Structure-property relation of nanoporous graphene membranes

To reveal the structure-property relation of nanoporous graphene (NPG) membranes, molecular dynamics simulations are performed to study the mechanical properties of materials in uniaxial and biaxial tension, emphasizing the effects of neck width, relative density, pore size and shape. The structural evolution, crack initiation and propagation, brittle failure, Young's modulus, strength, toughness, fracture strain are addressed. For all tensile cases, the crack initiates on the pore edge with high stress and preferably propagates along the zigzag directions of graphene. The NPG in biaxial tension shows higher modulus than those in uniaxial tension. Relative density tends to be the dominant characteristic parameter to determine the mechanical properties. With constrained geometries, "smaller is stronger", and "smaller is tougher" are observed in the size effect of neck width. Pore shape affects the stress distribution and concentration, leading to varied mechanical responses. Particularly, the stress concentration in the tensile direction significantly reduces the mechanical performances. The scaling laws for the mechanical properties as functions of relative density and neck width are developed and presented for predicting the mechanical properties of NPG. The investigation further highlights the mechanical behaviors and potentially accelerates the promising applications of NPG membranes. (C) 2020 Elsevier Ltd. All rights reserved.