Tensile And Compressive Properties Of Graphene/Crabon Nanotubes With Crack

Carbon nanotubes and graphene are important members of new carbon nanomaterials，Studies have shown that perfect carbon nanotubes have outstanding mechancial, electrical,thermal and chemical properties. However, structural defects are unavoidably introduced incarbon nanotubes and graphene in the present production conditions, which affects themechanical properties of carbon nanotubes and graphene in a large part, so the effects ofdefects on carbon matertials have become a significant topic in the fields of nanomechancis.The tensile and compressive properties of carbon nanotubes and graphene with variousdefects remain to be further research. This paper focuses on the single walled carbonnanotubes and graphene with different cracks, and the effects of crack length, dip angle,temperature and strain rate on the tensile and compressive properties are investigated based onthe molecular dynamics simulations.Based on the Tersoff potential, the fracture of single-walled graphene with edge, centralhorizontal and oblique cracks are studied respectively, and the crack speed and crack initiationstress are calculated. The effects of temperature, strain rate and crack length on the tensileproperties of graphene are analysed. The results show that the crack speed and crack initiationstress are smaller for graphene with larger crack length. The fracture strength and fracturestrain decrease with the increase in crack length and temperature, and with the decrease ofstrain rate. Crack propagates from the region around the initial crack, and different cracksresult in different crack propagation paths.The fracture of single walled carbon nanotubes with different cracks are investigated,and the effects of crack length, temperature, strain rate, tube diameter and dip angle areconsidered in the molecular dynamics simulations. The deformation mechanism of carbonnanotubes in different conditions is analysed. The results show that crack grows from the areawhere near the initial broken bonds and propagates circumferentially along with the initialcarck direction. The tensile properties of carbon nanotubes are weakened with the increase ofcrack length and temperature. The variations of strain rate, tube diameter and dip angle alsoaffect the crack propagation paths.The axially compressed buckling of single walled carbon nanotubes with cracks are studied via molecular dynamics simulations. The variations of crack length and tube lengthare mainly considered. The results show that the critical buckling strength decreases with theincrease of crack length and tube length. For carbon nanotubes with the dip angle900, there ishollow and dislocation in the region of the initial crack. For carbon nanotubes with the dipangle300, there is hollow around the initial crack and twist in the edge of crack.