| In recent years, with the frequent occurrence of terrorist incidents and the enhancement of people’s self-protection consciousness, the body protection is becoming an important global issue, particularly defending the menace from daggers, bayonets and so on. There are more and more researches on stab-resistant products at home and abroad recently. But most of those are based on single structure, and are woven fabrics、non-woven fabrics and so on. Also there is a small amount of research work on weft-knitted fabrics and warp-knitted single-face fabrics, but most of all were limited to the speculative stage. The stab-resistant structure and property of warp-knitted spacer fabrics have not been studied yet.Based on the comparison among several kinds of high performance fiber raw materials, ultra-high molecular weight polyethylene (UHMWPE) is chosen to knit different structural warp-knitted spacer fabrics as stab-resistant materials. Firstly, the twist test was conducted on UHMWPE fibers. A protective under-twist of50twists/m was thrown on the UHMWPE fibers without sacrificing mechanical property. Experiments proved that the yarns with a protective low twist were beneficial to knit on the double rib warp machine. The warping and knitting performances of UHMWPE fibers were discussed. The problems and solution during warping and knitting were also analyzed. All of this made the knitting of UHMWPE-warp-knitted spacer fabrics be successfully. With reference to The People’s Republic of China GA68-2008"stab resistance body armor for police" standards and the world’s most authoritative performance test standard NIJ The quasi-static and dynamic stabbing tests were conducted to study the relationship between the stab resistance and fabric density, thickness of warp-knitted spacer fabrics and the shear thickening fluid (STF). Quasi-static stab-resistant performance test results showed that, under the premise of knitting, the stab resistance of higher-density warp-knitted spacer fabrics performed better. The warp-knitted spacer fabric with a proper distance of knock-over bar had a best stab-resistant property. But in a certain thickness (8mm), the fabric would reach the best comprehensive stab resistance. Secondly, the STF applied only to lower-density warp-knitted spacer fabrics. The weight of higher-density fabrics after dipping increased obviously, affecting the comprehensive stab resistance. Dynamic stab-resistant performance test results showed that, warp-knitted spacer fabrics deformed severely under stabbing. It’s better to compound with compacted materials to make soft stab-resistant body armor. Lastly, the project simulated the stab-resistant behavior of warp-knitted spacer fabric by the curve of penetration force versus penetration depth and ANSYS/LS-DYNA. The stab-resistant characteristic of warp-knitted spacer fabrics was also analyzed. The stretching and shearing of warp loops cooperating with the compression deformation of spacer structure resisted the impactor penetrating together. It would achieve the best stab-resistant results. The simulation showed that the increase of compactedness and bending rigidity would decentralize the penetration stress, enhancing the stab resistance of warp-knitted spacer fabrics.The topic studied the stab-resistant performance of warp-knitted spacer fabric made of UHMWPE fibers for the first time, demonstrating the feasibility of developing soft stab-resistant products with warp-knitted spacer fabrics. Warp-knitted spacer fabric as a new type of stab-resistant material has a considerable advantage and opens up a new direction for areas of domestic research of stab-resistant materials and also makes a certain contribution for individual protective armor development. |
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