Thermo-mechanical performances of new generation carbon/PEKK aerospace composite structures: The effect of cryogenic conditioning and high service temperatures

The development of the required database for the design of thermoplastic composite materials to be used in aviation applications is only possible by testing these materials in environments that simulate real-life operational conditions. Based on this motivation, in the thesis study, carbon fiber-reinforced thermoplastic composites produced through the AFP (Automated Fiber Placement) process were subjected to cryogenic conditioning (-50 °C), simulating high-altitude flight conditions, and the mechanical performances of the composites were determined at different temperatures (0 °C, room temperature, 50 °C, 100 °C, and 150 °C) after cryogenic conditioning. In this study, the mechanical performances of aircraft structural components were comprehensively addressed for the first time in the literature under increasing temperatures from high altitude to parking position, and to represent microcracks under service conditions, microcracks were induced in the composite specimens using acoustic emission-assisted load/unload tests. The findings indicate that microcracks play a crucial role in the face of escalating temperature cycles and cryogenic conditions.