Solidification of a shear thickening fluid in a finite volume under low-velocity impact

Abstract

Shear thickening fluids show a reversible viscosity increase and even a transient solid-like behaviour when the shear rate is above a critical value, hence they are widely used as an impact energy absorber. This work aims to characterise the low-velocity impact behaviour of an STF in a finite volume in a container − a situation where the material is normally used in a real-life application. The STF contains 58 vol% styrene/acrylate particles dispersed in ethylene glycol. Instrumented drop-weight impact tests are carried out, with transducers attached on the striker, the bottom and the side wall of the container, to characterise the low velocity impact-activated solidification behaviour of STF, addressing the effect of the finite volume. A new two-dimensional mechanistic model is proposed to describe the evolution of the solidification of the STF with a finite volume under the low-velocity impact. It was found that the impact-activated solidification of the STF is clearly dependent on not only the depth of the STF, as reported in previous studies, but also the radial dimension of the STF. In addition, the propagation velocities of the solidification front, in both the depth and radial directions, are found to be linearly proportional to the impact velocity.