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.

Composites with transversely oriented piezoelectric fibers in an epoxy matrix are developed as a means for large scale structural actuation and sensin . These active composites address the need for orthotropic actua on capability in a form that reduces many of the problems inherent in current monolithic ceramic actuators. Techniques are developed to predict effective material properties of the piezoelectric fiber composite for in-plane structural loading problems. This is done through advancement of several coupled electromechanical micromodels. Manufacturing of conformable piezoelectric fiber composites is described. Experimental data from the manufactured specimens show reasonable a s in stiffness and piezoelectric effects, and of anisotropy than that predicted by models.TRUCTURAL actuation and sensing is a key technology in the development of controlled structures. More recently, active materials have replaced the traditional means for actuation and sensing, and have increased the performance levels possible. Applications of materials including shape memory alloys, magnetostrictives, electrostrictives, and piezoelectrics have given investigators a new means for controlled structures technology. Piezoelectrics are perhaps the most widely used in this capacity because their high stiffness gives them high actuation authority, and they are easily controlled by an applied voltage. They also have high bandwidth and their active properties are relatively easy to model. Currently, piezoelectrics have been used for vibration suppression of structures as either surface bonded114 embedded5.6 actuators and sensors. Coupled electro-mechanical models of beam and plate structures have been developed and applied to the problems of piezoelectric passive damping7 and selfsensing of actuation of piezoelectric active structures*. Finally, experimental results in closed-loop control of structural vibration6J-4, aeroelastic response9.10, and acoustic bansmission of plates and shellsllJ2 have demonstrated the feasibility of active structural control using piezoelectrics.Despite the past successes, these studies have highlighted the difficulties associated with the present piezoelectric technology. These difficulties can be divided into two types of problems: those inherent in the piezoelectric, and those associated with the scalingt Assistant Professor,

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