Acousto-Ultrasonic Monitoring of Glueline Curing
Keywords:Acousto-ultrasonics, ultrasonics, glueline curing, epoxy, glueline thickness
AbstractHard maple electrodes were bonded with three types of epoxies in a lap joint and acousto-ultrasonic transmission monitored during curing. The electrodes, 3.2 x 25 x 115 mm, were lapped for a 25- x 25-mm bond area. Standard acoustic emission sensors, 175 kHz transmitter and 75 kHz receiver, were used to provide an RMS voltage output, which increased as the adhesive cured. The transmission increase was quantified using a halftime to cure. The increase in transmission is comparable to the predicted increase in longitudinal modulus. Increasing glueline thickness from 0.05 to 0.5 mm caused an increase in apparent cure time as measured by the halftime. By controlling glueline temperature, an activation energy was determined from the halftime to cure.
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