PARIS -- As visitors to the ongoing Paris Air Show crane their necks to see the mechanical marvels soaring overhead, new fuselage and engine materials are also getting plenty of attention. This segment of the aviation business is where Japanese companies shine.
Among the innovations highlighted at the event -- one of the world's largest aviation shows -- is a "supermaterial" called ceramic matrix composite, or CMC. General Electric of the U.S. has adopted CMC components for the high-pressure turbines in its next-generation Leap and GE9X jet engines.
CMC is made of silicon carbide ceramic fiber and ceramic resin. It goes through a highly sophisticated manufacturing process and is further enhanced with proprietary coatings. Silicon carbide ceramic fibers are two-thirds lighter, 20% more heat-resistant and twice as strong as nickel alloys -- the conventional materials for aircraft engines.
Bill Millhaem, general manager of the GE90/GE9X engine programs at GE Aviation, spoke at the show and stressed the revolutionary heat-resistance capabilities of CMC. The material's strengths are best demonstrated in high-pressure turbines, Millhaem said.
Combustion gas with a temperature of over 1,000 C is injected into these turbines. Nickel alloys must be cooled with air brought in from outside. But CMC can withstand temperatures up to 2,000 C without cooling.
Since surplus air can be used as thrust, using CMC in turbines leads to more efficient combustion, according to Millhaem. The new Leap engine is estimated to be over 15% more fuel efficient than current engines, though CMC is not the only reason for this.
GE selected Nippon Carbon as a partner for setting up a CMC venture, along with French engine manufacturer Safran. NGS Advanced Fibers, the new company based in the city of Toyama in central Japan, is to spend some 6 billion yen ($48 million) on a plant for mass production.
CMC in action
The Leap engine will be supplied to Boeing for its new 737 Max and Airbus for its A320neo.
The A320neo, which is 15-20% more fuel efficient than the existing A320, is due to make its first commercial flight sometime between October and December. The 737 Max, which is 14% more efficient than today's 737, is scheduled to make its maiden flight in 2017.
At this point, CMC is used only in turbines, but Millhaem suggested it will end up in other components, such as combustion liners and cylindrical parts.
GE intends to make such CMC components with its 3-D printing technology, which uses lasers to create complex jet engine parts from material dust. The company has already started making CMC components for 70 engines.
Capable of taking the heat
The underlying technology for all this -- silicon carbide fiber -- has improved dramatically in recent years. The upper temperature limit has been increased from 1,300 C to 2,000 C. The elastic modulus, which measures a material's resistance to deformation, has almost doubled to 380 gigapascals.
Electron beam irradiation technology is used to keep oxygen from infiltrating the material, which prevents deterioration at temperatures above 1,300 C. Nippon Carbon borrowed the technology from government-sponsored nuclear power research.
Ube Industries, meanwhile, has developed a continuous ceramic fiber it calls Tyranno Fiber. In partnership with Japanese machinery and component maker IHI, Ube is promoting its material for use in aircraft engines, too.
Ceramics and fibers tend to break up if they are combined too tightly. Ube solved this by coating the material with boron nitride. The company is now ramping up investment in the ceramic fiber project.
IHI, which has been doing its own special alloy processing to make such engine components as turbine discs and fans, is tapping chemical engineers to help expand production of CMC-based parts. Dealing with such new materials requires extensive knowledge of chemistry, particularly when it comes to temperature changes, according to Tsugio Mitsuoka, a senior IHI executive.
A GE Aviation executive sees possibilities for using CMC components in not only planes but also gas turbines for power plants.
Well-aware of the material's potential, U.K.-based Rolls-Royce, another aircraft engine manufacturer, has approached Nippon Carbon and Ube.