Preliminary failure analysis of an innovative morphing flap tailored for large civil aircraft applications

Aircraft wings are usually optimized for a specific mission design point. However, since they operate in a wide variety of flight conditions, some of these have conflicting impacts on aircraft design process, as a single configuration may be efficient in one instance but perform poorly in others. A shape-shifting surface, or usually referred as 'morphing', potentially enables transport aircraft to reach maximum performance in any flight conditions. Within the framework of the Joint Technology Initiative Clean Sky (JTI-CS) project, and during the first phase of the Green Regional Aircraft Integrated Technological Demonstration (GRA-ITD), the authors focused on the design and technological demonstration of an innovative bi-modal morphing outer wing flap to be installed on the next generation open rotor green regional aircraft. A novel active rib layout was designed to enable the articulation of the entire flap structure by means of multi-box arrangement. In order to prove structural load-carrying capabilities with the reference to a relevant environment, the full-scale morphing flap was properly analyzed by means of detailed finite element model analysis. To the authors' knowledge, there is no morphing concept in literature based on a similar architecture based on distributed servo-mechanical actuators. Hence, a rational review of the potential problems associated with actuators off-design conditions has been conducted to investigate the maturity of the concept and safety issues concerning the flap ground static test. In addition, useful insights have been provided to effectively detect potential failure conditions in service.