GLARE

Glare (derived from GLAss REinforced laminate ) is a fiber metal laminate (FML) composed of several very thin layers of metal (usually aluminum) interspersed with layers of S-2 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 aluminum 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 aluminum are:

Furthermore, the material can be tailored during design and manufacture so 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.

While a simple manufactured sheet of Glare is three to ten times more expensive than an equivalent sheet of aluminum, considerable production savings can be made using the aforementioned optimization. A structure built with Glare is lighter and less complex than an equivalent metal structure, requires less inspection and maintenance, and has a longer lifetime-till failure. These characteristics can make Glare cheaper, lighter, and safer to use in the long run.

Glare is a relatively successful FML, patented by the Dutch company Akzo Nobel in 1987. It entered major application in 2007, when the Airbus A380 airliner began commercial service. Much of the research and development was done in the 1970s and 1980s at the Faculty of Aerospace Engineering, Delft University of Technology, where professors and researchers advanced the knowledge of FML and earned several patents, such as a splicing technique to build wider and longer panels without requiring external joints.

The development of FML reflects a 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 aluminum laminates compared to monolithic aluminum. Later, the United States National Aeronautics and Space Administration (NASA) became interested in reinforcing metal parts with composite materials in the Space Shuttle program, which led to the introduction of fibers to the bond layers. Thus, 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 Reinforced ALuminum Laminates (ARALL), which combined aluminum with aramid fibers and was patented in 1981. This material had some cost, manufacturing, and application problems; while it had very high tensile strength, the material proved suboptimal in compressive strength, off-axis loading, and cyclic loading. These issues led to an improved version with glass fiber instead of aramid fibers.