Observation on Failure Process of Fiber-Reinforced-Composites in High Temperature Fatigue

采用CF/PEEK和CF/PMR-15复合材料的双悬臂梁试样，研究了碳纤维增强聚合物在高温下的分层行为，以阐明基体蠕变的影响。通过光学显微镜观察分层裂纹的扩展，发现蠕变加速了CF/PEEK在473K时的扩展速率，而CF/PMR-15在573K时几乎没有发生蠕变。根据线性断裂力学的概念，成功地对实验结果进行了分析。为了考察光纤桥接的屏蔽效果，在恒应力强度因子范围内进行了试验。由于光纤桥接的作用，裂纹的扩展速率减慢。用显微镜观察桥接的微观形态。对sic晶须增强铝合金在573K高温下进行了疲劳试验。本研究的重点是观察高温疲劳下的失效寿命和裂纹形貌。蠕变导致疲劳寿命缩短。在疲劳过程中观察到的裂纹很少，其中一个裂纹是在寿命中期产生的，导致了失效。由于该材料在高温下的抗拉强度和蠕变寿命是由联合研究项目（《sic晶须增强铝合金高温强度报告》，日本材料科学学会，1993年）进行的，因此本研究的结果是在基础数据的基础上进行分析的。

Delamination behavior of carbon fiber reinforced polymer at high temperatures was investigated in order to elucidate the effect of matrix creep using double cantilever beam specimens of CF/PEEK and CF/PMR-15 laminates. The propagation of delamination crack was observed by means of optical microscope and it revealed that the creep accelerated the propagation rate of CF/PEEK in fatigue at 473K while the creep scarcely took place in the tests of CF/PMR-15 at 573K.The experimental results was successfully analyzed on the basis of linear fracture mechanics concept. The tests were also conducted under constant stress intensity factor range in order to examine the shielding effect of fiber bridging. The propagation rate was decelerated as the crack propagated because of the fiber bridging. The micro-morphology of bridging was observed by means of microscopes.The fatigue tests of SiC-whisker reinforced aluminum alloy were carried out at 573K.The focus of this study was put on the observation on the failure life and the cracking morphology in high temperature fatigue. The fatigue life was shortened by creep deformation. Few cracks were observed during the fatigue and one of them, which initiated at the middle stage of life, brought about the failure. As the tensile strength and the creep life of the material at high temperatures was examined by a joint research project (Report on High Temperature Strength of SiC-whisker reinforced aluminum alloy, Society of Materials Science, Japan, 1993), the results obtained in this study were analyzed on the basis of the fundamental data.