Interface damage and failure mechanisms of CF/PEEK composite components in hygrothermal environments: Experimental and molecular dynamics study

CF/PEEK composite components are often subjected to hygrothermal conditions during service, yet the microscopic mechanisms of their hygrothermal damage and failure is difficult to explain by experimental techniques alone. This study integrates experimental techniques with molecular dynamics (MD) simulations to investigate the interfacial damage and failure mechanisms of CF/PEEK bushings under such conditions. The results reveal that the primary failure mode is interfacial debonding, which leads to matrix cracking. At the atomic level, the migration of water molecules from the matrix to the interface is captured, providing insights into the water-PEEK interaction mechanisms. A systematic analysis of the effects of the failure process shows that increased moisture absorption in PEEK raises the levels of bound and free water, weakens the intermolecular forces and increases the mobility of molecular chains, which is exacerbated by the effect of elevated temperatures. The thermal expansion coefficients of CF and PEEK are calculated by MD simulation and found to be 5-8 times different, promoting interfacial debonding and matrix cracking. Both moisture and temperature exacerbate the degradation of PEEK’s tensile properties at the interface, making the matrix more susceptible to collapse and fracture under external mechanical loads. These findings provide valuable atomic-level insights into the mechanisms governing the reduced interfacial integrity and mechanical performance of CF/PEEK composites in hygrothermal environments.