Solar UAV Composite Fuselage Structure Design And Optimization

Composite structure design and manufacture have been widely used in Unmanned Aerial Vehicle (UAV) field. Its lighter weight, better integral performance and longer service life have made it the optimal choice of Solar-Powered UAVs and also an important direction of Solar-Powered UAV researches. The application of composite materials increases UAV design space, but also greatly increases its design difficulty. Since the harsh requirements of Solar-Powered UAV Structure, the traditional design method with initial design, performance verification and experience-based modification has been more and more difficult to meet its design requirements, which has a long design cycle and huge workload. However, if structural optimization techniques are used to modify the size, shape, topology and other configuration information of a structure, the optimal structural form can be found that satisfies certain performance requirements and objective functions. This design method is more scientific and precise, and improves its structure design process from a experience-based level to a theoretic level. Thus, innovative structure design can be achieved.In the paper, a new solar-powered UAV composite fuselage is taken as the study object. The main contents are as follows.First, the major technical indicators and structural design requirements of the UAV are analyzed. The conversion method of fuselage aerodynamic loads into structural loads is studied and good results are obtained. Meanwhile, the mechanical characteristics equivalence theory of honeycomb composite materials is studied and equivalent material properties are computed. The finite element model of the UAV fuselage is establish in Abaqus and its static analysis is completed in order to obtain the integral strength and stiffness information as the reference for subsequent optimization.By analyzing the practical application conditions of the UAV, the form and sizes of structural beams are optimized. Pipe beam, box beam and I beam are proposed as the analysis objects. By the comparison of their finite analysis results, the box beam is chosen as the size optimization object. Taking the same weight as a constraint, the optimal sizes of the box beam section are obtained.Finally, the theories of structural optimization and topological optimization are studied. The topological optimization of the lightening holes of fuselage ribs is completed by the use of a variable density method. The design scheme based on the optimized results is compared with that of experience-based design.The results of the UAV structural beam analysis and the topological optimization results of fuselage rib lightening holes are satisfactory, which provide meaningful reference for subsequent improvement and optimization.