Modeling and characterization of piezoelectric fibers with metal core

A simple physical model of the first vibration mode of piezoelectric fibers with a metal core is developed for predicting their properties from the parameters of constituents. It is shown that the metal core diameter influences the piezoelectric properties of the fiber only to a lesser extent for diameter ratios lower than 0.3. The good accuracy of the model is confirmed by finite element modeling (FEM). A characterization procedure for actual fibers is then proposed. The properties of the piezoceramic constituent can be deduced from the fiber behavior, which is a precious too] for checking fiber quality. This procedure is applied to experimental Pb(Nb,Ni)O-3-Pb(Zr,Ti)O-3 fibers with a platinum core. The actual d(31) is - 112 pC/N for the ceramic phase of the fiber instead of -246 pC/N for the bulk material. It is believed that the poling process (constraints due to the metal core) and the density optimization are the two key factors for improving these performances.