Cohesive Bond Strength Prediction for Adhesive Joints

Abstract

An analytical study was carried out to derive the acoustic spectral response of an attenuating bond line. A similar effort was done to relate the time-base response of an attenuating bond line to the material properties of the adhesive. In this study, resonance separation, ultrasonic amplitude ratio, and resonance depth were related to the acoustic impedance, attenuation, and sound velocity of the adhesive layer. Experimental verification of the derived correlations was provided by systematically varying the properties of Chemlok 304, a two-part paste adhesive, by mixing the adhesive in a range of proportions. Single overlap shear specimens were made with these adhesive mixtures and the adhesive properties were measured in situ with high frequency broadband ultrasonics. The ultrasonic data were reduced to yield the sound velocity, density, and attenuation coefficients of the adhesive mixtures. The specimens were tensile-tested to determine joint strength and stiffness. The strength and stiffness of the bonded joints correlated well with the ultrasonic amplitude ratio, sound velocity, attenuation coefficient, and resonance depth.

Detection of kissing bond type defects and evaluation of the bonding quality in metal/adhesive/composite structures by a wavenumber-frequency insensitive SH mode

“…Consequently, the signal treatment in this work is focused on the amplitude variations of the propagating SH wave. Experimentally, Flynn [16] and C. Gauthier et al [17][18][19] showed that the attenuation coefficient of guided waves in the medium were indeed related to the bonding strength and stiffness of the adhesives. In the field of nondestructive evaluation by SH type guided waves, mostly modes SH0, SH1 and rarely SH2 or SH3 have been exploited [20][21][22][23], aiming to identify defects of cohesive or adhesive nature or to detect the adhesive layer thickness [23].…”