Monitoring of resin curing and hardening by ultrasound

A major aspect regarding the attainment of the desired properties for epoxy composite materials, bonded repair as well as repaired structural components via resin infusion is the control of the curing of the employed thermoset. This is required in order to distinguish the different stages of the structural formation and to provide adequate conditions for proper epoxy impregnation. In this study, ultrasonics was employed for the monitoring of the polymerization of a typical epoxy system. A wave generator was connected to a sensitive acoustic emission transducer in order to transmit elastic waves through the thickness of setting and hardening epoxy. The acquisition was conducted by another sensor of the same type acting as receiver. Different parameters like the wave velocity and attenuation are monitored in order to examine the rate of hardening. Results show that the changes in viscosity and elastic modulus with time can be monitored by the changes in the wave parameters. The effect of temperature is also discussed.

► We report on the detailed and continuous monitoring of epoxy curing by ultrasound.
► Wave duration is employed in conjunction with velocity and amplitude for monitoring.
► The influence of temperature on the rate and the final degree of curing is assessed.
► Changes in the viscosity and structure of the epoxy are successfully identified.