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The Dream of Composites

Mon, 11/20/2006 - 6:24am
The use of composite material in Boeing’s 787 Dreamliner is benefiting manufacturing, the environment, and, ultimately, the entire air travel industry.

The 787 Dreamliner, being built by Boeing, Everett, Wash., is changing the face of air travel in more ways than one. Besides the new passenger-pleasing features like an improved interior environment, wider seats and aisles, and larger windows, the 787 Dreamliner is the first commercial jet ever to have the majority of its primary structure—including the tail, wing and fuselage—made of advanced composite materials.

Going composite
The Boeing 787 Dreamliner will consist of 50% composite materials.
Image: The Boeing Company.
Composite materials, or composites, are in a class of materials that includes glass, Kevlar, Spectra, Vectran, and carbon fiber, which are held in shape by a hardened resin like epoxy or bismaleimide. Today, one can find composites in cars, golf clubs, snowboards, and medical devices, in addition to aircraft. For its part, the 787 Dreamliner, will be composed of 50% composites, 20% aluminum, 15% titanium, 10% steel, and 5% other materials. Specifically, carbon fiber reinforced plastic (CFRP) will be the primary composite for the majority of the 787’s structure with titanium graphite composites also being integrated into the Dreamliner’s wings. In contrast, the Boeing 777 is comprised of 50% aluminum and only 12% composites. “Boeing has used composites on commercial secondary aircraft structure (like fairings) since the 707 era,” explains Alan Miller, director of Technology Integration for the 787 program. “Kevlar and carbon fiber began to be used later as the fiber for significant structure in satellites and high performance vehicles (both private and military).”

The power of composites
The 787 Dreamliner family consists of three aircraft: the 787-8, 787-9, and 787-3. The 787-8 is designed to carry 210 - 250 passengers over a range of 14,800 km - 15,700 km. The 787-9 is designed to carry 250 - 290 passengers over a range of 15,900 km – 16,300km. The 787-3 is designed to carry 290 - 330 passengers over a range of 5,500 km – 6,500 km. All are designed to fly at a speed of Mach 0.85, which is similar to that of today’s fastest widebody airplanes, such as the Boeing 777 and 747.

The use of composites in the 787 Dreamliner is bringing benefits to every stage of the aircraft’s life. “Starting with the design of the airplane, we can develop larger, more integrated structures because of the way composites are manufactured,” explains Miller. “In the build of the airplane, we will see significantly less waste, fewer hazardous materials, and shorter manufacturing cycle times.” The composite barrel fuselage section, for example, will be manufactured in one piece, resulting in 1,500 fewer aluminum sheets and 40,000 - 50,000 fewer fasteners being used. This represents an 80% reduction in fasteners over a non-composite barrel structure.

Moreover, the 787 Dreamliner series will be 30,000 - 40,000 pounds lighter than the comparably-sized Airbus A330-200. This will enable the 787 to use 20% less fuel, resulting in 20% fewer emissions. The lower weight will also result in up to 45% more cargo revenue capacity as well as cost savings for the airlines. “Airlines will see lower cost because of fewer repairs and lower landing fees, which are often based on weight,” says Miller.

Passengers on the 787 Dreamliner will also benefit from the use of composites. The typical air pressure in an airplane corresponds to an altitude of about 2.4 km. “In operation, the (composite) structure is more durable and does not corrode or fatigue like metals,” says Miller. “Passengers will be able to enjoy a lower cabin altitude and high humidity during their flights because of composites.” The Dreamliner will be pressurized to the equivalent of 1.8 km of altitude, leaving the passengers far less tired after flight.Indeed, in regards to performance, the use of composite materials seems to be a thing of beauty for the 787 project, with the majority of the challenges occurring in early stage manufacturing. “We’ve tested it and seen its in-service performance. The material is not a challenge at all,” explains Miller. “On the 787, our challenge has been the ability to design and manufacture large structures economically from the material. We worked diligently with our partners for many years to develop the methods and tools that are now allowing us to use this material system economically.”

