Downstream Effects of Particle Clustering in Heterogeneous Powder Mixtures under Shock Compression

Heterogeneous, multiphase materials with topological complexities manifest changes in the shock compression process which can induce localization effects in small neighborhoods, as well as downstream effects carried by the propagating wave. Local property contrasts in packed particle beds induced by the clustering of particles of the same phase magnify the propensity for flow instabilities via plastic extrusion through harder material in the proximity of the compressed particles. These effects modify the shock wave and therefore affect the bulk thermodynamic state achieved by the compacted shock compressed particles. Pressed powder compacts can show preferential particle clustering due to the manufacturing process and even small changes in clustering can lead to large differences in localization and final predicted equation of state. The effects of particle clustering and other heterogeneities in the microstructure of pressed powder compacts are investigated in this work via microstructural descriptor functions and microstructure-based simulations of the shock compression phenomena in real and synthetic microstructures. Distinct microstructures with the same stoichiometry of phases but different particle clustering distributions are compared based on their wave profiles, density of hot spots/flow structures, and evolving correlation functions that fully describe the microstructural features of interest. This preliminary work will show the importance of fully quantifying local effects vs. volume/mass-weighted homogenized properties when predicting the performance of a specific heterogeneous material composition.