High‐Fidelity Computed Tomography‐Based Modeling of Compressive Damage in Stepwise Three‐Dimensional Four‐Directional Braided Composites

ABSTRACT Three‐dimensional (3D) braided composites are gaining prominence in demanding structural applications due to their monolithic architecture and resistance to delamination. However, conventional finite element models adopt idealized assumptions that overlook actual yarn configurations and interfacial complexities. To overcome this, a high‐fidelity finite element framework is constructed for a novel stepwise 3D four‐directional braided composite (SS3D4dBC). Leveraging micro‐computed tomography (CT), the true meso‐structure is reconstructed, including yarn spatial arrangement and cross‐sectional morphology. A progressive damage model incorporating the Puck failure criterion is embedded, enabling nuanced differentiation between intricate fiber‐ and matrix‐dominated failure modes under various loads. Then, the effect of braid angle on damage evolution and failure mechanisms during longitudinal and transverse compression is investigated. Damage initiates at yarn crossover regions under longitudinal compression, with smaller braiding angles enhancing strength by mitigating in‐plane damage. Conversely, transverse failure is governed by stress concentrations at yarn contact areas, though smaller angles also improve damage resistance. The model's simulation of stress–strain behaviors and failure strength demonstrates excellent agreement with experimental data, with a maximum error of 4.10%. This work establishes a robust, CT‐informed modeling approach that links realistic meso‐structures to macroscopic performance, providing a more powerful analytical tool for the design and optimization of advanced braided composites.