Investigating the impact response of fumed silica based shear thickening fluids using split Hopkinson pressure bar technique

Abstract

Shear thickening fluids (STFs) are classified as a sub-class of non-Newtonian fluids, which have emerged as promising smart materials, wherein their viscosity increases dramatically under the applied shear stress. In this study, STF comprising of Fumed silica (A200) and Polyethylene Glycol (PEG400), was synthesized, and characterized to evaluate its potential for impact mitigation applications. Steady shear rheological testing demonstrated a clear temperature dependence in viscosity behavior. At lower temperatures, the shear thickening fluid (STF) exhibited earlier and more pronounced thickening with higher viscosity increase, while at higher temperatures (45 °C), the onset was delayed as well as the severity of thickening reduced, showing that temperature greatly influences particle interactions and fluid resistance. Additionally, Split Hopkinson Pressure Bar (SHPB) test rig was used to study STF’s response under high strain rate compressive loading conditions. The parameters that were used to evaluate STF’s performance were average specimen stress, critical strain, and impact toughness under varying strain rate conditions. It was found that STF exhibited rate sensitive behaviour, changing from a low-viscosity fluid to a high viscosity solid, rigid, energy-dissipative material with the increasing strain rate. The highest specimen stress was observed to be 185.99 MPa at a strain rate of 41,411 s⁻¹. Also, at this strain rate the impact toughness of the specimen was found to be highest, 168.46 MJ/m3. However, with the further increase in strain rates, the peak stress, critical strain, and impact toughness exhibited drop in values, the trend being non-linear in nature. Thus, the strain rate of 41,411 s− 1 was termed as the Limiting Strain Rate (LSR) for the STF under study, which corresponded to peak performance of STF under dynamic compressive loading conditions. © The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering 2026.