Drop-weight Impact Behaviour of a Shear Thickening Fluid in a Finite Volume

Abstract

This thesis aims to study and explore the drop-weight impact-induced solidification process of an STF, consisting of 58 vol% styrene/acrylate particles in ethylene glycol, in a finite volume. The study begins with the characterisation of the mechanical behaviours (i.e., rheological and confined compression behaviours) of the STF. Low-velocity drop-weight impact experiments are conducted to investigate the effect of the STF’s dimensions in a finite volume on the impact behaviour of the STF. It is found that the impact behaviour is related to both the depth and the diameter of the STF. A new model is therefore proposed that the solidification front of an STF advances linearly to the impact velocity with a constant ratio in both the normal and radial directions, respectively, forming a semi-ellipse-like region which is captured by a direct observation with a high-speed camera. When this front propagates to one boundary, a force transmits back to the impact head. The interaction is detected by the load cell and piezoelectric transducers at the boundaries. Moreover, the coupled Eulerian-Lagrangian model and the volume of fluid model are adopted to simulate the development of the solidification front. In both models, the continuous propagation of the solidification front is depicted by expanding of a high-strain-rate region in all directions. The energy absorption under the drop-weight impact is found to decrease with an increase in the depth or width dimension of the STF before their critical dimension is reached due to the extension of the solidification period. Finally, the displacement-control oscillations are conducted on the STF to further explore its reciprocating performance for characterising the resistant force and energy absorption. It is found that the amplitude of displacement has a clear effect on the resistant force and energy absorption, while the frequency has little influence on them after the activation of the shear thickening.