The flexural behavior of Stitched Polyurethane Foam Composite Sandwich Structures

Abstract

AbstractOne 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 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 has been studied by three-point bending test and compared to the results of unstitched specimen. Results indicate that with decreasing the stitch spacing and therefore increasing the stitch density, bending strength improves, and the best bending behavior observed in ±45° stitch angle.