Yarn dynamic tensile behavior and meso-scale numerical simulation method for STF-Kevlar fabrics

Abstract

Shear thickening fluids (STFs) were found to be effective at enhancing the energy absorption capacity of Kevlar fabrics, which is promising in the area of soft-wall containment casings. In the current study, an improved mesoscale numerical simulation method for the yarn level was developed to predict the properties of STF-Kevlar fabrics with various STF concentrations. In addition, quasi-static and dynamic tensile tests as well as yarn pull-out tests were performed. Based on the dynamic tensile behavior and friction between yarns, a mesoscale numerical simulation method was proposed for STF-Kevlar fabrics. Combined with a ballistic impact test, the numerical simulation method based on the yarn tests was verified. It was found that the STF generates a strain-rate strengthening effect due to its shear thickening behavior during quasi-static tensile tests conducted at 0.0001 and 0.001 s−1. The initial elastic modulus, tensile strength, and failure strain of the yarn were obtained from dynamic tensile tests using a split-Hopkinson tension bar (SHTB) apparatus. The yarn pulling process includes the yarn straightening stage and yarn translation stage. The pull-out force decreased with the pull-out rate for the STF-treated yarn. The pull-out force of the STF-treated fabric increased by up to 213.2% compared with the neat fabric at the same pull-out rate. Based on the yarn pull-out testing results, the friction coefficient between the weft and warp yarns was estimated. Mesoscale numerical simulations were performed based on the dynamic tension behavior and friction behavior of the yarn, which were verified through ballistic impact test. Although the friction characteristics of the three STF fabrics were not significantly different, the energy absorption of the STF-treated fabrics differed considerably. As the tensile strength increased, the energy absorption characteristics of the fabric improved considerably.