Improving the extension-twist coupling performance of practically warpage-free laminates via layup hybridization

This article investigates whether the extension-twist and bend-twist coupling performance of practically warpage-free laminates can be improved by layup hybridization (carbon/epoxy-glass/epoxy hybrids) compared to non-hybrid (mono) laminates. We performed numerical layup search by simulating the thermal warpage, and the bend-twist and extension-twist behaviour of 4096 4-ply layup permutations. The upper limit of allowable manufacturing-induced warpage was based on the ISO2768 standard. The optimal hybrid and mono layups were selected to have the most significant coupling performance within the allowable warpage range. A mono layup achieved the maximum bend-twist performance (which does not require layup asymmetry), but layup hybridization increased the extension-twist performance by more than 30% in the practically warpage-free range. The numerical results were validated through 3D scanning and 3D digital image correlation-aided mechanical tests. We concluded that layup hybridization can significantly improve the extension-twist performance of realistically usable composite laminates with negligible thermal warpage.