Low-cycle fatigue failure of MoS2 monolayer

Two-dimensional (2D) materials, such as graphene, MoS2, et al., are promising for a wide range of applications, such as in nanoelectronics, sensors, resonators, oscillators, nanocomposites, et al. These applications, often under cyclic loading, demand robustness and durability. In this work, we perform molecular dynamics simulations to study the low-cycle fatigue life and failure mechanism of MoS2 containing a crack focusing on four influencing factors: Strain range, strain ratio, initial crack size, and temperature. We find that an increase in any of these four factors decreases the fatigue life of MoS2. We further reveal the detailed fatigue failure process and discover that bond rupture and remaking at the crack tips with irreversible lattice reconfiguration are necessary for crack propagation during the cycle loading, and after even fatigue failure, the cycles of bond rupture and remaking processes at the fractured edges can continue. We also examine the relations between the calculated fatigue life and the four influencing factors and find that they follow the well-known fatigue laws, suggesting their universal nature. These findings not only provide novel insights into the fatigue behaviour of MoS2, but also are important for the engineering applications of 2D materials.