Technology Update

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March 2002
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French R&D on new materials and surface treatments

Research and development into new materials technology—including surface treatment—is a central issue in the aerospace industry. In France, specialists across a broad spectrum of R&D centers are concentrating on applications that will help the aerospace industry meet not only its historical needs of saving weight and gaining performance, but also of wider issues.

"In the future, we will concentrate less on the material itself than on its relationship with its environment, as shown by the interest recently expressed in surface treatment," said Armand Coujou, a research engineer with the French CNRS (Centre National de la Recherche Scientifique) at the Materials Development Center in Toulouse, which is focusing on alloys and superalloys, composites, ceramics, and polymers. "Currently, aeronautical research is centered on improvements to (aluminum) alloys by optimizing their mechanical properties and corrosion resistance. In the past, researchers were primarily concerned with mechanical structure. Now, a part can no longer be understood without considering its treatment. As constraints apply to parts that are becoming smaller and smaller, lightweight, and subjected to harsh environments (friction, movement, elevated temperatures), their surfaces are becoming much more stressed."

CNRS is also looking at possible future applications of polymers in aircraft. "In aeronautics one tries to simplify the system by having materials that perform several functions," said researcher Colette Lacabanne. "We have carried out research with partners Hexcel Composites and Métallisation Tarbaise to replace the composites currently used in the composition of aircraft wings, with a structure made entirely of polymer." Although very light in weight, polymers are not conductors of electricity, and can be damaged by lightning. Métallisation Tarbaise is developing a thermal sprayer that would facilitate metallization of the material.

French research into metals technology includes rhenium and powder metallurgy. Airbus, Snecma, and Turbomeca want to know more about them and possible applications. As a result, French research centers are working on both. Rhenium, with a melting point of 3180°C, has applications for highly hostile environments inside aircraft engines, such as for turbine blades and internal coating of combustion chambers. Powder metallurgy could improve turbine disc life. Fortech, a subsidiary of Eramet Alloys, is among companies carrying out research.

Pechiney Aerospace, a specialist in profiled and thick laminates for wing stiffeners, has developed an alloy that is described as being more corrosion-resistant than 2024 aluminum, which has traditionally been used in structures and fuselage skin for civil aircraft. "We have developed a weldable material, called 6056, with a metallic state that 'desensitizes' the metal to corrosion. It was qualified for a little over a year on the Airbus A318," said Technical Development Engineer Philippe Lequeu. About 50% of the company's annual aerospace R&D budget is dedicated to the development of new alloys for wide-bodied aircraft, including the forthcoming A380. The company says that an alloy (7449), which has applications specifically to wings and is said to improve corrosion resistance by 10%, "had its first flight last April on the A340-500/600 and will almost certainly be adopted for the A380." Two alloys for skins and lower wing stiffeners, designed to offer a 10-20% gain in damage resistance, are currently undergoing qualification.

Very small parts are also subject to improvement programs. Atelier de la Haute-Garonne is a major supplier of rivets to the aerospace industry. The company has developed a new rivet from "improved alloys." It has recently been qualified on all Airbus assembly lines. According to the company, traditional rivets require treatment time. The technique it has developed is simplified. No tempering or surface treatment is required before use and there is unlimited storage time and no difficulties in placement.

Mapaero, a specialist aircraft paint subsidiary of Peintures Maestria, has developed and qualified a new generation of water-based paints. The program took seven years, with qualification by Airbus in 2000 and initial production application last year. It will be used across Airbus assembly sites. Mapaero Managing Director Jean-Francois Brachotte, said, "This paint, intended for aircraft structures (wings, fuselage), contains 15% solvents compared with 70% in currently used products, while guaranteeing equivalent performance. While reducing emissions of volatile organic compounds, it enables a reduction in costs and higher production rates because it is slightly cheaper, requires smaller quantities, and dries more quickly."

- Stuart Birch

A400M moves ahead

The A400M will have a 780 km/h cruise speed.

The Airbus Military A400M transport aircraft has moved significantly closer to manufacture with the agreement of eight European nations to purchase a total of 196 aircraft for their respective air forces. In keeping with the company's philosophy, the aircraft's design, engineering, and manufacture will be the responsibility of Airbus units across Europe.

Airbus UK will look after the overall management and design of the A400M wing and fuel system, plus assembly and full equipping of wings, including all systems and flying control surfaces. Much of the A400M's wing will use composite materials. Airbus UK's engineering and manufacturing teams have been working closely for some time on new specialized techniques and processes in the assembly of large composite aircraft structures.

The final assembly line for the A400M will be in Spain. The aircraft has been designed to offer an alternative to ageing fleets of C-130 and C-160 Transall aircraft and will have four high-speed turboprop engines to provide a cruise speed of Mach 0.72 at up to 40,000 ft. Designated TP400, these new powerplants will be jointly developed by a European consortium comprising Rolls-Royce, Snecma, MTU, FiatAvio, Industria de Turbopropulsores, and Techspace Aero. The Turkish aero industry has also been invited to take part in the program.

The A400M will be capable of operating from unprepared landing strips under adverse meteorological conditions, totally independent of ground support. It will have an in-flight refueling capability and could be rapidly converted to flying tanker role with hose and drogue refueling pods. The aircraft will feature a high wing configuration, rear loading ramp, large rear door, and tandem high-flotation retractable landing gear for soft-field conditions. The gear will include a "kneeling" facility. The aircraft has a "T-tail." The cargo hold will measure 22.9 m long including the ramp, 4 m wide at floor level and 3.85 m high. The load-carrying ramp will have a capacity up to 6000 kg. A powered crane with 5-t capacity will be fitted to facilitate loading from the ground and cross-loading capability.

Airbus has issued a list of some of the main areas of technology that the aircraft will embrace, including: composite propellers; turboprop engines; wing section; double-slotted flaps; carbon-fiber primary structure; proven fly-by-wire controls; flight envelope protection; and proven built-in test equipment (BITE).

The aircraft is due to fly in 2006, with initial customer deliveries scheduled for 2008.

- Stuart Birch

March 2002
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