Transverse Damage Localization and Quantitative Size Estimation for Composite Laminates Based on Lamb Waves

The damage detection method for composite laminates introduced in this research uses piezoelectric (lead zirconate titanate, PZT) transducers to excite/sense the Lamb wave signals. The complicated wave signals scattered by damage are accurately processed using a continuous wavelet transformation (CWT) based on the Gabor wavelet. The transducers are arranged on a composite laminate in the form of a network of square detection cells and triangular subcells. The damage location is estimated using the concept of centroid in two-stage detection method. The first stage detection is carried out by exciting a transducer at the center of each detection cell to locate the damaged cell and subcell. The damage localization is improved by exciting an additional transducer at the corner of the damaged subcell during the second stage detection. The damage size is then quantitatively estimated using cubic spline curve (CSC) and elliptical parametric (EP) methods based on the damage edge points. The damage location is estimated in two detection stages for high-accuracy because the damage edge points are calculated with reference to the estimated location of the damage. The arrangement of transducers and signal processing technique remain the same at all the stages of damage detection. Results from previous detection stages contribute to the improvement of damage detection in the subsequent stages. The size of detection cell plays a crucial role in designing the detection stages, and the proposed method can accurately quantify both location and size of the damage in composite laminate.