Piezoelectric structures are used in a variety of applications where instant response, high energy conversion efficiency
and accurate control are required. However, in the actuation domain they present an important drawback, which is the
small displacement capacity. In the present work non-linear mechanics and more specifically snap-through buckling
are used to transform a traditional bimorph structure with two piezoelectric layers and an aluminum substrate into a
non-linear high displacement actuator with increased combination of force/displacement output. Large displacements
are attained with the transition of the structure from one equilibrium position to another. A closed form analytical
solution for the snap-through behavior of piezoelectric/composite beams is presented. The effect of piezoelectric
actuation is introduced in this model through equivalent bending moments produced through the bimorph setting of
the piezoelectric actuator. Classical Laminated Plate Theory (CLPT) is used for the elaboration of an equivalent single
layer structure that takes into account the influence on the stiffness of the structure due to the piezoelectric layers.
During the development the importance of boundary conditions has been revealed and thus it has been modeled too.
Results from finite element analysis as well as the actuators' construction and the experimental setup and subsequent
results are presented.
In the present work, the non-linear analysis of smart beams and plates is performed, using FE techniques. A coupled constitutive formulation between thermal, electrical and mechanical fields is presented incorporating non-linearity due to large displacements. An 8-node plate element was implemented in combination with a discrete layer approximation (LW) for the through the thickness representation of the structure. The issues of the critical buckling load under different electrical conditions as well as thermal and electrical loading are also presented. Experimental results contribute in order to verify the numerical analysis results.
Non-linear smart actuators have attracted lately the interest of many researchers. It is well known that linear smart actuators have been used in a vast number of applications in different disciplines. However, most of the times a trade off between displacement and force must take place in order to increase their operational envelope. Taking into account this, it is not strange that research is headed towards non-linear mechanics in order to increase displacement, as well as force actuation in smart actuators. In the present work, issues related with the non-linear response of smart beams as well as snap-through performance are investigated. Beams with aluminum cores are equipped with continuous piezoelectric
layers that cover only a certain part of the structure. A number of symmetrical and asymmetrical actuators have been realized with different core lengths and thus the amount of active material over the whole length of the actuator varies. These actuators were tested in order to evaluate their critical buckling load as well as their snap-through performance. The snap-through displacement was examined with respect to the post-buckling compression of the actuators for all the configurations and the difference between symmetrical and asymmetrical actuators raises a number of issues concerning the design of such actuators.
Due to the extended application of piezoelectrics into a number of high performance structures, the necessity for accurate analysis of their behavior is of critical importance. In this work the dynamic analysis of a composite plate incorporating piezoelectric layers is presented. A 4-node plate finite element is developed. Discrete layer kinematic assumptions in combination with a thermal-electrical-mechanical coupled formulation takes place. This formulation enables the investigation of the response of a structure under the influence of different thermal and electrical conditions. Additionally, in order to investigate whether the kinematics assumptions implemented here are capable of capturing with accuracy the dynamic performance of both thin and thick structures, plates of different thicknesses are investigated.