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

Abstract 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.