Investigation On The Mechanical Properties And Regulation Mechanism Of Graphene Kirigami

Graphene is a new type of two-dimensional carbon material with a single atomic layer thickness.Since its discovery in 2004,it has been received extensive attention from scientific researchers.Graphene has excellent mechanical,thermal,magnetic and electrical properties and it is treated as a new generation of strategic materials.It has broad application prospects in high-performance nanoelectronic devices,composite materials,energy storage,gas sensors,field emission materials and other fields.Recent years,traditional kirigami/origami technology has been introduced into the field of nanotechnology.Experiments and numerical simulations show that as a simple,effective and controllable method,kirigami technology can greatly improve the ductility of graphene,and specific kirigami patterns may also cause graphene to exhibit negative Poisson's ratio effect,which may provide a new solution for effectively regulating the properties of graphene and other two-dimensional nanomaterials and expanding its application fields.In this work,two types of graphene kirigami models were constructed by introducing rectangular and rhomboidal void patterns.The mechanical properties and deformation failure mechanism of graphene kirigami under uniaxial tensile and shear loadings were investigated using molecular dynamics simulations.The effects of perforation size parameters such as aspect ratio and parameter S on the mechanical properties of graphene kirigami were studied emphatically and the regulation mechanism was also analyzed.The main research work can be listed as follows:(1)The tensile mechanical properties of rectangular and rhomboidal perforated graphene kirigami and the influence of perforation size parameters were studied.The results show that rectangular and rhomboidal perforations greatly reduce the ultimate stress and Young's modulus of graphene.By adjusting the aspect ratio and parameter S,the mechanical properties of graphene kirigami can be effectively regulated.When the parameter S is small(S<6),the rectangular perforated graphene kirigami will undergo out-of-plane deformation during the tensile process,and the fracture strain is improved up to twice that of pristine graphene.When the parameter S is large(S?6),the graphene kirigami structure will not deform out of plane.The fracture strain of rhomboidal perforated graphene kirigami is less than that of pristine graphene.When the aspect ratio of the perforation is 2.5 and S is less than 8,the Poisson's ratio of the rectangular perforated graphene kirigami become negative.When the aspect ratio of the perforation is 2.5 and S is less than 6,the Poisson's ratio of the rhomboidal perforated graphene kirigami become negative.In addition,the hydrogenation of the cut edge also affects the mechanical properties of graphene kirigami.The results show that hydrogenation will enhance the tensile ultimate stress and Young's modulus of rhomboida perforated graphene kirigami,while it has little effect on the ultimate stress and Young's modulus of rectangular perforated graphene kirigami.(2)The mechanical properties of rectangular and rhomboidal perforated graphene kirigami and the influence of perforation size parameters were studied under shear deformation.It is found that the rectangular and rhomboidal perforations on graphene kirigami significantly reduce the shear ultimate stress and shear modulus of graphene.By adjusting the aspect ratio and parameter S,the mechanical properties of graphene kirigami under shear deformation can be effectively regulated.When the parameter S is small(S<5),the shear fracture strain of rectangular perforated graphene is greater than that of pristine graphene.Increasing the aspect ratio of perforation can increase the shear fracture strain of rectangular perforated graphene kirigami.The aspect ratio has a significant effect on the shear ultimate stress of rhomboidal perforated graphene kirigami.When the aspect ratio of perforation decreases,the shear ultimate stress of the rhomboidal perforated graphene kirigami increases significantly.