A Study on the Effects of Annular Weft Insertion Paths and Tensions on the Impact Property at the Joints of 3D Woven Composites With Closed Sections

ABSTRACT The demand for the integrated formation of the preforms with closed sections is surging, and the problem of enhancing their joints needs a quick solution. In this study, novel methods for annular weft insertion path design and a universal calculation formula of the length differences across layers are developed. A 3D shuttle loom was employed with “flattening‐weaving‐reduction” process to weave nine groups of tubular preforms with different weft insertion paths and tensions. Following the weaving process, the joints were adjusted to the center using the “reduction‐centering‐flattening” method before being cut and cured. Then, Charpy impact tests were conducted to collect force‐displacement and energy‐displacement curves for analysis. The results indicate that both parameters influence the impact property at the joints. With increasing tension, the final energy absorption and failure displacement initially increase before decreasing across all paths. In addition, cross‐layer weft yarns in Path 1 are relatively parallel with few intersections, resulting in the poorest load‐bearing capacity and impact strength. In contrast, Path 2 has numerous intersections, achieving the highest impact strength and absorbing up to 6.22 J at the tension of 0.375 N. Furthermore, Path 3 features multiple intersections that converge at a single point, providing superior load‐bearing capacity and stiffness.