A first principles investigation into the mechanical properties and the strengthening mechanism of the graphene/aluminum interface structure

As a reinforcing phase, Graphene (Gr) can effectively enhance the strength of the aluminum substrate (Al). Yet most of the previous research focuses primarily on the interfacial adhesion, the mechanical performances of the graphene/aluminum interface structure and the corresponding strengthening mechanism remain insufficiently understood. In this study, employing density functional theory (DFT), the electronic and mechanical properties of different graphene/aluminum interface structures (Gr/Al) are investigated. By tensile simulations of the Gr/Al interface structures, the enhancement mechanism of Gr on aluminum substrate is revealed at a microscopic scale. The ideal strength of the Gr/Al interface structure increases with the increasing number of graphene layers, where the three-layer graphene structure (AAA-Gr/Al) exhibits the highest ideal strength of 5.02 N/m. For the tensile of the Gr/Al interface structure, the distortion of the graphene lattice enhances the interfacial binding ability and resists tensile deformation. Eventually, the breaking of the C-C bonds in graphene occurs, preventing the reformation of in-plane strong σ covalent bonds. For the AAA-Gr/Al interface structure under biaxial tension, the resistance to deformation primarily arises from the p_z orbital of graphene and the p_x orbital of graphene hybridizes with the s orbital of Al, which synergistically increase the ideal strength of the interface structure. A comprehensive framework on evaluating the mechanical performance of Gr/Al interface structures has been developed by combining adhesion energy analysis, stress-strain calculations, and electronic structure analysis, which will advance the understanding of the structure-property relationship in Gr/Al composites.