Raymond Pace, worldwide marketing director for Saint-Gobain Performance Plastics, Process Systems Business Unit, looks into the materials used in the development of the new generation of lightweight, fuel-efficient aircraft
From the outside, a Boeing 707 built in the 1950s may not look drastically different from the more recent iterations of this design. But, the variances are much closer to the surface than one may think.
Much has evolved in aircraft engineering over half a century. Some changes are noticeable – such as interior alterations to accommodate more passengers in the same or less space, or the individual entertainment units embedded in the back of each headrest. Some of the most radical revisions aren’t, however, even visible to passengers, even though they span a wide range of applications. These include the use of new or advanced materials in everything from the floorboards and window gaskets to the rudders and wings.
As the cost of oil has risen, demand for more fuel-efficient airplanes has increased, driving the industry’s manufacturers to seek out solutions for building lighter aircraft. Increasing consumer concern for the environment and demand for more eco-friendly transportation are also prompting aircraft manufacturers to leverage materials that will make airplanes lighter, more fuel efficient and less costly to operate.
To achieve these goals, manufacturers have increasingly used lightweight composites to replace the monometals characteristic of earlier planes. In fact, a report by Visiongain entitled “The Composites Market 2012-2022: Glass Fibre, Carbon Fibre & Aramid Fibre” predicted that the composites market would continue to grow as demand for lightweight, fuel-efficient aircraft and other transportation technologies remains strong.
Composites
The use of composite materials isn’t new to the aerospace industry. Before the trend toward reducing weight gave composites a new purpose, carbon fibre, polymer and hybrid materials had been – and continue to be – integrated throughout aircraft in interior finishes, floor beams, stabilisers and many other areas. The inherent performance properties of composites, such as durability, corrosion resistance and friction-reduction make them perfect in general for use in protective coatings and seals as well as window and door gaskets.
Seals are crucial to operation, and are used in some of the most important parts of the aircraft. Depending on the use, the seals must be able to withstand a variety of conditions, ranging from high pressures and temperatures to chemical degradation and erosion.
When developing a seal for a given application, especially when complex performance requirements apply, the best options available are often engineered solutions that include fabric reinforcement or a compound of several materials with different properties. An engineered solution can be customised for different applications to improve performance. For example, seals for wing flaps need to be resistant to corrosion, and so coatings or protective materials can be added to the composite that safeguard the seals. Other layers may be added to provide extra protection against wear and abrasion from airflow.
Composite materials are also used in window and door gaskets on airplanes for the purposes of ensuring safety. The air quality inside the cabins is carefully managed to provide a comfortable atmosphere for passengers, and to protect this air quality window and door gaskets must prevent any potential leaks and guarantee that all doors and windows are securely closed. Therefore, materials for these applications should be tailored to each use to ensure the best possible performance.
As demand for better fuel economy drives the weight-reduction trend to new frontiers, composites will remain at the front and centre of innovation. As forecasted in the Visiongain report, demand for more sophisticated composites is escalating around the world and it is creating new opportunities to expand applications of composites – specifically in the development of lightweight materials. As a result, new uses are being found for materials such as fluoropolymers, which can enable the production of lightweight composites.
Fluoropolymers possess friction-reducing properties and the ability to prevent the corrosion of metal substrates, meaning they are ideal for use in protective coatings and seals. This is why they are already familiar to the aerospace and automotive industries.
In airplanes, fluoropolymers are often used in wire harnesses which run throughout planes to protect electric wiring and provide a flame-retardant barrier in the event that a damaged wire sparks.
Besides use in cable jackets and seals, there’s an even wider array of possibilities for fluoropolymers on the horizon of aircraft design. Due to the exceptional and inherent strength of these materials, manufacturers of commercial and military planes alike are considering the use of lightweight fluoropolymers during the design of the aircraft fuselage. Such applications could both enhance the efficiency of the manufacturing process and offer new opportunities for even more dramatic reductions in weight.
Driving forces
These and other advancements will continue to drive aerospace industry players closer to achieving their weight-reduction goals; and as the price of oil increases and consumers become more environmentally conscious, there may be no end to this pursuit.
Manufacturers continue to meet industry demand for greater fuel efficiency, enhancing aircraft with lightweight composites, driving the industry-wide material evolution and delivering the next generation of advanced, fuel-efficient planes.
St Gobain Performance Plastics
