In-situ tailored repair of thermoplastic composites by overprinting of continuous carbon fibre reinforced polymer filaments

This study proposes an efficient and convenient in-situ repair approach for damaged thermoplastic composites by 3D overprinting. Continuous carbon fibre reinforced polyphenylene sulphide (CCF/PPS) filament was employed to overprint repair patches onto conventionally manufactured woven polyamide 6 (PA6) laminates. The process window was optimised through thermal analysis of the target polymers, with a temperature range spanning from the melting point of PA6 (216.8°C) to the crystallisation point of PPS (227.6°C). A nominated interface temperature of 220 °C was evidenced as the most effective, raising the tensile strength of repaired specimens to 205.9 MPa, an improvement of 35 % compared to open-hole laminates and a recovery of nearly 50 % of the strength lost relative to undamaged specimens. Additionally, bio-inspired spider web printing paths were tailored for static indention loading, restoring 94 % of the original laminate strength while reducing material usage by 67 % compared to conventional unidirectional patches. This novel overprinting approach offers a highly efficient and flexible solution for repairing damaged thermoplastic structures.