Numerical Investigation of the Fracture Properties of Pre-Cracked Monocrystalline/Polycrystalline Graphene Sheets

Abstract

The fracture properties of pre-cracked monocrystalline/polycrystalline graphene were investigated via a finite element method based on molecular structure mechanics, and the mode I critical stress intensity factor (SIF) was calculated by the Griffith criterion in classical fracture mechanics. For monocrystalline graphene, the size effects of mode I fracture toughness and the influence of crack width on the mode I fracture toughness were investigated. Moreover, it was found that the ratio of crack length to graphene width has a significant influence on the mode I fracture toughness. For polycrystalline graphene, the strain energy per unit area at different positions was calculated, and the initial fracture site (near grain boundary) was deduced from the variation tendency of the strain energy per unit area. In addition, the effects of misorientation angle of the grain boundary (GB) and the distance between the crack tip and GB on mode I fracture toughness were also analyzed. It was found that the mode I fracture toughness increases with increasing misorientation angle. As the distance between the crack tip and GB increases, the mode I fracture toughness first decreases and then tends to stabilize.

On the mechanical characteristics of graphene nanosheets: a fully nonlinear modified Morse model

“…It should be noted that, in contrast to structural elements such as beams and frames, the connector elements do not require section properties. As an example, when beam elements are used to model C-C bond stretching in MSM methods, various circular [32] and rectangular [47] sections are suggested in the literature, while there is no general consensus on their selection. First, a detailed 'inp' file is written, which contains nodes, elements and their connections, then a Python code is developed to import this input file into Abaqus.…”

Toughening Two Dimensional Materials Through Lattice Disorder

“…To increase the fracture toughness of brittle materials as strong as graphene while retaining its 2D nature, there are not many methods at our disposal. Theoretically, several promising approaches, including designing graphene structures with controlled distributions of topological defects [7][8][9] , modifying the grain size 10,11 and misorientation angle of grain boundary [12][13][14] , have been found to improve the fracture resistance of graphene. Turning those ideas into reality, however, has met signi cant challenges: atomic structures of 2D materials are di cult to be manipulated through mechanical exfoliation 15,16 , chemical vapor deposition (CVD) [17][18][19][20][21] , or other well-known technologies 22,23 .…”

The Crack Angle of 60° Is the Most Vulnerable Crack Front in Graphene According to MD Simulations

“…Thus, it is believed to be one of the strongest materials [17,18]. Its mechanical properties have been extensively investigated [19][20][21][22][23][24][25][26] along with those of hydrogenated graphene and other derivatives [27][28][29][30][31]. Furthermore, studies have shown that the fracture toughness (a measure of a material's ability to resist fracture) of defective graphene is very low, classifying it as a brittle material that is hence susceptible to breaking [12].…”

“…Hence, regular efforts are made to establish effective methods through which graphene toughness can be improved. A number of studies on the effect of the defect geometry, including cracks, on the mechanical properties of graphene, such as its fracture toughness, have been reported [25,[32][33][34]. Crack tips, in general, are wedge-shaped.…”