Graphene Origami-Enabled Auxetic Metallic Metamaterials: An Atomistic Insight

Auxetic metamaterials with programable negative Poisson's ratio (NPR) are of great significance in engineering applications. These materials, however, are either mechanically weak or heavily reliant on their specially designed architecture/topology to be auxetic. Consequently, their auxetic performance may be deteriorated or even lost due to local structural deformation or failure under excessive external loading. Developing materials simultaneously possessing auxetic characteristics and excellent mechanical properties still remains a great challenge. Herein, we report a class of graphene origami (GOri)-enabled metallic metamaterials with a highly tunable NPR as well as improved mechanical properties using molecular dynamics study. Simulation results reveal that embedding more GOri into Cu matrix can not only lead to a bigger NPR but also an increased elastic modulus of the nanocomposite. The NPR of the nanocomposite with 3.35 wt % Miura-patterned GOri can reach –0.2796 at room temperature. The application of pressure and temperature can further enhance the auxetic behavior of the nanocomposite. It is also found that GOri/Cu nanocomposite significantly outperforms its counterpart reinforced with pristine graphene in terms of NPR.