Response Of The Ferroelectric Thin Film Under Infrared Radiation And The Buckling Analysis Of The Electrode Delamination

The ferroelectric-thin-film pixel is an essential element in uncooled infrared focal plane array (UIRFPA) of an infrared detector. It is a multilayered structure. Its middle ply is a ferroelectric thin film, and the upper and lower surfaces are covered with metallic electrodes. In addition, some protective coatings are probably fabricated. Nowadays "the smaller the better" is becoming a principle for the design of the ferroelectric pixel. The requirements of photonic sensitivity to the infrared radiation are also increasing rapidly for military and civil uses. Therefore, the thermo-electro-mechanical problems involved in the UIRFPA design are worth studying. The works of pioneer researchers on the thermal conduction in multilayered structures or functionally graded materials are only confined in the transient or stable thermal conduction problems, such as the functionally graded coating in the heat-resistant structures. Some authors stimulated or measured the output responses of ferroelectric-thin-film elements using finite element codes or experimental methods. But there are only few works for analyzing the relationship between the thermal conduction and the output signals of the intelligent devices.Some authors studied the buckling problems of delaminates of laminated structures or laminated composite materials using finite element analysis and traditional beam/plate theories. In these works, the delaminating model might be oversimplified. Some authors studied the buckling problems in isotropic materials under the plane strain mode using finite deformation theory, such as Wang Wen-Xue , Loboda and Mityukova , Chiu and Erdogan etc. Madenci and Westmann analyzed the local buckling problems of penny-shaped delaminate in the mid-surface of the thin plate subjected to symmetric or anti-symmetric remote compression. Madenci and Westmann analyzed the propagation problem of local delaminate in the laminated structure under compressive load. Madenci et al analyzed the buckling problem of penny-shaped delaminate in the interface of coating and substrate under biaxial loading. Balkan and Madenci analyzed the same problem but under thermal loading. Sburlati, Madenci and Guven analyzed the same problem but the thickness of the substrate was finite. These analyses only considered the delaminating in isotropic materials. But hardly can be found the works analyzing the buckling problems of delaminates in intelligent structures and materials taking account of the influence of the coupling effects.In many works, buckling of delaminating in structures under bending was analyzed by using the finite element method. It was only found that Kardomateas analyzed this problem using traditional beam theory. The solution was expressed in the form of elliptic integrals, and compared with experimental data. But hardly can be found the works for analyzing the buckling of delaminates in the smart structures and materials employing finite deformation theory and bias electric field theory under bending. Analyses of these problems are important and benefit for studying the damage problems in the intelligent devices.In this work, the output responses of a smart structure and the related delaminate buckling problems will be analyzed, including the follows:In chapter 1 the summary of the related works will be given. Heat conduction and buckling of delaminates in structures are introduced briefly.In chapter 2, heat conduction and the output response of voltage of a ferroelectric thin film pixel are analyzed. The solution is compared with experimental evidence.In chapter 3, buckling of a through-the-width delaminate in the interface between the infinitely deep ferroelectric substrate and the metallic coating subjected to remote uniform compression is analyzed. The finite deformation theory and bias electric field theory are employed. Using Fourier integral transformation and the corresponding boundary conditions, a set of singular integral equations is obtained. Using Muskhelishvili theory and Gauss-Chebyshev polynomial, these singular integral equations are discretized to a set of homogeneous linear algebraic equations, and the solution can be obtained. The code of the problem is written in the Mathematica. In the example, the critical remote strain and the buckling configuration for different length-to-thickness ratios of delaminating are given. The effect of electric-mechanical coupling is included.In chapter 4, the same problem as that in chapter 3 is analyzed. But the ferroelectric substrate has a finite thickness with the lower surface covered by metallic electrode. In other words, the model is a ferroelectric thin film with its upper and lower surfaces covered by metallic electrodes. The method employed for analyzing is more or less the same as in chapter 3. The case of electric field in the ferroelectric thin film is also considered. In order to verify this analytical solution, a finite element solution is obtained in help of PATRAN and NASTRAN codes. It is found that both solutions are in a good agreement. In chapter 5, the same problem as that in chapter 3 is analyzed. But the model is subjected to a remote pure bending. In the procedure of solution, the model is divided into several layers. The continuity conditions are employed in the interfaces of these layers. The critical bending moment, curvature and the configuration of buckling for different ratios of the delaminate length and the thickness of the electrode are given. Solution of the finite element analysis in virtue of PATRAN and NASTRAN codes is obtained to verify the analytical solution.The conclusion and prediction of research in this area are given in chapter 6.