Characteristics of smart composite wing with SMA actuators and optical fiber sensors

Recently, morphing concepts for UAV or MAV have been significant issues in aerospace engineering. Morphing wing concept, a biomimetic technology in aerospace engineering, has been realized by various methods including changes of wing's cross-section, plan form, and spar position. This paper investigates a morphing wing with variable camber using SMA actuators. The test model is a symmetric wing structure composed of two tapered graphite/epoxy composite plates and a steel body. Shape memory alloy (SMA) is attracting much attention as actuators for controlling the shape of structures because of high recovery force and large deformation. Four pairs of the SMA wire actuators are attached on the bottom surfaces of the wings in the chord-wise direction. SMA actuators produce enough deformation to cause significant improvement the static and dynamic characteristics of the wing model. Lift and drag forces, most important static aerodynamic characteristics, were measured at various angles of attack. Lift of the wing was increased without increasing drag forces when electric current was applied to the SMA actuators. Dynamic vibration signals were measured by FBG sensor at the root of the wing. The FBG sensor was successfully applied to the monitoring of the aeroelastic unstable phenomena at various angles of attack. At flutter speed, limit cycle oscillation with constant frequency occurred. It was also observed that the vibration energy is concentrated on the flutter mode and increased with the increase of the airflow speed. The effects of the angle of attack on aeroelastic characteristics of the wing were investigated. The amplitude of the limit cycle oscillation was significantly reduced at the flutter velocity when SMA actuators were activated.