Effect of interlayer sliding on the estimation of elastic modulus of multilayer graphene in nanoindentation simulation

¹ Research Reactor Utilization Department, Korea Atomic Energy Research Institute - 989-111 Daedeok-daero, Yuseong-gu, Daejeon 34057, Republic of Korea
² Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST) 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
³ Division of Mechanical Engineering, College of Engineering, Korea Maritime and Ocean University 727 Taejong-ro, Yeongdo-gu, Busan 49112, Republic of Korea

^(a) dsohn@kmou.ac.kr (corresponding author)

Received: 9 June 2016
Accepted: 30 June 2016

Abstract

Nanoindentation experiments and simulations are carried out to estimate the elastic modulus of freely-suspended-multilayer graphene. However, due to the difficulty of clamping all layers of multilayer graphene in experiments, and to the ambiguity of imposing the clamped boundary conditions in numerical simulations, the estimated values of elastic modulus exhibit large variation. In particular, interlayer sliding can affect the estimation of elastic modulus. From a series of molecular dynamics simulations, we demonstrate that the estimated elastic modulus of multilayer graphene depends on the level of interlayer sliding involved in boundary conditions. Under fully clamped boundary conditions that prevent interlayer sliding, the elastic modulus is constant regardless of the number of layers. In contrast, under weakly clamped boundary conditions that involve interlayer sliding, the elastic modulus decreases with increasing number of layers. In the case of weakly clamped conditions, a few wrinkles form in the interlayer and then coalesce into a single large wrinkle due to interlayer sliding. Our findings provide an understanding of the variation of elastic modulus observed in other experimental and numerical studies.