## 3 Aerospace Engineering Applications
### Aplication to Wing Morphing
After manufacturing a prototype of morphing winglets, the aerodynamic performances were evaluated under the wind tunnel test under various attack angles. It was confirmed that aerodynamic performance of the UAV can be improved by controlling the wing-tip configuration with consideration of the inclined angle of the UAV. The proposed morphing winglet for UAV is presented in Figure 8. [PERSON] et al. reported on research works on morphing wings using SMA actuators in a review paper on morphing aircraft using smart materials [104]. In addition to the morphing structure technology using the SMA actuator, various morphing structure technologies using piezoelectric materials, electro-active polymers, and magnetostriction were summarized and reported. [PERSON] et al. reported in an introspective paper about SMA applications in aircraft morphing technology [105]. They compared the characteristics of SMA, SMP, and shape memory polymer composites (SMPC), and the aerospace applications of each material are summarized. [PERSON] and [PERSON] investigated a case study of camber change for the horizontal tail in the UAV, and a numerical simulation was conducted to exam the SMA actuator-based camber change [106]. A maximum deflection of 0.6 mm at the trailing edge tip was detected in the numerical results. [PERSON] and [PERSON] reported in a review paper about morphing surfaces using SMA actuators [107]. After giving an overview of research on SMA actuators, adaptive aerodynamics applications of an SMA actuator were investigated. The numerical case study was investigated for the feasibility demonstration of the actuation of a spoiler trailing edge with SMA actuators. [PERSON] and [PERSON] reported in a short review paper on SMA actuators for aerospace engineering, including modeling and experiments for morphing wings, inlet geometry, and tailoring of the orientation of various propulsion systems, and variable chevron shape for noise and thrust optimization [108]. Space applications for isolation of vibration, self-deployable solar sails, and low-shock release devices were proposed. [PERSON]  
Figure 8: UAV with soft morphing winglets [103] Reproduced with permission from Elsevier under STM Permissions Guidelines. (**a**) wind tunnel test setup, (**b**) morphing winglet with \(\alpha=3^{\circ}\), (**c**) morphing winglet with \(\alpha=9^{\circ}\). Figure 7: Conceptual design of SMA actuator for morphing airfoil models [101] © IOP Publishing. Reproduced with permission. All rights reserved. et al. developed a multi-segment morphing system for the micro air vehicle (MAV) using SMA actuators [109]. They applied an adaptive control algorithm that can provide fast, concurrent, and independent operation of four-segment morphing with SMA actuators. The system was implemented using an open-source autopilot with an additional weight of 6 g per segment of morphing. [PERSON] et al., for the application of morphing flap of an unmanned aerial vehicle (UAV), proposed a hybrid composite actuator capable of maintaining the shape of an integrated SMA wire and SMP support [110]. For the improvement of the aerodynamic force in combination with the shape transformation of the wing, the proposed composite actuator was implemented as a part of the morphing wing. Through the test under wind tunnel condition, it was observed that the lift coefficients were higher by about 35%, and the drag coefficient was lower by about 50% than the conventional one. [PERSON] et al. carried out numerical simulations for the shape prediction of the trailing edge driven by a combination of SMA wires and Macro-Fiber Composite (MFC) bimorphs actuators [111]. To achieve large deflection at low frequency and rapid actuation with small deflection, an SMA wire and MFC patch was utilized, respectively. [PERSON] et al. proposed an effective methodology to design deformable wing shapes to achieve predefined target wing configurations by adjusting the applied temperature to the SMA actuator [112].