Characterisation of Active Fibre Composites with polypyrrole finger electrodes

摘要

State-of-the-art Active Fibre Composites (AFC) are piezoelectric actuators made of one layer of unidirectionally oriented lead zirconate titanate (PZT) ceramic fibres contacted through two interdigitated electrodes (DDE) which are usually printed on a polymer film. The layup is impregnated with epoxy resin. One drawback of current AFC design are the electrodes which contact the fibres in only two small surfaces, namely top and bottom side of the fibres, thus introducing the electric field quite inhomogeneously. AFC with through-the-thickness finger electrodes have been developed: finger electrodes made of the conducting polymer polypyrrole/p-toluene sulfonic acid are electrochemically polymerised directly around the piezoceramic fibres. The behaviour of the actuators was investigated with Electronic Speckle Pattern Interferometry (ESPI), a laser interference technique. With this method it is possible to measure the strain and the elongation locally on every point of the AFC, without application of gauges which interfer with the actuators deformation. Results show an overall strain of the actuator of about 0.12% at 2.0 kV in fibre direction, compared to state-of-the-art AFC of the same design, which have at 2.0 kV a strain between 0.08% and 0.15%. In case of pAFC the electrode fingers are thicker than in case of screen-printed AFC, thus reducing the effective active length and increasing the inactive regions. The local strain of the fibres in the active region of pAFC - between the electrode fingers - reaches values of 0.187% compared to 0.166% for screen printed AFC.