How do the mechanical properties of carbon nanotubes increase? An experimental evaluation and modeling of the engineering tensile strength of individual carbon nanotubes

To enable the development of multiwalled carbon nanotubes (MWCNTs) with superior mechanical properties, a theoretical model of the tensile strength of MWCNTs is developed, and the structural- mechanical property relationships of MWCNTs are investigated using experimental results obtained by uniaxial tensile tests from this study and data from the literature. We show that the nominal tensile strength is an important design factor in determining the mechanical properties of composites reinforced with carbon nanotubes (CNTs) and that the nominal (engineering) tensile strength is written as a product of the fracture strength (effective strength) and fracture cross-section ratio that can be calculated by the fracture cross-sectional area divided by the full cross-sectional area including the hollow core. Based on this model, controlling the degree of intershell crosslinking to produce clean break fractures in the nanotube shells without a dramatic degradation of the fracture strength is important for improving the nominal tensile strength.