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A criterion for matrix failure of laminated composite plies in transverse tension and in-plane shear is developed by examining the mechanics of transverse matrix crack growth. Matrix cracks are assumed to initiate from manufacturing defects and can propagate within planes parallel to the fiber direction and normal to the ply midplane. Fracture mechanics models of cracks in unidirectional laminates, embedded plies and outer plies are used to determine the onset and direction of propagation of crack growth. The models for each ply configuration relate ply thickness and ply toughness to the corresponding in-situ ply strength. Calculated results for several materials are shown to correlate well with experimental results.

Abstract3D failure criteria for laminated fibre-reinforced composites, based on a physical model for each failure mode and considering nonlinear matrix shear behaviour, are developed. Special emphasis is given to compression failure. The physical model for matrix compression failure is based on the Mohr-Coulomb criterion and also predicts the fracture angle. For fibre kinking, an initial fibre-misalignment angle is considered to trigger failure, due to further rotation during the compressive loading. The plane where the kinking takes place is predicted by the model, as well as the kink-band angle. Applications are presented that validate the model against experimental data.