Enhanced Impact Resistance of Polyurethane Foam Composites Reinforced with Shear Thickening Fluids and Multi Wall Carbon Nanotubes

Abstract

Lightweight, impact-attenuating foams that can dissipate large amounts of kinetic energy are essential for modern helmets, automotive knee-bolsters, and blast-mitigation panels, where every added gram reduces wearer fatigue or fuel consumption while safety requirements continue to rise. However, conventional polyurethane foam has limitations in resisting sudden deformation under high-impact forces. To address this gap, the present work evaluates polyurethane foam impregnated with a shear-thickening fluid (STF) that contains 0–1.2 wt % multi-walled carbon nanotubes (MWCNT), with the goal of identifying the optimum formulation for peak-force mitigation and energy-damping efficiency. STF with 1.2 wt % MWCNT achieved the highest peak viscosity (188.41 Pa · s), delivering an optimal shear-thickening response. Foam treated with this formulation exhibited a 35% reduction in peak force and a 29% increase in impulse during 1.3 m drop tests (1200 g mass) compared with untreated foam, while SEM revealed only minor cell-wall distortion. These findings demonstrate a practical pathway to engineer ultralight, high-performance impact-mitigation foams for personal protective equipment and transportation safety systems, and lay the groundwork for future studies on cyclic durability, fire behaviour, and large-scale manufacturing of STF-nanotube-reinforced foams.