Improving stab resistance of soft body armor composites via modified shear thickening fluids (STFs)

This study examined shear thickening fluids (STFs) for soft armor composites. STFs, consisting of 55 wt.% silica nanoparticles in polyethylene glycol (PEG), have been used to boost the quasi-static and dynamic stab resistance of E-glass fabrics. To enhance the rheological properties of virgin STF (VSTF), we introduced modifications to the PEG chain structure through interactions with malonic and tartaric acid, resulting in the creation of MSTF and TSTF, respectively. Rheological analysis demonstrated that these modifications led to a substantial increase in viscosity, with MSTF and TSTF exhibiting approximately 25.92 and 5.92 times greater viscosity than VSTF, respectively. A series of quasi-static knife stab tests was conducted, revealing a significant improvement in peak force. Moreover, as stab loading speed increased, the energy absorption capacity of the materials demonstrated a direct correlation. Subsequently, we employed regression analysis with artificial intelligence techniques to predict knife stab resistance across various loading speeds. Our results established a robust relationship between force-displacement characteristics and knifing speed. Notably, the heightened viscosity of fabrics infused with TSTF, MSTF, and VSTF led to dynamic impact energy absorption values that were 1.74, 1.58, and 1.43 times higher, respectively, compared to the neat fabric.