Design of an all-composite wing for a small UAV Platform. Imside the development process of FEA and Optimization software for composite structures
Tutor / director / evaluatorGhiringhelli, G.
Document typeMaster thesis (pre-Bologna period)
Rights accessRestricted access - author's decision
This work is the first movement of the design of an all composite UAV wing, helping a group of aeronautics engineering students, to increase the technologic level of its. To do that, the means and technology from CIMNE Company are used, specially a current main line of investigation in the center, the FEMCOM project. This work is included in the development of new finite element methods for analysis and optimal design of structures with composite materials. After the introduction of the motivations and the student group, it’s presented the initial construction technique of the D-box, the seed for the idea of building an entire wing made of composite material, and a test for the methodology to follow when simulating aeronautic composite structures using CIMNE’s FEA software COMPack. There are exposed the main requirements that the new structure must fulfill. Besides the global idea of enhance the use of composite materials in the wing structure, it is established the need of increase the wing structural strength and maintain the specific mass, and also, to make it more easy to be constructed by non-professional technicians. Later is presented a general picture of composite structures used in aeronautic applications. How and why the composite parts are being used in aircraft structures, and defining the advantages and benefits of using composites instead ordinary materials. The method to transform the old D-box structure made by a single layer of composite and balsa wood into an all-composite wing is planned. The final structure was defined after a decision process, started by a brainstorming, followed by a detailed evaluation of the more valid concepts, keeping in mind the main objectives. The E model specimen is chosen and the wing structure is named EV structure. After the decision of the structural morphology of the wing, the materials that will effectively form the composite parts as fibers, matrix, foams and such are decided. The decision is made after the study of the materials that are commonly used to manufacture composites structures, including a brief introduction to fiber science, woven fabrics theory and the main aspects of resin chemistry. After this the decision of the materials that will be use to simulate and construct the EV model is made, the materials are dividend in skin and core, and some special considerations of which material fits more to each part are explained, based on the general requirements of the structure and on the features of each material. After this, it’s possible to establish the first parameters of the structure and start to virtually construct and test the designed wing, by doing a Finite Element Analysis and the posterior optimization of the EV model of all composite wing. After introducing a brief part of COMPack theory and know-how, a trial load state is applied into the EV model in order to run the first introductory simulations. The first results obtained from the preliminary models served to initiate the optimization process. After a brief presentation of the optimization 16 module, a trial problem will be presented and run in order to establish optimization guidelines, and optimize the initial structure. The optimized models, named series 40’s are analyzed and finally a definitive structure configuration is defined. This structure is loaded with the full load set established by the Trencalòs Team for their future plane that will compete in the Trencalòs Team. The results of the simulation showed that the main reinforce structures (carbon tube and the carbon band on the skin) the main part of the stress, still far away of its yielding limit. Due to the method of load application, the PS foam core was damaged when increased the nominal load to 126%. The composite structure takes without any major problem the stress caused by the load set defined, but the foam is sensitive to load concentrations. This fact will be important in order to establish future lines in work. Later on, there is a discussion of the aspects related to the economic issues of this work, as a stage of the development process of CIMNE’s FEMCOM project, based in the implementation of analysis and optimization tools and software for composites structures. The cost of this work will be estimated in 52.842 €, considering all the human and technical resources that actually took part and collaborated in a active way to develop the program and get the results here presented. In addition, it’s offered the cost that represent to perform a study design or optimization of an composite part or model, in order to quantify the price of the service that CIMNE could offer after the development of this software and the possible launch into the market. Finally, it is explained the future lines of investigation established after the end of this work. Details of how this work will be carried on inside CIMNE are given, considering the problems and conclusions exposed. About COMPACK software one of the main aspects is to improve the method of defining internal loads, specially twist and bending moments to avoid artificial stress concentration zones. The implementation of a module able to apply pressure value directly to a FEM mesh is also defined as a very useful tool, as well as the need of a user manual for COMPack, which was started last month of February. Observing the good results obtained, the construction of the physic EV model is planned for this spring. In order to experimentally test the structure and compare the obtained results. The EV model is planned to take part of the new plane of the Trencalòs Team, which will compete in the next Air Cargo Challenge 2011 that will take place in Stuttgart next 12th of August.
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