Mechanical behaviour of triaxial flat braided soft tissue repair devices

Braided textile structures are widely used in soft tissue repairs due to their high strength, flexibility, and ability to integrate with biological tissue. However, the relationships between braiding manufacturing parameters and the resulting mechanical behaviour remain poorly quantified in triaxial braids, limiting intentional design and optimisation. In this study, manufacturing parameters including take up speed and strand count were systematically varied, and the effect on mechanical behaviour quantified. Thirty-seven braid designs were tested in uniaxial tension to failure, with breaking load, stiffness, ultimate tensile strength, and a strength efficiency ratio evaluated. Correlation analysis and linear regression models with leave-one-out cross-validation were used to assess parameter sensitivity and predictive capability. The results demonstrate that strand count is the dominant predictor of breaking load across all braid constructs, while take-up speed acts as a secondary modifier that influences fibre alignment and load sharing within structurally identical groups. Engineering stress decreases with increasing strand count whereas stiffness responses depend on the interaction between bias strands and inlay yarns. The introduction of multi-strand inlay yarns significantly increases the absolute strength of flat braids, but the stiffness has a more complicated relationship depending on the detailed architecture, changing with strand-core ratio and braid angle/crimp. These findings show that the mechanical performance of braided soft-tissue repair devices can be controlled by varying manufacturing parameters. Predictive models were developed to provide a quantitative framework for optimising braided implants to meet specific mechanical requirements, supporting a more systematic and engineered approach to soft-tissue repair device design.