SAMPE Journal - May/June 2017 - 11
Feature Article
temperature structures could require
thermal-cycling tests applicable to
the intended application to properly
assess their durability.
Conclusions
In summary, RTM370 resin is a very
promising polyimide resin and is
relatively easy to process, especially
into thicker, 6-mm laminates as
shown by the processing of 56 cm
× 56 cm panels. Many polyimide
resins are not able to satisfactorily
produce high-quality laminates at
that thickness.
Processing trials
at the beginning of the program
established usable cure/post-cure
cycles and were verified by NDE.
The mechanical properties of UNC
and OHC were within the expected
value range from RT to 288°C (550ºF).
These data indicate that, while the
232°C (450°F) and 288°C (550°F)
values were well within expected
range, a longer-term application,
especially at 288°C (550°F), should
be evaluated based on application
time-at-temperature requirements.
The
compression-after-impact
(CAI) tests also verified RTM370's
toughness as evidenced by the very
satisfactory value. The typical value
at RT of ~270 MPa after a 373-J impact
energy is very satisfactory compared
to competing polyimide composites.
The thermal cycling tests showed
these materials to have aboveaverage resistance to microcracking
at both -54°C to 232°C and -54°C
to 288°C up to 1200 thermal cycles,
although they did not make it to the
2400-cycle target. Overall, RTM370
composites performed better than
many competing polyimide resin
composites.
Further
characterization
of
these materials is recommended
to determine the full spectrum of
properties for targeted performance
requirements tied to specific
potential parts and platforms. Such
characterizations should include a
wider variety of mechanical tests,
including
notched
properties,
and the sensitivity of mechanical
performance with sizing relating
SAMPE Journal, Volume 53, No. 3, May/June 2017
Figure 8. Short beam shear strength of RTM370/T650-35 stitched composites.
Subjected to isothermal aging at 288°C (550°F) in air for 1000 h.
to elevated-temperature exposure,
especially for extended periods
of time. Future studies should
also include processing trials to
evaluate the feasibility of using
RTM370 imide resin to produce
larger, more complex parts, and
manufacturability of representative
structures. Such studies are essential
if the material is to be used in any
aerospace flight hardware.
Figure 9. High quality of RTM370
stitched composite panel after cure and
post-cure.
Table 3. Compression test data for 6-mm (thick) RTM-370/T650-35 stitched composites.
Table 4. Compression-after-impact (CAI) test result.
Acknowledgements
This work was supported by
NASA contracts NNC10AA03A and
NNC12AA01A with Boeing under
50/50 cooperative agreement. Boeing
Research & Technology at Huntington
Beach, CA performed all the fabrication,
quality and testing effort on the program
with California State University, Long
Beach (CSULB). The authors also like to
thank Ohio Third Frontier for funding
support through Maverick Corp., and
Akron Polymer Systems for producing
and providing RTM370 resin for this
study. In addition, funding support
from NASA Supersonic program and
NASA Glenn 2010 Tech Transfer Fund
are greatly appreciated.
11
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