In this paper the finite layer methods are extendedly used to the coupled thermo-elastic analysis of simply-supported, functionally graded (FG) doubly curved (DC) shells with temperature-dependent material properties. The specified temperature conditions are prescribed on the top and bottom surfaces of the shell. The material properties of the shell are assumed to obey the power-law distributions through the thickness direction according to the volume fractions of the constituents, and the effective material properties are estimated using the Mori- Tanaka model. Comparisons of the solutions obtained using the finite DC layer (FDCL) methods with the temperature-dependent and temperature-independent material properties are carried out.
Since the concept of functionally graded materials was proposed for use in thermal barrier materials at the National Aerospace Laboratory of Japan (Koizumi, 1992, 1997), the development of these FG materials has progressed rapidly, and their application in various advanced industries has become increasingly popular. These FG materials are composed of two- or more-phases of dissimilar materials in such a manner that the material properties vary gradually and continuously in one or more directions. The FG materials have considerable design flexibility, for example engineers can design the most appropriate material properties, according to a variety of structural performance requirements, by adjusting the spatial distributions of the volume fractions of the constituents. Due to the continuous spatial distribution of the material properties of the FG material, it can also be used to form a variety of single-layered, sandwiched and multi-layered FG structures to prevent delamination failure, which often occurs at the interface between adjacent layers of conventional laminated composite structures, in which the material properties suddenly change.
Since the above-mentioned FG structures are intended for use in severe thermal environments, the coupled thermo-elastic analysis of these structures has attracted considerable attention in order to accurately estimate the thermo-elastic stress and deformation induced in them. Most of the articles examining the coupled thermo-mechanical behavior of FG plates and shells available in the literature did not take account of the effects of temperature-dependent (TD) material properties. In recent years, the effects of TD material properties on the various structural responses of the FG plates and shells have attracted considerable attention, with the aim of finding the difference between the results with the TD and temperature-independent (TI) material properties. Based on Reddy's refined higher-order shear deformation theory (HSDT) (Reddy, 1984) coupled with the von K'arm'an geometrical nonlinearity (VKGN) term, Shen (2002, 2007) investigated the nonlinear thermal bending responses of FG plates subjected to the thermo-mechanical loads, in which TD material properties were considered, and this approach was also extended to the similar analysis of FG cylindrical panels resting on elastic foundations by Shen and Wang (2015). Shen (2004) investigated the thermal buckling behavior of FG cylindrical shells with TD properties, and Farid et al. (2010) examined the 3D free vibration behavior of FG curved panels resting on a Pasternak-type foundation using a hybrid semi-analytic differential quadrature method, in which the TD properties was considered, while the current issue seems not to be carried out in the literature.
