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Calculation and Design of Parameters for Four-step 3D Braided Preform with Complex Rectangular Cross Sections

The complex rectangular configuration refers to the geometrical shape jointed by two or more rectangles together. The calculation and design of parameters for 3D braided preform with simple rectangular cross-section are not suitable for those with complex rectangular cross-section because there are special microstructures in complex shaped preform. According to the unit cell models of 3D braided preform with complex rectangular cross-section, the method for computing the amount and volume of each unit cell is presented, the equation for calculating the fiber volume fraction is derived, and the relationships between preform parameters are developed. Based on the equations and relationships established, the procedure for designing the numbers of yarns arrangement is presented from preform dimensions, yarns linear density, fiber density, and fiber volume fraction. A preform with complex rectangular cross-section is designed and produced. The procedure for designing is supported by experimental results.