The new mechanical model developed by the team is based on the equivalence between the chemical potentials and the mechanical strain energies of the C–C bonds considered as structural beams with bending, axial and shear deformation mechanisms. The approach allows the group to identify not only the equivalent mechanical properties of the C–C bonds, but also their thickness and bond length, as well as providing closed-form solutions for the in-plane mechanical properties of the graphene sheets.

The model shows good agreement with the experimental results available from open literature. Moreover, the model shows that the shear behaviour of the graphene sheets can be explained mechanically when the C–C bonds deform as an auxetic (Negative Poisson's ratio) component. Auxetic structures expand when pulled along one direction, having a counterintuitive deformation behaviour compared with classical structures and materials. The strong auxetic behaviour of the bonds is present for all of the force models considered, and provides an overall shear stiffness for the graphene sheet in good agreement with results from other work performed using molecular dynamics methods.

The researchers presented their work in Nanotechnology.