Ngj-;aojg - NTRS - NASA

0 downloads 0 Views 11MB Size Report
R=19850021724 2018-11-05T11:01:43+00:00Z .... manufacturers, either expressed or implied, by the National. Aeronautics and Space ..... The shipping dates were May,. August and ...... cracking to 31 +lPa (4.5 ksi), and full failure to 35 Wa (5.0 ksi). ..... SMC Composite Materials," Proceedings of the Sixth Conference.

NASA CONTRACTOR REPORT

177357

__

(

(NASA-CR-177357)

L C L Y f I E tliTEIX ANL GRAPBXTE E I B d R IrUIEiiFACE 2 3 L C 1 F i n a l B e p o r t , , ! ~ r .15364 Cec. 1 S E 4 1 Y y o m i n g Univ.) :? d : . + > ' p B C A ' l t i / I r " A3 1 CSCL

-

- ..

-1

Unclas

Ili)

G3/24

Polymer Matrix and Graphite Fiber Interface Study

D.F.Adams R. S. Z i m m e r m a n E .?,I. O d o m

June 1985

CONTRACT NASZ-116 1 2

IINFORMATION NATIONAL TECHNICAL I SERVICE REPRODUCED B Y

I

U.S. DEPARTMENT Of COMMERCE SPRINGFIELD V A . 22161

,

,

Ngj-;aojg :.

29E63

. ,

,

7 . ;

J

3. Rectp~enr's OJtalog No

2. Government Access~on No.

1 . Report No

NASA CR 177357 5 Report Dare

4 . T ~ t l eaad Subr~tle

June 1985

Polymer Matrix and Graphite Fiber Interface Study 7. Aurhor(5l

6 . Perform~ngOrgantzat~onCode

Donald F. Adams Richard S. Zimmerman Edwin M. Odom

8 Perform~ngOrgan~zar~on Report No

UWME-DR-501-102-1 10. Work Un11 NO

9. Perform~ngOrgan~zalionName and Address

Composite Materials Research Group University of Wyoming Laramie, Wyoming 82071

1 1 . Conrract or Grant NO.

NAS2-11612 13. Type of Report and Period Covered

i Z . S.mnsoring Agency Name 1:7d Idoress ,

NASA-Ames Research Center Moffett Field, California 94035

Final Re 0rt Aoril 19g3 - Der. 1984 14. Sponsor~ngAgency Code

505-33-31

15. Supplementar~ Notes

NASA-Ames Technical Contact: Demetrius A. Kourtides,Arnes Research Center, MS 234-1 (415) 094-6079, FTS 464-6079 16. Abstract

Hercules AS4 graphite fiber, unsized, or with EPON 528, PYA, or polysul£one sizing, was combined with three different polymer matrices. These included Hercules 3501-6 epoxy, Hercules 4001 bismaleimide, and Hexcel F155 rubber-toughened epoxy. Unidirectional composites in all twelve combinations were fabricated and tested in transverse tension and axial compfession. Quasiisotropic laminates were tested in axial tension and compression, flexure, interlaminar shear, and tensile impact. All tests were conducted at both room temperature, dry and elevated temperature, wet conditions. Single fiber pullout testing was also performed. Extensive scanning electron microphotographs of fracture surfaces are included, along with photographs of single fiber pullout failures. Analytical/ experimental correlations are presented, based on the results of a finite element micromechanics analysis. Correlations between matrix type, fiber sizing, hygrothermal environment, and loading mode are presented. Results indicate that the various composite properties were only moderately influenced by the fiber sizings utilized.

17. Key Words (Suggerted by A u t h o r l s l l

18. D ~ s l r ~ b u t i oStalemen1 n

Graphite/Polymer Composites Fiber-Matrix Interface Mechanical Properties Micromechanics Analyses Unclassified

Unclassified ' For

NASA.C-166 (Rev. 10-75)

sale by the

s

Subject Catagorg 24

20. Securilv Class~f.(of 1h1s pagel

19. Security Classil. (of this report)

,

Unclassified, Unlimited

N a l ~ o n a Technrcal l Information

2 1 . No. o f Pages

396 S e r v ~ c e S. p r i r i e l ~ e l d .V ~ r g ~ n i22161 a

22. Prlce'

,

PWFACE This technical report study of

the graphite

NASA-Ames

Research

presents the results of

fiber-polymer matrix

Center

under

a thirteen-nonth

interface, sponsored by

Research Contract No. NAS2-11612.

1Yr. D . A . K o u r t i d e s s e r v e d a s the NASA-Ames Project ~4onitor. All work was conducted by the Composite Materials Research Group (CMRG)

within

University

the

of

Department

Wyoming,

of

Mechanical

except

the

characterization, which was performed of Lansas City, Missouri.

F. Adams, Professor, Mr.

Edwin $1.

program

was

fiber

surface

and Mr. Richard

S. Zimmerman, Staff

by

Mr.

William

Morrison,

Gregory

i$errill

students in Mechanical

Composite Materials Research Group.

extended

to Dr. Norman

J. Johnston of

Engineer.

Zimmerman in June 1984. Making

this program were Messrs.

of the

treatment

was assigned to this

significant contributions to

Bauer, undergraduate

the

by fiidwest Research Institute

Engineer, initially

succeeded

Pressnall,

at

Co-Principal Investigators were Dr. Donald

Odom, Staff

but

Engineering

Mathew Graf,

Bishop, and Kenneth

Engineering and members Special appreciation is

NASA-Langley Research Center

for supplying the thermoplastic-sized graphite fibers for use in this study. Numerous the

material acquisition problems

first six months of

completing the work. 1984,

a full

All

eight months

this contract,

were encountered during

resulting in some delay in

materials were not received into the

program.

Once

until January materials were

received, good progress was made in the fabrication of composites and the testing of all samples. Use of

commercial products

or names

of manufacturers

in this

report does

not constitute official endorsement

manufacturers,

either

expressed

Aeronautics and Space Administration.

or

implied,

of such products o r

by

the

National

TABLS OF CONTENTS Section

Page

1

SUMCllARY . . . . . . . . . . . . . . . . . . . . .

1

2

INTRODUCTION

. . . . . . . . . . . . . . . . . .

19

3

EXPERMENTAL PROCEDURES . . . . . . . . . . . . .

21

3.1

TestMatrix . . . . . . . . . . . . . . .

21

3.2

Fiber Sizings . . . . . . . . . . . . . .

21

3.3

Preparation of Composite Materials

. . .

23

3.4

Composite Test Specimen Preparation . . .

28

3.5

Neat Resin Test Specimen Preparation

.

30

.

3.5.1

Tensile Test Specimens

. . . .

30

3.5.2

Iosipescu Shear Test Specimens .

30

3 . 5. . 3

Coefficient of Thermal Expansion Tests . . . . . . . .

31

Coefficient of Moisture Expansion Tests . . . . . . . .

31

Testing Equipment . . . . . . . . . . . .

34

3.5.4

3.6.1

Unidirectional Composite Transverse Tension . . . . . .

35

3.6.2

Laminate Axial Tension

. . . .

35

3.6.3

Unidirectional Composite Axial Compression . . . . . . .

35

3.6.4

Laminate Axial Compression

.

37

3.6.5

Laminate Flexure

. . . . . . .

37

3.6.6

Laminate Interlaminar Shear . .

37

3.6.7

Neat Resin Properties . . . . .

39

3.6.8

Single Fiber Pullout

39

.

. . . . .

TABLE OF CONTENTS (continued) Section

4

Page EXPERIpiENTAL RESULTS

. . . . . . . . . . . . . .

43

4.1

Fiber Surface Treatment Characteristics .

43

4.2

Neat Resin Properties . . . . . . . . . .

43

4.3

Composite Fiber Volume Contents . . . . .

48

4.4

Unidirectional Composites . . . . . . . .

51

4.6

4.4.1

Transverse Tension

. . . . . .

53

4.4.2

Axial Compression . . . . . . .

65

quasi-Isotropic Laminates . . . . . . . .

76

4.5.1

Axial Tension . . . . . . . . .

77

4.5.2

Axial Compression . . . . . . .

87

4.5.3

Flexure . . . . . . . . . . . .

99 .

4.5.4

Interlaminar Shear

4.5.5

Tensile Impact

Single Fiber Pullout

. . . . . . 109

. . . . . . . . 114

. . . . . . . . . . 127

SCANNING ELECTRON MICROSCOPE RESULTS

. . . . . . 141

. . . . . . . . . . . . . . 141

5.1

Introduction

5.2

Specimen Preparation

5.3

Explanation of SEM Photographs

. . . . . . . . . . 141

ANALYTICAL/EXPERIMELVTL CORRELATIONS

. . . . . 141 . . . . . . 195

6.1

Micromechanics Analysis . . . . . . . . . 195

6 . 2'

Constituent Properties

6.3

Analysis Procedure

6.4

AS4/3501-6 Correlations . . . . . . . . . 207

. . . . . . . . . 198

. . . . . . . . . . . 205

TABLE OF CONTENTS (Continued) Page

Section

6.5

6.6

6.7

. . 207

6.4.1

Thermal Residual Stress

6.4.2

Moisture-Induced Stresses . . . 212

6.4.3

Transverse Tensile Loading

.

.

.

..216

6.4.3.1

Room Temperature, Dry . . . . . . . . 216

6.4.3.2

Elevated Temperature, Wet (93OC, 1%M) . . . . . .

AS4/4001 Correlations . . . .

.

.

.

221

. . . . 226

6.5.1

Thermal Residual Stresses

.

.

. 226

6.5.2

Moisture-Induced Stresses

. .

. 227

6.5.3

Transverse Tensile Loading

. :

228

6.5.3.1

Room Temperature, Dry . . . . . . . . 228

6.5.3.2

Elevated Temperature, Wet . . . . 231

AS4/F155 Correlations . . .

.

.

. . . . . 235

6.6.1

Thermal Residual Stresses . . . 236

6.6.2

Moisture-Induced Stresses . . . 236

6.6.3

Transverse Tensile Loading

. . 237

6.6.3.1

Room Temperature, Dry . . . . . . . . 237

6.6.3.2

Elevated Temperature, Wet . . . . 241

Summary of Results

.

. . .

CONCLUSIONS AND RECOMMENDA'TIONS .

.

. . . . . . . 245 .

. . . . . . 247

TABLE OF COiqTENrS (Continued)

Sect ion References

Page . . . . . . . . . . . . . . . . . . . . . . . . . 251

Appendices Appendix A

-

Tables of Individual Specimen Test Results

Appendix B

-

Individual Data Plots . . . . . . . . . . . . 327

Appendix C

-

Appendix D

-

. 255

Additional Photographs of Single Fiber Pullout Specimen Fracture Surfaces . . . . . 369 Characterization of Graphite Fiber Surface Coatings . . . . . . . . . . . . . . . . . . 379

SECTION 1 SUMMARY Three polymer matrix materials and four fiber sizings, including an unsized graphite viz,

fiber, were

chosen by

fiber/polymer matrix

NASA-Ames for

interface

this Hercules

study.

AS4

A baseline epoxy,

Hercules 3501-6, plus Hercules 4001, a bismaleimide, and Hexcel

F155, a

rubber-toughened epoxy, were

selected as the

matrix materials.

Three common

828

polyvinylalcohol, and

epoxy,

PVA

thermoplastic, were

graphite fiber

used, along with

three polymer

sizings, i.e., EPON

Udel 'P1700 polysulfone

an unsized fiber,

total of twelve fiber sizinglmatrix combinations.

to create a

These sizings were

applied by Hercules, Inc. and NASA-Langley Research Center, to fibers supplied then sent using

from a

common batch.

Samples of

to Midwest Research Institute for surface characterization

infrared spectroscopy. These

are included here as Appendix D. fiber, in the all

test

these sized fibers were

sizing characterization results

Hercules AS4 high strength graphite

form of 12,000 filament tow, was

panels.

This

provided

a

common

used in fabricating fiber base

for this

interface study. All specimen

composite material fabrication, and

Composite Materials

prepregging,

test

mechanical testing

Research Group

(CrtRG)

panel fabrication,

was performed at

the

by the

University of

Wyoming. An extensive mechanical characterization study was completed on

the

12

fiber

surface

treatment/polymer matrix composites, at two

different environmental conditions, viz, room temperature, dry (RTD) and elevated

(ETW).

temperature, wet

Unidirectional,

i.e., [O] 8 ,

composites were tested under transverse tensile and axial compressive loadings, and axial

tensile, axial

(interlaminar) Single

shear

shear, and

also,

strengths.

mechanical

as

Neat

an

aid

tensile

impact

in the determination of interfacial was performed

Hercules 4001 and i.e.,

on two

Hexcel F155, to

tensile

and

two neat

of the

determine

shear strengths,

strains, for use as input to the finite element

computer program.

Coefficient of

thermal expansion

and coefficient of moisture expansion measurements were these

loadings.

all 12 fiberlmatrix

conducted on

resin testing

properties,

moduli, and ultimate micromechanics

instrumented

testing was

matrix materials, viz, their

[+45/0/90Is, laminates under

compressive, three-point flexure, short beam

fiber pullout

combinations

i.e.,

quasi-isotropic,

resin systems.

All of

also made on

the above data were already

available for the Hercules 3501-6 epoxy. Scanning unidirectional tensile

electron microscopy composite

was

fracture

performed

surfaces, for

and axial compressive loadings.

on both

all

of

the

transverse

An extensive collection of

SEM photographs is included in Section 5 of this report.

A summary of the mechanical Figures 1 through strength

test results is

8, in simple bar chart forms.

properties are summarized in

presented here in For brevity, only

these figures (except for the

laminated composite tensile impact testing, for which a energy

absorption plot

relevance).

is

included

total impact

instead, as being of greater

Complete results, including tables of numerical averages

AVERAOE TRANSVERSE TENSILE STRENGTHS

Figure 1

.

unidirectional composite Transverse Tensile Strengths of the Twelve Fiber Sizing/:$atrix Combinations.

AVERAOE AXIAL WMPRESSIVE STRENGTHS

Figure 2.

Unidirectional Composite Axial Compressive Strengths of the Twelve Fiber S i z i n g / ~ a t r i xCombinations.

AVERAGE LAMINATE TENSILE STRENGTHS

Figure 3.

Quasi-Isotropic Laminate Axial Tensile Strengths of the Twelve Fiber SizingIMatrix Combinations.

AVERAOE LAMINATE COMPRESSIVE STRENGTHS

Figure 4.

Quasi-Isotropic Laminate Axial Compressive Strengths of the Twelve Fiber SizingIMatrix Combinations.

AVERAGE LAMINATE FLEXURAL STRENGTHS

Figure 5.

Quasi-Isotropic Laminate Flexural Strengths of the Twelve Fiber Sizing/Matrix Combinations.

AVERAQE INTERLAMINAR SHEAR STRENGTHS

Figure 6.

Quasi-Isotropic Laminate Interlaminar Shear Strengths of the Twelve Fiber SizingIMatrix Combinations.

AVERAOE TENSILE IMPACT UUERQIES

Figure 7.

Quasi-Isotropic Laminate Tensile.Impact Energies of the Ten Fiber S i z i n g / ~ a t r i xCombinations Successfully Tested.

AVERAGE

Figure 8.

SINGLE FIBER PULLOUT STRENGTHS

Single Fiber Pullout Shear Strengths of the Seven Fiber S i z i n g / ~ a t r i xCombinations Successfully Tested.

and three-dimensional bar chart plots, Incldded

there

also

are

modulus

are presented in

and

strain

to

Section 4.

failure data as

appropriate. Figure 1

is a plot

of the unidirectional

composite transverse

tensile strengths of the 12 fiber sizing/matrix combinations, at both dry (RTD) and elevated

the room temperature,

temperature, wet (ETw)

test conditions.

The wet condition was an approximately

moisture

gain

weight

in

the

composite

in

one percent

all cases.' Since the

graphite fibers do not absorb this moisture, this one percent gain of

the composite corresponds

weight gain in actual

to two to

the matrix itself,

fiber volume

of

the

three percent moisture

the exact value

particular

weight

depending on the

composite.

Individual

composite fiber volumes and matrix neat (unreinforced) resin moisture saturation

levels

temperature was AS4/4001

are

tabulated

selected

composites, and

as

Section 4. The elevated test

in

93°C

(200°F)

38°C (100°F)

for the AS4/F155 composites.

The Hercules 3501-6 epoxy is a 177°C (350°F')

matrix, while Hexcel F155 temperature

Hexcel F155

rubber-toughened epoxy is a

matrix.

Thus,

all

120°C (250°F)

composites incorporating the

matrix were tested at the lower elevated temperature, to

ETW

permit

cure temperature matrix

and Hercules 4001 bismaleimide is a 204°C (400°F) postcure

material,

cure

for the AS413501-6 and

comparisons

on

a

somewhat

equivalent

basis

between

systems. As

indicated in Figure

1, the transverse

tensile strengths of

the AS413501-6 unidirectional composites, for all four fiber sizings, were

clearly

composites,

lower

than

particularly

the at

strengths the

RTD

of

the

other two matrix

test condition.

This is not

surprising in

that the Hercules 3501-6 is a relatively low strain to

failure epoxy, and

thus so is the composite.

That the fiber sizing

poorest interface bond, viz, the PVA sizing,

expected to provide the

resulted in the highest composite transverse tensile strength is also not

totally

unexpected.

fiber-matrix

debonding

stress concentrations stress relief.

The

slightly

(microcracking) in this

,These aspects

poorer in

bond

local

brittle matrix,

allows local

regions

of high

thus providing

are discussed in detail in

some

Section 6,

in relation to the experimental/analytical correlation micromechanics results.

The transverse

composite systems also different

fiber

tensile strength results for

the other two

indicate significant differences

sizings.

In

particular,

the

between the

polysulfone sizing

produced high RTD strength

values, and the PVA sizing

as

condition, however, the polysulfone-sized

expected.

At

the ETW

lower values,

AS4/4001'composite strength was not retained. Figure compressive

2

is

a

strength

plot

those

of

the

greater detail in

the

averages.

compressive strengths of than

of

unidirectional

At

room

a

other

two

fiber-dominated property, in a lower

laterally

microbuckling, a

supports

lower modulus

lower composite axial maintained

at

the

clearly lower

a

a combination of lower

Axial compressive strength lower

fiber volume would be

composite strength. Also, the

individual

matrix can

compressive strength.

ETW

axial

composite systems. As discussed in

Section 4 , this was due to

expected to result matrix

temperature, the

the AS4/~155composites were

fiber volumes and a lower matrix modulus. being

composite axial

condition.

It

since the

fibers

be expected These same

against

to lead

to

trends were

will be noted in Figure 2,

however, that there was no clear influence of fiber sizing.

That is,

axial compression of a unidirectional composite does not appear to be a good discriminator of fiber-matrix interface bond strength. Axial

tensile

summarized in although it

strengths

Figure 3.

strengths.

the quasi-isotropic laminates are

There was

no clear

will be noted that the

significantly higher at the Likewise,

of

the AS4/3501-6

AS4/4001 strengths were actually

ETW condition than at composites at

The strengths of the

lower, however.

trend in the results,

room temperature.

least maintained

their RTD

AS4/F155 composites did tend to

These trends are

associated with the

be

reduction of

the curing residual stresses at the higher temperatures combined with the

generally beneficial effects of

the cooldown-induced

moisture swelling in offsetting

thermal'contraction stresses, as

discussed in

Section 6. The quasi-isotropic laminate axial compressive strengths plotted in Figure

4 tended to

follow the same

trends as the unidirectional

composite axial

compressive strengths

(Figure 2).

there

strong

fiber

was

no

composites were both

test

influence

clearly stronger

conditions.

laminates were similar.

The

of

than the

composite

compression,

sizing,

the

AS4/4001

AS4/3501-6 composites at

fiber volumes

of

these.two types of

On the other hand, the fiber volumes of

AS4/F155 laminates were lower, accounting these

That is, while

systems.

As

for

the

for the lower strengths of

unidirectional

composite axial

laminate axial compression is not a sensitive indicator

of interface bond strength. Quasi-isotropic plotted in

Figure 5.

laminate, three-point As expected,

flexural

the trends

strengths are

follow those of the

axial

compression

strengths

(~igure 4).

tests

of graphite/epoxy

in

a

flexural

laminate

composites tend

axial compressive strengths (for Thus,

The

test,

to be

axial tensile

higher than the and 4 ) .

example, compare Figures 3

the

laminate

tends

to

fail

on the

compression side, i.e., the compressive strength dictates failure. No

unidirectional

his

NASA-Ames.

test

indicator of interface quasi-isotropic expected

to

be

as

beam shear

AS41F155 presumably moisture. matrix

called

a

were

specified

relatively

as

a

that it would

While

the not

unidirectional

be adequate.

are summarized

by

sensitive

shear tests of

for, however.

indicator

strength results there was not

tests

Short beam

it was hoped

The

in Figure 6. At

a strong influence of fiber sizing. sizings performed

well, but were not

As might be expected, the high strain-to-failure Hexcel

F155 rubber-toughened strengths.

been

sensitive an

EPON 828 and polysulfone

exceptional.

have

laminates were

room temperature The

might

shear

performance.

composite shear test, short

composite

epoxy produced the

highest interlaminar shear

However, at the ETW condition, the unsized and laminate was

shear

due

to

strengths were interface

severely

PVA-sized

degraded.

rhis

bond degradation by the absorbed

On the other hand, the other two, higher cure temperature,

materials

exhibited

shear

strength

reductions uniformly,

somewhat independent of fiber sizing. As discussed in Section 4 , the quasi-isotropic laminate

tensile

impact tests were only successful for some of the fiber sizinglmatrix combinations.

Specifically,

delaminate, resulting

in

the

AS4/4001

laminates

questionable results.

tended

to

Thus, the tensile

impact total energy absorption plots of Figure 7 do not include these -14-

d a t a , except

f o r t h e RTD t e s t s of t h e EPOA 828 and p o l y s u l f o n e - s i z e d

AS414001 l a m i n a t e s . tensile

impact

Like

tests

did

different fiber sizings. well as

t h e AS4/3501-6

lower f i b e r volumes, i n f l u e n c e of mechanism.

t e s t s (Figure 3 1 ,

the s t a t i c t e n s i l e not

indicate

strong

the

i n f l u e n c e s of t h e

The AS41F155 l a m i n a t e s d i d perform about a s laminates a t

room t e m p e r a t u r e ,

presumably b e c a u s e of t h e

high m a t r i x s t r a i n

i n s p i t e of

o f f s e t t i n g favorable

to failure as

an e n e r g y a b s o r p t i o n

The impact e n e r g y a ~ s o r p t i o n s of t h e 120°C (250°F) c u r e

t e m p e r a t u r e Hexcel

F155 m a t r i x l a m i n a t e s tended

t o i n c r e a s e more a t

t h e ETW t e s t c o n d i t i o n s t h a n d i d t h e h i g h e r c u r e t e m p e r a t u r e H e r c u l e s 3501-6

epoxy

sensitivity

matrix laminates.

This r e f l e c t s

the greater moisture

F155 epoxy m a t r i x .

of t h e Hexcel

( I t w i l l be r e c a l l e d

t h a t t h e t e s t t e m p e r a t u r e used was l o w e r , t o compensate f o r t h e lower cure

temperature,

but

the

amounts

of

absorbed m o i s t u r e were t h e

same.) C o n s i d e r i n g t h e g r e a t e r c o m p l e x i t y of t h e

t e n s i l e impact t e s t

method r e l a t i v e t o t h e s i m p l e s t a t i c s h o r t beam s h e a r t e s t , i t i s n o t an a t t r a c t i v e s c r e e n i n g t e s t . Single f i b e r pullout t e s t discussed i n successfully.

Section 4 ,

. cause the f i b e r s t o .

828-sized

f i l m s could

interface

higher

than

unidirectional

and

strengths produced

produced by

the

quasi-isotropic

previous seven f i g u r e s

do n o t seem

by

other laminate

As

were n o t t e s t e d

made t h i n

p u l l out r a t h e r than f a i l i n

bond those

fibers

n o t be

828 r e s u l t s a r e p r e s e n t e d i n F i g u r e 8 .

EPON the

t h e EPON

The m a t r i x

8.

r e s u l t s a r e plotted i n Figure

tension.

enough t o Thus, no

The i m p l i c a t i o n i s t h a t t h i s f i b e r s i z i n g were three.

Of c o u r s e t h e

data presented i n the

t o support t h i s

conclusion.

w i l l a l s o be n o t e d i n F i g u r e 8 t h a t o n l y t h e p o l y s u l f o n e - s i z e d

It

fibers

were s u c c e s s f u l l y

pulled out

highest

Hexcel F155

matrix.

For

the

materials, the polysulfone-sized f i b e r s resulted i n

o t h e r two m a t r i x the

of t h e

pullout

shear

strengths.

e x p e c t e d t h a t t h i s s i z i n g would

Thus,

it

would have been

have been t h e most d i f f i c u l t t o work

w i t h , r a l h e r t h a n be t h e o n l y one s u c c e s s f u l l y u t i l i z e d . As

w i l l be

noted i n

in

cases

strengths

all

unidirectional

Figure 8 , were

the calculated interface shear

relatively

composite s h e a r s t r e n g t h s .

other investigators as well, as

low

compared t o t y p i c a l

T h i s h a s been o b s e r v e d by

discussed i n S e c t i o n 4.6 i n

detail.

That i s , while t h e s i n g l e f i b e r p u l l o u t t e s t i s i n t e r e s t i n g , i t not

adequately

composite.

simulate

an

actual

multifiber,

S t r e s s c o n c e n t r a t i o n s induced where

does

h i g h f i b e r volume the f i b e r e x i t s the

m a t r i x f i l m a t e a c h s u r f a c e u n d o u b t e d l y r e d u c e t h e p u l l o u t f o r c e , and hence,

the

calculated

shear

strength.

Thus,

considering

the

d i f f i c u l t i e s involved i n performing t h e s i n g l e f i b e r p u l l o u t t e s t , it i s concluded

that it i s

not a p r a c t i c a l

i n t e r f a c i a l bond s c r e e n i n g

test. Ln

addition

to

mechanical p r o p e r t i e s uniaxial

tensile,

expansion t e s t s

materials. for

and

laminated

composite

t e s t s summarized i n F i g u r e s 1 t h r o u g h 8 above,

Iosipescu

and

Test r e s u l t s

the Hercules

unidirectional

shear,

were performed

bismaleimide

4001

the

Hexcel

t h e r m a l e x p a n s i o n and m o i s t u r e

on t h e

F155

neat (unreinforced) Hercules rubber-toughened

were a l r e a d y a v a i l a b l e

3501-6 epoxy,

these data

epoxy m a t r i x

from a p r i o r

being included

study here i n

S e c t i o n 4 . 2 a l s o , f o r completeness. These n e a t finite

element

r e s i n m a t r i x p r o p e r t i e s were needed micromechanics

analysis

utilized

as input t o the i n Section 6, i n

making predictions on

of the influence of matrix

unidirectional composite

analytical predictions

transverse

were then

type and fiber sizing

tensile properties.

correlated with

These

the corresponding

experimental data generated here. The

correlations

presented

in

Section 6

indicate

that the

University of Wyoming's WY02D finite element micromechanics

analysis

is

fully

capable of

predicting unidirectional composite response,

including the influence of a degraded interface.

Thus, it

is likely

to

become an extremely valuable tool in future experimental studies,

in

identifying

the

proper

tests,

and

testing

conditions, to be

present study has provided a

large quantity of

utilized. In summary, the experimental data, One

group

prepreg, conducted

of

generated under carefully

experienced

fabricated

the

researchers made

composites

and

this

all

of

the required

the neat resin specimens,

all of the testing, did the scanning electron microscopy,

and performed the finite element analyses. in

controlled conditions.

report

are

believed

to

be

Thus, the data accurate

Experimental procedures and interpretations of results in detail in the following sections.

and

presented reliable.

are presented

SECTION 2

INTRODUCTION

The

influence

performance of

for

mechanical

the

fiber-matrix

the composite

ater rials

Composite Wyoming

of

has been

Research

some

time.

properties

of

a topic

Group

Thermal

interface

(CMRG) and

bond

on

of research

at

the

moisture

composite material

the

by the

University of

effects

on

the

also

been

of

have

foremost interest in the numerous prior programs undertaken involving graphite fibers and a variety of polymer matrix systems. Initially, a graphite

program

the twelve

NASA-Langley

within

Research

general

aerospace

filament tow

form was

EPON 828 epoxy

program, thus maintaining

polymer matrices

Center

with

and fiber

the

Hercules AS4 ,high strength its

the

matrices and a

treatments.

fiber [2] was obtained from Hercules Aerospace

Hercules AS4 graphite

of

polymer

surface treatments was proposed

was added to the

combinations of

treatments.

four

Due to the unavailability of PEEK thermoplastic [ l ] , a

fourth surface treatment

because

study

fiber with three different

to NASA-Ames.

and

to

availability

industry.

acquired with

graphite fiber

and

The

four required surface was chosen

extensive current usage

Hercules AS4 fiber in 12,000 three different

[ 3 ] , polyvinylalcohol (PVA), Ultem

sizings, viz,

P1700 polysulfone

[4], and'unsized. Three polymer resins were acquired, viz, Hercules 3501-6, a material,

standard Hercules

epoxy 4001,

----

matrix a

151

selected

bismaleirni.de

[6],

--

Preceding Page Blank

E'L:APtTTS - 2::.'

? ;-

-

..-.. 7 3

- - -. ..

.,

Z'"'

.. .;

-2

as

the

baseline

and Hexcel F155, a

rubber-toughened epoxy 1 7 1 . The

twelve

combinations

were

prepregged, and fabricated into

unidirectional

and quasi-isotropic plates,

manufacturer's

specifications.

plates for mechanical of

performance

Hercules AS4

Specimens

being cured according to were machined

property measurements, to

between

the .four fiber

from these

provide comparisons

surface treatments of the

graphite fiber when combined

with each

of the

three

polymer matrices. performed at two conditions, viz, room temperature,

Testing was dry,

(RTD), and elevated temperature, wet, (ETW), wet defining a one

percent

moisture

transverse

tension

composites, axial shear,

and

weight and

gain

condition.

axial

compression

of

tension, axial compression,

tensile

impact

of

single fiber pullout testing. a

Tests performed included

scanning electron

the

the

unidirectional

flexure, interlaminar

quasi-isotropic laminates, and

Fracture surfaces were examined

microscope ( S E d )

to evaluate

using

the fiber-matrix

interface. The

Composite

micromechanics

Materials

analysis

and

Research associated

Group's

finite

element

WY02D computer program was

used to predict unidirectional composite properties, and to infer the interface

strengths

treatments combined

resulting

from

with the various

the

different

fiber

matrix materials.

surface

Conclusions

were thus arrived at as' to the most efficient method of fiber surface treatment associated with the three different types of resin systems.

SECTION 3

EXPERIMENTAL PROCEDURES 3.1

Test Matrix A

comprehensive series of

tests was completed

for each of the

twelve fiberlmatrix combinations and three neat resin system's. Table 1 indicates

the specific

tests performed,

and the

test conditions

utilized. The dry test specimens were to

insure

that

they

remained

conditioned (wet) specimens were closed

glass

containers

percent

of

dry

after

74OC

at

chamber until

moisture

fabrication.

Moisture-

suspended above distilled water

maintained

Benchmaster environmental weight

stored in dessicators until tested,

desired.

(165OF)

they had This

in a Tenney

absorbed the

elevated

in

one

temperature

allowed the test specimens to

reach the desired moisture level

more

rapidly

been

room

than

temperature. determine

if

they

Witness the

had

exposed

specimens were

level

of

moisture

to moisture

weighed absorption.

at

periodically

to

Specimens were

conditioned to one percent moisture weight gain prior to testing. 3.2

Fiber Sizings All of

the AS4 graphite

Magna, Utah, in the form unsized fiber, fiber sized

with

fiber was supplied

by Hercules, Inc.,

of 12,000 fiber tow 121.

Hercules provided

sized with Shell EPON 828

polyvinylalcohol

(PVA).

August and December 1983, respectively.

