Development of novel auxetic textile structures using high performance fibres

The present work reports the first attempt of developing auxetic structures using high performance fibres through knitting technology. Polyamide (PA) and para-aramid (p-AR) fibres and their combination were knitted in to purl structures using flatbed knitting machine, varying different structural (such as loop length, cover factor and yarn density) and machine parameters (such as take-down load). The influence of different parameters on negative Poisson's ratio (NPR) was thoroughly investigated. It was observed that NPR improved strongly with the increase in loop length of knitted structures. NPR also increased with the decrease in cover factor and increase in course density of knitted fabrics. An increase in take-down load also improved NPR for tightly knitted samples, but led to initial decrease and subsequent increase in NPR for medium and higher loop lengths; except for p-AR fabrics, which showed a decrease in NPR with take-down load for higher loop lengths. Tensile properties of the developed auxetic structures were also found to depend strongly on fibre type and loop length, and the highest tensile performance was achieved with lower loop lengths and p-AR yarns. The p-AR fabrics produced using lower loop length and lower take-down load resulted in the highest NPR of - 0.713. Therefore, the developed knitted structures produced using high performance yarns and showing strong auxetic effects can have huge potential for industrial applications, especially in personal protection materials, such as cut resistance fabrics, bullet proof vest, helmets, and so on.