Effects of tensile strain rate and grain size on the mechanical properties of nanocrystalline T-carbon

T-carbon is a new carbon allotrope forecasted by first-principle calculations and fabricated experimentally through the irradiation of a multi-walled carbon nanotube. In this study, the mechanical properties and failure mechanisms of nanocrystalline T-carbon under tensile testing are investigated using molecular dynamics simulations. The results show that the mechanical properties are significantly affected by the strain rate and grain size. A higher strain rate results in greater failure stress, failure strain and Young's modulus, i.e., the strain rate has a similar influence on these mechanical properties. In contrast, the failure strain of nanocrystalline T-carbon decreases with an increasing grain size, but the failure stress and Young's modulus do not monotonously change when grain size varies. Moreover, during the tensile process, it is found that the crack always initiates at the grain boundaries, especially at junctions of multiple single crystal grains, and then propagates along grain boundaries. Besides, for different strain rates and grain sizes, the nanocrystalline T-carbon shows various deformation and fracture patterns, which finally induces the distinct mechanical properties of nanocrystalline T-carbon.