16:00
Nonlinear optimisation
Chair: Jonathan Cooper
16:00
30 mins
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Optimizing high aspect ratio composite wings through geometrically nonlinear aeroelastic tailoring
Touraj Farsadi, Majid Ahmadi, Hamed Haddad Khodaparast
Abstract: In aerospace engineering, the focus on innovating and optimizing the design and manufacturing processes of high-aspect-ratio composite wings is pivotal for achieving efficiency and advancements. These wings, characterized by their elongated and slender structures, utilize advanced materials like carbon fiber and employ efficient manufacturing techniques, such as vacuum bagging. The potential benefits of such wings include significantly lighter aircraft, reduced fuel consumption, and improved overall performance. However, realizing these advantages requires addressing numerous structural and aeroelastic constraints.
This research introduces an aeroelastically tailored Multi-objective, Multi-disciplinary Design Optimization (MMDO) approach that seamlessly integrates numerical optimization techniques. The primary objectives are to minimize weight, ensure structural integrity, and subsequently manufacture the optimized wing configuration. Ground Vibration Testing (GVT) is performed to validate, update, and correlate with the numerical model. The proposed numerical methodology integrates Finite Element (FE) modelling and analysis software, an in-house Reduced Order Model (ROM) framework for nonlinear aeroelastic analyses and tailoring, and using Particle Swarm Optimization (PSO) as a stochastic optimization method. This integration creates a robust numerical approach within the Nonlinear Aeroelastic Simulation Software (NAS2) package for designing composite wings with enhanced aeroelastic and structural performance. This comprehensive methodology aims to produce composite wings that meet safety and performance standards while driving cost-efficiency in the aerospace industry. The paper's contributions lie in:
• Proposing a Multidisciplinary Design Optimization (MDO) method addressing structural, composite material, aeroelastic, and manufacturing constraints for UAV wings. Optimization considers critical factors like buckling, deformations, stress limitations, composite failure, delamination constraints, flutter, and gust response restrictions.
• Emphasizing the importance of addressing geometrically nonlinear static and dynamic constraints, contributing to the optimization of highly flexible composite wings.
• Introducing NAS2, a fully automated in-house software, for optimizing and designing composite aircraft structures, offering versatility in aerodynamics and structural models for different flight conditions, wing setups, and optimization scenarios.
• Conducting manufacturing, material characterization, and experimental tests on the optimized composite wing to validate the NAS2 software and gain insights into the practical challenges of this multidisciplinary field, distinguishing the research in its comprehensiveness among studies on high-aspect-ratio composite aircraft wing design.
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16:30
30 mins
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Influence of Load Introduction Method on Wingbox Optimization with Nonlinear Structural Stability Constraints
Francesco M. A. Mitrotta, Alberto Pirrera, Terence Macquart, Jonathan E. Cooper, Alex Pereira do Prado, Pedro Higino Cabral
Abstract: The aviation industry's challenge to achieve net-zero carbon emissions by 2050 demands innovative approaches to aircraft design, particularly through the development of lighter, more fuel-efficient aircraft structures. Aeroelastic optimization plays a crucial role in this process by enabling exploration within a design space bounded by numerous constraints, including structural strength and stability. Traditional aeroelastic optimizations rely on linear buckling analyses which, while computationally efficient, tend to over-constrain the design space due to their conservative nature. Such conservatism places a glass ceiling on the sizing loads used within optimization studies, preventing the exploitation of the full load-bearing capacity, especially as aircraft designs trend towards more slender and compliant wing structures where nonlinear effects become significant. This paper builds on previous research by integrating a nonlinear structural stability constraint into the optimization of a wingbox structure under a distributed load. Three optimization scenarios are considered to evaluate the influence of different load introduction methods: distributed non-follower forces, distributed follower forces, and non-follower forces applied to a load reference axis. In addition, the formulation of the nonlinear structural stability constraint is revisited to allow its application in presence of follower forces. Our findings, demonstrated on an idealized version of the Common Research Model wingbox, confirm a substantial mass reduction using the nonlinear constraints compared to the traditional linear ones, ranging between 8 and 9%. Not much difference is found between the structures optimized with distributed non-follower and follower forces, because of their small deflections. Instead, a noticeable difference is found for the structure optimized with non-follower forces applied to the load reference axis, which achieves a smaller mass reduction. If on one hand these results suggest that employing the load reference axis approach might lead to conservative results, on the other hand we show that such approach leads to an inaccurate prediction of the structural deformation.
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17:00
30 mins
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Multidisciplinary design optimisation of an aircraft with the semi-aeroelastic hinge device
Marta Colella, Mario Peinado Garcia, Francesco Saltari, Franco Mastroddi, Fabio Vetrano, Paolo Mastracci, Andrea Castrichini
Abstract: This paper introduces a Multidisciplinary Design Optimization approach aimed at improving aircraft performance by equipping the wings with the semi-aeroelastic hinge device. New aircraft projects incorporate recent aviation technologies, including the use of lightweight materials to reduce aircraft weight and fuel consumption. An emerging technology in this field is the application of semi-aeroelastic hinge (SAH) devices, allowing for an increased wingspan and consequent reduction in induced drag, while ensuring that manoeuvring and gust-induced loads remain below critical values. Additionally, the use of SAH, complementing the folding wing tip concept, facilitates a reduction in airport taxing space. Despite numerous studies on SAH, none have explored its impact on aircraft design and performance through methodological preliminary design optimization.
This paper has the following objectives:
- Employ an in-house code to parametrically create an aeroelastic finite element-based model incorporating a semi-aeroelastic hinge device (See Fig. 1). Conduct typical manoeuvre analyses via Nastran static solver as well as flutter and gust response analyses using the formulation outlined in Castrichini et al. [1].
- Establish design constraints by hypothesising potential failure cases, foreseeing their potential integration into aircraft certification specifications.
Conduct preliminary design optimization of aircraft incorporating semi-aeroelastic hinge devices, illustrating their impact on aircraft performance. Present the results in a Pareto front, showcasing the gains in flight speed and fuel consumption.
Bibliography
[1] Castrichini, A., Wilson, T., Saltari, F., Mastroddi, F., Viceconti, N., & Cooper, J. E. (2020). Aeroelastics flight dynamics coupling effects of the semi-aeroelastic hinge device. Journal of Aircraft, 57(2), 333-341.
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