Glass Fiber Reinforced Polymer (GFRP) is prone to damage during long-term service. Among its defects, flat-bottom hole defects are particularly challenging for achieving high-contrast imaging and precise localization. This study focuses on defect detection and imaging using a microwave reflection method. Firstly, the electromagnetic wave propagation characteristics in GFRP and the impact of internal dielectric discontinuities on reflection coefficients were analyzed. A defect localization and imaging method based on enhanced reflection features was developed. By combining reflection anomaly spectrum analysis, incrementally constrained peak identification, and fine two-dimensional spatial localization, stable detection and precise positioning of 8 mm flat-bottom hole defects with non-uniform distribution on the back side was achieved. The results indicate that this method can effectively suppress background interference, significantly improve the imaging contrast between defects and the matrix, and produce imaging results that closely match the actual defect distribution. The findings demonstrate that the proposed method is suitable for nondestructive testing and visual characterization of typical internal defects in GFRP, providing a technical reference for high-quality nondestructive imaging detection of composite material structural damage.
Key words
Microwave nondestructive testing /
Glass fiber reinforced composite material /
Defect /
Localization /
Imaging
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