Characterizations of STF-Treated Aramid Fabrics Using Picture Frame Test

Abstract

Shear thickening fluid (STF) is a non-Newtonian fluid featuring the increased viscosity upon high strain rate applied. Recently, STF-treated aramid fabrics have been researched to enhance the bulletproof efficiency maintaining the lightweight, however their shear properties including tow shearing, which significantly contribute to the bulletproof properties, have not been characterized, in particular under high shear strain rates. In this study, the shear properties of STF-treated aramid fabrics are characterized using a picture frame test. For this purpose, STF is prepared using polyethylene glycol and silica colloids and coated onto aramid fabrics. Varying the shear strain rate by controlling the pulling speed of the picture frame, the effect of STF on the shear properties of the aramid fabric is investigated. Finally, the shear properties of STF-treated aramid fabrics are predicted a multi-scale energy model and compared with the experiments. This prediction is then extended to cover such a high strain-rate situation as the bullet impacts, enabling to determine the mechanism behind the improved bulletproof performance of the STF-treated fabric.