Before thousands of spectators at the world's largest air show, Airbus SAS introduced its newest airliner, the A350 XWB. The twin-engine wide-body flew over Le Bourget Airport in Paris earlier today, one week after its maiden flight. Airbus has secured more than 600 orders for three versions of the aircraft, according to company documents.
Beneath the blue and white company livery, the A350's airframe is composed of 72 percent lightweight materials like aluminum and titanium alloys. The most important material, however, is carbon fiber reinforced polymer, making up more than 53 percent of the airframe.
The increase in lightweight components in aircraft signals how commercial aviation targets have shifted from larger, farther, faster to cheaper, quieter, more efficient. Though the materials themselves are not new, the technology and the commercial demand for them have recently aligned. That makes advanced materials like carbon fiber essential to staking out a competitive edge in an international arena.
The A350 will go toe to toe with Boeing Co.'s incumbent 787 Dreamliner, already in service with nine airlines. Like the A350, the 787 also uses substantial amounts of carbon fiber in its airframe to enhance fuel economy and cut operating costs for airlines.
The material is making inroads into other sectors as well. Stronger, stiffer and more durable than most metals and at a fraction of the weight, carbon fiber enables a suite of energy-efficient and clean technologies from wind turbines to cars in an era of turbulent energy prices and a changing climate.
Now governments around the world are vying for a stake in the global carbon fiber market. The United States in particular is aiming to retake the lead it once held in advanced materials, playing to its strengths in research and development.
An American company, Union Carbide, initially developed carbon-fiber-reinforced polymers in 1958, but today China, Japan and Europe manufacture the vast majority of this material.
Trying to recover a U.S. lead
As part of a new manufacturing initiative to boost U.S. competitiveness through the clean energy sector, the Department of Energy launched a state-of-the-art carbon fiber technology facility earlier this year at the Oak Ridge National Laboratory in Tennessee. The facility, supported by a $35 million DOE grant, will serve as a testbed for the development of cheaper, better-performing carbon fiber materials.
"We've really lost the technology. Part of our vision here is we're going to take it back," said Lee McGetrick, director of the Oak Ridge carbon fiber technology facility.
More than 90 percent of carbon fibers use the petroleum-based precursor polyacrylonitrile, or PAN, as their raw material. But converting PAN into carbon fibers is a slow, energy-consuming process requiring high temperatures and strict environmental controls. According to McGetrick, sourcing and producing PAN makes up about half the cost of the final carbon fiber product.
To bring down costs, Oak Ridge is looking to scale up production of two cheaper carbon fiber precursors: polyolefins and lignins. Polyolefins are plastic materials that could one day come from recycled products like water bottles or baby diapers. Lignins are bio-based materials and natural byproducts of pulp and paper mills as well as the biofuels industry.
However, harnessing these fiber sources is challenging. "In most studies, they have reported lignin is a very tough material to make into fine fibers," said Mahendra Thunga, a postdoctoral researcher at Iowa State University who researches carbon fiber. "The finer the carbon fiber, the more strength you have. Getting a fine fiber is very critical with lignin."
Nonetheless, proving the viability of carbon fibers from various waste streams would bring down overall costs, while bolstering the U.S. carbon fiber market and industries supplying it.
"Today's carbon fiber industry is really a boutique industry. By proving you can do it at a low cost at scale, we're trying to turn it into a big box store kind of industry, and that could really be a boon for the United States in manufacturing," McGetrick said.
Slashing fuel costs
There is already a huge demand for these boutique products. In commercial aviation, the push for lightweight materials came from fuel price concerns. Global oil shocks in the '70s spurred the airline industry to look for ways to increase fuel efficiency without compromising performance. "That didn't really come from us," said Roland Thévenin, senior composites expert at Airbus. "It was required from our customers."
The company experimented with different carbon fiber components like bulkheads and spars, gradually replacing more and more metal structural components with composites, Thévenin explained. Their first primary part made from composites, the vertical stabilizer in the A310, took wing in 1985. The new A350 has individual carbon fiber parts, such as the A350-900 outer wing box, as large as 32 meters by 6 meters. "What we're doing is an evolution [for each new program], not an evolution," he said.
Carbon fiber coupled with other efficiency measures in the A350 yields a 25 percent improvement in fuel economy over comparable aircraft without such advances. Similar strategies in the 787, which is 50 percent carbon fiber, reduce fuel use by 20 percent compared to competing designs.
