Abstract
The hygrothermal behavior of carbon fiber-reinforced ploy(ether ether ketone) (PEEK) and poly-phenylene sulfide) (PPS) composites subjected to moisture and temperature is investigated in this study. The properties of both composites exposed to temperature/humidity and immersed in water for extended periods are studied. Properties studied include moisture sorption, crystallinity, dynamic mechanical response, tensile strength, and flexural strength. Both the PEEK/C.F. and the PPS/C.F. composites exhibit good moisture/ temperature resistance and property retention after hygrothermal exposure. The diffusivities and the equilibrium moisture absorption are measured at 60.70, 80°C with 85% R.H. (relative humidity). A Fickian type diffusion is observed at all exposures. Crystallinity increase of the composites is found for the PPS/C.F. composites exposed to 80°C with 85% R.H. environment and is correlated with the damping properties in the dynamic mechanical study. However, the hygrothermal effect on the crystallinity and the glass transition temperature of the PEEK/C.F. composites is negligible. Mechanical properties of the PEEK/C.F. composites decrease slightly with the increase of temperature/moisture and exposure period. Mechanical property reductions of the PPS/C.F. composites decrease with the increase in exposure temperature when subjected to a similar environment; this is due to the relatively complete molecular relaxation and additional crystallization of higher temperature.