Preliminary design of a novel morphing rib architecture based on lumped elastic properties

Aircraft wings are usually optimized for a specific design point. However, since they operate in a wide variety of flight regimes, some of these have conflicting impacts on aircraft design, as an aerodynamically efficient configuration in one instance may perform poorly in others. Ideally rigid, non-deformable aircraft structures preclude any adaptation to changing conditions. Alternatively, morphing wings can provide adaptive capabilities to maximize aircraft performance in every flight condition. It is therefore not surprising that several research programs are currently running worldwide to explore the feasibility of morphing concepts especially with reference to their benefits/drawbacks ratio. Among these, the CRIAQ MD0505 project was launched; the project represents the first joined research program between Canadian and Italian academies, research centres and leading industries. Referring to the wing tip of a regional transportation aircraft, the program addresses the implementation of combined smart structures specifically conceived to optimize the aerodynamic efficiency; more in detail an adaptive-bump configuration is investigated for the upper skin of the wing box (to control the separation point between laminar and turbulent flow) and a variable camber aileron architecture. In this framework the authors focused on the design of a morphing aileron characterized by active ribs enabling the in-flight modification of external airfoil shape. On the base of specific requirements regarding target morphing shape to be matched and loads to be withstood, an innovative architecture was developed for the active rib; the rib is chordwise divided in three main blocks connected by crossed springs which assure relative rotation among blocks while contributing to the absorption of external solicitations.. In this paper, the preliminary design phase of the rib has been outlined, from the concept definition up to the assessment of structural properties and actuation system through advanced FE analyses.