However, composites are only part of the story. Scott Lefeber of Boeing's 787 communications team said in an email that for the fuel advantage in the Dreamliner,3 percent comes from materials like composites, 3 percent from systems, 3 percent from improved aerodynamics and 8 percent from better engines. Similarly, Airbus attributes the A350'S fuel savings in equal portions to reduced weight, aerodynamic upgrades and fuel-efficient turbines.
Though carbon fiber parts and efficient engines are already flying on some aircraft on the market, engineers needed a new aircraft to completely capture the efficiency from these upgrades. "For example, the engines are more efficient so the wing doesn't need to carry as much fuel so the wing can get smaller. When the wing gets smaller, the engine can get a little smaller," Lefeber said. "The full benefit of the technology improvements can only be reached with an all-new design."
The savings extend beyond lower fuel costs. Carbon fiber is more durable than metal in a similar role since it doesn't corrode or fatigue as easily, so maintenance will be cheaper over the plane's lifetime. Conventional metal-based aircraft like the Boeing 767 or the Airbus A330 have a service life of 30 years but require a second major structural inspection after 12 years in operation.
"This means that at age 12, a metallic airplane's best years are behind it in terms of maintenance costs," Lefeber said. "The 787 will not undergo its second heavy check until it is 24 years old; the benefit of this to the 787 operator cannot be overstated."
Renewable energy also stands to benefit from advanced materials. In wind turbines, carbon fiber's stiffness means rotors can use longer blades, thereby increasing the efficiency of each individual generator. "The amount of energy captured by the machine goes up with the square of the rotor diameter," explained Joshua Paquette, a principal member of the technical staff at Sandia National Laboratories. "Carbon offers a great opportunity for wind turbine blades in that you can increase the strength by a factor of 10 and stiffness by a factor of four for the same weight."
However, there are still some barriers before carbon fiber becomes as common in airliners and minivans as it is in race cars and fighter jets.
Stiff competition for a stiff material
"The biggest hurdles are cost, throughput and recycling," said Ross Kozarsky, senior analyst at Lux Research, a technology research and advisory firm. This is especially important to the automotive sector, both consumer and commercial, where reducing an automobile's weight by 10 percent yields a 6 to 8 percent fuel efficiency improvement, according to DOE.
Because the industry is so large, trends in making cars can ripple through other segments of the economy, especially when it comes to materials.
In addition, the market for cars, trucks and buses is very sensitive to price, so even a tiny cost increase has to have a substantial payoff in terms of efficiency, Kozarsky explained. Automobile turnover is also much faster than it is for aircraft, so manufacturers have to design and fabricate new carbon fiber parts on very large scales year after year, a tedious and expensive process. On a factory floor, workers will have to prepare thousands of components daily. "The processing time for the part probably needs to come down below one minute," he said.
Automakers are evaluating alternatives as well. "Carbon fiber is not operating in a vacuum," Kozarsky added. Other materials, like magnesium, aluminum and titanium, are comparable to carbon fiber in certain roles with the added benefits of lower costs, larger production scales and quicker manufacturing.
As a result, "carbon fiber is likely to be somewhat of a niche player," said Kevin Lowery, director of corporate communications at the aluminum company Alcoa Inc. "Sure, you're going to see it win a piece of an application here and a piece of an application there. But is it the first thing people will jump to when they think about building a vehicle? It probably won't."
At the other end of the equation, there are concerns about recycling. According to Alcoa, 95 percent of the aluminum used in a car gets recycled. Steel also has a high recycling rate. Carbon fiber, by contrast, can't be melted down and is very difficult to reuse. BMW Group and Boeing established an agreement last year to pioneer ways to reclaim carbon fiber parts at the end of their useful life, but today most carbon fiber ends up in a landfill.
Industrial experience is another factor in carbon fiber proliferation. People have built cars out of steel and aluminum for 100 years and know how to use those materials, Lowery said. Manufacturers will need to invest more in workforce development around carbon fiber technology before it becomes viable.
Oak Ridge's McGetrick said it would take at least five to 10 years for these cheaper carbon fibers to hit the mainstream automotive sector. But, ultimately, "we think that there's a potential market explosion," she said.
Other countries seem to think so as well. "You have big materials players on every continent," Kozarsky said. "We are starting to see a lot of activity in China for carbon fiber."
In the next generation of carbon fiber composites, there will be stiff competition.
Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500
