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Glass reinforced aluminium (GLARE) is a fiber metal laminate (FML) composed of several very thin layers of metal (usually aluminium) interspersed with layers of glass-fiber pre-preg, bonded together with a matrix such as epoxy. The uni-directional pre-preg layers may be aligned in different directions to suit predicted stress conditions.
Though GLARE is a composite material, its material properties and fabrication are very similar to bulk aluminium metal sheets. It has far less in common with composite structures when it comes to design, manufacture, inspection, or maintenance. GLARE parts are constructed and repaired using mostly conventional metal working techniques.
Its major advantages over conventional aluminium are:
- Better "damage tolerance" behavior (especially impact and metal fatigue, as the elastic strain is larger than other metal material it can consume more impact energy. It is dented easier but has a higher penetration resistance )
- Better corrosion resistance
- Better fire resistance
- Lower specific weight
Furthermore, it is possible to "tailor" the material during design and manufacture such that the number, type and alignment of layers can suit the local stresses and shapes throughout the aircraft. This allows the production of double-curved sections, complex integrated panels or very large sheets, for example.
While a simple manufactured sheet of GLARE is more expensive than an equivalent sheet of aluminium, considerable production savings can be made using the aforementioned optimization. A structure properly designed for GLARE is significantly lighter and less complex than an equivalent metal structure, requires less inspection and maintenance, and has a longer lifetime-till failure, often making it cheaper, lighter, and safer in the long run.
GLARE is a relatively successful FML, patented by Akzo Nobel in 1987. It has entered commercial application in the Airbus A380. The several patents mention among others as inventors Vogelesang, Schijve, Roebroeks and Marissen, then professors and researchers at the Faculty of Aerospace Engineering, Delft University of Technology, where much of the R & D on FML was done in the 1970s and 1980s.
The fruition of FML development marks a step in the long history of research that started in 1945 at Fokker, where earlier bonding experience at de Havilland inspired investigation into the improved properties of bonded aluminium laminates compared to monolithic aluminium. Later, NASA got interested in reinforcing metal parts with composite materials as part of the Space Shuttle program led to the introduction of fibers to the bond layers, and the concept of FMLs was born.
Further research and co-operation of Fokker with Delft University, the Dutch Aerospace Laboratory NLR, 3M, Alcoa and various other companies and institutions led to the first FML, the Aramid fiber based ARALL. This proved to have some cost, manufacturing and application problems (while it had a very high tensile strength; compression, off-axis loading and cyclic loading proved problematic), which lead to an improved version with glass-fiber instead of aramid fibers.
Over the course of the development of the material, which took more than 30 years from start to the major application on the Airbus A380, many other production and development partners have been involved, including Boeing, McDonnell Douglas, Bombardier, and the US Air Force. Over the course of time, companies withdrew from this involvement, sometimes to come back after a couple of years, like Alcoa who withdrew in 1995 to come back in 2004 and withdrew once again in 2010. These strategic decisions show the dynamic nature of innovation processes.
Besides the applications on the Airbus A380 fuselage, GLARE has multiple 'secondary' applications. GLARE is also the material used in the ECOS3 blast-resistant Unit Load Device. This is freight container shown to completely contain the explosion and fire resulting from a bomb such as that used over Lockerbie. Other applications include among others the application in the Learjet 45 and in the past also in cargo floors of the Boeing 737.
GLARE is currently produced by GKN-Fokker in the Netherlands and Airbus in Nordenham, Germany. GKN- Fokker opened a brand new facility next to its existing facilities in Papendrecht, the Netherlands where they produce Glare sheets of 4.5 x 11.5 m, including the milling of doors windows etc. on a 5-axis milling machine with a movable bed.
Glare has also been used to make cargo doors for later models of the C-17 Globemaster III.
- Vermeeren, Coen (Editor) Around Glare: A New Aircraft Material in Context Published by Springer, August 1, 2002 ISBN 1-4020-0778-7
- Vlot, Ad Glare: history of the development of a new aircraft material Kluwer Academic Publishers, 2001 ISBN 1-4020-0124-X
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