Evaluation of laminated glass adhesion strength based on Lamb waves through the observation of the Schoch effect

Compared to standard plain glass panes, laminated glass has many advantages, such as improved glass panes' safety, structural strength, and aesthetics. An essential quality criterium of laminated glass, tunable during production, is the adhesion strength of the interlayer. Traditional quality control is destructive and involves peeling, tensioning, or impacting the specimens, while ultrasound may, if properly applied, reveal the quality parameters nondestructively and reduce production costs. In facilities equipped with ultrasonic phased array transducers, bounded beam effects may be exploited to investigate the considered glass panels. In this work, we provide a proof of concept of a bounded beam effect, known as the Schoch displacement, caused by ultrasonic guided waves, to map variations in adhesion nondestructively. Even though in industrial production lines, one may opt for phased array techniques to measure the effects, in this work, we provide images obtained by acousto-optic Schlieren photography for demonstrative purposes.