Ultrasonic characterization of accelerated environmental degradation of adhesively bonded joints

摘要

A contact, dual channel angle beam ultrasonic spectroscopy system was developed for monitoring the environmental degradation of adhesive bonds. Using standard manufacturing processes, bonded samples were prepared and exposed to accelerated environmental degradation: immersion in saturated NaCl solution at 68℃ and 4.45 kN (1000 lb) load. Pixel-by-pixel normal and angle beam ultrasonic measurements were made to estimate the degradation of bondline properties: effective shear and longitudinal moduli and wave attenuations, density and bondline thickness. It is shown that the ultrasonic results provide information on damage evolution prior to failure. Specifically, adhesive creep and bondline property variation may serve as failure precursors measurable by the described spectroscopic method.