Detailed study and optimization of wing morphing concepts

Abstract

Consulta en la Biblioteca ETSI Industriales (9197)

[EN] The research presented in this thesis investigates the optimal ways of changing the shape of a wing. Nowadays, this adaptability has been achieved by means of multiple mechanisms like flaps, slats, variable wing sweep and variable wing angle of attack among others. In this way, the aircrafts undergo certain geometrical changes to enhance or adapt to their mission profiles. State-of-the-art is still quite far of using the morphing concept, so the disadvantages of the weight, complex and conventional hinged control surfaces or high lift devices which provide discrete geometry changes, have led us first of all to look into the more advanced and promising materials, which are known as smart materials, in order to implement them as distributed actuators.

In this thesis we have principally focused on Shape Memory Alloys (SMA) and Dielectric Elastomers (DE). Thereby, we have try to figure out the best possible way to combine them in order to take advantage of their most important and profitable properties, thus ensuring that their disadvantages were compensated.

With the purpose of developing a morphing wing concept including these smart materials, we needed to obtain numerical models of them. Concerning DE, also called Electro-active Polymers (EAP), a validated Finite Element model already exists [1], and it was used in our simulations. Concerning the SMA however, no such model was available. The first step was to carry out some research about SMA applications and its physical behavior, and then multiple tests were performed in order to find out how the SMA performs under certain conditions. Afterwards, a Finite Element representation of it could be made.

After analyzing some of the preliminary morphing concepts already studied, we created a new 3-dimensional model of the so-called ¿fishbone concept¿. The improvements applied to this numerical model, carried out during this phase of the work, concerned firstly the extension to the third dimension; and secondly the introduction of a reliable numerical behavior of the SMA and EAP. Logically, being this wing a compliant structure, it is highly influenced by the aerodynamic loads to which it is subjected, thus the analysis has been based on a coupled structural and aerodynamic points of view.

Once we managed to have an initial structural design, the next step was to subject the structure to an optimization phase by indentifying the parameters with maximal influence in the morphing capabilities. The objective of this optimization was to increase the aerodynamic performance, with specific aerodynamic goals, not by prescribing pre-determined target geometrical shapes but altering the design of some components of the structure, until the best design was found. Afterwards, a demonstrator based on the determined morphing concept has been manufactured.

Every part of the demonstrator was built, structural tests were carried out on them before assembling the various components, and detailed comparisons with the results of the numerical model in terms of achieved shape, amplitude of deformation and blocking force have been carried out. During this step, the numerical analysis was correlated with the results of every test carried out on the prototype until they matched as close as possible. The experience gained in this part of the thesis enabled us to identify the areas of improvement in the prototype production procedures and both structural and aerodynamic issues.

Part of this thesis has been performed with Daniël Peeters who wrote his semester project in relation to this topic [2]. Thereby, the interested reader is referred to his semester thesis for the results of the work our previous work mainly concerning the SMA study in which some important aspects are more deeply detailed.