Fracture strength of carbon nanotubes with interwall sp3 bonding and intrawall vacancy defects

In the discipline of nanomaterials, the outstanding mechanical properties of nanoscale fibres and tubes (carbon nanotubes or CNTs) make them highly attractive as potential reinforcing constituents in polymer, ceramic or metal matrices. They are expected to form the next generation of advanced composites. However, achievement of high performance materials through this approach requires a fundamental understanding of the mechanics of nanoscale reinforcement, which may be quite different to micron-scale reinforcement. Single-wall CNTs (SWCNTs) appear ideal for use in material reinforcement with theoretical tensile strengths approaching 100 GPa. But, like most brittle materials, SWCNTs contain fabrication defects that lower their strengths below the ideal level. In many applications, multi-wall CNTs (MWCNTs) have been used due to their lower cost, availability, and ease of fabrication. MWCNT structures can vary widely depending on the fabrication process, and so MWCNTs are considered to be defective and disordered relative to SWCNTs, and to have lower strengths.