Nonlinear thermo-mechanical buckling and post-buckling of multilayer FGM cylindrical shell reinforced by spiral stiffeners surrounded by elastic foundation subjected to torsional loads

The nonlinear buckling and postbuckling behavior of Multilayer functionally graded (FGM) cylindrical shells reinforced by ring, stringer and/or spiral stiffeners made of isotropic material under torsional loads and thermal load is proposed by an analytical approach. The thin shell is composed of three layers: isotropic layer - FGM layer - isotropic layer and surrounded by Pasternark type elastic foundation. The governing equations are based on the Donnell shell theory with von Kármán-Donnell-type geometrical nonlinearity, combining the improvability of Lekhnitskii's smeared stiffeners technique for spiral stiffeners. The effects of mechanical and thermal loads are considered in this paper. The number of spiral stiffeners, angle stiffeners, temperature change, and volume fraction index of shells, foundation and stiffeners are numerically investigated. A very large effect of spiral stiffeners on buckling behavior of shell in comparison with orthogonal stiffeners is approved in numerical results.