Research of laser width variability in line laser infrared thermal wave inspection of CFRP laminates and defect reconstruction method for mobile detection

Abstract

The line laser scanning infrared thermography method is a rapid and comprehensive approach for defect detection. This study investigates the impact of line laser width on detecting Carbon fiber reinforced polymers (CFRP) defects, revealing that narrower line lasers are more effective for shallow subsurface defects, while wider line lasers provide greater stability for deeper subsurface defects. To address issues like target loss, misdetection, and leakage in moving detection, a quasi-static reconstruction method based on Discrete Fourier Transform and Principal Component Analysis (DFT-PCA) is proposed. This method tracks and localizes moving defects, converting the image sequence into a quasi-static format and applying frequency domain denoising to achieve clear defect boundaries and reduced background noise. The study further explores the optimal line laser width by analyzing the relationship between the defect diameter-to-depth ratio and the signal-to-noise ratio of the reconstructed images. The findings indicate that for defects with a diameter-to-depth ratio greater than 6, a line laser with a width smaller than 4 mm offers better detection results, whereas for a diameter-to-depth ratio smaller than 6, a line laser with a width larger than 4 mm is more effective. These conclusions confirm previous research on the varying effects of line laser width on detection performance.