Quality Assessment of Bond Interfaces by Nonlinear Ultrasonics Transmission

Quality assessment of bond interfaces in composite materials is an important task in non-destructive materials testing. Techniques to characterize or even measure the bond strength are required. Binding forces are nonlinear and cause a nonlinear modulation of transmitted or reflected ultrasonic waves. Therefore, the generated higher harmonics of an insonified monochromatic wave will give informations about the quality of adhesive bonds. This paper presents the basic physical model of this technique and investigations of the adherence of coatings on carbon-fibre reinforced carbon samples and of the bond interface in fusion-welded silicon wafers exploiting the nonlinear transmission of ultrasound. Some of the results are compared to destructive tests.