Strain-Wave Reflections During Ballistic Impact of Fabric Panels

Abstract

A numerical model is presented which describes the strain level build-up in yarns due to multiple strain wave reflections from yarn crossover intersections in a woven fabric subject to ballistic impact. Crossing yarns present barriers from which strain waves are partially reflected. The maximum yarn strain occurs at the point of impact and decays with distance along the yarn away from this point. The rapidity of decay is governed by the crossover reflection coefficient. Using observations of the deformation cone size of ballistically impacted fabric panels, it is concluded that the reflection coefficient is small (approximately 0.01). The strain increases with time at different rates for different reflection coefficients until failure at the impact point. Extensions of this model to other fibrous structures are discussed.

Effect of structural hybridization on ballistic performance of aramid fabrics

“…This causes the yarns to displace towards the back of the fabric and therefore higher trauma depth is created. 14…”

Recent advances in modeling and experiments of Kevlar ballistic fibrils, fibers, yarns and flexible woven textile fabrics – a review

“…The 'local' nature of impact event is indicated by a small degradation of the tensile properties of yarns that are extracted from a shoot pack away from the impact location 149 . Strain wave reflection, noted by Freeston and Claus 150 , at the yarn cross overs can increase the strain level depending on the reflection coefficient. Although length and width of the fabric is larger than the thickness, impact is a 'local' event causing significant transverse deformation initially which is largely neglected by the continuum scale homogenized approaches.…”

Formation and properties of fluid jet entangled HMPE impact resistant fabrics

“…Textile materials currently used include woven fabrics, unidirectional sheets, fibre reinforced composite panels and nonwoven structures. Generally, in fibre assemblies yarn or fibre crossovers behave as partially fixed ends from which an incident strain or shock wave, which is introduced by a ballistic impact, is partly reflected and partly transmitted past the crossovers [11]. Thus, in a woven fabric these crossovers magnify the strain levels so that the elongation in the yarn may reach its maximum and elongation at break or yarn breakage occurs.…”