ASPECTS OF THE ADHESIVE BOND STRENGTH CLASSIFICATION PROBLEM.

Void or lamination detection in an adhesive bond does not present any unusually difficult inspection problems in nondestructive testing. Strength classification, on the other hand, is tremendously difficult because of the extremely small nondestructive feature signal variations that occur because of inadequate substrate surface preparation, improper cure, or chemical segregation of the adhesives in bands containing no voids or delaminations. A state-of-the-art review of the ultrasonic classification of adhesive bonds is presented in this paper along with various analytical bond model details of the influences of density, modulus, and attenuation effects on the ultrasonic signals. The results of an experimental bond strength evaluation study are also presented.