The influence of fibre orientation and of the adjacent layers on the delamination of laminated composites

The paper presents a comparative analysis between different configurations of composite laminates with respect to the delamination onset and growth. The results are presented in terms of the total displacement jumps at the crack tip for an initial imposed displacement up to the final delamination. Therefore, the influence of fibre orientation and the suitable selection of the configuration of the composite laminates are discussed. Moreover, the effect of the adjacent layers on the interlaminar damage of composite laminates is analysed. In this context, a significant number of numerical models have been carried out for two different configurations of multi-layered composites, namely [05/+θ/+θ/05] and [05/+θ/-θ/05]. The influence of the orientation of the adjacent layers is investigated, as well as the sign of the fibre orientation angles. The analysed composite laminates are subjected to tensile opening fracture mode, considering a pre-existing initial crack located at the interface between the layers from the middle plane. The variation of the mode I opening displacement with respect to the fibre orientation angle of the adjacent layers is graphically illustrated. The obtained results show similarities in the variation of Poisson's ratio with respect to the fibre orientation. Therefore, the mismatch of the Poisson's ratio of the adjacent laminas may involve significant interlaminar stresses which can lead to a delamination failure or an opening fracture mode.