Recycled composite materials from plastic parts of end-of-life vehicles mixed with recycled carbon fiber from automotive manufacturing waste

The production of virgin carbon fiber (vCF) is an energy-intensive process. The recycled carbon fiber (rCF) plays a crucial role by reducing energy consumption, lowering environmental impact, and promoting circularity within the composite materials industry. This study explores the recycling potential of prepreg carbon fiber waste and discarded automotive bumpers for producing composites from waste. The CFRP waste was recycled through a controlled thermal process and the resulting weight loss behavior obtained via a muffle furnace was evaluated using a design of experiments and analysis of variance. Optimization identified 500 °C with a 60 min holding time as the most effective condition, yielding clean rCF with minimal degradation and a residual mass of approximately 51.74 wt.%. The rCF was compounded with shredded car bumper at 0, 5, and 10 wt.% fiber contents. Incorporation of 10 wt.% rCF increased the tensile strength from 14.12 MPa to 19.40 MPa (+37.4%) and the flexural strength from 23.72 MPa to 29.12 MPa (+22.6%), whereas impact strength decreased from 269.12 J/m to 66.11 J/m (−75.4%) due to reduced energy absorption. The 5 wt.% rCF composites exhibited the highest tensile modulus of 0.69 GPa, indicating superior stiffness, while the 10 wt.% rCF composites demonstrated a slightly lower modulus of 0.53 GPa (−23.2%) but higher strength and hardness, suitable for load-bearing and wear-resistant applications. These results demonstrate that both CFRP and automotive plastic wastes can be effectively recycled into value added composites with tunable mechanical properties, supporting the circular economy and reducing energy intensive vCF.