A dynamic stiffness improvement method for thin plate structures with laminated/embedded shape memory alloy actuators

Cantilever thin plates are commonly used as external structures in different aircraft, e.g., missile fins and aircraft rudders, which have important functions such as adjusting attitude and providing lift. However, when the aircraft is flying at a high speed, the elastic modulus of the material will be significantly reduced due to the thermal effect. This will decrease the dynamic stiffness of the aircraft and thereby lead to flutter and other serious problems. This study aims to investigate the dynamic stiffness improvement method for thin-walled structures at high temperatures with shape memory alloy (SMA) actuators. A theoretical model of an SMA laminated aluminum thin plate is established first. Then an improved stiffness enhancement method with distributed SMA actuators is proposed. The configuration of the actuator is designed and verified by the finite element method. A frequency prediction model of the thin plate structure is established with Back Propagation (BP) neural network and optimal placement of the actuator is achieved based on a genetic algorithm. The validity of the proposed method is verified through both numerical simulations and high-temperature frequency sweep experiments. The results show that the stiffness of the thin plate structure can be significantly improved by the SMA actuators. Specifically, the first-order bending frequency and first-order torsional frequency of the structure can be improved by nearly 10% at 200 °C.