Based On The Molecular Dynamics Method Study The Buckling Behavior Of Defect Of Carbon Nanotubes

Carbon nanotube has attracted tremendous scientific and industrial interests due to its exceptional mechanical, electrical and thermal properties. In this paper, classic molecular dynamic simulations are carried out to investigate the buckling behaviors of imperfect carbon nanotube under axial comprssion.Systematically study the buckling behaviors and mechanical properties of single-walled carbon nanotubes under axial compression, both for perfect and imperfect ones introducing atomic vacancies. The effect of chirality, diameter, quantity and position of vacancy are systematically studied. The simulation results reveal that their mechanical properties such as Young’s modulus, critical strain and stress suffering a significant decline as the increasing numbers of vacancies. It is also found that the critical stress and strain are sensitive to position of atomic vacancy. Carbon nanotubes with vacancies located at the center have lower critical strain and are easier to reach the failure stage than those with vacancies at both sides.The buckling behaviors of pristine and defective DWNTs under uniaxial compressive loads are studied by means of MD simulation, with an emphasis on the load transfer mechanisms of the Frenkel pair crosslinks between adjacent walls. Results show that inter-tube crosslinks reduce the buckling stress of nanotube dramatically while only modestly reduce the Young’s modulus. Although introducing of crosslinks sacrifices part of the sustainable strength of the material, it avoids the sharp drop of the stress when buckling and is more stable in the post-buckling stage. The findings in the above investigation give us useful implications in utilizing CNTs based nanocomposites, particularly for materials to resist high speed impact such as ballistic armor.Further simulations are performed by applying compressive loads to the outer tube only to reveal the load transfer mechanisms and efficiency. Results show that the compressive stress applied to the outer tube can be efficiently transferred to the inner tube through the covalent bonds, which have stronger bonding energy compared to the weak van der Waals force in pristine DWNTs. The computational study also reveals that DWNTs with higher crosslink density have better load transfer performance. The findings in this paper are of particular value in the design and fabricate super strong CNTs reinforced composite and macroscale CNT fibers. The observations illustrate crosslinks play an important role in transferring load/energy between shells which has potential applications in MWNTs, multi-layer graphene sheets and high-strength CNT fibers.