Probing Intrinsic Elastic Properties of Multilayer Graphene -- a New Mechanical Constant

TL;DR

This study measures the elastic properties of multilayer graphene using in situ bulge tests and introduces a new mechanical modulus that accounts for interlayer effects, enhancing understanding of its intrinsic elastic behavior.

Contribution

The paper develops a theoretical model and experimental approach to accurately determine the intrinsic elastic constants of multilayer graphene, addressing interlayer strain transfer issues.

Findings

Measured elastic constants vary with layer number.

Proposed a new mechanical modulus combining Grüneisen parameter and Young's modulus.

Identified limitations of traditional elastic constant measurements due to interlayer effects.

Abstract

We present measurements on in-plane Young's modulus and the Gr\"{u}neisen parameter of multilayer graphene with varying number of layers, obtained through {\it in situ} bulge tests. Accurate determination of their elastic parameters poses a significant experimental challenge due to the substantial differences in mechanical behavior between intra- and inter-layers. To address this, we develop a novel theoretical model with first-principles calculations to investigate thickness-dependent incomplete strain transfer between the layers. Our findings show that the experimentally measured elastic constants, which deviate from computed intrinsic values, fail to fully capture ideal mechanical couplings between layers. As a solution, we propose a new mechanical modulus that integrates the Gr\"{u}neisen parameter and in-plane Young's modulus, providing a more reliable representation of their mechanical properties, independent of unavoidable interlayer effects.