Nonlinear thermo-mechanical analysis of thermo-plastic composite plates

Thin composite structures are increasingly employed in aerospace applications, including deployable appendages such as solar panels and booms, where low mass and high stiffness are essential. Fiber-reinforced polymer composites are processed at elevated temperatures, generating thermal residual stresses upon cooling. When manufacturing imperfections introduce ply-level thickness variations, the resulting stress distribution becomes unbalanced, causing out-of-plane warping that can compromise structural integrity and dimensional precision. This work presents a geometrically nonlinear thermo-mechanical finite element model based on the Carrera Unified Formulation (CUF). The framework adopts a class of plate elements in which the through-thickness direction is discretized by an independent one-dimensional finite element mesh, enabling the accurate representation of variable-thickness geometries without remeshing the in-plane domain. The kinematic field is governed by generalized expansion functions, allowing arbitrary approximation orders across the thickness. The thermo-mechanical coupling is addressed within a fully nonlinear framework using Green–Lagrange strain measures. A coupled tangent stiffness matrix is derived, incorporating both the material and geometric contributions to the mechanical response, as well as the thermo-mechanical coupling terms arising from temperature-dependent thermal stress resultants. The governing equations are solved iteratively via a Newton–Raphson scheme, ensuring quadratic convergence in the vicinity of the solution. The model is validated against experimental and numerical reference data for symmetric and unsymmetric carbon fiber laminates under thermal loading. The influence of thickness imperfections on warping amplitudes and residual stress distributions is investigated, demonstrating the sensitivity of the structural response to manufacturing variability. The proposed approach provides an accurate and computationally efficient tool for the analysis and design of thin composite components subjected to combined thermal and mechanical loads.