Reuse of Mechanically Recycled Carbon Fiber Waste as Secondary Reinforcement in CFRP Composite Laminate

The increasing accumulation of carbon fiber reinforced polymer waste has created an urgent need for sustainable recycling strategies capable of preserving material value while maintaining mechanical performance. In this study, mechanically recycled carbon fiber microparticles were utilized as secondary reinforcement in epoxy matrices and multilayer CFRP laminates. Particle-modified epoxy systems containing 0-3 wt.% recycled carbon fiber were first evaluated to determine the optimum reinforcement ratio, after which laminates were manufactured using the selected composition (3 wt.%). Flexural and tensile performances were experimentally investigated in accordance with ASTM standards, and thermo-mechanical behavior was analyzed through dynamic mechanical analysis. Results demonstrated that incorporation of 3 wt.% recycled carbon fiber increased the flexural modulus and strength of epoxy by approximately 11% and 15%, respectively, indicating effective stress transfer and crack-hindering mechanisms at the matrix level. When applied to CFRP laminates, the same particle content led to a 4.8% increase in flexural modulus and a 15.7% improvement in flexural strength. The enhanced performance is attributed to micro-scale crack bridging and improved interlaminar stress redistribution induced by dispersed recycled particles. Dynamic mechanical analysis results showed only minor variations in glass transition temperature, confirming that particle addition did not adversely affect thermal stability. Overall, the findings demonstrate that mechanically recycled carbon fiber particles can serve as an effective and sustainable reinforcement phase, enabling the high-value reuse of composite waste while improving the mechanical performance of epoxy-based composite structures.