Influence of guide ring shape variation on braiding angle distribution of circular braided composites with rectangular cross-section mandrel

Circular braiding is an advanced manufacturing process for forming fiber-reinforced composite preforms, featuring excellent design flexibility and superior near-net-shape forming capability. However, this high-speed and flexible manufacturing method also introduces the problem of nonlinear fiber bundle distribution at the edges of the mandrel. The influencing mechanisms and control strategies regarding fiber bundle distribution remain unclear. This paper establishes a high-fidelity finite element model for radial circular braiding under the 176-carrier process based on the digital element method. It systematically compares the effects of circular and elliptical guide rings with different aspect ratios on the braiding process of rectangular cross-section mandrels, and proposes an effective method for extracting braiding angles. It has been found that the guide ring increases the difference in yarn convergence distance on adjacent sides of the rectangular cross-section mandrel by regulating the spatial position of the yarn guide points. This compensates for the inherent non-axisymmetric geometry of the rectangular cross-section mandrel, thereby effectively suppressing in-plane yarn bending, reducing variations in braiding angles between adjacent surfaces, and improving the overall uniformity of the braiding angle. This study provides a theoretical foundation and process guidance for the shape optimization of guide rings for mandrels with complex cross-sections, contributing to the precise braiding of high-performance composite preforms.