Nonlinear fracture of two-dimensional transition metal carbides (MXenes)

As a newly discovered two-dimensional (2D) material group, MXene has exceptional thermal-electronic properties. However, its mechanical behavior, especially fracture, remains unexplored. In-situ SEM tensile experiments show that the fracture of MXene is quite nonlinear with a much-prolonged softening stage in comparison with other 2D materials, which is suspected to be caused by the anisotropy and relatively thick monolayer of MXenes. In this work, molecular dynamic (MD) modeling is conducted to investigate the anisotropic fracture behavior of two types of MXenes (Ti2C and Ti3C2) with different monolayer thickness. Both pristine and defected MXenes are investigated. Results show that: (1) MXene tends to fracture along zigzag direction, (2) atomic vacancies at the crack tip have limited effects on the overall fracture behavior, (3) a thicker monolayer can produce a larger cohesive zone due to the 'thinning' process, (4) complex fracture paths are to be expected for mixed-mode fractures.