(666d) Formation and Thermomechanical Behavior of Nanocomposite Superstructures from Interlayer Bonding in Twisted Bilayer Graphene
We also report results of a systematic study of the mechanical behavior of such carbon nanocomposite superstructures based on molecular-dynamics (MD) simulations of uniaxial straining tests according to a reliable interatomic bond-order potential. The mechanical properties of these 2D materials are investigated over the full range of structural parameters. We introduce a ductility metric, demonstrate its direct dependence on the concentration of sp3-bonded C atoms, and show that increasing the concentration of sp3-bonded C atoms beyond a critical level induces ductile mechanical response. We analyze the ductile fracture mechanisms, mediated by void formation, growth, and coalescence, in contrast to the typical brittle fracture of graphene and probe the brittle-to-ductile transition. In addition, we report results of MD simulations of nanoindentation tests that we have performed on these superstructures, including mechanical properties of these 2D materials, such as elastic modulus, strength, and toughness, and demonstrate their direct dependence on the superstructuresâ structural parameters as well as indentation parameters. The underlying fracture mechanism of such superstructures under nanoindentation testing also is characterized in detail. Finally, we report results of non-equilibrium MD simulations of thermal transport in these superstructures, aimed at determining the dependence of the lattice thermal conductivity of the superstructures on the key structural parameters, such as the concentration of covalent interlayer C bonds. Our study sets the stage for designing few-layer-graphene-based nanocomposites with unique thermomechanical properties and functionality over a broad range of applications.