Microwave characterization of carbonyl Fe55Ni45 fiber-filled composites

Fiber-filled composites have the ability of tailoring the electric and magnetic properties and can be suitable for use as microwave lenses, high-strength low weight electromagnetic interference (EMI) shielding materials, radar absorbing materials (RAM), antennas and waveguides, etc. The subject of this paper is to examine the microwave characterization of carbonyl Fe₅₅Ni₄₅ fiber-filled composites. With the method of the transmission and reflection waveguide, the complex permittivity and permeability of carbonyl Fe₅₅Ni₄₅ fiber-filled composites in S-band (2-4 GHz) were measured by a vector network analyzer. The reflection loss of these composites was also calculated in this frequency range. The results show that the strong skin effect can decrease the conductivity of fiber and ultimately reduce the effective permittivity of fiber-filled composites. The lower aspect ratio of carbonyl Fe₅₅Ni₄₅ fiber gives rise to the decrease of the effective magnetic field and the permeability. It was also found that the reflection loss of the composites is influenced more greatly by the low permittivity than that by thickness.