Look for an accelerating battle among materials suppliers to win acceptance for the next generation of single-aisle aircraft being developed by Boeing and Airbus.
Pittsburgh-based aluminum giant Alcoa fired a new volley with an announcement that it has developed alloys which, it says:
- Provide up to 10 percent in weight savings over composite-intensive planes
- Lower the cost to manufacture, operate, and repair planes by up to 30 percent compared to composite-intensive planes
- Allow for a 12 percent increase in fuel efficiency
- Deliver passenger comfort features equivalent to composite-intensive planes, such as higher cabin pressure, large windows, and higher humidity
"The decisions made in the past decade to build the first composite-intensive aircraft were a huge wake-up call for us," said Mick Wallis, president of Alcoa North American Rolled Products, in a press release. He is responsible for Alcoa’s aerospace sheet and plate products. "In hindsight it was the right decision for the time -- when advanced aluminum solutions were not as developed -- but our technology solutions have made quantum leaps since those decisions."
The new metals include third-generation aluminum-lithium alloys that are said to result in up to 7 percent lower density in major structural applications along with better corrosion resistance.
The new alloys signal that Alcoa will not cede any ground to the use of carbon-reinforced plastic, which made a breakthrough on the Boeing 787 Dreamliner. Deliveries on that plane are running three years late because of a variety of problems, including technology and design issues related to composites, which represent about half of the materials used in the Dreamliner.
Industry insiders say the new, improved aluminum alloys stand an excellent chance of widespread use on next-generation single-aisle aircraft.
The case for the still-lighter composites diminishes on smaller aircraft with shorter routes. Aircraft engineers at Boeing, Airbus, and elsewhere will also take into account potential damage on short-run flights. Single-aisle aircraft take off and land more frequently than large planes, and can take a beating.
Alcoa says aluminum has more damage tolerance than carbon composites. It's also possible to more easily see damage in aluminum. The improved corrosion resistance in the new alloys tackles one of the big selling points for carbon composites: They require frequent inspection interval cycles. The precise difference in inspection intervals is not yet clear because of the new technologies just announced.
Alcoa is also developing new structural concepts, such as selective reinforcement. In this approach, aluminum-lithium sheet reinforced with glass fibers is placed in specific areas that need to be strengthened.
Additional improvements are coming in composites technology, but the most important developments are being kept top secret by the aircraft manufacturers. The focus is on processing speed. There's no question about the strength and quality of the composite. But processing of the thermoset resin is time consuming. Efforts are underway to automate processes where possible.
Several examples of processing innovation are on display this week at the Paris Air Show. For example, Advanced Composites Group is showing its composites technology for aerospace structures that do not require autoclaves for curing. The company's MTM44-1 toughened epoxy matrix resin prepreg will be used for the wing panels on the Airbus A350 XWB aircraft. That will be the first use of out-of-autoclave processing in a commercial aircraft structure.
CGTech is showing Vericut software for automated fiber placement (AFP) programming and simulation at the giant aircraft trade fair.