Crack kinking in h-BN monolayer predicted by energy dissipation

Rapid crack propagation in a strip of a hexagonal boron nitride monolayer is studied by molecular dynamics. Crack kinking/branching takes place at high velocities under displacement loadings, accompanied by elastic waves dissipating the external supplied work besides the fresh surface energy. Cracks moving at a maximum velocity (similar to 74% of the Rayleigh wave velocity) do not branch immediately, which is governed by energy dissipation around the crack tip, instead, once the energy release rate (G) reaches a critical value of 19.75J/m(2) (similar to 5.9 times the surface energy density of 3.35J/m(2)), kinking occurs, which shows that G could predict the onset of kinking/branching accurately. The dependences of G for crack initiation and branching on displacement-loading rate, strip size, and initial crack length are examined as well.