Tensile Strength of CNT Fibres: Characteristic Length, Stress Transfer and other Impact Factors

The initial strength hype over carbon nanotubes arose from predictions of the strength of individual graphene layers, encouraged by measurements of individual MWCNTs and SWCNT bundles in AFM [1, 2]. However, while the scientists were professionally explicit as to what they had measured, the publicity assumed that these figures could also be readily realized in materials made from these components. It’s against a background of this overselling that we examine the gradual improvement in strength of macroscopically useful materials. Yarn-like fibres composed of carbon nanotubes made by the direct spinning process [3] have been used as the subject of this study. There have been occasional observations of strengths greater than 5 N/tex [4], which have served to maintain the enthusiasm for on-going developments. Here, we will re-examine those high strength reports in the context of the response of nanotubes aggregates to applied tensile stress.