| A CAD system for 3D braiding process design has been developed in this thesis. The code has been wrote by using the latest assembled developing tools --Visual C+ +.Net, under the environment of the Microsoft Windows 2000.The mathematical model is defined for the process design on the basis of the microstructure of 3D braided composites. The defined unit cells have the brick shape which height is equal to the braiding pitch, and oriented in the same reference coordinate as the composites. The elliptical cross-section is assumed for the braiding yarn, which is more approximate to the realistic situation of the yarn in the composites. According to the topological analysis of the unit cells, the relationship between the braiding parameters is established, such as braiding angle, braiding pitch, fiber volume fraction, dimension of composites etc.. Based on the mathematical formulas, the mainly process design parameters can be calculated by the iterative method.The 3D braiding CAD system is the special application during the course of 3D braiding process design, developed by using the object-oriented technology. It runs on the PC, not like the old system that can only run on the special system environment. The system adopts the standard Windows user interface, has characters of computing fast, handling easily and friendly interface. It is made up of the file subsystem, the drawing subsystem and the process design subsystem on arranging yarns, it has realized the functions of drawing graph, picking graph, editing graph, saving graph and process designing. The c omputed d ata a pproximates t he e xperimental d ata. With t he research of the system, the process design of 3D braided preform is made totally by computer. The technicians are freed from the complex work, theprecision and speed of process design are enhanced, which contributes greatly to the design quality of 3D braided composites.
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