Analytical model of piezoresistivity for strain sensing in carbon fiber polymer-matrix structural composite under flexure

An analytical model is provided for the piezoresistive phenomenon of continuous carbon fiber polymer-matrix composite under flexure. This phenomenon allows strain sensing and entails reversible increase of the tension surface resistance and reversible decrease of the compression surface resistance during flexure. The model considers the surface resistance change to be due to change in the degree of current penetration. The longitudinal strain resulting from the flexure affects the through-thickness resistivity (which relates to the contact resistivity of the interlaminar interface). Good agreement is found between the model and prior experimental results, except that the calculated surface resistance on the tension side is higher than the measured value, when the magnitude of the average longitudinal strain on the surface exceeds 3 × 10^-3.