Investigation on fracture of pre-cracked single-layer graphene sheets

Peridynamics (PD) is employed to model the fracture of pre-cracked graphene sheets under mode-I loading condition to show its application at nanoscale. Then the related mechanisms at atomic scale are revealed by using molecular dynamics (MD) simulation, with which the mechanical properties and fracture mechanisms of full atomistic pre-cracked single-layer graphene sheets (SLGSs) with different types of crack tip micro-structures are investigated. The results such as the fracture forms obtained from the PD and MD simulations show good consistency. The MD results show that different crack tip structures have distinct effect on the mechanical properties of graphene sheets. The pre-cracked SLGSs with ω-type crack tip show higher fracture strength and strain than the ones with u-type crack tip. For the pre-cracked SLGSs with u-type crack tip, the fracture strength and strain of the armchair sheet are higher than the zigzag one. However, there are almost no differences for the armchair and zigzag sheets with ω-type crack tip. Due to the difference between armchair and zigzag structures, carbon polygon ring can form in armchair sheets and its formation is related to the crack tip structures and the crack width. In addition, the crack propagation can be characterized by the local stress state, which for crack initiation is different from steady crack propagation.