Correlation Between Electromechanical Impedance and Thermal Analysis for Adhesive Cure Time Evaluation in SHM GW Applications

Abstract

Piezoelectric ultrasonic sensors used in Structural Health Monitoring (SHM) systems are usually attached to components by using adhesives with intrinsic properties that end up affecting their frequency-response. In this work, the electromechanical impedance of sensors attached to an aluminum sheet with three different epoxy resins was monitored during curing. Impedance change indexes (CIs) were calculated and compared with cure degree estimations from Differential Scanning Calorimetry (DSC). Results show that resonance frequencies were displaced by up to 30 kHz, and amplitudes changed considerably during the curing process of the selected resins. Results indicate that certain CIs show a high positive correlation value (R=0.96) with DSC data, and could therefore be used in practical applications to evaluate the curing status of the adhesive in SHM applications.

Keywords

• Adhesive
• electromechanical impedance
• change index