This study investigates the aerodynamic benefits of integrating trailing edge camber morphing on the strut of a regional strut-braced wing aircraft designed to cruise at Mach number of 0.5. Strut-braced wings are recognized for their weight advantages in high aspect ratio designs compared to the equivalent cantilever wings since the strut decreases the main wing’s bending moment. Hence, the induced drag component can be reduced due to the high aspect ratio without increasing the weight of the main wing. However, the strut increases the parasite drag component highlighting the need for innovative methods to improve the strut-braced wing overall aerodynamic efficiency. Recent studies have shown the significance of strut shape in the overall drag reduction and the necessity of maintaining high aerodynamic efficiency in off-design conditions. In this work, a genetic algorithm was utilized in conjunction with a mid-fidelity aerodynamic model to optimize the morphing strut trailing edge geometry across a range of climb and cruise conditions. The optimization objective was the minimization of drag and the design variables were the equivalent trailing edge deflection angles in seven sections of the strut. The results demonstrate a drag reduction of 0.5% to 3% both in climb and cruise. For lift coefficients below 0.8, the drag reduction is mainly attributed to the redistribution of the loading and the induced drag component reduction. In contrast, at lift coefficients above 0.8, the parasite drag component decreases due to the increased region of laminar flow over the upper wing surface.@en

High aspect ratio strut-braced wing aircraft can significantly reduce the induced drag while limiting the weight penalty of increasing the wingspan. As part of the Hybrid Electric Regional Wing Integration Novel Green Technologies (HERWINGT) project, a multifunctional morphing strut is being investigated. In this study, an optimization framework is proposed to define the thickness distribution of the morphing trailing edge of the strut to achieve the desired operational shapes while considering laminate manufacturing guidelines and material allowables. The optimizer finds designs capable of achieving the objective shapes and provides load and mass estimations that can be used to make design decisions. The output of the optimization will be used for the future detailed design, manufacturing and mechanical testing of a multi-functional strut demonstrator.@en

This study explores the implementation of aeroelastic tailoring in the design of a regional aircraft featuring a strut-braced wing (SBW). Making use of the aeroelastic optimisation framework from Delft University of Technology, PROTEUS, the research addresses two distinct cases. The first case involves a simplified SBW geometry to validate the modifications of PROTEUS, which were conducted to include the strut in the aeroelastic analysis. Static and dynamic load cases are compared with a NX Nastran aeroelastic model, showing good agreement in displacements, strains, and gust response. In the second case, the study investigates the weight-saving potential of aeroelastic tailoring in an SBW aircraft based on the ATR-72. Three optimisation scenarios, allowing various laminate types, are examined: unbalanced symmetric laminates, balanced symmetric laminates, and a thickness optimisation with a prescribed balanced symmetric stacking sequence. The results reveal that the prescribed stacking sequence limits stiffness tailoring, thereby also reducing potential weight savings. Moreover, the study shows how the presence of a strut reduces wing deflections, limiting the effectiveness of aeroelastic tailoring.@en

Previous numerical and experimental studies have shown the load alleviation capabilities of the flared folding wingtip. However, they have also shown the complex dynamics of the system and the limitations in the results obtained by modeling such an aeroelastic system using linear models, which cannot capture the effects of the large wingtip deflections. Therefore, the current study presents a nonlinear time domain flexible multibody model comprising a linear beam representing the main wing, and a rigid body representing the wingtip and its nonlinear effects. In addition, the time domain model allows the simulation of the hinge release based on the load threshold, which was also studied experimentally. The structural model is coupled to quasi-steady aerodynamics strip theory to model the aerodynamic loads. The aerodynamic model is refined using the experimental steady-state results from the previous work and then compared to the experimental gust response from the same study. The model presents good agreement with the experimental results in the case of low and moderate-frequency gusts. However, the agreement is worse for high-frequency gusts as expected due to the assumption of quasi-steady aerodynamics. Furthermore, the model captures the same trends observed in the experiment for the hinge release load threshold. Finally, the time-marching model is also used to assess the nonlinear stability boundaries and the occurrence of limit cycle oscillations.@en

This study presents an aeroelastic wind-tunnel experiment to identify the influence of the wing stiffness and hinge release threshold on the gust load alleviation performance of a folding wingtip design. Five models with different stiffness and tailoring properties are tested, and the wing root bending moment at different conditions is compared to the response with the locked-hinge condition to assess the impact on the gust load alleviation capabilities of the folding wingtip. The results show that the structural properties do not have an important impact on the peak load alleviation but the hinge release threshold and timing do. Releasing with the correct timing can reduce significantly the peak loads. However, the dynamics of the system are affected by this release; the flutter speed is decreased, and, although the performance can improve, load oscillations increase, which can be considered detrimental for reasons such as fatigue or passenger comfort.@en

The ram air inlets flaps are used in some aircraft to modulate the amount of ram air cooling the Environmental Control System. The current flap design features two metallic plates connected with a hinge. The present work studies an alternative design that replaces the metallic plates with a single composite laminate with morphing capabilities. An optimization framework is proposed to define the thickness distribution of the laminate taking into account the desired operational shapes, manufacturing guidelines and maximum allowable strains. This framework combines linear and nonlinear simulations to account for the large deflections while limiting the computational cost of the optimization. The results of the optimization framework are discussed at the end of the paper and next steps are formulated.@en

An aeroelastic wind tunnel experiment to identify the influence of the wing stiffness and hinge release threshold on the gust load alleviation performance of a folding wingtip design is presented in this study. Five models with different stiffness and tailoring properties are tested and the wing root bending moment at different conditions is compared to the response with locked hinge conditions to assess the impact on the gust load alleviation capabilities of the folding wingtip. The results show that the structural properties do not have an important impact on the peak load alleviation but the hinge release threshold and timing do. Releasing with the correct timing can reduce significantly the peak loads. However, the dynamics of the system are affected by this release: the flutter speed is decreased and, although the performance can improve, load oscillations increase, which can be considered detrimental for reasons such as fatigue.@en