Intrinsic conductivity of short conductive fibers in composites by impedance spectroscopy

Electrical property measurements (DC conductivity, impedance spectroscopy) were employed to determine the "intrinsic conductivities" of short conductive fibers in cement matrix composites. Intrinsic conductivity determines, in the dilute limit, the variation of overall conductivity (DC or AC) vs. volume fraction of fibers. Model composites consisting of steel wires (0.5 mm diameter), but with aspect ratios comparable to typical carbon or steel fibers used in cement/concrete, were shown to exhibit similar "dual-arc" impedance spectra as observed in actual composites. The results were compared with existing calculations for composites with randomly distributed right cylinders. The conductivity vs. aspect ratio behavior can be used to estimate the fiber aspect ratio in randomly distributed fiber composites.