Abstract The effects of test environment humidity and temperature on the fatigue threshold and crack growth behavior of P2-etched and commercial coil-coated (CC) aluminum adhesive joints were studied under mixed-mode loading using aluminum asymmetric double cantilever beam (ADCB) specimens. Under dry conditions, increasing the temperature to 80 °C had an insignificant effect on the fatigue threshold, but caused an increase in the crack growth rates. At 40 °C, the fatigue behavior was insensitive to moisture at higher crack growth rates, but became sensitive to moisture level in the test environment as crack growth rates slowed to the threshold. The effect of moisture and temperature were explained by the observed changes in the crack path, which in general moved progressively closer to the more highly-strained adherend as the applied strain energy release rate, and consequently the crack growth rate, decreased. Furthermore, the residual adhesive thickness on the more highly-strained adherend, tr, increased with increasing temperature, and the crack path shifted to the hydrated aluminum oxide interface when the test environment was saturated with moisture. The degrading effect of a hot-wet environment was similar for both P2-etch and CC pretreatments. At higher crack growth rates, the joint fatigue performance was degraded solely due to the effect of the increased temperature, whereas at low crack growth rates, the fatigue performance was degraded predominantly because of elevated moisture.
Last. Jan K. Spelt(U of T: University of Toronto)H-Index: 48
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Abstract Open-faced asymmetric double cantilever beam (ADCB) specimens of toughened epoxy-aluminum adhesive joints were aged either in a constant humidity environment or a cyclically changing environment to study the mixed-mode fatigue behavior. Under constant humidity environments, the fatigue threshold strain energy release rate initially decreased with aging time until it reached a constant minimum value for long times. In contrast, the crack growth rates continued to increase with aging time...
Last. Jan K. Spelt(U of T: University of Toronto)H-Index: 48
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The effect of bondline thickness on the fatigue and fracture of aluminum adhesive joints bonded using a rubber-toughened epoxy adhesive was studied using finite element analysis. The fatigue data of Part I examined the dependence of the fatigue threshold and cyclic crack growth rate on the adhesive thickness under both mode-I and mixed-mode loading. The fracture data of Part I illustrated the relation between the adhesive thickness and the quasi-static crack initiation and steady-state critical ...
Last. Jan K. Spelt(U of T: University of Toronto)H-Index: 48
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The fatigue behavior of adhesive joints made with commercially coil-coated thin aluminum sheets has been measured using modified double cantilever beam (DCB) and cracked lap shear (CLS) specimens that avoided yielding. The thin sheets were bonded to a stiffener using a reinforcing adhesive layer. Experimental and finite element analyses demonstrated that the reinforcing adhesive layer had an insignificant effect on the stress state at the crack tip and the resulting fatigue behavior. The modifie...
Last. Jan K. Spelt(U of T: University of Toronto)H-Index: 48
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The absorption and desorption of water in two different rubber-toughened epoxy adhesives was measured gravimetrically over a relatively wide range of temperature and relative humidity (RH). The data were fitted to a new diffusion model in which Fick's law was assumed to act in two sequential stages, each with its own diffusion coefficient and saturated water concentration. This “sequential dual Fickian” (SDF) model and a Langmuir-type diffusion model were both able to model the absorption behavi...
Last. Jan K. Spelt(U of T: University of Toronto)H-Index: 48
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The fatigue threshold and slow crack growth rate behavior of a highly-toughened epoxy adhesive was studied as a function of the starting condition (fatigue precrack and fillet), testing approach and interfacial bond strength. For cohesive failure, the threshold behavior was very similar when starting from a fatigue precrack or an uncracked fillet; however, the threshold was lower when interfacial cracks grew from a fatigue precrack. When compared to the time required for a crack to reach a signi...
Last. Jan K. Spelt(U of T: University of Toronto)H-Index: 48
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The R-curve behavior of two different rubber-toughened epoxy adhesives was measured as a function of the mode ratio. A bilinear model was used to characterize the fracture resistance (R-curve) behavior from crack initiation to steady-state crack propagation. Experiments showed that the model parameters depended strongly on the loading mode ratio and the adhesive bondline thickness, but were largely independent of the crack initiation geometry. The results are relevant to the prediction of the cr...
