Mechanical properties and failure behavior of hexagonal boron nitride sheets with nano-cracks

Cracks in nano-scale are common defects in the 2D materials fabricated by a chemical vapor deposition method. Mechanical performance of 2D materials might be affected significantly due to the presence of nano-cracks. In this work, the mechanical performance and failure behavior of h-BN sheets with nano-cracks were studied using molecular dynamics methods. The relationship between the mechanical properties of h-BN sheets and the type or size of cracks was analyzed. The effect of temperature and strain rate on the mechanical behaviors of h-BN sheets was discussed. Results showed that when the crack size was larger than the threshold value, the Young's modulus of h-BN sheets decreased with the increase of the crack size linearly. The increasing crack size resulted in faster decrease of the Young's modulus of the zig-zag h-BN sheet than that of the armchair h-BN sheet. The fracture strength decreased rapidly with the increasing crack size first. Then, when the crack size reached a critical value, change of the fracture strength become minor. The mechanical properties of h-BN sheets with cracks were sensitive to the variation of temperature and strain rate. The information obtained in this work would be useful for estimating the mechanical performance and failure mechanism of h-BN sheets in future application. (C) 2017 Elsevier B.V. All rights reserved.