Nondestructive testing (NDT) is nothing new. Applications for the non-destructive evaluation of adhesive joints date back to the early 1970s. The first pioneers used ultrasonic and infrared methods to detect voids and loose bonds in poorly made aircraft parts such as honeycomb panels. Today, NDT is routinely used in the aerospace industry, and its use is growing in automotive and other industries.
However, NDT is not for everyone. Even though there is a new generation of high tech NDT instrumentation, when it comes to adhesives bonds, NDT provides mostly qualitative interpretation. It is still difficult or impossible to determine quantifiably how strong a bond is. The most difficult defect to find are those related to improper curing and surface treatments. Therefore, great care and control must be given to surface-preparation procedures and shop cleanliness.
Furthermore, NDT encompasses a number of technologies, and not all are equally good in finding a specific defect. Certain technologies will be optimum depending on the type of defect that you are looking for, the part geometry, and the materials used to create the joint.