Mechanism of crack propagation in penta-graphene

Penta graphene has attracted much attention due to its unique carbon atom topology and novel properties in these years. In this paper, we study the crack growth and material fracture mechanism of penta graphene under uniaxial tension systematically via molecular dynamics simulation. We explore the mechanism of stress field and influencing factors during crack growth on penta graphene. The mechanical properties of penta graphene and graphene are compared and analyzed. The effect of temperature on the mechanical properties of penta graphene is analyzed by comparing the strain-stress curves at various temperatures. The Young's modulus of penta graphene at fracture time are discussed, and we reveal that the temperature influence on Young's modulus before fracture. By designing initial cracks of different lengths on penta graphene, we investigate into the variation of stress field at both crack tips on penta graphene under stress stretching. The mechanism of crack growth and propagation on penta graphene is uncovered with more details from atomic perspective. It is found that the stress fields are concentrated on various parts on penta graphene with the different crack length. During the growth of short cracks, the stress field mainly concentrates on the crack tip during all the process. In the process of the growth of longer cracks, the stress field will first focus on the section of the crack, and then transfer to the crack tip and begin to grow and propagate around. By analyzing the reduced energy release rate during crack growth and fracture, it is suggested that the lower atomic binding energy weakens the fracture strength of penta graphene, and thus affects the mechanical properties of penta graphene.