Over the last 10 years there has been an increase in passenger air travel of more than 50%. Thanks to highly efficient engines, however, fuel consumption has risen by just three per cent during the same period.
While there were some 84,000 flights per day in 2011, this figure is expected to increase to approximately 170,000 by 2030. Clearly, the efficiency of aircraft engines has to be enhanced even further to meet growing fuel requirements.
More efficient engines means bigger engines - but bigger engines are also heavier, which is why the use of light weight materials as composite components or aluminium can proof beneficial.
Annulus fillers made of composite
Modern engines generate 80 % of their thrust from the so-called bypass flow produced by the large blades at the engine intake. Between these blades there are aerodynamic fillers, and these have a crucial role to play: they ensure optimum airflow and sealing, as well as having to resist impact from foreign bodies such as hail and birds. During operation they are exposed to powerful centrifugal forces. Annulus fillers are currently made of aluminium. For quality reasons, the filigree components are milled from a single aluminium block, so unit costs are very high.
In a project lasting three years, the IWK (Institute of Materials Engineering and Plastics Processing at HSR University of Applied Sciences Rapperswil) joined forces with Rolls-Royce and the Austrian company FACC to develop such a component made of composite fibre. The prize-winning and partially patented design saves weight and can be cost-efficiently produced in larger quantities.
As the client, Rolls-Royce defined the requirements and technological framework conditions; the IWK developed the concept and designed all components and processes, and FACC produced a pilot series of fillers towards the end of the project.
During the development of the filler, the IWK made use of digital simulations and optimizations. This included structural simulations using finite element methods so as to ensure the component functioned reliably. Meanwhile the production process was designed and optimized using software developed by the IWK itself. The filler is produced using the Resin Transfer Moulding (RTM) method: this involves dry carbon fibres being inserted in a cavity between the upper and lower tool and then impregnated by the liquid resin system.
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