Long-term Durability Study on Mechanical and Dynamic Mechanical Performance of a High-performance Carbon Fiber-polymer Laminate

This paper reports a detailed study on the long-term mechanical and dynamic mechanical performance of carbon fiber (CF) plain-woven fabric-reinforced epoxy (CF/epoxy) laminates fabricated by the hot-compression molding technique. Water-sorption experiments, mechanical property tests, and dynamic mechanical analysis (DMA) tests were performed after immersion in de-ionized water at different temperatures (i.e., 25 degrees C, 60 degrees C, and 80 degrees C) for times up to 120 days. The results show that weight-gain curves for the composites at elevated temperature (i.e., 80 degrees C) fit the theoretical Fickian diffusion curve during the initial immersion time, but deviate substantially as time prolongs. The flexural properties and dynamic mechanical properties are highly susceptible to the effects of the hygrothermal environment, and the performance for both degrade with increasing exposure temperatures and durations. The dynamic mechanical properties partly recover after the drying treatment, which is caused by the irreversible degradation in the interfacial region (i.e., fiber/matrix debonding) as evidenced by morphological images from scanning electron microscopy (SEM). Finally, the long-term degradation of the composites was estimated and the service life of the materials was also predicted using the Arrhenius degradation theory. The outputs of the research show that CF/epoxy laminates have flexural strength retention of 60 % for more than 2 years at the annual temperature of Kyoto.