A novel encoded line laser array method of scanning infrared thermography nondestructive testing for CFRP defect

Abstract

This paper presents a novel encoded line laser array (ELLA) method for scanning infrared thermography nondestructive testing (IRT‑NDT) of carbon fiber reinforced plastics (CFRP). By spatially arranging multiple line lasers, ELLA generates Lock‑in like, frequency‑modulation like, and 13‑bit Barker‑coded pulse like (Barker13‑like) excitation waveforms, extending modulated thermography from static to scanning systems. Numerical simulations confirmed that ELLA heating profiles closely match static excitations. To process dynamic image sequences, pseudo‑static matrix reconstruction (PSMR) converts them into spatially static datasets, enabling established algorithms such as fast Fourier transform, thermal signal reconstruction, and matched filtering (MF). The algorithmic results demonstrated that, compared with single line laser scanning, the combination of ELLA with PSMR and post‑processing effectively improves defect detectability, even under added salt‑and‑pepper and Gaussian noise. Both the signal‑to‑clutter ratio and signal‑to‑noise ratio (SNR) evaluations confirm the effectiveness of ELLA, with overall values being improved by post‑processing algorithms. Barker13‑like excitation achieves consistently high SNR across most algorithms, and the moving average model of MF reached the maximum SNR of 12.91. Overall, ELLA integrates the rapid coverage of scanning IRT‑NDT with the sensitivity of modulated excitation, offering a feasible and efficient approach for large‑scale CFRP defect detection.