Double-shock-induced spall and recompression processes in copper

Spall damage caused by multiple shockwaves is a crucial and significant issue worth exploring. Herein, we perform molecular dynamics simulations to investigate shock damage and the recompression process in double-shock-loaded copper. Compared to the traditional spall signal, two significant velocity peaks with different time intervals between peaks are observed in the free-surface velocities under two shock loadings. The dynamic processes are then revealed via the evolution of voids and the complex propagation of waves. Meanwhile, the states of the recovered samples after shock loading are found to depend on the loading conditions. Both intact samples that undergo recompression and broken samples with separated spall scabs are observed in our simulations. Secondary spallation is observed after the recompression process, and the associated spall strength is significantly lower than that under the first shock loading. Recrystallization is observed in the spall region after secondary shock loading with a remnant of highly localized plastic deformation. The simulation results are confirmed based on the thermodynamic properties of the samples obtained via the temperature–pressure pathway.