Investigation of the stability of clamped functionally graded cylindrical shells in elastic medium under the lateral pressure

Functionally graded materials (FGM) are advanced material types in which the structural properties of the material change continuously or gradually according to the position. It can be used in almost all areas of structural engineering, and is a frequently preferred material form in heavy and light industry. Consequently, the accurate determination of their structural characteristics and mechanical behavior is of critical importance. In the thesis study, stability analysis of cylindrical shells made of Functionally Graded (FG) materials in an elastic medium under lateral external pressure effect was carried out within the framework of of Donnell type shell theory. After mathematically modeling the FGMs and external pressure load, the basic relations belonging to the cylindrical shell structural shape were established for the geometric linear case. Then, stability and deformation compatibility equations of FG cylindrical shells on Pasternak foundation were obtained based on Kirchhoff-Love theory (KLT). After determining the approximation functions for the clamped boundary conditions, the Galerkin procedure was applied to solve the basic partial differential equations. From the algebraic equations obtained after integration, the analytical expression for the critical external lateral pressure of functionally graded cylindrical shells under clamped boundary conditions on the Winkler elastic foundation is obtained. When the elastic medium effect is not taken into account, the analytical expression for the critical lateral external pressure of functionally graded cylindrical shells is obtained as a special case. The expressions in question will be minimized according to the buckling mode and the minimum values of critical external lateral pressure with and without elastic media are obtained numerically. Extensive numerical analyses, interpretations and generalizations are carried out for the minimum values of critical external lateral pressure by considering different volume fractions, Pasternak-Winkler elastic foundation coefficient and geometric characteristics of the cylindrical shell.