Damage Detection of CFRP laminates by using Ultrasonic Lamb Wave with a Sparse Array

Guided ultrasonic wave array have found many applications in detection and localization of damage in structural health monitoring (SHM) and non-destructive testing (NDT) of plate-like structures. For accurate and reliable monitoring of large structures by array systems, a high number of actuator and sensor elements are often required. In this paper, A minimum redundancy sparse array is adopted to realize high resolution and accurate damage imaging in carbon fiber reinforced polymer (CFRP) laminates, considering the energy skew effect and dispersion of Lamb wave. The Lamb wave wavenumber curve of A0 mode with its geometric relationship is used to calculate the skew angle. In order to avoid the dispersive phenomenon, the array beam-forming and imaging algorithm is presented in frequency domain by applying phase delay to each frequency component. A cross-shaped sparse array is designed according to minimum redundancy linear array. In the experiment, a PZT is used to generate Lamb waves, and a scanning laser doppler vibrometer (SLDV) is used to receive signals by arranging the scanning points in a sparse array. Experimental Results indicated that the proposed sparse array combined with imaging algorithm can locate defects of CFRP laminates with high accuracy while decreasing the processing costs and the number of required transducers. This method can be utilized in critical structures of aerospace where the use of a large number of transducers is not desirable.