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
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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 (!@a) (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
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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%.
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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 .
-
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m-
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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
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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
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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
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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
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.,-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
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U
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C a,
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a,
a cn
3
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0 Z
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N
5
L I . a,
>
u u
C cn
ooooooool
0 0
([I
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H b
CI
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d
&
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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
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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
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I S Y E X U SHM E L V TEMP, M T 4001
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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
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