Aero-elastic Tailoring of Composite Turbomachinery Blades through Gradient-based Optimisation

In recent years, advances in aircraft engine fuel efficiency have been largely the result of increased propulsion efficiency. The latter is obtained by increasing the diameter of the fan at the front of the engine, in contemporary designs responsible for most of the thrust. Further improvement is possible, but hindered by mechanical limitations of the fan blades, which are susceptible to aero-elastic flutter: severe vibrations created by a positive feedback between the blade’s motion and the force exerted on it by the air. Composite materials show great promise in this regard, as the strength and stiffness in various directions can be tailored to act on this feedback mechanism. Advances in additive manufacturing techniques now offer an unprecedented freedom in both the external shapes and internal structure (determining the strength and stiffness properties). Exploiting this potential requires advanced optimisation tools, capable of considering the internal structure as well as the external shape and taken aero-elatic behaviour like flutter into account. Their development has however been lagging behind. The goal of this research project is therefore to extend an existing optimisation framework to include the tailoring of composite materials considering aero-elastic effects. Applicable in various fields, the present project is centered on aircraft engine fan blades, as they are prone to experience flutter but offer an important outlook on improved fuel efficiency.