Improvement of ballistic impact resistance using flattened roll design and $SiO_2$ shear thickening fluid impregnated fabric

Abstract

Aramid and ultra high molecular weight polyethylene(UHMWP) have been used as the basic materials for soft body armors. These materials have low weight and high strength compared to other materials. Although these fabrics are characterized by low density and high energy absorption, approximately 30~50 layers of fabric are required to be protected against ballistic threats. Weight of one bullet proof vest without a hard protective insert is around 5~7kg. It is too heavy for combatants to move around freely. In this paper, the impact resistant characteristics of shear thickening fluid (STF) impregnated fabrics and the effect of flattened roll design were investigated to increase the energy absorption of body armor. In this study, the ballistic impact characteristics of Kevlar $KM2\reg$ non-treated and plain woven fabric impregnated with shear thickening fluid was investigated. The STF was made of $SiO_2$ (100nm) powder in polyethylene glycol. STF increases the ballistic resistance of fabric by restrictions on yarn pullout. STF impregnated fabric has lower indentation depth than non-treated fabric at equal areal density. However, STF impregnated $KM2\reg$ was penetrated in lower velocity than neat Kevlar. Therefore, a novel design should be inserted playing an important role in impact velocity reduction before the STF impregnated fabric. Flattened roll designed UD ($Dyneema\reg$ UD-SB 31) was used to absorb the impact energy in front of the STF impregnated Kevlar. It has the advantage of 10~15% areal density reduction in comparison to other design. A hybrid type of flattened roll designed UD and STF impregnated fabric increases the ballistic resistance consequently reducing the body armor weight.