Polyimide composites (PETI-340M) were fabricated and subjected to high-temperature aging and thermal cycling to evaluate resistance to degradation. Mechanical-degradation mechanisms and kinetics depended on aging temperature. Aging at 232°C resulted in strength loss due to polymer degradation, while intra-tow cracking was the dominant mechanism during aging at 288°C. Composite panels subjected to thermal-cycling fatigue (−54°C to 232°C) retained mechanical properties without microcracking. However, in regions containing pre-existing fabrication-induced defects (primarily voids), intra-tow microcracks were observed after thermal cycling. Unlike some polyimide composites (PMR-15), oxidative aging effects during thermal cycling were negligible. The thermo-oxidative stability and the retention of mechanical performance after thermal cycling indicates potential for long-term, high-temperature structural applications.

制造聚酰亚胺复合材料 (PETI-340M) 并对其进行高温老化和热循环以评估抗降解性。机械降解机制和动力学取决于老化温度。在 232°C 下老化导致聚合物降解导致强度损失，而在 288°C 下老化过程中丝束内开裂是主要机制。经受热循环疲劳（-54°C 至 232°C）的复合板保留了机械性能而没有微裂纹。然而，在包含预先存在的制造缺陷（主要是空隙）的区域中，在热循环后观察到丝束内微裂纹。与某些聚酰亚胺复合材料 (PMR-15) 不同，热循环过程中的氧化老化效应可以忽略不计。