Structural Modeling and Bearing Capacity Analysis of Kevlar Stitch Thread-Reinforced Composites Based on a Crossed-Beam Framework

In this study, the equivalent parameter method was employed to incorporate the strength contribution of Kevlar stitch threads into the interlayer strength model. The Equivalent Parameter Method employs RVE-based homogenization theory to predict composites' macro-mechanical behavior from microstructural features. The load-bearing properties of stitched and unstitched composite structures under various loading conditions were analyzed, with a particular focus on the effects of stitching on structural performance. The reliability of the equivalent parameter method was validated through experimental data, maintaining a load error within 5%. The results indicate that under Y-axis loading, despite the increased local stiffness in the stitched region, structural bearing capacity decreased by 0.4% due to edge stress concentration. Conversely, under Z-axis and X-axis loading, Kevlar stitch threads significantly enhanced the load-bearing capacity, increasing it by 12% and 31.8%, respectively. These findings demonstrate that while Kevlar stitch threads improve the local strength of composites, the influence of stress distribution under different loading conditions and the selection of stitching configurations must be carefully considered during design. Furthermore, this study underscores the necessity of optimizing stitched composite structures based on specific application requirements to achieve optimal performance.