Structural Health Monitoring (SHM) based on Lamb waves is a novel technology using permanently attached actuator and sensor networks, data acquisition and data evaluation systems to enable in-service inspection of composite structures. By analysing the sensor signals, different kinds of structural damages can be detected and located. The aim is to prove the damage detection and localisation in complex and realistic composite aircraft structures. Therefore, a door surround panel is developed and manufactured because of its high structural complexity and its high impact probability during aircraft operation. This panel consists of skin, 44 stringers, 4 typical frames, a complete set of door frames and 584 piezoceramic sensors incl. wiring harnesses. A robust sensor network and manufacturing process is developed in order to integrate the SHM network into the manufacturing process of the structure (co-bonding) and to reduce the manufacturing effort and costs. It is proven that all 584 integrated sensors survived the different manufacturing steps of the door surround structure.
Credit: DLR (CC BY-NC-ND 3.0).
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Researchers at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) are researching a morphing wing trailing edge that can be smoothly transformed into any shape and will make conventional flaps redundant. The flaps on the wings of today’s commercial airliners are actuated via a complicated mechanism. Their arrangement and the resulting gap when they are extended compromises the aerodynamics, increases fuel consumption and contributes to inflight noise. The new technology, on the other hand, is flexible, its movement being based on that of carnivorous plants. This enables the gap between the wing and the flap to be eliminated.
Icing of aerodynamic surfaces causes decrease of performance and is a safety concern. Therefore, ice protection and detection systems are necessary for airplanes. For investigation in this field of research, a deicing test stand was built up.
Fin stabilisers are used to improve the passengers’ comfort via reduction of the roll motion. Conventional fin stabilisers produce hydrodynamic forces to counteract the roll moment of the vessel and thereby reduce the roll motion during cruise. However, the attenuation of the roll motion is also appreciated when anchored, i.e. in zero speed mode as well. Zero-speed fins are characterised by a larger chord and a less balanced fin that enables the paddle principle for roll reduction. In general, these designs require a larger driving torque. To improve the effectiveness of such a system, a flexible trailing edge is developed and tested together with SKF Blohm + Voss Industries, BaltiCo and the Federal Police in Germany. The structural concept features a flexible, load-bearing GFRP plate in combination with a polyethylene foam core and a polyurethane skin.
Asteroid (sampling) missions are of high interest for finding a missing link in the evolution of our solar system and the development of life on earth. In this context the Mobile Asteroid Surface Scout (MASCOT) – a small ‘shoe box’-shaped 10kg lander package was developed at DLR in cooperation with JAXA (Japan Aerospace Exploration Agency) and CNES (Centre National d’Études Spatiales). At 3rd December 2014 it was launched on-board of JAXA’s Hayabusa-2 S/C towards the Cclass asteroid 1999 JU3. Reaching there MASCOT will support the mother spacecraft with its landing site selection (for sample up-take). To guide the extremely high mechanical launch loads and to cope with the tilted accommodation on Hayabusa-2, MASCOT is split up into two parts, a mechanical support structure and the landing module itself. Within DLR the Institute of Composite Structures and Adaptive Systems is responsible for the complete structural design and manufacturing of MASCOT. While both structures weigh only 1.4 kg in total, at the same time they must withstand a launch load equivalent to more than 350 times their own mass, i.e. half a ton.
Automation will be the key factor for an increasing use of composite technology in all industrial areas. Some automated technologies are already used in the manufacturing process of large composite components. However, there are still problems during manufacturing, which could not yet be resolved completely. Furthermore, the drawbacks of the cooling chain and the expensive autoclave process deter the use of composite technology in some industrial areas. It is the aim to demonstrate the suitability of a new manufacturing approach regarding the automated fibre placement. The bonding of consolidated fiber tapes should allow an optimal utilisation of the fibre properties. It eliminates typical manufacturing defects. In order to show the automated processing of the consolidated tape, a rudimentary placement unit is under development. The unit takes into account the changed material properties and verifies the use of consolidated fibre tapes for an automated process.
Improvements of the efficiency play a vital role in the design of future commercial aircraft. An efficient high-lift system, which is being investigated in the Collaborative Research Centre 880 benefits from the so-called Coandă effect. A key element of this system is a contour-variable leading edge, because it allows adapting of the wing geometry to the aerodynamic requirements of different flight phases better than conventional high-lift devices. The concepts and methods for the structural realisation of such a leading edge are investigated at the DLR Institute of Composite Structures and Adaptive Systems.