The

epoxy [ 3 ] , and fiber

shipping dates were May,

Table 1 Test Matrix for Each FiberIMatrix Combination

Loading Mode

Number of Specimens Room Temperature, Elevated Temperature, Wet (ETW) Dry (RTD)

Quasi-Isotropic Laminate Tests Tension Compression Flexure Interlaminar Shear Instrumented Tensile Impact

5 5 5 5 5

Fiber-Matrix Interface Tests Transverse Tension Axial Compression Single Fiber Pullout

10 10 10

Neat Resin Tests Uniaxial Tension Iosipescu Shear Thermal Expansion Moisture Expansion Subtotals

5

5 3

3 71

Total Specimens/Combination

68 139

Total specimens for 12 fiberlmatrix combinations and neat 3 resin systems; less neat resin tests for Hercules 3501-6 (data already available): 1378

One

pound

NASA-Langley sizing [4].

of

the

unsized

t o receive

AS4

a General

The s o l v e n t

used was m e t h y l e n e c h l o r i d e .

weight of t h e w e i g h t of

d a t e from NASA-Langley A l l work

fiber

was

sent to

E l e c t r i c UDEL P-1700 p o l y s u l f o n e

r e s i d u a l s i z i n g a f t e r s o l v e n t removal by

graphite

The amount of

was a p p r o x i m a t e l y 0.37 p e r c e n t

the graphite f i b e r i t s e l f .

The s h i p p i n g

was December 1983.

a s p a r t of

the present study,

and r e p o r t e d h e r e , was

performed u s i n g t h e s e same b a t c h e s of f i b e r s . 3.3

P r e p a r a t i o n of Composite M a t e r i a l s A l l twelve

of

four

resins

c o m b i n a t i o n s o f H e r c u l e s AS4 g r a p h i t e f i b e r w i t h one

different

treatments

were p r e p r e g g e d u s i n g

batch prepregger was

surface

used t o

graphite

one of two

p r e v i o u s l y developed

prepare s u f f i c i e n t

s p o o l i n t h e lower

b a t h on

up t o

U n i v e r s i t y of Wyoming the four

H e r c u l e s AS4

matrix composite combinations.

F i g u r e 9 i s a p h o t o g r a p h of t h i s p r e p r e g u n i t ,

good q u a l i t y p r e p r e g .

rollers,

a t the

A drum winder

p r i o r programs a t Wyoming t o produce

T h i s t e c h n i q u e had been used i n

heated r e s i n

three different matrix

techniques.

prepreg f o r

f i b e r / H e r c u l e s 3501-6 epoxy

showing t h e f i b e r

and

the front.

the heated

r e a r of t h e a p p a r a t u s

The f i b e r

resin bath.

p a s s e s around

and t h e various

I n t e r n a l wipers d i r e c t t h e

f i b e r down i n t o t h e r e s i n , which i s t y p i c a l l y h e a t e d t o a p p r o x i m a t e l y 120°C

(250°F),

Between t h e through

where

r e s i n bath

a sequence

excess r e s i n .

the

fiber

and t h e

of w i p e r s

The drum

tow becomes s a t u r a t e d w i t h r e s i n . drum, t h e

t o spread

impregnated f i b e r p a s s e s out the

tow and

wipe o f f

speed and r e s i n b a t h t r a n s v e r s e s p e e d c a n be

i n d i v i d u a l l y a d j u s t e d t o a c c u r a t e l y a l i g n t h e f i b e r tows i n a u n i f o r m p a t t e r n a c r o s s t h e r e l e a s e paper taped

t o t h e drum.

Once a c o m p l e t e

Figure 9.

Drum W i n d e r P r e p r e g U n i t U s e d .

w i d t h of

p r e p r e g i s wound, a second s h e e t of r e l e a s e p a p e r i s p l a c e d

o v e r t h e p r e p r e g and t h e p r e p r e g i s rem,oved from t h e drum, by c u t t i n g across i t i n a

g r o o v e i n t h e drum.

Laid o u t f l a t , t h i s

produces a

p i e c e of p r e p r e g a b o u t 1'80 cm (70 i n ) l o n g , and of t h e d e s i r e d w i d t h . For t h e

present study,

36 cm

prepreg

was

into

then

cut

(14 i n ) uniform

30.5

s t a c k e d u p , and p l a c e d i n m o i s t u r e - p r o o f a

freezer.

The

bags

prevented

wide p r e p r e g

was made. T h i s

cm ( 1 2 i n ) l o n g p i e c e s ,

p l a s t i c bags

moisture

for storage i n

accumulation

while the

p r e p r e g was b e i n g s t o r e d i n t h e f r e e z e r . The H e r c u l e s 4001 and Hexcel F155 r e s i n s were p r e p r e g g e d u s i n g a technique viscous

d e v e l o p e d a s p a r t of t h e p r e s e n t s t u d y f o r u s e w i t h h i g h l y

A

resins.

p r e p r e g g e r shown (solid)

i n Figure

r e s i n on

drawn t h r o u g h

thin film

t o p of

a flat

10.

A

was produced u s i n g t h e f i l m

heated p l a t e

the release

m e l t s t h e hot-melt

p a p e r , and

d i e arrangement,

r e s i n on t h e r e l e a s e p a p e r . were h e a t e d t o

of r e s i n

then the paper i s

leaving a

uniform l a y e r

The H e r c u l e s 4001 and Hexcel El55 r e s i n s

o n l y 75OC (167OF)

i n t h i s process,

t o minimize c u r e

a d v a n c e and t o m a i n t a i n a c o n s i s t e n t v i s c o s i t y f o r t h e Sufficient resin around

f i l m was

t h e drum of t h e drum

Figure 9 .

This r e s i n

drawn t o

allow being

winding was t h e n This

f i l m backed

with r e l e a s e

film in

a manner

similar to

process.

A second

l a y e r of f i l m

placed over t h e f i b e r

p r e p r e g was

f i l m forming.

wrapped c o m p l e t e l y

w i n d e r p r e p r e g u n i t p r e v i o u s l y shown i n

t a p e d t o t h e drum, and t h e n t h e d r y AS4 g r a p h i t e onto the

of

removed from

t h a t used

p a p e r was s e c u r e l y f i b e r tow was wound i n t h e normal wet

backed w i t h r e l e a s e p a p e r

and r e s i n f i l m a l r e a d y t h e drum,

on t h e drum.

c u t i n t o uniform l e n g t h s ,

s t a c k e d , p l a c e d i n p l a s t i c b a g s , and s t o r e d i n a f r e e z e r .

As f o r t h e

Figure 10.

F i l m P r e p r e g g e r Unit Used.

Hercules 3501-6 matrix, 36 cm (14 in) wide prepreg was made. Once enough prepreg This

minimized

storage

unidirectional,

[O] 8 ,

was made to lay up a time and

for

the

plate, this was done.

prepreg.

Both

eight-ply

eight-ply quasi-isotropic, [+45/0/90Is,

plates

were laid up for this

program.

The Hercules 3501-6 and 4001

matrix

composite plates were

fabricated and cured

into 30.5 cm (12

in) long by 30.5 cm (12 in) wide plates.

The Hexcel F155 plates were

also 30.5 cm (12 in) long, but only 15.2

cm (6 in) wide.

P155

matrix

platen

size

3501-6

and

press.

All

composite of

the

heated

4001 matrix three

plates

were platen

made smaller to accomodate the cure press used.

composite plates

types

of

The Hexcel

The Hercules

were cured in a blanket

composites were

cured

using

manufacturer's recommended cure schedules as given below: Hercules 3501-6 Cure Schedule 23°C to 150°C heatup at 3"~/min,at 20 psi pressure 150°C to 177°C heatup at 3"c/min, at 90 psi pressure Hold for 3 hours at 177°C Post-cure in an air circulating oven for 4 hours at 177°C Hercules 4001 Cure Schedule 23°C to 150°C heatup at 3"c/min, at 20 psi pressure 150°C to 177°C heatup at 3"C/min, at 90 psi pressure Hold for 3 hours at 177°C Post-cure in an air circulating oven for 4 hours at 177"C, followed by 8 hours at 204OC Hexcel El55 Cure Schedule Heat in full vacuum to 85°C Hold for 4 hours at 85°C

the

Heat to 121°C at 20 psi pressure Hold for 3 hours at 121°C The

12,000 filament fiber

tows used in

well in the prepregging process. tendency

to

stick

together

this program handled fairly

The polysulfone-coated fibers had a

and

did

not

spread as evenly in the

wet-wind and film-wind processes as the other

three types of surface

treated fiber tows.

The unsized fiber tows produced

of fuzz balls during

the wet-wind and film-wind processes,

be

expected.

The

handled, and

produced

technique used technique

uniform

best

PVA

treated

quality

fibers were easily

prepreg.

The

wet-wind

Hexcel F155 and

Hercules 4001 resins, were

the quality of

the prepreg produced, with

in terms of

t'o clean

impregnated

and

as might

with the Hercules 3501-6 epoxy, and the film/dry wind

filmldry wind

easier

828 the

used with the

judged equal the

EPON

a large volume

process up

this

the fiber

being

apparatus

tows with

distribution of

easier

fibers

to perform.

afterward.

Both

It was also techniques

sufficient resin, and allowed the across

the

release paper,

this

producing uniform thickness prepregs. 3.4

Composite Test Specimen Preparation All

using

composite test

specimens were

diamond abrasive tooling.

overheating of the

machined from

Water cooling was

cured plates

used to prevent

composites during these operations.

A converted

machinist's surface grinder was used to machine most of the specimens to

final dimensions.

Tensile specimens

were machined into dogbone

shapes using a Tensilkut router. All finished specimens were clearly marked and stored in plastic bags until used.

The specimens designated for the hot, wet testing were suspended over distilled water

in containers kept in a temperature chamber and

maintained

at

(165°F').

weighed to

record the percent

74OC

various

composite

percent

was

systems.

measured,

Witness

specimens were periodically

weight gain being After

these

a moisture

specimens

temperature chamber, but left in

experienced by the weight gain of one

were

removed

from

the

the moisture chambers, until just

prior to testing. The

unidirectional composite transverse

tensile specimens were

nominally 15 cm (6 in) long and 2.5 cm (1 in)

wide.

Quasi-isotropic

laminate tensile specimens were 15 cm (6 in) long by 1.3 cm wide.

Unidirectional and

specimens were

10 cm (4 in) long by

flexural specimens were Short

laminated

7.6 cm (3

composite

compression

1.3 cm (0.5 in) wide. in) long by

beam (interlaminar) shear specimens were

by 1.3 cm (0.5 in) wide.

axial

Instrumented

(0.5 in)

2.5 cm (1

Laminate in) wide.

1.5 cm (0.6 in) long

tensile impact specimens were

18 cm (7 in) long by 1.3 cm (0.5 in) wide. Only testing.

the

tensile

impact

~lass/epoxy tabs, 5.1

these specimens using

specimens cm ( 2

a Techkits A-12

required tabbing prior to

in) long, were bonded

onto

two-part epoxy adhesive

[8].

This tabbing adhesive has been used at the University of Wyoming a number of years, with

excellent results.

for

Single-axis strain gages

were bonded onto one surface of the tensile impact specimens (using a standard

strain gage

adhesive),

to

allow

for

dynamic

strain

measurement. Strain gage extensometers compression specimens

to

were used on

measure

strains.

the static tension

and

3.5

Neat Resin Test Specimen Preparation Unreinforced

(neat) resin

F155 rubber-toughened determine element

the

testing was

epoxy and

matrix

the Hercules

properties

micromechanics

required

computer

program.

were

measured

for

these

4001 bismaleimide, to as

input to the finite

Uniaxial

Iosipescu shear properties as a function of content

performed on the Hexcel

tensile

and

temperature and moisture

two resin systems.

The Hercules

3501-6 matrix material properties did not have to be measured in this program since they had been evaluated in previous programs [9,10]. 3.5.1

Tensile Test Specimens Both

the

fabricated

Hexcel

into

F155

tensile

procedures developed

and

Hercules

test

4001

resin systems were

specimens using the well documented for NASA-Langley [11,12]

during prior programs

and the Naval Air Development Center [13]. Tensile

specimens were 15.2 cm (6.0

wide, and 0.25 cm (0.1 to

machine

required

the

the

rectangular

A Tensilkut router tool

resin pieces

for tensile testing.

and 0.51 cm (0.2 program.

in) thick.

in) long, 1.27 cm (0.5 in)

into

A gage section

in) wide was used

was used

the dogbone shape

7.6 cm (3.0 in) long

for all tension testing

in this

Two extensometers were attached to each specimen, to permit

measurement

of

both

axial

and transverse strains during each

tensile test. 3.5.2

Iosipescu Shear Test Specimens Iosipescu shear test

cm (0.5

in) wide by 0.25 cm (0.1

was machined grinding

specimens were 7.6 cm (3.0 in) long by 1.3 in) thick.

into both edges of the

wheel.

The standard 90' notch

test specimen using an abrasive

+45 degree strain A dual-element -

gage rosette was

then bonded

to

one

measurement of shear previously

in

a

surface strain.

large

of

specimen to

allow for the

The Iosipescu shear test had been used

number

excellent results [14-171.

each

It is

of

test

programs at Wyoming, with

presently also being considered by

Committee D-30 of ASTM for inclusion as an ASTM Standard Test Method. 3.5.3

Coefficient of Thermal Expansion Tests Coefficient of thermal expansion (CTE) testing was performed

the

Hercules

4001

and

Hexcel

F155

neat resins using a computer-

controlled quartz tube dilatometer test apparatus [18,19]. is

a

photograph

specimens

were

temperature

the

test

tested, each

set up.

Figure 11

Typically, three identical

specimen being

excursions from -40°C

Hercules 3501-6 neat resin.

of

on

subjected

(-40°F) to 120°C

to

three

(250"~)for the

and 4001, and up to 66OC (150°F) for the Hexcel F155

The heating rate was 1.7OCImin (3"FImin).

The specimens

were 12.7 cm (5.0 in) long, 0.95 cm (0.38 in) wide, and 0.25 cm (0.10 in) thick. 3.5.4

Coefficient of Moisture Ex~ansionTests Coefficients of moisture

expansion (CME) were measured

for the

Hercules 4001 and Hexcel F155 neat resins using a special quartz tube dilatometer test apparatus previously developed Wyoming

[18,19].

Figure 12

at the University of of the CME test setup.

is a photograph

Two very thin, i.e., 0.90 mm (0.035 in) thick, 70 mm (2.75 in) square plates

of

the material

to

be

tested

temperature/hurnidity chamber

maintained

percent

One

relative

humidity.

electronic analytical balance placed in a

were at

placed 66OC

specimen was

in

(150°F)

suspended

a closed and

98

from an

while the other identical specimen was

quartz tube dilatometer apparatus.

The 'weight gain due

Figure 1 1 .

Coefficient o f Thermal Expansion Apparatus.

Figure 12.

Coefficient of Hoisture E x p a n s i o n Apparatus.

to moisture

absorption and the corresponding

concurrently

for

the

two

specimens,

'computer program to calculate

expansion are recorded

and input to the equipment's

the coefficient of moisture

expansion

(CME) directly. Typically, three pairs of specimens of each material were tested to

obtain an

average value.

diffusion even at 66'C

Because of

the slow rate of moisture required 7 to 10 days

(150°F), a typical test

to complete. 3.6

Testing Equipment All

static testing

was performed

using an

electromechanical test machine coupled 21MX-E

minicomputer

reduced on

for

control

the Hewlett-Packard

Instron Model 1125

to a Hewlett-Packard Model HP

and

data acquisition.

21MX-E computer

and then

Data were read to a

data tape for later transfer to the University of Wyoming's CDC CYBER 760 mainframe computer. accomplished average

on

test

the

All plotting and further

CYBER

760

was

done

results

Engineering's PRIdE 550 7550 digital plotter. of

information, but

computer. on

the

data reduction was

Additional plotting of

Department

of hlechanical

computer, coupled to a Hewlett-Packard Nodel

Data

handling involved very large

this was

managed relatively

quantities

efficiently using

magnetic tapes for data transfer. Tensile Model

SI-1D

impact

testing

pendulum-type

was

performed

impact

testing

special wedge-type tensile grips and tensile impact bonded to load

ring

specimens [20,21].

used

to

measure

machine

incorporating

a load cell to accommodate A single-element

each test specimen to monitor was

using a modified Satec

load.

the

strain gage was

strain, and a piezoelectric Data were acquired using a

Nicolet

Explorer

transferred

Hodel

I11

to the

206-2

digital

oscilloscope, and then

HP 21-PIX-E minicomputer for subsequent reduction

and plotting. A Bemco

1125

Model

testing.

FTU 3.8 environmental testing

machine

A hot air

to

chamber was used

perform

gun and thermocouple

the

in the Instron

elevated temperature

arrangement was used with

the Satec impact testing machine to perform the

elevated temperature

instrumented impact testing. 3.6.1

Unidirectional Composite Transverse Tension Transverse tension testing was performed using an Instron strain

gage

extensometer

Complete

to

measure

stress-strain

curves

axial were

strain

for

recorded

each

specimen.

for each test, which

allowed for the calculation of Young's modulus, E, ultimate strength, 0

u'

and ultimate strain, EU.

3.6.2

Laminate Axial Tension Quasi-isotropic, i.e.,

axial tension using measure

[+45/0/90]

a strain gage

axial strain

and thus

,,

specimens were tested in

extensometer on each

permit the

specimen to

calculation of composite

modulus, and the recording of a complete stress-strain curve for each specimen . 3.6.3

Unidirectional Composite Axial Compression An end-loaded, side-supported test fixture (shown in

was used

for all

axial compression

testing.

This

Figure 13)

test method had

been used in several previous testing programs [22,23] producing very consistent results.

Two sets of steel blocks clamp on each end of a

flat rectangular specimen, providing rigid support at each end. polished steel guide rods maintain alignment of the two fixture

Two

Figure 13.

.

End Loaded, Side Supported Compression Test Fixture.

halves.

An extensometer is attached in the short gage section of the

specimen to measure

strain.

between two flat platens, of the

The specimen

Failure

failure at the

almost

compression

with the steel fixture taking the majority

direct loading, transferring

length.

is loaded in

always

it into the

occurs

in

specimen ends (crushing or

specimen along its

the gage section, with

brooming), occurring very

infrequently. 3.6.4

Laminate Axial Compression laminates, i.e., [+45/0/90]

Quasi-isotropic

,

were also tested

in axial compression, using the same end-loaded, side-supported test configuration used in the axial compressive testing of unidirectional composites, as described in Section 3.6.3. 3.6.5

Laminate Flexure Quasi-isotropic

flexure

laminates,

to determine the

i.e.,

[+45/0/90Is , were tested in

flexure strength and

modulus.

A standard

three-point bend flexure setup shown in Figure 14 was used for all of the flexural testing. in)

long, and

Crosshead

Test specimens 25 mm (1.0 in) wide, 76 mm (3.0 (0.09 in)

2.3 mm

movement

was

thick were

monitored

to

used for this testing.

allow the calculation of the

flexural moduli. 3.6.6

Laminate Interlaminar Shear Quasi-isotropic

determine their interlaminar STD

D2344-76.

i.e.,

laminates,

Test specimens

, were

tested to

shear strength, following AS'TM Standard

15 mm (0.6

wide, and

2.3 mm (0.09 in) thick were

testing.

Load was

monitored for

calculation of shear strength.

[+45/0/90Is -

in) long, 13 mm (0.5 in)

used for all short beam shear

each test

specimen, allowing the

F i g u r e 14.

Three-Point

Loading F l e x u r e F i x t u r e .

3.6.7

Neat R e s i n P r o p e r t i e s

Neat r e s i n specimens of t h e Hexcel F155 and H e r c u l e s 4001 m a t r i x m a t e r i a l s y s t e m s were f a b r i c a t e d used

in

many

previous

u s i n g t h e same t y p e s of s t e e l molds

programs

at

Wyoming

[ll-13,18,19].

Both

u n i a x i a l t e n s i l e and I o s i p e s c u s h e a r specimens were f a b r i c a t e d t o c h a r a c t e r i z e t h e s e two r e s i n s .

The H e r c u l e s 3501-6 epoxy had a l r e a d y

b e e n c h a r a c t e r i z e d i n p r e v i o u s programs [ 9 , 1 0 ] and t h u s was n o t t e s t e d i n t h i s program. 3.6.8 Single

fiber

interfacial different fibers,

bond

pullout between

tests the

were

AS4

graphite

s u r f a c e t r e a t m e n t s , and t h e and

(PVA), or combination

fibers

treated

polysulfone with

the

with

dell

fiber,

study.

used by

3501-6

Penn and

evaluate the with t h e four

three matrix resins.

thermoplastic, epoxy,

the

b i s r n a l e i m i d e , and t h e Hexcel F155 rubber-toughened The method

to

Unsized

EPON 828 epoxy, p o l y v i n y l a l c o h o l

P1700)

Hercules

conducted

Bowler [ 2 4 ]

were used i n Hercules

4001

epoxy.

was a d o p t e d f o r t h i s

A s i n g l e f i b e r was s e p a r a t e d from t h e 1 2 , 0 0 0 f i l a m e n t tow and

bonded o n t o

a C-shaped m e t a l

tab using Techkits

A-12 epoxy [ 8 ] ,

A

s m a l l p i e c e of masking t a p e was u s e d t o h o l d t h e f i b e r i n p l a c e u n t i l t h e epoxy h a r d e n e d .

The t a b s w i t h t h e a t t a c h e d f i b e r s were hung on a

m e t a l c r o s s b a r , a s shown i n F i g u r e 1 5 .

The f i b e r s were t h e n t h r e a d e d

t h r o u g h i n d i v i d u a l 2 . 5 mm ( 0 . 1 i n ) h o l e s i n 0 . 0 2 5 mm ( 0 . 0 0 1 i n ) t h i c k s t a i n l e s s s t e e l shim s t o c k .

A

s m a l l p i e c e of masking t a p e

was t h e n

a t t a c h e d t h e lower edge of e a c h f i b e r , a s a w e i g h t t o e n s u r e t h a t t h e f i b e r s hung

s t r a i g h t down t h r o u g h e a c h h o l e .

pulverized i n t o

small granules

and enough

F r o z e n r e s i n was t h e n placed i n

each h o l e

to

F i g u r e 15.

S i n g l e F i b e r P u l l o u t Test F i x t u r e .

completely cover

the hole.

minimize its tack, too soon in the

The resin

was used

in frozen

form to

thus keeping the resin from sticking to the fiber

process.

The fabrication fixture with ten suspended

fibers was then placed into a preheated oven at 140°C (285°F) for the Hercules 3501-6 F155

resin.

and 4001 The

temperatures. (350°F)

for

resin

The

resins, and

100°C (212°F)

for the Hexcel

films were

cured

hours at these

Hercules

4 hours.

(350°F) for 4 hours,

3501-6

The

was

for

3

post-cured at 177OC

then

Hercules 4001 was post-cured at 177°C

then for 8 hours at 204°C

(400"~). The Hexcel

F155 was post-cured for 3 hours at 127OC (260°F). All fiber pullout testing

was,performed using an

A metal hook attached

1125 electromechanical universal test machine. to the crosshead of the

end of

the testing machine engaged the

the fiber.

Pulling on

Instron Model

the tab

C-shaped tab at

thus pulled

the fiber

through the resin film. Initially, many fibers were broken due to too thick, thus requiring trials, a technique membrane of pulling

fibers were lb)

microscope Polaroid

of the

to

photographs

document the

films.

load cell.

slides

aid of

pullout.

for achieving

each fiber, and success

recorded on a strip

full scale

force for

was developed

resin around

fibers out

too much

the resin films being

Loads

in making

determination of

an extremely thin was achieved

required to

fiber

in

pull out the

chart recorder using a

The fibers

the

After many

0.2 N (0.05

were then mounted on glass pullout length measurements.

debond

the debond

region were taken, to

length. Fiber

diameters

were also measured from these photographs, knowing the magnification. Interfacial shear

strengths were

then

calculated

using the

simple formula:

where: P = l o a d a t debond D = f i b e r diameter L = debonded l e n g t h

SLC'TION 4 EXPERLdENTAL RESULTS 4.1

Fiber Surface Treatment Characterization All four fiber surface treatments were chemically characterized,

to

verify

surface of fiber

the

presence

of

the

proper chemical treatments on the

the AS4 fiber used in this study.

sizings was

performed

by

This fingerprinting of

Midwest Research Institute (MRI),

Kansas City, Missouri,

on a subcontract basis to the

Wyoming.

yarn

Four

fiber

samples

were

Institute, these being taken from the prepreg for the program. was used to characterize four fiber samples.

sent to Midwest Research

same fiber spools used to make

Internal reflectance infrared spectroscopy the graphite fiber coatings present

methylene

PVA-sized, and

polysulfone-sized fibers, with water

chloride

fiber sample.

for

unsized,

828-sized,

also being used

Spectra were then compared with

handbook spectra for the same polymers. for reference.

the

The extracted sizings were dried and

then analyzed using IR spectroscopy.

calculated also,

on the

The fiber coatings were dissolved from the fiber

surface using

on the PVA-sized

University of

Coating weight percents were

The infrared

the fiber sizings corresponded to the handbook

spectra obtained for spectra in all cases.

A copy of the MRI report 1s reproduced as Appendix D of this report. 4.2 Neat Resin Properties Both the Hercules 4001 and the Hexcel F155 matrix materials were tested

in neat

3.5. Uniaxial

resin (unreinforced) tensile and Iosipescu

form, as

discussed in Section

shear tests were

performed, as

functions of both temperature and moisture content. Average uniaxial tensile

test results are presented in Table 2.

Individual tensile test specimen results are given in Tables A2

of

Appendix

Appendix B. each

A,

with

individual

As will be noted,

of four

stress-strain

A1 and

plots given in

the two resin systems were tested

environmental conditions,

i.e., 23°C

at

(73OF) and 38°C

(lOO°F), dry and wet, for both the ~ercules4001 and the Hexcel F155. The

F155 epoxy

relatively

is a

low

121°C (250"~) cure epoxy;

temperature

to

allow

it was tested at a

properties

to

be

measured

consistent with its lower cure temperature and iower glass transition (Tg) temperature. 204°C

The

(400°F); but

Hercules 4001 bismaleimide resin was cured at

it was

tested at

the same

temperatures as the

F155. As previously noted, been

tested

available.

in

prior

the Hercules 3501-6

studies

Hercules

had

[9,10], and thus data were already

These results are also presented in

presentation of

epoxy neat resin

3501-6

properties

Table 2.

A complete

is given in Reference

[I21 Referring to and

Table 2, it

4001 neat resin tensile

can be seen

that the Hercules 3501-6

properties are reasonably comparable at

both environmental conditions.

The

higher Poisson's

ratio and the

better modulus retention of the Hercules 4001, a bismaleimide resin, will be noted.

The Hexcel P155

rubber-toughened epoxy exhibited

lower tensile modulus, as expected,

and a relatively high strain

a to

failure. The saturatidn moisture are also given in Table

2.

contents of the three matrix materials While the

Hercules 3501-6 epoxy, at 6

p e r c e n t by

weight m o i s t u r e a b s o r p t i o n , i s n e a r s t r u c t u r a l polymers, i t

r a n g e of n o s t two

systems

tested

here

were

w i l l be n o t e d

even

i m p l i c a t i o n s i n terms of m o i s t u r e

t h e upper end of t h e

higher.

t h a t the other

This

swelling-induced

has' special

internal stresses

i n t h e c o m p o s i t e , a s w i l l be d i s c u s s e d i n S e c t i o n 6 . I o s i p e s c u s h e a r t e s t i n g was a l s o performed on

both the Hercules

4001 and Hexcel P155 n e a t r e s i n s , t o a l l o w measurement of t h e i r s h e a r strengths curves

and

were

shear

noduli.

recorded

environmental

for

Complete

each

shear

specimen

conditions indicated

at

i n Table

stress-shear the

four

strain

different

3 . The I o s i p e s c u s h e a r

t e s t specimens were machined from 0.25 cm (0.10 i n ) t n i c k p l a t e s c a s t a t the

same time a s t h e t e n s i l e t e s t specimens.

test results

f o r the Hercules

summarized i n T a b l e 3 , a l o n g H e r c u l e s '3501-6. T a b l e s A3

4001 and Hexcel

F155 n e a t r e s i n s a r e

w i t h p r e v i o u s l y measured v a l u e s f o r t h e

Individual

and A4 of

The I o s i p e s c u s h e a r

test

specimen

Appendix A , w i t h

data

a r e included i n

individual shear stress-shear

s t r a i n c u r v e s g i v e n i n Appendix B. These s h e a r s t r e s s - s h e a r

s t r a i n curves

f i t and t h e r e s u l t i n g e q u a t i o n s

were s u b s e q u e n t l y curve-

used a s i n p u t t o t h e

micromechanics computer program.

f i n i t e element

D e t a i l s of t h i s c u r v e - f i t p r o c e d u r e

and t h e micromechanics r e s u l t s a r e g i v e n i n S e c t i o n 6 . Referring

again t o

s t r e n g t h of t h e H e r c u l e s dry ksi).

Table 3 ,

be n o t e d

4001 b i s m a l e i m i d e a t t n e

c o n d i t i o n was measured This

it w i l l

t o be v e r y

low, i . e . ,

that the shear

room t e m p e r a t u r e , only

17 MPa ( 2 . 4

i s due t o t h e r e l a t i v e l y b r i t t l e n a t u r e of t h i s r e s i n a t

t h e RrD c o n d i t i o n ,

which makes i t

concentration e f f e c t s .

particularly sensitive to

stress

I t w i l l be n o t e d t h a t t h e s h e a r s t r e n g t h more

m m o m mcuom d

m m o m m m o m A

than doubled

with the

increase of

However, the combined the

shear

strength

significantly.

influence of temperature and again.

This is

The

also

decreased

[11,12], the hygrothermal

the matrix material and

and stiffness properties.

or moisture.

moisture lowered

shear modulus

typical response

environment plasticizing strength

either temperature

As can be

hence reducing its seen in Table 3, the

Hercules 3501-6 epoxy was affected similarly. The Hexcel F155 was not subjected to as

in the ETW

high a temperature

condition, and hence

did exhibit as severe a loss of properties. The coefficient of and Hexcel Section

thermal expansion of both

the Hercules 4001

F155 matrix materials also were measured, as described in

3.5.3.

Averages

presented in Table 4.

of

the

six

tests

for

each

Individual test results and plots

strain versus temperature are included in Appendix B. Hercules 3501-6

epoxy, also

included in

resin are of thermal

The values for

Table 4, were taken

from

References [12,18,19]. The

coefficients of

materials

were

moisture

also measured,

Section 3.5.4.

Average values

test

plots are

data and

Hercules

3501-6

epoxy

expansion of

using

the

the

techniques described in

are reported in Table

contained in Appendix B. also

included

in

two matrix

Table

5.

Individual

The values for 5 were taken from

References [12,18,19]. 4.3

Composite Fiber Volume Contents Fiber

The fiber method

volumes were

measured on

volume determinations were

described in

ASTM Standard

all sets

of composite panels.

made using the STD D3171-76.

acid digestion Three replicates

were measured for each panel, with good correlation between the three

samples.

Table

plates tested.

6 gives

the average

Detailed

fiber volumes

results are presented in

for each set of

Tables A5 through

A7 of Appendix A. For the unidirectional composite panels, variation

from

one

fiber

another, which must be

surface

there was considerable

treatmentlmatrix combination to

taken into consideration when comparing the

measured composite strength and

stiffness properties.

done later in this section, and also in Sections

This will

be

6 and 7 when making

analytical/experimental correlations. The

fiber volumes

of the

quasi-isotropic laminate panels also

varied significantly, as indicated in Table 6. the

AS4/F155

composites

in

general were

The fiber volumes of

lower then those of the

Hercules 3501-6 and 4001 matrix

composites, because of the different

prepregging

Of

value for Because

procedures the unsized

of the

used.

particular

AS4/F155 quasi-isotropic

different handling

note is the very low composite laminate.

characteristics of

the graphite

fibers having different surface finishes, it was difficult to control the

resin

content

processes. operation,

In

a

accurately. during larger

this desired

the

program, as

uniformity would

iterations over a period of time.

prepregging

and curing

in a commercial prepregging be achieved by successive

This was not practical to

attempt

in the present study. 4.4

Unidirectional Composites The 12 combinations of

to transverse

unidirectional composites were subjected

tensile and axial

compressive loadings, at

temperature, dry, and elevated temperature, wet are presented in the next two subsections.

both room

conditions.

