Aluminium's Enduring Role in Lightweight Aviation

The aviation industry continues its quest to lightweight aircraft to meet the needs of rapidly evolving trends.
6 January, 2016
Aluminium that made flight possible from the beginning remains at the core of today's solutions.
The next generation of aircraft are expected to begin flying by 2030, and they'll be meeting the needs of 16 billion passengers per year by 2050, according to industry trade leader Iata. Another 400 million tons of cargo are anticipated by then, all within the constraints of the global plan to reduce carbon emissions in the fight to limit the worst impacts of climate change.

So lightweight materials like aluminium and carbon composites are more important than ever, but they're helped along by other innovations. Nanotechnology has created a revolution in materials that delivers optimized structures that are half the weight they were 40 years ago, in systems that include everything from windows and ovens to toilets. Recycling advances mean that virtually all airplane interiors are made with recyclable materials. Cultural trends in tech are making a difference too: Passengers bring devices, so aircraft are rarely fitted with in-flight entertainment systems anymore.
In aviation, lightweight materials make up 80 percent of all materials, and aluminium used in the structural parts is the most important component, accounting for 50 percent of the plane's inputs. More carbon composites are expected in the future, and that's true in an automotive sector just as keen for light weights, as in energy and other fields. The cost difference is expected to drop, for example, in automotive manufacturing but carbon fiber products will still cost 25 to 30 percent more, and questions remain about whether the amount of energy used in mass producing them yields a negative benefit.
The Boeing 787 Dreamliner, which relies on carbon composites for about 50 percent of its total weight, still contains a significant amount of aluminium – and growth is expected in the aviation sector for both materials. In forecasting for 2030 when compared with 2010, McKinsey sees carbon fiber in aircraft to go from 9 to 16 percent of total construction, while aluminium drops by a comparable amount – but the overall share of all lightweight materials in the total aircraft manufacturing increases by 7 percent too. That leap is almost 40 percent in automotive, where aluminium and high-strength steel take off by 2030.

Image: Wikipedia
For those aviation take-offs, though, even some companies that consider carbon composites still choose aluminium. The Airbus 380 contains 10 times the aluminium that the Airbus 320 did, and that's in one of the world's largest passenger aircraft. It's also true for Mitsubishi, where engineers initially planned for composite wings on a regional jet design. The company stayed with aluminium because it served as a better overall solution – and this, from a company that actually supplies composites to commercial aircraft manufacturers. The aluminium also is preferred for military aircraft like the J-35 Joint Strike Fighter, where it is used in the six forged bulkheads that make up the weight-bearing frame.
Image: Wikipedia
Comparatively, the carbon composites are valued for their high strength-to-weight and stiffness-to-weight ratios, and can deliver the strength and stiffness properties of steel with between 40 to 70 percent weight savings. Yet they also have their disadvantages beyond cost: They tend to be brittle, unyielding and offer low impact resistance.

The most common aluminium alloy in aerospace contains about 6 percent zinc with smaller amounts of magnesium and copper, and offers the strength of steel with flexibility in its applications. New high-strength aluminium alloys continue to be developed, and promise to deliver lightweighting improvements for aviation and other industries well into the future.
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