(529h) Mechanical Behavior of Graphene Nanomeshes

Graphene-based nanomaterials have exceptional electronic, mechanical, and thermal properties that can be tuned by tailoring their nanostructural features. Graphene nanomeshes (GNMs) are ordered, defect-engineered graphene nanostructures consisting of periodic arrays of nanopores in the graphene lattice with neck widths less than 10 nm. The electronic, transport, and mechanical properties of GNMs can be tuned by varying the structural, chemical, and architectural parameters of the nanomeshes, such as their porosity, pore lattice structure, pore morphology, as well as the type and extent of their pore edge termination.

Here, we report the results of a comprehensive study of the mechanical response of GNMs to uniaxial tensile straining and determine their mechanical properties based on molecular-dynamics (MD) simulations of dynamic deformation tests according to a reliable bond-order interatomic potential. We establish the dependences of the GNMs’ ultimate tensile strength, fracture strain, and fracture toughness on the nanomesh porosity and derive scaling laws for the strength-density relation of the GNMs. We place special emphasis on how the above properties are affected by the GNMs’ pore morphology and pore edge termination with H atoms. The underlying mechanisms of crack initiation and propagation, and of nanomesh failure are characterized in detail.

We also study the mechanical and structural response of GNMs to nanoindentation based on MD simulations of nanoindentation tests. We demonstrate that the elastic modulus and the hardness of the GNMs decrease monotonically with increasing nanomesh porosity and derive modulus-density and hardness-density scaling laws. We also examine the effects on the hardness and stiffness of the GNMs of the termination of the GNMs’ pore edges by hydrogenation. The underlying mechanisms of nanomesh structural response upon nanoindentation also are characterized in detail over the full range of the GNMs’ structural parameters examined.