In the challenging design space of a natural laminar flow wing, a multi-material, multi-functional leading edge was developed. The leading edge, consisting of CFRP as structural material, features an integrally bonded steel foil erosion shielding. The deviating coefficients of thermal elongation of erosion shield and structure, leading to shape distortions over the wide range of operational and thus thermal environment of an aircraft, are taken into account by a unique kind of attachment. The leading edge is joined to the leading edge ribs with struts just at the Krueger landing and to the wing upper cover on the inside of the structure with a joint design named “floating lap joint”. Through the use of eccentric bushings, the leading edge becomes fully interchangeable. Free of waviness, without fastener heads on the outside, this solution enables the designer to tailor a laminar leading edge that adopts its laminar shape in cruise flight, therefore manufactured pre-shaped, being installable force-free and ensuring safety of operation of adjacent systems at every point of the flight envelope.
Due to its material thickness of only 0.1 mm, an 8 m long boom of the current design weighs less than 500 gram. In spite of the light weight, the booms are very stiff and can be used as basic modules for various large space structures at future space missions. Potential applications for those booms are deployable solar sails for propellant less propulsion or even solar arrays and low frequency radar antennas.
The buckling and post-buckling analysis of stiffened thin-walled composite structures is often performed by complex and time-consuming methods. Kriging based metamodels can be employed to describe this buckling behaviour efficiently and without big loss in accuracy.
SAGITTA Unbemanntes Luftfahrzeug
A new online quality assurance concept for the production of carbon components in autoclave processes is currently being researched by the Center for Lightweight-Production-Technology (ZLP) of the German Aerospace Center in Stade. In this field of research, the temperature is an essential process parameter. Current sensors for measuring the temperature have the disadvantage of being firmly anchored to tools and thus they can only measure temperatures of defined positions. With the use of a thermography system in combination with a linear drive inside the autoclave, 2D temperature measurements of the part surface can be made. In this manner, a new source of temperature data is available for the improvement of the autoclave processes.
Despite the progress in the development of electrical storage devices, the quest for more efficiency by improved specific properties is continuously driven by increasing energy requirements. There is a particular need for volume and weight savings in mobile products such as portable electronics or hybrid/electric vehicles and aircrafts. Structural supercapacitors are promising multifunctional energy storage devices bearing mechanical loads and storing/delivering electrical energy simultaneously.Currently, most commercial supercapacitors are using ionic liquids as electrolytes. However, safety issues and light structure design for usage should also be taken into consideration. Recent research focuses on lithium ion solid electrolyte which can be applied in electrical energy storage devices without any leakage risks. Therefore, LiAlTi(PO4)3-based solid electrolytes have been developed and embedded into composite materials, which demonstrate a potential being utilised as solid electrolyte for multifunctional energy storage devices.
Strukturintegrierte Lichtquellen
In contrast to conventionally used aluminium, CFRP has a different fire behaviour with a high resistance against burn through. However, the smoke generation is much higher and mechanical properties of CFRP decrease as a result of matrix decomposition, which in turn leads to a loss of structural integrity. The CORINNA project investigates the optimisation of fire properties of CFRP fuselage materials in a ‘pool-fire’-scenario (a kerosene fire underneath a grounded aircraft) with the aim to increase the evacuation time for passengers. Hybrid material systems are being developed for structural composite components, where the flame retardant is directly incorporated into the material. These materials form a barrier against thermal radiation and/or gases or can be a source for delamination in case of a fire and protect the underlying structure from the effects of the flames.
Neuartige Flugzeugbauteile aus leichtem kohlefaserverstärktem Kunststoff (CFK) müssen in einem Autoklaven, einer Art großem Ofen, ausgehärtet werden. Das Problem: während des Aushärtungsprozesses erhalten die Wissenschaftler keine Information über eventuelle Fehler oder Mängel im Bauteil und können den Aushärtungsprozess nicht unterbrechen. Forscher des Deutschen Zentrums für Luft- und Raumfahrt (DLR) haben im Rahmen des EU-Projekts LOCOMACHS Sensoren entwickelt, die Aufschluss über die Qualität des im Autoklaven befindlichen Bauteils geben, so dass im Falle von Mängeln die Produktion vorzeitig abgebrochen werden kann. Das spart Zeit, Geld und schont die Umwelt. Für diese Entwicklung haben sie am 2. Juni 2015 den (JEC) Innovation Award in der Kategorie "Aeronautics" in Houston erhalten.