Delaminations growth in compression after impact test simulations: influence of cohesive elements parameters on numerical results

The compressive strength of impact damaged composite laminates may be reduced by ply damage and delaminations, which may grow under load. At coupon level, the residual strength of impacted laminates is assessed through Compression After Impact compression after impact (CAI) tests; as a complement to the experiments, numerical tools are sought that predict the behavior of delaminated composites. In this context, the paper investigates the influence of the cohesive elements parameters -– the inter-facial strengths and the cohesive mesh size -– in CAI test simulations. The study is carried out using a recently developed initialization technique that allows CAI simulations be run independently from the impact simulations (used to calculate induced delaminations). The first part of the study uses a conventional sequential approach (CAI analyses follows the impact simulations which share the same parameters) to asses the sensitivity of force time histories and in-plane delaminations growths to parameters variation. Then, for a selected initial damage scenario, the inter-facial strengths sensitivity is performed also evaluating the computational efficiency. The study shows how the cohesive parameters affect both the accuracy and the computational cost of the analyses and contributes to establish guidelines for an effective use of cohesive elements in CAI tests simulations.