Woodruff School of Mechanical Engineering



Morphing Airfoil Using Compliant Structures and Variable Stiffness Approaches


Dr. Paolo Ermanni


ETH Zurich


Thursday, March 8, 2012 at 3:30:00 PM


Guggenheim Building, Room 442


Massimo Ruzzene
(404) 894 3078


Lightweight structures are constructed to carry and transfer loads with minimum material usage considering a wide set of structural requirements (e.g. sufficient high margin of safety against failure, creep, buckling, too high deformation, fatigue under all occurring operating conditions). The design space available to engineers has been considerably expanded by the introduction of composite and adaptive materials with outstanding mechanical properties and functional features, opening-up for new and somehow intriguing applications, which in fact tend more and more to mimic typical functionalities of living systems, one of them being shape adaptation. Shape adaptation is conceivable in principle for all mechanical systems. Yet, it is of particular importance in energy conversion and transportation, where conventional design solutions show limitations in the ability to cope with a complex set of conflicting requirements such as high stiffness, shape adaptation, aerodynamic load alleviation, and substantial amounts of structural damping. The first part of the talk is devoted to airfoil morphing using compliant concepts with adaptive materials. Compliant systems are designed to be hinge-less, combining load-carrying properties with functionalities, which are specific to mechanisms. Morphing is realized by taking advantage of the elastic properties of the material, thus introducing a controlled flexibility in the structure. Our approach is involving several disciplines starting from design objectives based directly on aerodynamic performances instead of prescribing fixed geometrical shapes. Multi-disciplinary optimization is applied to 2D- and 3D-configurations. Depending on the problem to be solved, design parameters are related to topology, size as well as the undeformed shape of the airfoil. Promising aerodynamic and structural morphing performances have been obtained by applying Dielectric Elastomers and Shape Memory Alloys as actuators. The second part of the talk is dealing with the integration of variable stiffness elements in the airfoil structure. The basic concept is relying on layers with variable shear stress transfer, controlled by temperature or electric fields. In particular, we are investigating novel forms of direct electrostatic coupling. The concept of Electro Bonded Laminates (EBL) relies on the combination of electrostatic normal forces and friction between laminate layers in order to actively control the bending-twist coupling of the system. The mechanical response is strongly dependent on the electrical properties of its polymer constitutive films in terms of dielectric and the insulating properties. Multilayer polymer configuration is considered as a possible answer to this need and it is put forward together with the electric model and the relatively high frequency experimental evidence of the proposed solution.


Paolo Ermanni, studied Mechanical Engineering at the ETH Zürich. He received his Dr. sc. techn. degree at the ETH Zurich in 1990 under the guidance of Prof. Dr. M. Flemming. His research work was focusing on process technologies for highly integrated aircraft fuselage structures made of composite materials. He spent more than five years at Airbus Germany in Hamburg as a senior engineer and later on, as a project manager. In 1997 he took on a new challenge as a manager in the consulting firm A.T. Kearney in Milan. He was appointed associate professor at ETH Zurich in 1998 and has been full Professor of composite materials and adaptive structures at ETH Zurich since April 1, 2003.