Microstructural Damage Characterization in Various CFRP Laminate Configurations Subjected to Fatigue Loading Using Micro‐Computed Tomography (Micro‐ CT ) and Scanning Electron Microscopy ( SEM )

ABSTRACT This study explores the evolution of microstructural damage in Carbon fiber‐reinforced polymer (CFRP) laminate with varying stacking sequences—unidirectional 0° (UD [0] ₁₂ ), unidirectional 90° (UD [90] ₁₂ ), and cross‐ply [0/90] _6S —under tension‐tension fatigue loading. Micro‐computed tomography (micro‐CT) and scanning electron microscopy (SEM), the failure mechanisms and correlation between observed damage features and fatigue life were investigated. Mechanical testing results show that the fiber orientation significantly affects fatigue resistance, with UD [0] ₁₂ laminates exhibiting early failure due to fiber fracture, while UD [90] ₁₂ laminates demonstrate longer fatigue life, primarily influenced by matrix‐dominated damage. Cross‐ply laminates exhibit a complex combination of fiber and matrix damage, resulting in an intermediate fatigue performance. Quantitative analysis of the micro‐CT data unveils the morphology of pore spaces, crack sphericity, and the distribution of crack length, providing further insight into the relationship between microstructural defects and fatigue behavior. This work highlights the critical role of laminate configuration in optimizing CFRP fatigue resistance. A comprehensive framework for understanding the complex interactions governing damage initiation and progression under cyclic loading was also established.