Nonequilibrium molecular dynamics simulations of shock wave propagation in nanolayered Cu/Nb nanocomposites

Abstract

Employing nonequilibrium molecular dynamics simulations, we characterize the defect substructures induced in nanolayered Cu/Nb composites by shock compression, and their manifestation on macroscopic observables such as pressure, shear stress and temperature. We find that Cu lattice dislocations are initially nucleated at the Cu/Nb heterophase interface, and subsequently transmit into the neighboring Nb crystal. The nucleation of dislocations at interfaces may be partly attributed to the shear stress gradient across interfaces; although there is a good impedance match between Cu and Nb at the shock strengths we are considering, the interfaces introduce a periodic variation in the pressure and shear stress profiles, even during elastic loading. The resulting dislocation activity (nucleation and transmission) subsequently leads to local heating at those interfaces. These findings imply that by atomic design of interface structure and spacing, one might control the thermomechanical response of nanocomposites under extreme mechanical loadings. © 2012 American Institute of Physics.