Results

Table 6 Average Fiber Volumes For the Various Graphite/Polyrner Matrix Composite Plates

Unidirectional Panels

Quasi-Isotropic Panels

Uns ized

47.3

54.5

EPON 828

58.9

58.8

PVA

56.7

64.1

Polysulfone

52.4

52 .O

56.?

52.2

EPON 828

40.0

43.8

PVA

39.7

47.4

Polysulfone

4 4 .O

4 2 ..2

AS4/4001 clns ized EPON 8 2 8

Polysulfone AS4/F155 Uns ized

4.4.1

Transverse Tension Both

unidirectional

composite

quasi-isotropic laminate axial tensile 12

fiber/matrix

laminates

are

combinations.

presented

in

transverse

tensile

testing was performed for all

Results

for

the

quasi-isotropic

Xeasurements of tensile

Section 4.6.

modulus, ultimate tensile strength, and ultimate tensile made, at

two environmental

and

conditions, viz,

strain were

room temperature, dry

(RTD) and elevated temperature, wet (ETW), i.e., 93°C (200"~)for the Hercules

3501-5 and 4001 matrix composite specimens and 38°C (100°F')

for

Hexcel

the

El55

matrix

composite specimens.

The Hexcel El55

composites were tested at a lower temperature because the F155 matrix is a 121°C is cured

(250'~) cure temperature system while the Hercules 3501-6 at 177°C

(350°F) and

Testing the Hexcel F155 matrix

the Hercules

4001 at 204°C (400°F).

composites at 93°C (200°F) would have

resulted in very low mechanical properties, which would have made it difficult system.

to

evaluate

the

fiberlmatrix

interface

for that resin

Therefore, the Hexcel F155 was tested at what was considered

an equivalent temperature, considering its

cure temperature relative

to the Hercules 3501-6 and 4001 cure temperatures. Transverse performed

tensile

testing

to help evaluate

test

results for all

Tables 7 These

and 8 , for

same data

unidirectional

the effectiveness of

between the Hercules AS4 graphite treatments) and the

of

the interface bond

fiber (with four different surface

three polymer matrices.

Average values of

12 fiber/matrix combinations the RTD and

are also

composites was

the

are presented in

ETW test conditions, respectively.

plotted in

bar chart

form in Figures 16

through 21, for ease of visualization of possible trends.

Individual

.

test

specimen results

~ppendix A, with

are

included

in

Tables

individual stress-strain

A8 through A13 of

curves being included in

Appendix B. Reference will be made first results

(Figures

respectively). AS413501-6

16

and

At

17

the

for

room

unidirectional

to the transverse tensile strength the

RTD

temperature,

composites

clearly

strengths, for all fiber surface treatments. exhibited strengths

about twice

poorest performer.

There were variations

dry

conditions,

condition, the

exhibited the lowest

The AS414001 composites the PVA

as high,

ETW

and

sizing being the

in fiber volume

from one

fiberlmatrix combination to another (as previously presented in Table 6).

However,

there does not appear to be a correlation between high

transverse tensile strength and low fiber volume content, as might be expected spaced

based

upon

the

fibers result in

well

established

fact that more closely

higher stress concentrations in the matrix

material [26-281. temperature, dry (RTD) transverse tensile strengths of

The room the

AS41F155 unidirectional composites were as high, or higher, than

those of the ~S4/4001composites. At

the ETW

strengths were Figure 17 is true

also

condition (see all significantly

plotted to the same for

all

subsequently, to make appear to have the

other

Figure 1 7 ) , lower.

(It

should be

scale as Figure 16.

comparison

plots

comparisons easier.)

to

noted that This will be

be

presented

The AS41F155 composites

better strength retention in general, but it must

be noted (see Table 8) that these tests were (lOO°F).

the transverse tensile

conducted at only 38°C

Table 7 Average Unidirectional Composite Transverse Tensile Test Results At the Room Temperature, Dry Condition Composite Material System

Ultimate Strength (1YPa) (ksi)

Tensile I.lodulus (GP~) (~si)

Ultimate Strain (percent

iJnsized

22

3.2

7.9

1.2

0.29

EPON 828

22

3.2

7.7

1.1

0.28

Polysulfone

23

3.4

7.6

1.1

0.30

Uns ized

49

7.1

Y .5

1.4

0.56

EPON 828

55

8.0

8.8

1.3

0.61

PVA

37

5.4

8.1

1.2

0.46

Polysulfone

48

7 .O

9.1

1.3

0.55

Unsized

60

8.7

6.9

1 .O

EPON 828

50

7.3

7.9

1.2

PVA

37

5.4

7.5

1.1

Polysulfone

67

9.8

7.7

1.1

AS4/4001

~S&/F155

Table 8 Average Unidirectional Composite Transverse Tensile Test Results At the Elevated Temperature, Wet Condition

Composite Material System AS4/3501-6 Unsized EPOM 828 P VA Polysul fone AS4/4001 Uns ized EPON 828 PVA Polysulfone AS4/F155 Uns ized EPON 828

PV A Polysulfone

'Test Temperature ("C)

Ultimate Strength (ma) (ksi)

Tensile Ultimate lYodulus Strain (GPa) ( ~ s i ) (percent)

Unidirectional Composite Transverse Tension Room Temperature, Dry (RTD)

POLYSULFONE

Figure 16.

Unidirectional Composite Transverse Tensile Strengths of the Twelve Fiber S i z i n g / ~ a t r i xCombinations at the Room Temperature, Dry Condition.

Unidirectional Composite Transverse Tension Elevated Temperature, Wet (ETW)

Figure 17.

Unidirectional Composite Transverse Tensile Strengths of the Twelve Fiber Siring/ Matrix Combinations at the Elevated Temperature, Wet Condition.

Unidirectional Composite Transverse Tension Room Temperature, Dry (RTD)

F i g u r e 20.

Unidirec Fiber S i

Unidirectional Composite Transverse Tension Elevated Temperature, Wet (ETW)

Figure 2 1 .

The transverse the RTD and

ETW conditions, respectively, are also shown as three18 and 19.

dimensional plots in Figures

was relatively little variation in did exhibit Table 7.

7 and 8 for

tensile moduli, tabulated in Tables

the highest

At room

modulus.

moduli, which

temperature, there

The AS414001 composites

can perhaps

be best seen in

It would have been expected that the Hercules 3501-6 matrix

composites

have

the

highest

moduli,

since the fiber volumes were

comparable to those of the Hercules 4001 matrix composites (see Table 6) and the matrix tensile modulus is higher (Table 2).

In fact, the

composite transverse moduli of the Hexcel F155 matrix composites were about as lower

high, even

(Table 2 )

able

6).

relation

though the

and

the

composite

These trends will to

the

finite

modulus of

this matrix material is

fiber volumes were also lower in Section 6 in

be discussed further

element micromechanics

predictions of

composite response. At

the

ETW

various composites

condition, the decreased by

transverse

tensile moduli of the

40 percent

20 to

relative to

the

corresponding RTD values, as can be seen by comparing Tables 7 and 8. The AS4/F155 composites were degraded the most, even though these ETW tests were conducted at only 38°C ( 1 0 0 " ~ )as ~ opposed to 93OC (200°F') for

the

other

fiber-matrix

two

matrix

interface

systems.

debond

The

may

suggestion is

have

hygrothermal conditioning prior to testing, or stages of the transverse tensile loading. as

will

be

discussed

analytical/experimental

further

correlations

of

occurred

that

during

a the

during the very early

The former is more likely, in

relation

Section 6.

to

the

This may have

occurred for the PVA-sized AS413501-6 composite also, as suggested by

the significant drop in composite modulus. Transverse tensile strains

to failure for all

RTD conditions, are plotted

treatmentlmatrix conditions, for the Figure

20.

As

indicated also

12 fiber surface

7, the

in Table

in

transverse tensile

strains of the Hercules 3501-6 matrix composites were the lowest, for all

fiber

surface

treatments.

This

to

failure values

for

consistent

observed (Figure 16).

transverse tensile strengths also strain

is

the

Hexcel

with the low The

higher

El55 matrix composites

reflect the higher strains to failure of this rubber-toughened matrix material (Table 2 ) .

It will also be noted, however, that this higher

matrix strain to failure is not translated fully to composite strain. The Hercules 4001 matrix exhibited a RTD strain to failure only about 45 percent as high as the Hexcel F155 (see Table 21, yet the AS4/4001 composite transverse strains This

is even more significant when

are taken into account. the

averaged at least

AS4/4001

75 percent as

high.

the differences in fiber volumes

As indicated in Table 6, the fiber volume of

composites

57

averaged

composites averaged only about

percent, while the AS4/F155

40 percent.

That is, there

was much

more of the high strain to failure Hexcel F155 matrix in the AS41F155 composites

than

there

matrix in the AS414001

was

lower

composites.

strain

to failure Hercules 4001

Thus, even though the transverse

tensile strengths were comparable, the

higher strain to

the matrix

to the

did not

typical

[12], and

"tough"

matrix

Figure

21,

the

translate directly indicates one

materials

ETW

for

strains

This

is

practical limitation of developing

use to

composite.

failure of

in

composites. As indicated in

failure for all composite systems

followed essentially the same trends as the RTD data.

4.4.2

Axial Compression Axial

compression

testing

was

unidirectional composites and the room

temperature,

conditions.

(RTD)

dry

also

performed

on

and

elevated

temperature, wet (ETW)

The temperatures and moisture contents

emphasized that the

all three matrix materials, 177°C (350°F) Hercules

for the

4001.

were the same as

cure temperatures were

axial

and 204°C

compressive

test

Again, it

different for

viz, 121°C (250°F) for the

Hercules 3501-6,

The

the

quasi-isotropic laminates, at both

previously defined in Section 4.4.1 for the tensile tests. should be

both

Hexcel F155,

(400"~) for results

for

the the

quasi-isotropic laminates will be presented in Section 4. Axial composites

compression testing to

assist

in

interfacial

strength, by

fibers.

theory, as

In

fiber-matrix

bond

causing the

was performed

the

evaluation

observing

fail

of

the

microbuckling

the interfacial

will

on the unidirectional

earlier

strength is under

fibers to become laterally

fiber-matrix

of the graphite decreased, the

compressive

unsupported.

loading,

They then will

buckle to cause total failure of the composite. The unidirectional summarized

in Tables 9 and

respectively. Figures 22

composite axial

These

data

through 27, as

compressive properties

and ETW test conditions,

10 for the RTD are

also

are

plotted

in bar chart form in

an alternative form

of observing trends.

Individual test specimen data are presented in Tables A14 through A19 of Appendix A, and stress-strain curves are included in Appendix B. At the compressive consistently

room temperature, strengths

of

lower than

the

dry (RTD)

the axial

F155

matrix composites were

the other

two composite systems,

Hexcel

those of

test condition,

Table 9 Average Unidirectional Composite Axial Compression Test Results At the Room Temperature, Dry Condition Composite Naterial System

Ultimate Strength (ma) (ksi)

Compressive blodulus (GPa) (Msi)

Ultimate Strain (~ercent)

Uns ized

719

104

100

14.5

1.33

PVA

797

116

122

17.7

0.62

Polysulfone

839

122

116

16.9

0.97

887

129

128

18.6

0.60

Unsized

547

79

68

9.9

0.97

EPON 828

674

98

86

12.4

0.91

PVA

549

80

79

11.5

0.75

Polysul£one

608

88

91

13.2

0.69

Uns ized EPON 828 PVA Polysulfone AS4/F155

Table 10 Average Unidirectional Composite Axial Compression Test Results At the Elevated Temperature, Wet Condition Composite Material System

Test Temperature ("C)

'

Ultimate Strength ([email protected]) (ksi)

Compressive Modulus (GP~) (~si)

Ultimate Strain (percent)

Uns ized

469

68

79

11.5

0.55

EPON 828

536

78

87

12.7

0.54

PVA

512

74

93

13.5

0.56

Polysulfone

555

80

95

13.7

0.65

Uns ized

581

84

91

13.2

0.80

EPON 828

670

97

122

17.7

0.73

PVA

596

87

107

15.5

0.55

Polysulfone

619

90

123

17.9

0.49

AS414001

AS4/F155 Uns ized EPON 828 PVA Polysulf one

93°C

38°C

Unidirectional Composite Axial Compression Room Temperature, Dry (RTD)

Figure 2 2

.

Unidirectional Composite Axial Compressive Strengths of the Twelve Fiber Sizing/ Matrix Combinations at the Room Temperature, Dry Condition.

independent of fiber surface treatment, the EPO1'4 828 sizing producing the

highest

AS4/F155

compressive

strength. The

unidirectional composites was

fact that the Hexcel F155

fiber

probably associated with the

The lower

matrix stiffness

for the fibers, and hence,

microbuckling

performance of the

has the lowest modulus of the three matrix

materials (see Table 2). lateral support

poorer

under

axial

implies less

an earlier occurrence of

compressive

loading.

This also

accounts for the intermediate compressive strengths of the AS4/3501-6 composites. strength

Within

each

composite

system,

was not strongly influenced by

suggests that axial compression testing is not

the axial compressive

type of fiber sizing.

This

of unidirectional composites

a very sensitive indicator of the efficiency of the interface

bond strength.

The present

data do suggest the importance of matrix

stiffness on axial compressive strength, however. By observing Table 10 made

concerning

further noted,

the

and Figure

23, similar

interpretation of

however, that the axial

the

comments can be

ETW data.

It will be

compressive strengths of all

of the 12 fiber sizing/matrix combinations were significantly reduced in

the

presence

of

a

reduction was relatively matrix materials, lower

environment.

uniform at about

keeping in mind that the

temperature.

compressive

hygrothermal

Presumably

strengths were

30 percent for

to

strength all three

AS4/F155 was tested at a

these reductions

due

The

in composite axial

the reduced stiffnesses of the

matrix materials at the hot, wet conditions of these tests. The axial combinations

compressive moduli of the 12 unidirectional composite at the

RTD condition

compressive moduli of the

are plotted

in Figure

24.

The

Hercules 3501-6 and 4001 matrix composites

were similar

in magnitude.

what would be GPa (34 dsi) and

a

The

predicted for the

measured values are

Hercules AS4 graphite

modulus fiber [2], using

simple

fiber-dominated

rule-of-mixtures property.

slightly below fiber, a 235

the fiber volumes of calculation

[29]

However, the variations

Table 6

for

this

from one type of

surface-treated fiber composite to another appear to be accounted for by the corresponding variations in fiber volume. The much

lower fiber

volumes of

the AS4/F155

composites also

explain why their

composite moduli were lower.

Also, corrected for

fiber volume, the

composite moduli for

would be similar.

The rule-of-mixtures relation would suggest an AS4

all four surface

This was also

graphite fiber modulus of only about 207 GPa (30 Msi). true for the other two groups of composites. the Hercules AS4 graphite as advertised that the

treatments

This could suggest that

fibers used did not have as high a modulus

by the manufacturer

composite modulus

[Z].

However, it

values were

lower than

is more likely predicted by

a

simple rule-of-mixtures relation because of the occurrence of slight fiber misalignments within the composites [291. As

can be

trends in similar

seen by

comparing

Figures 24 and 25, the general

composite compressive modulus at to

those

unidirectional condition

is

observed

composite also

not

axial a

at

room

the ETW

temperature.

compressive modulus

satisfactory

condition were That

is,

at a hot, wet

discriminator of relative

interface bond strength. As an aside, however, it will be noted that the

AS4/4001

increasing

composites

temperature

composites decreased

suffered very

and

moisture

little modulus

loss with

content, while the AS4/3501-6

in axial compressive modulus by 20

percent or

more. also

The ~ S 4 / ~ 1 5 5composites were not tended to decrease

in modulus at

as consistently lower, the ETW condition.

but

That the

AS4/4001 did not decrease in modulus is somewhat surprising since the Hercules

4001 matrix itself did decrease

in modulus at the hot, wet

condition (see Table 2). The

unidirectional

composite

axial

failure, tabulated in Tables 9 and 10, are form

in

Figures

respectively.

26

At

incorporating

and room

unsized

27,

for

strains

RTD the

and

ETW

conditions,

AS4/3501-6

polysulfone-sized

AS4

composites

graphite

exhibited unusually high strains, with the unsized fiber in general exhibiting the highest strains. Figure 2 7 ) ,

fibers

composites

At the ETW condition (see

the differences tended to disappear.

Axial very

to

also plotted in bar chart

the

temperature,

and

compressive

compressive failure

of a

complex fracture process,

unidirectional composite

is a

involving fiber-matrix debonding due

to transverse tensile stresses developed by the Poisson effect, gross longitudinal splitting also caused tensile

stresses,

failures,

and

predominates strong

fiber microbuckling,

gross

within a

influence

by the Poisson-induced transverse

on

45"

angle

shear

specific specimen the

local

composite

longitudinal

failures.

Which

during failure

strain

to

shear mode

can have a

failure

actually

measured. 4.5

Quasi-Isotropic Laminates As

indicated

considerable

in

attention

the was

surface

treated composites

methods

were

test

matrix

given

to

in laminate

of Table 1 in Section 3.1, the performance of the fiber form.

Five

selected, to characterize [+45/0/90], -

different test quasi-isotropic

laminates.

Since

it is in laminate form

graphite/epoxy composites NASA-Ames

was

are

particularly

used

that most high performance

in

interested

aerospace in

applications,

this composite form.

A

quasi-isotropic layup was selected as being of general interest. 4.5.1

Axial Tension Quasi-isotropic laminate axial tensile testing was conducted

all 12 fiber sizing/matrix combinations.

The room temperature,

(RTD) test results are summarized in Table 11. wet ( ~ ' T t l ) results are included in Table 12. are

given in

Tables A20

through A25

stress-strain curves in Appendix these

data are also

B.

on dry

Elevated temperature,

Individual specimen data

of Appendix A, and individual For use in

making comparisons,

plotted in three-dimensional

bar chart form in

Figures 28 through 33. Considering first the RTD axial tensile strength data

are

AS4/F155

plotted

in

Figure

28.

results, these

general, the AS4/3501-6 and

In

composite laminates tended to

exhibit higher axial tensile

strengths than the AS4/4001 laminates. However, there do not to be any clear trends in

the data of Figure 28.

strong correlation between

not a

strength,

appear

Likewise, there is

fiber volume content

and laminate

suggesting that the 0 " plies did not dominate the strength

response. At the ETW condition, the to be 4001

higher than matrix

matrix

at room

temperatures for this only

38°C

temperature for

composites, but

composites.

(10O0F),

It

laminate strengths (Figure 29) tended

generally

should

again

be

the Hercules 3501-6 and

lower noted

for the Hexcel F155 that the ETW test

177°C (250"~)cure rubber-toughened whereas it was

93°C

epoxy was

(200°F) for the other two

Table 11 Average Quasi-Isotropic Laminate Tensile Test Results At the Room Temperature, Dry Condition Composite Material System

Ultimate Strength ( M P ~ ) (ksi)

Tensile Modulus (GP~) (~si)

Ultimate Strain (percent)

Uns ized

452

65.5

40.9

5.93

1.13

EPON 828

430

62.4

41.5

6.02

1.21

PVA

368

53.3

30.8

4.47

1.18

Polysulfone

470

68.2

39.6

5.75

1.20

Uns ized

371

53.8

35.7

5.18

1.06

EPON 828

317

46 .O

29.4

4.27

1.09

PVA

303

44.O

26.9

3.91

1.11

Polysulfone

432

62.6

36.4

5.27

1.21

Unsized

317

46 .O

22.9

3.32

1.39

EPON 828

449

65.2

32.0

4.65

1.44

PVA

452

65.5

32.5

4.72

1.41

Polysulfone

369

53.5

31.1

4.51

1.20

AS4/4001

A~4/P155

Table 12 Average Quasi-Isotropic Laminate Tensile Test Results At the Elevated Temperature, Wet Condition Composite Material System

Test Temperature ("C)

Ultimate Strength (ma) (ksi)

Tensile Modulus (GPa) (rlsi)

Ultimate Strain (percent)

Unsized

451

65.4

42.0

6.09

1.16

EPON 828

481

69.7

42.3

6.13

1.19

PVA

424

61.5

37.4

5.42

1.37

Polysulfone

474

68.8

42.4

6.15

1.21

Unsized

Polysulfone AS4/F155 Unsized EPON PVA Polysulfone

38" C

W z

0 LL 3

u a, n

-Cr r(

V)

3

>

0) rl 0)

3

u

4-l

.d

LI

0)

vI

I,

1

aJ u

u cd cd t-l

ir

r: U

d

a, 0 4J

cd

.r(

U

a e

; IE

0

U U .rl

a x

0 -4

t-l U

0 H

I

yJB~eJJS (B~w)

u a

u

z

bo

e a N Cn .d

.r(

1 -r( CYm

LJJ

z

0 L

5 V)

-add

Quasi-Isotropic Laminate Axial Tension Room ~kmperature,Dry (RTD)

Figure

Quasi-Isotropic Laminate Axial Tensile Strains to Failure of the Twelve Fiber S i z i n g l ~ a t r i xCombinations at the Room Temperature, Dry Condition.

coinposite

systems,

recalled that the

as

indicated

Table

and the

Hexcel P155

matrix itself

both tension (Table

It

nigh

possible

contributed

to

It

will also be

8 ) stayed relatively high at

strength retention, in is

12.

transverse tensile strengths of the unidirectional

AS4/F155 composites (see Table condition,

in

that the

the ETW

exhibited reasonable

2 ) and shear

(Table 3).

laminate hygrothermal residual stresses

axial

tensile

strength

of the AS4/F155

loss

composite laminates. In

general, laminate tensile

strength does not

appear to be a

sensitive indicator of fiber-matrix interfacial bond strength. Axial plotted

tensile

in Figures 30 and

RTD and ETW to

moduli

strength.

of the

moduli of the

31 for the two

That

is, at

AS4/4001 composites

test conditions.

the ETW

At both

to explain

condition, the axial the

increased significantly, and the

AS4/~155 composites decreased

favorable residual residual

various composite laminates are

AS413501-6 composites increased slightly,

tensile moduli of the

possible

the

conditions, the trends in modulus appeared to be similar

those for

moduli

of

composite strength

slightly.

It is

increases in

often

terms of more

stresses at the hot, wet condition (lower thermal

stresses

due

to

being

closer

to

the

original

cure

temperature, and favorable offsetting stresses due to matrix moisture swelling).

However,

why

composite

obvious.

The graphite fibers

moisture

changes, and all

(as shown

in Tables 2

moduli

increased

are unaffected by the

three matrix materials

and 3).

The

is

not

as

temperature and

become less stiff

unidirectional composite moduli

did decrease at the ETW condition, both in transverse tension ( ~ a b l e s

7 and

8) and in axial

compression (Tables 9 and

10).

Although not

measured here, the in-plane (longitudinal) shear soduli would also be expected

to

decrease.

delamination would

The

also

occurrence of

tend

to

microcracking or local

reduce

the

measured

modulus.

Obviously, more investigation will be required to explain the results observed prove

here.

to

Needless

be

a

to say,

suitable

laminate tensile modulus did not

indicator

of

fiber-matrix

interface

performance. Laminate axial tensile strains to failure are plotted in Figures 32 and 33. was

At both room temperature and elevated temperature, there

very little

from

variation from

one matrix

At the RTD condition (Figure 3 2 ) ,

one fiber sizing to another.

the Hexcel

F155

failure which

matrix

composites

were only

material to another, or

about 15

exhibited composite strains to

percent higher

Hercules 3501-6 matrix composites, even though

than those of the

the strain to failure

of the rubber-toughened Hexcel F155 epoxy itself was over 250 percent higher

than that of the

can be

made between

bismaleimide

Hercules 3501-6 epoxy.

the Hexcel

matrix,

and

F155 matrix

their

Similar comparisons

and the

composites.

Hercules 4001

That

is, neither

fiber-matrix interface strength nor matrix strain to failure appeared to influence the measured laminate axial tensile strain to failure. 4.5.2

Axial Compression The

axial

loaded, side Results

compression testing supported

fixture

are summarized in Tables 13 and

conditions, respectively. presented curves

test

was

in Tables

Individual

A26 through

are included in Appendix B.

A31 of

conducted

described

using

the end

in Section 3.6.3.

14 for the RTD and ETW test test

specimen

Appendix A .

As for the

data

are

Stress-strain

test results of the

Table 13 Average quasi-Isotropic Laminate Compression Test Results A t the Room Temperature, Dry Condition

Composite Material Sys tern

Ultimate Strength (;*a) (ksi)

Compressive Modulus (GPa) (~si)

Ultimate Strain (percent)

Unsized

319

46.3

37.6

5.45

1.35

EPON 828

368

53.3

56.0

8.12

1.07

PVA

356

51.7

47.8

6.94

1.09

Polysulfone

383

55.5

49 . O

7.10

1.30

EPON 828

468

59.3

39.7

5.75

1.98

PVA

386

55.9

47.3

6.87

2.46

Polysulfone

44 5

64.5

44.9

6.52

2.65

EPON 828

28 1

40.7

34.0

4.94

0.88

Polysulfone

256

37.1

26.8

3.88

1.03

AS4/4001 Uns ized

AS4/F155 Unsized

'Table 14 Average Quasi-Isotropic Laminate Compression Test Results At the Elevated Temperature, Wet Condition Composite Material Systern

Test Temperature ("C)

Ultimate Strength (-Ma) (ksi)

Compressive Modulus (GPa) (Msi)

Ultimate Strain (percent)

Uns ized

296

42.9

40.4

5.86

0.87

PVA

213

30.9

29.8

4.32

0.80

Polysulfone

294

42.6

35.4

5.14

0.93

337

48.9

32.1

4.66

1.41

AS^ 14001

Unsized EPON 828

PVA Polysul fone AS4/F155 Unsized EPON 828

PVA Polysul fone

93°C

previous

sections,

the

average

failure are also presented in

strengths, moduli, and strains to

bar chart form, in Figures

34 through

39. The

room

temperature, dry

strengths are plotted combinations.

The

(RTD)

in Figure 34 trends

were

laminate

for all 12

very

sizinglmatrix

fiber

similar

unidirectional composites (see Figure 22).

axial compressive

to

those

That is, while

for

the

there was

no clear trend between fiber surface treatments, there was a distinct trend from

one matrix material to

another.

The AS414001 composites

stronger than the AS413501-6 composites, which in turn

were somewhat

were considerably

stronger than

the ~ S 4 / ~ 1 5 5composites.

unidirectional composites in axial compression (Section was

postulated

to

be

due

different matrix materials 3).

It is interesting

to

the

differences

the

4.4.21, this

in

moduli of the

(as presented previously in

that the same

For

Tables 2 and

trend is observed here, where

only one-fourth of the plies are oriented in the axial direction. As

can

reductions significant.

be

seen

by

comparing

Figure

35

to

Figure 34, the

in axial compressive strengths at the ETW conditions were The Hercules 3501-6 and 4001 matrix composite laminates

decreased an average of about 20 percent in strength; the Hexcel F155 matrix composites

lost an

average of

almost 40 percent.

For

the

unidirectional composites, the strength losses were fairly uniform at 30 percent

for all

Again,

should

it

three systems, be

remembered

as discussed

in Section 4.4.2.

that the AS4/F155 composites were

~ the two 177°C (350°F) cure systems tested at only 38°C ( 1 0 0 " ~ )while were

tested

composites

at

93°C

suffered no

(200°F). more

That

percentage

the

AS4/F155 unidirectional

strength loss

at

the ETW

Quasi-Isotropic Laminate Axial Compression Elevated Temperature, Wet (ETW)

POLYSULFONE

Figure 35.

Quasi-Isotropic Laminate Axial Compressive Strengths of the Twelve Fiber Sizing/ Matrix Combinations at the Elevated Temperature, Wet Condition.

a,.

5g

Quasi-Isotropic Laminate Axial Compression Room Temperature, Dry (RTD)

Figure 38.

Quasi-Isotropic Laminate Axial Compressive Strains to Failure of the Twelve Fiber SizinglMatrix Combinations at the Room Temperature, Dry Condition.

condition than the other two composites, while the AS4/F155 laminates loss of the other two

suffered twice the

laminates, is particularly

interesting. the ETW

At generally

condition, the

exhibited

somewhat

PVA-sized fiber composite laminates lower

strengths.

This

was

not as

evident in the unidirectional composites (~igure23). Room temperature modulus values lower

laminate

composites are volumes

axial

compressive

presumably strongly

are plotted in Figure

36.

stiffnesses

AS4/F155

of

associated with

of these composites (see Table

the

the lower fiber

6 of Section 4.3).

there does not seem to be a strong correlation.

However,

For example, for the

AS4/3501-6 composites, the polysulfone-treated fiber composite much lower fiber volume versus higher.

64 percent,

The

had a

than the PVA-sized fiber composite, viz, 52

yet its

axial compressive modulus was slightly

Likewise, the unsized fiber AS4/F155 laminate had a very low

fiber volume ( 2 8 percent). significantly

lower

than

Yet its axial compressive modulus was not that

of

the

polysulfone-sized

fiber

composite, which had a fiber volume of 42 percent. The laminate axial compressive moduli at the ETW plotted

in

observed

Figure

for

modulus of the low

fiber

modulus

the

37.

The

general

unidirectional

condition are

response was similar to that

composites

(Figure 25).

The low

unsized AS4/F155 composite might be attributed to the

volume

previously

quoted.

of the polysulfone-sized AS4/4001

But,

in contrast, the high

would not be explained by

an abnormally high fiber volume. Thus, while there are clearly as of yet unexplained anomalies in the

data,

no

obvious

trends

seem

to

emerge.

Laminate

axial

compressive modulus

does not appear to be

a meaningful indicator of

fiber-matrix interfacial bond strength. The values

laminated for

all

composite

12

axial

combinations,

compressive at

condition, are plotted in Figure 38.

the

room

strain to failure temperature, dry

The relatively high strains to

failure of the AS4/4001 composites are somewhat surprising. not occur for the unidirectional composites (Figure 26).

This did

As will be

discussed in the next section, the RTD flexural strains to failure of the AS4/4001 laminates were not unusually high; this might have

been

expected based upon the axial compressive strain data shown in Figure 38.

That

is,

possible

concern

would

in these AS4/4001 laminates,

delaminations to the

one

tensile impact

data to

this would be expected to

be

the occurrence of

as discussed in relation

be presented

in Section 4.5.6.

strongly influence the flexure data

But also,

and there was no indication of any anomalous behavior there. At

the

elevated

strains to failure

temperature, wet

condition,

in the AS4/4001 did not

are plotted in Figure 39.

occur.

As for the unidirectional

unusually high

The test results composite axial

compressive strains, the laminate axial compressive strains tended to become For the

more uniform among the 12

combinations at the ETW condition.

unidirectional composites, the strains

for all three matrix

systems were lower at the ETW condition than at the RTD condition, as can be seen by comparing Tables 9 and 10, or Figures 26 and 27. was associated with the uniformly reduced strengths, Section 4.4.2. the ETW

For the laminates, the

conditions were also lower than

Hercules 3501-6

and

This

as discussed in

axial compressive strains at at room temperature for the

4001 matrix systems.

The AS4/3501-6 laminates

averaged about both

cases.

failure

a 50 percent reduction, with considerable scatter in

On

the other

increased

by

AS4/F155 laminate

hand, the 30

about

percent,

strains to

except for the PVA-sized

laminate, which did decrease by about 30 percent. The

cause of the increasing strains

laminates room

at the ETW

temperature.

strengths and

condition was the

These,

moduli

in

at failure of the AS4/F155 exceptionally low values at

turn, are

recorded.

The

associated

corresponding

with the low strengths and

moduli of the unidirectional composites were also low, of course, as previously discussed in Section 4.4.2.

Thus, the ~ ~ 4 1 ~ 1composites 55

generally did not perform as well as the other two composite systems. 4.5.3

Flexure A standard three-point flexure fixture, as

described in Section

3.6.5, was used in conducting all of the tests of the quasi-isotropic laminates.

The average values of the results

obtained are presented

in Tables 15 and 16, for the room temperature, dry (RTD) and elevated

(ETW)

temperature, wet test

specimen results

Appendix A. Bar

test are

conditions, respectively. listed

in

Stress-displacement plots

chart plots are presented

Individual

A32

through A37 of

are included

in Appendix B.

