On the low reinforcing efficiency of carbon nanotubes in high-performance polymer fibres

Driven by the exceptionally high mechanical properties of carbon nanotubes (CNTs), over the years an extensive research effort has been devoted to the reinforcement of high-performance polymer fibres with CNTs. However, to date, improvements in the strength of these fibres have been rather modest even for relatively high CNT contents. After a brief review of CNT reinforced polymer fibres, here, analytical and numerical finite element models will be used to show that these experimental findings are to be expected based on the intrinsic mechanical properties of these polymer fibres and CNTs, their aspect ratio and interfacial characteristics. Results show that for realistic CNT contents and aspect ratios, the extraordinary strength of CNTs cannot be easily fully exploited in high-performance polymer fibres like Dyneema (R) or Kevlar (R). Even if CNTs are perfectly aligned, bonded and dispersed, the low intrinsic shear strength of these highly anisotropic polymer fibres limits effective stress transfer and nanotube reinforcement.