Effect of thread tension on mechanical performance of stitched glass fibre-reinforced polymer laminates -experimental study

This article presents the results of interlaminar shear and flexural tests of polyester resin - glass fibre laminates made from the preforms unstitched and stitched by various thread tensions: low, medium and high. The laminates were impregnated using resin transfer moulding method. The interlaminar shear and flexural tests were conducted by loading parallel and transverse to the stitch lines. Interlaminar shear strength, flexural strength and flexural modulus were obtained. Deformation extent of the reinforcing structure of the stitched laminate increases with the increase in the thread tension and causes decrease in the flexural strength and modulus. However, the increase in the thread tension offers improvement in the interlaminar shear strength. Optimization of changes in the flexural properties and the interlaminar shear strength with the thread tension showed that an operation of stitching of the reinforcing preforms should be conducted by low or medium stitching thread tension (approximately 3-9 N).