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May 2007
Boeing 787 Update

Approaching rollout and first flight, the 787 relies on innovations in composite materials and processes to hit its targets

Posted on: 5/1/2007
High-Performance Composites

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The 787's First Horizontal Stabilizer

Source: The Boeing Co. The 787’s first horizontal stabilizer is delivered to Boeing in Seattle on April 24, aboard Boeing’s Dreamlifter freighter. Manufactured by Alenia Aeronautica at its facility in Foggia, Italy, the stabilizer is transported in five pieces, the left and right stabilizer, two elevators and a center section. When completed, the assembly has a wingspan of 62 ft/18.9m and measures 32 ft/9.75m, fore to aft.

The 787 Dreamliner, The Boeing Co.’s (Seattle, Wash.) and commercial aviation’s fastest-selling passenger aircraft ever, corralled order number 567 in April. The plane maker says 2006 revenues increased 15 percent from 2005 — up 26 percent in the fourth quarter alone. In 2006, Boeing captured 73 percent of the twin-aisle market and 61 percent of the overall market.

Few observers now doubt that this unprecedented success has much to do with the plane’s composite-intensive design. At 50 percent composites, by weight, the 787 is in a class by itself. According to Boeing, the advantages of significantly increased use of composites go beyond the more obvious weight/economy benefits. Greater cabin pressure, larger windows, less corrosion and extended maintenance schedules were key drivers in the 787 design — each very appealing to Boeing’s airline customers.

With the aircraft shortly entering full-scale production, HPC spoke with representatives from Boeing’s principal composite materials suppliers for the following update on the advanced composite materials, processes and machinery now in use.

Prepregs for primary structure

Without doubt, the largest supplier of 787 composite materials is Toray Industries (Tokyo, Japan). The company is providing its trademarked Torayca 3900-series highly toughened carbon fiber-reinforced epoxy prepreg for the 787’s primary structure in unidirectional tape (various widths), narrow slit tape (for fiber placement), and woven fabric forms. The majority of the 3900-series materials will be made with intermediate modulus T800S fiber.

According to Earl Benton, director of sales and marketing for Toray’s U.S. subsidiary Toray Composites (America) Inc. (TCA, Tacoma, Wash.), the T800S fiber, which replaced the T800H fiber used initially on the Boeing 777, is the result of improved carbon fiber manufacturing processes, which result in higher production rates, and better availability without sacrificing mechanical performance or the company’s ability to meet Boeing’s rigorous BMS8-276 specification for primary structure prepregs. Boeing qualified the prepreg’s basic unidirectional product form for the 777 prior to 2004, in advance of the 787 program.

Toray prepreg will be used to form principal structures on the empennage; Boeing Fabrication (Seattle) will make the vertical tail while Alenia Aeronautica (Rome, Italy) will use it to fashion the horizontal stabilizer. At Vought Aerospace (Dallas, Texas), the unpressurized aft fuselage skins and stringers will feature the prepreg, as will Alenia’s center fuselage, Kawasaki Heavy Industries’ (KHI, Gifu, Japan) mid-fuselage and aft wheel well bulkhead, and Spirit AeroSystems’ (Wichita, Kan.) forward fuselage section. The center wing box, constructed by Fuji Heavy Industries (FHI, Tokyo, Japan) is fabricated entirely from Torayca prepreg. Mitsubishi Heavy Industries (Nagoya, Japan) will form skins, stiffeners and spars for the main wings and wing boxes from the material while KHI is responsible for the fixed trailing edge. Korean Air Aerospace (Seoul, Korea) is producing the wing tips. Both Mitsubishi and FHI have installed LINEAR ATLAS dual-phase automated tape laying machines from Forest-Liné (Paris, France), featuring two heads, one of which uses spooled unidirectional tape and the second using precut materials, permitting rapid lay down in complex areas. The Mitsubishi machines are reportedly the largest composite machine tools ever produced. Meanwhile, Saab Aerostructures (Linköping, Sweden) will use Torayca prepreg to fabricate cargo and access doors,

Latecoere (Toulouse, France) will make passenger doors and several smaller suppliers will make components as subcontractors to Tier 1 Partners. All components produced from Torayca prepregs will be cured via autoclave.

According to Andrea Dorr, manager of aircraft sales and marketing for Toray Composites (America), automating prepreg layup was a manufacturing imperative to produce the 787. “Since qualifying for the Boeing 777 in 1994, TCA and Boeing have continually been working to optimize the material forms for automated processing and improved production efficiencies,” she notes. “The key to making the economics work on 787 is obtaining much higher material lay-down rates than classic hand layup or first-generation ATL machines. Boeing needed to reach certain productivity levels in order to be able to commit to building a plane with this level of composite content.”

