Carbon Fiber/Stainless Steel Yarn/Epoxy Hybrid Composites with Highly Mechanical and EMI Shielding Performance

Hybrid composites integrating carbon fiber (CF) and stainless steel (SS) reinforcements provide a promising strategy toward simultaneous mechanical enhancement and electromagnetic interference (EMI) shielding. In this study, three CF/SS architectures, including laminated composite (LC), stitched laminated composite (SLC), and hybrid woven composite (HWC), were fabricated and compared. Tensile and flexural tests were conducted to assess the influence of hybrid architecture on mechanical behavior. Mechanical results showed that HWC exhibited the highest tensile strength (172.5 MPa) and flexural strength (152.52 MPa), outperforming LC and SLC due to more efficient load transfer and more uniform stress distribution enabled by the synergistic effects of intralaminar hybridization and mechanical interlocking at the yarn scale. EMI performance in the X band (8.2–12.4 GHz) indicated that all composites achieved a total shielding effectiveness above 36 dB. LC showed the highest absolute EMI SE (62.64 dB), whereas HWC exhibited the highest specific shielding effectiveness (262.64 dB·cm 2 /g), demonstrating that intralaminar hybridization achieved a superior balance between shielding efficiency and weight reduction through optimized conductive network density. These results demonstrated that intralaminar hybridization is an effective strategy for developing lightweight, mechanically robust, and EMI shielding multifunctional composites.