Effects of yarn interlacement in diamond triaxial braid on its patterns and tensile properties

Braiding is a preform technique involving the use of interweaving yarns. In the braiding process, manufacturing parameters dictate the resulting braided structures. Although numerous models based on braided architectures have been presented to predict patterns and mechanical properties, a comprehensive braided model that considers in-plane yarn interference in braiding is yet to be established. This study introduces a pioneering predictive model for triaxial braided patterns, considering yarn interlacing during braiding. Because of yarn interference, basic and deformed patterns were fabricated within the diamond triaxial braided structure. The cover factor of each pattern and the bent axial yarns in deformed patterns were predicted using a cover-factor equation and bending discriminant. To validate the analytical model and examine the effects of the patterns on the mechanical properties, various braided preforms and composites with three different braiding angles were fabricated. The analytical model and experimental results for cover factors indicated a discrepancy of less than 6%. Based on tensile tests, the deformed pattern exhibited inferior mechanical properties compared with the basic pattern, primarily due to its bent axial yarn and larger resin-rich area. This study provides a sophisticated method for predicting triaxial braided patterns, which are applicable to braided product design and modeling.