A phenyl–ethynyl terminated polyimide resin based on KAPTON-type backbone structures, ‘TriA-X’, polyimide is promising as a matrix resin of heat-resistant carbon fiber reinforced plastic composites, but its mechanical properties remain unclear. This study examined off-axis stress–strain behavior of unidirectional carbon fiber (CF)/TriA-X polyimide composites under tensile load at room temperature (RT), 100°C, 150°C, and 200°C to elucidate the matrix resin plastic deformation behavior. Comparing the rupture stress and rupture strain of off-axis specimens at RT and 100°C, they decreased concomitantly with increasing test temperature. Comparison of the rupture stress at 100°C, 150°C and 200°C revealed no significant difference in the rupture stress. A one-parameter plasticity model proposed by Chen and Sun with temperature-dependence of the plasticity model parameters elucidated the nonlinear stress–strain behavior. Model results agreed well with the nonlinear stress–strain behaviors of the CF/TriA-X composites at RT, 100°C, 150°C, and 200°C.

中文翻译：

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单向碳纤维/苯基-乙炔基封端的 KAPTON 型聚酰亚胺 TriA-X 复合材料在高温下的非线性应力应变行为

基于 KAPTON 型骨架结构的苯基乙炔基封端聚酰亚胺树脂“TriA-X”聚酰亚胺有望作为耐热碳纤维增强塑料复合材料的基体树脂，但其机械性能仍不清楚。本研究检测了单向碳纤维 (CF)/TriA-X 聚酰亚胺复合材料在室温 (RT)、100°C、150°C 和 200°C 拉伸载荷下的离轴应力应变行为，以阐明基体树脂塑性变形行为。比较室温和 100°C 下离轴试样的断裂应力和断裂应变，它们随着测试温度的升高而降低。100°C、150°C和200°C下的断裂应力比较显示断裂应力没有显着差异。Chen 和 Sun 提出的单参数塑性模型具有塑性模型参数的温度依赖性，阐明了非线性应力-应变行为。模型结果与 CF/TriA-X 复合材料在室温、100°C、150°C 和 200°C 下的非线性应力-应变行为非常吻合。