GE Aviation has been developing CMCs for decades. Manufactured from silicon carbide ceramic fibres and ceramic resin, CMCs are lightweight, just one-third the density of metal, and are more heat resistant than metals, helping to improve fuel-efficiency.
The doomed F136 – a joint project with Rolls-Royce that wasn’t completed due to US defence cuts – developed in the 2000s was the first to incorporate CMC components in the hot section of the engine (low-pressure turbine vanes).
And now, the GEnx includes CMC parts in the turbine and the combustor, meanwhile the LEAP – created with its CFM partner Snecma – has a CMC turbine shroud.
Of course, CMCs are not the only composites in these engines. Both have woven carbon fibre blades, for example. Safran, which is working with GE Aviation on the LEAP blades, has confirmed that it expects its composite manufacturing operations to account for eight per cent of annual revenues by 2020.
That’s a staggering four times more than the materials do now, but with a backlog of 7,500 LEAP engines and counting, Safran can afford to be confident. It is no wonder then, that it opened a €50m ($64m) research plant earlier this year.
Not to be outdone, Rolls-Royce has developed its own carbon-titanium composite blade for the next generation of Trent engines. The new blade, which is set to move into flight testing, will offer a 1,500lb weight saving per aircraft, the OEM claims, significantly contributing to the Ultrafan’s predicted 25% improvement in fuel efficiency over the first generation Trent.
With the global market in aerospace composites already worth billions of dollars, it is set to become even more lucrative as the next generation of engines take to the skies. For MROs then, it is important to get to grips with these materials and how to repair them.
Read Bernard Fitzsimons’ article on advances in composite materials in the current issue of Aircraft Technology Engineering & Maintenance.