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

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.