Multiscale PA6 Composites Reinforced With Recycled Carbon Fibers and Graphene: Synergistic Effects on Mechanical and Electromagnetic Behavior

Abstract

The mechanical recycling of carbon fiber‐reinforced thermoplastics (CFRTs) generally degrades the mechanical properties of the resulting composites, primarily due to fiber length reduction. To partially overcome this limitation, this study developed multiscale polyamide 6 (PA6) composites containing mechanically recycled CFRTs (up to 20 wt%) and graphene nanoplatelets (GNPs, up to 5 wt%) through melt mixing, followed by extrusion and injection‐molding. Morphological and thermal analyses indicated that the two‐dimensional GNPs may act as physical bridges at the carbon fiber‐matrix interface. This multiscale filler system produced a synergistic mechanical response; the PA6/3GNP/20rCFRT composite achieved an ultimate tensile strength of 127 MPa and an elastic modulus of approximately 5 GPa, while theoretical models indicated a significant increase in the fiber efficiency factor. Furthermore, the multiscale architecture successfully imparted multifunctional electromagnetic properties. The multiscale composites achieved a total electromagnetic interference shielding effectiveness (EMI SE) of 20 dB, together with a promising reflection loss of −26 dB. These findings demonstrate that a multiscale filler system with GNPs provides an effective and scalable strategy for upcycling CFRT waste into advanced multifunctional structural and electromagnetic shielding materials.