Multiscale investigation of EMI shielding performance in carbon black-reinforced epoxy composites

This study presents an integrated experimental and analytical investigation of the electromagnetic interference (EMI) shielding effectiveness (SET) of carbon black (CB)-reinforced epoxy composites. Composites were fabricated using a simple hand lay-up technique with CB filler contents ranging from 4 wt.% to 40 wt.%. SET was evaluated in the X-band frequency range (8–12 GHz) using a calibrated Vector Network Analyzer (VNA), relevant to radar, satellite, and wireless communication applications. An analytical model based on classical electromagnetic wave theory was developed to predict total shielding by incorporating reflection, absorption, and multiple internal reflections. Results revealed that absorption dominated the overall shielding response, contributing more than 80–85% of the total attenuation, confirming the material’s suitability for high-frequency EMI suppression. The model showed strong agreement with experimental results, with a mean absolute deviation of 10.16 dB, confirming its validity for preliminary design assessments. Increasing CB content significantly enhanced shielding performance, achieving a maximum SET of 47.48 dB at 25 wt.% representing nearly a 40% improvement relative to low-loading composites. HFSS field simulations further verified strong electromagnetic attenuation and absorption-driven energy dissipation within the composite structure. Minor deviations between model and experiment underscored the importance of uniform filler dispersion. Overall, the findings demonstrate that CB/epoxy composites offer a lightweight, cost-effective, and efficient alternative to traditional metallic EMI shields, providing a rare multiscale correlation across experimental, analytical, and numerical domains.