Hydrothermal aging of friction riveted thermoplastic composite joints for aircraft applications

In this paper, the sensitivity of carbon fiber reinforced polyether-ether-ketone friction riveted joints to hydrothermal aging was assessed, addressing the degradation mechanisms and post-aged quasi-static mechanical behavior of the joints. The joints were exposed to 71 °C and 95% relative humidity for 28 days. Despite the oxidation of the metallic nut and washer as well as cavitation and degradation of the composite, a 23% increase of joint mechanical performance was observed after 28 days of exposure. It is believed that the temperature and water uptake drove matrix post-crystallization at the surface of the fibers, which led to local strengthening of the composite in the rivet surrounding and, consequently, improved the joint residual strength.