Since the birth of aviation, designers have continuously endeavored to improve the lift to weight ratios of aircrafts.
An increasingly important innovation in the aerospace industry is the use of composite materials, as these enable designers to overcome the barriers created by using metals.
Composite materials have played a major role in weight reduction, and hence they are used for both structural applications and components of all spacecraft and aircraft from gliders and hot air balloon gondolas to fighter planes, space shuttle and passenger airliners.
Composites are essentially materials made up of 2 or more phases or constituent parts, predominantly plastics reinforced with carbon fibers.
They can be formed into various shapes to increase their strength and layered with fibers running in a different directions, to allow designers to form structures with unique properties.
The development of next generation composite materials with light-weight and high-temperature resistance will help in designing high-performance, economical aircrafts.
A Brief History Of Composite Materials in Aerospace
Fiberglass consisting of glass fibers embedded in a resin matrix is the most common composite material, and first came to prominence in the 1950s for designing Boeing 707 passenger jet.
Compressor blades of the RB211 jet engine developed by Rolls Royce in 1960s were made of carbon fiber, which is brittle and has unique fatigue behavior.
Fibrous composite materials were originally used in small amounts in military aircraft in the 1960s and within civil aviation from the 1970s.
Since the 1980s composites have primarily been used for secondary wing and tail components such as wing trailing edge panels and rudders.
Each generation of new aircraft developed by Boeing has had an increased percentage of composite material, with the highest being 50% in Boeing 787 Dreamliner. The major structural elements of Boeing's 787 Dreamliner are made of more carbon 'sandwich' composites and advanced carbon laminate, a shift away from archaic fiberglass composites.
Aramid fibers, on the other hand, are widely used for constructing leading and trailing edge wing components and very stiff, very light bulkhead, fuel tanks and floors.
Advanced composites consisting of a combination of high-strength stiff fibers embedded in a common matrix material are also widely being used in the aerospace industry.
Advantages of Composites Usage in Aerospace
Some of the key benefits of using composites for aerospace applications include the following:
- Weight reduction up to 20 to 50%.
- Single-shell molded structures provide higher strength at lower weight.
- High impact resistance. For instance, Kevlar (aramid) armor shields planes have reduced accidental damage to the engine pylons that carry fuel lines and engine controls.
- High thermal stability
- Resistant to fatigue/corrosion
- Structural components made of composite materials are easy to assemble.
Composite Aircrafts and the Environment
Recycling used parts from decommissioned aircrafts is another option available when using aerospace composites.
The Boeing Company is particularly involved in improving the environmental performance of the airplanes by adopting recycling of all the aircraft materials manufactured using composites.
The recycling of composites is a two-step process that involves separating composites from other aircraft materials during an aircraft’s retirement and recovering good quality fibers to be re-introduced as a materials source in aerospace manufacturing.
>Although recycling of an aircraft structure is a complex and expensive process, it may save money in purchasing expensive first-hand parts.
The Future of Composites in Aerospace
With increasing fuel costs, commercial aerospace manufacturers are under pressure to enhance the performance of aircrafts, for which weight reduction is a key factor.
Based on the progress that is being made in composite construction techniques, it is very likely that the airplane of tomorrow will be manufactured using composite materials.
However, there are still some hurdles to overcome before composites can replace aluminum and other metal alloys completely, particularly in case of large airplanes.
For one, composites are expensive and require a large labor force plus complex and expensive fabrication machines.
Composite technology continues to advance, and the invention of new types of composites such as carbon nanotubes and basalt forms will further accelerate composite usage.
Sources and Further Reading