Design strategy for optimising weight and ballistic performance of soft body armour reinforced with shear thickening fluid

This study presents some soft armour panel design strategies using shear thickening fluid (STF) reinforced Kevlar(R) fabric. The effect of size of silica nano and sub-micron particles on the ballistic performance of soft body armour panels against the small arms ammunition (velocity similar to 430 +/- 15 m/s) has been analysed. Two STFs, namely STF-500 and STF-100, were prepared by dispersing silica particles of 500 nm and 100 nm diameter, respectively, in polyethylene glycol (PEG) 200. Kevlar(R) fabrics were impregnated with both the STFs. Multiple layers (20-24) of fabrics were stitched to prepare 13 soft armour panels which were evaluated for back face signature (BFS) against 9 x 19 mm lead core bullet. Soft armour panels comprising of fabrics impregnated with STF-500 yielded lower BFS than the respective panels comprising of fabrics impregnated with STF-100. This study also revealed that STF impregnation of Kevlar(R) fabrics can reduce the BFS by 2.5 mm-2.8 mm while keeping the areal density of the panel same (5 kg/m(2)). The areal density of soft armour panel can be reduced further by 10% (4.5 kg/m(2)), while keeping the BFS comparable to or lower than that of an STF impregnated homogenous panel, by judiciously placing the STF impregnated fabrics at the rear side while neat fabrics are placed at the strike face of the panel. STF impregnated panels were found to stop the impacting bullet earlier than neat panel.