Disbond monitoring at wing stringer tip based on built-in ultrasonic transducers and a pulsed laser

Abstract

An active ultrasonic diagnostic method for monitoring the occurrence and growth of a disbond at a wing stringer tip was developed and verified using built-in piezoelectric lead-zirconate-titanate transducers. The diagnosis was based on the ultrasonic arrival time delay caused by an increase in the disbond-induced wave path and can provide quantitative information on the disbond length. The change in the ultrasonic amplitude, which is a conventional measure for disbond detection, was also included in the diagnostics. Finally a single transmission and multiple reception method was used to obtain the arrival time and amplitude distributions. Another active ultrasonic diagnostic tool based on a pulsed laser ultrasonic generation was proposed for a nondestructive evaluation to obtain more reliable results on the damage detected using the built-in transducers. The diagnostics were verified using a metal skin-stringer structure as an experimental model, and then applied to monitoring the disbond at a stringer tip in a composite wingbox.