Strain sensing in single carbon fiber epoxy composites by simultaneous in-situ Raman and piezoresistance measurements

The change of electrical resistance in continuous single carbon fibers and single carbon fiber/epoxy model composites with applied strain has been investigated with a new method combining simultaneous in-situ Raman and electromechanical measurements. In all cases, a sudden increase to infinity of the relative electrical resistance corresponds to fiber fracture. The gage factors of the piezoresistance curves were determined. Reinforcement/matrix interface are compared for sized and unsized systems. It is shown that, in principle, it is possible to correlate the fiber strain and the variation of electrical fiber resistance as a function of the applied strain for a single fiber embedded in epoxy. This study indicates that carbon fibers embedded in epoxy matrix may serve as electrical strain sensors to detect both their own onset of damage and that of the composite under load, prior to specimen fracture.