Multi-scale simulation of stitched foam-core sandwich composites subjected to low-velocity impact

Multi-scale approach has been developed for evaluating the damage resistance of sandwich structures composed of stitched foam-core and woven face sheets subjected to low-velocity impact. Simplified model of stitched foam-core was established. The classical theory of homogenization was adapted and used by treating the foam strengthened by the glass fiber resin column as orthotropic equivalent core material which elastic properties depended on each component and their volume participation. And finite element model of sandwich structure was established. Interface elements were added between panels and foam-core to simulate the initiation and propagation of adhesive disbond damage. Impact behaviors of the stitched foam-core sandwich composites were calculated with GENOA progressive failure analysis commercial software and compared with those in experimental. Good agreements between numerical and experimental were found, which demonstrates the validity of the multi-scale progressive failure analysis method. The analysis shows that the damage in upper panel and delamination between panels and foam-core reduce effectively when the sandwich composites stitched. However, stitches brought initial damage to the structure; higher stitch density increased the foam-core stiffness, as a result, reduced energy absorption capability of sandwich structures.