the flexural behavior of stitched polyurethane foam composite sandwich structures

One of the main advantages of sandwich composites is the high bending strength to their weight ratio. these structures have significant problems such as face sheet-core de-bonding, which could be prevented by a variety of techniques including z-pining and stitching through the thickness. in this study, the effect of stitching on the bending behavior of sandwich composites with e-glass composite face sheets and polyurethane foam core has been investigated. specimens are stitched at three stitch spaces of 0.5, 1, and 2 cm with stitch pitch of 0.8 cm and stitch seam angles of 0, 90°, 0/90°, ±45°, 45°/90°, and ±60°. face bending stress and core shear stress of stitched specimens have been studied by a three-point bending test and compared to the results of unstitched specimens. results indicate that by decreasing the stitch spacing and therefore increasing the stitch density, bending strength improves, and the best bending behavior is observed in the ±45° stitch angle sample.