Aircraft Materials' Battle Heats up

Metals producers are fighting hard to regain market share in the aircraft business following the success of carbon-reinforced composites in the Boeing 787 Dreamliner.

One of the biggest developments comes from Alcan Engineered Products, which is introducing a new lightweight alloy that combines aluminum, copper, lithium, magnesium and silver alloy. Called AIRWARE™, the new alloy is said to exhibit high strength, high toughness and high corrosion resistance. According to Alcan, the new alloy also features high crack extension before unstable fracture of wide pre-cracked panels.

Alcan, a unit of Rio Tinto, rolled out the new alloy at the Farnsborough Air Show in England, where Boeing also flew the Dreamliner across the Atlantic Ocean for the first time.

Alcan Global ATI and Bombardier, a large aircraft manufacturer based in Quebec, have entered into a long-term agreement for the exclusive supply of AIRWARE to provide primary structure for the new CSeries aircraft. AIRWARE will comprise more than 20 percent of all materials used in the CSeries, which is now in the Detailed Design Phase (DDP).

Bombardier has begun releasing design datasets (drawings) to fabrication and production for the first ground and flight test aircraft. The aircraft is expected to commercially debut in 2013.

Built in China

The aluminum-lithium fuselage test barrel was built in China and has already successfully completed 60,000 fatigue cycles. The production fuselage for the CSeries will be built in Shenyang, China by Shenyang Aircraft Corp. (SAC), a subsidiary of the state-owned China Aviation Industry Corp. (AVIC).

Bombardier says the CSeries is the only modern aircraft specifically designed for the 100- to 149-seat market segment, and is already racking up significant orders.

Since the CSeries aircraft program was announced in 2008, Bombardier has received orders from Deutsche Lufthansa, Lease Corp. International and Republic Airways for a total of 33 CS100 and 57 CS300 aircraft. Options have been placed on a total of 90 additional CSeries aircraft.

Thanks to the use of the new-age aluminum, the pitch for the CSeries sounds a lot like the pitch for the Dreamliner: The aircraft will emit 20 percent less carbon dioxide and 50 percent less nitrogen oxide, fly four times quieter, and deliver significant energy savings - 20-percent fuel burn advantage, as well as 15-percent improved cash operating costs versus current in-production aircraft of similar size.

AIRWARE may have one significant advantage over carbon composites: recyclability of manufacturing waste.

Is it Recyclable?

According to Alcan, material removed during machining can be "infinitely" recycled into new aircraft parts, as can all components when an aircraft reaches the end of its commercial life. Boeing says it is working to develop commercial recycling processes for its composite waste, both for economic and environmental reasons.

Aluminum is not the only metal technology in greater play for aircraft applications.

Allegheny Technologies Inc. introduced its new titanium ATI 425^® Alloy to the commercial aerospace industry at this year's Farnborough International Air Show.

The titanium alloy's elements produce a material that can be hot or cold rolled and annealed to produce sheet with strength comparable to conventional pack-rolled titanium 6-4 sheet, but with improved formability due to higher room-temperature ductility.

ATI says that ATI 425 Alloy sheet can be produced with superior gauge control and improved surface finish, offering aircraft designers new opportunities for improving manufacturability and weight-saving potential.

A new magnesium technology also has promise. Sheet made in a liquid-forming process is said to provide 200 percent higher strength and improved toughness compared to conventional magnesium, while also providing the strength of carbon steel sheet at one-fourth the weight.

New Fasteners

Alcoa is developing new aluminum fasteners which have played a major role in the Dreamliner assembly, and is working on advanced hybrid structures at its technical center near Pittsburgh. Since Boeing launched the 787, Alcoa has developed three generations of aluminum lithium alloys.

"A few years ago, the industry consensus was that composites were the default material of choice," says Dan Goodman, director of marketing, Alcoa Aerospace. "That is no longer the case - particularly for narrow body aircraft. At a substantially reduced risk, proprietary aluminum alloys and new aluminum-lithium alloys offer improvements in weight savings and enhanced strength at a lower cost."

Alcoa and Commercial Aircraft Corp. of China are jointly exploring advanced aluminum structural concepts, designs and alloys to create a 190-seat aircraft, the C919. The aircraft will be assembled in Shanghai, but will source parts and components globally.

"The C919 will be the largest passenger jet to be produced in China," says Wu Guanghui, chief designer of the C919 program "Our goal is to design an efficient, high-performance structure that will compete in the global aerospace market." The C919 is expected to take its first flight in 2014 and enter service in 2016.

One of the outcomes of stress test issues with the composite wing on the Dreamliner was a decision by Mitsubishi Aircraft Corp. to switch from a composite to an aluminum wing on its the MRJ-21 regional jet. After weeks of delays and new design development, Boeing cleared the Dreamliner for flight.

Aluminum proponents such as Goodman also point to Lockheed Martin's choice of aluminum-lithium on the primary structures of the Orion spacecraft.