Toughening Mechanisms in Stacked Bilayer Graphene Sheets by Means of Sandwiched 1D Nano-rebars

Graphene, with an intrinsic strength of >100 GPa, exhibits promise for armor applications. However, the thermodynamically favorable manufacturing defects severely diminish their achievable strength. To remedy this, 1D nano-rebars, sandwiched between graphene monolayers, were studied. Real-time mode-I crack growth resistance was studied in reinforced graphene under SEM, which revealed that the dissipative interactions between 1D and 2D nanomaterials can increase the ductility of graphene by over 100%, albeit at a slight loss in effective toughness. This significant improvement was analyzed by introducing the concept of geometric conformity to explain the load transfer between them. By means of finite element analysis and shear lag models we explained the contribution of dissipative interactions between nano-rebar and graphene in reducing stress concentration around cracks, leading to high ductility. The dissipative bonds were found to be more favorable over covalent bonds in terms of maintaining a lower interface stress, further delaying interface local failure.