A novel approach for introducing aligned multi-walled carbon nanotubes (MWCNTs) in a carbon-fibre composite pre-impregnated (prepreg) laminate, to improve the through-thickness fracture toughness, is presented. Carbon nanotube (CNT) 'forests' were grown on a silicon substrate with a thermal oxide layer, using a chemical vapour deposition (CVD) process. The forests were then transferred to a pre-cured laminate interface, using a combination of pressure and heat, while maintaining through-thickness CNT alignment. Standard Mode I and four-point bend end-notched flexure Mode II tests were undertaken on a set of specimens and compared with pristine specimens.Mode I fracture toughness for T700/M21 laminates was improved by an average of 31% while for T700/SE84LV specimens, an improvement of 61% was observed. Only T700/M21 specimens were tested in Mode II which yielded an average fracture toughness improvement of 161%. Scanning Electron Microscopy (SEM) showed good wetting of the CNT forest as well as evidence of penetration of the forest into the adjacent plies.

No abstract

Film uniformity is an issue in many deposition processes, especially in substrates with elongated lateral dimensions such as fibers. In this study, a plasma chamber was designed with dual electrodes to improve the uniformity of plasma polymer films.Plasma polymerized acrylic acid films were deposited via single or double electrode configurations onto silicon wafer pieces placed down the center of the chamber, to mimic the potential position of a fiber. A radial and spatial map of film chemistry and thickness throughout the chamber were determined and demonstrated improved radial uniformity and film stability using the dual electrode configuration, highlighting the importance of spatial characterization when designing a rector for the coating of three-dimensional objects such a fibers.

No abstract

Plasma-polymerised tetramethyldisiloxane (TMDSO) films are frequently applied as coatings for their abrasion resistance and barrier properties. By manipulating the deposition parameters, the chemical structure and thus mechanical properties of the films can also be controlled. These mechanical properties make them attractive as energy adsorbing layers for a range of applications, including carbon fibre composites. In this study, a new radio frequency (RF) plasma-enhanced chemical vapour deposition (PECVD) plasma reactor was designed with the capability to coat fibres with an energy adsorbing film. A key characterisation step for the system was establishing how the properties of the TMDSO films could be modified and compared with those deposited using a well-characterized microwave (MW) PECVD reactor. Film thickness and chemistry were determined with ellipsometry and X-ray photoelectron spectroscopy, respectively. The mechanical properties were investigated by nanoindentation and atomic force microscopy with peak-force quantitative nanomechanical mapping. The RF PECVD films had a greater range of Young’s modulus and hardness values than the MW PECVD films, with values as high as 56.4 GPa and 7.5 GPa, respectively. These results demonstrated the varied properties of TMDSO films that could in turn be deposited onto carbon fibres using a custom-built RF PECVD reactor.