Nonlinear thermo-elastic analysis of laminated composite structures for spacecraft

Laminated composite structures still attract the interest of the space industry for several reasons, including lightweight, tunable anisotropy allowing for tailored thermo-elastic stability and integration of components through one-peace manufacturing. Applications of fiber-reinforced materials include strap elements, booms, deployable structures and solar arrays, antennas, and payload shrouds. An example of the successful use of laminates is the NASA Space Launch System (SLS), which demonstrated the effective use of these materials in the production of payload faring, EUS, and lightweight joints to join large rocket structures. Although attractive, composite structures still present challenges compared to conventional materials, especially in extreme conditions experienced during launch and in the outer space environment. Thermal cycling resulting from Earth orbit, for example, significantly impacts fatigue behaviour and the mechanical performance of composite parts. Furthermore, due to the presence of extreme thermal loads, it became mandatory to accurately describe the large displacements due to thermal deformations in the case of thin laminates, as well as complex 3D distortions and nonlinear buckling. Addressing these challenges necessitates the development of advanced models, often not readily available in industrial practice. This research aims to describe the complex behaviour of composite structures under thermal load, offering insights into the design of space-worthy materials and components. The problem is formulated within the Carrera Unified Formulation framework, which allows a compact and hierarchical implementation of high-order structural theories. The thermal problem is schematized using a decoupled approach, where the thermal profile is assumed to be known and treated as an external load. The nonlinear equations are solved by the Finite Element Method using the Newton-Raphson algorithm. Comparative analyses between linearized and nonlinear approaches highlight the importance of nonlinear analysis of the thermal effect for these structures. The accuracy of higher-order theories and their importance in studying high-precision application structures is also assessed.