Discrimination of Different Levels of Adhesion in a Bi Layer Aluminum/Epoxy Structure Using Lamb Waves

The aim of this work is to bring a new knowledge of the quality of the adhesion through a collaboration between physical-chemists and acousticians. Bi layers Aluminum/epoxy samples are manufactured with different surface treatments at the interface aluminum/epoxy and with different cures of the epoxy coating in order to obtain different and controlled levels of adhesion. The treatments are mechanical (sand blasting) and/or chemical (silanization). Two cross linking of the epoxy are considered : 80% or 100%. The goal is to discriminate acoustically each level of adhesion using guided Lamb waves, by measuring the wave-number shift for a given frequency and the attenuation of the propagating modes. The experimental study is realized using a contact transducer as an emitter and a laser vibrometer as a receiver to measure the time dependent normal displacement at the aluminum surface of the propagating waves. Results show that, depending on the propagating mode, the different samples can be discriminated either by the shift of the experimental dispersion curves or the attenuation of the mode.