Porosity and specific surface area dependence of shock-induced plasticity and melting in open-cell nanoporous Cu

We systematically study the plasticity and melting behavior in shock loading, as well as their dependence on porosity (ϕ) and specific surface area (γ) for nanoporous copper (NPC), by conducting large-scale non-equilibrium molecular dynamics simulations. During shock compression, the plasticity (i.e., dislocation slips) is dominant at lower impact velocities, while melting is governing at higher impact velocities. With increasing ϕ, both the plasticity and melting undergo the transitions from “heterogeneity” to “homogeneity” along the transverse directions. The increase in γ prompts an apparent heat release and gives rise to the transition from local plasticity to uniform solid disordering at lower impact velocities, while accelerates the melting at higher impact velocities, by converting more surface energy into internal energy. Upon impact, shock-induced pores collapse accelerates the consolidation of NPCs and is controlled by two mechanisms, i.e., the shearing ligament, prompted by plasticity, under low-velocity impact, and the internal micro-jetting facilitated by melting under high-velocity impact.