The characterization of oxide layers in adhesive joints using ultrasonic reflection measurements

Cawley, P.; Pialucha, Tom; Zeller, B. D.

doi:10.1098/rspa.1996.0101

Cited by 16 publications

(11 citation statements)

References 22 publications

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“…However, the signals produced by the LS and SL reflections from the interface always appear at the receiver at same time and so cannot be separated. Previous work [8] showed that the shear-shear reflection coefficient at an angle of 32 0 in the aluminium was likely to be the most sensitive to changes in the properties of the oxide layer at the interface. This also has the advantage of being beyond the longitudinal critical angle, so the received signal is simplified.…”

Section: Ultrasonic Techniquesmentioning

confidence: 99%

“…Similar two-layer specimens were employed in earlier work by Cawley et al [8] and also by Wylde and Spelt [26]. The two-layer specimen was chosen for several reasons: an exposed epoxy layer would allow water to diffuse through the epoxy to the interface in a uniform manner, so possibly making the degradation more uniform and easier to detect.…”

Section: Specimensmentioning

confidence: 99%

“…This also has the advantage of being beyond the longitudinal critical angle, so the received signal is simplified. The tests reported in [8] were a series of point measurements, the transducers being aligned carefully at each test point. In the work reported here it was important to scan the specimens so that any localised changes would be detected.…”

Section: Ultrasonic Techniquesmentioning

confidence: 99%

“…Four basic categories of ultrasonic technique have been investigated [4]. These are ultrasonic reflection coefficient measurements at normal-and/or oblique-incidence [5][6][7][8]; Lamb wave measurements [9][10][11]; the propagation of true guided waves in the adhesive layer [12][13][14][15]; and the measurement of the zeroes of the reflection coefficient from the adhesive layer, which is related to the propagation of leaky guided waves along the layer [16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

“…unchanged normal stiffness and tangential stiffness reduced to zero), but also holds for more realistic cases. All the techniques discussed in [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] use ultrasonic waves which have components which do not propagate normal to the interface. Calculations based on likely interphase-layer properties [4] indicated that the measurement of oblique-incidence reflection coefficients is likely to be the most promising technique in practice, since its sensitivity to the interlayer characteristics is at least as good as that of the other methods and the reflection coefficients are relatively insensitive to small changes in the bulk adherend and adhesive properties.…”

Section: Introductionmentioning

confidence: 99%

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Comparison of normal and oblique incidence ultrasonic measurements for the detection of environmental degradation of adhesive joints

Vine

Cawley

Kinloch

2002

NDT & E International

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SummaryNormal-and oblique-incidence ultrasonic scans have been conducted on two-and three-layer adhesive-joint specimens exposed to water at 50 o C for periods of up to 18 months. The joints consisted of aluminium alloy adherend(s) which was subjected to one of four different surface pretreatments prior to being coated (for the two-layer specimens) of bonded (for the three-layer specimens) with an epoxy polymer. Overall, the oblique-incidence technique detected the same types of defect as the normal incidence scans, except when the resolution was too poor to detect the smallest defects. No defect was detected using oblique-incidence scans that could not be detected using normal-incidence scans. In the two-layer specimens, two main types of defects were detected: edge disbonds and micro-defects. Micro-defects were detected in regions remote from the edges and these small-scale, isolated defects appeared took several forms. In the case of the two-layer specimens, the detection of micro-defects was clearly a strong indicator that the interphase of the specimen had been attacked and weakened by the ingressing water molecules and, indeed, the number of such defects correlated to the loss of interfacial toughness. In the case of the three-layer specimens, the extent of edge disbonding was much lower than compared to the corresponding twolayer specimens. Also, no micro-defects were detected ultrasonically in any of the three-layer specimens. However, examination of some of the failure surfaces from the three-layer specimens suggested that some micro-defects may have been present but that they were too small to be detected at the spatial resolution of the ultrasonic scans. Therefore, for the three-layer joint specimens, there were no indicators from the ultrasonic scans which could reveal whether the joint had suffered attack and weakening of the interphase regions by the ingressing moisture. Finally, for all the tests conducted it was very noteworthy that there was no evidence of a gradual change in either the normal-or oblique-incidence reflection coefficient moving into an apparently wellbonded region from either the edge disbonds or the micro-defects, when present.

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Section: Ultrasonic Techniquesmentioning

confidence: 99%

Section: Specimensmentioning

confidence: 99%

Section: Ultrasonic Techniquesmentioning

confidence: 99%