Flaw insensitive fracture in nanocrystalline graphene

摘要

We conducted the large-scale atomistic simulations to investigate the fracture behaviors ofnanocrystalline graphene nanostrips with flaws,such as holes or notches.The simulations showthat microcracks nucleate randomly at intrinsic defects along grain boundaries and coalesce toform a big crack,eventually leading to catastrophic fracture.The key finding is that the microcracknucleation and coalescence are not always induced by nor associated with the large holeor notch in the simulated system.The simulation results are in good agreement with theoreticalprediction based on the fracture mechanics.This study also showed the entropic elastic behaviorsof graphene in the initial state of deformation and estimated the facture surface energy of about 8J/m2 for nanocrystalline grapheme,which is lower than that (about 10 J/m2) of single crystallinegraphene.These differences can be attributed to the presence of defects along grain boundariesin nanocrystalline graphene.