Damage imaging algorithm for non-destructive inspection of CFRP/steel adhesive joints based on ultrasonic guided wave propagation

Abstract

The paper concerns assessing the quality of the adhesive connection between a steel plate and the reinforcing CFRP laminate. A three-stage algorithm for non-destructive damage imaging was developed. As the first step, an initial study involving dispersion curves of joint components was executed to determine the material parameters and the appropriate excitation frequency. During the second step, damage identification in three-layer joints was performed using the weighted root mean square (WRMS) of the guided wave signals. A novel approach to determine the optimal values of WRMS parameters was proposed. Within the third step, the guided wavefield was recorded by scanning laser vibrometry. Visualization of the distribution of WRMS values on the surface of scanned specimens allowed efficient damage imaging. The application of statistical analysis (histograms) was used to prepare the final damage maps. The results of the investigations showed the high usefulness of the developed approach for imaging both intentionally introduced and unintended defects in adhesive joints.