Showing papers by "Xiaoding Wei published in 2016"
TL;DR: This study demonstrates that the finite shear strength between individual layers could explain the experimentally measured size-dependent strength with thickness scaling in MLG sheets and reveals an atomic level interlayer slippage process.
Abstract: Understanding the deformation mechanisms in multilayer graphene (MLG), an attractive material used in nanodevices as well as in the reinforcement of nanocomposites, is critical yet challenging due to difficulties in experimental characterization and the spatiotemporal limitations of atomistic modeling. In this study, we combine nanomechanical experiments with coarse-grained molecular dynamics (CG-MD) simulations to elucidate the mechanisms of deformation and failure of MLG sheets. Elastic properties of graphene sheets with one to three layers are measured using film deflection tests. A nonlinear behavior in the force vs deflection curves for MLGs is observed in both experiments and simulations: during loading/unloading cycles, MLGs dissipate energy through a “recoverable slippage” mechanism. The CG-MD simulations further reveal an atomic level interlayer slippage process and suggest that the dissipated energy scales with film perimeter. Moreover, our study demonstrates that the finite shear strength betwe...
105 citations
TL;DR: It is revealed that the deformation and failure of graphene oxide are strongly dependent on the relative concentrations of epoxide (-O-) and hydroxyl (-OH) functional groups, and should be treated as a versatile, tunable material that may be engineered by controlling chemical composition.
Abstract: The mechanical properties of graphene oxide (GO) are of great importance for applications in materials engineering. Previous mechanochemical studies of GO typically focused on the influence of the degree of oxidation on the mechanical behavior. In this study, using density functional-based tight binding simulations, validated using density functional theory simulations, we reveal that the deformation and failure of GO are strongly dependent on the relative concentrations of epoxide (−O−) and hydroxyl (−OH) functional groups. Hydroxyl groups cause GO to behave as a brittle material; by contrast, epoxide groups enhance material ductility through a mechanically driven epoxide-to-ether functional group transformation. Moreover, with increasing epoxide group concentration, the strain to failure and toughness of GO significantly increases without sacrificing material strength and stiffness. These findings demonstrate that GO should be treated as a versatile, tunable material that may be engineered by controllin...
67 citations