Aluminum remains relevant despite trend toward composites
Notwithstanding the unprecedented scale of composites content in the Boeing 787 and Airbus A350XWB airliners, aluminum still reigns as the material of choice in most airliner fuselage applications. At least that’s the message Alcoa–the aluminum company–wants to send here in Farnborough, where scores of examples of flying machines made of the metals the company supplies grace the static display.
Of course, the use of carbon-fiber products doesn’t preclude the use of aluminum and various other more exotic metals in the same airplane. Even what many consider an all-composite fuselage in the 787 uses thousands of highly specialized and expensive metallic fasteners made by Alcoa. In fact, according to Bill Christopher, Alcoa executive vice president and group president of the company’s Engineered Products & Solutions division, the dollar value of Alcoa’s contribution to the 787 virtually equals that of the aluminum-bodied 767.
Unfortunately, delays to the 787 and the A380 along with pressures such as inventory de-stocking and a collapse in the regional and business aircraft markets resulted in less demand for Alcoa’s aerospace products last year, when sales fell from $4 billion in 2008 to “just north of $3 billion.” However, the company’s financial position looks better this year, said Christopher. “If you look at the de-stocking on the jet engine side, that’s behind us; we’ve seen a pickup in the MRO, the replacement side of the business,” he added. “I think that de-stocking through that whole supply chain is done.”
Thankfully, the underlying fundamentals of the large commercial aircraft business “held up very well” all along, said Christopher, and Alcoa remains bullish about its prospects for the next two to three years, as manufacturers proceed with planned build rate increases and the 787 and A380 programs “ramp up to run rates.” Still, he said, “it will be later this year, early next year before we start to see any significant activity back there again.”
Three years ago Alcoa had just finished adding sheet and plate capacity at its Global Rolled Products division mills in Davenport, Iowa; Kitts Green, UK; Fusina, Italy; and Belaya Kalitva, Russia. The additions accounted for some 50 percent capacity expansion. Today, not only Alcoa, but the entire industry faces an overcapacity situation, particularly on the plate side, [but] “less so on extrusions,” said Christopher. “[In terms of] fasteners and airfoils, there’s some excess capacity but not nearly to the same extent, and most of that is driven just by business jet and regional jet demand.”
About half of the company’s portfolio consists of its traditional aluminum structural businesses it started a century ago. The other half consists of its Howmet jet-engine investment castings unit and its Alcoa Fastening Systems (AFS) division.
Although Christopher wouldn’t reveal what proportion of Alcoa Aerospace’s revenue now comes from proprietary products, the company clearly has moved away from commodity markets and into proprietary technology. In 2004, proprietary products accounted for 12 percent of Alcoa’s aerospace revenue; in 2007 that share rose to more than 20 percent.
“If you ask what holds together a portfolio of jet engine parts, fastening systems and sheet, plate and extrusions for aluminum structures, it is technology,” said Christopher. “We look at each individual segment, we want highly complex applications where, in fact, we expect mission requirements to increase demands on the product, which allows us to develop technologies that solve customer problems.”
Christopher explained that the economic rationale for replacing equipment lies more firmly today with the cost savings that come with technology improvements than with direct acquisition cost savings the OEMs sought for earlier projects. The resulting demand for more sophisticated materials plays directly to Alcoa’s strengths. “Overall, it is clearly what we drive for, whether it’s proprietary, highly differentiated, a combination of technology or know-how or special dimensional characteristics,” he said. “And that really represents the core of all three segments of what we have.
“For the next five or six years we’re going to go through a renaissance in the industry, where you have all new platforms being run out,” Christopher predicted. “By 2020 you’re going to be talking about everything from twin-aisles to your super jumbo jets all being brand-new platforms.”
The next “battle ground,” according to Christopher, will involve the single-aisle segment, where Alcoa believes its metallic products will prove superior
to composites. Since Boeing launched the 787, Alcoa has developed three generations of aluminum lithium alloys, he said. Stronger than traditional aluminum, aluminum-lithium allows manufacturers to use thinner and, hence, lighter fuselage skins.
Another area in which Alcoa believes it can compete with composites on weight involves so-called selective reinforcement, a concept that centers on strengthening certain fuselage points with hybrid material. “We’re now starting to look at single-aisle applications and saying we think that there’s anywhere between a 3-percent and 14-percent improvement on weight that can be delivered [with selective reinforcement],” said Christopher.
Whether or not aluminum- lithium or structural reinforcement technologies find their way onto new narrowbodies might well depend on the partnerships Alcoa manages to forge with OEMs. In fact, the company last year signed a strategic partnership agreement with Comac to help the Chinese company decide on what materials to use on the C919–the new 170- to 190-seat narrowbody scheduled for market introduction in 2016. “We have a full team of people working with their design people on really putting forth our best technologies in the design of that aircraft, from both a fastener perspective and an aluminum structures perspective,” said Christopher.
Of course, Alcoa has shown intense interest in the narrowbody strategies of Boeing and Airbus as well, along with the fortunes of the A380 and 747-8. The A380 alone consumes nine times the metal and alloys required by today’s 737 and A320. The largest supplier to the A380 program, Alcoa provides forgings, extrusions, sheet, plate and castings for the superjumbo’s wing and fuselage skins, along with stringers, frames, spars, gear ribs, engine and pylon supports, seat tracks and floor beams.
The AFS division has developed multi-material lock bolts for the assembly of the big jet’s wing box and new-generation blind bolts tailored for the program’s robotic assembly techniques. Each A380 uses about one million Alcoa fasteners.
“When you look at the prospects right now, the 747-8 and A380 [are] both metallic aircraft. They’re not going to change for 25 years,” said Christopher. “You’ve got the single aisles…obviously their lifespan is going to be longer than what everybody expected and we think we have incredibly competitive alternatives for them– especially given a single-aisle mission–that would provide them weight advantage and give them a lot more experience and predictability in both their design and their launch costs.”
Alcoa (Hall 1 Stand A9) can effect further weight savings by replacing titanium with advanced aluminum alloys. “Our fundamental belief is if you had a choice between aluminum and titanium, obviously you’re going to pick aluminum because it machines faster and it’s lighter,” said Christopher. “But then you’re trading off, in certain cases, strength” as well as titanium’s resistance to expansion at high temperatures. “The coefficient of thermal expansion between aluminum and composites unfortunately is very different,” he noted. “So there are places you just can’t put them together because, as the plane heats up or cools off, you’re going to end up with structural issues. So that’s part of the barrier that we face there.”