Damage growth in constrained angle-ply laminates under cyclic loading

Damage initiation and growth under quasi-static and cyclic loading of constrained angle-ply laminates [0/±θ4/0] are investigated. Three angle-plies were studied with θ=25°, 45°, and 75°. The life to initiate matrix cracking, the onset of delamination and the saturation of matrix cracking in the three laminate geometries have been determined. It is found that the onset of stiffness reduction coincided with the damage observed visually. The lowest stiffness drop occurred in the [0/±254/0]T laminates with the lowest edge crack density. In contrast, the [0/±754/0]T laminates which developed through-width cracking, had the highest stiffness drop. It was observed that when both the in-plane shear and tensile normal stresses in the direction of fibre were high, the crack density became the largest, e.g. the [0/±454/0]T laminates.