Influence of fiber weave geometry and Fe 3 O 4 content on the electromagnetic shielding behavior of CFRP composites

This study examines the electromagnetic interference (EMI) shielding effectiveness (SE) of carbon fiber reinforced polymer (CFRP) composites enhanced with magnetite (Fe 3 O 4 ). Three carbon fiber weave architectures – twill, plain, unidirectional – were produced with 5, 10, and 15 wt.% Fe 3 O 4 to evaluate the effects of fiber orientation and filler content on shielding performance. Measurements were conducted under near-field (NF) and far-field (FF) conditions in the 4–6 GHz range using free-space techniques and a vector network analyzer. Reflection, absorption, and transmission characteristics were analyzed alongside complex permittivity, permeability, dielectric and magnetic loss tangents, and frequency-dependent electrical conductivity to clarify material–wave interactions. Fe 3 O 4 powders were characterized by X-ray fluorescence (XRF) and X-ray diffraction (XRD), while composite morphology was examined via scanning electron microscopy. Mechanical behavior was assessed through impact testing. The 5 wt.% Fe 3 O 4 twill composite achieved the highest NF shielding (54.66 dB), whereas the 10 wt.% Fe 3 O 4 unidirectional sample showed the best FF performance (49.27 dB). Unidirectional composites exhibited the greatest impact strength, peaking at 1.6096 kJ/m 2 for the 10 wt.% sample. Results indicate that twill architecture improves local field disruption at lower filler levels, while unidirectional geometry enhances FF performance through anisotropic conductive pathways. Excessive Fe 3 O 4 loading (15 wt.%) led to performance saturation, indicating an optimal reinforcement threshold.