Interfacial damage of bilayer graphene under shear deformation: Theory, experiment, and simulation

Damage at micro- and nanoscale plays a key role in the failure of a solid, but such behaviors at the interfaces of two-dimensional (2D) materials are still not fully explored. In this work we systematically study the interfacial damage of bilayer graphene (BLG) beyond its interfacial shear strength, covering aspects of theory, experiment, and simulation. We extend the well-established shear-lag model for monolayer graphene on a polymer surface to a graphene/graphene/polymer system, whose numerical results demonstrate that the deformations of two graphene layers are strongly coupled with strain localizations and affected by the edges, and they both remain deformed even after the interface has been damaged. Using Raman spectroscopy and the carbon-isotope substitution technique, the interfacial damage of BLG is monitored experimentally, confirming the non-zero strains in the graphene layers with a damaged interface. Finally, molecular dynamics simulations reveal that with an increased tension, the shear stress concentration near the BLG edge increases the density of interfacial dislocation, initiating the damage and expanding to the central part. This work helps clarify the interfacial damage process in a 2D material system with a cross-scale picture, and we believe that it will provide valuable guidance for the understanding of other basic issues in solid mechanics.