In-situ Fracture Toughness Measurement of Multilayer Graphene

Understanding the fracture and failure properties of graphene is a critical step towards integrating graphene into electromechanical devices and flexible electronics. However, the exact fracture properties of graphene are hard to measure due to the atomic level thickness of graphene and its brittle nature which tends to cause it to break before accurate measurements of its properties can be made. In this paper, a method is presented for measuring the fracture properties of graphene with varying number of layers. This method utilizes a custom designed MEMS tensile tester and an effective and repeatable graphene transfer process that enables the transfer of patterned graphene structures onto MEMS devices. The fracture properties of graphene samples with different numbers of graphene layers were tested and the critical strain energy release rate of fracture was measured to be 22 J/m(2), 71.3 J/m(2), and 145 J/m(2) for similar to 7 layer, similar to 12 layer, and similar to 15 layer graphene, respectively. These results show that the fracture toughness of the graphene increases as the number of layers increases. This is likely due to the need for brittle cracks to propagate through multiple, weakly connected layers of the graphene for ultimate failure to occur in the graphene.