Enhancing through-thickness electrical conductivity in recycled carbon fiber-reinforced polymer composites using machining waste

CFRP (carbon fiber-reinforced polymer) production in Europe is approximately 10,000 metric tons annually, and according to the UK authorities, approximately 35% of end-of-life CFRP waste is currently landfilled. The authors propose a novel recycling process for industrial CFRP waste particles to produce the core of a sandwich CFRP panel through the direct molding method. Industrial CFRP powder from grinding operations was collected, sieved and molded into square panels with and without external skins of virgin CFRP prepreg. Thermogravimetric (TGA) and differential scanning calorimetry (DSC) analysis revealed thermal activation (~70 °C), indicating potential for reprocessing. This study proposes a novel recycling route that directly molds industrial CFRP grinding waste into the core of sandwich structures, with or without virgin CFRP prepreg skins. Key findings: thermal re-processability was confirmed through TGA and DSC, showing activation near 70 °C; electrical conductivity reached 0.045 S/cm through the thickness in sandwich panels, with recycled cores maintaining comparable conductivity (0.04 S/cm); mechanical performance was improved significantly with prepreg skins, as evidenced by three-point bending tests showing enhanced stiffness and strength. These results demonstrate the potential of recycled CFRP waste in multifunctional structural applications, supporting circular economy goals in composite materials engineering.