Investigation of crack propagation and existing notch on the mechanical response of polycrystalline hexagonal boron-nitride nanosheets

In this paper, we investigate the effect of temperature and grain size on the mechanical response of atomistic polycrystalline structures through classical molecular dynamic (MD) simulations. Five samples with different grain sizes in the range of 2–20 nm are examined under different temperatures. In addition, the effect of the crack size on the crack speed and orientation is studied for samples with an initial edge crack of different crack lengths. We also determine the effect of the initial crack lengths on the tensile strength. Our results show a drop in the tensile strength and elastic modulus with decreasing grain size while the failure strain is increasing. The failure pattern shows an opposite trend in the sample with a grain size higher than 14 nm. An existing initial center crack reduces the tensile strength and failure strain as well, and this reduction is independent of the initial crack length. The impact of the initial notch on the mechanical properties depends furthermore on the location of the notch in the samples.