TAGS: Thermoplastic Composites
Researchers at the Deutsches Zentrum für Luft- und Raumfahrt (DLR) are working on the FlexMat project to investigate the possibility of using a flexible surface between the aircraft wing and the moving surfaces for noise reduction. DLR is working in collaboration with Invent and the Technical University of Munich for this project.
Artificial Skin for Reduced Sound
The transition skin tested by DLR has a span of one meter. It consists of a mix of materials, comprising synthetic rubber – ethylene propylene diene monomer rubber (EPDM) and glass-fiber reinforced composites. The rubber forms the basis for the skin, into which the researchers inserted glass-fiber plates at varying intervals, on both the outer and inner surfaces.
The deformation properties of the transition skin can be adjusted by means of the soft, flexible rubber and the positioning of the rigid glass-fiber strips. The researchers endeavored to keep local deformations to a minimum, so that the glass-fiber composites and rubber did not separate.
"The final tests using a demonstrator showed that the wing skin being tested is very hard-wearing and can be deformed to a large extent," says Martin Radestock, DLR. "In the event of extreme deformation, the only thing that needs care is the paintwork, to make sure that it does not crack."
The use of a flexible skin on wing leading edges has been shown to be feasible. Further testing will be necessary in order to check the extent to which noise and drag can be reduced using this technique and determine the maximum load limit of the skin.
Flexible Skin to Withstand Extreme Aerodynamic Loads
The direct transitions between the fixed part of the wing and the moving control surfaces or high-lift devices need to be avoided. This could be achieved with a flexible skin between the fixed wing and the moving components. The new skin must be able to withstand extreme aerodynamic loads, but it must not be too stiff, otherwise the systems driving the moving components would have to be able to exert additional force.
"
Continuous transitions between flap systems and the main aerofoil would be a huge advantage for future laminar flow wings, which allow air to pass around them without turbulence," says Radestock. "
This could reduce airflow turbulence and ensure laminar stability." Among other things, laminar flow wings result in lower drag, which is beneficial for the environment.
"We concentrated on the outboard area of the wing," explains Radestock. "
The slat on the leading edge was replaced with a variable-shape leading edge, referred to as a droop flap, which was developed and researched at our institute back in 2007. We also installed our transition skin." A transition triangle from the Technical University of Munich was applied between the aileron and the trailing edge of the wing.
Source: Deutsches Zentrum für Luft- und Raumfahrt (DLR)