|Ph.D Thesis||Department of Aerospace Engineering|
|Supervisor:||Assoc. Prof. Abramovich Haim|
|Full Thesis text|
The present research investigates the structural integrity of smart structures based on extension and shear type piezoelectric patches. The static and dynamic behavior of the extension type piezoelectric mechanism were widely investigated and presented in many studies. On the other hand, investigations on the static and dynamic behaviour of shear type piezoelectric mechanism, as being reflected in profesional publications, were limited and not always clear. Moreover, the key issue associated with the structural integrity of smart structures used in the aerospace industry is their behaviour under applied cyclic loading. Therefore, to evaluate and understand the integrity of smart structures, investigations must include active sensors/actuators embedded or bonded as a part of a smart structure, and loaded under combined electro-mechanical cyclic loads, the same way they are used in real-life applications. Surveying the published literature, a little research has been performed in the field of structural integrity of smart structures; A small number experimental study were published, and almost no work has been carried out in combined mechanical high cyclic E/M loading of the structure while actuating the PZT, a phenomenon called high cyclic electro-mechanical loading.
It is the aim of the present research to investigate the integrity of smart structures through a comprehensive experimental study, thus sought to determine the functionality of piezoceramic actuators/sensors embedded in or bonded on a laminated composite beam. The beams were undergoing combined high cyclic electromechanical loadings under fully reversed, symmetric and non-symmetric tension-compression loading and pure bending moment conditions. The main impact of the present research constitute the ability to predict the structural integrity of a given smart structure as a function of its life cycle, yielding a balanced design with enhanced survivability. This enables the integration of piezoelectric patches with a larger confidence in their applications.
Another important goal of the present research is to extend the existent knowledge of the shear type piezoelectric mechanism. For this purpose, analytical and numerical models were developed for two common structure types, beams and plates. These models enable a better understanding of the shear type piezoelectric behavior. The last part of this research, deals with the evaluation of the piezoelectric analysis and computational capabilities of existing commercial finite element codes, ANSYS and ABAQUS. The analytical models developed earlier are used as benchmark models to investigate the relevant finite elements models existing in the above two commercial finite elements codes.