Reducing-yarn technique and flexural properties of 3D braided composites with tapered cross-section

Mechanisms of near-net-shape reducing-yarn braiding were discussed. Microstructures in yarn-reducing regions were characterized by image observation and topological analysis. Flexural properties in the tapered regions of the reducing-yarn composites or cut composites and those of the uniform composites were compared. Finally, failure mechanisms of the reducing-yarn composites and cut composites were analyzed. The results indicate that continuity of the braiding process after yarn reduction must be ensured. The reducing-yarn preforms have a trapezoid profile near the reducing-yarn cross-section. Flexural properties of the reducing-yarn composites are higher than those of cut counterparts but lower than the uniform composites. The reducing-yarn composites show compound failure modes, which are dominated by yarn breakage and also include matrix cracking and fiber pulling-out.