The blast resistance of stitched sandwich panels

The effect of through-the-thickness stitching on the blast resistance of sandwich panels is investigated both experimentally and numerically. Panels based on three-dimensional woven S-glass/epoxy skins and a crosslinked PVC core were manufactured using a vacuum assisted resin infusion process. The panels were stitch-bonded using Kevlar 129 yarn, by means of a multi-needle stitch-bonding machine developed in a previous investigation. The performance of both orthogonal (0) and biased (45) stitching procedures were considered and their respective responses were compared to that of a similar unstitched panel. The blast resistance of the sandwich panels was modelled using finite element techniques. An examination of the blast-loaded samples highlighted a number of failure mechanisms, including crushing of the foam core, skin-core debonding, fracture of the glass fibre/epoxy skins, fibre-matrix debonding with fibre pull-out and delamination. If evaluated on the basis of specific impulse (applied impulse normalized by plate mass), the results indicate that stitching has no obvious effect on the blast resistance of the sandwich structures. Agreement between the finite element models and the experimental data was good over the range of loading conditions considered. Here, the FE models accurately predicted the overall deformation responses of the panels and also captured the primary failure modes.