While the low weight of aluminium means that it is still the most common material used in aircraft construction, this staple of the aerospace industry does nevertheless have a few less desirable properties. It’s not the strongest material around, nor is it the easiest to weld together and, despite its low weight, designers would still like to get their hands on something even lighter.
Now, it seems, their wishes have been granted, with the introduction of a material that is said to exhibit all of the benefits and none of the problems of aluminium. It will make its first large-scale debut on the Airbus A380.
Called Glare, it has been under development for over 20 years at the Delft technical university in Holland, but has only recently entered mass production. According to its Dutch manufacturer, Stork Fokker, it is lighter, cheaper, stronger, more resistant to fire and impact damage, and less prone to fatigue.
Glare – which stands for Glass fibre Reinforced Aluminium – will be used on 400m2 of upper fuselage sections of the A380 where, according to Airbus vice-president Charles Champion, it will help to save around one tonne in weight.
The material, which is a laminate with alternating layers of aluminium and glass fibre-reinforced adhesive, could be thought of as a ‘ply-metal’. It looks the same as aluminium sheeting, but it is constructed from 1mm thick layers; first a thin layer of aluminium, then a thin layer of strong glass fibre, and then another layer of aluminium.
As well as being 10 per cent less dense than aluminium, Glare has proved to be less prone to fatigue, and its fire and damage resistance is claimed to be superior . Indeed, according to Airbus, testing has demonstrated that an artificial crack subjected to thousands of flight cycles hardly increases in size.
This is because the glass fibres sandwiched between the aluminum layers are capable of keeping the material together and preventing tearing. And because the first glass fibre layer prevents any penetration beyond the superficial aluminium coating it is said to have high corrosion resistance.
The manufacture of Glare involves a hot-bonded manufacturing process where the sandwich of alternating layers of glass fibre and aluminum are bonded under high pressure and temperature in an autoclave specially developed by German manufacturer Maschinenbau Scholz . This giant oven is 23m long, 5.5m in diameter, and weighs 160 tonnes.
The different layers are securely bonded using an epoxy resin. According to an Airbus spokesman, the resin and bonding are able to resist the extreme operating conditions encountered in flight, such as pressure, tension and torsion forces, as well as extreme temperatures.