(A) reference free and non-contact method for detecting and imaging damages in adhesive bonded structures

Abstract

Adhesive bonded structures have been used widely in aerospace, automobile, and marine industries. Due to complex nature of the failure mechanisms of the joints, cost-effective and reliable damage detection is crucial for the related industries. This thesis presents an experimental and analytical candidate method for in-situ damage detection of adhesive-bonded joints. The fully non-contact method utilizes air-coupled ultrasonic transducers (ACT). Various configurations of transmitter and receiver including through transmission, pitch-catch scanning and probe holder angles are attempted and the obtained results are analyzed. The method examines time of flight of the ultrasonic waves over a spatial comparison to assess and visualize the presence of the critical damage and provide the possibility of damage localization. The proposed method works without relying on reference data obtained from the pristine condition of the target structure. Aluminum bonded plate and triplex adhesive bond with debonding weakened bonding are used to confirm the accuracy of the method. The proposed method is potentially suitable for in-situ non-destructive testing applications due to the simplicity of the mechanism and little power consumption of the ACTs.