Tables

in Figures 40 through 45, for use in

comparing data trends. The RTD flexural strength averages are plotted in Figure 40. comparing

this

plot

strengths

(Figure

with

341,

it

that can

for the laminate axial compressive be

seen

that the trends are very

similar. This is as expected, since the axial

compressive strengths

were generally higher than the axial tensile strengths. flexural

failures typically

By

occurred on the

That is, the

compressive surface of

Table 15 Average Quasi-Isotropic Laminate Flexural Test Results At the Room Temperature, Dry Condition Composite Material Sys tern

Ultimate Strength ( M P ~ ) (ksi)

Flexural Modulus (GPa) (~si)

Ultimate Strain (percent)

Uns ized

860

125

54.7

7.94

1.57

EPOA 828

881

128

60.1

8.72

1.47

Polysulfone

943

137

59.2

8.59

1.59

94 7

137

67.5

9.78

1.50

1034

150

66.0

9.57

1.57

EPON 828

669

97

40.0

5.80

1.58

Polysulfone

651

94

39.4

5.71

1.75

AS4/4001 Unsized EPOA 828

Polysulfone AS4/F155 Uns ized

Table 16 Average Quasi-Isotropic Laminate Flexural Test Results At the Elevated Temperature, Wet Condition Composite daterial System

Test Temperature ("C>

Ultimate Strength (Pipa> (ksi)

Flexural Modulus ( G P ~ ) (~si)

Ultimate Strain (percent)

Unsized

548

80

54.3

7.87

0.97

Polysulfone

625

91

52.9

7.67

1.14

718

104

66.2

9.60

1.11

854

124

74.9

10.86

1.14

Uns ized

371

54

25.4

3.69

1.47

Polysulfone

407

59

37.2

5.40

1.10

AS4/40~l

93°C

Unsized E P O A 828

PVA Polsulfone AS4/E155

38 O C

Quasi-Isotropic Laminate Flexure Elevated Temperature, Wet (ETW)

Figure 41.

Quasi-Isotropic Laminate Flexural Strengths of the Twelve Fiber Sizing/Matrix Combinations at the Elevated Temperature, Wet Condition.

O

a Qn 2E 5cuo g 7 € cuo 0 =-

a-

a

0

3LT

u

Quasi-Isotropic Laminate Flexure Elevated Temperature, Wet (ETW)

ULFONE

the

specimen.

The

laminates were an

RTD

axial

tensile

strengths

exception, however, being lower

shown previously

in Figure

28.

This

flexural strength trends, however. AS4/4001 laminates were

did not

of the ~S4/4001

than expected, as

carry over

into the

The RTD flexural strengths of the

the hlghest of

all three composite

systems

tested. Figure 41, the ETW flexural

As shown in

strengths followed the

same trends as the RTD strengths. Also, these elevated wet strengths

were consistently

lower than

the corresponding

temperature, dry strengths, just as the axial were.

the ETW

At

laminates

were

strengths, as 29

and 35.

condition, the

than

the

is not

strengths of these axial

compressive

12 and 14, or Figures

can be seen by comparing Tables Thus, it

room

compressive strengths

axial tensile

considerably higher

temperature,

surprising that the flexural strength

data followed the same trends as the axial compressive strength data. As

for the axial compressive

strengths, flexural strengths are

not a suitable indicator of interfacial bond efficiency. The flexural modulus data are plotted in Figures the RTD was

and ETW test conditions, respectively.

similar to that of both

moduli, and not appear

The general response

the axial tensile and axial compressive

a similar conclusion can be to be a

42 and 43, for

drawn.

That is, there does

correlation between flexural modulus and fiber-

matrix interface bond strength at either environmental condition. Laminate flexural strains to failure are presented in Figures 44 and 45 for the RTD and ETW test conditions, respectively. recalled

(see Figule

compressive

strains

38 of to

Section 4.5.2)

failure

of

the

It will be

that the laminate axial ASG/4001

composites were

exceptionally, and

44 that

this

strains to trend

unexplainably, high.

was

not

failure.

to the

carried

In

over

fact, these

laminate axial

It will

be noted in Figure

to the RTD laminate flexural strains were

tensile strains

very similar

in

(as plotted in Figure

321, with the AS4/F155 laminates exhibiting the highest values. Since the ~S4/4001 laminates did not indicate high

axial

compressive

condition, it would be follow the

strain

response when

tested

expected that the ETW flexural

axial strain values, both

was true, as can be

this anomalously at

the ETW

strains would

tensile and compressive. This

seen by comparing Figure 45 with

Figures 33 and

39. In summary, nothing in the flexural test results was unexpected. Unfortunately,

this

test

method

does

not

appear

to

be

a good

indicator of fiber-matrix interfacial bond strength. 4.5.4

Interlaminar Shear Interlaminar

shear

tests, using

the

short beam

shear test

method, were performed on all 12 fiber sizinglmatrix combinations as a

further aid in

evaluating the effectiveness

surface treatments. are

listed in

Average laminate

Tables 17

and 18

elevated temperature, wet test test

specimen

Appendix A.

results

are

of the various fiber

interlaminar shear

for the

room temperature, dry and

conditions, respectively. included

in

strengths

Individual

Tables A38 through A43 of

Bar chart plots are included here, as in Figures 46

and

47. Room

temperature, dry

plotted in Figure Hercules 3501-6

46.

(RTD)

interlaminar shear strengths are

Little difference

epoxy matrix composite

will be noted

in the four

laminate combinations.

The

I'able 17 Average Quasi-lsotrupic Laminate Interlaminar Shear Strengths At the Room 'Tesperature, Dry Condition Composite Material System

-

Shear Strength ( i\Pa 1, (ksi)

Uns ized

30

4.3

Polysulfone

30

4.4

52

7.5

EPON 8 2 8

77

11.1

PVA

63

9.2

Polysulfone

63

9.1

AS4/4001 Uns ized

Polysulfone AS4/P155 Uns ized

'Table 18 Average Quasi-Isotropic Laminate Interlaminar Shear Strengths At the Elevated Temperature, Vet Condition

Composite Material System

Unsized EPON 828

Polysulfone

Unsized EPON 828

PVA Polysulfone AS4/F155 Unsized

EPON 828 PVA Polysulfone

Test 'Temperature ("C)

Shear Strength (ma) (ksi)

Quasi-Isotropic Laminate Interlaminar Shear ~oom Temperature, Dry (RTD)

POLYSULFONE

Figure 46.

Quasi-Isotropic Laminate Interlaminar Shear Strengths of the Twelve Fiber sizing/ Matrix Combinations at the Room Temperature, Dry Condition.

823

EPON

and

polysulfone

unsized

and

shear strengths The

Hexcel

strengths

PVA-sized

fiber

than any of

F155 matrix

of

sizings yielded the highest shear

Hercules 4001 bisrnaleimi.de matrix

strengths of the the

fiber

any

of

composites, with

combinations still having higher

the Hercules 3501-6 matrix composites.

composites

the

three

produced

matrix

the

materials

highest at

shear

the

room

temperature, dry (RTD) condition, with the EPON 828 surface treatment being the best. Elevated temperature, wet (ETW) interlaminar shear strengths are plotted

in

composites

Figure were

47.

The

reduced

in

AS413501-6

baseline shear

strength

only

graphitelepoxy slightly by the

elevated temperature, wet condition, remaining relatively strength independent

of fiber surface treatment.

matrix composites were

828 sizing resulting in On

the

other

strongly, and composites

hand,

the greatest composite shear the

Hexcel

F155

nonuniformly, influenced

fiberlF155 matrix composite

by the

the most.

For example, the

had exhibited one

.

the

lowest

ETW condition.

The

PVA-sized graphite fibers unsized

of the highest

shear

But in the ETW condition

strengths in the RTD condition (Figure 46). displayed

strength loss.

matrix composites were more

unsized and

were degraded in shear strength

it

The Hercules 4001

also influenced only slightly, with the EPON

incorporating the

(Figure 471,

uniform in

shear

strength

of all 12

combinations tested. 4.5.5

Tensile Impact Lnstrumented

tensile

impact

testing

was

performed

at

both

environmental conditions on most of the 12 fiberlmatrix combinations. Only 10 of the 12

combinations were tested at the room temperature,

dry ( R T D ) condition, due to an unexplained problem of delamination of the unsized and PVA-treated graphite fiber composite laminates of the Hercules

4001

bismaleimide

delaminations was

the

matrix.

excessive

A

possible

thermal

cause

stresses

of

these

induced during

cooldown from the cure temperature, as will be discussed later. Elevated

temperature, wet

conducted only

on the Hercules

(ETw)

tensile

impact

3501-6 and Hexcel

F155 epoxy matrix

composites, for all four fiber surface treatments. tensile impact

specimens were (ETW)

temperature, wet

problem of delamination of

a

sufficient

preparing impact

tests.

combinations

of

the

of

extra

composite

Since

at the

none

of

Hercules

to the previously mentioned

Hercules

4001

laminates

to

the

fiber

4001

4001

elevated

in the Hercules 4001 matrix laminates.

amount

additional

No Hercules

successfully tested

condition due

testing was

four

Lack

resin prevented

repeat these tensile surface treatment

bismaleimide matrix composites

could be successfully tested, this suggests that the ETW condition is even more detrimental than the RTD condition. The

averages

of

all

of

the quasi-isotropic laminate tensile

impact tests which were successfully performed are included in Tables 19 and 20. through A48 versus

time

Individual test specimen data are presented in Tables A44 of Appendix A. plots

comparisons, the

are

Individual force

shown

averages

are

in

Appendix

also

versus time and energy

B.

plotted

For ease in making in bar chart form in

Figures 48 through 53. Average tensile impact strength values at the RTD plotted in Figure 48. The AS413501-6 laminates laminates which were

successfully impact

condition are

and the two AS414001

tested all exhibited about

Table 19 Average Quasi-Isotropic Laminate Instrumented Tensile Impact Test Results at the,Room Temperature, Dry Condition

Composite Material Sys tern

Ultimate Strength (ma) (ksi)

Unsized

414

EPON

41 2

Polysulfone

407

Dynamic Modulus (GPa) (Msi)

AS4/4001 Uns ized* EPON 828

385

PVA*

427

62.0

40.0

5.8

Unsized

276

40.0

20.7

3.0

EPON 828

3 34

48.5

30.3

4.4

PVA

36 1

52.4

33.1

4.8

Polysulfone

370

53.6

35.2

5.1

Polysul £one

AS4/F155

*No data taken

-

see text.

Total Energy ( k ~ / )m ~ (ft-lb/in3 )

Average Quasi-Isotropic Laminate Instrumented Tensile 1mpac't Test Results at the Elevated Temperature, Wet Condition

Composite Material System

Test Temperature ("C)

Ultimate Strength (ma) (ksi)

Dynamic Modulus (GPa) (~si)

Total Energy ( k ~ / m ~ ) (ft-lb/in3)

Uns ized

38 1

55.3

40.0

5.8

1349

30

EPON 8 2 8

507

73.5

40.0

5.8

1529

34

PVA Polysulfone AS4/4001 Uns ized EPON 8 2 8 No data taken PVA Polysulfone AS4/F155 Uns ized

-

see text

m

c

.d 1

h M

9

M

rl

I

QI.

c

u

W

'44 w

4

m

U

0

n m

B

E

1 -J

3 V

h

.d V)

u rox a

d

3

w

E 4 m 3

c a h

O

n

O X m

a

u

w

Quasi-Isotropic Laminate Tensile Impact Room Temperature, Dry (RTD)

Figure 48.

Quasi-Isotropic Laminate Tensile Impact Strengths of the Ten Fiber Sizing/~atrix Combinations Successfully Tested at the Room Temperature, Dry Condition.

Quasi-Isotropic Laminate Tensile Impact Room Temperature, Dry (RTD)

.

Figure 52

Quasi-Isotropic Laminate Tensile Impact Energies of the Ten ~ i b e rSizing/Matrix Combinations Successfully Tested at the Room Temperature, Dry Condition.

Quasi-Isotropic Laminate Tensile Impact Elevated Temperature, Wet (ETW)

LYSULFONE

Figure 5 3

.

T

Quasi- so tropic Laminate Tensile Impact Energies of the Eight Fiber ~ i z i n g l ~ a t r i x combinations Successfully Tested at the Elevated Temperature, Wet Condition.

the same

tensile strength, viz, approximately 415 m a (60 Ksi).

the AS413501-6 laminates, tensile tests (see Table laminates successfully

this was about the same 11 of Section 4.5.1).

impact tested, this

tensile impact strengths of the AS4/F155

For

as for the static

For the two AS4/4001

was also true.

The RTD

laminates averaged about 20

percent lower than the corresponding static tensile

strength values,

except for the polysulfone-sized fiber laminate strengths, which were the same in both tests. The tensile El55

impact strengths of the

matrix laminates tested at the

Hercules 3501-6 and Hexcel

ETW condition were, on average,

the same as the RTD impact strengths.

about scatter

in the data, as can be

However, there was more

seen in Figure 49.

The low impact

strength of the unsized AS4/F155 laminate can be explained b y t h e low fiber

volume content

for this

matrix combination (see Table 6

particular fiber

surface treatment/

of Section 4.3).

On the other hand,

the exceptionally high tensile impact strengths of the EPON 828-sized and

polysulfone-sized

terms

of fiber

~S4/3501-6 laminates

volume differences.

cannot be explained in

As indicated

in Table

6 , the

fiber volume of the polysulfone-sized laminate was the lowest of

all

four, while that of the EPON 828-sized laminate was relatively high. Tensile impact condition

are

(dynamic) moduli

plotted

in

Figure

at the

50

for

room temperature, dry the

ten

fiber surface

treatmentlmatrix combinations which were successfully tested. the RTD moduli did the

tensile

impact

strengths

not vary significantly

one exception being the

As for

(Figure 481, the tensile impact

from one combination

to another,

unsized fiber/F155 matrix combination,

which was somewhat lower than all the others.

As for tensile impact

strength, this

can p r o b a b l y be e x p l a i n e d by

t h i s composite.

The

t h e low f i b e r volume of

dynamic modulus v a l u e s

t h e s t a t i c t e n s i l e moduli,

were a b o u t t h e

i n some c a s e s b e i n g a b i t

same a s

h i g h e r , and i n

o t h e r c a s e s , a b i t lower. The ETd l a m i n a t e t e n s i l e impact moduli same

trends

increasing

as or

the

( F i g u r e 5 1 ) f o l l o w e d The

RTD

values,

and

e x h i b i t e d no c l e a r t r e n d o f

decreasing

modulus

with t e s t i n g environment.

dynamic moduli t h u s tended t o be lower t h a n t h e moduli, as those

c a n be

of

Table

moduli were to

the

s e e n by 12

of

comparing t h e

Section

4.5.1.

significantly

higher

fiber

corresponding s t a t i c

r e s u l t s of

T a b l e 20 w i t h

That t h e AS413501-6

h i g h e r t h a n t h e A S 4 / ~ 1 5 5 impact

These

impact

moduli was p r o b a b l y due

volumes

of

the

AS4/3501-6

laminates. The RTD t e n s i l e F i g u r e 52.

impact t o t a l e n e r g y a b s o r p t i o n s

The t o t a l e n e r g y

and 4001 m a t r i x l a m i n a t e s was

(28 ft-lb/in3).

are plotted in

a b s o r b e d by each of t h e H e r c u l e s 3501-6 a b o u t t h e same,

The t o t a l impact e n e r g y

v i z , a b o u t 1260 kJ/m3

a b s o r b e d by t h e Hexcel F155

m a t r i x c o m p o s i t e s a v e r a g e d o n l y a b o u t 1035 kJ/m3 ( 2 3 f t - l b / i n 3 ) , w i t h t h e PVA-sized ft-lb/in

1.

~ s l i g h t l y h i g h e r a t 1170 k ~ / m(26

f i b e r laminate being 'This

higher value

might be

e x p l a i n e d by t h e s l i g h t l y

higher f i b e r

volume of t h e PVA-sized

t h i s was n o t

s u p p o r t e d by a c o r r e s p o n d i n g l y low

fiber/F155 laminate.

However,

impact e n e r g y v a l u e

f o r t h e u n s i z e d f i b e r I F 1 5 5 l a m i n a t e , which had a v e r y low f i b e r volume. At

the

elevated

temperature,

wet

test

condition, the t o t a l

impact e n e r g y v a l u e s i n c r e a s e d , a s c a n be s e e n by comparing F i g u r e 53 with Figure 52.

Proportionally,

t h e i n c r e a s e was

much g r e a t e r f o r

the ~ S 4 / ~ 1 5laminates, 5 viz, the EPOli 828 and PVA-sized fiber

two of

composites.

Yhy these

two laminates should

be so much

higher than

the others is not obvious. 4.6 The detailed procedures for performing the tests

were

presented

in

Section

3.6.8.

single fiber pullout 12

All

fiber

treatment/matrix combinations were tested, with varying

surface

degrees of

success, this being extremely delicate work. Although impossible

all

12

combinations were

in the present effort to

fibers in all cases.

tested,

it

proved to be

achieve a proper pullout of the

The EPOiq 828 sizing

combined with any of

three resins proved to be the most difficult to work with. 828 fiber surface treatment always than fiber pullout, the

This EPON

resulted in fiber breakage rather

indicating a high interfacial bond strength for Likewise, the Hexcel F155 resin combined with

EPOA 828 sizing.

all four

the

fiber surface treatments was difficult

to work with.

Only

the polysulfone-sized fibers were successfully tested with the Hexcel F155 resin.

in

the

always

Wany iterations were tried, varying the size of the hole

shim

stock

a broken

and

the

fiber rather

cure temperature. than fiber

But the result was

pullout.

The resin films

could not be made thin enough to pull fibers through

the Hexcel El55

film. The averaged results

for the single

were successful are presented in Table 2 1 .

fiber pullout tests

which

Individual test specimen

results are included in Tables A49 through A51 of Appendix A, for the three matrix materials. pullout

are presented

Photographs of typical single in Figures

fibers after

54 through 60, representing

all

Table 21 Average Single Fiber Pullout Test Results for AS4 Graphite Fibers in the Three Different Matrix Materials

Matrix Material

Fiber Sizing

Fiber Diameter (p)(lo-" in)

Hercules 3501-6 EPOXY

Hercules 4001 Bismaleimide

Hexcel F155 Rubber-Toughened Epoxy

Embedded Length (mm)

Interfacial Shear Strength (1~1Pa) (ksi)

(10-~in)

Uns ized

8.4

3.3

94

3.7

32.6

4.7

PVA

7.4

2.9

134

5.2

32.4

4.7

Polysulfone

8.3

3.3

84

3.3

41.5

6.0

Uns ized

8.4

3.3

201

7.9

20.2

2.9

PVA

9.3

3.7

169

6.7

16.3

2.4

Polysulfone

8.9

3.5

102

4.0

40.3

5.9

Polysulfone

8.6

3.4

130

5.1

21.1

3.1

Figure 54.

Optical Photomicrograph (80x1 of Single Fiber Pullout Specimen A E R Y 0 4 ; Unsized A S 4 Graphite Fiber and Hercules 3501-6 Epoxy Matrix, Showing the Top Aeniscus at A and the Bottom o f t h e R e s i n Film at 0 .

JRi168NAIb PAGE 1% OF POOR QWk!m

F i g u r e 55.

O p t i c a l P h o t o m i c r o g r a p h ( 5 0 ~ )o f S i n g l e F i b e r Pullout Specimen AERY21, PVA-Sized A S 4 G r a p h i t e F i b e r and H e r c u l e s 3501-6 Epoxy X a t r i x , Showing t h e Top Meniscus a t A and t h e Bottom of t h e R e s i n F i l m a t 8.

ORIGINAL PAGE -IS?. OE W O R QUAllPV a

Figure 56.

Optical Photomicrograph (64x1 o f Single Fiber Pullout Specimen A E K Y 3 2 , Polysulfone-Sized AS4 Graphite Fiber and Hercules 3501-6 Epoxy, Showing the T o p Meniscus at A and the Bottom of the Resin Film at B.

Figure 57.

O p t i c a l P h o t o m i c r o g r a p h (320X) o f S i n g l e F i b e r P u l l o u t S p e c i m e n AERZOO, U n s i z e d AS4 G r a p h i t e F i b e r and H e r c u l e s 4 0 0 1 B i s m a l e i m i d e , Showing t h e Top M e n s i c u s a t A a n d t h e a o t t o r n o f t h e R e s i n Film a t 3.

Figure 58.

Optical Photomicrograph (320X) o f Single Fiber Pullout Specimen A E R Z 2 0 , PVA-Sized AS4 Graphite Fiber and Hercules 4001 Bismaleimide, Showing the Top Meniscus at A and the Bottom of the Resin Film at 3.

Figure 59.

Optical Photomicrograph (50X) o f Single Fiber Pullout Specimen A E R Z 3 0 , Polysulfone-Sized A S 4 Graphite Fiber and Hercules 4001 Bismaleimide, Showing the Top deniscus o f A and the Bottom of Resin Film at B.

Residual material to the right o f A will be noted, indicating that the debonding was not entirely clean.

ORJGBNAL PAGE 16 OF POOR QUALlm

Figure 60.

Optical Photomicrograph (320x1 o f Single Fiber Pullout Specimen AERX31, Polysulfone-Sized AS4 Graphite Fiber and Hexcel F155 Epoxy, Showing the Meniscus at A and the Bottom of the Resin Film at B.

three

matrix

materials.

C for

Appendix

reference.

what was t h e t o p

These

photographs

included i n

t h e meniscus a t

where t h e b o t t o m o f

T h e s e l o c a t i o n s a r e marked A and B , r e s p e c t i v e l y ,

on t h e photographs. diameters

are

p h o t o g r a p h s show

s u r f a c e o f t h e r e s i n f i l m , and

t h e f i l m had b e e n .

fiber

Additional

Photographs such a s t h e s e were used t o d e t e r m i n e

and

film

thicknesses.

They

also

p r o v i d e d some

i n s i g h t a s t o t h e n a t u r e of t h e p u l l o u t s . As

can

resulted

be

seen

in

21,

the

polysulfone-sized

fibers

i n t h e highest i n t e r f a c i a l shear strengths for the Hercules

3501-6

and 4 0 0 1 r e s i n s .

to

even

be

Table

PVA-sized

higher,

fibers

H e r c u l e s 3501-6

The EPON 8 2 8 c o m b i n a t i o n s c o u l d b e i n f e r r e d

since

no

fiber

performed

as

well

epoxy, b u t

not quite

p u l l o u t s were a c h i e v e d . as

The

the unsized f i b e r s i n the

as well

i n t h e H e r c u l e s 4001

bismaleimide. It

w i l l be noted t h a t t h e r e

was some v a r i a t i o n i n AS4 g r a p h i t e

f i b e r d i a m e t e r , a s i s t y p i c a l o f t h e PAN p r e c u r s o r g r a p h i t e f i b e r s i n general (see,

f o r example,

film thickness ( i . e . ,

the

from o n e r e s i n s y s t e m t o t h e H e r c u l e s 3501-6 Penn, e t

al.

[24]

Reference [ 2 4 ] ) .

Likewise, the average

embedded l e n g t h o f t h e f i b e r ) another.

The t h i n n e s t f i l m s were

matrix, being approximately 8 0 p found, using

t h i c k n e s s e s l e s s t h a n 300

also varied

a similar

t h i c k had t o b e

used f o r

t o 1 3 0 ~t h i c k .

epoxy m a t r i x ,

that film

u s e d when t e s t i n g K e v l a r

f i b e r s , b u t f o r g r a p h i t e f i b e r s , t h e t h i c k n e s s had t o b e l e s s t h a n 5OU.

However, Penn a l s o m e a s u r e d c o n s i d e r a b l y h i g h e r s h e a r s t r e n g t h s

t h a n i n d i c a t e d h e r e i n T a b l e 2 1 , h i g h e r by a f a c t o r o f two t o Thus, t h e r e l a t i v e successes i n f i b e r s out without breaking

three.

terms of being a b l e t o p u l l g r a p h i t e

them a p p e a r t o b e s i m i l a r .

P e n n ' s work

1241 also pullouts

correlates with the using

the

EPON

inability to obtain

828

sizing

in

the

,

successful fiber

present study.

The

thinnest fibers which could be obtained were still too thick. Unfortunately, no

unidirectional composite longitudinal shear

tests were called for or performed results

having been presented

completely valid

on the quasi-isotropic laminates,

previously in Table

comparison, the

EPON

828

17.

While not a

sized fiber composite

laminates did produce the highest shear strengths in all cases. further shear

supports

strength of

the

assumption that

the EPON

828 sized

This

it was the higher interface fibers that

prevented their

being tested successfully in pullout. For the Hercules 3501-6

matrix, the shear strengths as measured

from the single fiber pullout tests (Table 21) agreed reasonably well with the laminate interlaminar shear strengths [24], using both

al.

unidirectional correlations. with

short beam shear

graphite/epoxy

Penn, et

and Iosipescu shear tests of

composites,

obtained

similar

Penn's single fiber pullout tests tended to be lowest,

the short

beam shear

results the highest of all. 35

(Table 1 7 ) .

results higher,

and the Iosipescu shear

The Iosipescu shear results were

about

percent higher than the single fiber pullout shear strengths.

should

be noted that

It

for the ~evlar/epoxy system, Penn's Iosipescu

shear results were 270 percent

higher (i.e., higher

by a factor of

2.7). As will be matrix

noted by comparing the results for the Hercules 4001

in Iables 1 7 and 21,

2.5 times higher the unsized

the laminate shear strengths were about

than the single

fiber pullout shear

strengths for

and PVA-sized fibers, but only 1.3 times higher for the

polysulfone-sized fibers. For were

the

Hexcel

E l 5 5 matrix,

successfully

quasi-isotropic

pulled

only the polysulfone-sized fibers

out.

laminate was

The

2.9 times

Penn [24], the coefficient of thermal

shear

higher.

strength As

of

pointed out by

expansion mismatch between the

graphite fiber and the matrix can be

an important parameter.

cooldown from

the matrix contracts

the

the cure temperature,

fiber diameter,

fiber-matrix shear

inducing a

interface.

properties.

compressive residual La

This

The

favorable

During

more than

stress at the

in terms of enhancing

P155 matrix

Hexcel

the

is

cured

at a lower

temperature than the other two matrix systems, which results in lower residual stresses. Since the

single fiber pullout specimen

normal composites, the internal

low fiber volume content compared to stress states are also

different.

has effectively a very

Thus, direct comparisons

of test

results must be carefully qualified. As previously noted, the single fiber pullout test used here was developed

al. [ 2 4 ] .

by Penn, et

with a

different single

single

fiber in a dogbone-shaped

material.

The

specimen.

A

observe matrix

the

single special

Drzal

fiber specimen

fiber

cracking under a

configuration.

He

casts a

miniature tensile coupon of matrix

runs

mechanical

fiber-matrix

[30] has worked extensively

from loading

interface microscope.

end

to

end of the resin

device

was designed, to

bonding,

fiber

fracture, and

Drzal's specimen configuration

and loading device were duplicated at the University of Wyoming, with Drzal's

cooperation

and

guidance.

A

photograph

fixture and a typical specimen is shown in Figure bl.

of

the loading

Figure 61.

S i n g l e F i b e r Compo'site T e n s i l e Specimen and L o a d i n g Fixture ( a f t e r Drzal [ 3 0 ] ) .

Drzal used

low cure temperature,

high strain to

failure model

resins as the matrix material, and achieved well controlled failures. In

the present investigation

three

matrix

materials

epoxy, Hercules 4001 epoxy.

As

it was, of

already

course, desired to use the

identified,

bismaleimide, and Hexcel

previously presented in Table 2

viz,

Hercules 3501-6

F155 rubber-toughened

of Section 4.2, even the

rubber-toughened epoxy exhibited a tensile strain to failure about 3.5 percent.

The strains to

failure of the

materials were only about half this value. not

prove to be suitable, producing

aside for

the present study.

were made, however.

of only

other two matrix

Thus, the test method did

unstable fractures, and was set

Single fiber specimens of good quality

Thus, the technique is available for future use,

if needed. In summary, the single fiber the

present

study

were

only

pullout tests conducted as part of partly

successful.

Considering the

extreme difficulty in performing these very time consuming is questionable as to whether The data required.

It

would

appear,

based

tests, it

obtained are worth the effort both

on

the extensive effort

expended here and the prior efforts by Penn, et al. [24], that it may be

much

more

meaningful

to

unidirectional composites instead.

perform

shear

tests

on

actual

SECTION 5 SCANNING ELEC'1'RONL~ICROSCOPEXESULTS 5.1

Introduction

A

JEOL JSM-35C scanning electron microscope was used for all of

the work

of the present study.

This

instrument has a magnification

range from 10X to 180,00OX, a depth of field of 30p

at 1000X, and a

0

resolution of 60A. 5.2

Specimen Preparation

A

total

of

48

specimens were

representing

all of the environmental

tensile

axial

and

compression

polymer matrix composites.

The

mounted

for

examination,

conditions for the transverse

testing

of

the 12 graphite fiber/ mm ( 1 . 0

SEA specimen mounts were 25

in) in diameter.

A Buehler No. 4150 silicon carbide cutoff blade was used the SLd specimens from the failed test articles. paint was used to bond which

the

surface

debris.

All

A silver conducting

the SEi$ specimens to the brass

specimens were

ultrasonically

specimens were

to cut

cleaned

mounts, after to remove loose

subsequently vapor-coated with

gold to make them electrically conductive.

5.3 Explanation of SEM Photographs Specimens conditions, transverse

representing both

and

both

tension

following pages,

and

test

unidirectional axial

temperature composite

compression, were

selected SEN photographs

test

and

moisture

types, i.e.,

studied.

On the

are shown along with,

to

the

extent

possible, a

surface features.

The

description/interpretation of the fracture

48 photographs represent both the RTD and ETW

test conditions for all 12 fiber sizinglmatrix combinations, for both loading conditions. The

first

24

figures, i.e.

Figures

62

through

photographs of fracture surfaces for transverse tensile unidirectional composites. Figures

62

composite: RTD

through

tests of the

The first eight of the photographs, i.e.,

69, are

for

the AS4/3501-6

unidirectional

four representing the four different fiber sizings at the

test

condition, followed

condition.

by

The photographs are

unsized,

via,

85, are

photographs,

EPON i.e.,

unidirectional composite

the ETW test

representing

always presented in the

828, PVA, Figures

four

70

and

polysulfone.

through

transverse

eight photographs of the group, Figures

The

77, depict

tensile

same order, next eight

the

failures.

AS4/4001 The final

78 through 85, represent the

AS4/F155 composites. The

next

24

figures,

i.e.,

photographs of fracture surfaces of

Figures 86

through

109,

are

unidirectional composites tested

in axial compression.

The order

of presentation is the same

as for

the transverse tensile

tests.

Figures 86. through 93 represent

the

AS4/3501-6 composites for the four RTD tests followed by the four ETW tests.

Figures 94

through 101 are for the

AS4/4001 composites, and

Figures 102 through 109 represent the AS4/F155 composites. Each of these 48 SEM of the failures observed. presented in the aeliberate.

photographs was selected as being The inclusion

typical

of so many photographs, and

body of this report rather than in an appendix, was

These

photographs

are

very

valuable

indicators

of

the degree

of fiber-matrix

interface bonding,

differences from one system to another.

and document

subtle

They should also prove to be

very useful in future studies, as an archive of fracture modes. The photographic system of the SEr4 displays information directly across the bottom of each SEM photograph.

Referring, for example, to

Figure 62, the caption reads:

25 KV XlOOO 1131 1O.OU UW85 The interpretation is as follows:

25 KV

electron beam accelerating voltage, in kilovolts

XlOOO

magnification

1131

photograph number

10 .OU

length of scale bar, in microns

UW85

the SEN unit identification number, i.e., University of Wyoming and the current year, 1985

The

specimen

convenience.

system

is

summarized here

for

A typical specimen identification is divided into three

sets of characters. AFRY06.

numbering

For example, the specimen number in Figure 62 is

This is interpreted as follows:

A

'identifies the program, for NASA-Ames, related to the graphite fiber/polymer matrix interface study

FRY

identifies the type of specimen, environmental condition, and polymer matrix, as defined below

06

identifies the fiber surface treatment and specimen number

The complete set of codes, Table 22.

for all specimens tested, is presented in

It

should

be

s p e c i n e n from which associate the tabulated

in

noted

tnat,

by i d e n t i f y i n g t h e p a r t i c u l a r t e s t

t h e SEN p h o t o g r a p h was t a k e n ,

s p e c i f i c mechanical Appendix

c h a r a c t e r i s t i c s observed.

