The flared folding wingtip (FFWT) is a concept presented by Airbus to increase the aerodynamic efficiency and provide a means of load alleviation. A gate-to-gate demonstration of this concept has already been presented with the AlbatrossONE, a scaled aircraft featuring the FFWT concept. In this demonstration, the aircraft fold the wingtips during taxiing to fulfil gate requirements and extends it before take-off for improved efficiency. In addition, they can be released during flight to provide load alleviation and reduce the roll rate reduction caused by the increase in the wingspan. The objective of this thesis is to further study the FFWT concept.

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.

Experimental aeroelastic data is often needed in order to validate the output of fluid-structure interaction numerical simulations or to gain insight into the physics of a problem without the need of intermediate modelling. Traditional measurement approaches in wind tunnels have relied on the simultaneous use of several measurement systems (accelerometers, strain gauges, pressure probes, PIV…) in order to capture the relevant structural and aerodynamic variables. However, this results in complex setups which are often intrusive and need to be specifically tailored for each experiment. In addition, the output of these sensors is often limited to pointwise information. This thesis proposes the use of the robotic PIV system as a versatile measurement system capable of providing simultaneous, full-field aerodynamic and structural information in a non-intrusive way. This approach involves the simultaneous tracking of Helium Field Soap Bubbles and reflective markers for the characterization of flowfield and structure respectively. To prove the measurement concept, an experiment is conducted in the Open Jet Facility at TU Delft, where the aeroelastic response of a flexible composite wing is studied. The static and dynamic deflection of the wing is measured, where the dynamic cases correspond to the wing response to discrete and continuous gusts of different reduced frequencies. Following the experiment, a methodology is developed in order to reconstruct the aeroelastic response of the wing based on this information by combining marker-tracking data and a simplified structural beam model of the wing. The results include the reconstruction of structural variables such as strains and wing-tip accelerations, and aerodynamic variables in the form of steady and unsteady, phase-averaged flowfields. Some information about the different loads acting on the wing can be recovered from the structural model and from the flowfields based on the circulation around the wing. A good general agreement is found between the reconstructed variables and the validation measurements provided by independent systems.