Analysis of the Impedance Spectra of Short Conductive Fiber-Reinforced Composites.
Analysis of the Impedance Spectra of Short Conductive
Torrents, J. M.; Mason, T. O.; Peled, A.; Shah, S. P.;
Garboczi, E. J.
Journal of Materials Science, Vol. 36, No. 16,
4003-4012, August 2001.
fibers; cements; composite materials; impedance;
orientation; spectroscopy; spreading resistance
The presence of small amounts of short conductive fibers
in a composite of finite matrix conductivity results in
the subdivision of the one matrix impedance arc into two
separate low and high frequency arcs in the complex
impedance plane. These features are attributable to a
"frequency-switchable" interfacial impedance on the
fiber surfaces, rendering them insulating at DC and low
AC frequencies, but conducting at intermediate
frequencies. A combination of physical simulations
(single wires in tap water) and pixel-based computer
modeling was employed to investigate 'the roles of fiber
pull-out, debonding, and orientation on the impedance
response of fiber-reinforced composites. The ratio of
the low frequency arc size to the overall DC resistance
(gamma-parameter) is sensitive to pull-out and/or
debonding, especially when a fiber just barely makes
contact with the matrix. The gamma-parameter is also
quite sensitive to fiber orientation with respect to the
direction of the applied field. Ramifications for the
characterization of cement, ceramic, and polymer matrix
composites are discussed.