Biaxial compression of centimeter scale graphene on strictly 2D substrate

TL;DR

This study investigates the mechanical behavior of centimeter-scale graphene on water, revealing its elastic and plastic properties, the influence of functionalization, and the emergence of viscoelasticity and strain-morphology correlations.

Contribution

It provides the first detailed stress-strain analysis of large-scale graphene on water, showing that natural graphene lacks intrinsic elastic parameters and exploring effects of lattice modifications.

Findings

Young's modulus scales with size and is much lower than microscale graphene.

Crumpling induces viscoelasticity and wrinkle formation.

Strain distribution correlates with graphene morphology.

Abstract

Biaxial compression of centimetre-scale graphene, freely standing on the surface of water is studied. Within this platform, we report full stress-strain compression of graphene identifying elastic and plastic deformations. The Young's modulus follows a scaling law and falls two orders of magnitude below the commonly reported values with microscale graphene samples. Such results strongly confirm that graphene - in its very natural form - lacks any intrinsic elastic parameters. Different functionalization/manipulation of graphene lattice affects the mechanics of graphene differently; particularly the effect of the sp3 hybridization and crystalline voids on the yield strength of graphene is explored. Crumpling of graphene is accompanied by gradual generation and transformation of wrinkles which brings about viscoelasticity in graphene, observed for the first time in this paper. Additionally, we report a peculiar correlation between the morphology and the distribution of the strain in graphene lattice.