Analysis Of Mechanical Properties Of Nano Network From Few-Layered Graphene Connected With Benzene

Ductility characterizes the plastic deformation ability of a material under tensile load,and is one of the most important mechanical properties of a material.Graphene is one of the most concerned carbon nanomaterials in recent years,and its mechanical properties have received extensive attention.Existing studies have shown that the ultimate breaking strains of single-layer graphene materials stretched along the armchair and zigzag chiral directions at room temperature are 21% and 14%,respectively.Once the strain exceeds the fracture strain,graphene will quickly fail in a brittle fracture mode.Graphene's lower fracture strain,poor ductility and severe brittle failure mode greatly limit its application.In order to improve the poor ductility of graphene materials,this paper proposes a new type of carbon nano network structure composed of benzene-graphene based on multilayer graphene materials and benzene molecules.On this basis,molecular dynamics methods are used to study the constitutive relationship and microscopic fracture behavior of the new material under uniaxial tensile load,and the key factors such as the material's geometric size,environmental temperature,and strain rate are analyzed.Specific influence on mechanical properties.The main conclusions of this article are as follows:(1)Firstly,molecular dynamics simulation methods were used to study the effects of environmental temperature,stretching rate and number of sandwich layers on the uniaxial tensile mechanical properties of the new carbon nano network structure.The results show that the load-bearing behavior of the nano-network structure during the stretching process is divided into three stages.In the first stage,only the surface layer graphene bears the tensile force,which is manifested as a slow increase in the stress in the stress-strain curve;in the second stage,all the graphene sheets in the model participate in the load.When the strain increases to the first critical strain,the surface layer graphene will undergo brittle fracture and cause the stress in the stress-strain curve to drop suddenly;in the third stage,only the sandwich layer graphene is loaded,and the strain increases to the second critical strain When the value is reached,the stress suddenly decreases again.That is,the surface layer is broken at the first critical strain,and the core layer is broken at the second critical strain.The characteristic that the carbon nano network contains two critical strains under uniaxial tensile load is caused by the difference in length between the surface layer graphene and the sandwich layer graphene sheet.The critical strain of carbon nano network structure always decreases with increasing temperature.When the temperature is constant,the second critical strain of the new material is greater than the fracture strain of single-layer graphene,thus improving its ductility.In addition,the number of core layers and the stretching rate will also affect the critical strain to a certain extent.(2)On the basis of the above research,the influence of the number of periodic cells on the uniaxial tensile mechanical properties of the nano-network structure is considered.The results show that the number of cells contained in the nano-network structure has a significant impact on the second critical strain of the structure.This is mainly due to the greater the number of cycles,the greater the number of atoms,resulting in longer stretching time.The maximum critical strain for the fracture of the sandwich layer depends on the length difference between the surface layer and the sandwich layer,indicating that the ductility of the new nano-network structure is adjustable.In addition,the uniaxial tensile mechanical properties of the nano-network structure in which the benzene ring is removed and the graphene directly connected are also studied.It is found that when the benzene ring is not connected in the model,the surface layer and the sandwich layer have more similar critical strains,that is,the first The critical strain is 24.9%,and the second critical strain is 25.8%.This is similar to the original graphene and cannot improve the ductility of the nano network structure.The new carbon nano network structure proposed in this study has high and adjustable ductility,which can provide a reference for the design of new carbon nano materials under large displacement loads.