Time and Temperature Dependent Stress-Strain Behavior of Unidirectional Carbon Fiber/Polyimide Composites Under On-axis and Off-axis Tensile Loading

Phenylethynyl terminated polyimide “TriA-X” developed in Japan Aerospace Exploration Agency (JAXA) exhibits excellent mechanical properties with high glass transition temperature (> 350 °C), therefore it is suitable as matrix resin of high temperature composites. However, the time and temperature dependent mechanical properties have not been investigated. This study examined the mechanical behavior of unidirectional (UD) carbon fiber (CF)/ TriA-X polyimide composites by off-axis monotonic tensile tests and off-axis tensile creep tests. As results, it was revealed that one parameter plasticity model by Sun and Chen was effective to represent the nonlinear stress-strain behavior of UD-CF/ TriA-X composites. Furthermore, linear viscoelastic behavior was observed from the off-axis tensile creep tests of UD-CF/ TriA-X composites. On the other hand, residual strain was observed in creep recovery curves after unloading, which suggested that the creep and creep recovery behaviors of UDCF/ TriA-X composites are not affected only by viscoelastic and plastic deformation, but also by viscoplastic deformation.