Multifunktionale Flügelvorderkante in Multimaterialbauweise

Neben der Gewichtsreduktion durch den Einsatz von Faserverbundwerkstoffen kann im Flugzeugbau die Widerstandsreduktion durch die Laminarhaltung der Grenzschicht am Tragflügel einen signifikanten Beitrag leisten. Ein wichtiger Baustein im Zusammenführen beider Ansätze ist die multifunktionale Flügelvorderkante in Multimaterialbauweise

Structural concept of ECHO - Hybrid bonding and laminar joints

The Clean Sky 2 project ECHO focuses on integrating a hybrid laminar flow control (HLFC) system on a horizontal stabilizer for a long-range aircraft. HLFC extracts a portion of the boundary layer to stabilize the flow, reducing drag on the airfoil. The transition from laminar to turbulent flow must be retarded on the airfoil far behind the leading edge. For this reason, the horizontal stabilizer box has tight tolerances and a minimum number of gaps and steps. A common approach to reduce the gap dimensions is filler, but this process is time consuming and exact geometry cannot be guaranteed due to the high thermal expansion of the filler. In this new concept, a preformed steel foil is used to cover the studs in the gap between the leading edge and the box. The foil is bonded to the titanium leading edge after the leading edge is assembled. This ensures both accessibility of the fasteners in case of maintenance and compliance with aerodynamic requirements

Entwicklung einer laminaren Flügelschale

Technologien zur Senkung des Treibstoffbedarfs und der CO2-Emissionen stehen im Fokus der Verkehrsflugzeugentwicklung. Die Widerstandesreduktion durch die Laminarhaltung der Grenzschicht am Tragflügel kann hier einen signifikanten Beitrag leisten. Zum Erreichen dieses Ziels ist die Einhaltung hoher Anforderungen an die aerodynamische Oberfläche notwendig, was gerade in einer Faserverbundbauweise besondere Herausforderungen mit sich bringt

Laminar Interface Concept for a HLFC Horizontal Tailplane Leading Edge, Design and Manufacturing Approach

With the aim of reducing fuel consumption and CO2 emissions, the CS2 HLFC on HTP project is investigating the replacement of a conventional leading edge on the horizontal tailplane of an Airbus A350 with a leading edge equipped with an active HLFC system. By extracting a part of the boundary layer through a perforated titanium outer skin, the laminar flow is stabilised and thus the aerodynamic drag is reduced. In order to prevent laminar-turbulent transition of the boundary layer behind the suction area at the leading edge, tight tolerances for gaps and steps must be maintained at the interface to the HTP box. With state-of-the-art technology, gaps between the components are closed with a filling compound. This is a time-consuming process and compliance with the exact geometry is not guaranteed due to the strong thermal expansion of the filler. Also, the bolt heads of the structural connection can disturb the laminar flow. A design concept is presented for the attachment of the leading edge to the HTP box, covering the bolts and the gap between the leading edge and the skin of the HTP box with a pre-curved steel foil, which is bonded onto the titanium leading edge skin after the leading edge has been assembled. This ensures both the accessibility of the fastening elements in the case of a necessary replacement if damage has occurred, as well as complying with the aerodynamic requirement

A Multi-material, Multi-functional Leading Edge for the Laminar Flow Wing

Furthered by economic goals and society`s ecological awareness, laminar flow control technologies move increasingly into focus in transport aircraft design. The reduced friction drag of a natural laminar flow wing enables a reduction in fuel consumption and thus reduction of CO2 emissions and decreasing operational costs. Additional to requirements on conventional wings, a natural laminar flow wing has to comply with high demands on its surface quality. Very small steps, gaps, waviness or lightly protruding fastener heads may cause a laminar-turbulent transition of the sensitive boundary layer flow

Design Optimization of a CFRP Wing Cover for the AFP Process

The economic application of carbon fiber reinforced plastics in large-scale aerospace structures demands cost-efficient production technologies. In recent years, much progress was achieved in automation engineering, like automated fiber placement (AFP) and automated tape laying (ATL) technologies. In the design process, new methods have been established to incorporate boundary conditions of the production process. Henceforth the optimization process is not only focused on weight-reduction, but on an improved cost/weight ratio. Most research on this topic has been done in the field of conceptual design, as the highest percentage of the later arising manufacturing cost is defined by decisions made in the early design phase. But there is also a potential for reducing production cost in the detailed design phase. In the Composite Design department of the DLR Institute of Composite Structures and Adaptive Systems the detailed design of a wing cover skin section was optimized for the AFP-process. Ply shapes and ramp geometries have been modified to reduce the number of courses needed for ply-layup, and thus to reduce production time. Uncomplete courses with less than all of the available tows, as well as repeated stops and acceleration of the fiber-placement head due to unnecessary tow-cutting processes have been avoided. With these approaches the total layup time was reduced by 3,4% whereas the on-surface time of the fibre placement heads decreased by even 5% compared to the reference design, while structural weight remained constant. The optimization strategies, originally developed for the AFP-process, are also applicable to the ATL-process. The optimized design was analyzed in 3 sections and compared to the reference design for 408 combinations of longitudinal, transversal and shear loads, showing only minor differences in strength and stability