Single-yarn pull-out test in neat, solvent-treated and shear-thickening fluid-impregnated Kevlar® KM2 fabric

Abstract

Purpose In order to help explain experimental findings related to the stabbing- and ballistic-penetration resistance of flexible body-armor, single-yarn pull-out tests, involving specially prepared fabric-type test coupons, are often carried out. The purpose of this paper is to develop a finite-element-based computational framework for the simulation of the single-yarn pull-out test, and applied to the case of Kevlar® KM2 fabric. Design/methodology/approach Three conditions of the fabric are considered: neat, i.e, as-woven; polyethylene glycol (PEG)-infiltrated; and shear-thickening fluid (STF)-infiltrated. Due to differences in the three conditions of the fabric, the computational framework had to utilize three different finite-element formulations: standard Lagrangian formulation for the neat fabric; combined Eulerian-Lagrangian formulation for the PEG-infiltrated fabric (an Eulerian subdomain had to be used to treat the PEG solvent/dispersant); and combined continuum Lagrangian/discrete-particle formulation for the STF-infiltrated fabric (to account for the interactions of the particles suspended in PEG, which give rise to the STF character of the suspension, with the yarns, the particles had to be treated explicitly). Findings The results obtained for the single-yarn pull-out virtual tests are compared with the authors’ experimental counterparts, and a reasonably good agreement is obtained, for all three conditions of the fabric. Originality/value To the authors’ knowledge, the present work represents the first attempt to simulate single-yarn pull-out tests of Kevlar® KM2 fabric.

Incorporation of shear thickening fluid effects into computational modelling of woven fabrics subjected to impact loading: A review

“…Significant reduction in computation costs in terms of elements, memory and required solving time has been achieved in comparison with the traditional, meso-scale model (Yang et al, 2018). Taking a step beyond meso-scale modelling, Grujicic et al (2017) reached the fibre/filament level/micro-scale modelling of a fabric. However, the modelled fabric consists of only eight yarns (five and three in warp and weft directions, respectively) to minimise the computational time.…”

“…Therefore, the frictional coefficient is independent of the material and fibre/yarn surface properties. In general, the static frictional coefficient is largely governed by the surface topology/roughness of the yarns, while the dynamic counterpart is mainly controlled by the constituent material (Grujicic et al, 2017). Therefore, equation (2) may be a better approach than equation (4) for practical applications.…”

“…Consequently, modelling exercises should further focus on explicit modelling of the STF domain. Grujicic et al (2017) developed a computational framework for the simulation of a yarn pullout test applicable for STF-impregnated Kevlar KM2 fabrics using ABAQUS FEM code. The model used was of high resolution and was beyond the meso-scale (yarn-level), with each yarn containing 37 parallel fibres modelled explicitly, as described in section 'Various approaches to numerical modelling of fabrics'.…”