Monitoring adhesive curing in bi-layer waveguides using ultrasonic guided lamb waves

This research investigates the use of ultrasonic guided Lamb waves for real-time monitoring of adhesive curing. Two industrial adhesives with different chemical and mechanical were studied: Poly Max and Densolen Primer on an aluminium waveguide. The most sensitive Lamb wave mode-frequency combinations for each adhesive were identified. Two novel amplitude-based indices were developed to track the curing process. These indices showed a strong correlation between changes in adhesive stiffness and Lamb wave amplitude variations. The results demonstrated a decrease in Lamb wave amplitude with adhesive stiffening, enabling effective monitoring of the adhesive phase transitions and the curing process. The adhesives exhibited different overall curing mechanism with minimal room temperature influence: Densolen Primer stiffened rapidly, while Poly Max stiffened gradually. The alignment between the proposed indices and recommended cure times suggests a promising Lamb wave-based technique for adhesive cure monitoring, particularly valuable in limited-access scenarios.