CNT fibres - yarns between the extremes
AbstractThe carbon nanotube community swims in the sea of superlatives. Researchers expect mechanical performance to achieve two extremes, an ultrastrong fibre taking us into space, and a superlubricant saving energy otherwise lost as heat. We examine CNT fibres in the light of traditional yarn science and present an interpretation of properties which combines aspects of these two extremes of performance.
Stress Transfer within CNT Fibres: A FEA Approach
Abstract Carbon nanotube (CNT) fibres are characterized by extreme anisotropy in their structure and physical properties. These fibres have been shown to have high axial strength, but poor shear strength between carbon nanotubes; for this reason it is difficult to transfer stress uniformly acrossthe fibre cross section. Here, Finite Element Analysis (FEA) is used to predict the stress distribution and the stress-strain curves of CNT fibres. The resultsdemonstrate that, in accordance with St. Venant principle,very considerable length-to-diameter ratios (> 10 3 ) are required to obtain a uniform stress distribution within the fibres even in the presence of low applied strain.
Mechanical Performance of CNT Fibres
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. The challenge for fibres composed of carbon nanotubes (CNTs) is to translate the impressive properties of the individual carbon nanotubes into the fibres. Yarn-like fibres composed of carbon nanotubes made by the direct spinning process have been used as the subject of this study. There have been occasional observations of strengths greater than 5 N/tex, which have served to maintain the enthusiasm for on-going developments. Here, we will re-examine those reports in the context of the response of nanot…
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 obser…
Mechanical properties of carbon nanotube fibres: St Venant’s principle at the limit and the role of imperfections
Abstract Carbon nanotube (CNT) fibres, especially if perfect in terms of their purity and alignment, are extremely anisotropic. With their high axial strength but ready slippage between the CNTs, there is utmost difficulty in transferring uniformly any applied force. Finite element analysis is used to predict the stress distribution in CNT fibres loaded by grips attached to their surface, along with the resulting tensile stress–strain curves. This study demonstrates that, in accordance with St Venant’s principle, very considerable length-to-diameter ratios (∼103) are required before the stress becomes uniform across the fibre, even at low strains. It is proposed that lack of perfect orienta…