International Conference on Adaptive Structures and Technologies ( ICAST ) University Park , Pennsylvania , October 4 – 6 , 2010 1 Morphing Trailing Edges with Shape Memory Alloy Rods

Multiple flight regimes during typical aircraft missions mean that a single unique optimized configuration, that maximizes aerodynamic efficiency and maneuverability, cannot be defined. Discrete components such as ailerons and flaps provide some adaptability, although they are far from optimal. Wing morphing can significantly improve the performance of future aircrafts, by adapting the wing shape to the specific flight regime requirements, but also represents a challenging problem: the structure has to be stiff to maintain its shape under loads, and yet be flexible to deform without collapse. One solution is to adopt structural elements made of smart materials; Shape Memory Alloys (SMAs) have demonstrated their suitability for many static applications due to their high structural integration potential and remarkable actuation capabilities. This paper proposes an innovative flap architecture for a variable camber trailing edge, whose reference geometry is based on a full scale wing for a regional transport aircraft. The compliant rib is based on a truss-like structure where some members are “active” rods made of SMA. These actuators are able to sustain the external loads while allowing controlled shape modification. Elastic elements are incorporated to provide pre-straining for the SMA and therefore allow cyclic actuation. The layout of the structure is obtained using a preliminary optimization process, incorporating practical constraints, by focusing on a basic truss-like element and its repetition and position within the overall truss. The aerostructural performance is estimated using FE analysis. The SMA behavior is modeled using a dedicated routine to evaluate the internal stress state and the minimum activation temperature. The design fulfils a number of key requirements: a smooth actuation along the chord; morphed shapes that assure the optimal aerodynamic load distribution for high lift; light weight; low mechanical complexity. The design features of the architecture are investigated, and the requirements of the morphing skin discussed.

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