Nonlinear thermo-mechanical stability of eccentrically stiffened functionally graded material sandwich doubly curved shallow shells with general sigmoid law and power law according to third-order shear deformation theory

In this paper, the nonlinear analysis of stability of functionally graded material(FGM) sandwich doubly curved shallow shells is studied under thermo-mechanical loads with material properties obeying the general sigmoid law and power law of four material models. Shells are reinforced by the FGM stiffeners and rest on elastic foundations.Theoretical formulations are derived by the third-order shear deformation theory(TSDT)with the von K′arm′an-type nonlinearity taking into account the initial geometrical imperfection and smeared stiffener technique. The explicit expressions for determining the critical buckling load and the post-buckling mechanical and thermal load-deflection curves are obtained by the Galerkin method. Two iterative algorithms are presented. The effects of the stiffeners, the thermal element, the distribution law of material, the initial imperfection, the foundation, and the geometrical parameters on buckling and post-buckling of shells are investigated.