Aero-thermo-elastic behaviour of variable stiffness composite laminates and sandwich panels with temperature-dependent material properties

This work is focused on the evaluation of the impact of temperature-dependent material properties on the linear aero-thermo-elastic flutter and buckling stability of variable stiffness composite laminates and sandwich panels with curvilinear fibres under supersonic airflow and thermal loads. To ensure a proper structural modelling, an assessment of Equivalent Single Layer and Layerwise models is also provided, involving the First- and Third-order Shear Deformation Theories as well as further refined theories based on high-order Lagrange z-expansions with thickness stretching. Numerical applications are centred on graphite-epoxy composite laminates and PVC foam core sandwich panels, with either unidirectional or curvilinear fibres, considering simply supported and clamped boundary conditions. It is concluded that temperature-dependent material properties can substantially decrease both critical buckling temperatures and flutter boundaries, depending on the fibre orientations, thermal expansion coefficients and boundary conditions. In particular, the temperature-dependency of the core material plays a major role on the aero-thermo-elastic stability of sandwich panels. Ultimately, the models accuracy assessment reveals that high-order theories are necessary to attain highly accurate flutter estimations for temperatures close to the critical buckling temperature, especially when considering curvilinear fibres and temperature-dependent material properties.