Theoretical Prediction of the Stiffness and Failure Strength of Stitched Foam-Core Sandwich Composites

Abstract

Based on the microstructure, a novel theoretical method was proposed to predict the equivalent stiffness and failure strength for stitched foam-core sandwich composites. Experimental studies on stiffness and failure strength were also carried out. Considering the different thickness increment of the laminated face-panels for different stitching density and the influence of the stitching angle to the width of the resin pocket zone, a modified fiber distortion model was developed to evaluate the stiffness of stitching laminated face-panels by a combined series-parallel model. As for the prediction of failure strength, the composite face-panels were analyzed by the classical laminate theory and the local wrinkling failure of the face panel was also considered. A bridging model was adopted to analyze the stress of the stitched foam-core, and the failure strengths were predicted with proper failure criteria for different constitutive materials. The equivalent stiffness and failure strength of stitched foam-core sandwich composite panels were obtained under fat-wise loading, edge-wise loading, three point bending and transverse shear loading, respectively. The predicted results showed a good agreement with the experimental results and the finite element results, which demonstrated the validity of the present theoretical method.