Multi-Angle Crack Detection in CFRP Based on Line Laser Infrared Thermography Scanning Technology

Infrared thermography is a real-time and efficient method for defect detection. This study utilizes line laser scanning infrared thermography to detect cracks in manually laid-up unidirectional CFRP, 3D-printed CFRP cracks, and naturally occurring microcracks in CFRP deflectors. In manually layered unidirectional CFRP, detection performance is influenced by the layup direction, with cracks aligned to the layup exhibiting minimal hindrance to heat conduction, resulting in weaker high-frequency components in thermal images and poorer detection accuracy. In contrast, the composite structure of 3D-printed CFRP minimizes the impact of crack orientation. By analyzing the temperature characteristics of the crack center and thermal drag tail for cracks with varying opening angles, the study establishes a relationship between the crack opening angle, crack depth, and thermal features. Fitted curves of the ratio between crack opening angle and absolute temperature difference yielded an average <i>R</i>² of 0.9828 and MSE of 0.1287, validating the effectiveness of the proposed approach. Finally, the features of microcracks in CFRP deflector plates were effectively extracted through high-frequency filtering, which demonstrated the broad applicability and robustness of this study.