Finite element analysis of mode II delamination suppression in stitched composites using cohesive zone model

To provide an accurate prediction of mode II delamination properties of stitched composites, a single stitched laminate under pure shear load (interlaminar shear) is investigated. An interlaminar shear test (IST) is conducted, using a specially constructed fixture. A finite element model of the IST is developed, using a spring connector to represent the stitch thread. Furthermore, an end notch flexural test is simulated based on the IST model and with a cohesive zone element used to simulate crack propagation. The effects of the cohesive zone modelling parameters (interfacial strength, stiffness and viscosity coefficient) are also investigated. Close agreement is obtained between the simulated and experimental results. Finally, the verified model is extended to study the effect of the number of stitch rows in the crack region. The results confirm that the crack propagation starting point (peak load) depends on the number of stitch rows in the crack region.