Fatigue-free cohesive zone model for fatigue delamination prediction in fiber reinforced composite laminates

Abstract

This work proposes a Fatigue-free cohesive zone model (F-free model) for predicting fatigue delamination growth in fiber reinforced composite laminates. Unlike traditional empirical approaches that rely on fatigue test calibration, the F-free model is grounded in mechanics and requires only quasi-static delamination data. The formulation combines Timoshenko beam theory with a fatigue cohesive zone model, where the interfacial toughness evolves with crack length to account for the influence of bridging fibers. A proof-stress-inspired method is used to define the cohesive zone endurance limit, eliminating the need for fatigue-specific testing. The model is validated against two benchmark cases. The predicted fatigue delamination growth rates show excellent agreement with experimental data, and the results indicate that the model predictions successfully encompass the full range of observed growth rates. Additionally, the Paris’ law exponents derived from model predictions closely match those obtained from the experimental data. Beyond accuracy, the approach offers physical insight into the mechanical role of fiber bridging, revealing its effect in raising the fatigue threshold and steepening the crack growth curve. Overall, the model provides a robust framework that does not require fatigue data for simulating fatigue delamination growth in fiber reinforced composite laminates.