Microscale Mapping of Fiber Strain and Damage in Composite Wrinkled Laminates Using Computed Tomography Assisted...

Area of Science:

• Materials Science
• Mechanical Engineering
• Non-destructive Testing

Background:

• Out-of-plane fiber wrinkles in carbon-fiber-reinforced polymer laminates are critical defects leading to premature failure.
• Detecting and assessing these wrinkles is challenging with current methods.

Purpose of the Study:

• To introduce a novel diagnostic technique combining X-ray computed tomography (XCT) and Wide Angle X-ray Scattering (WAXS) for in situ analysis of wrinkles.
• To enable detailed field-resolved mapping of axial and radial lattice microstrain in wrinkled laminates.
• To establish radial microstrain gradients as a reliable indicator of wrinkle severity.

Main Methods:

• In situ compression testing of carbon-fiber-reinforced polymer laminates with controlled small and large wrinkles.
• Simultaneous data acquisition using XCT and WAXS.
• Development of an orientation-aware reduction pipeline for texture classification, peak fitting, and microstrain mapping.

Main Results:

• Detailed mapping of axial (ε100) and radial (ε002) microstrain fields was achieved.
• Large wrinkles showed significant radial microstrain (-14.5 µεMPa⁻¹), while small wrinkles exhibited lower magnitudes.
• Strain hotspots correlated with delamination, matrix cracking, and fiber kink banding, confirmed by tomography.

Conclusions:

• Radial microstrain gradients serve as a robust, non-destructive indicator of wrinkle severity in carbon composites.
• The developed XCT/WAXS method provides unique insights into defect behavior.
• Findings support performance-based rejection criteria and targeted inspection in aerospace applications.