Mechanical wave measurement and gas excitation for bondline inspection

Abstract

Systems and methods for bondline inspection using mechanical wave measurement and gas excitation. A cost-effective optical interferometry technique is used to measure mechanical waves generated by gas excitation, which measurements may be used to verify the strength of a bondline of a composite bonded structure. A gas gun which produces a high-pressure short-pulsewidth gas pulse at the front free surface of the composite material. A velocity interferometer system for any reflector (VISAR) is synchronized with the controlled gas pulsation and used to measure the surface velocities. The respective shock wave-induced displacements of the back and front free surfaces are then calculated. The measured free surface displacements are compared with calibrated thresholds to determine whether a weak bond has been detected or not. Optionally, a ring magnet is aligned exactly under the gas gun nozzle to enable VISAR beam centering.