Laminates of Celion/LARC-160, fabricated in thicknesses from 4 to 16 ply and in unidirectional, x-ply and fabric ply configurations, were isothermally aged at temperatures of 204, 260 and 316 C for periods up to 15,000 hours. Weight-loss of the test panels was measured at selected intervals during aging. At the lower aging temperatures, it was observed that panel thickness and ply arrangement influenced the apparent stability: i.e., thicker panels degraded less than thin panels and unidirectional panels degraded less than x-ply or fabric reinforced panels. At higher aging temperatures, all panel configurations and thicknesses converged toward the same behavior

Nelson, James B.

English

NASA Technical Reports Server

NASA Technical Memorandum 100496 1 
EFFECT OF GEOMETRY ON THERMAL AGING BEHAVIOR OF 
C E L I O N / L A R C - 1 6 0  COMPOSITES 
JAMES B I  NELSON 
(BASA-Tfl -1004S4)  E E F f C L  CF' G E C ; E E l B Y  OB 18 9-2 1047 
1bERBAL A G f I i G  B I E I V Z C B  GF CELICL/IABC-lSO 
CCMPUSJlES {IlaZa) 23 F CSCL 11D 
Uoclas 
G3/24 0205364  
DECEMBER 1987 
National Aeronautics and 
Space Administration 
Langley Research Center 
Hampton. Virginia 23665 
https://ntrs.nasa.gov/search.jsp?R=19890011676 2020-03-20T02:35:12+00:00Z
EFFECT OF GEOMETRY ON THERMAL AGING BEHAVIOR OF 
CELION/LARC-160 COMPOSITES 
B Y  
JAMES B. NELSON 
SUMMARY 
Laminates o f  Celion@/LARC-160, fabricated in thicknesses from 4 to 16 
ply and in unidirectional, x-ply and fabric ply configurations, were 
isothermally aged at temperatures of 204, 260 and 316'C for periods up to 
15,000 hours. 
intervals during aging. At the lower aging temperatures, it was observed 
Weight-loss o f  the test panels was measured at selected 
that panel thickness and ply arrangement influenced the apparent stability: 
i.e., thicker panels degraded less than thin panels and unidirectional 
panels degraded less than x-ply or fabric reinforced panels. A t  higher 
aging temperatures, all panel configurations and thicknesses converged 
tovJard the same behavior. 
4 
INTRODUCTION 
The National Aeronautics and Space Administration is currently 
conduct'ng research directed at exploiting the full weight-saving potential 
*Celion is a registered trademark of BASF Structural Material, Inc. 
2 
of composite materidls for a wide range of aerospace structural 
applications. 
for decades and are currently being used in applications requiring long-term 
thermal exposures at temperatures below 177OC. 
composite materials, however, include spacecraft requiring use at 
temperatures up to 316°C for lifetimes up to 100 hours and subsonic and 
future supersonic aircraft applications requiring use at temperatures o f  
170°C t o  260°C for periods of 50,000 t o  70,000 hours. 
Carbon fiber reinforced epoxy composites have Seen studied 
Potential applications for 
Currently, the only readily available composite matrix materials 
suitable for this temperature range i s  the class of addition polyimides 
represented by the NASA-developed PMR-15 and LARC-160 resins. 
stlidies have been made of the long-term thermal stability of these and 
similar materials (refs. 1 to 6). One difficulty in predicting long-term 
stability from accelerated and/or sma 1 scale tests is the effect of  sample 
geometry (ref. 2 ) .  In ref. 2, a dist nct difference between the measured 
stability of small SRS test specimens and larger 6 inch square panels, as 
well as an effect of sample thickness was reported. It was asserted that 
these effects could be observed by monitoring weight loss during thermal 
aging. 
A number of 
This paper reports on a study to further define this effect of geometry 
on the apparent thermal stability of Celion/LARC-160 composites. Three 
different geometric configurations of Several thicknesses of unidirectional, 
x-ply and fabric reinforced panels of LARC-l60/Celion were thermally aged at 
temperatures of 204"C, 260°C and 316°C for times up to 15,000 hours. 
Results are presented showing the weight-loss of each panel as function 
aging time and temperature. 
