Engine OEM mulls composite fan blades

 - September 23, 2008, 6:51 AM

UK-based Rolls-Royce and GKN Aerospace have established a joint venture to study the use of composite materials in fan blades. The engine manufacturer and the aerostructure specialist are investing, on a 51-49 basis, £11 million ($22 million) in
a research and development program. For Rolls-Royce, this could signal a major shift from a well established design choice.

The joint venture stems from an ongoing research program called Vital and partly funded by the European Union. The goal of the program was to produce high-bypass-ratio engines “that could deliver a significant reduction in both noise and fuel burn.” Therefore, new technologies that will eliminate weight penalties incurred by the increase in bypass ratio are needed, a Rolls-Royce spokesman told AIN. Research on composite fan blades began under Vital.

Ric Parker, Rolls-Royce director for research and technology, said that the goal is “delivering light and low-cost fan blades for next-generation engines.” Vital’s objectives include a 2-percent improvement in fan system efficiency. GKN will bring automated manufacturing technologies, among other things, to the table. The joint venture is supported at a national level, too, with the UK government co-funding a technology program called “the environmental lightweight fan.”

In recent years, Rolls-Royce officials have consistently asserted that titanium fan blades offer better overall performance, notably in weight, than their composite equivalent. For example, the BR725, destined to power the Gulfstream G650, has 24 titanium blades. However, the company spokesman pointed out Rolls-Royce flew composite fan blades on the Conway engine in 1968. “But, as materials and manufacturing techniques have improved, we have continued to re-evaluate the benefits of competing technologies,” he added. [Ironically, it was failure of the carbon-fiber fan first intended for the RB211 widebody turbofan that plunged Rolls-Royce into bankruptcy nearly four decades ago.–Ed.]

General Electric, Rolls-Royce’s main competitor in air transport engines, has its GE90 in service with carbon-fiber fan blades. The U.S.-based manufacturer claims it has created “a uniquely curved blade design that is lighter, more aerodynamic and larger than traditional titanium blades.” The leading edge of GE90 fan blades, however, is made of titanium.