Piezoresistivity in continuous carbon fiber polymer-matrix composite

Piezoresistivity involving the volume resistivity of a continuous unidirectional carbon fiber epoxy-matrix composite in the fiber direction decreasing reversibly upon tension in the fiber direction was observed by the four-probe method, due to an increase in the degree of fiber alignment. Use of the two-probe method resulted in measurement of the contact resistance rather than the volume resistance. The contact resistance increased reversibly upon tension.