Morphing technologies for the aviation of the future.
MORPHING, COMPOSITE MATERIALS, High lift devices, LEADING EDGE, LIGHTWEIGHTING, AVIATION, RELIABILITY
Quiet, safe and energy-saving – our wish-list for the airplanes of tomorrow. Fraunhofer LBF is contributing to this through the “morphing leading edge”, i.e. the malleable wing leading edge which adjusts to the current aerodynamic requirements. The wing curvature, and therefore also its uplift, increases during slow flight. However, unlike traditional high-lift flaps, gaps do not open up, which means that flow noise and drag are avoided.
Complex system development for aviation
In order to achieve this goal, many individual problems need to be solved. What material achieves the required malleability? And does so across the full temperature range? How can the necessary malleability be achieved without the material being too heavy and taking up too much assembly space? What redundancy designs are required to ensure the required safety for aviation? These and other questions were pursued by Fraunhofer LBF scientists in collaboration with other Fraunhofer Institutes and the industry partner Airbus DS within the scope of the EU-sponsored “Clean Sky 2” project. This resulted in a suggestion for a constructive solution, which should fulfill the various requirements as well as possible, see Figure 1.
Figure 1: Draft of the Morphing Leading Edge by Fraunhofer LBF. (© Fraunhofer LBF)
The conflict between the goals of the high rigidity which the skin structure of the “Morphing Leading Edge” (MLE) requires in order to absorb the high air loads and the high malleability which is necessary for the task was resolved by the selection of a composite material based on carbon fiber – a material which also offers many benefits within the scope of lightweighting. The thickness and inner layout of the laminate vary locally. The layout of the skin structure is tailored to ensure the required rigidity and resistance properties at all points. The suitability of the material for the required life span was also proven during materials testing. Residual stresses which could arise as a result of thermal expansion or contraction were analyzed numerically and solved constructively using clever combinations of materials.
A CNT-based de-icing system and laser-supported form monitoring are also integrated into the system.
Redundant systems ensure reliability
The actuation follows the trend for “more electric aircraft”, which is prevailing in aviation. Accordingly, the use of energy-intensive hydraulics needed to be avoided as far as possible. For this reason, electromechanical actors were selected here. A serial redundancy concept was chosen to ensure the reliability of the system. This guarantees that the MLE is fully functional even if an actor fails, and safely avoids the structure becoming overloaded as a result of a defective, opposite start-up of both actors. Other faults were analyzed with regard to their consequences in order to minimize risks for safe flight operation.
The expected component loads due to air pressure and skin rigidity were determined by means of numerical analyses, while the required power transmission elements were designed in a structurally durable manner taking into account the significant lightweighting requirements.
The “Morphing Leading Edge” system which has up to now been developed digitally is set to be built into hardware too – pending approval of project continuation – and will be able to demonstrate the functional capacity of the solution.
EU, Clean Sky 2 program, CS2-AlR-GAM-2019
“Yet another successful example of the substantial Fraunhofer competency in the field of aviation.” Dr. Volker Landersheim
- Dr. Volker Landersheim
- Phone: +49 6151 705-475