Effect of stitching parameters on mechanical properties of foam-core sandwich structure composites

The stitched foam-core sandwich composites with different stitching methods and stitch density were manufactured using vacuum assisted resin infusion (VARI) molding process. The effect of stitching parameters on their flatwise tensile, three-point flexural, core shear and climbing drum peel properties was investigated. The results show that although stitching makes flatwise tensile strength and core shear strength of foam-core sandwich composites to decrease obviously, it can improve flexural properties as well as substantially enhance climbing drum peel properties. Modified lock stitch method is better than tufting stitch method. Properly increasing stitch space has certain positive effect for mechanical properties, but it is not conducive to the enhancement of climbing drum peel properties. For modified lock stitched foam-core sandwich composites with the stitch density of 30 mm X 10 mm, flatwise tensile strength and core shear strength are reduced by 14.75% and 24.79%, respectively, whereas flexural strength and average peel strength are respectively increased by 7.96% and 80.78% compared to those of unstitched foam-core sandwich composites.