Learning the initial mechanical response of composite material: structure evolution and energy profile of a plastic bonded explosive under rapid loading.

Plastic bonded explosive (PBX) is a typical composite material used widely in the defense industry and in aerospace engineering. The mechanical behavior of PBX is an important factor to be considered in its formulation design, but the initial mechanical response is not well understood due to the complexities of atomic interactions in a multi-component system. We applied a hybrid force field to investigate the initial mechanical response of cyclotrimethylenetrinitramine(RDX)-based PBX, by molecular dynamics. The structure evolution shows that the initial damage occurs mainly in the binder region, and is caused by conformational stretching and void propagation. The relationship between loading rate and initial damage indicates that lower loading rate is more beneficial to conformation relaxation, and consequently to increasing strain limitation. The energy profile indicates that the variation of non-bonded interaction energy, especially coulomb energy, has a significant influence on the variation of total energy. Therefore, when designing PBX, good mechanical strength can be expected by selecting polymer and explosive formulations with strong electrostatic interaction. Graphical abstract The structure evolution and energy profile of plastic bonded explosive (PBX) under uniaxial tension.