Paris 2011: Alcoa ups the ante against composites
Aluminum giant Alcoa (H5 F220) is here exhibiting a fuselage section manufactured with advanced aluminum-lithium alloy sheet that was stretch-formed on existing tooling by Spirit Aerosystems’ factory in Wichita, Kansas. U.S.-based Alcoa is targeting the next generation of single-aisle aircraft (with a clear focus on Boeing’s expected decision this year) as the potential first applications. It is touting the merits of new-technology metals against composites–lower weight, better fuel efficiency, reduced cost and less risks in production–promised for aircraft entering into service before 2020.
“We learned the hard way that we did not innovate enough,” Kevin Lowery, communications director for Alcoa’s global rolled products, told AIN. He was referring to the decisions by Boeing and then Airbus to dramatically increase the proportion of composite materials on their new widebody programs–respectively, the 787 and the A350 XWB. After this wake-up call, research and development in aluminum has accelerated over the past decade, notably at Alcoa’s research center in Pittsburgh, Pennsylvania.
According to Tony Morales, global marketing director for aerospace aluminum, the empty weight of rolled products, with Alcoa’s new alloys, will be cut by six to 10 percent. The starting point for this is the new material’s lower density, 3 to 7 percent below that of today’s metals. On top of that, Alcoa engineers have devised ways to add structural reinforcements only where they are really needed. Also, thanks to better crack propagation resistance, some parts can be made thinner and lighter.
Other improvements have further helped to fuel consumption for aircraft. First, applying these new design approaches (including the more precisely located reinforcements) allow Alcoa to achieve more aerodynamic geometries, such as a higher wing aspect ratio.
Alcoa also is working on longer-term wing skin technologies, targeting lower drag. Reduced skin friction holds a potential 3- to 6-percent enhancement. All told, the company predicts that fuel burn in the next generation of narrowbodies could be 7 to 12 percent better than current performance, thanks to the new metallic materials and advanced structural technologies. This does not take into account progress in engine technology.
As for passenger comfort on the 787, Boeing has said that composites allow for larger windows. Thanks to the more precisely located reinforcements on the fuselage, Alcoa is able to offer equivalent improvements using metal, according to Lowery. In terms of cabin pressurization and moisture levels, Alcoa also now claims to be on an equal footing with composites. For example, the new alloys can take 6,000 feet in cabin pressure at cruise altitude.
In the area of maintenance, a third-generation, more corrosion-resistant aluminum-lithium alloy can be inspected at intervals twice as long as before. Another factor is greater fatigue performance. Separately, a self-cleaning metal sheet is in early development. Thanks to millimeter-scale geometry features and coatings, the metal sheet essentially repels dirt.
In production terms, Alcoa claims its solutions to be up to 30 percent cheaper, and much less risky, than composites. The company says it can ensure more timely deliveries as a result of having “established high-volume supply chains and reduced investment needs via existing infrastructure.” It also stresses the ability to recycle aluminum.
So how successful will Alcoa be in convincing manufacturers to adopt its new solutions? Time will tell. To begin with, the firm conducted a survey to assess aluminum perception. It showed that nearly three out of four of the technical respondents surveyed had a favorable perception of aluminum as a primary structure material, as opposed to 54 percent for composites. Among management and commercial constituencies, the results showed the opposite. “The better the survey interviewees understand aluminum, the more they are favorable to it,” reported Alcoa.
Aerospace accounts for roughly 10 percent of Alcoa’s $30 billion annual revenues.