Theoretical analysis and numerical simulation of electromagnetic parameters of Fe-C coaxial single fiber

Based on the Maxwell equation, the electromagnetic model in the coaxial fiber was described. The interaction with electromagnetic wave was analysed and the theoretical formula of axial permeability (μ∥), axial permittivity (ε∥), radial permeability (μ⊥) and radial permittivity (ε⊥) of Fe-C coaxial fiber were derived, and the demagnetization factor (N) of fibrous material was revised. Calculation results indicate that the composite fiber has stronger anisotropy and better EM dissipation performance than the hollow carbon fiber and solid iron fiber with the same volume content. These properties can be enhanced through increasing aspect ratio and carbon content. The μ‖ is 5.18-4.46i, μ⊥ is 2.58-0.50i, ε∥ is 7.63-6.97i, and ε⊥ is 1.98-0.15i when the electromagnetic wave frequency is 5 GHz with the outer diameter of 0.866 μm, inner diameter of 0.500 μm, and length of 20 μm. The maximum of the imaginary part of μ∥ and ε∥ are much larger than that of μ⊥ and ε⊥ when the structural parameters change, and the maximum of μ∥ and ε∥ can reach 6.429 and 23.59. Simulation results show that greater conductivity, larger aspect ratio, thin iron shell play important roles to improve the electromagnetic matching ability and microwave attenuation for the Fe-C coaxial fibers.