NOVEL FLEXIBLE BODY ARMOR UTILIZING SHEARTHICKENING FLUID (STF) COMPOSITES

摘要

The U.S. Army requires lightweight, flexible body armors that provide ballistic protection withoutsignificantly compromising soldier mobility and dexterity. Currently fielded systems employ multi-plyKevlar? fabric armors, whose bulk and stiffness make them practical only for torso protection. Toaddress this problem, we are investigating the ballistic properties of Kevlar fabrics impregnated withcolloidal shear thickening fluids (STFs). STFs are fluids that undergo a sudden and dramatic increase inviscosity above a critical shear rate, in some cases transforming to a material that exhibits solid-likebehavior. Impregnating Kevlar fabrics with this fluid results in a composite material which is flexible atlow strain rates, such as during normal soldier motion, but stiffens upon sudden impact to provideballistic protection. We have fabricated and tested a series of such materials. The shear thickening fluidis composed of silica particles with a nominal diameter of 446 nm at a loading of 57% v/v in ethyleneglycol. Special fabrication techniques are used to ensure that the STF fully wets the Kevlar fabric (plainweave, 600 denier, KM-2). The results show that, under the conditions tested, the ballistic performanceof the STF composite armors is equivalent to or slightly better than neat Kevlar armors of the sameweight. However, the STF armors require significantly fewer layers of Kevlar fabric than the neat Kevlararmors. The resulting STF armors are therefore significantly more flexible, and thinner, than theconventional materials. Ballistic results for a range of STF composite architectures and materials will bepresented and compared, and mechanisms for the enhanced ballistic performance will be proposed.