The 787 Partners selected equipment from the various global suppliers of automatic tape layers, fiber placement machines, and automated stringer laminators. “Boeing and Toray invested significant resources to develop and qualify material forms that meet stringent mechanical and physical property requirements for 787 while accommodating a wide range of processing needs. The material forms were designed to meet the high lay-down rates required to support the 787 Program production rates.”

Fortunately, Toray did not have to develop new types of prepreg processing equipment, but simply had to scale existing machinery to meet volume demands. In addition to standard unidirectional tape, a number of other product widths and forms, including narrow slit tape and woven fabric styles were added and qualified. One fabric style includes an interwoven conductive wire, and is used as the outermost ply on the fuselage for lighting-strike protection.

Further, Toray has not had to spend much time working with its partners to optimize the specific component cure cycles, even though there are significant differences in shape, size and thickness among the solid laminates (wingskins and spars are much thicker than the fuselage skins, for example). “Boeing and the Partners establish the processing parameters based on the section and equipment through the qualification of the fabrication equipment at the Partners’ sites.” Dorr reports. Getting all the product forms qualified, however, was no easy task, Benton notes. Virtually the entire Toray Composites (America) engineering staff has been involved full time in this effort going back to 2003, he adds.

“Among the biggest challenges,” says Dorr, “is managing the material requirements and logistics supply chain for the geographically diverse group of Boeing Partners. The process of forecasting requirements and production needs for the expanded range of product forms is further complicated by the differences in Partner production flow times as well as logistical considerations.”

To meet the growing demand for carbon fiber, Toray has invested significantly in carbon fiber and prepreg manufacturing capacity (for facts and figures, see “Related Content,” at left). Benton says that while the prepreg expansion is almost entirely driven by the 787 program, the fiber expansion is geared to meet expected growth in aerospace and nonaerospace markets.

Toray’s Benton observes that, while the Tacoma prepreg facility was established in 1992 to supply material for Boeing’s 777 horizontal and vertical stabilizers and floor beams, the goal always was to set the bar much higher. “The 787 program, at least from Toray’s point of view, has been the objective all along: the dream of making a composite airplane,” he says. “We have transitioned from a local supplier to two Boeing facilities nearby in Fredrickson, where the empennage for the 777 is built, to a full up global prepreg supplier.”

Although all of the Toray prepreg for the 787 currently is produced in Tacoma and shipped to component manufacturers in Japan, Korea, Italy, France, Sweden and North America, the transition will include establishing local inventory sites for prepreg in Europe, Japan and North America. Within the next two years, prepreg manufacture will commence in Japan, in closer proximity to the Fuji, Mitsubishi and Kawasaki sites.

New materials, different processes

Challenges abound not only because of the increased use of composites and the global scope of the supplier base but because the 787 incorporates several new material forms and some key components made with out-of-autoclave molding processes. “The 787 program represents a huge step change for the composites industry. It is a wonderful and different approach to building an airplane, leading to a wealth of different products,” says David Barr, material supplier Hexcel’s (Dublin, Calif.) director of Americas development programs, but adds, “The scale and scope of this airplane brought on a whole lot of new challenges for material suppliers and part makers.”

Hexcel has several new materials on the 787. One, its trademarked HexMC, was selected for the 787’s larger window frames, which on the 787 are considered a primary structure. HexMC is a quasi-isotropic form of prepreg for compression molding, produced by precision cutting of prepreg unidirectional tapes, yielding considerably higher properties than traditional SMC or BMC. For the window frames, the company’s trademarked HexPly AS4 carbon fiber prepreg is based on Hexcel’s aerospace-qualified 350°F/177°C-cure 8552 epoxy prepreg resin. Barr says the advantages of HexMC include very good structural properties, net shape molding, better fatigue performance than most metals, with lower weight and no need for fiberglass galvanic corrosion barrier plies.

The NORDAM Group’s Interiors and Structures Div. (Tulsa, Okla.) got the production nod for the window frames in February after an 18-month development cycle. NORDAM and Boeing developed detailed specifications, created five design configurations and did qualification and certification testing for the first composite window frame for a commercial airliner.

Al Miller, Boeing’s director of advanced technology, reports, “NORDAM said they could meet our specifications and they did. The window frame is a truly innovative product and has helped Boeing achieve performance targets for the aircraft.”