3 
E X PER I ME N TAL PR OC E I) IJ R E 
M a t e r i a l s  and F a b r i c a t i o n  
The p o l y i m i d e  m a t r i x  r e s i n  used i n  a l l  t h e  laminates i n  t h i s  s tudy was 
LtRC-160. LAHC-160 i s  a s o l v e n t l e s s  r e s i n  system based on t h e  e t h y l  e s t e r s  
o f  3,3 '  ,4,4'-henzophenone t e t r a c a r b o x y l  i c  d ianhydr ide  (BTOA) and 5-norbor-  
nene-2,3-d icarboxy l ic  a c i d  ( N A ) ,  and Jef ferson Jef famine A P - 2 2  aromat ic  
amine m i x t u r e  ( r e f .  7 ) .  T$e carbon f i b e r  used f o r  t h e  u n i d i r e c t i o n a l  and 
x-pq i e d  laminates,  (0.9@),, was C e l i o n  6000 cont inuous fi lament yarn, 
. s i z e d  w i t h  a DuPont NR-15082 p o l y i m i d e  p recu rso r  s o l u t i o n .  The f a b r i c  
re in fo rcemen t  m a t e r i a l  was C e l i o n  3000 cont inuous f i l a m e n t  yarn, s i z e d  w i t h  
an epoxy compat ib le  r e s i n ,  woven i n t o  a 8 harness s a t i n  weave. 
these prepregs, appr.3ximately 30 cm x 30 cm, were vacuum bag au toc lave  
processed t o  e maxirnilm temperature of 330°C accord ing  t o  t h e  cure tempera- 
t u r e  p r o f i l e  shown ilr f i g u r e  1. A f t e r  f a b r i c a t i o n ,  t h e  laminates were 
Layups o f  
s u b j e c t e d  t o  u l t r a s o n i c  C-scan inspec t i on .  F i b e r  volume, r e s i n  content,  
v o i d  c o n t e n t  and th ic i tneqs were determined f o r  each acceptable laminate.  
These a re  shown i n  Table I .  The panels  had low t o  moderate v o i d  con ten t  and 
g e n e r a l l y  a f i b e r  vo1,ume o f  50 t o  60 percent .  The g l a s s  t r a n s i t i o n  tempera- 
t u r e  ( T g )  was measured as 349"C, i n d i c a t i n g  adequate cure.  Each o f  t h e  
accep tab le  30 cm square laminates were c u t  i n t o  t h e  t e s t  panel  con f igu ra -  
t i o n s  shown i n  f i g u r e  2. 
I so the rma l  Aging 
Forced-convect ion h o r i z o n t a l  a i r f l o w  ovens were used f o r  i so the rma l  
aging a t  204OC, 260°C and 316°C. The average a i r  v e l o c i t y  was approx ima te l y  
4 
Q.75  m/sec. 
a o a r t ,  w i t h  a i r  f l o w i n g  f r e e l y  between each panel .  The panels were 
su9 jec ted  t o  exposure t imes up t o  15,000 hours.  
a l l  panels  were removed f o r  weight  l o s s  de te rm ina t ions  and then rep laced.  
Each t ime, the  oven was cooled t o  room temperature over a p e r i o d  o f  two 
hours t o  lessen t h e  thermal shock when t h e  Danels were removed. When t h e  
aging of the panels was completed, t h e y  were each examined c l o s e l y  w i t h  a 
l o w  power microscope and photographed. 
The panels  were suoported v e r t i c a l l y  on t h e i r  edges, 12 mm 
A t  predetermined i n t e r v a l s ,  
S ince t h e  r e s i n  conter l t  of t h e  panels var ied,  t h e  w e i g h t - l o s s  da ta  were 
normal ized t o  a u n i f o r m  30 percent  r e s i n  content .  
9ESULTS AND DISCUSSION 
One o b j e c t i v e  of t h i s  s tudy was t o  examine t h e  e f f e c t  o f  t h e  exposed 
pane! edge on t h e  measured weight  loss.  The r e s u l t s  r e p o r t e d  i n  r e f e r e n c e  
2, i n d i c a t e d  t h a t  weight  l oss  occurred p r e f e r e n t i a l l y  f rom t h e  su r face  o f  
t h e  panel  edge pe rpend icu la r  t o  t h e  d i r e c t i o n  of t h e  f i h e r  (0" edge) i n  
u n i d i r e c t i o n a l  laminates.  The t h r e e  panel  c o n f i g u r a t i o n s  aged i n  t h i s  s tudy  
( f i g .  2 )  p rov ided  a v a r i a t i o n  o f  t h i s  parameter. C o n f i g u r a t i o n  I has t h e  
l a r g e s t  do edge su r face  area r e l a t i v e  t o  bo th  t o t a l  edge su r face  o r  panel  
volume, and I 1  t h e  sma l les t .  The e f f e c t  o f  these t h r e e  panel  c o n f i g u r a t i o n s  
on long-term thermal ag ing behavior  o f  u n i d i r e c t i o n a l  panels  aged a t  204°C 
i s  shown i n  f i g u r e s  3 t o  5. The we igh t - l oss  behavior  of t h e  4 - p l y  panels  i n  
f i g u r e  3 shows a v a r i a t i o n  w i t h  panel  c o n f i g u r a t i o n  b u t  n o t  t h a t  which was 
expected. The c o n f i g u r a t i o n  I1 panel ( l e a s t  0" edge area) degraded t h e  most 
and t h e  panel  I (most 0" edge area) t h e  l e a s t .  Th is  appears t o  i n d i c a t e  
5 
4 
that the 90" edge of these panels i s  the preferential site for weight-loss. 
