The present study is an experimental and computational investigation of shock wave propagation in multiphase suspensions. Particle suspensions are used as a means of obtaining a system in which there is limited initial inter-particle contacts with a large degree of parametric variability. The suspensions were prepared in ethylene glycol at several volume fractions (41%, 48%, and 54%) of silicon carbide particles, mixtures that have been shown to be shear thickening in rheological studies. The dynamic response of the shear thickening fluids is investigated in ranges of deformation relevant to ballistic impacts.
A series of plate impact experiments were conducted to obtain the shock Hugoniots of the various suspensions at particle velocities in the range of 200-900 m/s. The experimental results show a transition in the wave propagation behaviour from a regime of propagation dominated by the compressibility of the liquid phase of the suspension to a regime where the response of the mixture becomes dominated by inter-particle contact networks. The transition in the shock Hugoniots of the suspensions indicates a shock-induced stiffening of the suspensions. In situ longitudinal and lateral stress measurements are made in the intermediate volume fraction suspension at two different impact velocities demonstrating a deviatoric stress component to the stress state within the suspension.
Analytical and numerical models are employed to demonstrate the likely cause of the transition in the behaviour of the suspensions, resulting from the variation in the solid phase volume fraction of the suspension with increasing shock wave strengths. The results are discussed in terms of the development of extensive inter-particle contacts in a compression-induced mechanism analogous to classical shear thickening in dense suspensions.