Comments on mixed-mode fracture in adhesive joints

Duer, R.; Katevatis, D.; Kinloch, A. J.; Williams, J. G.

doi:10.1007/bf00034074

Cited by 18 publications

(4 citation statements)

References 10 publications

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“…Knowing the geometry of the adherend and the load at a given crack length allowed the adhesive fracture energy, G c , of the bond to be measured [28]. With the specimen bonded to a stiff base the failure tended to propagate at, or very close to the aluminium/epoxy interface [29]. For the three-layer specimens a similar approach was used.…”

Section: Mechanical Testingmentioning

confidence: 99%

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: Mechanical Testingmentioning

confidence: 99%

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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“…In the literature, numerous works have been directed on determining strength and fracture behavior of similar material sandwiched joint. These include investigations upon the effect of bond thickness [2][3][4] , crack path propagation [5][6][7] and assessment of fracture initiation criteria [8][9][10][11][12] . It has been reported that the strength and fracture behavior of the rubber modified adhesive joint is greatly dependent on the adhesive bond thickness and existence of cracks or flaws [2,3] .…”

Section: Introductionmentioning

confidence: 99%

Fracture Toughness Test of Epoxy Adhesive Dissimilar Joint with Various Adhesive Thicknesses

Afendi

Teramoto²

2010

JMMP

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In this study, effect of bond thickness upon the strength and fracture toughness of epoxy adhesive dissimilar joint is investigated. Tensile and three-point-bending (abbreviated as 3PB hereafter) fracture tests are conducted. Finite element method (abbreviated as FEM hereafter) analysis is also executed to analyze the stress distribution at an interface corner of dissimilar joint. From FEM analysis results, it is found that the stress singularity in the dissimilar joint exists pronouncedly at the SUS304/adhesive interface corner and the order of stress singularity in the tensile model is higher than that in the 3PB model. Moreover, the order of stress singularity in the dissimilar joint having bond thickness of 1.0 mm is quite identical to the value obtained from analytical solution under the plane stress condition. From 3PB test and tensile test, it has been confirmed that the failure stress of dissimilar joint slightly increases with the decreasing bond thickness and can be well predicted by using the interface corner toughness, Hc parameter. The failure of dissimilar joints always originates from the SUS304/adhesive interface corner and the failure stress for dissimilar joint of 3PB test is higher than that of tensile test. For the specimens failed at the ALU/adhesive interface corner, the poor wettability of ALU adherend's surface plays an important role. For the dissimilar joint with an interfacial crack, the fracture toughness, Jc is calculated by J integral method in FEM analysis. Fracture toughness, Jc for cohesively fractured specimens is more or less constant but shows some dependency on bond thickness for interfacially fractured specimens. Locus of fracture can be best interpreted in terms of stress singularity order at the interfacial crack tip.

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“…The load was applied to the end of the specimen, and the load and crack length were measured. Knowing the geometry of the joint and the load at a given crack length allowed the adhesive fracture energy, G c , to be ascertained [28,29]. For both the twoand three-layer specimens the results were then displayed in a similar fashion to a 'C-scan', with a grey-level square representing the toughness at a given point on the specimen.…”

Section: Mechanical Testingmentioning

confidence: 99%

“…In the case of the two-layer specimens, each strip was bonded to a stiff aluminium-alloy base and an end block was glued to one end of the aluminium-alloy adherend. With the specimen bonded to the stiff base the failure would tend to propagate at, or very close to the aluminium-alloy/epoxy interface [29]. For the three-layer specimens a similar approach was used.…”

Section: Mechanical Testingmentioning

confidence: 99%

The Correlation of Non-Destructive Measurements and Toughness Changes in Adhesive Joints during Environmental Attack

Vine

Cawley

Kinloch

2001

The Journal of Adhesion

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Normal-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 adherends which were subjected to one of four different surface pretreatments prior to being coated (for the two-layer specimens) or bonded (for the three-layer specimens) with an epoxy polymer. The four commonly used pretreatments which were investigated were a grit-blast, a chromic-acid etch (CAE), a chromic-acid anodise (CAA) and a phosphoric-acid anodise (PAA). Techniques have been developed to measure the fracture toughness, G c , of the specimens before and after water exposure such that fracture toughness maps could be ascertained, where the measured values of G c may be assigned to spatially discrete positions within the specimens. The relative performance of the different pretreatments used in the present work followed that expected from the literature: the chromic-acid anodised (CAA) surface pretreatment giving the most durable two-and three-layer specimens and the grit-blasting pretreatment giving the least durable. In the two-layer specimens, the ultrasonic inspections detected two main types of defects: corrosion-driven edge-disbonds and micro-defects. The edge-disbonding mechanism usually started at an unsealed flush edge, and was initiated by a region of corrosion which developed on the edge of the specimen and which undercut the epoxy layer. Edge-disbonds were easily and accurately detected ultrasonically. Micro-defects were detected in regions remote from the edges and these small-scale, isolated defects took several forms. In the case of the three-layer joint specimens, only edge-disbonds could be detected ultrasonically. Nevertheless, in some of the three-layer joints which were attacked and weakened by ingressing water, the failure surfaces suggested that micro-defects were present. For both the two-and the three-layer specimens, the results from the ultrasonic scans have been correlated with the values of the fracture toughness of the specimens, before and after water exposure. Whilst the ultrasonic scans detected the presence of micro-defects in the two-layer specimens, which appeared to correlate with the extent of interphase toughness loss upon water exposure, the scans clearly failed to detect any changes in the interphase regions which would indicate the general loss of interphase toughness seen with the three-layer grit-blast and PAA specimens.

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Comments on mixed-mode fracture in adhesive joints

Cited by 18 publications

References 10 publications

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

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

Fracture Toughness Test of Epoxy Adhesive Dissimilar Joint with Various Adhesive Thicknesses

The Correlation of Non-Destructive Measurements and Toughness Changes in Adhesive Joints during Environmental Attack

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