Development of soft composite materials with improved impact resistance using Kevlar fabric and nano-silica based shear thickening fluid

The application of shear thickening fluid (STF) on Kevlar fabrics improves the impact energy absorption by the soft composite as the viscosity of the former increases drastically during impact. The influence of process parameters like padding (squeezing) pressure and silica concentration in STF on impact performance of Kevlar-STF soft composite has been investigated in this research. The impact energy has been measured by dynamic impact tester as well as by low speed bullet impact test using a 0.380 Caliber revolver. Higher STF concentration improves the impact energy absorption by the Kevlar-STF soft composite. Higher padding pressure reduces the STF add-on% on Kevlar fabrics making the composite lighter. However, the impact energy absorption by the Kevlar-STF composite increases with the increase in padding pressure due to better and uniform distribution of STF within the fabric and yarn structures. The beneficial effect of higher padding pressure on impact energy absorption was also verified by the low velocity bullet impact test. At optimum process conditions, the impact energy absorption by Kevlar-STF soft composite goes up by around 150% and 400%, depending on the type of Kevlar fabric.