Aerothermodynamical loads cause buckling and plastic deformation of thin-walled structures under boundary conditions, which restrict the structural movement. We present the numerical computation of a loosely coupled fluid-structure interaction for thermal buckling. The task of the research is to provide a mechanical model which incorporates the correct material behaviour and is suitable for thermal panel buckling. For this, an elasto-viscoplastic material model with non-linear isotropic hardening is used, which also includes nonlinearly temperature dependent material parameters. This material model is implemented into a user material in Abaqus FEA. The structural computation is coupled with the fluid computation within the fluid-structure interaction code ifls from the TU Braunschweig. For the fluid solver TAU from the DLR is used.

Experiments have shown that a high-enthalpy flow field might lead under certain mechanical constraints to buckling effects and plastic deformation. The panel buckling into the flow changes the flow field causing locally increased heating which in turn affects the panel deformation. The temperature increase due to aerothermal heating in the hypersonic flow causes the metallic panel to buckle into the flow. To investigate these phenomena numerically, a thermomechanical simulation of a fluid-structure interaction (FSI) model for thermal buckling is presented. The FSI simulation is set up in a staggered scheme and split into a thermal solid, a mechanical solid and a fluid computation. The structural solver Abaqus and the fluid solver TAU from the German Aerospace Center (DLR) are coupled within the FSI code ifls developed at the Institute of Aircraft Design and Lightweight Structures (IFL) at TU Braunschweig. The FSI setup focuses on the choice of an equilibrium iteration method, the time integration and the data transfer between grids. To model the complex material behaviour of the structure, a viscoplastic material model with linear isotropic hardening and thermal expansion including material parameters, which are nonlinearly dependent on temperature, is used.

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