On the strain-rate dependence of dynamic tensile strength in single and nanocrystallie SiC*

The strain-rate dependence of dynamic tensile strength in single and nanocrystalline SiC is investigated via large scale molecular dynamic simulations. A quasi-isentropic loading method is used to evaluate the strain rate to over six-order from 10⁷ to 10¹² s^-1. SiC with [001] orientation exhibits a perfectly reversible deformation twinning mechanism that enables a high tensile strength, while [110] and [111] crystals contain irreversible defects after unloading that results in a significant decrease in strength. Octahedral cleavage along {111} family planes is found to occur only in [001] SiC within 10⁹ s^-1 of the strain rate due to its covalent bond. A power model can be fit basing on the tensile strengths at extremely high strain rate regime which yields a good prediction of strengths at plate-impact experimental strain rates.