Increased automation of the production process is the key to boosting the scope for using composite materials in new airframes. As such, it is the main driver of development work at GKN’s new composite research center. And, according to John Cornforth, the UK group’s head of technology, aero engines are the most promising future application for modern composites.
The research center is part of GKN’s advanced composites facility which opened a year ago at Cowes on the Isle of Wight in southern England. The production center is pioneering resin film infusing techniques and has a new $2.5 million automated tape layer (ATL) that puts down composite materials up to 50 times faster than if the task were done manually.
GKN’s contract to provide 20-meter (65.6-feet) wing spars for the Airbus A400M military transport aircraft is extending ts capabilities in automated composites manufacturing. These are the first all-composite primary structures on a large transport aircraft wing.
Much of the work on the first ship set–delivered in late May–was still done manually but the company expects to have automated most of the process by the time the sixth ship set is completed around the end of this year. Overall, the largest wing sections can be completed in just 24 hours, compared with a typical manual process spanning six to eight days.
The 11-axes ATL machine has taken just 12 hours to lay materials for the longest 14-meter section of the A400M spars and the company expects this time to be reduced further as the GKN team fully integrates it into the production process. One issue it has confronted is elimination of wrinkling in the composite layers.
Cost Is Key
According to Cornforth, composite solutions are increasingly suitable in technical terms for aircraft primary structures but the key is to ensure that the cost of these makes sense when compared to equivalent metals. “We have to get the cost of making these structures down to today’s market price,” he told a pre-Farnborough show press briefing.
In fact, much of this cost is driven by insufficient supply of carbon fiber to meet strong worldwide demand from aerospace and other industries. Raw material costs for composites are still higher than for steel and aluminum, but they can be less than for titanium. Nonetheless, GKN believes that by extending automation it can achieve a 30-percent reduction in the cost of composite structures.
The Cowes facility has a 16-meter autoclave that allows for two spar sections to be formed at the same time. The A400M contract calls for up to four ship sets to be produced each month–requiring the completion of 32 spar sections in this time frame.
GKN is also developing techniques to allow composite curing to be done outside autoclaves, using self-heated tooling. This approach will allow the company to work on odd-sized structures that wouldn’t fit in an autoclave, as well as easing production bottlenecks over autoclave capacity. It also promises to improve quality and reduce the amount of nondestructive testing and reworking that needs to be done. The company also employs an innovative “double-diaphragm” forming process.
The GKN process includes an advanced Henri Liner milling machine which ensures accuracy in making the composite shapes (to a tolerance of just 0.25 mm) without the need to refine them by hand. Specially developed software compensates for deficiencies of the machine on all its five axes, taking into account factors such as seasonal temperature changes.
The quality of the composite structures is meticulously reviewed in just the same way as if they were metal. According to Cornforth, only about 2 percent of the composites production has to be reworked and the scrap rate is less than 1 percent.
Cornforth explained that increased automation in the composites manufacturing process will ensure an exact fiber content throughout the structures. This degree of certainty will reduce the design weights of the structures, as will the growing ability to bond composite parts together.
For GKN, automating production processes at its facilities in the West has proved to be more attractive than outsourcing work to lower-cost economies in eastern Europe and Asia. “This hasn’t proved easy because the countries concerned aren’t generally ready to take the technological leap that is required for this sort of production,” explained Cornforth.
Working Toward a Complete Wing
With anticipated programs such as next-generation narrowbodied airliners in mind (that is, A320 and Boeing 737 replacements), GKN’s composites research center has been focusing on challenges such as the best production process for close-boxed structures such as tailplanes and ailerons that would form part of an integrated wing. In the long term, the company would ike to achieve the manufacturing capability for a complete small wing, including its control surfaces.
The center is also charged with advancing GKN’s claim to be the UK center of excellence for composite structures in aero engines. For instance, the group is now working on a prospective new composite fan blade for engine maker Snecma and will complete the preliminary design review in September before discussing the production phase.
Increased automation also promises to make it more feasible to create cylindrical or conical nacelle components from composites, including fan cowl doors, inlets and nozzles. The company already makes the fan cowl for the Rolls-Royce Trent 700 engine that powers the A330 twinjet. Much of GKN’s research has enjoyed the backing of European Union funding for programs aimed at reducing the environmental impact of air transport by improving engine efficiency and reducing airframe weights.
Projects such as the A400M wing spars and large composite assemblies on the Airbus A380 illustrate the degree of program responsibility and investment that have made GKN Aerospace (Chalet G1-3) a leading tier-one supplier. The group, which last year generated revenues of more than $1 billion and now employs 6,300 people, also makes metallic structures (for example, ribs for the fuselage of the C-17 military transport), nacelles, engine components, transparencies, electrical de-icing systems, fuel tanks and flotation systems. Recent contract wins included preferred vendor status for A330/340 cabin windows and development of a new ice protection system for the Pratt & Whitney F135 engine for the Lockheed Martin F-35 Joint Strike Fighter.
