Effects of interfacial strength and failure modes on the tension-tension fatigue performance of high-toughness CF/EP composites

Carbon fiber (CF) reinforced epoxy (EP) composites have excellent tension-tension fatigue performance and are suitable for blade and rotor structures. Interfacial debonding is one of the typical damage modes in the tension-tension fatigue of CF/EP composites. In this article, the relationship between interfacial shear strength (IFSS) and interfacial failure period as well as tension-tension fatigue performance of CF/EP composites was thoroughly characterized and discussed. By changing the composition of EP, IFSS of CF/EP composites was adjusted. There was no direct correlation between changes in IFSS and changes in one million cycle fatigue strength of CF/EP composites. In order to further study the mechanism of fatigue damage of composites in depth, acoustic emission and scanning electron microscope were used to elucidate the period of interface failure and the mechanism of interface action in the fatigue process. The results indicate that changes in IFSS affect the crack propagation mechanism, thereby affecting the fatigue performance of the composite material. This research provides empirical evidence on the interface damage mechanism during the tension-tension fatigue process of CF/EP composite materials, which could be a guide for the component design of high-toughness composite systems for aerospace applications.