MS Thesis Presentation by Kyle G. Webber
Thursday, May 5, 2005

(Dr. Christopher Lynch, Chair)

"Characterization of Actuation and Fatigue Properties of Piezoelectric Composite Actuators "

Abstract

E poxy c omposite l am i nated p iezoelectric s tress- e nhanced actuators (ECLIPSE) have been developed for potential applications by the United States Air Force and others. This class of actuators offers several advantages over other unimorph actuators such as lighter weight, design flexibility, and short production time. Anisotropic differential thermal expansion is utilized in the design of the actuators to achieve large out-of-plane curvature and place the brittle piezoelectric ceramic in residual compression. The numerous composite material choices and configurations can be used to control characteristics of the actuator such as radius of curvature and force output.

ECLIPSE actuators were characterized during this study. They were made from layers of Kevlar 49/epoxy composite and a lead zirconate titanate ceramic (PZT) plate. All ECLIPSE actuators tested were built with a PZT plate with the same dimensions and material, but had different layup configurations. By changing the stacking order of the composite and PZT material, characteristics of the actuator were altered. The performance of each ECLIPSE actuator was compared. The maximum achievable displacement of each actuator was measured by cyclically applying an electric field at low frequency between zero and the maximum electric field allowable for the piezoelectric material. The frequency was also increased to a resonance condition to characterize the fatigue behavior of these actuators. In addition, the force output of various actuators was measured with a four-point bending apparatus. The experimental data was compared to a classical lamination theory model and an extended classical lamination theory model. These models were used to predict actuator behavior as well as to calculate the stress and strain distribution through the thickness of the actuator.

Many key points were understood more fully after this investigation. The manufacturing of ECLIPSE actuators was refined to produce very reliable and repeatable results. The manufacturing can now be done with a minimum of space required using much more inexpensive equipment. The stacking order of the actuators has been tested and the effect of adding or reducing the number of composite layers on the displacement and the force production is more fully understood. In addition, the fatigue behavior has been shown.