A Study On The Lightweight Fuselage Design For Unmanned Helicopter

Modern battlefield environment requires Unmanned Air System to hover for longer periods of time, go greater distances and operate much more quietly than ever before. The high-endurance capabilities of such rotorcraft demands high fuel fraction and lightweight fuselage structures. The weight of fuselage structures normally takes one-third of the basic empty weight, thus it would be reasonable to design a lightweight fuselage structures through optimization methods.Due to limitations in traditional structure materials and design method, the shortcoming of conventional helicopters is the high-weight airframe which leads to a low fuel fraction. With the development of composites industry and the application of advanced optimization design methods like parameter optimization, shape optimization and topological optimization, lightweight airframe which has high fuel fraction will be achievable in the design process.This thesis based on the structural design of diverse unmanned helicopters. According to the configuration design of the unmanned helicopter, the initial layout of the fuselage structures is given by the result of topological optimization which indicates the optimal load transfer path. Then the finite element model of this airframe is built in ANSYS and the static analysis is implemented. After several modification iterations, the airframe structural design which fulfills the requirement of strength and stiffness is accomplished. At last, a Response Surface Methodology(RSM) based optimization is performed on the parameter design of composite fuselage structure. The lightweight airframe design is enabled through the whole procedure which consists of structural topological modeling, static analysis and structural design optimization.In the application of fuselage structural design, the thesis discusses two types of optimization methods, which covers the following contents:(1) optimal load transfer path in the dominant area of middle fuselage;(2) probable failure modes in the main part based on Puck failure criteria;(3) mechanical behavior of different parts of the entire fuselage structure from the result of RSM based optimization. The integrated design method which the thesis suggests provides effective reference for the fuselage structures design.