Although they were originally developed to improve the performance and reliability of solid rocket motors, thermostructural composite materials are being used increasingly in aeronautical propulsion applications wherever technical performance is a critical factor, and also when the intrinsic properties of these materials produce a more effective and efficient component.
Nozzle flaps for military aircraft engines
The intrinsic properties of thermostructural composites with a self-healing matrix, particularly their strength at high temperatures combined with low sensitivity to thermal gradients and their light weight, offers benefits in terms of mass, performance, and service life for afterbody components for military engines.Afterburner systems (flame holders) are an application for which CMC materials would offer weight gains and enhanced performance and durability.
Turbine shroud
Uncooled HP turbine sealing shrouds made from ceramic matrix composites (CMC) offer the potential of better performance (specific consumption) and reduced weight. A gain in possession cost is also possible as a result of the simplification of the complex architecture of the shroud (made possible by the low coefficient of expansion of the CMC material) and an increase in service life.
Afterbody of civil aircraft engines
The use of CMC thermostructural composite materials on the hot components of the engine and nacelle would offer a significant reduction in mass compared to the traditional metal versions (a gain of 30 to 50%). Its use on the nozzles and exhaust cones of civil engines is a promising application for engines of the future. The validity of this technological breakthrough has been proven by the design and production of a “mixer” type nozzle for the CFM56-5C made from CMC, which recently completed a successful series of tests. Not only is the shape of the CFM56-5C mixer extremely complex (with lobes to mix the streams of hot and cold gases) but it must also interface with both the nacelle and the aft structure of the engine’s exhaust casing.
Combustion chamber
Using Cerasep® thermostructural composite materials to make the walls of combustion chambers offers the advantage of enabling a reduction in the flow of cooling air over the walls, which makes the air-fuel ratio in the chamber leaner and consequently reduces the harmful emissions from the turbojet (particularly NOx). A full-scale prototype of the combustion chamber has undergone evaluation on a test bench.
