Fibre Sizing Effect on the Adhesion Between a Carbon Fibre and a Reactive Thermoplastic Polymer

The present work, part-funded as part of the Innovate UK Thermoplastic: Monomer to Automotive Parts (TMAP) project, focuses on investigating the fibre sizing effect on the degree of adhesion between carbon fibre utilised in a 3D-woven fabric, and a reactive thermoplastic polymer, with the end goal being for the material combination to be potentially utilised in the automotive sector. This paper discusses how the apparent interfacial shear strength (IFSS) is influenced by the sizing chemistry of the carbon fibre and attempt to produce, and apply, alternative sizing formulations to provide enhanced performance by re-sizing as-received fibres. For studying the IFSS value, the single fibre fragmentation technique (SFFT) was selected. The results indicated that the IFSS was strongly dependent on the sizing chemistry applied, and that the degree of adhesion observed for a thermoplastic polymer bonded to a fibre coated in a thermoplastic sizing was lesser than the equivalent epoxy combinations. It was observed that the IFSS was the largest for the industry coated fibres, with the thermoplastic sizing applied providing the largest respective IFSS. Notably it was shown that the re-sized fibres did exhibit varying IFSS values depending on the formulation, as well as the process for applying the new sizing. Whilst these IFSS values were observed to be less than those found for the industry sized fibre, observations made from the SFFT suggested that this may have been more down to the removal of the initial sizing, and re-coating process for the fibre in its 3D-woven form being inconsistent. From the results presented it is hypothesized that the new sizing formulations did provide adhesion with the reactive thermoplastic polymer, and that would further investigation and development, could provide enhanced adhesion between carbon fibre and reactive thermoplastic polymers.