Abstract

Buckling and fracture are two crucial failure modes of h-BN sheet and establishing the criterion for the failure modes is the prerequisite to guarantee the proper applications of h-BN sheet in practice. For the failure of h-BN sheet, previous studies mainly focused on the freestanding h-BN sheet under uniaxial or equi-biaxial loadings. However, for the more general case in practice, the critical failure of substrate-supported h-BN sheet under complicated loadings remains to be studied. In this paper, the substrate-supported h-BN sheet under complicated loadings is considered to reveal the failure mechanism and to establish the criteria for both the buckling and fracture. In order to predict the critical failure stresses efficiently and accurately for complicated loadings, a modified mode-independent energy-based analysis method (mMIEM) is proposed. Then, by analyzing the stress state and observing the failure features, the rational criteria for the buckling and fracture are established and the space of the allowable stress for the SiO2 substrate supported h- BN sheet is provided. The results indicate that the buckling of h-BN sheet is dominated by the second principal stress, namely the maximum compressive stress, while the fracture depends on the stresses along and vertical to the armchair direction rather than the principal stresses. Moreover, the substrate has a significant effect on the critical buckling of the h-BN sheet but has little effect on the critical fracture. The failure criterion and allowable stress space can be used in the design and evaluation of the h-BN based electronic devices.

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