Mechanical properties of bilayer graphene sheets coupled by sp3 bonding

The mechanical properties, such as the Young's modulus, the interlayer shear modulus and the ultimate tensile strength, of bilayer graphene sheets (GS) coupled by sp3 bonding are investigated by molecular dynamics simulations. These mechanical properties are found to be sensitive to the presence of sp3 bonds in the bilayer GS. The sp3 bonds exert a strengthening influence on the interlayer shear modulus as well as the load transfer rate, thereby enhancing the stability capacity of GS under axial compression. However, the presence of sp3 bonds also leads to a reduction in the Young's modulus, ultimate tensile strength and the associated facture strain. The adverse and strengthening effects induced by the sp3 bonds are also strongly dependent of their distributions. Simulation results suggest that a small amount of sp3 bonds can be introduced in GS to improve its load transfer rate and stability substantially at the expense of a marginal deterioration in the Young's modulus and tensile strength.