Non linear behavior of piezocomposites in power resonant devices

A comparative study between the nonlinear behavior of a composite and the p iezoceramic, that has been used for it, has been carried out. This characte rization is necessary to use the composite in power transducer applications . A study of the changes on the losses and the resonator stiffness has been made. These changes, and also the possibility of the frequency hysteresis, show different behaviors in the composites, because they very quicker in t he ceramics than in the composite. To carry out this study two measuremet m ethods are used, mainly the measurement of the motional impedance increase with the motional current. The results obtained have been normalized in ord er to make them independent of the resonator size and to make easier the co mparison between the composite and the ceramic. The figure of the mechanica l losses tangent versus the average strain shows that the losses could be g reater in the ceramic than the composite, in certain conditions. The depend ence behavior of the losses and stiffness increases versus the average stra in has been studied, for both resonators.