An incremental-onset model for fatigue delamination propagation in composite laminates

Abstract

We propose to treat propagation of a fatigue-driven delamination in composite laminates as a sequence of incremental delamination onsets and develop a cohesive zone model (CZM) to simulate it. The model employs a fatigue damage evolution law that is based on the reduction of critical strain energy release rate. Unlike existing fatigue CZMs, which assume and use Paris' law derived from propagation tests as input, the proposed model relies solely on the experimental data from fatigue onset tests (namely the G-N curve, where G is the supplied strain energy release rate and N is the number of cycles to onset). The model is implemented within an implicit finite element code using three-dimensional cohesive elements and is demonstrated to predict fatigue delamination propagation in unidirectional carbon fibre/epoxy composites under Mode I loading. This incremental onset model predicts the Paris’ law, which compares well with experimental data for this case. Composites with toughened inter-laminar interface and under other modes of deformation and their combinations may exhibit a different fatigue behaviour.