A,

with

p r o p e r t i e s of the

specific

it is possible t o

t h a t specimen, fracture

as

surface

Table 22 Test Specimen Identification Code Specimen No. a. b -.

"I -

Ames

-

Neat Resin Tension

- Neat Resin Iosipescu Shear

-

Neat Resin Thermal Expansion

-

Neat Resin Moisture Expansion

-

Fiber Pullout

-

Transverse Tension

-

Axial Compression

-

Laminate Compression

- Laminate Tension

-

Laminate Flexure

-

Interlaminar Shear

-

Instrumented Tensile Impact

-

Room Temperature, Dry

-

Elevated Temperature, Wet

- Hexcel F155 Epoxy

-

Hercules 3501-6 Epoxy

- Hercules 4001 Bismaleimide

-

Unsized

- EPON 828 sizing

-

PVA sizing

- Polysulfone sizing -145-

F'igure 62.

Unsized AS4/Hercules 3501-6 Unidirectional Composite, Transverse Tensile Specimen ARFY06, 23OC, Dry Condition.

Good adhesion of the matrix to the graphite fibers, along with a normal hackle pattern i n - t h e matrix caused by the tensile failure, is indicated.

OR4GWAL PAGE

OF.POOR

Figure 63.

QUALBV

EPON 828-Sized AS4/Hercules 3501-6 Unidirectional Composite, Transverse Tensile Specimen AFRY10, 23"C, Dry Condition.

Good matrix adhesion to the graphite fibers, and a normal matrix hackle pattern caused by the tensile failure is indicated.

Figure 64.

PVA-Sized A S 4 / H e r c u l e s 3501-6 U n i d i r e c t i o n a l C o m p o s i t e , T r a n s v e r s e T e n s i l e Specimen AFRY26, 23"C, Dry C o n d i t i o n .

L i m i t e d f i b e r l m a t r i x a d h e s i o n and somewhat more d i s r u p t i o n of t h e c o m p o s i t e from t h e t e n s i l e f a i l u r e t h a n s e e n i n F i g u r e s 6 2 and 6 3

w i l l be n o t e d .

0R.868NAL PAGE "\s'> OF POOR QUALITY

Figure 65.

Polysulfone-Sized AS4/Hercules 3501-6 Unidirectional Composite, Transverse Tensile Specimen AFRY33, 23"C, Dry Condition.

oder rate fiber-matrix adhesion and some bulk composite disruption is indicated.

F i g u r e 66.

Unsized AS4/Hercules 3501-6 U n i d i r e c t i o n a l C o m p o s i t e , T r a n s v e r s e T e n s i l e Specimen APEY04, 100°C, M o i s t u r e Conditioned.

Some minor d e b r i s from t h e f a i l u r e c a n be s e e n , a l o n g w i t h b a r e f i b e r s , empty f i b e r t r o u g h s , and a h a c k l e d r e s i n s u r f a c e c a u s e d by the t e n s i l e f a i l u r e .

Figure 67.

EPON 828-Sized A S 4 / ~ e r c u l e s3501-6 Unidirectional Composite, rransverse Tensile Specimen A F E Y 1 2 , 100°C, ~oisture-Conditioned.

Many empty fiber troughs, bare fibers, and the hackled matrix surface caused by the tensile failure will be noted.

Figure 68.

PVA-Sized AS41Hercules 3501-6 Unidirectional Composite, Transverse Tensile Specimen A F E Y Z ~ , 100°C, Aoisture-Conditioned.

Bare fibers and a somewhat coarser hackle pattern in the matrix t h a n s e e n in Figure 6 7 are evident.

F i g u r e 69.

Polysulfone-Sized AS4/Hercules 3501-6 Unidirectional Composite, Transverse Tensile Specimen AFEY35, 10O0C, Moisture-Conditioned. A

Bare fibers and a very coarse hackle pattern in the matrix are obvious.

Figure 70.

Unsized ~ S 4 / H e r c u l e s 4001 Unidirectional Composite, Transverse Tensile Specimen AFRZ04, 2 3 " C , Dry Condition.

Limited fiber-matrix interface bonding is indicated.

Figure 71.

EPON 828-Sized ASb/Hercules 4001 Unidirectional Composite, Transverse Tensile Specimen AFRZl7, 2 3 " C , Dry Condition.

Bare fibers, but s h e signs of fiber-matrix interface.adhesion, are evident.

Figure 72.

PVA-Sized AS4/Hercules 4001 Unidirectional Composite, rransverse Tensile Specimen AFRZ23, 23"C, Dry Condition.

Bare fibers and locations of fiber pullouts can be seen.

ST

Z L pue

' O L s a z n % r ~ u~ uhoqs saser, juam2eal2 asejlns xaqgo aq2

F i g u r e 74.

U n s i z e d A S 4 / H e r c u l e s 4001 U n i d i r e c t i o n a l C o m p o s i t e , T r a n s v e r s e T e n s i l e Specimen AFEZ02, 100°C, M o i s t u r e Conditioned.

Bare f i b e r s and f i b e r t r o u g h s , and a rough h a c k l e d a p p e a r a n c e o f the m a t r i x , a r e dominant f e a t u r e s of t h i s f r a c t u r e s u r f a c e .

-3uapyna a l e ' 9 ~

u l a 2 3 e d l a u r g B q 2 y ~c ~ q 2 1 n laqT3 ~ l ~ d ~ d m a duom pue s l a q T 3 a l e g

Figure 76.

PVA-Sized A S 4 / ~ e r c u l e s 4001 Unidirectional Composite, Transverse Tensile Specimen AFEZ21, 10O0C, MoistureConditioned.

A fiber with some resin still adhering to it, indicating better adhesion, and also some porosity in the matrix, c a n be seen in this photograph.

8R4GfNAQ PAGE W o~,POOR quAkam

Figure 77.

Polysulfone-Sized AS41Hercules 4001 Unidirectional Composite, Transverse Tensile Specimen AFEZ34, 100°C, ~oisture-Conditioned.

Fibers with some matrix material still adhering to them, indicating moderate interface bonding between the fibers and the surrounding matrix, are shown. evident.

Porosity in the matrix is also

F i g u r e 78.

U n s i z e d AS41Hexcel F155 U n i d i r e c t i o n a l C o m p o s i t e , T r a n s v e r s e T e n s i l e Specimen AFRXO1, 23"C, Dry Condition.

Some b r o k e n f i b e r s and a v e r y c o a r s e r e g i o n o f f a i l e d m a t r i x a r e shown.

The r e l a t i v e l y c l e a n f i b e r s u r f a c e s i n d i c a t e i m p e r f e c t

fiber-matrix

i n t e r f a c e bonding.

.ORIGINAL PAGE BS QJ dPOOR QBBABBm

Figure 79.

EPON 828-Sized ~ ~ 4 / H e x c eEll 5 5 Unidirectional Composite, Transverse Tensile Specimen A F R X 1 0 , 23"C, Dry Condition.

Some bare fibers and a somewhat less coarse matrix failure surface t h a n seen in Figure 78 are evident.

,

Figure 80.

PVA-Sized ASO/Hexcel E l 5 5 Unidirectional Composite, Transverse Tensile Specimen AFRX26, 2 3 O C , Dry Condition.

Some broken fibers and moderate fiber/matrix adhesion will be noted.

ORIQ3NAL PAGE 1%

05

Figure 81.

BOOR QUALI*

Polysulfone-Sized AS41Hexcel F155 Unidirectional Composite, Transverse Tensile Specimen AFRX33, 23"C, Dry Condition.

Better fiberlmatrix adhesion in the center of the photograph, where a fiber has pulled some matrix away, is indicated.

Figure 82.

Unsized AS4/Hexcel F155 Unidirectional Composite, Transverse Tensile Specimen AFEXOO, 3d°C, MoistureConditioned.

Some indications of interface breakdown and exposed fibers can be seen.

Figure 83.

EPON 828-Sized ASOIHexcel E l 5 5 Unidirectional Composite, Transverse Tensile Specimen AFEX13, 3a°C, Moisture-Conditioned.

Some indication of reasonable fiber/matrix adhesion is evidenced b y the matrix still adhering to the otherwise bare fibers.

Figure 84.

PVA-Sized AS4/Hexcel F155 Unidirectional Composite, Transverse Tensile Specimen AFEX21, 3 8 " C , ?ioistureConditioned.

Matrix ductility is quite evident in the center of the photograph, with some bare fibers also seen.

Figure 85.

Polysulfone-Sized AS4IHexcel F155 Unidirectional Composite, rransverse Tensile Specimen A F E X 3 3 , 38"C, Hoisture-Conditioned.

Bare fibers and other indications of inadequate interface bonding c a n be seen.

Figure 86.

Unsized AS4/Hercules 3501-6 Unidirectional Composite, Axial Compression Specimen AGRY05, 23OC, Dry Condition.

Little indication of fiber buckling, but major longitudinal splitting and gross shear failure, is shown.

ORiGJGbMAL PAGE IS POOR QUALITY

Figure 87.

dPON 828-Sized A ~ 4 / H e r c u l e s 3501-6 Unidirectional Composite, Axial Compression Specimen AGRY17, 23"C, Dry Condition.

No evidence of fiber microbuckling, but some longitudinal splitting and gross shear failure, is indicated.

r r

Hl

t-r

.

o

H 3

Q

m

.

3

0'4

C 1 ID

m

CI)

-

r.

0

0 0 V, LrJ

m

.r C 1 (D

7

o

n

0 00 1 Pl

rn

m--r. 2 o m 3

1

n

cnc m w m m ntn

r.

B W m u 3

0 C

7

P I 0 (3'.

3 0

zc

2

-

P

N 3 N

r.

a

rN rl

r

3

w m

0

.'-t




b) EPON 828 sized

a) unsized

DRY,

c) PVA sized

Figure 113.

828

PVA SIZED

e

e

STRAIN

R T

DRY,

R .T

R.T

DRY, POLYSULFON SIZED

d) polysulfone sized AS4/3501-6 Unidirectional Composite, Room Temperature, Dry Condition, Transverse Tensile Loading. Correlations Between Predictions and Experimental Data for All Four Fiber Sizings, Using a ?laximum Normal Stress Failure Criterion.

I S

upon

the

individual measured

values

attempt to model each specific value. experimental

data

did

variations

in

fiber

analytical

results

not

degradation

of

the

around

the

interface can

simply

reducing the

simulated

Thus, to

be

be

a

Figure

75

only

25

percent

The

strength

finite elements

assigned any properties desired.

properties, a in

in Figure 113 are the

interface.

strength properties

corresponding matrix simulated.

plotted

assuming

fiber-matrix

6 , rather than to

a strong sensitivity to these

Also

predicted

Table

As discussed in Section 4 , the

indicate

volume.

of

as some

percentage of the

degraded interface

113,

the

percent

By

bond can

be

interface bond strength is

of the strength of the Hercules

3501-6 epoxy matrix itself. As

can

predicted

be

the

seen

in

initial

Figure

113,

the finite element analysis

stiffnesses of

particularly considering

all

four

that n o attempt was

composites well,

made to

simulate the

I

exact fiber volume variations.

The predicted composite stress-strain

curve for the perfect interface extends to 47 MPa (6.8 ksi). applied no

stress level, only limited matrix yielding had occurred, and

matrix

twice

At that

cracking.

Since

this

applied stress was already about

that actually measured, this

assuming a ultimate

25 percent strength was

computer run was terminated.

interface strength reduced

reduction, the

drastically.

Complete

By

predicted composite

fracture was predicted at the 31 MPa (4.5 ksi) stress level indicated in

Figure

113.

experimentally conditions. As

This

measured

value

is

in

strengths

reasonable agreement with the for

discussed in Section 4 , it

that the EPON 828

all

four

fiber

sizing

might have been expected

and polysulfone sizings would have resulted in the

t e n s i l e s t r e n g t h s , and t h e PVA s i z i n g t h e l o w e s t .

highest transverse As

can

rhus, fit

be

seen

in

Figure

no a t t e m p t was the

individual

113, a l m o s t t h e o p p o s i t e was o b s e r v e d .

made t o f u r t h e r experimental

refine the analysis t o better

data.

I n g e n e r a l , t h e agreement

i n d i c a t e d i n F i g u r e 113 i s good. Examples of t h e i n t e r n a l s t r e s s s t a t e s , e x t e n t crack

patterns

are

included

in

Figure

of y i e l d i n g , and R e s u l t s f o r t h e 25

114.

p e r c e n t i n t e r f a c e s t r e n g t h d e g r a d a t i o n a r e shown. f o r each loading increment, f o r components p r e s e n t e d i n

i s , only four here,

Of c o u r s e , r e s u l t s

e a c h of t h e e i g h t s t r e s s

F i g u r e 1 1 2 , were a v a i l a b l e

of t h e s e v e r a l

for study.

hundred p l o t s a v a i l a b l e

a l t h o u g h many dozens o f

and s t r a i n That

.are presented

o t h e r s were a c t u a l l y s t u d i e d .

Figure

114a shows t h a t t h e maximum normal s t r e s s ( t h e c r i t e r i o n f o r f a i l u r e ) occurred near the

i n t e r f a c e along the x a x i s .

However, t h e maximum

octahedral shear s t r e s s ( t h e c r i t e r i o n for yield) y axis, as t h e same l e v e l , of rapidly.

region (Figure applied The

F i g u r e 114c. predicted and

1 1 4 ~ ) . This

stress

e x t e n t of

Thus, f i r s t

(less

yielding initiated

than

yielding a t

y i e l d i n g occurred i n

14

at a

low

MPa), b u t d i d n o t s p r e a d

28 MPa

(4.0 k s i )

i s shown i n

A s p r e v i o u s l y i n d i c a t e d i n F i g u r e 1 1 3 , f u l l f a i l u r e was

a t 31 i ' a

(4.5 k s i ) .

The

e x t e n t of y i e l d i n g a t f a i l u r e ,

t h e c r a c k p a t t e r n r e s u l t i n g i n t h i s f a i l u r e , a r e shown i n F i g u r e

114d. the

114b.

shown i n F i g u r e

occurred along t h e

As c a n b e s e e n , t h e m i c r o c r a c k i n g f o l l o w e d t h e i n t e r f a c e up t o y i e l d zone, and t h e n

a c r o s s t h e t h i n web

of y i e l d e d m a t r i x , t o

r e s u l t i n a t o t a l fracture path. As

criterion

noted was

previously,

an

also

Since

tried.

octahedral the

shear

stiffness

stress

failure

properties

were

--

d+-aww C m 4-119 -119 B 30119 r $71119

-

m*bCTr=w W I =Pa -8

-c -

=-

W-

w

r ~ (

-119 5

~

3-119

PDL1 D

o

H

-- 4 v m - eplm

WIQ I~~ I Q

w. -- 4-119 -

RLnm

I1

3s-

A

L

I

331ra

a) maximum principal stress

m1-07 1 ~ 1 ~ TEN.. 8. aJ

*-

MW-

w -

wn .wm

-m.

m-

SP WUI I - tar9

r

earn

-a .wm

-w m

--lC

uue

m

mneum/R

c) extent of yielding Figure 114.

-

C -

ISIIQ

o

Z

-

W

-

D ~ti

-m w m

-

RLnm

w.

-

.

-a m

I ~ R Z

5am

A

~ m r s

c - ~ w r s I tern

ram

-

EDaC--m

-

ap-n.wm c 9 +.am 50-

ram-=

=-

-

=1-8m.m,axmwmm

mm. w $12-

-341-mmm m- w n -KI sn wrs tm am PDL

b) octahedral shear stress

IM.

massn-w m-n.wm.c 4.wm SQ.wrs

-

u-Clwm C w 4wm

riCl

m- . w r 5n w m

-

m 91

-

-a .wm

m

m w . - sr 30

-

m u

WIQ

mass

d) crack pattern at failure

A S 4 1 3 5 0 1 - 6 Unidirectional Composite, Room Temperature, Dry Condition, Transverse rensile Loading. Internal Stress States for the 25 Percent Degraded Interface Model, Using a Maximum Normal Stress Failure Criterion.

unchanged,

the

composite

c r a c k i n g were t h e normal

stress-strain

same a s t h o s e shown i n F i g u r e

stress failure criterion.

adequately

predicted.

microcracking

had

yet

However,

assuming

occurred

at

103

not yet f u l l y yielded.

a

up t o f i r s t micro113 f o r t h e maximum

That i s , t h e

s t r e s s l e v e l a t which t h e computer r u n m a t r i x was

curves

s t i f f n e s s was a g a i n p e r f e c t i n t e r f a c e , no

i4Pa ( 1 5 k s i ) , t h e a p p l i e d

was t e r m i n a t e d .

The e x t e n t

In f a c t , the

of y i e l d i n g a t 34 MPa

( 5 . 0 k s i ) and a t 86 t4Pa ( 1 2 . 5 k s i ) a r e

i n d i c a t e d i n F i g u r e s 115a and

115b,

percent interface degradation

respectively.

resulted

in

early

1 1 5 ~ 1 ,b u t s t i l l which

(2 ksi)

,

the

a at

no f a i l u r e a t

the fiber-matrix interface (Figure 69 ;*a

k s i ) applied s t r e s s ,

terminated.

A t 14 MPa

HPa ( 1 0 k s i ) and

The e x t e n t of y i e l d i n g It

t o t h e almost

shown i n F i g u r e 1 1 5 c .

y e t i n i t i a t e d a t 69

F i g u r e 115d.

at

A s i m i l a r r e s u l t was

y i e l d e d , a s opposed

50 p e r c e n t d e g r a d a t i o n

a g a i n no f a i l u r e had

i s shown i n

(10

r u n was t e r m i n a t e d .

i n t e r f a c e was f u l l y

t h e a n a l y s i s was

50

percent i n t e r f a c e strength degradation.

yielding for the

However,

ksi)

yielding

p o i n t t h e computer

o b t a i n e d f o r a 75

full

Assuming

was t h e same

a t 45 PiPa ( 6 . 5

f o r t h e 50 p e r c e n t

degradation case. The c o n c l u s i o n must criterion

is

not

be t h a t t h e o c t a h e d r a l s h e a r s t r e s s f a i l u r e

applicable

to

t r a n s v e r s e t e n s i l e l o a d i n g of t h e

~ 5 4 / 3 5 0 1 - 6 u n i d i r e c t i o n a l composite. normal s t r e s s

failure criterion

On t h e o t h e r h a n d ,

worked q u i t e

t h e maximum

w e l l , a s demonstrated

here. 6.4.3.2 The

E l e v a t e d T e m p e r a t u r e , Wet (93OC, 1 % ~ )

experimentally

stress-strain

curves

determined are

plotted

individual in

Figure

transverse 116,

for

tensile the

four

O R e M A L PAGE '1%.

-----

OF POOR QUALITY

9 8 1 6

- emu

m.lB4..

-

dC-Omm.C

A-

m

sn

DU

DI

--rC

s

-

WW.-

-19.-=

m u

W

-

M.

.wm

sa

----

39616 T W 6 . TPI..

a

dC-mDm.C

m-

ma

~ - B . W W

SW-

m-

-neema

w

a) yielding at 34 MPa

.bl

.wm

m

r

s-

O

DJT. -S

RLXKI.'

*

n l ~ s - .-a

.bm Ual!

mumum

m

an

b) yielding at 86 MPa

m1-e m.TEN, 5B# CElffLCa) m .

c) 50% interface degradation, yielding at 14 MPa Figure 115.

AS4/3501-6 Unidirectional Dry.Condition, Transverse Yielding as a Function of Using an Octahedral Shear

d) 75% interface degradation, yielding at 45 MPa Composite, Room Temperature, Tensile Loading. Extent of Amount of Interface Degradation, Stress Failure Criterion.

different fiber sizings.

6 h a v e been p l o t t e d

i n t h i s Section making

comparisons.

micromechanics for

both

a

I t w i l l be n o t e d t h a t a l l r e s u l t s p r e s e n t e d

Also

t o t h e same s c a l e ,

shown

in

analysis predictions perfect

interface

Figure

of t h e

and

25

116

for ease i n

are

the

WY02D

s t r e s s - s t r a i n response,

percent

degradation.

The

immediate c o n c l u s i o n might be t h a t t h e ETW m a t r i x modulus u s e d i n t h e a n a l y s i s was low

n o t h i g h enough.

composite

stiffness

This i s not

is

due

to

predicted a t

f a i l u r e occurred the

at slightly

However, t h e

l e s s than

a t 23 MPa ( 3 . 4 k s i ) .

experimentally

measured

i n t e r f a c e by 25 p e r c e n t r e d u c e d

The f i r s t m i c r o c r a c k i n g

4 MPa

( 0 . 5 k s i ) , and f u l l

T h i s p r e d i c t i o n was c l o s e t o

strengths

predicted s t r a i n s

The

the extensive matrix cracking

p r e d i c t e d a t v e r y low a p p l i e d s t r e s s l e v e l s . was

t h e c a s e , however.

were much

plotted

in

too high.

Figure

116.

Degrading t h e

t h e f a i l u r e s t r a i n s , by r e d u c i n g t h e

f a i l u r e s t r e s s , b u t r e d u c e d t h e c o m p o s i t e modulus

even f u r t h e r below

the experimental values. Corresponding ln

shown

Figure

p a t t e r n , which perfect ksi).

cracking

117.

patterns

Figure

did follow the

interface case,

117a

at

selected

load l e v e l s a r e

indicates the predicted crack

f i b e r - m a t r i x i n t e r f a c e even

a t an

applied s t r e s s

for this

l e v e l of 17 MPa ( 2 . 4

With

increased loading, the crack

then propagated.across the

t h i n web of

m a t r i x m a t e r i a l a t the y-axis

leading t o t o t a l fracture

a t 23 14Pa ( 3 . 4 k s i ) , a s i n d i c a t e d i n F i g u r e 1 1 6 . men predicted

t h e i n t e r f a c e was to

temperature, F i g u r e 117b.

partially prior

to

fail any

A t o n l y 3.5 MPa

degraded 25 p e r c e n t , during

heat-up

mechanical (0.5 k s i )

to

loading.

t h e i n t e r f a c e was the

93°C

test

T h i s i s shown i n

applied loading, the crack

93 MG

43 OE6. C . , 1 % M, WSIZD

0

t3

8.8

8 5

1 0

S l R m 6ERCENT)

93 DEG C . , 1 % M,

Figure 116.

82B SIZED

0

0 0 63

0 S

1 .@

1 .S

STRAIN BERCENT)

b ) EPON 828 sized

a) unsized

c) PVA sized

I S

C , I K M,

PVA SIZED

93 DEG. C , I % H.

FUYSJLFONE SIZED

d) polysulfone sized AS413501-6 Unidirectional Composite, Elevated Temperature, Wet Condition ( 9 3 " C , 1% M), Transverse Tensile Loading. Correlations Between Predictions and Experimental Data for All Four Fiber Sizings, Using a Maximum Normal Stress Failure Criterion.

a) yielding at 17 MFa

b) 25% interface degradation, yielding prior to loading 33al-6 W . TEN.. ZS X CEIAPCED M

m~~~~ E9-S3Wm.C 9

c)

25% interface degradation, yielding at 3.5 MPa

Figure 1 1 7 .

-

2-m

m-

m

-

2-S

m

P

-

O

51OtaI -U8m'l3rcC

'U'UE

fmmBbbmR

L u

P

-

m

--

U -.*

FWTM

m

51L

R

W -IQ

m

d) 25% interface degradation, yielding at 14 MPa

AS413501-6 Unidirectional Composite, Elevated Temperature, Wet Condition ( 9 3 " C , 1% M ) , Transverse Tensile Loading. Extent of Interface and hatrix Cracking, Based Upon a Maximum Normal Stress Failure Criterion.

had s p r e a d extended

as indicated completely

f r a c t u r e then produced t h e appears

i n Figure

around

the

117c. interface

16 [@a

occurred a t

(Figure

(2.3 k s i ) .

low composite modulus

( 2 . 0 k s i ) , it

14 MPa

At

117d).

This e a r l y

and h i g h s t r a i n

Total cracking

to failure.

It

t e n s i l e s t r e n g t h f o r t h i s ETW

t h a t modeling a h i g h e r m a t r i x

c o n d i t i o n would have produced b e t t e r agreement w i t h

the experimental

data. Using

an o c t a h e d r a l shear s t r e s s

no m a t r i x model,

PlPa (10 k s i ) f o r

c r a c k i n g up t o 69

a t which

failure criterion resulted in

point the

a n a l y s i s was

the perfect interface

terminated.

Degrading t h e

i n t e r f a c e 50 p e r c e n t s t i l l r e s u l t e d i n no m a t r i x o r i n t e r f a c e f a i l u r e up t o

69 PlPa (10 k s i ) .

i n good

However, t h e p r e d i c t e d composite modulus was

agreement w i t h t h e

measured v a l u e s .

t h e s t a t e m e n t made e a r l i e r t h a t when

using

the

maximum

This

further supports

i t was t h e e x t e n s i v e m a t r i x c r a c k i n g

normal

stress

criterion

t h a t caused t h e

a p p a r e n t low c o m p o s i t e modulus i n d i c a t e d i n F i g u r e 1 1 6 . A s u i t a b l e f a i l u r e c r i t e r i o n a p p e a r s t o be one somewhere between

t h e two c o n s i d e r e d h e r e . 6.5

AS4/4001 C o r r e l a t i o n s The

Hercules

temperature

than

r a t h e r t h a n 177°C the

AS4/4001

stresses

in

4001 the

bismaleimide Hercules

(350°F).

composite. this

matrix

3501-6

was c u r e d a t a h i g h e r

epoxy,

T h i s was t a k e n i n t o Yet,

composite

as

were

i.e.,

204°C (400°F)

a c c o u n t i n modeling

w i l l be shown, t h e h y g r o t h e r m a l actually

lower

than

for

the

A6413501-6 c o m p o s i t e , due t o t h e i n f l u e n c e of o t h e r f a c t o r s . 6.5.1

Thermal R e s i d u a l S t r e s s e s As i n d i c a t e d i n T a b l e 3 o f S e c t i o n 4 ,

t h e s h e a r s t r e n g t h of t h e

Hercules 4001 at the RTD condition was measured to be quite low, viz, 17 MPa (2.4 low.

ksi).

Thus, the shear yield

These low values

may have been associated with the

Iosipescu shear test method on as discussed in Section 3. were

used

yielding (400°F)

in of

the the

matrix

cure temperature.

failure

criterion was

analysis.

material

the actual measured values This

during

This did

resulted

cooldown

in complete

from the 204°C

not significantly influence the

loading, however, used.

use of the

this relatively brittle resin system,

Nevertheless,

present

subsequent mechanical

stress was correspondingly

if a maximum normal stress

The measured tensile

strength of the

Hercules 4001 bismaleimide matrix was 53 MPa (7.7 ksi),

i.e., over

three times its shear strength. 6.5.2

floisture-Induced Stresses As

fully

noted yielded

addition

in

the

during

of one

previous

subsection, the matrix had already

cooldown after

weight percent

curing

moisture to

the

composite.

The

the ~ ~ 4 / 4 0 0composite 1

(corresponding to 2.72 M in the matrix itself, the matrix saturation level being 7.0% ~ 4 ) resulted in a net interface normal hygrothermal residual stress of almost exactly zero. stress

induced

cooldown-induced

by

moisture

That is, the tensile

absorption almost

compressive normal

stress

normal

exactly offset the

at the interface.

All

other stress components were also very low, of course. Heating the moisture-conditioned composite up to the 93°C (200°F) ETW test temperature increased the interface normal stress to coefficient of thermal expansion (Table 4) and a lower coefficient of moisture expansion (Table 5).

The present predictions demonstrate

the power of the micromechanics analysis to quantify the influences of

such v a r i a b l e s . Because of t h e s e r e l a t i v e l y low h y g r o t h e r m a l s t r e s s e s , no m a t r i x c r a c k i n g was p r e d i c t e d , even f o r a 25 p e r c e n t degraded i n t e r f a c e . 6.5.3

T r a n s v e r s e T e n s i l e Loading

6.5.3.1

Room T e m p e r a t u r e , Dry

The p r e d i c t e d s t r e s s - s t r a i n c u r v e s , assuming a maximum normal s t r e s s f a i l u r e c r i t e r i o n , a r e presented i n Figure 118, along with t h e i n d i v i d u a l s t r e s s - s t r a i n curves f o r a l l four f i b e r s i z i n g composites. The p e r f e c t i n t e r f a c e r e s u l t s c o r r e l a t e d v e r y w e l l w i t h t h e experimental data, tending t o s l i g h t l y underpredict ultimate s t r e n g t h s and m o d u l i e x c e p t f o r t h e PVA-sized

f i b e r composite.

The

u n d e r p r e d i c t i o n of moduli was a g a i n u n d o u b t e d l y due t o s l i g h t l y p r e m a t u r e m a t r i x c r a c k i n g , a s s o c i a t e d w i t h t h e maximum normal s t r e s s f a i l u r e c r i t e r i o n used.

The PVA-sized

f i b e r s would be e x p e c t e d t o

r e s u l t i n t h e p o o r e s t i n t e r f a c e bonding, and h e n c e , t h e e a r l i e s t matrix cracking.

A s s e e n i n F i g u r e 118, t h e s t r e n g t h s of t h e s e

specimens were t h e l o w e s t . For t h e p e r f e c t i n t e r f a c e bond, no m a t r i x c r a c k i n g was p r e d i c t e d up t o a l m o s t

38 MPa ( 5 . 5 k s i ) . 45'

t h e i n t e r f a c e , a t about

However, a c r a c k t h e n

from t h e l o a d i n g a x i s

( t h e x-axis),

s p r e a d r a p i d l y i n b o t h d i r e c t i o n s , c a u s i n g immediate MPa ( 1 . 3 more

ksi), still

favorable

AS4/3501-6

a relatively

residual

composite

stress

discussed

low l e v e l . state

in

failure.

and

The 9

The r e a s o n f o r t h i s

relative

Section

initiated a t

to

6.4.2,

that was

in a

the

higher

r e s u l t a n t f r a c t u r e i s shown i n F i g u r e 119a. Assuming

a

25

percent

i n t e r f a c e d e g r a d a t i o n caused i n t e r f a c e

c r a c k i n g t o o c c u r a t o n l y 3 . 5 MPa ( 0 . 5 k s i ) , a s shown i n F i g u r e 119b.

ORIGINAL PAGE "E OF. POOR QUALITY R T . DRY,

0.0

0 5

USSIZED

10

R T . DRY,

15

828 SIZED

0 5

0 0

1 0

STRAIN m>

SlRAIN BERCPIT>

1 5

b) EPON 828 sized

a) unsized

R . T . DRY,

R T

PVA SIZED

75

DRY,

POLYSULFOlY

SIZED

75 1e

10

c) PVA sized Figure 118.

d) polysulfone sized AS4/4001 Unidirectional Composite, Room Temperature, Dry Condition, rransverse Tensile Loading. Correlations Between Predictions and Experimental Data for All Four Fiber Sizings, Using a Maximum Normal Stress Failure Criterion.

OWIG&NAL PAGE

8s

OF W X l R QkPAhOm, -aDea--

=-

m-bWm.C

mm7

-

s- w m

WS

wrm

-w sr

-

-3l

.wrm

m w . -s

U - W W m

so

SrSO-

-

wrm

w m -aBemR rmmme4uR

P . F ZP r -

m-warm x -

- ism

SQ-

M

w m

t

13-

m -

m m

m

-

-

m . .?5%EFXD,?TT

7RAUj

ear earn

:ze5.7:3

z-

-a

%Kzt

?s;m 7-2

-

-1

-

c ) i n t e r f a c e normal s t r e s s , p r i o r t o l o a d i n g , RTD F i g u r e 119.

m -

.WY w m

-HI

91-

-W

wrm

FunM 50-

-

W

w m

aw

-nue.uR

VuE UQC

TFN-6

TEN. 5 % CEFWED TST

mcraYr-m 7

3 5

se-wwrmc a -1 w m W -

2.nw

IQD-

b ) 25% i n t e r f a c e d e g r a d a t i o n , y i e l d i n g a t 3.5 MPa

a ) crack pattern a t f a i l u r e -1

massn-aw C

WIQ

tam-

m -

WY

w m

.m=crrro 92-

-a eam

mto 511-

-w w m

WIQ

-aBe.wR

m

d ) 25% i n t e r f a c e d e g r a d a t i o n , y i e l d i n g a t 7 MPa

AS4/4001 U n i d i r e c t i o n a l Composite, Room T e m p e r a t u r e , Dry C o n d i t i o n , T r a n s v e r s e T e n s i l e Loading. E x t e n t o f I n t e r f a c e and M a t r i x C r a c k i n g , Based'Upon a Maximum Normal S t r e s s F a i l u r e C r i t e r i o n .

