This dissertation explores the development of a framework for wing aeroelastic tailoring in the preliminary design phase of aircraft, focusing on weight reduction and aerodynamic efficiency through the use of composite materials. The framework utilizes low-fidelity, fast computational tools to handle numerous load cases, modeling the wing structure with FEM shell elements and aerodynamics with the doublet lattice method (DLM). Composite material properties are optimized using lamination parameters, with structural continuity enforced through blending constraints.

To address the limitations of low-fidelity methods, CFD-based corrections are applied to the DLM for accurate aerodynamic load representation, and a surrogate model is introduced for aerodynamic drag estimation. This model approximates wing deflection efficiently, reducing the need for costly high-fidelity simulations.

The framework, implemented in Nastran, is applied to industrial cases focusing on the impact of blending constraints, dynamic load cases, and multi-objective optimizations balancing weight and drag. Blending constraints result in smoother transitions between wing sections, ultimately producing a light final design, even though there is an initial 5% increase in structural weight due to a reduced design space. Dynamic loads, incorporated through the Equivalent Static Load (ESL) method, have minimal impact on the overall design.

Multi-objective optimization reveals trade-offs between structural weight and aerodynamic drag. Weight minimization favors structures with wash-out behavior, leading to higher drag due to increased angle of attack. Conversely, drag minimization results in stiffer wings with less wash-out. The framework's results align closely with full-order CFD models, validating its effectiveness.@en

In aircraft design, proper tailoring of composite anisotropic characteristics allows to achieve weight saving while maintaining good aeroelastic performance. To further improve the design, dynamic loads and manufacturing constraints should be integrated in the design process. The objective of this paper is to evaluate how the introduction of continuous blending constraints affects the optimum design and the retrieval of the final stacking sequence for a regional aircraft wing. The effect of the blending constraints on the optimum design (1) focuses on static and dynamic loading conditions and identifies the ones driving the optimization and (2) explores the potential weight saving due to the implementation of a manoeuvre load alleviation (MLA) strategy. Results show that while dynamic gust loads can be critical for wing design, in the case of a regional aircraft, their influence is minimal. Nevertheless, MLA strategies can reduce the impact of static loads on the final design in favour of gust loads, underlining the importance of considering such load-cases in the optimisation. In both cases, blending does not strongly affect the load criticality and retrieve a slightly heavier design. Finally, blending constraints confirmed their significant influence on the final discrete design and their capability to produce more manufacturable structures.

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In the present paper the authors want to investigate the effect of different load configuration in order to identify the ones driving the optimization. A set of static loads, gust loads and static loads with maneuver load alleviation (MLA) are tested. Gust loads have been included in the optimization via an equivalent static load (ESL). Composite blending is tackled by means of continuous constraints and a two phases approach is proposed to find a blended stacking sequence table. Results show that region of influence can be identified for specific loads and that MLA can be beneficial for structural weight reduction. Finally, the blending constraints prove their effectiveness by significantly reducing the error in retrieving a blended stacking sequence.

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The main objective of this paper is to propose an aeroelastic optimization approach capable of performing structural sizing optimization considering structural and aerodynamic constraints. The proposed approach uses a detailed FE model of a composite wing with shell elements in order to obtain realistic weight estimation and structural responses. Moreover, a surrogate model based on rigid RANS computations provides a high-fidelity lift and drag coefficient estimation during the optimization as constraints. The use of RANS computations allows the surrogate model to consider all drag components and not the induced drag only. An approximation of the structural displacement is proposed based on modal projection and principle component analysis. Results shows that a polynomial regression of order four is accurate enough to be used as surrogate model of the drag coefficient and of the lift-to-drag ratio. Moreover, it is possible to conclude that improvements in aerodynamic performance comes at the price of a heavier and stiffer structure.

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Optimizing the laminates of large composite structures is nowadays well-recognized as having significant benefits in the design of lightweight structural solutions. However, designs based on locally optimized laminates are prone to structural discontinuities and enforcing blending during the optimization is therefore crucial in order to achieve structurally continuous and ready-tomanufacture designs. Bi-step strategies, relying on a continuous gradient-based optimization of lamination parameters followed by a discrete stacking sequence optimization step during which blending is enforced, have been proposed in the literature. However, significant mismatch between continuous and discrete solutions were observed due to the discrepancies between both design spaces. The present paper highlights the capability of the continuous blending constraints, recently proposed by the authors, in reducing the discrepancies between discrete and continuous solutions. The paper also demonstrates that more realistic optimal continuous designs are achieved thanks to the application of the blending constraints during the aeroelastic optimization of a variable stiffness wing. Additionally, the proposed blending constraints have been applied to NASTRAN SOL 200 showing their ease of implementation in commercial software. @en