PLATE AND MICRO-SCALE STRUCTURES: ANALYSIS AND EXPERIMENTS
Vechery, Mary Elizabeth
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Within this work, plate and micro-scale structures are studied. Methodologies are developed to analyze the laminate stiffness, residual forces, moments and stresses, and deformations in these thin composite laminate structures to facilitate better designs, enable device characterization, and enhance device performance. Specific devices studied in this work are cantilevered and clamped-clamped PZT resonators of various lengths, widths, and laminate thicknesses. In order to better understand the behavior of these devices, analytical and experimental methods have been developed. The analytical methods are based on linear and nonlinear beam and plate models, with reduced-order models developed to study dynamic behavior. Parameter identification techniques have been applied to characterize residual stress induced deformation of micro-scale structures. Extensive data has been collected through careful experiments to aid the development of identification techniques and to determine device deflections and individual device residual stress values. An analytical model has been developed to describe the behavior of thin composite laminate plate-like structures. Since an exact solution for plate mode shapes does not exist for all boundary conditions, appropriate combinations of orthogonal functions are assumed for the mode shapes of a plate with all edges simply supported or all edges clamped. These functions make the development of reduced-order models possible for these boundary conditions. In addition, these plate-like structures are asymmetric isotropic laminates. A procedure was applied to calculate the stiffness, forces and moments for a laminate comprised of multiple isotropic layers regardless of symmetry. Parametric identification techniques were developed to identify system parameters and to characterize residual stress induced deformation in plate and micro-scale structures. These techniques are based on linear and nonlinear beam models and reduced-order methodologies, and they enable the first characterization of residual stress in PZT micro scale devices post-fabrication and release processing. The obtained results indicate that post-release residual stress measurements in devices can be considerably different from the corresponding measurements made before release.