Investigation of impact damage in multi-directional tape laminates and its effect on local tensile stiffness

This paper examines the effect of impact damage on local tensile stiffness of multi-directional tape laminates. A finite element model is used for parametric studies of the effect of various patterns of delaminations and cracks across the fibres. Regular and random crack patterns are considered for 8 and 16 ply quasi-isotropic laminates. The effect on local stiffness is evaluated by a recently developed inverse numerical approach. It is found that fibre cracks control the loss of stiffness but that delaminations are instrumental in extending the zone influenced by these cracks. Fractographic observations are finally used to generate a detailed model of the damage in a real laminate. A close agreement was found between the predicted and measured strain fields and the corresponding stiffness distributions obtained with the inverse method.