As f o r t h e p e r f e c t i n t e r f a c e c a s e , debonding o c c u r r e d f i r s t . a t 45" t o the loading stress

a x i s b e c a u s e of t h e

a t the

very f a v o r a b l e compressive r e s i d u a l

i n t e r f a c e along

the x

s t r e s s s t a t e i s shown i n F i g u r e 1 1 9 c .

and y a x e s . This

This preexisting

i n t e r f a c e debond q u i c k l y

s p r e a d t o t h e x a x i s , and t h e n p r o p a g a t e d up

i n t o the bulk matrix a t

6 . 9 MPa ( 1 . 0 k s i ) , a s

Full

at

shown i n F i g u r e 119d.

1.1 k

7.6 MPa

s

as indicated

by t h e

f r a c t u r e occurred

s t r e s s - s t r a i n c u r v e of

Figure 118. These

r e s u l t s suggest t h a t

~ S 4 / 4 0 0 1 composites

was

not

t h e i n t e r f a c e bond degraded

for the various

significantly

at

the

RTD

condition. Use

of

the

extensive matrix composite

octahedral

c r a c k i n g a t low

moduli

which

strains to failure. measured

shear

shear

were

failure

criterion

resulted i n

applied s t r e s s l e v e l s ,

too

and h e n c e ,

low, combined w i t h h i g h a p p a r e n t

As p r e v i o u s l y d i s c u s s e d , t h i s was due t o t h e low

strength

temperature.

Use

of

undoubtedly

resulted

of

the

Hercules

4001

matrix

a

more

typical

shear

strength

in

good

modulus

predictions,

at

room

would h a v e

but composite

s t r e n g t h s which were much t o o h i g h . 6.5.3.2

E l e v a t e d T e m p e r a t u r e , Wet

The

ETW

predicted

transverse

tensile

loading

stress-strain

c u r v e s a r e shown i n F i g u r e 1 2 0 , f o r b o t h a p e r f e c t i n t e r f a c e and a 25 percent degraded i n t e r f a c e , criterion. treatments are perfect

The

assuming a maximum normal s t r e s s f a i l u r e

experimental

also plotted.

interface

resulted

data As c a n

in

good

for

the

be s e e n , general

four

fiber

surface

t h e assumption of a agreement

with

the

n o n l i n e a r i t y of t h e experimentally determined s t r e s s - s t r a i n response.

93 DE6. C . , IX

0.0

0.5

93 DEG. C , IX H ,

INSRED

H,

I

a

1 5

a

e

B

STRAP4 @ERxNT)

1 5

b) EPON 828 sized

93 DEG. C , I X M,

B 5

S

c)

1 8

STRAIN (PERCDJT)

a) unsized

0 0

5

820 SIZED

PVA sized

Figure 120.

W

->

PVA

1 0

SIZED

93 DEG

1 5

8 0

C

, I X M,

8 5

FUYSULFONE SIZED

18

1 5

STRAIN BERIM)

d ) polysulfone sized ~ S 4 / 4 0 0 1Unidirectional Composite, Elevated Temperature, Wet Condition (93"C, 1% M ) , Transverse Tensile Loading. Correlations Between Predictions and Experimental Data for A11 Four Fiber Sizings, Using a daxirnurn Normal Stress Failure Criterion.

The of

p r e d i c t e d s t r e n g t h s were s l i g h t l y the

allowable

adjust

matrix

this difference.

strain

high, although closer control

a t assumed f a i l u r e would p r o b a b l y

The a s s u m p t i o n

of a

25 p e r c e n t i n t e r f a c e

d e g r a d a t i o n was o b v i o u s l y t o o s e v e r e , a s i n d i c a t e d i n F i g u r e 120. The f a i l u r e mode p r e d i c t e d assuming a p e r f e c t i n t e r f a c e i s shown i n F i g u r e 121a. the

The

interf ace.

AS4/3501-6 which

f r a c t u r e i s i n t h e bulk m a t r i x ,

This

composite

was

is

quite

a t the

primarily

an

unlike

same ETW

interface

that

r a t h e r than a t

predicted

condition (see failure.

The

for

the

Figure 117a), reason for t h i s

distinct difference i s related to

t h e d i f f e r e n c e s i n c o e f f i c i e n t s of

thermal

expansion

expansion

materials, normal

as

and

already

hygrothermal

t e n s i l e , were

moisture discussed

stresses

much lower

in

prior

for the

between

t h e two m a t r i x

Section 6.5.2. to

loading,

The i n t e r f a c e although

AS4/4001 composite.

still

This s t r e s s

d i s t r i b u t i o n i s shown i n F i g u r e 121b. Degrading t h e i n t e r f a c e s t r e n g t h

by 25 p e r c e n t was

however, t o s h i f t t h e f a i l u r e back t o t h e i n t e r f a c e , a s F i g u r e s 121c loading,

and.-12ld.

accounting

for

i n d i c a t e d i n F i g u r e 120. That

F i r s t cracking a l s o the

reduced

indicated i n

occurred e a r l i e r i n the

apparent

composite

Likewise, t o t a l f r a c t u r e occurred

i s , t h e p r e d i c t e d composite

than 1 7

sufficient,

MPa ( 2 . 5 k s i ) , whereas

modulus earlier.

s t r e n g t h was o n l y s l i g h t l y g r e a t e r for the perfect interface

i t was 32

MPa ( 4 . 6 k s i ) .

As for the sizing variations

RTD

condition,

a p p e a r e d t o be

the

composites i n c o r p o r a t i n g

did

not

appear

to

be

degradation minimal.

the Hercules

degraded

by

the

effects

Also, t h e

due t o

fiber

i n t e r f a c e s of

4001 b i s m a l e i m i d e m a t r i x e l e v a t e d t e m p e r a t u r e and

OWIWNAL PAGE 1% OF POOR QUALOm

a) crack pattern at failure -1

M. TEN., 25 X CaffPDED 1M

c) 25% interface degradation, cracking at 1 4 MPa Figure 1 2 1 .

b) interface normal stress, ETW, prior to loading -1

W. TEN.. 25

XcajRPaD

IM

d) 25% interface degradation, cracking at 17 MPa

A S 4 / 4 0 0 1 Unidirectional Composite, Elevated Temperature, Wet Condition ( 9 3 " C , 1% M), Transverse Tensile Loading. Extent of ,Interface and Watrix Cracking, Based Upon a Maximum Aormal Stress Failure Criterion.

presence

of m o i s t u r e .

The AS4/3501-6

composites i n d i c a t e d g r e a t e r

i n f l u e n c e s , a s p r e v i o u s l y shown. Although

no

will

results

be

presented

here,

t h e u s e of a n

o c t a h e d r a l shear s t r e s s f a i l u r e c r i t e r i o n again did not correlations

with

the a

good

data.

Assuming

interface

resulted

expected,

b u t t h e s t r e n g t h was much t o o h i g h .

as for

in

experimental

produce good

prediction

of

a

perfect

modulus a s would be F i r s t c r a c k i n g , which

t h e maximum normal s t r e s s f a i l u r e c r i t e r i o n ( s e e F i g u r e 1 2 1 a )

occurred i n the

bulk m a t r i x r a t h e r than a t

a t 55

APa ( 7 . 9 k s i ) , t o t a l

ksi).

The e x p e r i m e n t a l l y

the i n t e r f a c e , i n i t i a t e d

f r a c t u r e being predicted a t

68 MPa ( 9 . 8

measured c o m p o s i t e s t r e n g t h s were

o n l y on

t h e o r d e r of 25 m a ( 3 . 6 k s i ) , a s shown p r e v i o u s l y i n F i g u r e 121. Assuming

a

25

percent

p r e d i c t e d c o m p o s i t e modulus excessive

interface

degradation

which was much

interface cracking

t o o low, b e c a u s e

which o c c u r r e d .

in a

resulted

of t h e

Correspondingly, t h e

c o m p o s i t e s t r e n g t h p r e d i c t i o n was t o o low, and t h e s t r a i n t o

failure

too g r e a t . 6.6

AS4/F155 C o r r e l a t i o n s As discussed i n d e t a i l i n

advertised actual

as

a

cure

rubber-toughened

temperature

m a n u f a c t u r e r was

was a l s o modeled h e r e .

127°C

3.

Thus, t h i s It w i l l be

(250°F)

F155 i s

c u r e epoxy.

( 2 6 0 ' ~ ) recommended

by

The the

composites t e s t e d h e r e , a s

127OC (260°F) c u r e noted t h a t t h e

temperature

o t h e r two m a t r i x

cured o r postcured a t higher temperatures, t h e Hercules

3501-6 epoxy a t 204OC ( 4 0 0 ° F ) .

of

121°C

used i n f a b r i c a t i n g t h e

discussed i n Section

s y s t e m s were

S e c t i o n s 3 and 4 , t h e Hexcel

1 7 7 O C (350°F) and t h e H e r c u l e s

4001 b i s m a l e i m i d e a t

6.6.1

Thermal R e s i d u a l S t r e s s e s The

coefficient

rubber-toughened

theraal

of

expansion

epoxy was h i g h e r t h a n t h o s e of

s y s t e m s , a s might be e x p e c t e d ( s e e T a b l e 4 ) . lower

cure temperature,

when

of

and h e n c e

the

Hexcel

F155

t h e two o t h e r m a t r i x

However, b e c a u s e of t h e

the smaller temperature decrease

c o o l i n g down t o room t e m p e r a t u r e , t h e t h e r m a l r e s i d u a l s t r e s s e s

i n t h e A S 4 1 ~ 1 5 5 c o m p o s i t e s were p r e d i c t e d t o than i n the

o t h e r two c o m p o s i t e

The

composites

corresponding were

respectively.

-21

For example,

i n t h e AS41F155 c o m p o s i t e was

i n t e r f a c e normal s t r e s s ksi).

systems.

be s i g n i f i c a n t l y lower

stresses

14Pa

(-3.0

in ksi)

the highest

.-lo MPa (-1.4

t h e AS414001 and AS4/3501-6 and

-31

MPa

(-4.5

ksi),

Unfortunately, s i n c e t h e s e a r e compressive s t r e s s e s a t

the interface, higher s t r e s s e s are favorable i f a

transverse tensile

l o a d i n g i s t o be a p p l i e d , a s b e i n g c o n s i d e r e d h e r e . Ploisture-Induced S t r e s s e s

6.6.2

The c o e f f i c i e n t was

of m o i s t u r e e x p a n s i o n of t h e Hexcel F155 m a t r i x

comparable t o t h a t of t h e

t h a t of

H e r c u l e s 3501-6 epoxy, and lower t h a n

t h e H e r c u l e s 4001 b i s m a l e i m i d e ( s e e

It w i l l a l s o

Table 5 ) .

b e r e c a l l e d t h a t t h e a v e r a g e f i b e r volumes of t h e A ~ 4 / ~ 1 5c5o m p o s i t e s were lower t h a n An

for the other

average f i b e r

volume of

micromechanics a n a l y s e s . maximum i n t e r f a c e normal although

tensile,

stresses in

-was

two c o m p o s i t e s y s t e m s 40 p e r c e n t

As a r e s u l t of

only

t h e AS414001 and

4 MPa

is

favorable

in

i n the present

these various factors, the

residual s t r e s s - a t the (0.6 k s i ) ,

ETW t e s t c o n d i t i o n ,

The

corresponding

AS413501-6 c o m p o s i t e s were

k s i ) and 29 1W.a ( 4 . 2 k s i ) , r e s p e c t i v e l y . stress

was modeled

( s e e Table 6 ) .

terms

of

9 >Pa ( 1 . 3

T h i s lower t e n s i l e r e s i d u a l

subsequent

transverse

tensile

loadings.

- Tensile Loading Transverse

6.6.3 6.6.3.1

Room Temperature, Dry

The micromechanics transverse

tensile

analysis consistently underpredicted the RTD stiffness

of

composites, as can be seen in Figure 122. for the

maximum normal stress

cracking

did

predicted

not

initiate

cannot be

at

low

The measured

unidirectional

These particular plots are

failure criterion.

attributed to

prior discussions.

AS4/F155

the

stress

But

levels, the low moduli

this effect,

moduli of

since matrix

as was the case in

the Hexcel

F155 matrix

were lower than for the other two resin systems (see Tables 2 and 3 1 , but this was not

unexpected and there is no reason

to suspect these

experimental data.

Variations in fiber volume do not appear to be an

explanation either.

A fiber volume of 40 percent was modeled and, as

indicated in Table 6 , this is a representative

average value for the

various AS4/F155 unidirectional composites. For

the

occur until first

interface

a stress level of

crack

loading), matrix

perfect

initiated

and

matrix

spread

the upper

first failure did not

59 MPa (8.5 ksi)

the

immediately

again, to

Full failure

in

assumption,

to

the x axis (the axis of

the region

being modeled.

as indicated in

Figure 122.

That is, once a crack initiated, complete fracture followed Similar results were obtained for the case, but the

crack

25 percent

quickly.

degraded interface

at lower stress levels, as indicated in Figure 122.

did

tend

to

follow

,This

the interface and across the

boundary of

was at 62 MPa (9.0 ksi),

at

was attained.

Also,

the interface more closely for the

degraded interface model, as might be expected.

R T DRY,

LNSIZED

R .T DRY,

Figure 122.

DRY,

828 SIZED

b) EPON 828 sized

a) unsized

c) PVA sized

R T

PVA

SIZED

R T

DRY,

POLYSULFON SIZED

d) polysulfone sized

~ S 4 / F 1 5 5Unidirectional Composite, Room Temperature, Dry, Transverse Tensile Loading. Correlations Between Predictions and Experimental Data for All Four Fiber Sizings, Using a Maximum Normal Stress Failure Criterion.

F i g u r e s 123a t h r o u g h 123c i n d i c a t e t h e i n t e r n a l s t r e s s s t a t e s i n the

p e r f e c t i n t e r f a c e model c o m p o s i t e a t

an a p p l i e d s t r e s s l e v e l of

41 MPa ( 6 k s i ) , i . e . , b e f o r e any l o c a l f a i l u r e s had o c c u r r e d . 123a

indicates

developed, However,

the

interface

t h e maximum

normal

value being

as indicated i n

tensile

q u i t e high

Figure 123b, t h e

stresses

Figure

which had

a t 69 ~ 9 (a1 0 k s i ) .

maximum p r i n c i p a l s t r e s s

away from t h e i n t e r f a c e was even s l i g h t l y h i g h e r , i . e . ,

74 MPa

ksi), in

This e x p l a i n s

the matrix along the x

a x i s between f i b e r s .

(10.7

why t h e i n i t i a l f a i l u r e e v e n t u a l l y o c c u r r e d away from t h e i n t e r f a c e .

will

It

also

be

noted

that

Hexcel F155 m a t r i x was measured of t h e

o t h e r two

tensile

t o be c o n s i d e r a b l y h i g h e r t h a n

matrix materials.

s t r e n g t h of

which was a b o u t

t h e RTD t e n s i l e s t r e n g t h o f t h e

t h e Hexcel

As i n d i c a t e d

F155 m a t r i x

25 p e r c e n t h i g h e r t h a n t h a t

i n Table

that 2, t h e

was 77 MPa ( 1 1 . 2 k s i ) , of t h e H e r c u l e s 3501-6,

and a l m o s t 50 p e r c e n t h i g h e r t h a n t h a t of t h e H e r c u l e s 4001. On t h e o t h e r h a n d , t h e s h e a r s t r e n g t h of t h e Hexcel F155 was n o t so high. about

50 p e r c e n t t h a t

previously

a s i n d i c a t e d i n T a b l e 3 , i t was

A t 48 MPa ( 7 . 0 k s i ) ,

discussed

H e r c u l e s 4001,

of t h e H e r c u l e s in

a t only

Section 2 . 4 MPa

6.5,

3501-6 epoxy. the

(17 k s i ) ,

shear

only

Of c o u r s e , a s s t r e n g t h of t h e

was q u e s t i o n a b l y low and

t h u s c a n n o t b e compared. While t h e s e v a r i a t i o n s i n n e a t r e s i n t e n s i l e and s h e a r s t r e n g t h s may be e x p l a i n e d i n l a r g e p a r t by t h e d i f f i c u l t i e s i n p e r f o r m i n g n e a t resin testing,

use of t h e s e

obviously

a

has

example, u s e of i s based

strong

r e s u l t s i n the

influence

on

micromechanics a n a l y s i s

the predicted r e s u l t s .

For

t h e o c t a h e d r a l s h e a r s t r e s s f a i l u r e c r i t e r i o n , which

upon t h e

shear t e s t

d a t a , would

be e x p e c t e d

t o lead

to

a) interface normal stress at 41 ? P a F I S 'TRCE(S. SDJ , EFECr M .

A D C D

b) first principal stress at 41 MPa F156llVM

TEN.

2

5

X

~

C

c) octahedral shear stress at 41 MPa

d) 25% interface degradation, cracking at 45 MPa

Figure 123. A S 4 / F 1 5 5 Unidirectional Composite, Room Temperature, Dry, Transverse Tensile Loading. Stress Contours and Extent of matrix Cracking, Rased Upon a daximum Normal Stress Failure Criterion. -240-

~

earlier

c r a c k i n g , due

to the

Hexcel El55 m a t r i x m a t e r i a l .

lower measured

F i g u r e 123c i s a p l o t of t h e o c t a h e d r a l

shear s t r e s s

d i s t r i b u t i o n a t an applied s t r e s s

i.e.,

to

prior

any

s h e a r s t r e n g t h of t h e

failure.

will

It

of 41 MP$ ( 6 . 0 k s i ) ,

be n o t e d t h a t t h e h i g h e s t

s t r e s s e s o c c u r r e d a t t h e i n t e r f a c e , about 50° above t h e l o a d i n g a x i s , and a l s o a l o n g t h e y a x i s away from t h e i n t e r f a c e . Assuming first failure however,

a

25

percent

interface

t o occur e a r l i e r i n t h e

total failure

respective values v a l u e s were i n

s t r e n g t h d e g r a d a t i o n caused loading, as expected.

followed i n i t i a l

Again,

f a i l u r e very closely.

were 41 MPa ( 6 . 0 k s i ) and 45 MPa ( 6 . 5 k s i ) .

r e a s o n a b l e agreement w i t h

The These

the experimental data,

as

i n d i c a t e d i n Figure 122. Use of t h e o c t a h e d r a l s h e a r s t r e s s f a i l u r e composite s t r e n g t h p r e d i c t i o n interface

assumption,

p e r c e n t degraded

and

of 8b l e a an

only

i n t e r f a c e model.

theory resulted i n a

(12.4 k s i ) f o r

the perfect

lower v a l u e f o r a 25

slightly

That i s , once a g a i n t h e p r e d i c t e d

s t r e n g t h s were t o o h i g h u s i n g t h i s f a i l u r e c r i t e r i o n . 6.6.3.2

E l e v a t e d T e m p e r a t u r e , Wet

Correlations tensile

between

stress-strain

the

curves

analytically for

the

predicted

unidirectional

c o m p o s i t e , b a s e d upon a maximum normal s t r e s s

transverse AS4/F155

f a i l u r e c r i t e r i o n , and

t h e experimental d a t a a r e p l o t t e d i n Figure 124.

The a s s u m p t i o n of a

p e r f e c t i n t e r f a c e r e s u l t e d i n a p r e d i c t e d c o m p o s i t e modulus which was t o o n i g h i n g e n e r a l . F i r s t f a i l u r e was p r e d i c t e d a t 45 MPa ( 6 . 5 k s i ) , with complete ksi).

f r a c t u r e following almost

Assuming a

immediately a t 47

MPa ( 6 . 8

25 p e r c e n t degraded i n t e r f a c e lowered t h e o n s e t o f

c r a c k i n g t o 31 +lPa ( 4 . 5 k s i ) , and f u l l f a i l u r e t o 35 W a ( 5 . 0 k s i ) .

38 DEG. C , l X H.

0 5

INSUED

1

STRAIN

38 DEG C , l X H,

'a

b ) EPON 828 sized

38 M G C , I % M,

PVA

SIZED

38 DEG

B

0 0 5

S

c)

SIZED

m)

a) unsized

e.0

820

PVA sized

Figure 124.

1

a

W BERCEM)

1 .s

C , I X M,

WLYSULFONE SIZED

0

0

ee

0.5

1

e

1

.s

STRAIN BERCOJT)

d) polysulfone sized AS4/F155 Unidirectional Composite , Elevated Temperature, Wet Condition (38"C, 1% M ) , Transverse Tensile Loading. correlations Between Predictions and Experimental Data for All Four Fiber Sizings, Using a Maximum Normal Stress Failure Criterion.

There was

som,e concern

program that, because of

in

the

the ability

experimental of the

portion of the

Hexcel F155 matrix to

absorb moisture rapidly (see Table 5 for moisture saturation levels), the AS41F155 composites may

have absorbed additional moisture

waiting

assess the

to be

tested.

To

while

potential influences of this 1 2 4 were

repeated

assuming a 2% M (i.e., a two weight percent moisture weight

gain) in

possibility, the

these

computer simulations of Figure

composites.

increase

The

additional

the unfavorable

the matrix,

tensile residual

and thus, presumably

composite strengths.

moisture

This

would

be expected to

hygrothermal stresses in

promote matrix cracking

would also decrease the

and lower

apparent modulus

and increase the strain to failure. Nhile the actual predictions did indicate these expected trends, the magnitudes of the changes were relatively small. begin

to crack at

slightly lower levels

The matrix did

of applied stress, but the

cracks did not grow to total failure as rapidly. This was associated with the lower modulus and greater failure strain of the

Hexcel F155

epoxy at the higher moisture level (see Table 3). The

crack

patterns

at

total

failure

for

the four computer

simulations, i.e., perfect and 25 percent degraded interfaces, and 1% M

and 2% M, are shown in

they were

not great.

As

Figure 1 2 5 .

While there were differences,

expected, the crack

followed the degraded

interface more closely. This

type of

predictive tool influence of a to

demonstrate

analysis

available.

again points It was

out the value of having a

relatively simple to

possible abnormal amount of that

even

if

it

had

assess the

moisture absorption, and

occurred, it would not have

PAGE 6% qu A L ~ W

-I OD-

e e m w m

m . WP&ImT

F168'1I1L#

-

m

r

W

~

-

5

1

C

wlls

- m a

a

W - R

rn

W

C

m

-

g

W

T

M -9

wrs

R a a w R

~

-

RLnKI- W

sa

w u

W

a) perfect interface, 1%M

b) perfect interface,' 2%M

c) 25% interface degradation, 1%M

d) 25% interface degradation, 2%M

Figure 125.

AS4/F155 Unidirectional Composite, Elevated Temperature, Wet Condition, Transverse Tensile Loading. ' ~ n f l u e n c e of Composite Xoisture Content and Interface Bond Strength on Predicted Crack Patterns, Using a i-laximum Normal Stress Failure Criterion.

drastically altered the experimental results obtained.

6.7 Summary of Results It

has

been

micromechanics

demonstrated

analysis

can

that

the

predict

'W02D

finite

unidirectional composite

transverse tensile properties with reasonable accuracy. can be fiber

used to volume,

show the interface

content, etc., program. design the indicated

without

In future

be

the

are negligible.

necessity

selected variables

particularly

of

performing

will hopefully

matrix, so

neglected or only included to

The analysis such as

strength, test temperature, moisture

work, it

original test to

influences of bond

element

that the

important

also be

a full test used to help

parameters which are

can be tested, and others

the extent necessary to show that they

SECTION 7 CONCLUSIONS AND RECOMMENDATIONS This study demonstrated that other matrix

and

the

specific

loading

composite performance than sizings utilized here. in that it

factors such as the type

mode

any one of

of

have greater influences on

the four different

This is, of course, a

composite

very positive finding

suggests the latitude which is permissible in selecting a

fiber sizing. It was demonstrated that a unidirectional composite is still the most

desirable

composite

form

quasi-isotropic

laminates

produced

tended

to

obscure

the

role

fracture. Even -the simple

for

of

performance complex

evaluations.

The

failure modes, which

the fiber-matrix interface in the

interlaminar (short beam) shear

the quasi-isotropic laminates were not as

useful as shear

tests of tests of

the unidirectional composites would have been. The

two

dependent on practical

single

fiber

the testing

graphite fiber.

This

The single

thin fiber disk

is a very delicate

if not done exactly right, will even if those

done properly, the obtained

using

detail in Section 4.6. dogboned tensile

test

technique, and

screening tests.

the formation of a very

composite

other

methods

too time

used were too

consuming to

fiber pullout test requires of matrix around

a single

fabrication procedure, and

not produce valid results.

results are often test

be

methods.

In fact,

in wide variance with This was discussed in

The second single fiber test method used, a

coupon of neat

resin with a

i------------'--, . -Preceding Page Blank :, -

247 ..

-

y-

-

-..-

. .

single graphite fiber

embedded in it with normal The

along its axis,

also proved to

structural resins

such as

test method was originally

capable

of

being

cured

strains to failure. To

summarize

carefully

at

those of

use

the present study.

developed using model resin systems, low

temperatures

and exhibiting high

The present resins were not in this category. the

test

documented in

test configurations interface

be difficult to

procedures, much

this report,

was learned, and is

about the

ability of various

to serve as sensitive indicators of fiber-matrix

performance.

Complex

laminates,

such

as

the

quasi-isotropic laminates specified for use in the present study, are not good

choices; and model composites such as the single fiber test

specimens are

not sufficiently representative of

volume composites. fundamental

A simple unidirectional composite, tested

loading modes,

transverse

tens ion,

logical

those

which

loading

viz,

modes

compression,

clearly the proper

emphasize to

the

use

role

if

it

interface which is to be evaluated. an Iosipescu shear test

in the

axial tension, axial compression,

transverse

(longitudinal) shear, is tests,

actual, high fiber

and

choice. of

in-plane

Even of

these

the interface are the

is the effectiveness of the

The first choice would thus be

of the unidirectional composite, followed by

transverse tensile and axial compression tests. Along

with

the

positive

fact

that

there

was

no

strong

distinction in the performance of the four different fiber sizings in so many different loading modes, vast were

generated.

this

report

These

and its

amounts of useful design data

data are

fully presented

appendices.

Properties

and documented in

such as

neat

resin

/

stress-strain

curves

to

failure, and

coefficients of thermal and

moisture

expansion, are

influences resin

of

not

elevated

normally

temperature and

and the corresponding composites

are documented electron

in the

available.

form of

microphotographs

of

Likewise,

the

moisture on both the neat

are included.

an extensive composite

Failure modes

collection of scanning

fracture

surfaces.

These

hopefully will be very useful to future investigators, for comparison purposes as new fiber sizings are developed.

A finite element micromechanics program, WY02D,

only recently developed

extensively, was also introduced. transverse presented

tensile data in

only

Section 6, and

was

it

Only

shown

that

related computer

and therefore not

here.

their

However,

correlations

analysis

the results

with the actual

the great potential the

yet used

the unidirectional composite

were analyzed

experimental data, demonstrate Not

analysis and

of such a

can

predict

tool. actual

unidirectional composite response, it was demonstrated that it can be used to estimate

the influence of potential variables.

is this capability that is of particular significance.

In fact, it If the actual

testing has already been done, an analysis to predict these properties

is superfluous.

consuming and

However, testing

expensive; and if it does

measured

is both extremely time

not lead to useful results,

it is also wasteful of resources. The micromechanics analysis can be used to screen candidate material combinations under various and

environmental

difficult to

conditions, including

achieve in the

those

which

laboratory. Only those

loading would

be

most promising

combinations then need be actually fabricated and tested. The present actual composite

study was designed by NASA-Ames to generate data on material systems and fiber

sizings in current use.

This

was

achieved, as

fully

documented

in

this

report.

It is

recommended that in any future study, model systems also be included. For

example,

the

present

study

would

have

benefited

from

the

inclusion of a fiber surface treatment or fiber sizing which resulted in little or no interface bonding.

This would have provided a strong

baseline for comparisons. Likewise, is

strongly

evaluation,

recommended. by

environments. only

the

permitting

For

room

environmental

This

temperature, dry

possible

to

than the

combinations

identify losses

the

of

use of only

of

more

in-depth

materials

as the present

Thus,

and

study was,

it was not possible to

from moisture

temperature or

critical

a

methods

and one elevated temperature, wet

condition were studied.

The

permit

example, as extensive

temperature effects

occurred.

will

more

separate

significant

focusing on fewer test

composite

two .or three

eight different methods called

effects.

Nor was it

moisture level at which properties

would

have

basic test methods, rather for in

the present study,

will permit these additional determinations. In

conclusion, it

is

recommended

that additional studies be

conducted, using additional matrix materials, wider range

of fiber

sizings.

strain curves to 'failure, and fabrication and such

as

the

The

generation of

of

is extremely

In

these requirements.

It is

fracture

surface

materials used should not be

this way, a complete and

can gradually be assembled.

important. Details,

fiber volumes,

characteristics, and the quality of the overlooked.

complete stress-

the careful documentation of composite

test conditions, recording

other fibers, and a

therefore useful data base

hoped that the present work meets

REFERENCES 1.

"Victrex PEEKICarbon Fibre," Data Sheet APC PD3, Imperial Chemical Lndustries, ICI Americas, Inc., Wilmington, Delaware, 1983.

2.

"Hercules Product Data Sheet No. 847-3: Magnamite Graphite Fiber Type AS4," Hercules, Inc., Magna, Utah, August 1981. "EPON 828 Epoxy Resin," Shell Data Sheets, Shell Development Company, Houston, Texas, 1984. "Udell P1700 Polysulfone Resin," General Electric Data Sheets, Plastics Operations, General Electric Company, Pittsfield, dassachusetts, 1982. "Hercules 3501-6 Epoxy Resin," Hercules Specification HS-SG-560, Revision A , Hercules, Inc., Magna, Utah, November 1983. "Hercules 4001 Bismaleimide Resin," Hercules Data Sheets, Hercules, Inc., ldagna, Utah, 1983. "Hexcel F155 - A Controlled Flow Epoxy Resin for Laminating and Co-Curing at 250°F Cure," Product Data Sheet, Hexcel Corporation, Dublin, California, March 1982. "Techkits Epoxy Adhesive A-12," Techkits, Inc., Demarest, New Jersey, 1984. D. F. Adams and D. E. Walrath, "Hygrothermal Response of Polymer Matrix Composite Materials," Report UWME-DR-901-102-1, Department of Mechanical Engineering, University of Wyoming, September 1979. D. A. Crane and D. F. Adams, "Finite Element Micromechanical Analysis of a Unidirectional Composite Including Longitudinal Shear Loading," Report UWME-DR-101-101-1, Department of Mechanical Engineering, University of Wyoming, February 1981. R. S. Zimmerman, D. F. Adams, and D. E. Walrath, "Investigation of the Relations Between Neat Resin and Advanced Composite Mechanical Properties, I' Keport UWME-DR-301-101-1: Volume I Results, Volume 11 - Appendices, Department of Mechanical Engineering, University of Wyoming, May 1983. R. S. Zimmerman, D. F. Adams, "Mechanical Properties Testing of Candidate Polymer Matrix Materials for Use in High Performance Composites," Keport UWIC-DR-401-104-1, Department of Mechanical Engineering, University of Wyoming, August 1984. E. M. Odom and D. F. Adams, "A Study of Polymer Matrix Fatigue Properties," Report UWME-DR-301-103-1, Department of Mechanical

Engineering, University of Wyoming, June 1983. D. E. Walrath and D. F. Adams, "Analysis of the Stress State in an Iosipescu Shear Test Specimen," Report UWME-DR-301-102-1, Department of iqechanical Engineering, University of Wyoming, June 1983 . D. E. Walrath and D. F. Adams, "Verification and Application of the Iosipescu Shear Test Method," Report UWIYE-DR-401-103-1, Department of Mechanical Engineering, University of Wyoming, June 1984. D. F. Adams and D. E. Walrath, "Iosipescu Shear Properties of SMC Composite Materials," Proceedings of the Sixth Conference on Composite Haterials: Testing and Design, ASTM STP 787, Phoenix, Arizona, May 1981, pp. 19-33. D. E. Walrath and D. F. Adams, "The Iosipescu Shear Test as Applied to Composite Materials," Experimental Mechanics, Vol. 23, No. 1, March 1983, pp. 105-110. D. S. Cairns and D. F. Adams, "Moisture and Thermal Expansion of Composite Materials," Report UWME-DR-101-104-1, Department of Mechanical Engineering, University of Wyoming, ~ovember1981.

