Composites fatigue delamination prediction using double load envelopes and twin cohesive models

This paper presents an explicit finite element methodology for predicting fatigue delamination in composite laminates using twin cohesive models and a combined static & fatigue cohesive formulation; one model is loaded under the peak-load envelope, whilst the other model is loaded under the trough-load envelope. The twin models contain pairs of twin cohesive interface elements that predict delamination growth by exchanging data at every time increment. The cohesive formulation evaluates fracture mechanics parameters, e.g. the local minimum to maximum fracture energy ratio via local information associated with the twin cohesive elements, without the need to know the global loading information, e.g. the global R ratio. The method allows predicting the mechanical condition of a laminate at both the peak and trough loads. This method is validated by multiple test cases with varying mode mixities and R ratios, showing a high computation efficiency.