Active aero-visco-elastic flutter control and layerwise modelling of supersonic smart sandwich panels with variable stiffness composites

This work focuses on the active aero-visco-elastic flutter control of smart sandwich panels under supersonic airflow by combining viscoelastic materials with variable stiffness composites and surface bonded piezoelectric sensor/actuator layers, exploring variable-order layerwise models based on shear deformation theories. Numerical applications of smart sandwich panels encompass either viscoelastic or purely elastic core, along with elastic layers of composite laminates, using unidirectional or curvilinear fibres, considering thin and moderately thick panels, as well as narrow and wide cores. Proportional and derivative feedback control laws are implemented resorting to the electric potential differences across the piezoelectric layers. Comparing the control laws, it is concluded that the proportional control has a significant stabilizing effect on the occurrence of coupled-mode flutter, as in sandwich panels with purely elastic core, unlike the derivative control. However, when dealing with single mode flutter, as in viscoelastic sandwich panels described with complex modulus approach, the derivative control outperforms the proportional control in improving the flutter resistance. Ultimately, the accuracy assessment of the models predictive capabilities in active flutter control analysis reveals that although the layerwise first-order model ensures a good compromise between numerical accuracy and computational efficiency, especially in thin sandwich panels, high-order models are necessary for moderately thick panels.