Effects of atomic vacancy defects and their evolution mechanisms on the fracture of carbon nanotubes

CNTs produced by traditional physical and chemical methods inevitably have some defects. The existence of defects has a great impact on the physical, chemical and mechanical properties of CNTs. This article presents a method for evaluating the influence of vacancy defects on the fracture mechanism of carbon nanotubes using the C–C bond fracture criterion. The objective of this approach is to develop a finite element model of carbon nanotubes that includes atomic vacancy defects, allowing for the analysis of the evolution of these defects into dislocations. Specifically, this study utilizes a finite element model to simulate the fracture behavior of carbon nanotubes. Additionally, X-ray diffractometer and Raman spectrometer techniques are employed to characterize and analyze complete carbon nanotubes with atomic vacancies and defects throughout the evolution process. The findings indicate that vacancy defects significantly reduce the tensile strength and ultimate strain of Carbon nanotubes, with reductions of approximately 20–30% and 12–18% in tensile strength and final strain, respectively. The diffraction and Raman spectra uncover the evolution mechanism of carbon nanotubes from point defects to dislocation until fracture, and further demonstrate the substantial decrease in their mechanical properties resulting from stress concentration.