The paper models the effects of dynamic coupling between a structure and an electrical network through the piezoelectric effect. The coupled equations of motion of an arbitrary elastic structure with piezoelectric elements and passive electronics are derived. State space models are developed for three important cases: direct voltage driven electrodes, direct charge driven electrodes, and an indirect drive case where the piezoelec tric electrodes are connected to an arbitrary electrical circuit with embedded voltage and current sources. The equations are applied to the case of a cantilevered beam with surface mounted piezoceramics and indirect voltage and current drive. The theoretical derivations are validated experimentally on an actively controlled cantilevered beam test article with indirect voltage drive.
Piezoelectric Fiber Composites were previously introduced as an alternative to monolithic piezoceramic wafers for structural actuation applications. This manuscript was an investigation into the improvement of piezoelectric fiber composite performance through a nonconventional electroding scheme. Two microelectromechanical models were developed that predict the composite properties. These models were used to examine the trends of composite properties versus fiber volume fraction for various constituent materials. Several etched electrode PZT fiber composites, with fiber volume fractions ranging from 7% to 58%, were manufactured and tested. Experimental measurements showed excellent agreement with both the trends and magnitude of model predicted values. The maximum fiber volume fraction composites demonstrated a capacitance (E3 /Eo) of 550, piezoelectric free strain constants (d33 and d31) of 150 pm/V and-70 pm/V, and piezoelectric clamped stress (e33) of 5 C/m2, showing a substantial improvement over previous piezoelectric fiber composites with uniform electrodes. Maximum strain values of 1700 ppm were measured, indicating higher in-plane actuation than monolithic piezoceramics.
An investigation was made into the field of planar structural actuation with anisotropic active materials. The mechanisms for creating anisotropic actuators were discussed, and the impact of anisotropy was shown at the individual lamina level and at the laminated structure level. Models for laminated structures were developed using an augmented Classical Laminated Plate Theory incorporating induced stress terms to accommodate anisotropic actuator materials. A twistextension coupled laminate was used to exemplify how twist can be directly induced into isotropic host structures using anisotropic actuation. Four anisotropic actuators with different material anisotropies were compared using this example. Finally, a laminate incorporating piezoelectric fiber composite actuators was manufactured and tested. Excellent agreement was found between the predicted and experimental response.
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