Long-Term Mechanical and Thermal Performance and Lifetime Estimation of a Carbon Fiber Reinforced Polycarbonate Laminate

The degradative property performance and the deterioration of long-term durability and reliability are critical issues for carbon fiber thermoplastic composites exposed to various harsh and changing environments, in particular wet/hot conditions. This study presents an experimental investigation on the long-term mechanical and thermal performance of laminated woven carbon-fiber-reinforced polycarbonate composites (CF/PC). The CF/PC laminate specimens were exposed to a water bath at both ambient and high temperatures (i.e., 25 °C, 60 °C, and 80 °C) for long-term immersion periods. The moisture absorption behavior was investigated via gravimetric methods and the outcomes evidence that the water absorption behavior is a multi-stage process at elevated temperatures. The degradation of the mechanical performance was assessed by monitoring the evolution of flexural modulus and flexural strength during the hydrothermal aging exposure process. Clearly, a prominent effect of the temperature is discerned, where after a duration of 120-day conditioning, approximately 65% and 35% of the flexural strength is retained at 60 °C and 80 °C, respectively, whereas a slight decrease of the flexural modulus is observable. This variation is probably ascribed to the progressive deterioration induced by the degradation of the PC matrix and interface failure. Moreover, the long-term performance of CF/PC laminates is estimated based on the Arrhenius related methodology and the time–temperature superposition principle and the composites remain above the flexural strength retention of 60% for more than 1.4 years. Finally, experimental findings reveal that a slight reduction in the T_g and thermal resistance is observed with increasing exposure temperatures and prolonged durations.