Atomistic response of monocrystalline boron carbide to dynamic triaxial tension

Response of monocrystalline boron carbide to dynamic triaxial tension has been investigated using molecular dynamics simulations along crystal orientations parallel and perpendicular to the three-atom chain. Substantial anisotropy in the stress-strain response of boron carbide is revealed, with loading parallel to the three-atom chain generating a post-yield stress reduction followed by almost perfectly plastic behavior until the onset of fracture. In contrast, loading perpendicular to the three-atom chain generates a post-yield increase in tensile stress that is followed by an abrupt monotonic reduction in stress due to fracture initiation. Distinct differences are also revealed in the alignment of fracture planes to the direction of applied tension, with fracture occurring at ∼90° and ∼45° to the direction of tension when loaded parallel to and perpendicular to the three-atom chain, respectively. Through a systematic analysis of the deformation of all the 41 bonds in a unit cell of boron carbide, these differences in mechanical response are deciphered to arise from the different extents to which specific bonds deform and break upon loading along the two crystal orientations.