Numerical Investigation of EMI Shielding in Graphite Materials: From Porous to Dense Structures Using Finite Element Simulation

Electromagnetic interference (EMI) shielding is essential in modern electronics, telecommunications, and aerospace systems. Graphite-based materials are promising shielding candidates due to their tunable electrical conductivity, low density, corrosion resistance, and thermal stability. However, numerical studies investigating the combined effects of conductivity and thickness on shielding effectiveness (SE) across the X-band remain limited. This study presents a parametric finite element analysis of EMI shielding performance for graphite materials with electrical conductivities of 1, 10, 100, 1000, and 3000 S/m, representing structures ranging from highly porous to dense graphite. Thicknesses from 1 to 10 mm are simulated in a WR90 rectangular waveguide using finite element simulations. The Transition Boundary Condition (TBC) is employed to efficiently model conductive slabs without resolving the skin depth via volumetric meshing. Shielding effectiveness is evaluated from S-parameters and decomposed into total (SET), absorption (SEA), and reflection (SER) components. Results show that SET increases with both conductivity and thickness, and that shielding behavior is strongly dependent on conductivity. Low-conductivity graphite (σ = 1 S/m) exhibits absorption-dominated shielding, reaching an absorbed power fraction of 89% at 5 mm thickness. At σ = 10 S/m, the material enters a transitional regime where absorption and reflection contribute comparably. For highly conductive graphite (σ ≥ 100 S/m), reflection becomes dominant, with the reflected power fraction approaching 0.97 at σ = 3000 S/m. A conductivity-dependent saturation thickness is identified, beyond which additional thickness provides negligible shielding improvement. Dense graphite materials (σ ≥ 1000 S/m) reach saturation at approximately 1 mm thickness. Finally, a conductivity–thickness design heatmap is developed to guide the optimization of graphite-based EMI shielding materials.