Objective Carbon fiber reinforced plastics (CFRP) is widely used in aerospace, automotive, and wind energy fields. However, defects such as delamination, debonding, cracks, and impact damage may occur during manufacturing and service, which makes efficient and reliable non-destructive testing (NDT) techniques necessary. Active infrared thermography has become an important method for defect detection and characterization in CFRP because of its non-contact inspection, high testing efficiency, large-area coverage, and visualized results. Therefore, it is necessary to systematically review the research progress of active infrared thermography for CFRP and clarify the applicability of different excitation methods.

Methods The basic principles, typical implementations, and research status of active infrared thermography for CFRP are summarized and analyzed. According to different excitation mechanisms, the methods are classified into optical thermography, ultrasonic thermography, and electromagnetic thermography. Typical CFRP defects, including impact damage and barely visible impact damage (BVID), artificial regular defects, interfacial debonding, and cracks, are taken as the main objects of analysis. The detection mechanisms, applicable defect types, and characterization features of different excitation methods are compared.

Results and Discussions The analysis shows that different active infrared thermography methods have different advantages in CFRP defect detection. Optical excitation is more suitable for rapid screening and characterization of thermal-resistance-type defects such as delamination. Ultrasonic excitation is more suitable for revealing interface-contact defects and micro-damage, especially impact damage and BVID. Electromagnetic excitation has targeted advantages in the detection of CFRP-metal hybrid structures. At present, active infrared thermography still faces problems in detection depth, signal-to-noise ratio, quantitative characterization accuracy, and engineering applicability.

Conclusions Active infrared thermography is an effective NDT technique for CFRP defect detection and characterization. Different excitation methods should be selected according to the defect type, material structure, and inspection requirements. Future research should focus on low-damage and coded excitation, multimodal fusion, intelligent enhancement and automatic recognition, quantitative defect inversion, three-dimensional tomographic characterization, and engineering application, so as to improve the detection reliability, quantitative characterization capability, and practical applicability of active infrared thermography for CFRP.