Enhanced reactivity by energy trapping in shocked materials: reactive metamaterials for controllable output

Abstract

Through the use of carefully designed numerical experiments on an explosive system, that use predictive models for subcomponents and multi-material simulation, we demonstrate enhanced reactivity by energy trapping in regions of the reactive flow that were previously shocked. Particles and inclusions are placed in designed patterns in an explosive matrix. New capabilities in additive manufacture make it possible to consider novel designs, that we refer to as ‘reactive metamaterials’. For a fixed amount of energy delivered by a shock impactor, an explosive that normally would not detonate, will detonate when particles are included. Enhanced reactivity correlates precisely with a change in the partition of energy from kinetic to internal, via reflective processes and flow stagnation in high pressure systems. We analyse cases associated with high shock impedance tantalum particles, and void inclusions, individually and placed in a test array. High impedance reflectors trap energy in regions of pre-shocked material. Whereas void shock collapse causes depressurisation of the material along with rapid material flow, and high pressure spot formation related to the jet impact blast. We analyse how these limiting cases of high impedance particle arrays and void arrays partition specific kinetic and internal energy, during the shock impact transient on the system of matrix explosive and embedded particle/voids. Both generate specific flow fields, pressure and temperature cycles in the matrix material over interval times, determined by the particle/void size and placement. Design variations of the configurations presented here can be tested by both experiment and simulation, and can be searched for optimal designs, aided by modern machine learning search methods.