1. Multi-objective, multi-point aerodynamic optimization at a high-lift condition and at a cruise condition. The maximisation of the maximum lift coefficient and the simultaneous maximisation of aerodynamic efficiency L/D at 70% of maximum Cl were selected as objectives for the high-lift condition. The maximisation of L/D ratio at fixed angle of attack was selected as objective for the cruise condition. A baseline shape was selected featuring a droop nose, in order to facilitate the achievement of shapes optimized for different flight conditions from a single starting shape. The optimization at high lift conditions provided a 1.8% increase in CL,max and simultaneous 0.3% increase in L/D at 0.7*CL,max with respect to the new baseline. At cruise conditions, a 2.8% increase of L/D and simultaneous 2.7% increase in CL was achieved.
2. Extension of the aerodynamic optimization to an airfoil with a trailing edge flap; 3% increase in CL,max and simultaneous 0.5% increase in L/D at 0.7*CL,max wrt the baseline with flap was achieved in high-lift conditions, while a 2.7% increase of L/D and simultaneous 2.4% increase in CL was achieved in cruise conditions.
3. Structural optimisation to reach target shapes from the aerodynamic analysis, using both 2D and 3D structural models of the airfoil. The structural properties of the 2D model were determined by the extension stiffness (EA) and the bending stiffness (EI). The influence of the stringers was also considered by increasing the EI value for the corresponding beam elements. The structural optimization was a two level optimisation, in which the first level was employed to find the optimal stiffness distribution matching the aerodynamic target shapes, while in the second level the optimal stiffness was achieved using practical structural components. The results from optimization proved that a single target shape can be achieved with good accuracy from its baseline shape and also an approach to reach two different target shapes was demonstrated on a number of test points.
4. Sizing of the Leading Edge Composite; the achieved stiffness distribution from the first level structural optimization was sized, with the aim of finding the optimal stack sequence in each element.
5. Enhancement of airfoil composite skin design; the skin was tailored based on a variable stiffness composite. The potential of reducing the actuation forces was investigated and Puck’s failure model was included in the model. Required actuation forces can be reduced if the stiffness of the leading edge skin is varied.
6. Quantification of aeroelastic effects on the optimised shapes: the developed strategy is effective in ensuring that the structural shapes match the targets and that aero/structural effects are low and do not degrade aerodynamic performance. It was found that it is possible to keep the EI range low by placing actuation locations in the region on the suction side where pressure loads are higher. Also, adding more actuation points seemed beneficial for the shape error.The influence on aerodynamic performance of limit on maximum curvature variation was also studied, highlighting a low sensitivity when it is chosen among standard values for typical composite materials used for morphing applications.
7. Analysis and optimization of an unconventional morphing concept proposed by the TL, where the lower edge of flexible skin is connected to the front spar by a deployable hatch, in order to provide additional deformability, showed that higher stall Cl can be obtained.
As part of dissemination/communication/exploitation activities, two peer-reviewed papers were published in specialised journals and a conference paper was presented. Also, the developed routines both for aerodynamic and structural optimization were delivered to the TL for further exploitation.
