Assessment of Numerical Approaches for Quasistatic Fatigue and Dynamic Delamination Propagation in Curved Laminates

The accurate prediction of fatigue delamination growth and critical damage size remains an open challenge in enabling the Slow-Growth design and damage-tolerance substantiation in composite aircraft structures. Delamination is especially important due to difficult detectability and the high sensitivity of laminated composites to this failure mode. This work presents a preliminary experimental characterization of the fatigue-driven delamination in a thick, pre-damaged L-shaped composite specimen. To support and interpret these results, a cohesive zone-based finite element (FE) fatigue modelling framework was first verified on standard Mode I (DCB), Mode II (ENF), and Mixed-Mode (MMB) specimens, using experimental data from the literature. The framework was then applied to simulate the fatigue behaviour of the L-shaped specimen. Finally, the variation of energy release rate with crack-growth was investigated to explain the observed failure modes, highlighting the strong sensitivity of delamination growth to initial loading conditions.