Nondestructive Testing for Environmental Degradation of Adhesive Joints

The Correlation of Ultrasonic Measurements with Toughness Changes During the Environmental Degradation of Adhesive Joints

“…The three-layer specimens are designed to be more representative of a genuine adhesive joint. Previous work had indicated that environmental attack was more likely to advance interfacially, as opposed to through water uptake in the epoxy [5]. To allow the very edge of the epoxy layer to be interrogated ultrasonically through the aluminium, it is necessary for the aluminium to extend beyond the edge of the epoxy.…”

“…The scanning system used allows for scanning at a resolution of 10 )lm. The other technique that has been used extensively is oblique incidence scanning [5]. This has involved using a pair of probes at oblique incidence to generate shear waves in the aluminium at around 37 degrees, by mode conversion at the water-aluminium interface.…”

The Ultrasonic Detection of Environmental Degradation in Adhesive Joints

“…Also, the relatively thick epoxy layer allowed a large separation between the reflections of the ultrasonic waves from the different layers. Previous work had indicated that environmental attack was more likely to advance interfacially, as opposed to via water permeation through the epoxy [7]. To allow the very edge of the epoxy layer to be interrogated ultrasonically, through the aluminium alloy substrate, it was necessary for the aluminium to extend beyond the edge of the epoxy.…”

“…The second technique that has been used extensively was oblique incidence scanning [7]. This involved using a pair of probes at oblique incidence to generate shear waves in the aluminium at around 37°, by mode conversion at the water-aluminium interface.…”