ijowever in figure 4, the weight-loss curves for the 8-ply panels, there is 
little difference between the three configurations. This is also true for 
the 16-ply panels shown in figure 5. In figures 6 and 7 the 4-ply 
unidirectional weight-loss curves f o r  agina at 260°C and 316°C are shown. 
Neither o f  these show any significant effect of panel'configuration. 
fact, none of the unidirectional panels aged at 260°C and 316°C showed any 
effect of panel configuration. It can be seen in figures 8 and 9 that the 
x-ply and fabric reinforced aged at 204"C, as expected, also show no effect 
of panel configuration. 
I n  
The aging data at 260°C and 316°C were similar. 
The effect of panel tnickness on weight-loss behavior is illustrated i n  
figures 10 to 12. T'le weight-loss curves of the unidirectional square 
panels aged at 204°C exhibit a systematic variation, with the 16-ply having 
the ledst weight-loss and the 4-ply having the most. This same behavior was 
shown by the x-ply panels ? u t  the fabric reinforced panels show little 
effect of panel  thickpess. These same general trends were repeated when the 
panels wcA't'e aqetl at 260°C and 316°C ( f i g s .  13 to 18). The thinner ( 4  and 8 
ply) unidirectional panels, however, show an increasing tenderlcy to degrade 
at the same rate. When aged at 316'C these two are essentially the same, 
whereas the 16-ply panel remains distinctly more stable. 
The variation in weight-loss with ply configuration (unid rectional, 
x-ply an3 fabric) is typified by the '8-ply aging curves shown 
to 21. 
unidirectional panels are significantly more stable than the x-ply or fabric 
panels. There is little or no difference between fabric reinforced and 
x-plied panels. 
n figures 19 
When aged at 204°C the The other thicknesses show the same trends. 
As the aging temperature is increased to 260°C and 316'C 
6 
the difference between the three ply configurations disappears. 
all three deqrade essentially at the same rate. 
At 3 1 6 O C  
CONCLUSIONS 
A general conclusion of this study is that for moderate sized panels 
tne geometric shape does not significantly influence weight-loss during 
thermal aging. The panel thickness did significantly effect the weight-loss 
of unidirectional and x-ply specimens aged at 204°C and 26OOC. The thicker 
panels degraded the least, the thinnest degraded the most.  This effect was 
q r e a t e s t  at 704"C, less at 260°C and essentially absent at 316OC. 
no significant effect of panel thickness observed in the fabric reinforced 
pdnels aged at any temperature. The p l y  configuration (unidirectional, 
x-aly o r  fabric) was an iiioortant factor in panels aged at 2 0 4 O C .  
unidirectional panels were significantly more stable than the fabric and 
x-ply panels. On aging at 260°C and 316°C there was no real difference in 
t9e three forms. 
There was 
The 
A t  low aging temperdtures, variables such as panel thickness and ply 
arrangement 2ffect the observed stability. At higher aging temperatures all 
panel configurations converae toward the same behavior. 
L 
7 
REFERENCES 
1. Serafini, T.  T.; Delvigs, P.; and Lightsey, G. R.: 
Polyimides from Solutions of Monomeric Reactants. 
Thermally Stable 
J. Appl. Polym. Sci., 
V O ~ .  16, NO. 4 ,  1972, pp. 905-915. 
2 .  Nelson, J. 5.: Long-Term Thermal Aging o f  Two Graphite/Polyimide 
Compos i te Mater i a 1 s . NASA TP-2369 , 1984. 
3 .  Nelson, J. 8.: Edge Crack Growth in Thermally Aged GraphitelPolyimide 
Composites. NASA TM-85163, 1984. 
4 .  Kray, R. J.: Development o f  New Addition-Type Composite Resins. NASA 
CR-3276, 1981. 
5 .  Yaximovicb, M. G.; Rer,y-en, 0.; and Lockerby, S . :  Development o f  
LARC-l60/NR150B2 Polyivide Graphite Hybrid Composites. 
198c:. 
NASA CR-159196, 
6. Nelson, J .  R.: Long-Term Thermal Aging o f  CelionD378A Composite 
Mat?rials. NASA TM-86362, 1985. 
7 .  St. C l a i r ,  T. L.; and Jewell, R .  A.:  Solventless LARC-160 Polyimide 
Matrix Resin. Proceedings, 23rd National SAMPE Symp., vol. 23, May 
1978, pp. 520-521.  
8 
TABLE I--INITIAL PROPERTIES OF CELION/LARC-160 
~ LAMINATES 
8 
I TH'CKNESS in. PANEL TYPE 
4-Ply Uni 
8-Ply Uni 
16-Ply Uni 
.023 
.047 
.092 
4-Ply x-Ply 
6-Ply X-Ply 
8-Ply X-Ply 
16-Ply X-Ply 
.022 
.033 
.043 
.080 
 
4-Ply Fabric .060 
8-Ply Fabric I .126 
FIBER VOL. 
0% 
53.2 
67.2 
54.0 
53.8 
48.5 
50.5 
52.1 
48.6 
54.6 
C 
RESIN WT. VOIDS 
% 1 %  
36.8 
25.2 
38.3 
4.4 
2.2 
0.5 
36.9 
42.8 
40.4 
40.1 
3.1 
1.9 
3.2 
0.4 
42.7 I 1.9 
0.9 37.3 
f 
2 
c 
(11 $9 
c" 
4oo 1 330°C 
3 hr 
PRESSURE AT 
274°C 
1 hr 
300 - 
0 I 
I I d 
2 4 6 8 0 
Curing Time, 
hrs 
3"C/min 
   
Figure 1. Temperature profile for Celion/LARC-160 autoclave curing process. 
10 
I '  fl-1 1 0" FIBER DIRECTION 
1 
k 6" -+i 
I1 
I11 
0" FIBER DIRECTION I 
6" 
1 
0" FIBER 
DIRECTION 
Figure 2. Test panel configurations. 
t 
5 
4 -  
3- 
2 -  
AGING TIME, hrs 
0 GROUP1 
0 GROUPll 
GROUPIII 
11 
1 -  
0 
v u  
0 I I 8 
Figure 3. Weight loss of 4-ply unidirectional panels of Celion/LARC-l60 aged 
at 204°C. 
v) 
v) 
2 
s 
c z 
W 
0 
K 
W n 
AGING TIME, hrs 
Figure 4. Weight loss of 8-ply unidirectional panels of Celion/LARC-l60 aged 
at 204°C. 
12 
AGING TIME, hrs 
Figure 5. Weight loss of 16-ply unidirectional panels of Celion/LARC-160 aged 
at 204°C. 
Figure 6. Weight 
4 
AGING TIME, hrs 
loss of 4-ply unidirectional panels of Celion/LARC-l60 aged 
at 260°C. 
AGING TIME, hrs 
Figure 7. Weight loss of 4-ply unidirectional panels of Celion/LARC-l60 aged 
at 316°C. 
cn cn s 
s 
10 
8 
6 
2 .j 
AGING TIME, hrs 
Figure 8. Weight loss of 4-ply X-plied panels of Celion/LARC-160 aged at 
204°C. 
14 
AGING TIME, hrs 
Figure 9. Weight loss of 4-ply fabric reinforced panels of Celion/LARC-l60 
aged at 204°C. 
L 
Figure 10. Weight loss variation with panel thickness of unidirectional Celion/ 
LARC-160 square panels aged at 204°C. 
10 
8- 
6 -  
4 -  
2 -  
0 4PLY 
0 8PLY 
16PLY 
0-, 
v) 
8 
I- z 
W 
0 
U w n 
15 
AGING TIME, hrs 
Figure 11. Weight loss variation with panel thickness of X-plied square panels 
of Celion/LARC-160 aged at 204°C. 
AGING TIME, hrs 
Figure 12. Weight loss variation with panel thickness of fabric reinforced square 
panels of Celion/LARC-160 aged at 204°C. 
20 , 
0 I . 
0 4PLY 
0 8PLY 
16PLY 
15 
10 I / /  
16 
5 
AGING TIME, hrs 
Figure 13. Weight loss variation with panel thickness of unidirectional square 
panels of Celion/LARC-l60 aged at 260°C. 
4PLY 
0 8PLY 
16PLY 
10 
I 
Figure 14. Weight loss variation with panel thickness of X-plied square panels 
of Celion/LARC-160 aged at 260OC. 
0 4PLY 
30: 20 0 8PLY 
10 
0 
102 
17 
AGING TIME, hrs 
Figure 15. Weight loss variation with panel thickness of fabric reinforced square 
panels of Celion/LARC-160 aged at 260°C. 
. l o z  103 AGING TIME, hrs 
Figure 16. Weight loss variation with panel thickness of unidirectional square 
panels of Celion/LARC-l60 aged at 316°C. 
60 
50 
40 
30 
20 
10 
0 
10' 10 
AGING TIME, hrs 
l o 4  
18 
Figure 17. Weight loss variation with panel thickness of X-plied square panels 
of Celion/LARC-160 aged at 316°C. 
AGING TIME, hrs 
Figure 18. Weight loss variation with panel thickness of fabric reinforced square 
panels of Celion/LARC-160 aged at 316°C. 
19 
Figure 19. 
l o L  i o 4  
AGING TIME, hrs 
UNIDIRECTIONAL 8i 0 x-PLY 
Weight loss of 8-ply square panels of Celion/LARC-l60 aged 
204OC. 
cn cn s 
s 
I- 
2 
W 
0 
W 
a 
n 
UNIDIRECTIONAL Ill 
0 x-PLY 1 
I I 
10 * 103 104 105 
AGING TIME, hrs 
at 
Figure 20. Weight loss of 8-ply square panels of Celion/LARC-l60 aged at 
260°C. 
50 
40 UNIDIRECTIONAL 
30 
20 
10 
0 
AGING TIME, hrs 
Figure 21. Weight loss of 8-ply square panels of Celion/LARC-l60 aged at 
31 6°C. 
Standard Bibliographic Page 
_- ____ - -_ - .-______ ---_____ - 
7 A u t t i o r ( s )  
James B. Ne lson  
_ _  
December 1987 
. - I 6. Performing Organization Code E f f e c t  o f  Geoiiietry on Thermal Aging Behavior  o f  Celion/LARC-160 Composites 
- 
8. Performing Organization Report No. 
N a t i o n a l  Ae ronau t i cs  and Space A d m i n i s t r a t i o n  
Washington, DC 20546 
14. Sponsoring Agency Code 
I ___ _ ~ _  __-_____ 
1 5  SuppleIneiitary Notes Use o f  commercial products o r  names o f  manufacturers i n  t h i s  
r e p o r t  does not c o n s t i t u t e  o f f i c i a l  endorsement o f  such p roduc ts  o r  manufacturers  
e i t h e r  expressed o r  i m p l i e d ,  by  t h e  N a t i o n a l  Ae ronau t i cs  and Space A d m i n i s t r a t i o n  
Kr\ Word< (Suggested bj Auth~rs(s))  
__-- 
, If, Abstract 
i Laminates of Celion@/LARC-160, f a b r i c a t e d  i n  th i cknesses  f r o m  4 t o  16 p l y  and i n  
u n i d i r e c t i o n a l ,  x - p l y  and f a b r i c  p l y  c o n f i g u r a t i o n s ,  were i s o t h e r m a l l y  aged a t  
1 temperatures of 204, 260 and 316°C f o r  pe r iods  up t o  15,000 hours. 
t h e  t e s t  pane ls  was measured a t  se lected i n t e r v a l s  d u r i n g  aging. A t  t h e  lower 
ag ing  temperatures,  it was observed t h a t  panel  t h i c k n e s s  and p l y  arrangement 
~ i n f l u e n c e d  t h e  apparent s t a b i l i t y :  
, panels  and u n i d i r e c t i o n a l  panels degraded less  than x - p l y  o r  f a b r i c  r e i n f o r c e d  
, panels .  
Weight- loss o f  
i.e., t h i c k e r  panels  degraded less  than t h i n  
A t  h i g h e r  ag ing temperatures, a l l  panel  c o n f i g u r a t i o n s  and th i cknesses  
converged toward t h e  same behavior .  
18 Distribution Statement 
20. Security Classif.(of this page) 19 Securit? Cidsrif (of this report) 
~ U n c l a s s i f i e d  
Thermal Ag i ng I Composite 
21. No. of Pages 22. Price 
1 S u b j e c t  Ca tegor ies  24 and 27 
For sale by the National Technical Information Service, Springfield. Virginia 22161 
N A S A  Langlc? f o r m  L J  ( J u n e  198s)  


Effect of geometry on thermal aging behavior of Celion/LARC-160 composites

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