Abstract

Photoacoustic and photothermal nondestructive evaluation techniques are an emerging approach for the inspection of several materials of industrial interest. This paper focuses on stratified materials such as aluminum epoxy or graphite epoxy laminates as well as metallurgically coated materials which are widely used particularly in the aerospace industry. Such materials must be carefully inspected to detect the presence of any extended defect such as a layer-to-layer delamination which could grow under stress in service resulting in a catastrophic failure of the assembled structure. Such materials are usually inspected after manufacture by ultrasonic or radiographic techniques. Such approaches have however a number of limitations, so that alternative techniques which could be applied rapidly, noninvasively, and with access from one side only of the structure are actively searched. Optical techniques provide an attractive alternative to such methods because they require no contact with the inspected surface so that they can be deployed in hostile and remote-located environments, while being easy to scan over large surfaces.

© 1985 Optical Society of America