Impedance Profiling for Bond Strength Evaluation

Measurement of the strength of adhesive bonds in multi- layered structures is of increasing importance. Ultrasonic NDE methods do not directly determine the strength of a bond but indicate characteristics of a bond which may be related to bond strength through empirical relationships. One such bond characteristic is its acoustic impedance. Impedance profiling methods have long been studied in the field of geophysics and medical ultrasonics [1,2]. In this paper the development of an inversion algorithm based on the so called Goupillaud equal travel-time method is described [3], with the aim of applying it to the NDE of adhesive bonds.