But one of the most interesting details to emerge from the session was the use of ceramic matrix composites (CMC) in the programme – marking the first time the material has ever been used in commercial aviation. Gareth Richards, LEAP program manager for CFM parent company GE Aviation, noted that if the “history of aviation is a history of materials”, then the development of ceramic matrix composites for aviation could mark the “beginning of a new material revolution”.
Ceramic matrix composites, a fully matured material system according to CFM, are being used in the high pressure turbine Stage 1 shrouds of the LEAP engine. Jumping from nickel alloys to CMCs marks a “huge step up in capability”, according to Richards, being a third of the weight and providing 20 per cent greater thermal capacity. Francois Bastin, LEAP program manager for Snecma, noted that the most remarkable characteristic of CMC is its “amazing strength” – twice the material strength of nickel alloys. In the Stage 1 shrouds, cooling air is eliminated as the part does not require cooling; this allows the engine to be much more efficient and durable.
The real revolution, though, will take place in programmes even beyond LEAP, according to Richards. He says the industry is going to see the “use of CMC grow dramatically in the years to come”, just as carbon fibre composite use has grown significantly in the past decades.
We are likely to see CMC used in fan blades and nozzles in the future, and while CFM has run tests already, achieving full maturity in these areas will still require more years of testing.
And in what could be a stark warning to CFM’s competitors (many of whom have played down the importance of CMC), Jamie Jewell, director, strategic communications at CFM International, claimed that the company was up to “30 years ahead of its competitors” in the development of ceramic matrix composites – an extraordinary head start if CMC delivers on the promise demonstrated in the LEAP programme.
Jason Holland, Editor, Aircraft Technology Engineering & Maintenance