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Title: Plasma treatment of carbon nanotubes and carbon fibre for use in composite materials
Author: Williams, John David
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2013
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The performance of components, structures and vehicles are always in some way limited by the materials they are made from , often leading to compromises. This drives development to invent and discover new materials or processes to improve upon the current state of the art. In this respect the research contained in this thesis has investigated the use of plasma treatment~ as a method for modifying the properties of carbon nanotubes and carbon fibres to improve upon current composite materials technology. The initial study focused on functionalising relatively large quantities of carbon nanotubes using a unique and scalable technique suitable for industrialisation. The research began with a standard oxygen and ammonia treatment, which led to the development of an oxygen plasma treatment for increased carboxyl functionality. The important discoveries were that processing time and gas pressure had a large impact upon the agglomerate size, bulk density, surface energy, solvent stability and the quantity of carboxyl functionalisation. The treated carbon nanotube~ developed in the initial study were investigated for their use within an epoxy system. The treated carbon nanotubes were shown to disperse better, reduced resin viscosity, increase resistivity, but had little effect upon mechanical properties, degree of cure or glass transition temperature compared to the untreated carbon nanotubes. The development of the oxygen treated carbon nanotubes led the research to investigate if these treated carbon nanotubes could be used to improve the fracture toughness of a pre-preg system. The results showed that it was possible to improve initiation and propagation mode I fracture toughness significantly. Mode II results also showed increased initiation but relatively unchanged propagation toughness at lower areal densities, however in both mode I and II at the highest carbon nanotube coating density the fracture propagation resistance was reduced. The final study looked into the use of plasma treating carbon fibres as a method to modify the fibre matrix interface. The interface strength was found to improve for short oxygen and ammonia treatments, while reduce for the tetrafiuoromethane treatment on the unsized fibres . However for the commercially sized fibres each plasma treatment appeared to damage the propriety treatment in terms of interface strength. A further investigation into attaching carbon nanotubes to carbon fibres showed a dramatically reduced interface strength. The research demonstrates a variety of methods which could be used to tailor the interface for improved strength or damage tolerance.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available