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Weight is everything when it comes to heavier-than-air machines, and designers have striven continuously to improve lift to weight ratios since man first took to the air. Composite materials have played a major part in weight reduction by replacing lot of heavy weight components. Composites are versatile, used for both structural applications and components, in all aircraft and spacecraft, from hot air balloon gondolas and gliders, to passenger airliners, fighter planes and the Space Shuttle. Applications range from complete airplanes such as the Beech Starship, to wing assemblies, helicopter rotor blades, propellers, seats and instrument enclosures. Composite materials can provide a much better strength-to-weight ratio than metals, sometimes by as much as 20% better. The lower weight results in lower fuel consumption and emissions and, because plastic structures need fewer riveted joints, enhanced aerodynamic efficiencies and lower manufacturing costs. The aviation industry was, naturally, attracted by such benefits when composites first made an appearance, but it was the manufacturers of military aircraft who initially seized the opportunity to exploit their use to improve the speed and maneuverability of their products.

We have already touched on a few, such as weight saving, but here is a full list:

• Weight reduction - savings in the range 20%-50% are often quoted.

• It is easy to assemble complex components using automated layup machinery and rotational molding processes.

• Monocoque ('single-shell') molded structures deliver higher strength at much lower weight.

• Mechanical properties can be tailored by 'lay-up' design, with tapering thicknesses of reinforcing cloth and cloth orientation.

• Thermal stability of composites means they don't expand/contract excessively with change in temperature (for example a 90°F runway to -67°F at 35,000 feet in a matter of minutes).

• High impact resistance - Kevlar (Aramid) armor shields planes, too - for example, reducing accidental damage to the engine pylons which carry engine controls and fuel lines.

• High damage tolerance improves accident survivability.

• 'Galvanic' - electrical - corrosion problems which would occur when two dissimilar metals are in contact (particularly in humid marine environments) are avoided. (Here non-conductive fiberglass plays a roll.)

• Combination fatigue/corrosion problems are virtually eliminated.

Fiber metal laminates (FML) are a new type of composite developed at the Delft University of Technology. Thin sheets of aluminum are alternated with thin sheets of traditional composite. The first FML was Arall, a combination of aluminum and aramid/epoxy. Although the material showed promise, adoption by the aerospace industry was slow. In the 1980s, Delft began developing a glass/epoxy FML called GLARE. GLARE was intended to be an alternative to aluminum in aircraft structures. Early research showed it had benefits over both aluminum and fiberglass composites, especially in fatigue and impact. Development continued over a number of years, and the commercial breakthrough came when Airbus decided to use the material on the A380.

Glare was intended from the start to be a new aircraft material, and it is evident the developers knew what would be required to achieve certification. Analysis begins with the Metal Volume Fraction (MVF) method, similar to the rule of mixtures for traditional composites. Once basic material properties are determined, the analysis moves on to stress-strain, blunt notch, stability and fatigue beahvior. Each includes experimental data to supplement the theoretical coverage. Ample references provide the reader with additional sources of information.