| In recent years, the use of thermoplastic composites (TPC) increased significantly because of their low cost, fast processing cycles and recyclability. In an effort to provide a manufacturing technique well suited for large TPC parts, Delft University of Technology has developed an infusion process based on a reactive anionic polyamide-6 (APA-6) resin system. Following recent work where significant differences in mechanical and physical laminates property with respect to flow direction were identified, the work presented in this thesis aims at improving laminate uniformity by testing different heating set-ups and infusion strategies.;First, the fibre coupling agent, contained in the proprietary 8225 finish, was tested to assess its compatibility with APA-6. Results show that this fibre coupling agent is compatible with the APA-6 matrix system, but is not better or worse that the previous 8207 finish used in previous work done at TU Delft.;Through a second study, key laminate properties were evaluated (ILSS, crystallinity and degree of conversion) using two different heating set-ups (platen press and infrared panels) over three different curing temperatures (160-180°C). The results of this study identified that the infrared method yielded better laminates than the platen press set-up. However, most laminate produced still had non-uniform properties with respect to flow direction, but laminates cured at 180°C showed better average properties.;Based on these results, to improve property uniformity, a third study was conducted using the double infusion strategy: a low infusion temperatures (110-150°C) followed by a curing step performed at 180°C. The results showed that the best laminate uniformity could be achieved with this double infusion strategy at infusion temperatures between 110°C and 130°C. The Tm and ILSS of these laminates exhibited lower standard deviation when compared to the one infused at 150°C and the one polymerised with a non-isothermal strategy. This uniformity enhancement was also validated with comparative laminate C-scans and optical microscopy results.;Keywords: Composite materials, polyamide, anionic polymerisation, Thermoplastic vacuum infusion, interphase, interlaminar shear strength, Differential scanning calorimetry. |