Last. Jan K. Spelt(U of T: University of Toronto)H-Index: 48
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The fatigue threshold and the cyclic crack growth of a highly-toughened epoxy adhesive were studied under mode I and several mixed-mode loading cases and compared with the quasi-static critical fracture energies. Four different adhesive systems were examined using steel and aluminum substrates having different surface roughness, and surface treatment. The effect of increasing the amount of mode II (increasing the phase angle) on the fatigue threshold strain energy release rate and the cyclic cra...
Last. John F. Watts(University of Surrey)H-Index: 54
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The adhesive fracture energy, Gc, of metallic joints, bonded with a rubber-toughened epoxy adhesive, has been measured using monotonically-loaded tests. Such tests have been conducted in various relative humidities and in water, at 21 °C. Two surface pretreatments have been employed for the substrates prior to bonding: a simple grit-blast and degrease (‘GBD’) pretreatment or a grit-blast, degrease and silane primer (‘GBS’) pretreatment. The joints were formed using metallic substrates which were...
AbstractThe continuous casting technology is a cost effective way to produce aluminium alloy sheet. As a result, aluminium alloys produced by this technology have great potentials to substitute steel in autobody panel applications. In the present work, fatigue tests were carried out on hot band (in as received and heat treated conditions) of a continuous cast AA 5754 aluminium alloy (4 mm thick) in directions of 0, 45 and 90° relative to the rolling direction. S–N curves of the alloy were measur...
Last. John F. Watts(University of Surrey)H-Index: 54
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The present work has used an accelerated test method, based upon cyclic-fatigue testing using a fracture-mechanics approach, to study the durability of organosilanepretreated joints which were adhesively-bonded using a hot-cured epoxy-film adhesive. The silane primer investigated was γ-glycidoxypropyltrimethoxysilane (GPS). The cyclic-fatigue tests were mainly conducted in (a) a ‘dry’ environment of 25 ± 2°C with a relative humidity of 55 ± 5% and (b) a ‘wet’ environment where the joints were fu...
#1Umesh Marathe(IITD: Indian Institute of Technology Delhi)H-Index: 3
#2Meghashree Padhan(IITD: Indian Institute of Technology Delhi)H-Index: 3
Last. Jayashree Bijwe(IITD: Indian Institute of Technology Delhi)H-Index: 52
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Abstract null null Adhesion of polymer reinforced with TiC (Titanium carbide) nanoparticles (NPs) with steel surface is controlled by various factors. The research findings have revealed the multiple extents of contributing factors such as the role of adhesion of NPs and micro-particles (MPs) with steel surface depending on surface free energy (SFE), their friction depending on the shape, amount, and size against a steel surface and their reinforcement action in PAEK (polyaryletherketone) leadin...
Abstract The present contribution focuses on the effect of adherend surface roughness on the strength of adhesive joints, which are particularly cost-effective and extensively applied in a wide range of industrial applications. However, the reliability of such solutions is a critical concern for the integrity of commercial products. To gain a deeper understanding on the effect of roughness, an extensive experimental campaign is proposed, where thermoplastic substrates are produced with a specifi...
To analyze the long-term monitoring reliability and life expectancy of FBG-based steel strands, accelerated corrosion and tensile tests were carried out and a life-prediction model was constructed. The validation test results indicated that the monitoring strain sensitivity of FBG-based steel strands decreases with an increase in solution concentration and time in a corrosive acidic environment. When the sensitivity dropped to about 80% of its initial value, the FBG sensor suddenly failed. The l...
Fatigue failure cracking under fluctuating stressing has been a major concern of engineering for many years. Fatigue failures have become more common and thereby significantly influencing engineering design as sources of vibration and dynamic loading of components have increased. The repairs of damaged metallic structures using bonded composite patch have been proved as an economical method to increase the fatigue life of damaged structures. This paper deals with an experimental study on the fat...
With the aim of understanding failure modes in the peeling of silicone-based adhesive joints and, in particular, the occurrence of adhesive or cohesive failure, an experimental campaign has been co...
The present contribution focuses on the effect of adherend surface roughness on the strength of adhesive joints, which are particularly cost-effective and extensively applied in a wide range of industrial applications. However, the reliability of such solutions is a critical concern for the integrity of commercial products. To gain a deeper understanding on the effect of roughness, an extensive experimental campaign is proposed, where thermoplastic substrates are produced with a specified roughn...