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This paper discusses the mechanical characteristics of laminated piezoelectric actuators that are manufactured at an elevated temperature, to cure the adhesive bonding the layers together, and then cooled to a service temperature. The actuators are of the unimorph-type, which are composed of a layer or layers of passive materials and a layer of piezoelectric material. THUNDER (thin layer unimorph ferroelectric driver and sensor)-type actuators, which consist of layers of metal, adhesive, and piezoelectric material, are studied and investigated in detail to understand the thermal effects due to the elevated manufacturing temperature. Owing to the large out-of-plane deformations of THUNDER-type actuators as a result of cooling to the service temperature, inclusion of geometric nonlinearities in the kinematic relations is taken into consideration for prediction of the thermally induced deformations and residual stresses. The deformations and residual stresses are predicted by using a 23-term Rayleigh–Ritz model and a finite-element model using ABAQUS. The thermally induced deformations result in actuator shapes which can be dome-like or near-cylindrical. Which shapes actually occur depends on the geometry of the actuator. Actuation responses of the actuators caused by a quasi-static electric field applied to the piezoelectric layer are also studied with the Rayleigh–Ritz approach. It is shown that geometric nonlinearities play an important role in the actuation responses, and these nonlinearities can be controlled by the choice of actuator geometry.

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Presented are the predicted manufactured shapes and actuated shape changes of metal-based THUNDER TM -like actuators and fiber-reinforced-polymer-based LIPCA-C1and LIPCA-C2-like actuators. As these actuators, which are laminated in nature, are manufactured flat at an elevated temperature and then cooled for use, they deform out of plane as they cool, resulting in residual curvatures. The development of the residual curvatures are predicted with a 23-term Rayleigh-Ritz model based on energy principles. Because of the large out-of-plane deformations due to cooling, geometrically nonlinear effects, in the sense of von Ka´rma´n, are included. Actuated curvatures due to activation of the piezoceramic material are also predicted. The behaviors of plate-and beam-like actuator geometries over a range of sidelength-to-thickness ratios are investigated. Finite element results for selected geometries are presented for comparison with the 23-term model. The results show that geometrically nonlinear effects are quite strong for THUNDER and LIPCA-C2 plate-like actuators, resulting in the potential for more than one cooled shape for THUNDER actuators and of a sudden change in the actuated shape, referred to here as snap-through, for LIPCA-C2 actuators. For the LIPCA-C1 actuators, and the beam-like geometries of the other two actuators, geometrically nonlinear effects are not as strong. Residual stress predictions within the cooled and activated actuators are also presented. Though the actuators considered are specific in design, the results can be interpreted more generally and point to the fact that a wide range of behaviors can be expected from geometrically nonlinear effects interacting with variations in materials (i.e., metals vs. fiber-reinforced materials) and geometry (i.e., platelike vs. beam-like and sidelength-to-thickness ratio).