Plastics play an integral role in the aerospace industry. Used in many parts and components both inside and outside aircrafts, especially airplanes and helicopters, plastics are deployed in aerospace applications for numerous reasons:
1. Plastics weigh less than metal – Reducing weight helps aircraft operators save on operational costs; lighter flights mean less fuel consumption.
2. Plastic parts are more durable and require less maintenance than other materials – Plastics do not rust and there are many plastic material grades that are flame, heat release, smoke and toxicity compliant.
3. Plastics are easy to fabricate – Plastics offer design flexibility in terms of colours, patterns, shapes and textures.
Applications of polymers in aerospace engineering
Many plastic innovations are used in aerospace, with some of them pioneered around World War II. One example goes back to 1933 when Plexiglas, a transparent acrylic plastic, was introduced in Germany and used for aircraft windshields and bubble canopies, resulting in weight reductions and better all-round visibility for fighter pilots. Still in use today on most fighter aircraft, the majority of modern acrylic canopies are vacuum formed.
English ophthalmologist Sir Harold Ridley discovered that World War II airplane pilots whose eyes were damaged by flying shards of acrylic fared much better than those injured by standard glass. This demonstrated better compatibility between human tissue and acrylic than with glass. Civilian applications, such as lenses, followed after the end of the war.
Acrylic bubble canopies were used on aircraft such as the Supermarine Spitfire and Westland Whirlwind.
In the late 1980s, thermoplastic sheet material was first used to form aircraft flooring via thermofolding. Floor panels of glass-reinforced polyetherimide (PEI) and carbon-reinforced PEI sheet material were thermofolded 90° downward at the edges to produce durable and low-cost edge closeouts.
Carbon fibre-reinforced PEI was used for floor panels in the Gulfstream G400 and G500 business jets as well as the Airbus Beluga transport aircraft, while glass-reinforced PEI was used in Fokker 100 aircraft cargo flooring (High-Performance Composites, March/April 1999, p. 32).
Today, carbon fibre-reinforced plastics, glass fibre-reinforced plastics and quartz fibre-reinforced plastics are used extensively in airplane doors, ceiling beams, fuselage sections (such as the undercarriage and rear end of fuselage), wings, horizontal stabilisers, fin and tail surfaces.
Nylon 6/6, 6/12 and acetal are routinely used as brackets, fasteners, grommets, rub strips and wear surfaces. Some of these parts and components are injection moulded, while many are machined from stock shapes.
Spacers used in aircraft thrust reverser assemblies are one application where polyamide-imide (PAI) is used due to its heat resistance and dimensional stability.
Other engineering plastic materials like polyphenylene sulfide (PPS) and polyetheretherketone (PEEK) offer chemical resistance to hydraulic fluids and aircraft fuels as well as outstanding physical properties in comparison with metals. High-end materials such as PAI, polybenzimidazole (PBI) and polyimide (PI) provide similar protection against fluids with good strength and even higher temperature resistance.
22% of the world’s largest commercial aircraft, the Airbus A380, is made of engineering plastics.
Another application example of engineering plastics in aircrafts are pivot bushings. Advanced materials like those listed above have various fillers added to the base polymer in order to increase load bearing capabilities and reduce wear. Hinge bushings in cabin and exit doors, aircraft flaps, handles and video arms can benefit from the impact resistance, self-lubrication, and in the case of interior systems, flame resistance of machinable engineering plastics.
22% of the Airbus A380, the world’s largest commercial aircraft, is built from carbon-reinforced plastics (New Scientist). This helps to reduce fuel burn to rates comparable to those of an economical family car (BPF). The Airbus A380 is also the first commercial airliner to have a central wing box made of carbon fibre-reinforced plastics.
The fuselage of the Boeing 787 Dreamliner is made from three plastic composite sections. This serves to reduce fuel burn by as much as 20% (BPF). Spaceship One, the first private spaceship to fly into terrestrial orbit, made extensive use of carbon fibre reinforced plastics to escape gravity by keeping the weight low.
Supplier of polymers used in aircraft
In many cases, only a handful of parts are used on a single aircraft. This makes it ideal for them to be machined from stock shapes. The low volume nature of aircraft production means that machining parts from stock shapes are often more cost-effective than moulding them.
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