A methodology for modeling the relationship between process and topological yarn structure of 3D rotary braided rectangular preforms

3D braided composites have been widely used in high-performance fields due to their excellent properties closely related to the special yarn structures. However, the capability to fabricate various yarn structures with flexible 3D rotary braiding method has not been systematically investigated. This paper proposes a methodology to model the process/topological yarn structure relationship of 3D rotary braided rectangular preforms. A novel algorithm is developed to trace the carrier path with machine control code, in which the carrier motion is expressed as mathematical functions of switch rotation status. Without considering yarns' volume, the lattice like ideal yarn topology is established using the yarn trajectories. To construct the real yarn topology, yarn topologies at the nodes which depend on corresponding switch rotation direction are studied. The yarn structure is explored within a representative unit owing to its repetitiveness, and specific switch rotation direction combinations which allow yarns to maintain straight in the preforms are derived.