Recycling of carbon fiber reinforced epoxy composites

Composite materials are extensively used across various industries due to their high strength-to-weight ratio, corrosion resistance, and durability. However, the increasing use of thermoset-based composites has raised critical concerns regarding end of life waste management, as they are difficult to recycle through conventional methods. Among emerging technologies, microwave-assisted acid digestion has gained attention as a promising, efficient, and environmentally friendly recycling approach. This study investigates the closed-loop recycling of carbon fiber reinforced polymer (CFRP) waste using a rapid microwave-assisted nitric acid digestion method. A parametric study was conducted by varying the process temperature (120 °C–150 °C) and microwave irradiation hold time (5–10 minutes) while keeping other parameters constant. In this working range, the most suitable condition was determined to be 10 minutes at 150 °C, and 99% resin removal efficiency was achieved. Recycled carbon fibers were characterized and compared to pristine fibers using Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), and Raman spectroscopy. The recycled fibers retained their structural integrity, showing no visible surface etching, no change in fiber diameter, and minimal resin residue. A comparison of the ID/IG ratios across different recycling processes indicates that there is no structural change occurred during recycling process. These findings highlight the significance of developing fast, clean, and scalable recycling technologies for thermoset composites, especially in high-performance applications like aerospace. The successful recovery of carbon fibers not only proves the feasibility of this method but also supports the advancement of closed-loop recycling systems. The recycling cycle defined by varying time and temperature parameters can serve as a foundation for future studies. As the recycled fibers preserved their structural integrity, they appear suitable for reuse, though further research is needed to evaluate their mechanical performance compared to virgin fibers for potential manufacturing applications.