The frame is expected to have significant impact on two key 787 characteristics: Its new, low-density composite saves nearly 50 percent in weight, and it offers superior damage tolerance compared to conventional aluminum frames. NORDAM has delivered initial shipsets to Boeing’s fuselage manufacturing partners Alenia Aeronautica, Kawasaki Heavy Industries, Spirit AeroSystems and Vought Aircraft Industries, where they are attached to the fuselage skins.

HexMC also is specified for a number of other parts including highly loaded gussets, pressure pans, clips, brackets and other small components typically produced in aluminum or titanium. Hexcel has assumed the tasks of designing, tooling, molding and certifying these components before delivery to Boeing’s system suppliers.

The engine nacelles for both the GE and Rolls Royce engines, fabricated by Goodrich Corp. (Charlotte, N.C.), use HexPly 8552/AS4 prepregs in the structures. The monolithic and sandwich structures are fabricated via advanced manufacturing techniques and incorporate a variety of Hexcel’s HexWeb honeycomb core products. For the GEnx engine option on the 787, GE has disclosed that the fan blades will use GE90 composite technology that has performed well, with no routine on-wing maintenance required and no in-service issues for more than a decade.

Engine noise reduction will be helped by use of Hexcel’s new trademarked Acousti-Cap inserted septum structural core. The patent pending Acousti-Cap technology, says Barr, is a one-piece inserted cap concept that provides optimized acoustic properties. The core can be heat-formed and machined to final part shape of the final part before the application of the skin plies and a single cure.

Out-of-autoclave trailing edges

Hexcel is supplying resins and structural carbon fabrics for out-of-autoclave manufacture of the 787’s movable trailing edge control surface components, a package that includes the aileron, flaperon and the inboard and outboard flaps, seven spoilers and all the fairings. A key product is HexFlow RTM6, which is widely used in the aerospace industry for the molding of composite structures. The components, produced by Hawker de Havilland (Melbourne, Australia), employ a specially developed HexForce fabric based on 12K spread tow fabric.

Although Hawker de Havilland has been a Boeing subsidiary since 2000, it must compete for Boeing contracts and was selected in November 2003 for the trailing edge package because of its economical vacuum-assisted resin-transfer molding (VARTM) process, which is based on technology developed for Boeing’s Sonic Cruiser. According to Steve Sloan, Hawker’s engineering manager, R&D on the process was supported by Australia’s public/private joint venture, the Cooperative Research Centre for Advanced Composite Structures, of which Hawker has been a member since the Center’s inception in 1991. The system, Sloan contends, will be more robust, more easily repairable and less prone to damage than previous trailing edge components made with conventional autoclaved prepreg sandwich structures. “What HdH and our team have done,” says business development general manager Tony Carolan, “is to develop innovative application techniques and predictive tools to allow liquid molding to be applied predictably and efficiently for a consistent, high-quality outcome.”

During the development phase, three large test “skins” more than 30 ft/9.1m long were fabricated using the process. The company is designing tools, running “producibility” trials, testing materials and hardware, implementing planning and production processes and finalizing its supply chain.

The wing leading edge structures are produced at Spirit AeroSystems Inc.’s Tulsa, Okla., facility. Hexcel provides large preformed, machined and splice-bonded HexWeb honeycomb subassemblies ready to be placed in the bonding tools for the movable leading edge structures. For these components, Boeing specified a carbon prepreg that combines Cytec Engineered Material’s (Tempe, Ariz.) high-temperature bis-maleimide (BMI) resin with Cytec carbon fiber reinforcement. This allows Boeing to remove some insulation that otherwise would be required with traditional epoxy systems, because the wing deicing system (the source of high heat) is integrated into these components. A combination of Hexcel-supplied Boeing BMS legacy glass and carbon fabric-reinforced epoxy prepregs, cured at 250°F/121°C is specified for the fixed leading edge structure.

For the interior, Barr notes that Hexcel is qualifying press-molded passenger and cargo compartment floor panels that are reportedly the lightest carbon-skinned sandwich panels available with a nonmetallic core. Additionally, Hexcel is supplying traditional 250°F/121°C- and 350°F/177°C-cure epoxy systems for various fairings and closure panels.

On the tooling side, Barr reveals that Hexcel’s trademarked HexTool, a heavy aerial weight prepreg of carbon fibers and high-temperature BMI resin, is being used for the construction of lightweight tools for fabrication of smaller and midsized components. Fuselage production

Elsewhere, Vought Aircraft Industries Inc. (Dallas, Texas) reports that its North Charleston, S.C.-based 787 production facility delivered the first shipset of rear fuselage sections in April. These comprise 23 percent of the 787’s fuselage structure: section 47 measures 19 ft in diameter and 23 ft long (5.8m by 7m), while section 48 measures 14 ft in diameter and 15 ft long (4.3m by 4.6m). Automated tape laying equipment from Cincinnati Machine (Hebron, Ky.) applies Toray 3900-series unidirectional carbon/epoxy tape onto a large barrel-shaped rotatable mold made from interlocking mandrels. Barrel sections are cured in Vought’s 76-ft long by 30-ft diameter (23.2m by 9.1m) autoclave — the world’s largest by volume, built by ASC Process Systems (Sylmar, Calif.)

