Effectiveness of Different Shear Thickening Fluids in Reducing Back Face Signature (BFS) of Body Armor Against Bullet Impact

Abstract

Shear thickening fluid (STF) or liquid armor based flexible & light weight liquid armor is attraction for both defense and Civilians. In order to understand the contribution of shear thickening behavior on ballistic performance of STF coated Kevlar fabrics, STFs of different shear thickening behavior were prepared by varying the particle size (100- 1000nm) and concentrations (62-70%) of nanoparticles in polyethylene glycol matrix. STFs were coated on Kevlar fabrics using Mathis padding mangle. Ballistic Trials on STF Coated Kevlar fabrics were performed as per NIJ level IIIA using 9mm x19mm ammunition with projectile mass 7.45 g and velocity 430±15 m/s respectively. Roma Plastilina #1 is used as backing material for the measurement of Back Face Signature (BFS). It was observed that BFS reduced significantly with STF coating on Kevlar fabric irrespective of rheological parameters. BFS does not show significant difference for particle size 100-600nm and performance suddenly falls with further increase in particle size. It is further observed in present study that STF coating on Kevlar fabric shows improvement only up to an optimum concentration, beyond which there is decline in performance.