Effect of stitch density on mechanical properties of stitched composites manufactured by VARI process

Abstract

The carbon fiber/epoxy resin composites with different stitch density were manufactured using modified lock stitching and vacuum assisted resin infusion (VARI) molding process. The influence of stitch space and stitch pitch on mechanical properties of the composites was investigated. The optimum stitch density was obtained. The results show that with increasing stitch space, both tensile and flexural properties enhance and interlaminar shear strength increases first and then decreases. With the increase of stitch pitch, both tensile and flexural properties exhibit an increasing trend. The stitched composites have the optimum integrated mechanical properties when the stitch density is 5 mm×8 mm. Their tensile strength, tensile modulus, flexural strength and flexural modulus reduce by 13.3%, 12.7%, 23.0% and 25.2%, respectively, whereas the interlaminar shear strength increases by 11.3% compared to the unstitched composites.

Keywords

• stitching
• composite
• vacuum assisted resin infusion
• mechanical property