2025/08/19
Valorisation de rebuts de production de préimprégnés composites thermoplastiques pour la fabrication additive
Richard Soucy, Ruan-Isabelle (2025). Valorisation de rebuts de production de préimprégnés composites thermoplastiques pour la fabrication additive. Mémoire de maîtrise électronique, Montréal, École de technologie supérieure.
The manufacturing of pre-impregnated rolls made from unidirectional carbon fibre and thermoplastic-matrix involves edge trimming, as they do not meet the specifications in terms of thickness and fibre content. This prepreg waste, referred to as tape edge trim (TET) waste, account for up to 15% of the pre-impregnated mass and are typically sent to landfills. The objective of this thesis is to present a method for valorizing thermoplastic pre-impregnated waste through additive manufacturing process using fused-granular-fabrication (FGF). The TET waste made from carbon fibre/PEKK, are first transformed into printable pellets. During this process, neat PEEK polymer is added to the pellets to reduce the fibre content and improve the printing properties. DSC analyses are performed on these pellets to study the degradation of PEEK and PEKK after aging at 380 °C or 400 °C under oxidative conditions. Polymer degradation, attributed to crosslinking reactions, is observed through a reduction in crystallization temperature and a decrease in crystallinity. However, no degradation is observed in FGF samples, demonstrating that the printing process prevents these reactions due to short cycle times and insufficient oxygen concentration in the extruder head. A large-scale six-axis FGF robot is used to print boxes with recycled CF/PEKK-PEEK pellets. As is typically observed for parts manufactured using extrusion techniques, standard tensile and flexural specimens extracted from the FGF boxes exhibit anisotropic mechanical properties. Additional boxes are produced by FGF using pellets derived from shredded fragments of FGF boxes to evaluate the possibility to recycle the material a second time. A decrease in material stiffness and strength is then observed, which is attributed to the scission of polymer chains and the reduction in fibre length occurring during the shredding of the printed parts. This thesis demonstrates the potential to use CF/PEKK-PEEK pellets derived from thermoplastic pre-impregnated production waste for applications such as mold fabrication using FGF. Finally, a mold designed for the manufacturing of a stiffener is printed using FGF as a demonstrator.