Tensile behavior of weft knitted glass/epoxy composites with laid-in yarns

Tensile behavior of mono-layer and multi-layer composites of weft knitted glass fabric in an epoxy matrix has been studied. The knitted fabric had a knit/knit stitch structure. The effect of laid-in yarns on the composite properties was examined by utilising knitted fabrics with 0% (i.e., no laid-in yarns), 2.2% and 4.4% by volume of laid-in yarns in the weft direction. It was observed that the laid-in-yarns, even at the small volume fractions used in this study, significantly improved the weft-direction strength and stiffness of the composites without having any adverse effect on the warp-direction properties. Increasing the number of fabric layers from one to three led to major enhancements in the weft-direction strength and fracture strain of the composite with 4.4% laid-in-yarns, due to the larger number of bridging laid-in yarns.