New 3D Braiding Method with Bidirectional Interlock for Variable Cross Section Preforms

An innovative 4StepPlus three-dimensional braiding method is proposed for the fabrication of solid nonuniform-cross-section composite fiber preforms. The method allows braid unit cells to be individually activated and deactivated after each braiding cycle using computer numerical control (CNC) for applications where changes in part cross-section require the addition or removal of yarns. Also, the unique ability to move yarns in any of four directions allows the yarns to be relocated to new positions for applications where the different cross-sectional shapes have similar cross-sectional areas. The ability to incorporate interlocking yarns in two directions enhances the preform"s integrity during handling and subsequent processing. Compactness of machinery and high carrier density will reduce fiber damage and produce uniform braid across the part"s width. While likely to be slower than rotary-type equipment, the flexible apparatus can be modularly built up in differing complexities depending on the areas to be changed during manufacture, thus keeping costs to a minimum. Modeling of the 4StepPlus process will be performed, and scaled prototypes of the composite preforms will also be fabricated and delivered to demonstrate the ability to change cross sections.