  We examine the fracture mechanics of tearing graphene. We present a molecular
dynamics simulation of the propagation of cracks in clamped, free-standing
graphene as a function of the out-of-plane force. The geometry is motivated by
experimental configurations that expose graphene sheets to out-of-plane forces,
such as back-gate voltage. We establish the geometry and basic energetics of
failure, and obtain approximate analytical expressions for critical crack
lengths and forces. We also propose a method to obtain graphene's toughness. We
observe that the cracks' path and the edge structure produced are dependent on
the initial crack length. This work may help avoid the tearing of graphene
sheets and aid the production of samples with specific edge structures.
