A new type of actuator composed of metal (brass) end caps and piezoelectric ceramics has been developed as a displacement transducer. Shallow cavities positioned between the metal caps and the central ceramic disk convert and amplify the radial displacement of the piezoelectric ceramic into a large axial motion of the metal end caps. Large da coefficients exceeding 2500 pC/N are obtained with the composite actuators. The behavior of the electrically induced strain with geometric variables, such as the thickness of the metal end caps, and with pressing force and driving frequency has been evaluated. Sizeable strains are obtained with both PZT (piezoelectric lead zirconate titanate) and PMN (electrostrictive lead magnesium niobate) ceramics. [

In recent years, piezoelectric and electrostrictive ceramics have been used in many actuators applications. A new type of composite actuator, which is based on the concept of a flextensional transducer, has been developed. (1-6) This ceramicmetal composite actuator, or "moonie" consists of either a piezoelectric ceramic disk or a multilayer stack sandwich between two specially designed metal end caps. This new design provides a sizeable displacement, as well as a large generative force. In other words, it bridges the gap between the two most common types of actuator; the multilayer and bimorph (7).

A new type of metal-ceramic composite transducer, the "moonie,' has been developed by sandwiching a poled lead zirconate titanate (PZT) ceramic between two specially designed metal end caps. Piezoelectric coefficients an order of magnitude larger than PZT itself are obtained. The metal-ceramic composites are being developed as fish finders, hydrophones, actuators, and transducers with integrated sensing and actuating capabilities. This paper describes the moonie principle, optimization of the moonie design using finite element analysis, and the performance of the device for several different applications.

The two most common type of piezoelectric actuators are the multilayer actuator with internal electrodes and the cantilevered bimorph actuator [']. A new type of composite ceramic actuator is the multilayered multistacked moonie (multi-multi moonie). Normal multilayer actuators produce a large generative force, but only a small displacement. Conversely, bimorphs produce large displacements but the forces are very small. The moonie actuator combines the advantages of both, producing a large displacement as well as a reasonably large generative force.

No abstract