Microscale Mapping of Fiber Strain and Damage in Composite Wrinkled Laminates Using Computed Tomography Assisted Wide‐Angle X‐Ray Scattering

Out-of-plane fiber wrinkles in carbon-fiber-reinforced polymer laminates trigger premature failure, yet remain difficult to detect and assess. This study introduces a powerful new diagnostic capability: the pairing of X-ray computed tomography (XCT) and Wide Angle X-ray Scattering (WAXS) during in situ compression of specimens containing small (0.2 mm) and large (0.5 mm) wrinkles. This approach enables, for the first time, detailed field-resolved mapping of axial ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mi>ε</mml:mi> <mml:mn>100</mml:mn></mml:msub> <mml:annotation>$\varepsilon _{100}$</mml:annotation></mml:semantics> </mml:math> ) and radial ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mi>ε</mml:mi> <mml:mn>002</mml:mn></mml:msub> <mml:annotation>$\varepsilon _{002}$</mml:annotation></mml:semantics> </mml:math> ) lattice microstrain. A new orientation-aware reduction pipeline supports texture classification, peak fitting, and per-point zero-load referencing, requiring minimal intervention and enabling scalable industrial deployment. In large wrinkles, radial microstrain reached -14.5 µ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:mrow><mml:mi>ε</mml:mi> <mml:mi>MPa</mml:mi></mml:mrow> <mml:annotation>$\varepsilon \mathrm{MPa}$</mml:annotation></mml:semantics> </mml:math> ^-1, compared to -11.0 µ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:mrow><mml:mi>ε</mml:mi> <mml:mi>MPa</mml:mi></mml:mrow> <mml:annotation>$\varepsilon \mathrm{MPa}$</mml:annotation></mml:semantics> </mml:math> ^-1 axially; small wrinkles exhibit approximately one-third of this magnitude. Strain hotspots are identified prior to failure, and tomography confirms these regions as the origin of delamination, matrix cracking, and fiber kink banding. To verify the results analytically, a compact, orientation-aware predictor is developed, reproducing measured fields with a mean absolute error on the order of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msup><mml:mn>10</mml:mn> <mml:mrow><mml:mo>-</mml:mo> <mml:mn>3</mml:mn></mml:mrow> </mml:msup> <mml:annotation>$10^{-3}$</mml:annotation></mml:semantics> </mml:math> . These findings establish radial microstrain gradients as a robust, non-destructive indicator of wrinkle severity, providing unique insight and enabling defect behavior to be embedded into full-scale modeling. This supports performance-based rejection criteria and targets inspection in aerospace laminates.