First observation of the inductance of a fibrous composite material, with the inductance mainly contributed by the fiber-fiber contacts

The first experimental observation of the inductance of a fibrous composite material is provided. A coil-less unidirectional continuous carbon fiber polymer-matrix composite, with cross-sectional area (width×thickness) A (0.5 × 3 mm²), B (1 × 5 mm²) and C (2 × 10 mm²), fiber volume fraction 70% and resistivity 2.3 × 10⁻³ Ω.cm, is studied. The reactance is totally inductive. The microstructure (the fiber-waviness-induced fiber-fiber contacts) contributes 49%−79% of the measured inductance, compared to ∼90% for the fiber tow. The polymer matrix diminishes the effect of the fiber-fiber contacts, which remain the dominant contributor to the inductance. The composite approximately consists of inductors in series and parallel. Longer length and smaller area promote the inductance. Shorter length and smaller area enhance Q. The phase angle θ is enhanced by increasing the area, which reduces the resistance. The maximum θ increases in the order: Size A (45°), Size B (70°) and Size C (85°), due to the decreasing resistance.