MACROSCOPIC AND MODERN MICROSCOPIC NDE METHODS FOR ADHESIVE-BONDED STRUCTURES

Unlike mechanical tests, NDE methods cannot be used to obtain direct strength information. However, these methods can detect various types of flaw in adhesive joints and therefore predict the performance of the structure. Some of the methods can also be used to follow the curing processes in complex joints and the rates and mechanisms of water or solvent penetration into adhesive joints. Most of the early methods were developed for metal-to-metal joints, honeycomb structures or composite materials used in the aerospace industry. These typically macroscopic techniques include acoustic, thermographic, holographic and most of the ultrasonic and radiographic methods. More recently, microscopic techniques have been developed for problems existing in other industries and in adhesivess research and in other industries and in adhesives research and development. These methods include ultrasonic microscopy, computed X-ray tomography and NMRI. The importance of the NDE methods will increase during the next few years, because of the increasingly widespread use of adhesives in various demanding applications. Development in NDE methods can also be expected to be fast and the resolution, sensitivity and speed of evaluation will improve with computer-controlled methods. © 1991.