Structural health monitoring of bonded composite patches using lamb waves

Abstract

Bonded composite patches are an attractive way to repair cracked or corroded airframe structures because of their several advantages compared to traditional riveted doublers. However, certification issues limit the application of this technology. We present here the first step in the development of a SHM system for detecting disbonds between the patch and the structure. This will provide important information concerning the damage state of the repair. PZT discs embedded between the patch and the metallic parent structure are used to excite and detect Lamb waves. Analytical study of the ultrasonic characteristics of both structure and actuator is essential to adjust the experimental setup. Processing of experimental signals allows us to locate the damage and shows the sensitivity of the SHM system to the size of the defect.