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A predictive localized damage and failure theory for 2d nanomaterials
Multilayered, staggered assemblies of 2D nanomaterials such as graphene and metal chalcogenides are finding applications in a broad range of areas from nanocomposites to energy storage devices. Whereas a large number of studies have focused on elasticity and fracture mechanisms of a single isolated sheet, the mechanical behavior of multilayered assemblies remains poorly understood due to scale limitations of molecular simulations. Here, we present an atomistically informed coarse-grained modeling technique based on a strain energy conservation approach that is particularly suited for describing the mechanical behavior of multilayer graphene in the elastic and fracture regimes (Ruiz, Xia, Meng, Keten, Carbon, 2014). The hexagonal symmetry of graphene’s honeycomb lattice is conserved, and therefore the anisotropy in the non-linear large deformation regime between the zigzag and armchair directions is preserved. The superlubricity effect, namely the strong orientational dependence of the shear rigidity between graphene layers, is also captured. We validate the model using by reproducing recent experimental nanoindentation results in silico. Tensile deformation studies illustrate that the elasticity and strength can be well described by an extended shear lag model, but the plastic response governing toughness is dependent on various factors, most notably size-effects. Based on simulation observations, we propose a physics-based analytical model to describe localization and failure mechanisms in staggered assemblies and dependence of the constitutive behavior on the evolution of damage. Our multi-scale approach is broadly applicable to 2D materials and paves the way for studying more sophisticated systems such as polymer nanocomposites synthesized by layer-by-layer (LbL) assembly.Author(s):
Sinan Keten
Northwestern University
Luis Ruiz
Northwestern University
Zhaoxu Meng
Northwestern University
Wenjie Xia
Northwestern University