Orthotropic electro-thermal behaviour of highly-aligned carbon nanotube web based composites

A ‘forest’ of vertically aligned carbon nanotubes (CNTs), synthesised by chemical vapourdeposition with an iron catalyst on a silicon substrate, is drawn into a horizontally-alignedCNT web. Previous work has shown that the electro-thermal properties of this web maybe tuned by altering the individual length of the CNTs and the number of layers. Thispaper demonstrates, for the first time, that the orientation and multi-directional layeringof the web provides further scope for tuning the electrical conductivity and heatdistribution of the composite system. An analytical model based on the thermalconduction theory of anisotropic solids is proposed to predict the electrical conductivityof general multi-layered and multi-directional CNT webs.Specimens with different aspect ratios and web orientations were manufactured and theirelectrical conductivity and resistive heat distribution measured. All of them were shownto exhibit electrical properties and heating distributions which could be predicted orbounded by the analytical model. Consequently, through tuning the CNT web orientationand layup, various heating patterns may be obtained and designed for specific requirements.