Characterization of composites of recycled polyether ether ketone with reclaimed carbon fibers

Abstract

This study investigates the fabrication and characterization of recycled polyether ether ketone (rPEEK) composites reinforced with 5–25 wt% reclaimed carbon fibers (rCF), produced by twin-screw extrusion and injection molding. SEM and X-ray micro-computed tomography revealed homogeneous fibers dispersion within the rPEEK matrix. Porosity remained between 4.0% and 7.4% up to 20 wt% rCF but increased to 15.9% at 25 wt% rCF. Significant fiber fragmentation during processing reduced the average fiber length to approximately 50 µm, well below the estimated critical fiber length (∼292 µm), indicating subcritical reinforcement and limited stress-transfer efficiency. Despite these limitations, the addition of rCF significantly improved mechanical performance. The tensile modulus increased from 3.1 GPa for neat rPEEK to 6.2 GPa at 25 wt% rCF, while tensile strength reached 113 MPa. Conversely, strain at break and impact strength decreased from 38% to 5% and from 8.9 to 5.9 kJ/m 2 , respectively, due to stress concentrations, interfacial debonding, and fiber pull-out. DMA confirmed increased stiffness and reduced damping capacity with increasing fiber content. The composites retained excellent thermal stability, with the onset of degradation remaining near 560°C. Overall, rPEEK/rCF composites represent a sustainable route to high-performance materials with potential applications in automotive and aerospace sectors.