The use of piezoelectric materials for power harvesting has gained significant interest over the past few years. The majority of research on this subject has sought to quantify the amount of energy generated in power harvesting applications, or to develop methods of improving the amount of energy generated. Usually, a monolithic PZT material with a traditional electrode pattern and poled through its thickness is used in power harvesting research projects. In recent years, however, several companies and research institutions have begun to develop and market a broad range of piezoelectric composite sensor/actuator packages, each conceived for specific operational advantages and characteristics. Commonly, these devices are employed in control and vibration suppression applications, and their potential for use in power harvesting systems remains largely unknown. Two frequently implemented design techniques for improving the performance of such actuators are the use of interdigitated electrodes and piezofibers. This paper seeks to experimentally quantify the differences in power harvesting application performance between several of these new actuators and to identify the reasons for their relative performance characteristics. A special focus on the structural and compositional differences between each actuator is incorporated in the discussion of the effectiveness of each actuator as power harvesting devices.
While exhibiting powerful characteristics, monolithic piezoelectric sensors and actuators suffer from many drawbacks due to inherent material properties and implementation issues. As a result of their stiff structure and primary operating principle, monolithic piezoelectric wafers perform poorly in a variety of important engineering applications. Piezoelectric Fiber Composites (PFCs) offer one possible solution to these limitations. Mechanically flexible and functioning on the basis of the d33 effect, these actuators enable and improve many piezoelectric applications. The NASA-Langley Research Center recently developed the Macro-Fiber Composite (MFC) actuator to address several shortcomings in the operational characteristics of competing PFC packages. While the construction of this actuator results in many advantages over comparable PFCs, potential exists for improvement in the design of the MFC. Thus, the single-crystal MFC is proposed. Single-crystal PMN, a specific piezoceramic compound, comprises the piezoceramic fibers of the proposed device, contributing larger piezoelectric coupling, higher bandwidth and higher stiffness to the MFC configuration. Development of this new actuator necessitates extensive characterization of its electromechanical properties. This paper describes the development and computational results of a short-circuit stiffness model that produces the four independent mechanical properties which describe the single-crystal MFC. Modeling results are compared to those of the standard MFC.