Electrical Impedance Spectra to Monitor Damage During Tensile Loading of Cement Composites.
Electrical Impedance Spectra to Monitor Damage During
Tensile Loading of Cement Composites.
(3661 K)
Peled, A.; Torrents, J. M.; Mason, T. O.; Shah, S. P.;
Garboczi, E. J.
Title No. 98-M34;
ACI Materials Journal, Vol. 98, No. 4, 313-322,
July/August 2001.
Keywords:
cements; carbon fibers; cement composites; impedance;
fracture process; electrical properties; spectroscopy;
bridging area
Abstract:
Use of conductive fibers can reinforce concrete and
monitor damage leading to the development of a smart
material. This work studied the correlation between the
electrical (DC and AC) and mechanical properties of
cement composites reinforced with conductive carbon
fibers. The tensile behavior and impedance behavior of
extruded and notched composites with a fiber volume
fraction of 0.5% or 3% were examined, with the
mechanical load and electrical field applied
longitudinally (in the direction of extrusion). The
crack growth of these composites during loading was
observed and analyzed by Digital Image Correlation
(DIC). A good correlation between the electrical and
mechanical properties was found, in that when a sudden
growth in the crack was observed, a dramatic change was
also noticed in the impedance values. Taking advantage
of the special frequency-dependent electrical properties
of conductive fiber-reinforced composites, impedance
values measured during the fracture process were used to
distinguish and calculate three different areas at the
crack front: uncracked area, bridging area, and open
area. The bridging area is the zone where the fibers
bridge the propagating crack. A greater bridging area
was found for the 0.5% fiber composite, compared to the
3% fiber composite. This can be explained based on
differences in the final length of the carbon fibers in
the two composites.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899