D. S. Cairns and D. F. Adams, "Moisture and Thermal Expansion Properties of Unidirectional Composite Materials and the Epoxy Matrix," Journal of Reinforced Plastics and Composites, Vol. 2, No. 4, October 1983, pp. 239-255. S. V. Hayes, "Rate Sensitive Tensile Impact Properties of Fully and Partially Loaded Unidirectional Composites," M.S. Thesis, Department of Mechanical Engineering, University of Wyoming, Lararnie, Wyoming, May 1980. S. V. Hayes and D. F. Adams, "Rate-Sensitive Tensile Impact Properties of Fully and Partially Loaded Unidirectional Composites," Journal of Testing and Evaluation, Vol. 10, No. 2, March 1982, pp. 61-68.

N. Irion, D. F. Adams and D. E. Walrath, "Compression Creep Behavior of SMC Composite Materials," Report UWME-DR004-104-1, Department of Mechanical Engineering, University of Wyoming, March 1980.

M.

d. N. Irion and D. F. Adams, "Compression Creep Testing of Unidirectional Composite Materials," Composites, Vol. 12, No. 2, April 1981, pp. 117-123.

L. Penn, F. Bystry, W. Karp and S. Lee, I1Aramid/~poxyvs. Graphite/Epoxy: Origin of the Difference in Strength at the Interface," Proceedings of the 185th National Meeting

of the American Chemical Society, Seattle, Washington, March 1983.

D. F. Adams, R. L. Ramkumar, and D. E. Walrath, "Analysis of Porous Laminates in the Presence of Ply Drop-offs and Fastener Holes," Northrop Technical Report NOR 84-10, Naval Air Systems Command Contract N00019-82-C-0063, May 1984. D. F. Adams and D. R. Doner, "Transverse Normal Loading of a Unidirectional Composite," Journal of Composite daterials, Vol. 1 , No. 2, April 1967, pp. 152-164. D. F. Adams, "Inelastic Analysis of a Unidirectional Composite Subjected to Transverse Normal Loading," Journal of Composite Materials, Vol. 4, No. 3, July 1970, pp. 310-318. D. F. Adams, "Elastoplastic Crack Propagation in a Transversely Loaded Unidirectional Composite," journal of Composite Materials, Vol. 8, No. 1, January 1974, pp. 38-54.

B. D. Agarwal and L. J. Broutman, Analysis and Performance of Fiber Composites, John Wiley & Sons, New York, N.Y., 1980. L. T. Drzal, M. J. Rich, J. D. Camping and W. J. Park, "Interfacial Shear Strength and Failure Mechanisms in Graphite Fiber Composites," Proceedings' of the 35th Annual Technical Conference, The Society of the Plastics Industry, 1980, Paper 20-C. R. F. Cilensek, "WY02D Finite Element Analysis Computer Program User Instructions and Documentation," Composite Materials Research Group, University of Wyoming, Laramie, Wyoming, August 1984.

D. F. Adams, "Inelastic Analysis of a Unidirectional Composite Subjected to Transverse Normal Loading," Report kY-6245-PRY The Rand Corporation, May 1970. D. F. Adams and S. W. Tsai, "The Influence of Random Filament Packing on the Transverse Stiffness of Unidirectional Composites," Journal of Composite Materials, Vol. 3, No. 3, July 1969, pp. 368-381. s Crack Propagation as D. F. Adams and D. P. Murphy, " ~ n a l ~ s iof an Energy Absorption 14echanism in Metal Matrix Composites," Report UWME-DK-101-102-1, Department of dechanical Engineering, University of Wyoming, February 1981. R. M. Richard and J . fi. Blacklock, "Finite Element Analysis of Inelastic Structures," AIAA Journal, Vol. 7, No. 3, March 1969, pp. 432-438.

APPENDIX A TABLES OF INDIVIDUAL SPECIMEN TEST RESULTS

-

[ I

Receding page

~ l ~ k T k- ;:.-+k- (ksi)

Room T e m p e r a t u r e , Dry ABRZ 01 2 3 4 5

28 16 10 12 8*

4.0 2.3 1.5 1.8 l.l*

Average S t d . Dev.

17 8

2.4

ABRZ 10 11 13 14

37 59 36 28

5.3 8.5 5.2 4.1

Average S t d . Dev.

40

5.8 1.9

1.1

100°C, Dry

13

Room T e m p e r a t u r e , 7 . O % M ABEZ 10

43 43 37 23"

6.2 6.2 5.4 3.3"

Average S t d . Dev.

41 3

5.9 0.5

ABEZ 0 1 2 3 4 5

12 10* 17 15 19

1 .8 1.5* 2.5 2.2 2.7

Average S t d . Dev.

16 3

2.3 0.4

11 12 13 14

-

-

*Not i n c l u d e d i n a v e r a g e

Shear 9odulus (GPa) (Msi)

Shear S t r a i n (percent)

Table A4 Individual Hexcel F155 Neat Resin Iosipescu Shear Test Results Specimen No.

Shear Strength (ksi) (MP~)

Shear dodulus (Gpa) (~si)

Shear Strain (~ercent)

Room Temperature, Dry

Average Std. Dev.

48 7

7 .O 1 .O

43 43 41 43

6.3 6.2 6 .O 6.2

43 1

6.2 0.1

1.1 0.1

75"C, Dry ABRX 10

11 12 14 Average Std. Dev.

Room Temperature, 9.6%M ABEX 10 11 12 13 14

48 43 46 48

7 .O 6.2 6.6 6.9

Average Std. Dev.

46 3

6.7 0.4

ABEX 00 01 02

35 34 33 33 34

5 .0 4.9 4.8 4.8 4.9

34 1

4.9 0.1

03 04 Average Std. Dev.

-

-

*Not included in average

-250-

0.15 0.01

5.4 0.5

Individual Fiber Volumes for the Various AS4 Graphite/Hercules 3501-6 Epoxy Composite Panels Fiber Sizing -.------

Unidirectional Panels

(percent)

Quasi-Isotropic Panels (percent

Uns i zed

Average Std. Dev.

4 i .3

Average Std. Dev.

58.9

Aver age Std. Dev.

56.7

Average Std . Dev.

0.3

Average Std. Dev.

.

54.5 0.7

EPON 828

Average Std. Dev.

58.8 0 .8

Average Std. Dev.

64.1

0.4

52.4 0.4

Average Std. Dev.

52 .O

0.3

1.1

Polysulfone

0.4

'i'able A6 Individual Fiber Volumes for the Various AS4 Graphite/Hercules 4 0 0 1 Bismaleimide Composite Panels

Fiber Sizing

Unidirectional Panels -(percent)

Quasi-Isotropic Panels (percent)

Uns ized

Average Std. Dev.

52.5 1.5

Average Std. Dev.

54.5 1.3

Average Std. Dev.

56.7

0.7

Average Std. Dev.

52.2 3.1

Average Std. Dev.

56.2 0.8

Average Std. Dev.

53.5 4.3

Average Std. Dev.

62.8 2.3

Average Std. Dev.

57.2 4.3

EPON 8 2 8

PVA

Polysulfone

.

,

'Table A7 I n d i v i d u a l F i b e r Volumes f o r t h e V a r i o u s AS4 G r a p h i t e I H e x c e l F155 Epoxy Composite P a n e l s

Fiber Sizing

..

Unidirectional Panels (percent)

Quasi-Isotropic Panels (percent)

Unsized

Average S t d . Dev.

37.7 1.8

Average S t d . Dev.

28.4 1.9

Average S t d . Dev.

40 .O 0.7

Average S t d . Dev.

43.8 2.0

Average S t d . Dev.

39.7 0.2

Average S t d . Dev.

47.4

Average S t d . Dev.

44 .O 3.4

Average S t d . Dev.

42.2

EPON 828

PVA

0.7

Polysulfone

2.6

Table A8 Individual AS4/3501-6 Unidirectional Composite Transverse Tensile Test Results at the Room Temperature, Dry Condition

Fiber Sizing Unsized

Specimen No.

Ultimate Strain (percent)

1.5" 3 .O 4.0 2 -5 2.7 4.5* 3.9

8.8 9.7* 7.1 7.2 7 .O 7.6 8 .O

1.28 1.40* 1.03 1.04 1.01 1.10 1.16

0.11" 0.21 0.39 0.24 0.27 0.42* 0.33

22 5

3.2 0.7

7.6 0.7

1.10 0.10

0.29 0.07

-

-

20 13* 26 20 19 26"

2.9 1.9* 3.7 2.9 2.8 3.8*

8.0 7.2 7.7 7.7

1.16 1.04 1 .ll 1 .ll

7.8 7.5

1.13 1.09

0.28 0.16* 0.33 0.25 0.25 0.34*

Average Std. Dev.

21 3

3.1 0.4

7.7 0.3

1 .ll 0.04

0 -28 0.04

AFRY 20 21

19* 23

2.8* 3.4

8.0 8 .O

1.16 1.16

0.22* 0.30

Average Std. Dev.

AFRY 10

11 12 13 14 15 16

PVA

lo*

Tensile Modulus (GP~) (Msi)

21 28 17 19 31* 27

AFRY 00 1 2

3 4 5 6

EPON 828

Tensile Strength (ma) (ksi)

-

-

T a b l e A9 I n d i v i d u a l AS4/3501-6 U n i d i r e c t i o n a l Composite T r a n s v e r s e T e n s i l e T e s t R e s u l t s a t t h e E l e v a t e d Temperature, Wet C o n d i t i o n (93"C, 14M) Fiber Sizing Uns i z e d

EPON 828

Specimen No.

Tensile Strength (MPa) (ksi)

T e n s i l e Modulus (GP~) ( ~ s i )

AFEY 00 01 02 03 04 05 06 07

13 21* ' 18 17 15 14 14 14

Average S t d . Dev.

15 2

2 -2 0.3

5.2 0.5

0.76 0.07

AFEY 10

12 12 12 10 14* 12 9*

lo*

1.8 1.7 1 .8 1.5 2 .O* 1.8 1.3 1.4"

5.7 5.9 6.1 6.1 6.8 5.9 6.4 5.2

0.82 0.86 0.89 0.88 0 -99 0.85 0.93 0.75

12 1

1.7 0.1

6 .O 0.5

0.87 0.07

11 12 13 14 15 16 17

Average S t d . Dev.

Ultimate S t r a i n ( p e r c en t )-

0.34 0.06

0.21 0.01

Table A9

Fiber Sizing PVA

Specimen No.

Tensile Strength (.ma) (ksi)

T e n s i l e Modulus (GP~) (Msi)

Ultimate S t r a i n (percent)

AFEY 20 21 22 23 24 25 26 27 28 29 Average S t d . Dev.

Polysulfone

Continued -

11 1

1.6 0.1

3.6 0.8

0.52 0.11

0.22 0.03

16 1

2.3 0.1

5.5 0.3

0.80 0.05

0 -31 0.02

AFEY 30 31 32 33

34 35 36 37 Average S t d . Dev.

*Not included i n average

9 u,

..

u-lo

0 0

aJ 'El 3 e m

o

G U (d

L I R

aJ U

-2 'El

P

3

=I m

a s1 0

x

v

aJ

-

d

0)

.d

-dn

m rd

. .

s

.,-I U

e

d .?I

U

h

m r d

$2 '3

*m c ~ m a-xb r o d o

d m U74~ndmW,mu-l m

u

(d

aJ 'El

>

U

4 cn

C a,

E

.d U

a,

a cn

3

.

0 Z

o - ~ ~ m d m da l@ ~ o o o o o o o o aoa (d

N

5

L I . a,

>

u u

C cn

ooooooool

0 0

([I

&

h

H b

CI

0) U .rl V)

.

d

&

.rl n

0 1

a

'a 0 N

0)

D

a

M

LI

m

u

m

([I

c nl 0)

M-

C3

U0)

a

2 4

0)

0)

C M

0 .rl

U U

B

O O 0) 03 & - 4 0)

a s u

.rl

C 3

u ([I

In In m

u

-. 4

kl

,-I

4

V)

LA

3

a)

4 &

3

Odhlrn.JIn\D d 4 d d d d d

3

2

a@J

Ma ([I

&

.

a U 4 cn 0)

3

-Y.

- o c n o c n ~ m c n m - j . o m m a m m

cnm m

Table A13

Fiber Sizing PVA

Specimen No.

Continued

Tensile Strength (MPa) (ksi)

Tensile Modulus (GP~) (Msi)

Ultimate Strain (percent)

AFEX 20

21 22 23 24 25 26 27

Average Std. Dev.

Polysulfone

12 1

0.1

3.5 0.2

0.51 0.02

0.38 0.04

33 2

4.7 0.2

5.1 0.3

0.74 0.04

0.05

1.8

AFEX 30 31 32 33 34 35

36 37 Average Std. Dev.

*Not included in average

0.69

Table A14 Individual AS4/3501-6 Unidirectional Axial Compression Test Results at the Room Temperature, Dry Condition Fiber Sizing Unsized

Specimen No.

PVA

Compressive Modulus (GP~) (Msi)

Ultimate Strain (percent)

AGRY 00 01 02 03 04 05 06 07 08 09 Average Std. Dev.

EPON 828

Compressive Strength (ma) (ksi)

717 62

. '

104 9

100 6

14.5 0.9

1.58 0.62

AGRY 10 11 12 13 14 15 16 17 18 19 Average Std. Dev.

731 55

106 8

114 14

16.6 2.0

0.62 0.12

AGRY 20 21 22 23 24 25

752 883 703 821 876 752

109 128 102 119 127 109

121 111 141 126 119 113

17.5 16.1 20.5 18.3 17.2 16.4

0.74 1.08" 0.51 0.64 0.92 0.58

Average Std. Dev.

800 71

116 11

122 11

17.7 1.6

0.62 0.10

Table A14

Fiber Sizing

Polysulfone

Specimen No.

Continued

Compressive Strength (ma) (ksi)

Compressive Ultimate Modulus Strain (GPa) ( ~ s i ) (percent)

AGRY 30 31 32 33 34 35

36 37 38 39 Average Std. Dev.

*Not included in average

841

122

76

11

117 8

16.9 1.1

0.97 0.07

Table A15 Individual AS413501-6 Unidirectional Composite Axial Compression Test Results at the Elevated Temperature, Wet Condition (93"C, 1%M)

Fiber Sizing

Uns ized

EPON 828

PVA

Specimen No.

Compressive Strength (MPa) (ksi)

Compressive Ultimate Modulus Strain ( G P ~ ) ( ~ s i ) (percent)

AGEY 00 01 02 03 04 05 06 07 08 09 Average Std. Dev.

469 66

68.0 9.5

AGEY 10 11 12 13 14 15 16 17 18 19

541. 532 512 474 547 467 650 530 538 566

78.5 77.1 74.3 68.8 79.3 67.7 94.2 76.9 78.0 82.1

Average Std. Dev.

536 51

AGEY 20 21 22 23 24 25 26

79 8

11.5 1.2

0.55 0.08

77.7 7.4

87 11

12.7 1.6

0.54 0.10

517 51 0 479 549 456 543 531

75 . O 73.9 69.5 79.6 66.2 78.8 77.0

91 6 1* 113* 83

13.2 8.9" 16.4" 12.1

105 93

15.2 13.5

0.58 0.47 0.45 0.65 1.31" 0.69 0.53

512 Average S t d . D e v . 34

74.3 4.9

93 9

13.5 1.3

0.56 0.10

-

-

Table A15

Fiber Sizing

Specimen NO .

AGEY 30 31 32 33 34 35 36 37 38 39

Polysulfone

Average S t d . Dev - - -

--

-

-

-

-

*Not included in average

Continued

Compressive Strength (,*a) (ksi)

Compressive Ultimate Modulus Strain (GPa) ( ~ s i ) (percent)

Table A16 Individual AS4/4001 Unidirectional Axial Compression Test Results at the Room Temperature, Dry Condition

Fiber Sizing Unsized

Specimen No.

AGRZ 10 11 12 13 14 Average Std. Dev.

PVA

'

Compressive Ultimate Modulus Strain ( G P ~ ) ( ~ s i ) (percent)

AGRZ 00 01 02 03 04 05 06 07 08 09 Average Std. Dev.

EPON 828

Compressive Strength (ma) (ksi)

9 24 76

134 11

105 4

15.2 0.6

1.05 0.16

1083" 917 883 821 862

157" 133 128 119 125

157" 122 122 127 98*

22.7" 17.7 17.7 18.4 14.2"

0.86 0.87 0.71" 0.70" 0.92"

869 41

126 6

123 3

17.9 0.4

0.87 0.06

120 6

108 10

15.6 1.4

0.84 0.06

AGRZ 20 21 22 23 24 25 26 27 28 29 Average Std. Dev.

827 41

Table A16

Fiber Sizing

Specimen No. .-

Polysulfone

Continued

Compressive Strength (ltPa) (ksi)

Compressive Modulus (GP~) (~si)

Ultimate Strain (percent)

AGRZ 30 31 32 33

34 35 36 37 38 39 Average Std. Dev.

*Not included in average

889 62

129 9

128 6

18.6 0.8

0.60 0.13

Individual AS4/4001 Unidirectional Axial Compression Test Results At the Elevated Temperature, Wet Condition (93"C, l%M) Fiber Sizing Uns ized

Specimen 110. "

AGE2 00 01 02 03 04 05 06 07 08 09 AL

Compressive Strength (MPa) (ksi) 496 572 531 621 579 614 579 552 648 579 614

Average 579 Std. Dev. 41 EPON 828

Compressive Ultimate Modulus Strain ( G P ~ ) ( ~ s i ) (percent)

84 6

91 10

13.2 1.4

97 7

122 14

17.7 2.1

AGEZ 10 11 12 13 14 15 16 17 18 Average 669 Std.Dev. 48 AGEZ 20 21 22 23 24 25 26 27 28

490" 614 593 552 690" 614 510* 579 614

Table A17

Fiber Sizing

PVA

-

Specimen No.

Compressive Strength ( M P ~ ) (ksi)'

Compressive Ultimate Modulus Strain ( G P ~ ) ( ~ s i ) (percent)

AGEZ 29

7 lo* 614

103" 89

142 104

20.6" 15.1

0.58 0.61

Average Std. Dev.

600 24

87 4

107 .7

15.5 0.4

0.55 0.06

AGEZ 30

634 579 593 614 800" 786" 752" 579 690 607 90 5

123 4

17.9 0.6

0.49 0.04

AL

Polysulfone

Continued

31 32 33 34 35 36 37 38 39 Average Std. Dev.

*Not included in average

621 34

Table A18 Individual AS4/F155 Unidirectional Composite Axial Compression Test Results at the Room Temperature, Dry Condition Fiber Sizing Uns ized

Specimen No. AGRX 00 01 02 03 04 05 06 07 08 09 Average Std. Dev.

EPON 828

Compressive Strength (MPa) (ksi)

545 55

79 8

Average 676 Std. Dev. 28

98 4

AGRX 10 11 12 13

14 15 16 17 18 19

PVA

AGRX 20 21 22 23 24 25 26 27 28 29

462 552 572 524 565 593 621 524 496 586

Average 552 Std. Dev. 48

80 7

Compressive Modulus (GPa) (Msi)

Ultimate Strain (percent)

Table A18

Fiber Sizing Polysulfone

Continued

Specimen No.

Compressive Strength ( M P ~ ) (ksi)

AGRX 30 31 32 33 34 35 36 37 38 39

600 634 641 600 621 552 565 627 648 600

87 92 93 a7 90 80 82 91 94 87

Average 607 Std. Dev. 34

88 5

*Not included in average

Ultimate Compressive Modulus Strain (GPa) ( ~ s i ) (percent) 81" 84 93 84 85 109" 92 101 97 117"

11.7* 12.2 13.5 12.7 12.4 15.8* 13.4 14.6 14.0 16.9"

0.79 0.75 0.72 0.73 0.78 0.63 0.65 0.61 0.69 0.59

91 7

13.2 1 .O

0.69 0.07

Table A19 Individual AS4/F155 Unidirectional Composite Axial Compression Test Results at the Elevated Temperature, Wet Condition (38"C, li;',~) Fiber Sizing Uns ized

Specimen No.

Compressive Strength (ma) (ksi)

AGEX 00 01 02 03 04 05 06 07 08 09 Average 406 Std. Dev. 30

EPON 828

59 4

53 5

7.7 0.8

0.70 0.09

71 4

69 4

10.0 0.6

0.69 0.02

AGEX 10 11 12 13 14 15 16 17 18 19 Average 486 Std. Dev. 24

PVA

Compressive Ultimate Modulus Strain ( G P ~ ) ( ~ s i ) (percent)

AGEX 20 21 22 23 24 25 26 27 28

Table A19

Fiber Sizing P VA

Polysulfone

Continued

Specimen No.

Compressive Strength ( M P ~ ) (ksi)

AGEX 29

35 2

51

Average Std. Dev.

354

51 2

AGEX 30 31 32 33 34 35 36 37 38 39

Average Std. Dev.

*Not included in average

16

Compressive Ultimate Modulus Strain ( G P ~ ) ( ~ s i ) (percent) 69

10 . O

0.66

Table A20 Individual AS4/3501-6 Quasi-Isotropic Laminate Axial Tensile Test Results at the Room Temperature, Dry Condition Fiber Sizing Uns ized

EPON 828

PVA

Specimen No .

Tensile Strength ( M P ~ ) (ksi)

AIRY 00 01 02 03 04

405 376" 510" 492 476

Average 471 Std. Dev. 46

68 7

AIRY 10 11 12 13 14

469 427 416 416 425

68 62 60 60 62

Average 430 Std. Dev. 22

62 3

AIRY 20 21 22 23 24

24" 62

162" 430 39 9

410 438

Average 421 Std. Dev. 21 Polysulfone

59 55" 74 71 69

AIRY 30 31 32 33 34 35 Average Std. Dev

*Not included in average

'

58 59

64 61 3

Tensile Ultimate Modulus Strain ( G P ~ ) ( ~ s i ) (percent)

T a b l e A21 I n d i v i d u a l AS413501-6 Q u a s i - I s o t r o p i c Laminate A x i a l T e n s i l e T e s t R e s u l t s a t t h e E l e v a t e d T e m p e r a t u r e , Wet C o n d i t i o n (93OC, 1 % ~ )

3iber Sizing Unsized

PVA

Polysulfone

Specimen No.

Tensile Strength (MPa) (ksi)

AIEY 00 01 02 03 04

197* 463 350" 442 448

29" 67 5 l* 64 65

Average S t d . Dev.

451 11

AIEY 10 11 12 13 14 15

Tensile Modulus ( G P ~ ) (tlsi)

Ultimate Strain (percent)

42 39

6.1 5.7

0.47" 1.21

44 43

6.4 6.2

1.06 1.21

65 2

42 2

6.1 0.3

1.16 0.08

467 49 4 343" 475 487

68 72 50" 69 71

&1 44 5 7* 43 41

5.9 6.3 8.2" 6.3 6.0

1.30 1.18

-

1.46" 0.98 1.02

Average S t d . Dev.

481 12

70 2

42 1

6.1 0.2

1.12 0.15

AIEY 20 21 22 23 24

436 263* 121" 414 423

63 38" 18* 60 61

34 39 40 37 37

5.0 5.6 5.8 5.4 5.3

1.36

1.32 1.43

Average S t d . Dev.

424 11

62 2

37 2

5.4 0.3

1.37 0.06

AIEY 30 31 32 33 34 35

447 515 477 466 450 488

65 75 69 68 65 71

43 43 42 41 43 42

6.2 6.2 6.1 6.0 6.2 6.2

1.38 1.27 1.15 1.16 1.09 1.19

Average S t d . Dev.

474 25

69 4

42 1

6.2 0.1

1.21 0.10

*Not i n c l u d e d i n a v e r a g e

-

-

-

-

-

-

-

-

'Table A22 Individual AS4/4001 Quasi-Isotropic Laminate Axial Tensile Test Results at the Room Temperature, Dry Condition

Fiber Sizing

Uns ized

EPON 828

PVA

Polysulfone

Specimen No.

Tensile Strength (Pipa) (ksi)

AIRZ 00 01 02 03 04

440" 398 370 339 308"

64" 58 54 49 45*

42* 40 32 32 33

6.0* 5.7 4.7 4.6 4.8

-

Average S t d . Dev.

369 30

54 5

34 4

5.0 0.5

1.03 0.06

AIR2 10 11 12 13 14

312 305 319 342 309

45 44 46 50 45

27 28 30 32 30

4.0 4.1 4.4 4.6 4.3

1.15 1.10 1.07 1.08 1.05

-

Average Std. Dev.

317 15

46 2

29 2

4.3 0.3

1.09 0.04

AIRZ 20 21 22 23 24

293 293 314 301 3 15

43 43 46 44 46

27 28 27 28 25

3.9 4.0 3.9 4.0 3.7

1.09 1.01 1.16 1.08 1.24

-

Average S t d . Dev.

303 11

44 2

27 1

3.9 0.2

1.11 0.09

AIRZ 30 31 32 33 34

404 448 425 445 436

59 65 62 65 63

38 37 35 36 36

5.5 5.3 5.1 5.2 5.3

1.11 1 .20 1.26 1.27 1.21

-

Average 432 Std.Dev. 18

63 3

36 1

5.3 0.1

1.21 0.06

*Not included in average

.

Tens ile Modulus (GPa) (Msi)

Ultimate Strain (percent)

1.06 1.03 1.18" 1.07 0.94

Table A23 Individual AS4/4001 quasi-Isotropic Laminate Axial Tensile Test Results at the Elevated Temperature, Wet Condition (93"C, 1 % ~ ) r'iber Sizing Uns ized

EPON 828

Polysulfone

Specimen No.

Tensile Strength (ma) (ksi)

AIEZ 00 01 02 03 04 05

1789 532 485 442 418 447

Tensile Ultimate ilodulus Strain ( G P ~ ) ( ~ s i ) (percent)

26* 77 70 64 61 65

22*

45

3.2* 6.6 6.4 6 .O 5.9 6.5

465 Average Std. Dev. 44

67 6

43, 2

6.2 0.3

1.12 0.06

AIEZ 10 11 12 13 14 15

445 518 485 401 452 436

65 75 70 58 66 63

39 44 41 38 39 39

5.7 6.3 6.0 5.5 5.7 5.7

1.15 1.15 1.24 1.07 1.17 1.15

Average Std. Dev.

456 41

66 6

40 2

5.8 0.3

1.16 0.05

Average Std. Dev.

452 35

66 50

37 1

5.4 0.2

1.27 0.09

AIEZ 30 31 32 33 34

596 618 603 598 613

86 89 88 89 a7

46 49 48 48 48

6.6 7 .O 7.0 7.0 7.0

1.44 1.33 1.34 1.40 1-27

45 44 41 41

0.33" 1.20 1.13 1.14 1.06 1.05

-

Table .A23

Fiber Sizing Polysulfone

Continued

-

Specimen No.

Tensile Strength ( M P ~ ) (ksi)

A I E Z 35

563

82

44

6.4

1.39 -

Average S t d . Dev.

598

87

47

19

3

2

6.8 0.3

1.36 0.06

*Not included in average

Tensile Modulus (GPa) (~si)

Ultimate Strain (percent)

Individual ~ ~ 4 / F 1 5Quasi-Isotropic 5 Laminate Axial Tensile Test Results at the Room Tsmperature, Dry Condition Fiber Sizing Uns ized

Specimen No.

AIRX 00 01 02 03 Aver age Std. Dev.

EPON 828

AIRX 10 11 12 13 14

Average Std. Dev.

PVA

AIRX 20 21 22 23 24

Average Std. Dev. Polysulfone

ALRX 30 31 32 33 34 Average Std. Dev.

Tensile Strength (MPa) (ksi)

Tensile Modulus (GP~) ( ~ s i )

Ultimate Strain (percent)

Individual AS4/F155 Quasi-Isotropic Laminate Axial Tensile Test Results at the Elevated Temperature, Wet Condition ( 3 8 " ~ ,~ X M ) Fiber Sizing Uns ized

EPON 828

PVA

Polysulfone

Specimen No.

AIEX 00 01 02 03 04

Tensile Strength ( M P ~ ) (ksi) 95" 195 268 306 274

14* 43 39

44 40

Tensile Modulus (GPa) (Msi)

Ultimate Strain (percent)

8* 21 20 23 21

1.2" 3.0 2.9 3.3 3.0

1.13 1.41 1.28 1.37 1.32

286 Average Std.Dev. 18

42 3

21 1

3.1 0.2

1.30 0.11

ALEX 10

370

11 12 13 14

403 351 382 389

54 58 51 55 56

30 31 28 28 32

4.3 4.5 4.1 4.1 4.6

1.16 1.23 1.24 1.34 1.18

Average 379 Std. Dev. 20

55 3

AIEX 20 21 22 23 24

376 390 353 350 377

55 57 51 51 55

Average 369 Std.Dev. 17

54 3

AIEX 30 31 32 33 34

44* 50 54 58 59

303* 345 3 72 399

405

Average 380 Std. Dev. 28

*Not included in average

55 4

T a b l e A26 I n d i v i d u a l AS413501-6 Q u a s i - I s o t r o p i c Laminate A x i a l Compression T e s t R e s u l t s a t t h e Room T e m p e r a t u r e , Dry C o n d i t i o n Fiber Sizing Uns i z e d

EPON 828

Polysulfone

Specimen No.

compressive Strength ( M P ~ ) (ksi)

AHRY 00 01 02 03 04 05

102" 313 290 354 414" 252"

15" 45 42 51 60" 3 7*

37 33 39 60" 44" 35

5.3 4.7 5.7 8.7" 6.4* 5.1

0.90 2.90" 1.19 0.75" 1.74 1.45

Average S t d . Dev.

319 32

46 5

38 5

5.5 0.7

1.32 0.35

AHRY 10 11 12 13 14

323 346 396 409 365

47 50 58 59 53

54 60 56 53 40"

7.9 8.8 8.2 7.7 5.8"

1.45 0.70 2-85" 1.45 0.67 -

Average S t d . Dev.

368 35

53 5

56 3

8.1 0.5

1.07 0.44

AHRY 20 21 22 23 24

3 24 363 363 332 401

47 53 53 48 58

49 35" 524 35" 47

7 .O 5.1" 7.5" 5.1" 6.8

1.30* 1.15 0.68* 1.07 1.05 -

Average S t d . Dev.

356 30

52 4

48 1

6.9 0.2

1.09 0.06

AHRY 30

359 394 3 75 408 376

52 57 54 59 55

42 56 49

6.1 8.1 7,1

1.31 1.28 0.75" 3.09*

72"

10.4"

383 19

56 3

49 7

7.1 1. O

31 32 33 34 Average S t d . Dev.

*Not i n c l u d e d i n a v e r a g e

Compressive Ultimate Modulus Strain (GPa) ( ~ s i ) (percent)

-

-

-

1.30 0.21

Table A27 Individual AS4/3501-6 Quasi-Isotropic Laminate Axial Compression Test Resu.lts at the Elevated Temperature, Wet Condition (93"C, 1%M) Fiber Sizing Unsized

EPON 828

Compressive Modulus (GPa) (Msi)

Ultimate Strain (percent)

Specimen No.

Compressive Strength (MPa) (ksi)

AHEY 00 01 02 03 04

294 306 299 285 297

43 44 43 41 43

32" 37 42

4.7" 5.4 6.1

42

6,l

296 Average Std. Dev. 8

43 1

40 3

0.4

0.87 0.14

34 30 27" 39" 29

31 36* 34 21* 25

4.5 5.3* 4.9 3.1" 3.6

0.92 0.75 0.71 1.394 0.83

Average 213 Std. Dev. 18

31 3

30 5

4.3 0.7

0.80 0.09

AHEY 30 31 32 33 34

282 278 300 305 303

41 40 44 44 44

40 32 35 36 35

5.9 4.6 5.0 5.2 5 .O

0.82 1.02 1.11 0.78 -.0.96

294 Average 13 Std. Dev.

43 2

35 3

5.1 0.5

0.93 0.10

-

-

5.9

0.79 1.03 1.05" 0.67" 0.80

AHEY 10 11 12 13 14 15 Average Std. Dev.

