Damage Assessment in Composite Material Using Air-Coupled Transducers

In this paper results of damage assessment of composite panel using guided wave propagation phenomenon are presented. Elastic waves excitation is based on piezoelectric transducer (PZT) and air-coupled transducer (ACT) while the waves sensing is based on scanning laser Doppler vibrometry. It thus forms the full non-contact diagnostic approach. Thin panel made of fibre-reinforced polymer is investigated. The problem of optimal slope angle of ACT and the possibility of symmetric and antisymmetric elastic wave modes excitation is investigated. Contact (PZT) and non-contact (ACT) elastic waves generation methods and their influence on the artificial damage (Teflon inserts) localization results are compared. Moreover, the influence of single and multiple acoustic wave sources on artificial damage localization results and the problem of panel coverage area by elastic waves with large amplitudes to improve damage sensitivity are investigated. Different locations of ACTs and their influence on damage detection results are investigated. Two damage imaging algorithms based on elastic waves root mean square (RMS) energy maps and wavefield irregularity mapping (WIM) have been proposed.