Nondestructive Evaluation of Adhesively Bonded Joints

Abstract

In this experiment, the method of phase spectral analysis was used to monitor ultrasonic moduli changes in a two part epoxy adhesive bonded between steel adherends during cure as well as during cyclic loading. Ultrasonic signals were generated using a piezoelectric transducer operated in the pulse-echo mode. These signals were digitized using a high-speed transient digitizer (100 MHz sampling rate) and stored for post-test analysis in the memory of a minicomputer. Based on this information, ultrasonic attenuation and phase velocity measurements (as a function of frequency) were obtained for both longitudinal and shear waves throughout the cure cycle. This technique was also used to monitor the cure of adhesives with different mix ratios in order to evaluate the utility of this approach for quality control purposes. The potential use of the method to study fatigue damage development was also considered.

Characterization of adhesively bonded joints using acousto-ultrasonics

“…However, when 20 MHz was employed, a correlation was observed and the reason for this was not clear. Kline et al [27] utilized the pulse-echo technique to measure ultrasonic attenuation and phase velocity in adhesively bonded steel specimens. They monitored changes in the moduli of the adhesive during cure process as well as during cyclic loading.…”