The effect of stitching on the low-velocity impact response of delaminatedcomposite beams

A numerical simulation is performed to predict the effects of stitching on the low-velocity impact response of stitched delaminated beams. The load/di splacement relations during the impact are assumed to be the same as in the corresponding static problem. Hence a solution to the problem of a stitche d delaminated beam under a static contact force is developed. The effects o f stitches are modeled as a constant shear traction in the stitch bridging zone to account for the shear resistance offered by the unbroken stitches. From the static simulation the load/displacement and displacement/crack-ext ension relations are obtained. From the area under the load/deflection diag ram the apparent fracture toughness due to the stitching is also estimated. The impact simulations provide information on the load at which the crack propagation initiates, the maximum contact force, and the extent of crack p ropagation at the end of the impact event. The results indicate that stitch ing does not increase the load at which delamination begins to propagate, b ut greatly reduces the extent of delamination growth at the end of the impa ct event. (C) 2000 Elsevier Science Ltd. All rights reserved.