Online Stress Characterization of CFRP Plates Based on Multi-Frequency Lamb Wave Group Delay Feature Fusion

This paper presents a stress monitoring scheme for carbon fiber-reinforced polymer (CFRP) plates based on the acoustoelastic effect of Lamb waves. The scheme fully integrates redundant information and improves the accuracy of stress characterization. While Lamb waves offer abundant information due to their dispersion characteristics, they also pose challenges for feature extraction. Additionally, the high sampling rate of traditional strategies limits the real-time performance of monitoring systems. To address these issues, a group delay extraction method based on Gaussian pulse fitting is applied. In regions where wavenumber and frequency are approximately linear, the dispersion distortion response under Gaussian excitation is a new Gaussian function, which is the basis of high-precision delay parameter identification. Finally, laboratory experiments are conducted to evaluate the performance. After calibrating the stress coefficients, a tensile test is carried out within the range of (0–150) MPa. The maximum error is 13.2 MPa. The experimental results show that the proposed method can achieve high-accuracy stress characterization.