PVA

Polysulfone

AHEY 20 21 22 23 24

*Not included in average

233 206 184* 265" 199

Table A28 Individual AS414001 Quasi-Isotropic Laminate Axial Compression Test Results at the Room Temperature, Dry Condition Fiber Sizing

Specimen No.

Compressive Strength (MP~)

Uns ized

AHRZ 00 01 02 03 04 05 Average Std. Dev.

EPON 828

AHRZ 10 11 12 13 14 15 Average S t d Dev.

PVA

AHRZ 20 21 22 23 24 Average Std. Dev.

Polysulfone

AHRZ 30 31 32 33 34 Average Std. Dev.

*Not included in average

(ksi)

Compressive Hodulus (GPa) (Msi)

Ultimate Strain (percent)

Table A29 Individual AS4/4001 Quasi-Isotropic Laminate Axial Compression Test Results at the Elevated Temperature, Wet Condition (93"C, l%H) Fiber Sizing Uns ized

Compressive Strength ( M P ~ ) (ksi)

Specimen No.

332 341 352 330 332

48 49 51 48 48

27 31 35 34 33

3.9 4.6 5.1 4.9 4.8

1.30 1.48 1.61 0.89" 1.24 -

337 Average 9 Std. Dev.

49 1

32 3

4.7 0.5

1.41 0.17

AHEZ 10 11 12 13 14

51 52 54 47 53

27"

4.0" 6.6 5.1 7.3" 5 .O

1.15 0.91 1.40 0.70 1.24

AHEZ 00

.

01 02 03 04

EPON 828

Average Std. Dev. PVA

AHEZ 20

21 22 23 24 25 Average Std. Dev. Polysulfone

Compressive Ultimate Modulus Strain (GP~) ( ~ s i ) (percent)

AHEZ 30 31 32 33 34 35 Average Std. Dev.

*Not included in average

352 359 374 325 367

46 35 51" 35

Individual AS41F155 Quasi-Isotropic Laminate Axial Compression Test ~esultsat the Room Temperature, Dry Condition Fiber Sizing Uns ized

Specimen No. AHRX 00 01 02 03

04 05 Average Std. Dev EPON 8 2 8

AHRX 10 11 12 13

14 15 Average Std. Dev. PVA

AHRX 20 21 22 23 24 25

Average Std. Dev. Polysulfone

AHRX 30 31 32 33 34 Average Std. Dev

*Not included in average

Compressive Strength (ma) (ksi)

Compressive Modulus ( G P ~ ) (Msi)

Ultimate Strain (percent)

Table A31 Individual AS4/F155 Quasi-Isotropic Laminate Axial Compression Test Results at the Elevated Temperature, Wet Condition (38"C, 1 % ~ ) Fiber Sizing

Specimen No.

Compressive Strength

Compressive I.lodulus

Ultimate Strain

2 Uns ized

AHEX 00

123 139 136 142 136

18 20 20 21 20

Average 135 Std. Dev. 7

20

AHEX 10

181 173 173 199 199 169

26 25 25 29 29 25

Average 182 S t d . D e v . 13

27 2

Average 154 Std. Dev. 8

22 1

AHEX 30

23 22 24 24

01 02 03 04 05

EPON 828

11 12 13 14 15

-

-

1

PVA

Polysulfone

31 32 33

159 154 163 165

T a b l e A31

Fiber Sizing

Polysulfone

Continued

-

Specimen No.

Compressive Strength ( M P ~ ) (ksi)

AHEX 34 35

172 168

25 24

26 20

Average S t d . Dev.

163

24 1

24

3.5

3

0.4-

*Not i n c l u d e d i n a v e r a g e

7

Compressive Ultimate Modulus Strain (GPa) ( ~ s i ) (percent) 3.8 2.9

1. O O 1.68

1.26 0.40

Table A32 Individual AS4/3501-6 Quasi-Isotropic Laminate Flexural Test Results at the Room Temperature, Dry Condition Fiber Sizing

Flexural Strength (Ma) (ksi)

Flexural Modulus (GPa) (Msi)

934 894 863 851 757

136 130 125 123 110

56.4 56.3 56.6 58.4 46.0

8.19 8.16 8.21 8.47 6.68

1.66 1.59 1.52 1.46 1.64

Average 860 S t d . D e v . 69

125 10

54.7 5.0

7.94 0.72

1.57 0.08

AJRY 10 11 12 13 14

909 881 970 761 887

132 128 141 110 129

56.7 63.5 62.0 55.5 62.8

8.22 9.21 8.99 8.05 9.11

1.60 1.39 1.56 1.37 1.41

Average 882 Std. Dev. 76

128 11

60.1 3.7

8.72 0.54

1.47 0.11

AJRY 20 21 22 23 24

762 818 820 812 881

111 119 119 118 128

47.0 52.5 48.8 47.8 53.1

6.82 7.62 7.08 6.93 7.71

Average 818 Std. Dev. 42

119 6

49.8 2.8

7.23 0.41

1.64 0.06

AJRY 30 31 32 33 34

1003 904 852 956 999

145 131 124 139 145

64.7 56.7 54.0 59.2 61.5

9.38 8.23 7.83 8.58 8.92

1.55 1.59 1.58 1.62 1.62

Average 943 Std. Dev. 65

137 9

59.2 4.1

8.59 0.60

1.59 0.03

Specimen No.

Unsized

AJRY 00 01 02 03 04 *

EPON 828

Polysulfone

Flexural Strain (percent)

'

1.62 1.56 1.68 1.70 1.66 -

'Table A33 I n d i v i d u a l AS4/3501-6 Q u a s i - I s o t r o p i c Laminate F l e x u r a l T e s t R e s u l t s a t t h e E l e v a t e d Temperature, Wet C o n d i t i o n (93"C, 1%M) Fiber Sizing Unsized

EPOiO 828

PVA

Specimen No.

Flexural Strength (MPa) (ksi)

Flexural Flexural Modulus Strain (GPa) ( ~ s i ) (percent)

AJEY 00 01 02 03 04

827* 625 534 509 526

120" 91 77 74 76

98.6* 54.7 51.2 50.5 60.7

14.30" 7.93 7.43 7.32 8.81

0.84" 1.14* 1.04 1.01 0.87

Average S t d . Dev.

548 52

80 8

54.3 4.7

7.87 0.68

0.97 0.09

AJEY 1 0 11 12 13 14

480" 636 679 452* 636

70* 92 99 66* 92

61.4 60.1 58.5 44.8* 55.8

8.90 8.71 8.48 6-50" 8.09

0.78" 1.06 1.16 1.01 1.14

Average Std.Dev.

651 25

94 4

AJEY 20

383* 5 17 57 0 5 19 515

56* 75 83 75 75

Average S t d . Dev.

530 27

77 4

AJEY 30 31 32 33 34

7 12 598 599 590 625

103 87 87 86 91

Average S t d . Dev.

625 50

91 7

21 22 23 24

Polysulfone

*Not i n c l u d e d i n a v e r a g e

'Table A34 Individual AS4/4001 Quasi-Isotropic Laminate Flexural Test Results at the Room Temperature, Dry Condition

Fiber Sizing Uns ized

Specimen No.

Flexural Strength (ma) (ksi)

Flexural Flexural Modulus Strain ( G P ~ ) ( ~ s i ) (~ercent)

AJRZ 00 01 02 03 04

967 1019 971 885 970

140 148 141 128 141

60.0 68.9 65.7 72.7 68.8

8.70 9.99 9.53 10.55 9.98

-

963 48

140 7

67.2 4.7

9.75 0.69

1.44 0.14

973 1060" 783" 990 9 27

14 1 154" 114* 144 134

70.0 73.5 47.4" 66.2 60.1

10.15 10.66 6.88* 9.61 8.72

1.39 1.44 1.65 1.49 1.54

-

Average Std. Dev. EPON 828

PVA

AJRZ 10 11 12 13 14 Average Std. Dev.

963 33

140 5

67.5 5.7

9.78 0.83

1.50 0.10

A J R Z 20 21

85 1 810 834 866 814

123 117 12 1 126 118

56.1 50.7 53.6 53.0 52.0

8.14 7.36 7.78 7.68 7.54

1.52 1.60 1.55 1.63 1.56

-

83 5 21

121 3

53.1 2.0

7.70 0.29

1.57 0.04

AJRZ 30 31 32 33 34

1114 996 1044 1032 992

162 145 152 150 144

69.5 65.0 67.1 67.1 65.6

10.08 9.42 9.73 9.10 9.52

1.60 1.53 1.56 1.64 .1 . 5 1

Average S t d . Dev.

1035 49

150 7

66.0 2.5

9.57 0.36

1.57 0.05

22 23 24

Average Std. Dev. Polysulfone

.

1.61 1.48 1.48 1.22 1.41

*Not included in average

T a b l e A35 I n d i v i d u a l AS4/4001 Q u a s i - I s o t r o p i c Laminate F l e x u r a l T e s t R e s u l t s , Condition a t t h e E l e v a t e d ~ e m ~ e r a t u r eMet (93"C, l%iO

Fiber Si z i n g

Uns i z e d

Specimen No.

Flexural Strength ( M P ~ ) (ksi)

Flexural Modulus (GPa) (14si)

AJEZ 00

475" 711 734 743 683

69" 103 107 108 99

39.7" 57.8 67.2 72.5 67.2

5.76* 8.39 9.75 10.52 9.75

Average S t d . Dev.

718 28

104 4

66.2 6.1

9.60 0.89

AJEZ 10 11 12 13 14

645 622 704 714 770

94 90 102 104 112

51.7 48.0 54.1 53.2 56.9

7.50 6.96 7.84 7.71 8.25

Average S t d . Dev.

691 62

100 9

52.8 3.3

AJEZ 20

709 670 668 620 67 5

103 97 97 90 98

59.4 59.4 53.7 53.9 60.1

8.62 8.62 7.79 7.82 8.71

Average S t d . Dev.

668 35

97 5

57.3 3.2

8.31 0.46

AJEZ 30

827 755 892 88 1 884

120 114 129 128 --128

69.2 70.9 80.6 74.8 78.8

10.03 10.28 11.69 10.85 11.43

854 48

124 7

74.9 4.9

10.86 0.71

01 02 03 04

EPON 828

PVA

21 22 23 24

Polysulfone

31 32 33 34 Average S t d . Dev.

*Not i n c l u d e d i n a v e r a g e

-

7.65 0.47

Flexural Strain (percent)

Table A36 Individual AS4/F155 Quasi-Isotropic Laminate Flexural Test Results at the Room Temperature, Dry Condition Fiber Sizing Uns ized

EPON 828

PVA

Specimen No. ,

Flexural Strength ( M P ~ ) (ksi)

Flexural Flexural Modulus Strain (GPa) (~si) (~ercent)

AJRX 00 01 02 03 04

548 592 613 548 615

79 86 89 80 89

30.4 31.9 34.7 23.5" 32.5

4.42 4.63 5.03 3.41" 4.71

1.80 1.85 1.77 2.33" 1.89 -

Average 583 Std. Dev. 34

85 5

32.4 1.8

4.70 0.25

1.83 0.05

719 609 654 693

104 88 95 101

47.7 37.0 35.4 50.7"

6.91 5.37 5.13 7.36"

1.51 1.64 1.85" 1.37"

Average 669 Std.Dev. 48

97 7

40.0 6.7

5.80 0.97

1.58 0.09

654 643 703 602 684

95 93 102 87 99

44.2 39.6 41.8 32.0" 43.6

6.41 5.74 6.06 4.64" 6 -32

1.48 1.62 1.68 1.88 1.57 -

Average 658 Std. Dev. 38

95 6

42.3 2.1

6.13 0.30

1.65 0.15

84

AJRX 10 11 12 13

AJRX 20

\

Polysulfone

21 22 23 24

AJRX 30

577 688 665 649 678

100 97 94 98

29.8" 40.6 40.8 34.6 41 .,7

4.33" 5.90 5.92 5.02 6.05

1.93 1.69 1.63 1.87 1.62 -

Average 651 Std. Dev. 44

94 6

39.4 3.3

5.71 0.47

1.75 0.14

31 32 33 34

*Not included in average

Table A37 Individual AS4/F155 Quasi-Isotropic Laminate Flexural Test Results at the Elevated Temperature, Wet Condition (38"C, 1%M) Fiber Sizing Uns ized

EPON 828

PVA

Polysulfone

Specimen No.

Flexural Strength ( M P ~ ) (ksi)

Flexural Hodulus (GPa) (Msi)

AJEX 01 02 03 04

87" 369 374 371

13* 54 54 54

26.3 22.8 27.2

3.82 3.30 3.95

1.40 1.65 1,36

Average 371 Std. Dev. 3

54 0

25.4 2.0

3.69 0.34

1.47 0.16

AJEX 10 11 12 13 14

482 446 494 471 467

70 65 72 68 68

41.5 37;7 42.5 42.7 40.9

6.02 5.47 6.17 6.19 5.93

1.16 1.18 1.16 1-10 1.15 -

Average 472 Std. Dev. 18

69 3

41.1 2.0

5.96 0.29

1.15 0.03

AJEX 20 21 22 23 24

365 348 401 320 386

53 50 58 46 56

35.5 29.3 34.5 33.0 34.3

5.15 4.25 5.01 4.79 4.97

1.03 1.19 1.16 0.97 1.12 -

Average 364 Std. Dev. 32

53 5

33.3 2.4

4.83 0.35

1.09 0.09

AJEX 30 31 32 33 34

390 426 440 364 416

57 62 64 53 60

42.0 33.1 39.6 34.7 37.0

6.09 4.80 5.74 5.03 5.36

0.93" 1.29* 1.11 1.05 1.13 - .

Average 407 Std.Dev. 30

59 4

37.2 3.6

5.40 0.52

1.10 0.04

*Not included in average

-

-

Flexural Strain (percent

-

T a b l e A38 I n d i v i d u a l AS413501-6 q u a s i - I s o t r o p i c Laminate I n t e r l a m i n a r S h e a r T e s t R e s u l t s a t t h e Room Temperature, Dry C o n d i t i o n

Fiber Sizing

Specimen No.

Unsized

AKRY 00 01 02 03 04

Average S t d . Dev

EPON 828

AKRY 10 11 12 13 14

Average S t d . Dev.

PVA

AKRY 20 21 22 23 24

Average S t d . Dev.

Polysulfone

AKRY 30 31 32 33 34

Average S t d . Dev.

Shear S t r e n g t h ( M P ~ ) (ksi)

30 29 29 33 28 -

4.3 4.2 4.2 4.8 4 .1 -

Table A39 Individual AS4/3501-6 Quasi-Isotropic Laminate Interlaminar Shear Test Results at the Elevated Temperature, Wet Condition (93OC, 1%M) ,Fiber Sizing Unsized

Specimen No.

AKEY 00 01 02 03 04 Average Std. Dev.

EPON 828

AKEY 10 11 12 13 14 Average Std. Dev.

AKEY 20 21 22 23 24 Average Std. Dev. Polysulfone

AKEY 30 31 32 33 34 Average Std. Dev.

lot included in average

Shear Strength (MPa) (ksi)

Individual AS4/4001 4uasi-Isotropic Laminate Interlaminar Shear Test Results at the Room Temperature, Dry Condition Fiber Sizing Uns ized

Specimen No. AKRZ 00 01 02 03 04 05 Average Std. Dev.

EPON 8 2 8

AKRZ 10 11 12

13 14 Average Std. Dev PVA

AKRZ 20 21 22 23 24

Average Std. Dev. Polysulfone

AKRZ 3 0 31 32 33

34

Average Std. Dev

*Not included in average

Shear Strength (ma) (ksi)

'Table A41 Individual AS4/4001 Quasi-Isotropic Laminate Interlaminar Shear Test Results at the Elevated Temperature, Wet Condition (93"c, 1 % ~ )

Fiber Sizing Uns ized

Specimen No. AKEZ 00

01 02 03 04 Average Std. Dev EPON 828

AKEZ 10

11 12 13 Average Std. D e v . AKEZ 20 21 22 23 Average Std. Dev. Polysulfone

AKEZ 30 31 32 33 34 Average Std. Dev.

Shear Strength (ma) (ksi)

Table A42 Individual AS4/F155 Quasi-Isotropic Laminate Interlaminar Shear Test Results at the Room Temperature, Dry Condition Fiber Sizing Uns ized

Specimen No.

Shear Strength (MPa) (ksi)

AKRX 00 01 02 03 04

59 53 57 63 62 -

Average Std. Dev EPON 8 2 8

AKRX 1 0 11 12 13 14 Average Std. Dev.

PVA

AKRX 20 21 22 23 24

Average Std. Dev. Polysulfone

AKRX 3 0 31 32 33 34 Average Std. Dev.

8.6

7.7 8.3

9.2 9.0

-

Individual AS4/F155 Quasi-Isotropic Laminate Interlaminar Shear Test Results at the Elevated Temperature, Wet Condition (38"C, 1 % ~ ) Fiber Sizing Uns ized

Specimen No. --AKEX 01 02 03

04 Average Std. Dev. E P O N 828

AKEX 10 11 12 13 14 Average Std. Dev.

Average Std. Dev. Polysul £one

AKEX 30 31

32 33 34 Average Std. Dev

*Not included in average

Shear Strength (MP~) (ksi)

Table A44 Individual AS4/3501-6 Quasi-Isotropic Laminate Instrumented Tensile Impact Test Results at the Room Temperature, Dry Condition Fiber Sizing Uns ized

Specimen No. ALRY 00 02 03 Average Std. Dev.

EPON 828

ALRY 10 11 12 13 Aver age Std. Dev.

PVA

ALRY 20 21 22 23 24

Aver age Std. Dev.

Ultimate Strength ( M P ~ ) (ksi)

Dynamic Modulus (GPa) (~si)

.

Total Energy

(k~/rn~ )

(ft-lb/in3 )

T a b l e A44

- Continued Fiber Sizing

Polysulfone

Specimen No.

ALRY 30

31 32 33 34 Average S t d . Dev.

Ultimate Strength (FIpa) (ksi)

44 1 400 414 358 421

64.0 58.0 60.0 52.0 61.0

40 7 31

59.0 4.5

-

Dynamic Modulus ( G P ~ ) (Msi)

T o t a l Energy (k~/m ) ~ (ft-lb/in3 )

Table A45 Individual AS4/3501-6 Quasi-Isotropic Laminate Instrumented Tensile Impact Test Results at the Elevated Temperature, Wet Condition (93"C, 1%M) Fiber Sizing Uns ized

Specimen No.

Ultimate Strength (MP~) ( k s i )

Dynamic Modulus (GP~) ( ~ s i )

Total Energy (kJ/m 3,

( f t-lb/ in 3,

1484 585

33.0 3.0

ALEY 00 01 02 03 Average Std. Dev.

EPON 828

ALEY 12 13 Average Std. Dev.

ALEY 20 21 22 Average Std. Dev.

374 132

54.3 19.1

31 -

4.6 -

Table A46 Individual AS4/4001 Quasi-Isotropic Laminate Instrumented Tensile Impact Test Results at the-Room Temperature, Dry Condition Fiber Sizing

EPON 828

Specimen No. ALRZ 10 11 12 13 14 Average Std. Dev.

Polysulfone

ALRZ 30 31 32 33 34 Average Std. Dev.

Ultimate Strength (i+~a) (ksi) 352 414 393 400 365

51 .O 60.0 57.0 58.0 53.0

Dynamic Modulus (GPa) (Msi) 35 32 39 32 32

5.1 4.6 5.6 4.7 4.7

Total Energy ( k ~ / )m ~ (ft-lb/in3 )

1259 1439 1124 1034

23.0 32 . O 25 .O 23 . O

Table A47 Individual AS4/??155 Quasi-Isotropic Laminate Instrumented Tensile Impact Test Results at the Room Temperature, Dry Condition Fiber Sizing Uns ized

Specimen No. ALRX 01 02 03

PVA

Dynamic lilodulus (GP~) (~si)

Total Energy ( k ~ / >m ~ ( f t-lb/in3 )

253 232 317 297

36.6 33.7 46.0 43 .O

21 19 24 22

3.0 2.7 3.5 3.2

765 945 1214 1079

17 .O 21 .O 27 .O 24.0

Aver age Std. Dev.

276 39

40 .O 5.7

21 3

3.0 0.4

989 180

22 .O 4.0

ALRX 10 11 12 13 14 15

379 379 352 310 221 365

55.0 55 .O 51 .O 45.0 32 .O 53 .O

26 37 32 32 30 26

3.8 5.4 4.6 4.7 4.4 3.8

1304 1349 945 720 495" 1349

29 .O 30.0 21 .O 16.0 11 .O* 30.0

Average Std. Dev.

334 61

48.5 8.9

30 4

4.4 0.6

1133 287

25.2 6.4

ALRX 20

359 359 372 352 365

52.0 52.0 54.0 51 .O 53.0

37 20 35 38 35

5.3 2.9 5.1 5.5 5 .O

1034 1484 1259 1079 989

23.0 33.0 28.0 24.0 22.0

361 8

52.4 1.1

33 8

4.8 1.1

1169 225

26.0 5.0

04

EPON 828

Ultimate Strength (ma) (ksi)

21 22 23 24

Average Std. Dev.

4 ([I

U

0

-I

h

a, d

n

([I

E-l

U I ,-I 4

*u-,aa&

G A

m m m m m

m

0 4 c V m u m m m m m

aJ

= h)

bO FI ([I

T a b l e A49 I n d i v i d u a l AS4/3501-6 S i n g l e F i b e r P u l l o u t T e s t R e s u l t s Fiber Sizing

Specimen No.

Fiber Diameter (pm)

Unsized

PVA

Polysulfone

(1r4in)

Embedded Length (mm)

(MP~)

(ksi)

-

55* 36

-

7.9" 5.2

AFRY 01 02 03 04 05 06

7.4 8.6 7.9 8.6 8.6 8.6

2.9 3.4 3.1 3.4 3.4 3.4

109 89 91

4.3 3.5 3.6

26 37 21*

3.7 5.3 3.1"

Average S t d . Dev.

8.4 0.5

3.3 0.2

94 8

3.7 0.3

33 6

4.7 0.9

AERY 20 21 22 23

7.9 9.7" 6.9 7.4

3.1 3.8* 2.7 2.9

130 173" 104" 135

5.1 6.8* 4 . l* 5.3

36 19" 34 28

5.2 2.7" 4.9 4.0

Average S t d . Dev.

7.4 0.5

2.9 0.2

132 4

5.2 0.1

32 4

4.7 0.6

AERY 30 31 32 33

8.6 7.4 8.6 8.6

3.4 2.9 3.4 3.4

58" 97 71 84

2.3" 3.8 2.8 3.3

45 43 41 37

6.5 6.3 5.9 5.4

Average S t d . Dev.

8.3 0.6

3.3 0.3

84 13

3.3 0.5

42 3

6.0 0.5

*Not i n c l u d e d i n a v e r a g e

94 91

(lv3in)

Interfacial Shear S t r e n g t h

-

3.7 3.6

-

'Table A50 I n d i v i d u a l ~ ~ 4 / 4 0 0S1i n g l e F i b e r P u l l o u t T e s t R e s u l t s

Fiber Sizing

Specimen No.

Fiber Diameter (pa)

Unsized

PVA

Polysulfone

AERZOO 01 02 03

Embedded Length

( 1 0 - ~ i n ) (mm)

(10-~in)

Interfacial Shear S t r e n g t h

(ma)

(ksi)

10.2" 8.6 8.6 7.9

4.0" 3.4 3.4 3.1

173 218 86" 211

6.8 8.6 3.4" 8.3

18 19 37" 24

2.6 2.7 5.3 3.5

Average S t d . Dev.

8.4 0.4

3.3 0.2

20 1 24

7.9 1.0

20 3

2.9 0.5

AERZ 20 21 22 23

8.6 9.7 9.7 7.4"

3.4 3.8 3.8 2.9"

196 185 66" 127

7.7 7.3 2.6* 5.0

17 16 31" 16

2.5 2.3

Average S t d . Dev.

9.3 0.6

3.7 0.2

169 37

6.7 1.5

16 1

2.4 0.1

AERZ 33

9.7 7.9

3.8 3.1

81 122

3.2 4 . 8-

48 33

6.9 4.8

8.9

3.5

102

4.0

40

5.9

34

Average S t d . Dev.

*Not i n c l u d e d i n a v e r a g e

-

-

-

-

-

4.5" 2.3

-

T a b l e A51 I n d i v i d u a l AS4/F155 S i n g l e F i b e r P u l l o u t T e s t R e s u l t s

Fiber Sizing

Specimen No.

Fiber Diameter (urn)

Polysulfone

(1r4in)

Embedded Length (mm)

Interfacial Shear S t r e n g t h

( l ~ - ~ i n ) (MPa)

(ksi)

AERX 30 31 32 33

8.6 8.6 8.6 8.6

3.4 3.4 3.4 3.4

89 178 79 170

3.5 7.0 3.1 6.7 --

54" 23 23 17

7.8* 3.3 3.4 2.5

Average S t d . Dev.

8.6 0.0

3.4 0.0

130 52

5.1 2.1

21 3

3.1 0.5

*Not i n c l u d e d i n a v e r a g e

APPENDIX B

INDIVIDUAL DATA PLOTS

,i ,

Preceding Page Blank

,,.

---.

.

.-

.

I , . I . -~_NK_J.:.~>:G~

.-I%-,

.-

.

.

.

,5

:.-

2--

:.,

4

. :

-

w,..

.-

- . ,

.

,

N

Neat Resin Uniaxial Tension

1 1 , ; Preceding Page Blank

'

,?:,

R E S TENSION ~ ELV

TEW

F155

OWBGBMAR PAGE 'IS' OF POOR QUALUn

I S Y E X U SHM E L V TEMP, M T 4001

F155 IOSIPESCU SHEAR ROOM T W . DRY

Neat Resin I o s i p e s c u Shear

- ORIGINAL PAGE 8%' OF POOR QUWLIW HERCLES 4681 BISCIALmIDE DRY

Hercules 4001 Bismaleimide Neat Resin Thermal Expansion

-2 LLRYld

m.BSa.s4bTCt)

!m!-

-

-- w e

e z s s e 7 5 f m DO;.

C

F155 E T EPOXY NO

Hexcel F155 Rubber-Toughened Epoxy Neat R e s i n Thermal Expansion

2

-1

-B

NO.

I

I

Neat Resin Moisture Expansion

.

.

..

I

,

,

.

,

T R W TEN TRAN 'EN

R T ,DRY 3501-6 UNSIZED

' 0

TRAN TEN

R T

. DRY

R 7

.DRY

350 1 -6 828

I

350 1 6 PVA

Unidirectional Composite Transverse Tension

T R N TEN

R T ,DRY 35dl-6

?-SkT&

TRAN TEN

ELV W . W E T 3501-6 CINSIZEI)

TRIW TEN

R T .DRY

4 ~ x 3 1828

TRAN TEN

ELV TEMP .WET 4001 PVA

i7 T .DRY F155 MIZm

TRAN

' '

!

f

"

'

"

-

P

I

TRAN

-

EN

R T . D R Y F155 828

75 I0

10

n

4

C1

B

Y,

8

s 25

8 8 0

2 5

5 0 STRLP(

TRAN TEN

7 5

18 8

0

8 8



R T , D R Y F155 PVA

2 5

5 0

STRASN (€43)

TRAN TEN

R T , D R Y F 155 P-SJLFCN

7

5

8

A X N

CMP R

AXIAL

T

.

DRY, 3501 -5.

C W R T ,

U\GIZED

DRY. 3501-6, PVA

' *m

Unidirectional Composite Axial Compression

AXIAL

C W R T

,

DRY, 3501-6.

P-aLFm

ORdGiNAL PAGE F%' OF POOR QUABUm '

A X W COW

AXIAL C O W

E L V TEMP ,NET 3501-6 PVA

AXLAL CDP

ELV TMP ,WET 3501-6 828

ELV TEW M T 3581-6 P-SUFO

A X I A L COW

AXIAL

~

Q

B

R T

,

C W R T

1

,

DRY. 4801

,

.

AXIAL

UNSim

,

,

I

R T

AXIAL C W

DRY, 4001 , PVA

,

R T

~

~

~

~

l1 QB ~

~

~

,

~

,

DRY. 4881, Bts

DRY,

4001. P - W F O N

J

8 75 A

6 I esa

?

8 E

0 88

a

5

18

15

AXIAL CUF

ELV TEW . K T 4881 P - W Q V

A X N C W

R T

.

AXIAL

DRY. F 1 5 5 V d I Z E D

CcUl'

R T

. my. F155.

8t8

W

saa

258

AXIAL

R T , DRY. F 1 5 S . PVA

AXIAL EW

R T

.

DRY, F l 5 5 , P - a F O N

AXIAL C

W

ELV TEW , K T F155 MEED

AXIAL t[EP ELV W

.UET FI 55 P-SULFOJ

Quasi-Isotropic Laminate Axial Tension

s

w CC*)

slum

(CIS)

L M TEN

R T

.DRY 4881 LNSIZED

LM TEN

R . T .CUY 4881 P - W ( T (

LPsr

TEN ELV To9 ,tlET 4881 P-XLFW

LNYTPI R T ,DRY F l S P V A

MTPI R T . W F 1 5 5 P - W

OR2G?.fiA[blPAGE 6%

OE T O O R gUAL!W LAM TEN

ELV T E T ,SET F155 LIFISZiED

LNI

TEN

KV

.WET ~l55 82a

LP*I

l&t

W

R T , DRY, 3501 -6, WA

Quasi-Isotropic Laminate Axial Compression

I&

C119 R T , DCN, 3581-6, 828

CW

R T .

DRI, 35014. P

-

W

LAM t3W

356 1-6 N I Z E D , 2 V T W ,

hEJ

LAM CmP

ELV TEW ,E T 3% 1-6 828

R T , Wf, 4881, 828

IAl

C W R T ,

m.4881,

P-SLfm

LAM aJW

ELV TEHP , K T 4001 828

Q)9

z 3 3 L , , , ,

W4

C W

R

T . ORY. F I B , .

,

, , , ,

R T

,

,

LA^

UFGI2ED

, , , , I

w,FlS,.

PJA

18

IP P.

-I

n

e" 188

e

0

e

s

Ie

IS

C W R T

,

DRY. F I B , , 828

LM W

a V TEMP , K T FISS PVA

LAn FLEX

rea

58

0

Quasi-Isotropic Laminate Flexure

R T ,CRY 35el-6 P-Slum

LAM F E Y

E V

TEW ,WET5 0 1 - 5

LAM DLZY

e

58

,

R

T

tm

,Coy

dm1 829

isa

a3

23

LnM R E X

R T ,WY F155 828

Quasi-Isotropic Laminate Tensile Impact

APPENDIX C

ADDITIONAL PHOTOGRAPHS OF SINGLE FIBER PULLOUT SPECIMEN FRACTURE SURFACES

Specimen AERYO1:

Unsized AS4/3501-6 (320x1

Specimen AERY02:

Unsized AS4/3501-6 (320x1

Specimen AERY03:

Unsized ~ ~ 4 1 3 5 0 1 - (160x1 6

Specimen AERY05:

Unsized AS4/3501-6 (320x1

Specimen AERY06:

Specimen AERY22 :

Unsized AS413501-6 (320x1

PVA-Sized AS4/3501-6 (250X)

Specimen AERY30:

Polysulfone-Sized AS413501-6 (320X)

Specimen AERY33:

Polysulfone-Sized AS413501-6 (320x1

Specimen AERZ02:

Specimen AERZ21:

Unsized AS4/4001 (320x1

PVA-Sized ~ ~ 4 / 4 0 0(320x1 1

Specimen AERZ22:

Specimen AERZ34:

PVA-Sized AS4/4001 (320X)

Polysulfone-Sized AS4/4001 (320x1

Specimen AERX32:

Polysulfone-Sized ~ S 4 / ~ 1 5( 53 2 0 x 1

Specimen AERX33:

Polysulfone-Sized AS4/F155 ( 3 2 0 x 1

APPENDIX D

CHARACTERIZATION OF GRAPHITE FIBER SURFACE COATINGS

-r].--,-..__

f

p.s--?-;

I Preceding Page Blank 4~~ I

--

1

.-,

.-

:--

I, - _.._d

374

._

, I:1

. .

~

L.-,

-.-

: