Research Progress in Ultrasonic Testing of Defects in Aerospace CFRP Composites

Carbon fiber reinforced polymer (CFRP) composites are essential to modern aerospace structures due to their high strength-to-weight ratio and design flexibility. However, internal defects formed during manufacturing or service life critically threaten structural integrity, demanding reliable non-destructive evaluation (NDE). Ultrasonic testing has emerged as the dominant method, offering high defect sensitivity and quantitative capabilities. Yet, CFRP’s inherent anisotropy, complex layup, and high attenuation cause beam distortion, structural noise, and limited penetration—constraining inspection accuracy and efficiency. This review systematically assesses recent advances and challenges in ultrasonic inspection of aerospace CFRPs. It compares contact and non-contact techniques to define their applicability limits and analyzes optimization strategies spanning acoustic physics and intelligent algorithms. A key focus is the trend toward intelligent systems: machine learning enhances offline diagnosis but requires integration of physical models to improve generalizability and interpretability, while structural health monitoring enables a shift from post-event inspection to real-time assessment. Looking forward, we propose a development pathway centered on multi-modal sensing, physics-guided artificial intelligence, and digital twin-based prognosis. And promote the standardization of the detection process to enhance the robustness of the system. This integrated approach will support the evolution of intelligent inspection systems capable of full-lifecycle health management for next-generation aerospace composite structures.