Chuang, Kathy C.

Criss, Jim M.

Mintz, Eric A.

NASA Technical Reports Server

Kathy C. Chuang
NASA Glenn Research Center, Cleveland, OH 44135
(216) 433-3227; Kathy.Chuang@grc.nasa.gov
Jim M. Criss
M & P Technologies, Inc. Marietta, GA 30314
(770) 652-7638; jim.m.criss@mandptechnologies.com
Eric A. Mintz
Center for High Performance Polymers and Composites,                      
Clark Atlanta University, Atlanta, GA 30314
Polyimide Composites Properties of 
RTM370 Fabricated by VARTM
https://ntrs.nasa.gov/search.jsp?R=20150010187 2019-08-31T07:44:09+00:00Z
High Temperature Polyimide Composites
Materials & Processing
♦ Conventional PMR-15, PMR-II-50, AFR-PE4 polyimide composites all 
require solvent-based prepregs for part fabrication ⇒ time consuming, 
costly and the use of solvents and diamines are hazardous
♦ Fabricate net-shape polymer matrix composites from resins in the melt 
via RTM or VARTM using preforms ⇒ eliminate costly hand lay-up and hazard
⇒ produce 30% cost saving & 20% weight saving for complex parts 
⇒ adaptable to automatic process
Challenge: RTM or VARTM requires low-melt viscosity that conventional
polyimides derived from commercially available s-dianhydride 
(> 103-105 poise) cannot meet 
♦ a-BPDA based imide resins have shown to exhibit low-melt viscosity 
(10-30 poise) at 280 °C ⇒ amenable to low-cost RTM  or VARTM process
♦ Advance PMC temperature capability to 260-315°C  beyond the 
state-of the-art RTM resins, such as epoxy (177 °C) &  BMI (232 °C)
Objectives
♦ Fabricated composite panels with 
RTM370 imide resin (~10-30 poise) 
by vacuum  assisted resin transfer
molding (VARTM)
♦ Compare mechanical properties of 
VARTM panels to RTM panels at 
288-315°C (550-600°F)
VARTM vs RTM
VARTM RTM
Use vacuum bag Need a mold (expensive)
Use vacuum only Use pressure and/or vacuum
15-20 psi 200 psi
Suitable for large part Suitable for small part/mold
RTM370 Imide Resins 
Advantages of imide resins containing a-dianhydrides:
•   Lower melt viscosities
•   Higher Tg’s
Solvent-Free process:
● No organic volatiles (Green)
● Adaptable to reactive extrusion (cost saving)
O
O O
O
O
O
+ O
H2N
NH2 + O
O
O
C C
Melted
a-BPDA            PEPA
 Imidized Oligomers
   
Physical Properties of Imide Oligomers/ Resins 
Based on a-BPDA and 4-PEPA
Resin Diamine Oligomer
Min. η @280 °C
by Brookfield1
(Poise)
Oligomer
Min. Complex 
[η]* @280°C2
(Poise)
Cured Resin
Tg (°C)
NPC3
byTMA5
Cured Resin
Tg (°C)
PC4@ 650°F
RTM370 3,4’-ODA 8.8 6.5 342 3705
RTM370 Composite --- --- 338
(DMA)6
350 
(DMA)6
1 Absolute viscosity measured by Brookfield Viscometer at 280 °C.
2 Complex viscosity measured by Aries Rheometer, using parallel plates.
3 NPC = No Post cure
4 PC = Resin Postcured at 343 °C (650 °F) for 16 hrs while composite postcured@650°
5 TMA =Thermal mechanical analysis heated at 10 °C/min, using expansion mode.
6 DMA = Dynamic mechanical analysis were performed at 5 °C/min heating rate,
using single cantilever.
3,4’-ODA = 3,4’-Oxydianiline
Rheology of APS’s RTM370 Imide Resin
2 hr hold at 280 °C
RTM370 Composite Property Comparison
VARTM vs RTM (T650-35/HT sizing) 
Test 
Temp.
OHC Strength
(MPa)
Initial   500h      1000h
@550°F  @550°F
288°C       288°C
OHC Modulus
(GPa)
Initial  500h    1000h
@550°F @550°F
288°C    288°C
SBS Strength
(MPa)
Initial 500h      1000h
@550°F  @550°F
288°C     288°C
VARTM
RT
288°C
315°C
327°C
233    194    120
186    197    135
182     --- 118
184     --- ---
37       38     33
40       42     38
42       --- 38
41       --- ---
43      37      22
31      27      17
29      26      15
30      --- 16
RTM
RT
288°C
315°C
327°C
269    287    230
242    244    198
231     --- ---
241     --- ---
44        47    44
48        44    45
46        --- ---
48        --- ---
51      54      43
41      41      41
31      --- ---
30      --- ---
RTM370  OHC Strength VARTM vs RTM
(T650-35/8HS/HT Sizing)
RT 288°C 315°C 327°C
0
50
100
150
200
250
300
O
p
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n
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H
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C
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p
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S
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t
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(
M
P
a
)  RTM370 by RTM
 RTM370 by VARTM
 BMI-5270-1 by RTM
550°F        600°F        620°F
RTM370  OHC Modulus VARTM vs RTM
(T650-35/8HS/HT Sizing)
RT 288°C 315°C 327°C
0
10
20
30
40
50
60
O
p
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M
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s
 
(
G
P
a
)
 RTM370 by RTM
 RTM370 by VARTM
 BMI-5270-1 by RTM
550°F         600°F         620°F
RTM370 SBS Strength VARTM vs RTM
(T650-35/8HS/HT Sizing)
RT 288°C 315°C 327°C
0
10
20
30
40
50
60
S
h
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B
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S
h
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S
t
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t
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(
M
P
a
)  RTM370 by RTM
 RTM370 by VARTM
 BMI-5270-1 by RTM
550°F            600°F           620°F
VARTM vs RTM
SEM of RTM370 made by VARTM
Void content = ~6.5% after postcured at 650°F/8 h
Resin vs fiber content =47-50% vs 53-50%
RTM370 Made by RTM
Void content= ~1%
Resin content = 44-47%
VARTM RTM
15-20 psi 200 psi
Higher void content Lower void content
Process Improvement:
♦ Injection at 260°C instead of 280°C ⇒ Longer pot-life, but longer injection time
♦ Add hold time at ~300°C, instead of direct ramp from 280°C to 371°C
Open-Hole Compression Strength of RTM370 Composites
Subjected to Isothermal Aging at 288°C for 1000 h in Air
550°F          600°F          620°F      
RT 288°C 315°C 327°C 
0
50
100
150
200
250
300
350
400
O
p
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n
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H
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C
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p
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s
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S
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(
M
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)
 Initial Property by RTM
 Initial property by VARTM
 500 h@288°C by RTM
 500 h@288°C by VARTM
 1000 h@288°C by RTM
 1000 h@288°C by VARTM
Open-Hole Compression Modulus of RTM370 Composites
Subjected to Isothermal Aging at 288°C for 1000 h in Air
550°F          600°F          620°F
RT 288°C 315°C 327°C 
0
10
20
30
40
50
60
70
80
O
p
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C
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p
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s
s
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M
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(
G
P
a
)  Initial Property by RTM
 Initial Property by VARTM
 500 h@288°C by RTM
 500 h@288°C by VARTM
 1000 h@288°C by RTM 
 1000 h@288°C by VARTM
Short-Beam Shear Strength of RTM370 Composites
Subjected to Isothermal Aging at 288°C for 1000 h in Air
550°F          600°F          620°F         
RT 288°C 315°C 327°C 
0
10
20
30
40
50
60
70
80
S
h
o
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t
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B
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S
h
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S
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(
M
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)
 Initial Property by RTM
 Initial Property by VARTM
 500 h@288°C by RTM
 500 h@288°C by VARTM
 1000 h@288°C by RTM
 1000 h@288°C by VARTM
Summary 
♦ Demonstrated RTM370 imide resin can be 
processed by VARTM out of autoclave
♦ VARTM panels have higher void content than 
those made by RTM, due to lack of pressure 
VARTM panels appeared to have slightly 
lower OHC, but comparable SBS at high temp. &
retained good mechanical properties after aging 
♦ Need process development to reduce void 
content to < 2% for aerospace applications
♦ Need to improve the resin content of VARTM
panels from 47-50% to 35-40%.
Acknowlegements
♦ NASA Glenn Tech Transfer Fund
♦ Akron Polymer Systems for supplying
RTM370 resin 
♦ Ohio Third Frontier Funding (Maverick)
♦ NASA Co-Op Grant to Clark Atlanta U.
♦ Linda McCorkle (OAI)  : SEM, Rheology 
Acid Digestion 
♦ Brian Shonkwiler(CAU): Mechanical Testing
♦ Dan Scheiman (ASRC): Thermal Analysis


Polyimide Composites Properties of RTM370 Fabricated by VARTM

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