Investigation on the Damage Initiation and Evolution of 3D Woven Composites Under Compressive Loads Using In situ X ‐Ray Computed Tomography

ABSTRACT 3D woven composites exhibit excellent crack resistance and formability due to their angular interlocked structures, which also lead to complex failure mechanisms under compressive loading. In this study, the initiation and evolution of compressive damage in 3D woven composites were investigated through in situ X‐ray computed tomography (μCT). Warp and weft specimens were prepared and subjected to in situ μCT scanning at different stages of compressive loading. The crack evolution process was examined and quantitatively analyzed based on 3D reconstruction results. Furthermore, the 3D deformation fields were characterized using the digital volume correlation (DVC) technique. Although fiber yarn kinking is identified as the primary factor of load‐bearing capacity reduction in both warp and weft specimens, the mechanisms of damage initiation and progression differ significantly. Specifically, the interface cracking outside the kinking band plays a precursor role in initiating yarn kinking. Under compressive loading, the additional bending moment induces a non‐uniform strain distribution along the warp yarn, promoting the development of alternating regions of positive and negative transverse strain on the surface of the specimen. The novel experimental insights, with the key contribution being the identification of damage initiation and evolution mechanisms, provide a foundation for theoretical modeling and optimal design of 3D woven composites.