Interfacial fatigue damage of fiber-reinforced composites by coating the fibers with functionally graded materials

In this paper, the interfacial damage properties of fiber-reinforced composites (FRCs) by coating the fibers with functionally graded materials (FGMs) under a tension–tension cyclic load is investigated. Based on the double shear-lag model and the modified power degradation model, the stresses in both the bonded region and the debonded region are obtained; then the relationships between the parameters (such as the debond rate and the debond length) and the number of cycles are studied using the fundamentals of fracture mechanics. For the purposes of practical application, the effects of the coating gradient as well as the dimensions of the fiber and coating are discussed, and the composite strain is also provided. To validate the analytical results, a numerical analysis is performed by the secondary development of a finite element code.