Detectability of kissing bonds using the non-linear high frequency transmission technique

Kissing bonds are adhesive bonding defects and are thought to arise from either contamination of the surfaces during manufacture or various forms of environmental attack. . When adhesives are used for safety critical applications the current method is to undertake extremely careful process control. None-the-less premature failure of adhesive joints still occurs and kissing bonds are often the most likely cause. Despite the need of detection of kissing bonds, they are difficult to be detected using conventional non-destructive testing techniques such as ultrasonics since the thickness of kissing bonds is many orders of magnitude less than an ultrasonic wavelength. However, kissing bonds can exhibit a strongly non-linear ultrasonic response when a high amplitude of ultrasonic wave propagates through the kissing bonds area. This paper concerns a study of the detectability of kissing bonds in adhesive joints using the non-linear high frequency transmission technique (NHFTT). Three specimens with perfect and imperfect bondings were tested using the NHFTT and non-linear parameters of them were measured to judge the conditions of the adhesive joint.