Fracture mechanics of multi-layer molybdenum disulfide

MSR Elapolu and A Tabarraei and XN Wang and DE Spearot, ENGINEERING FRACTURE MECHANICS, 212, 1-12 (2019).

DOI: 10.1016/j.engfracmech.2019.02.027

Molecular dynamics modeling is used to study the mechanism of brittle fracture in multi-layer two-dimensional molybdenum disulfide (MoS2) with a center crack subjected to mode-I loading. The simulation data is used to verify the application of Griffith, Inglis and quantized fracture mechanics theories for the fracture of monolayer MoS2 sheets. Results show that the Griffith theory cannot accurately predict the fracture strength of cracked MoS2 sheets. Since tip radius is quantized at the nanoscale, Inglis and quantized fracture theory are examined for cracks with different tip radii. Inglis theory is valid for cracks with blunt tips but is not accurate if the crack tip radius is less than 1.15 nm. In comparison to Inglis theory, quantized fracture mechanics gives a better prediction for the fracture strength of MoS2 sheets when the crack tips are very sharp. The simulation results also predict that the structure of the initial crack highly influences the crack advancing path. While at the macroscale, cracks propagate along a straight line perpendicular to loading, at the microscale level cracks in MoS2 kink to grow along a zigzag direction. The toughness and strength of the MoS2 sheets are not significantly affected by an increase in the number of layers from one to three.

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