title: On the failure load and mechanism of polycrystalline graphene by nanoindentation.
abstract: Nanoindentation has been recently used to measure the mechanical properties of polycrystalline graphene. However, the measured failure loads are found to be scattered widely and vary from lab to lab. We perform molecular dynamics simulations of nanoindentation on polycrystalline graphene at different sites including grain center, grain boundary (GB), GB triple junction, and holes. Depending on the relative position between the indenter tip and defects, significant scattering in failure load is observed. This scattering is found to arise from a combination of the non-uniform stress state, varied and weakened strengths of different defects, and the relative location between the indenter tip and the defects in polycrystalline graphene. Consequently, the failure behavior of polycrystalline graphene by nanoindentation is critically dependent on the indentation site, and is thus distinct from uniaxial tensile loading. Our work highlights the importance of the interaction between the indentation tip and defects, and the need to explicitly consider the defect characteristics at and near the indentation site in polycrystalline graphene during nanoindentation.
authors.affiliation: International Center for Applied Mechanics, State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi'an Jiaotong University, Xi'an 710049, China.
authors.forename: Z D
authors.initials: ZD
authors.lastname: Sha
authors.affiliation: Institute of System engineering, China Academy of Engineering Physics, SiChuan, MianYang 621900, China.
authors.forename: Q
authors.initials: Q
authors.lastname: Wan
authors.affiliation: Institute of High Performance Computing, A*Star, 138632, Singapore.
authors.forename: Q X
authors.initials: QX
authors.lastname: Pei
authors.affiliation: Institute of High Performance Computing, A*Star, 138632, Singapore.
authors.forename: S S
authors.initials: SS
authors.lastname: Quek
authors.affiliation: International Center for Applied Mechanics, State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi'an Jiaotong University, Xi'an 710049, China.
authors.forename: Z S
authors.initials: ZS
authors.lastname: Liu
authors.affiliation: Institute of High Performance Computing, A*Star, 138632, Singapore.
authors.forename: Y W
authors.initials: YW
authors.lastname: Zhang
authors.affiliation: 1] Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA [2] Department ofMechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: V B
authors.initials: VB
authors.lastname: Shenoy