Comparison of Graphite Fabric Reinforced PMR-15 and Avimid N Composites After Long-Term Isothermal Aging at Various Temperatures

摘要

Extensive effort is currently being expended to demonstrate the feasibility of using high performance, polymer matrix composites as engine structural materials over the expected operating lifetime of the aircraft, which can extend from 18,000 to 30,000 hr. To accomplish this goal, it is necessary to pursue the development of thermal and mechanical durability models for graphite fiber reinforced, polymer matrix composites. Numerous investigations have been reported regarding the thermo-oxidative stability (TOS) of the polyimide PMR-15. It is yet to be determined if the information obtained from the PMR-15 composite tests is applicable to other polymer matrix composites. The condensation curing polymer Avimid N is another advanced composite material often considered for structural applications at high temperatures. Avimid N is reported to have better thermo-oxidative stability (TOS) than PMR-15, but the latter is more easily processed. The purposes of the work described herein one to compare the thermal aging behavior of these two matrix polymers and to determine the reasons for, and the consequences of differences in thermal durability. Differences were observed in weight loss time data, microstructural changes, and compression properties after aging at temperatures of 204, 260, 288, 316, and 343℃. Of special interest were the differences in surface thermal and oxidative damage, and also the extent of internal cracking.