Influence of Stitch Density and Stitch Thread Thickness on Compression After Impact Strength of Stitched Composites

This study aims to investigate the influence of stitch density and stitch thread thickness on compression after impact (CAI) strength of stitched composites. Unstitched laminated composites and specimens stitched with varying stitch density and stitch thread thickness are subjected to impact damage and then compressive loading. It is shown that stitched composites have higher CAI strength than unstitched counterpart due to smaller impact-induced delamination area, where local buckling occurs during compressive failure. However, it is revealed that the effectiveness of stitching in suppressing delamination growth and inhibiting sublaminate buckling under compressive loading is intimately related to stitch density. It is also found out that stitch thread thickness has little influence on CAI strength at low impact energy level, but has considerable effect at high impact energy level