Experiments on free standing graphene can expose the graphene sheets to out-of-plane forces. An example of that is the back-gate voltage experimental setup. Here we show that out-of-plane forces can cause free standing graphene to fracture. This fracture mode is known as the tearing mode and is common in materials like paper. We present a numerical study of the propagation of cracks in clamped, free standing graphene as a function of the out-of-plane force. The simulation uses molecular dynamics and the MEAM semi-empirical potential, shown to reproduce well the properties of graphene and to support crack propagation. The simulations show that depending on the initial condition a crack will not run straight through the sheet, as initially expected. Another interesting result is that, depending on the initial crack orientation (zigzag or armchair), the propagation pattern will be different. The edge orientation of a graphene sheet determines its electronic properties, therefore it will be most useful to be able to predict the edge orientation of produced samples. Most importantly, from the simulations and an analytical calculation, we are able to obtain a threshold for the graphene fracture energy. This result should help avoid fracture of graphene samples in the lab.
Journal: TechConnect Briefs
Volume: 1, Nanotechnology 2011: Advanced Materials, CNTs, Particles, Films and Composites
Published: June 13, 2011
Pages: 200 - 202
Industry sector: Advanced Materials & Manufacturing
Topics: Carbon Nano Structures & Devices