Modeling Bistable Composite Laminates for Piezoelectric Morphing Structures

A sequential modeling effort for bistable composite laminates for piezoelectric morphing structures is presented. Thin unsymmetric carbon fiber composite laminates are examined for use of morphing structures using piezoelectric actuation. When cooling from the elevated cure temperature to room temperature, these unsymmetric composite laminates will deform. These postcure room temperature deformation shapes can be used as morphing structures. Applying a force to these deformed laminates will cause them to snap through to another shape. This bistability arises from the fabrication process of the thin unsymmetric laminates. The snap through force studied here will be controlled by using piezoelectricity. Macrofiber composite (MFC) actuators are used for piezoelectric actuation. In this research, an analytical modeling method is presented to accurately depict the piezoelectric morphing structures. Sequential numerical modeling of the cure process to account for residual stresses and postcured shapes and piezoelectric morphing structure is done to predict the piezoelectric actuated displacements of the thin unsymmetric composite laminates. Analytical and numerical models are compared to experimental methods and results. 1. Introduction Smart material systems are vastly becoming an integral part in engineering applications. One of the phenomena used in smart material systems is piezoelectricity. Working with unsymmetric bistable composites, piezoelectric effects can be implemented to achieve a snap through to the other cylindrical stable shape of the composite. This shape change caused by piezoelectric effects can be coupled with other domains and used as sensor or actuator. The objective of this research was to use piezoelectric effects for actuation. Bistability of the composite laminate is achieved during fabrication. After the cure process, multiple deformation shapes can be observed based on the ply orientation, material, and thickness of the laminate [1]. This deformation is due to the thermal strain gradient between the layers of the laminate and cure shrinkage during the cure process [2]. As an essential part of the smart material morphing system, the cure process and the resulting postcure deformation shapes are heavily investigated. In order to accurately depict piezoelectric morphing structures, the postcure room temperature shapes need to be characterized. This is done by using a Rayleigh-Ritz technique that accounts for the large out-of-plane strains occurring during the cooling of the laminate [3–7]. Piezoelectricity exhibits electromechanic