Piezoresistivity was observed in continuous unidirectional carbon fiber cem
ent-matrix and polymer-matrix composites. The fiber volume fraction was 2.6
-7.4% and 58% for cement-matrix and polymer-matrix composites respectively.
The DC electrical resistance in the fiber direction increased upon tension
in the fiber direction for the cement-matrix composite, due to fiber-matri
x interface degradation, but decreased upon tension for the polymer-matrix
composite due to increase in the degree of fiber alignment. (C) 2000 Kluwer
Academic Publishers.