A Comparison of Dynamic Piezoactuation of Fiber-based Actuators and Conventional PZT Patches

This work aims to extend investigations of the dynamic flexural actuation of a cantilever beam to fiber-based actuators (e.g., active fiber composite (AFC) or macro-fiber composite (MFC)), which consist of a single level of unidirectionally aligned piezoceramic fibers surrounded by a polymer matrix and electrically loaded by interdigitated electrodes. The main advantage of such actuators is their poling in the same direction as the beam length, i.e., they are able to act with the piezoelectric strain constant d 33 that is about two times higher than the piezoelectric strain constant d 31 used in PZT patches. Modeling using the finite element method is based on the multiplication in both plane directions of a unit cell, which is taken as a fiber unit (with its matrix) within two pairs of half-electrodes of the same polarity. Modeling of the whole system is possible practically only with MFC actuators, whose fibers have a rectangular section, thus reducing the number of required finite elements. In addition to a non-uniform longitudinal free extension of the electrically loaded piezofiber-based actuator, a lateral free shearing has been calculated, which results in a non-planar deformation of the actuator. When two such MFC actuators are bonded on both sides of an aluminum cantilever beam and loaded in the antiphase mode, they conduct into all flexural resonance modes of the actuated beam, as expected. However, a slight interference by the torsion eigenmodes of the actuated beam has also been detected, which was not present in the actuation type using (leadzirconate titanate) PZT patches. The experimental validation of these FEM results first confirms the static values for free strain components of the MFC actuator depending on the loading voltage, then dynamic values regarding the eigenfrequencies, as well as the acceleration amplitudes of the MFC actuated vibrating beam.