In March, Alenia Aeronautica (Rome, Italy) shipped the first 787 composite fuselage center sections 44 and 46 from its new composite fabrication facility in Grottagie, Italy to Global Aeronautica, a joint venture between Alenia and Vought in Charleston, S.C., which will assemble several fuselage sections. Section 44 is about 28 ft/8.5m long and section 46 is about 33 ft/10m. Alenia is using the latest generation of fiber-placement equipment from Ingersoll Machine Tools Inc. (Rockford, Ill.). Alenia also supplies the horizontal stabilizer from its facility in Foggia, Italy.

On Feb. 15, Spirit AeroSystems began production on the first all-composite forward nose (section 41). Fiber place-ment equipment from Ingersoll applies composite plies over the barrel’s compound contours, Spirit wrapped the forward section and then prepared it for cure in a 70-ft long by 30-ft diameter (21.3m by 9.1m) autoclave designed, built and recently installed by Thermal Equipment Corp. (Torrance, Calif.)

The nose section measures 21 ft in diameter and 42 ft long (6.2m by 12.8m). Nondestructive inspection (NDI) was successfully completed on the first production article using AUSS XVII (Automated Ultrasonic Scanning System, Generation 17), a product of the Boeing Automated Systems Group (BASG, St. Louis, Mo.). Subsequent tests confirmed the structural integrity of the unit based on lessons learned on three developmental articles. “The proof of concept on our developmental sections went very well, and set the stage for production of the first 787 forward section,” says John Pilla, Spirit’s 787 VP/general manager.

Cytec’s SurfaceMaster 905 surfacing film is used on all fuselage sections to reduce post-molding finishing (pit filling and sanding) prior to painting. A high-temperature bismaleimide (BMI) composite material from Cytec has been selected as an enabler for section 41’s fuselage barrel tooling. BMI tooling is much lighter than traditional Invar, potentially less expensive, and offers faster heating and cooling rates compared to metals.

VARTM’d rear pressure bulkhead

Vought’s aft fuselage unit includes the rear pressure bulkhead received in late March from the European Aeronautic Defence & Space (EADS) Military Aircraft business unit (Augsburg, Germany). The one-piece dome, which is inserted between section 47, the end-most pressurized section, and the unpressurized section 48 and tail section, is made using a vacuum-assisted resin transfer mold (VARTM) process and is approximately 14 ft by 15 ft (4.3m by 4.6m) in size. The 787 will be the first Boeing aircraft ever equipped with a composite aft pressure bulkhead.

The bulkhead benefits from a proprietary Cytec resin-infusion system. The process reduces capital expense on tooling and recurring materials costs, compared with traditional prepreg. The toughened composite reportedly has top flame/smoke/toxicity performance, allowing the elimination of fire barriers while reducing weight when compared with conventional resin infusion.

Landing gear braces

Albany Engineered Composites (AEC, Rochester, N.H.) is preforming the carbon fiber braces for the 787 landing gear structure supplied by Messier-Dowty (Vélizy, France). The preforms are being supplied to Messier-Dowty affiliate Aircelle (Le Havre, France), where they are infused with epoxy resin via resin transfer molding (RTM).

According to John Tauriello, Albany’s director of sales, business development and programs, the fiber is Hexcel’s IM-7, and AEC uses a Jacquard 3-D process to weave net-shape preforms with 55 to 60 percent fiber volume, with a portion of the fibers oriented in the z-direction to provide ply-to-ply interlock functionality and improve damage tolerance.

Ripple effects and turning points

The Boeing 787 suppliers are not the only industry players to benefit from the effort behind the plane. “Having a commercial airplane with this level of carbon fiber content offers the opportunity to overcome fluctuations in capacity that have been an issue in the carbon fiber industry for years,” says Toray’s Dorr. “With all the increased capacity, smaller fluctuations will not have as big an effect.”

More importantly, with Airbus Industrie poised to put its A380 into full production, a long-awaited volume market for aerospace-grade carbon is now firmly in place. And industry suppliers privately posit that we are witnessing a transformative event long awaited in the composites industry.

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