Debond Detection Using Broad-Band High-Frequency Excitation and Non-Contacting Laser Vibrometer System

Abstract

A membrane vibration-based method of detecting a debond between a host structure and a composite repair patch is presented. The two distinguishing features of this new method are the excitation and the measurement. The excitation uses a non-instrusive surface-mounted piezoceramic patch and a broad-band high-frequency multi-sine sweep. The measurement uses a noncontacting laser vibrometer and converts the broad-band excitation response into a single value equal to the RMS value of the velocity. The frequency band is selected such that the local membrane vibration of the debonded area is excited, resulting in relatively higher velocity in the debond area. The work is principally experimental with a theoretical justification of the membrane resonance detection technique. Two case studies of glass/epoxy repair patches bonded to aluminum plates with corner and edge debonds, respectively, are presented. In this work, it is shown that accurate detection of composite repair patch debonds is achievable.