Features of Laser-Vibrometric Nondestructive Testing of Polymer Composite Materials Using Air-Coupled Ultrasonic Transducers

Laser Doppler vibrometry has found application both in nondestructive testing (NDT) of polymer composite materials (PCMs) and in studies of the amplitude-frequency characteristics of acoustic emitters in a wide frequency range. The use of air-coupled systems for the excitation of acoustic vibrations in the tested objects makes it possible to carry out a non-contact NDT procedure. This expands testing facilities of composites, simplifies the quality control procedure, and minimizes external influences on the test objects in comparison with traditional acoustic NDT methods based on contact emitters. In this paper, we have investigated the features of NDT of composites by a non-contact method using scanning laser Doppler vibrometry. The results of NDT of impact damage to PCMs using several types of air-coupled systems for excitation of acoustic vibrations, namely, based on piezoelectric, magnetostrictive, and gas-discharge transducers are presented.