2D materials communicate with the environment through large area of surface. Recent experimental measurements have deepened our understanding of the friction between layers of 2D materials and suggested the interlayer properties, such as interlayer friction, can couple with intralayer properties and affect the overall behavior of multilayered 2D material systems. In this study, the effect of interlayer friction on asynchronous crack propogation and dissimilar crack paths is considered by integrating theoretical analysis and numerical simulation. It is found that the intact layer can postpone crack propogation in the neighbouring layer and cracks along dissimilar paths can communicate via interlayer sliding zone, resulting in a size-dependent fracture behavior.
Recent experimental measurements have discovered the fracture toughness of monolayer h-BN is much large than its intrinsic surface energy and based on DFT calculations toughening mechanisms of crack tip bifurcation and edge swapping due to the lattice asymmetry have been proposed. In this study, combining theoretical analysis and phase field (PF) modeling, we study the effect of the polarized edge stress and anisotropic fracture energy on the fracture of h-BN. It is found that polarized edge stress can contribute a mode II stress intensity factor (SIF) travelling with the crack tip and the competition between local lattice asymmetry and gloabl extrenal loading can result in a zigzag crack path with swaping branches.
Fracture has been a grave concern for practical applications of graphene other atomically thin and brittle crystalline materials. In this NSF awarded project, we have been systematically exploring the potential of using topological effects to enhance the fracture toughness of graphene. By designing topological defect distribution and controlling the out-of-plane curvature, we numerically demonstrate that various toughening mechanisms can be activated, including crack tip blunting, crack trapping, ligament bridging, crack deflection, daughter crack initiation and coalescence, pseudo-plastic deformation as well as snap-through among multi-stable states, and toughen graphene and related 2D materials effectively.