(557f) Mechanical Behavior of Nanocomposite Structures from Interlayer Bonding in Twisted Bilayer Graphene

Graphene-based nanomaterials have exceptional electronic, mechanical, and thermal properties that can be tuned by precise control of their nanostructural features. Such tunable properties are responsible for the unique function of these nanomaterials that has potential to enable numerous technological applications. Toward this end, in this presentation, we report a systematic computational analysis of the mechanical behavior of a class of two-dimensional (2D) carbon-based nanostructures, namely, graphene-diamond nanocomposites formed through interlayer covalent bonding of twisted bilayer graphene with commensurate bilayers. The interlayer bonding is induced by patterned hydrogenation that leads to formation of superlattices of 2D nanodiamond domains embedded between the two graphene layers with the periodicity of the underlying Moiré pattern. The analysis is based on molecular-dynamics (MD) simulations of uniaxial tensile straining tests according to a reliable interatomic bond-order potential. The mechanical response of the nanocomposites is explored systematically as a function of their structural parameters, which include the bilayer’s twist angle, the stacking type of the nanodomains where the interlayer bonds are formed, the interlayer bond pattern and density, and the concentration of sp³-bonded C atoms. We determine the mechanical properties of these 2D materials and identify a range of structural parameters over which their fracture is ductile, mediated by void formation and growth, in contrast to the typical brittle fracture of graphene. 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 and probe the brittle-to-ductile transition. Our study sets the stage for designing few-layer-graphene-based nanocomposites with unique mechanical properties and functionality over a broad range of applications.