Nonlinear thermal stresses analysis and post-buckling of rectangular composite laminates using high-order plate finite elements

The present paper investigates the geometrically nonlinear thermo-elastic response of composite plates undergoing large rotations/displacements, with a focus on post-buckling and 3D thermal stresses. The governing equations are derived from the Principle of Virtual Displacement (PVD), whereby the full Green-Lagrange strain tensor is adopted in a total Lagrangian framework. The thermal load is described using a decoupled approach, and constant thermal distribution is considered. The employed plate elements are developed through the Carrera Unified Formulation (CUF) and their formal expression is independent of the theory approximation order. Thus, low-order equivalent-single-layer (ESL) to high-order layer-wise (LW) models can be implemented with ease. The nonlinear problem is solved through the Newton-Raphson procedure combined with the arc-length constraint. Plates with different geometries and materials are analyzed, and linear and nonlinear analyses are compared. From the results, it is shown that LW models are needed to describe the 3D thermal stresses in nonlinear equilibrium states, whereas ESL finite elements are enough to describe the global deformation state.