Mechanical recycling of carbon fiber composites: Development of hybrid composites of epoxy resin, carbon fiber, and carbon nanotubes for functional electromagnetic applications

Abstract Carbon fiber (CF)‐reinforced epoxy resin composites (CF/ER) are widely used in the aerospace industry due to their excellent properties and have been studied for use in the automotive industry to help reduce the weight of electric cars. With the increase in demand for these materials, the problem of disposal and accumulation of waste arises, with mechanical recycling being a sustainable alternative. This work evaluated using CF/ER composite waste after mechanical recycling to develop hybrid composites by adding ER and carbon nanotubes (CNTs). For the preparation of the hybrid composites, CNTs were mixed with ER using ultrasound, followed by the addition of CF/ER particles and mechanical homogenization. Different contents of CNTs (0.5 and 1 wt%) and CF/ER particles (10, 20, and 30 wt%) were tested. The mixture was molded and cured to form test specimens. The compositions were evaluated for thermal, mechanical, electrical, and electromagnetic properties. Hybrid composites with 1 wt% CNT and 20 wt% CF/ER particles achieved outstanding properties. They exhibited electrical conductivity higher than 10 −4 S/cm and achieved the highest electromagnetic shielding efficiency (25 dB) in the X‐band, demonstrating potential for functional electromagnetic applications. Highlights CF‐reinforced composite waste needs a viable and profitable destination. Recycled hybrid thermoset composites were prepared from ground CF/epoxy composite and CNT. Hybrid composites present good homogenization and interaction between fillers and the matrix. CNT was added to the recycled composites for higher electrical conductivity values. The recycled hybrid composites showed promising electromagnetic shielding properties.