Among the manufacturing challenges that Boeing encountered was a difficulty with one of the development barrels. “The team experimented with a different tool (mandrel) and production process,” explains Miller. “Unfortunately, the finished barrel was deemed unacceptable due to excessive porosity, which is basically trapped gas or air that is present in the fuselage material that shouldn’t be there. A team of experts determined the root cause was tool leakage. A recovery plan is in place using the previously proven production method.”

Boeing unveiled the first 787 Dreamliner composite fuselage section in January 2005 at its Developmental Center in Seattle, Wash. The section, made as part of the new airline development process, proves the manufacturing techniques that will be used for the first time with the airplane. Photo: Ken DeJarlais.
Collaborative manufacturing
Building such a revolutionary type of aircraft is drawing not only on Boeing’s expertise and resources but also that of other aviation/aerospace companies. Some of the composite sections of the 787 Dreamliner will be fabricated at the Composite Manufacturing Center (CMC) at Boeing Frederickson, Pierce County, Wash. CMC is responsible for designing the entire structure of the vertical wing, including composite and metal subcomponents. In September 2006, the fabrication of the first composite stringers for the vertical fin began at the CMC, and in spring 2007, the CMC will deliver the first fully functional vertical fin.

Spirit AeroSystems, Wichita, Kan., is building the Dreamliner’s entire forward fuselage. In August 2005, Boeing and Spirit AeroSystems unveiled the first all-composite demonstration nose section. “We have built several demonstration fuselage sections of the airplane at our facilities in Seattle,” says Mike Blair, VP and general manager of the 787 program at Boeing. “Our partners, including Spirit, have worked alongside Boeing personnel in Seattle so that we can all learn about the new methods of building aerostructure. It’s very rewarding to see the knowledge that was developed jointly by the global 787 team is being applied in the actual production facilities where the 787 will be manufactured.”

Triumph Composite Systems, Inc., Wayne, Pa., is providing the composite floor panel system for the 787 Dreamliner. In addition, Triumph has recently been selected by Saab Aerostructures, Linkoping, Sweden, to provide the 787 large cargo door actuation system and by Vought Aircraft Industries, Dallas Texas, to supply integrated kits which include composite ducting, machined metal parts and fittings, hydraulic tubing, insulation and other components.

Even the engines on a portion of the 787 fleet will be constructed using composites. China Eastern Airlines, Shanghai, has chosen the GEnx engine from GE-Aviation, Cincinnati, Ohio, for its 787 Dreamliner fleet. GEnx is the world’s only jet engine with a front fan case and fan blades made of composites. Composites give this engine greater durability, weight reduction, and lower operating cost. The blades are made with GE90 composite technology which has performed well with no routine on-wing maintenance required and which has had no service issues in more than a decade, according to GE. The fan contains only 18 blades, 50% fewer than GE’s CF6 engine and has noise levels lower than any large GE commercial engine.

Looking to the future
Boeing is not the only major airline using composites in its planes. Toulouse, France-based Airbus is using CFRP in its A380 and A350 planes.

The A380 is being built with 25% composite materials—22% CFRP and 3% GLARE, a fiber-metal laminate composite. The center wing-box that connects the A380’s wings to its fuselage will be made of these composites. But it will be the A350 XWB (extra wide body) which will serve as Airbus’ answer to Boeing’s 787 Dreamliner. This aircraft will be the first Airbus product with an all-composite wing, and it will also use composites in the rear fuselage and tail cone. The fuselage, however, will be built with an aluminum alloy as opposed to composites. All told, the A350 XWB will be composed of about 45% CFRP. Airbus expects to deliver the A380 in 2010 and the A350 XWB in 2012.

Currently there are 455 orders and commitments for the 787 Dreamliner from 36 airline and leasing customers around the world. Development is on schedule for the first 787 Dreamliner flight in 2007 and for their entry into service in 2008.

According to Blair, the use of composites in the 787 Dreamliner was a big step for Boeing to take, but one they believe will pay off. “We believe this choice will help position Boeing to take advantage of the most modern materials technologies as we enter the second century of flight.”

—Martha Walz
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