Numerical simulation of the effect of stitching on the delamination resistance of laminated composites subjected to low-velocity impact

The paper illustrates the use of Finite Element (FE) analyses for the simulation of the effect of through-thickness stitching on the structural and damage response of composite laminates subjected to low-velocity impact. An FE model based on the use of progressive damage schemes for modelling intralaminar and interlaminar damage and accounting for the bridging action of stitching threads was developed in the study. Individual stitches were modelled by solid elements inserted along the thickness of the laminate and connected to the adjacent layer elements through cohesive interface elements. The predictions of the model were assessed by comparison with experimental data obtained by drop-weight impact tests on [03/903]S and [0/90]3S carbon/epoxy laminates. The numerical results were found to be in good agreement with the experimental observations in terms of force histories, force-deflection curves and internal damage induced by impact. In particular, the proposed model was able to correctly predict the effect of stitching on the damage response of the laminates at different impact energies and to capture the influence of the layup on the efficiency of stitching for improving the delamination resistance of the laminated samples.