Structure Optimal Design For All Composite Wings Of An Unmanned Aerial Vehicle

Extensive application of composite materials has become an important way todeal with the UAV (Unmanned Air Vehicle) structure lightweight, high stiffnessdesign problems. Structural performance of the wing has a crucial influence on theUAV flight performance. In order to enhance the UAV flight performance, thisdissertation launched a research work on the optimal design of the structure of anall-composite wing. The main contents of this paper include the following aspects:1) According to the requirements and index of design, an overall layout withthe three-beam and multi-wing rib was determined based on a successfully designedwing structures. The distribution of wings’ surface load was obtained through thestudy of the conversion from the aerodynamic loads to structural loads, and theboundary conditions of the wing in the physical model were also determined..2) Simplified model was built and the sensitivity analysis of main designparameters was conducted. According to that, the wing beams and skin which hadlarge influence on the wings’ performance were chosen as the optimizationobjectives. Meanwhile, a hierarchical coordination complex method was proposedaccording to the coupling problem between variables of wing beam positions and the cross-sectional dimensions, and therefore the main structure parameters weredetermined, which provided initial wing geometry model for the optimal design ofcomposite structures.3) The plyscheme optimization of the wing was conducted through stepwiseoptimization method: Firstly, the ply thickness optimization model was bulit withfinite element method to determine the optimal layer thickness. Secondly, the plysequence optimization model was built with genetic algorithm optimization methods,and according to discrete characters of the variables of composite stacking sequence,an integer coding genetic algorithm strategy was proposed and fitness function withstructure strength of the composite material as the optimization objective wasconstructed, and the solution to deal with the wing beam cross-section transitionzone was proposed. As a result, the best wing ply scheme was obtained. Theoptimization results show that he strength of composite wing structure become to1.45from0.98; the maximum deformation of the wing reduce from145.894mm to179.918mm; and the buckling load factor became1.863from1.087. Besides, stressdistribution of the wing after optimization is more reasonable and the material ismore fully utilized.4) Both theoretical model and finite element model were built and thecomparative analysis of the two modes shows that the finite element method isreliable. The main factors which had large influence on composite joints werestudied. According to the characteristics of the wing structure, the joints between thewing and airframe were designed and analyzed with finite element methods.5) Both finite element methods analysis and static test were carried out onsuccessfully designed composite wings and the test results show that the maximumerror of finite element analysis is16.95%, through which the reliability of the finiteelement analysis was verified. A comparative study was conducted between theoptimized wing and the existing wing, and the results show that: the optimizedall-composite wing of the UAV had fully met the design requirements.The research work in this dissertation provides a reference for engineering implementation of composite wing structures in the future.