Hybrid Basalt Fiber/Fe 3 O 4 – GNP Polymer Composites for High Performance Electromagnetic Wave Attenuation

Lightweight multifunctional composites integrating structural reinforcement with electromagnetic‐wave attenuation are promising for electromagnetic‐interference mitigation. Basalt‐fiber‐reinforced epoxy composites containing graphene nanoplatelets (GNP), Fe 3 O 4 , and their hybrid combination were fabricated and evaluated in the X‐band. Three formulations were investigated: B 15 G 5 F 0 (15 wt% basalt fiber, 5 wt% GNP), B 15 G 0 F 5 (15 wt% basalt fiber, 5 wt% Fe 3 O 4 ), and B 15 G 2.5 F 2.5 (15 wt% basalt fiber, 2.5 wt% GNP, and 2.5 wt% Fe 3 O 4 ). Structural and microscopic analyses confirmed incorporation of the functional phases, with localized agglomeration, and voids. B 15 G 2.5 F 2.5 exhibited the highest Vickers hardness (29.5 HV), compared with 21.5 HV for the basalt‐fiber composite. X‐band measurements revealed composition‐dependent complex permittivity and permeability. B 15 G 0 F 5 showed the strongest magnetic response, while B 15 G 2.5 F 2.5 achieved the lowest RL of approximately −23 dB near 10 GHz, with an effective absorption bandwidth (EAB) of ~1.8 GHz (RL ≤ −10 dB). In contrast, B 15 G 5 F 0 provided a broader bandwidth (~4.2 GHz) with RL of −10 to −11 dB. The results demonstrate that controlled Fe 3 O 4 /GNP hybridization can balance impedance matching, dielectric and magnetic losses, and mechanical performance.