Research On Mechanical-electric Behaviors Of Piezoelectric Composites

Piezoelectric fiber composites have wide application in engineering. In the multi-phase material system, the non-continuity in material properties may lead to high stress concentrations both at the interface and in the matrix, resulting in the separation of fibers from the matrix, and the final failure of the composite structure. Thus, it is of theoretical and practical importance to study the electro-elastic fields near the fibers in piezoelectric composites.In the present work we propose a straightforward and concise approach to analyze the electro-elastic fields near N interacting piezoelectric fibers based on complex variable theory. Below are the main contents of the work: following the brief introduction given in Chapter 1, key equations to be used in the work are outlined in Chapter 2. Chapters 3-5 are the main contributions of this dissertation, and they are summarized in detail, respectively, as follows:In Chapter 3, studied is an anti-plane problem for the interaction between N randomly-distributed cylindrical fibers in a piezoelectric matrix under anti-plane shear stress and in-plane electric field at infinity. The fibers are assumed to piezoelectric and be perfectly bounded to the matrix. Based on complex variable method, approximate solutions for complex potentials and elastroelastic fields are derived, and then numerical examples are presented to discuss the influences of fiber array, fiber size and fiber properties on couple fields in the matrix.Chapter 4 is an extension of the work in Chapter 3. In this Chapter, all the fibers are assumed to be coated, and then electro-elastic fields in an infinite matrix with N coating piezoelectric fibers are derived. Numerical results and discussions are also made to explore the influence of coating thickness, array type of fibers and material properties on interface stresses, stress concentrations and electric displacements in the matrix.In Chapter 5, addressed is a plane problem for the interaction between N randomly-distributed cylindrical fibers in an infinite elastic matrix subjected to in-plane mechanical loading. According to Muskhelishvili theory, stress distribution near the fibers is derived, and then numerical examples are presented to discuss the influences of fiber array, fiber size, fiber properties and applied electric fields along the fiber direction as well on couple fields in the matrix.Finally, this work is concluded, and future works on the topic are proposed in Chapter 6.