The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform
Keiji Tanaka - One of the best experts on this subject based on the ideXlab platform.
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Entropy-driven segregation in epoxy-amine systems at a copper interface.
Soft matter, 2021Co-Authors: Satoru Yamamoto, Keiji TanakaAbstract:The composition of an epoxy resin at the interface with the Adherend is usually different from that in the bulk due to the enrichment of a specific constituent, a characteristic called interfacial segregation. For better adhesion, it should be precisely understood how epoxy and amine molecules exist on the Adherend Surface and react with each other to form a three-dimensional network. In this study, the entropic factor of the segregation in a mixture of epoxy and amine at the copper interface before and after the curing reaction is discussed on the basis of a full-atomistic molecular dynamics (MD) simulation. Smaller molecules were preferentially segregated at the interface regardless of the epoxy and amine, and this segregation remained after the curing process. No segregation occurred at the interface for a combination composed of epoxy and amine molecules with a similar size. These findings make it clear that the size disparity between constituents affects the interfacial segregation via the packing and/or translational entropy. The curing reaction was slower near the interface than in the bulk, and a large amount of unreacted molecules remained there. Finally, the effect of molecular shape was also examined. Linear molecules were more likely to segregate than round-shaped ones even though they were similar in volume. We believe that these findings, which are difficult to obtain experimentally, contribute to the understanding of the interfacial adhesion phenomena on a molecular scale.
D. R. Arnott - One of the best experts on this subject based on the ideXlab platform.
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The Influence of Adherend Topography on the Fracture Toughness of Aluminium-Epoxy Adhesive Joints in Humid Environments
The Journal of Adhesion, 2001Co-Authors: An Rider, D. R. ArnottAbstract:The Adherend Surface topography has a dramatic effect on the durability of structural bonds formed between aluminium and an epoxy adhesive. Systematic changes in the micro-roughness of an aluminium Adherend were achieved using an ultra-milling technique to prepare Surfaces with topographies ranging from ultra-flat to a sawtooth profile with a base angle of approximately 60° and a peak-to-valley depth of 10 μm. The fracture toughness of double-cantilever beam specimens, stressed in the Mode 1 direction and exposed to a humid environment was found to change by a factor of approximately one hundred as the sawtooth profile angle was increased. These changes in fracture toughness may be accounted for through complex interrelationships between moisture diffusion and interphase mechanical properties, each with a strong dependence on the Surface micro-topography.
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Influence of Adherend Surface preparation on bond durability
Surface and Interface Analysis, 1999Co-Authors: Andrew N. Rider, C. L. Olsson-jacques, D. R. ArnottAbstract:Work presented in this paper focuses on the critical aspects of the Surface preparation of aluminium employed for the manufacture of aluminium-epoxy joints. The Surface preparation procedure examined is currently employed by the Royal Australian Airforce (RAAF) for repairs requiring metal-to-adhesive bonding. The influence of each step in the Surface preparation on the bond durability performance of the adhesive joint is examined by a combination of methods. Double-cantilever wedge-style adhesive joints are loaded in mode 1 opening and exposed to a humid environment. Together with analysis of the Adherend and joint failure Surfaces, the results show conclusively that adhesive bond durability is sensitive to the presence of contaminant and the roughness of the Adherend Surface. The presence of contaminant can interfere with the effectiveness of an organosilane coupling agent as a durability improver. A two-step bond degradation model was developed to describe qualitatively the observed bond durability performance and fracture data.
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Studies of the degradation of metal-adhesive interfaces with Surface analysis techniques
Applied Surface Science, 1993Co-Authors: D. R. Arnott, Andrew N. Rider, Lambrianidis, A.r. Wilson, Ng FarrAbstract:Abstract The application of bonded repairs and reinforcements to aircraft components places an emphasis on Adherend Surface treatment procedures because these treatments can significantly change bond strength and durability. A typical minimum treatment sequence for Alclad 2024-T3 aluminium alloy Adherends includes a solvent degrease, an abrasion with a Scotchbrite ® pad, a clean with a methyl-ethyl-ketone (MEK) soaked tissue and a grit-blast with 45 μm alumina powder. The Adherends are treated with γ-glycidoxy-propyl-trimethoxy-silane (γ-GPTS) coupling agent then bonded with an epoxy film adhesive. The composition of the adherent, the bond durability and the locus of fracture were examined at several stages of the adherent Surface treatment. Boeing wedge tests show that grit-blasting the Adherends creates a more durable adhesive bond than the Scotchbrite ® /MEK treatment and that the application of γ-GPTS improves bond durability in both cases. XPS has shown that the cleaning sequence decreases the concentration of hydrocarbon contaminant on the grit-blasted Adherend to an average thickness of less than 1.5 nm. XPS analyses of the fracture Surfaces indicates that for the grit-blast, grit-blast plus γ-GPTS and Scotchbrite ® /MEK plus γ-GPTS treatments, failure occurs primarily in the oxide film, whereas for the Scotchbrite ® /MEK treatment failure occurs at the adhesive/oxide interface possibly due to weakness induced by contaminant. XPS measurements show that a γ-GPTS overlayer retards the growth of the oxide on aluminium in humid air, until the γ-GPTS overlayer is desorbed. The improved bond durability with the coupling agent may be due to the inhibition of hydration sites on this oxide Surface.
Satoru Yamamoto - One of the best experts on this subject based on the ideXlab platform.
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Entropy-driven segregation in epoxy-amine systems at a copper interface.
Soft matter, 2021Co-Authors: Satoru Yamamoto, Keiji TanakaAbstract:The composition of an epoxy resin at the interface with the Adherend is usually different from that in the bulk due to the enrichment of a specific constituent, a characteristic called interfacial segregation. For better adhesion, it should be precisely understood how epoxy and amine molecules exist on the Adherend Surface and react with each other to form a three-dimensional network. In this study, the entropic factor of the segregation in a mixture of epoxy and amine at the copper interface before and after the curing reaction is discussed on the basis of a full-atomistic molecular dynamics (MD) simulation. Smaller molecules were preferentially segregated at the interface regardless of the epoxy and amine, and this segregation remained after the curing process. No segregation occurred at the interface for a combination composed of epoxy and amine molecules with a similar size. These findings make it clear that the size disparity between constituents affects the interfacial segregation via the packing and/or translational entropy. The curing reaction was slower near the interface than in the bulk, and a large amount of unreacted molecules remained there. Finally, the effect of molecular shape was also examined. Linear molecules were more likely to segregate than round-shaped ones even though they were similar in volume. We believe that these findings, which are difficult to obtain experimentally, contribute to the understanding of the interfacial adhesion phenomena on a molecular scale.
Andrew N. Rider - One of the best experts on this subject based on the ideXlab platform.
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Influence of Adherend Surface preparation on bond durability
Surface and Interface Analysis, 1999Co-Authors: Andrew N. Rider, C. L. Olsson-jacques, D. R. ArnottAbstract:Work presented in this paper focuses on the critical aspects of the Surface preparation of aluminium employed for the manufacture of aluminium-epoxy joints. The Surface preparation procedure examined is currently employed by the Royal Australian Airforce (RAAF) for repairs requiring metal-to-adhesive bonding. The influence of each step in the Surface preparation on the bond durability performance of the adhesive joint is examined by a combination of methods. Double-cantilever wedge-style adhesive joints are loaded in mode 1 opening and exposed to a humid environment. Together with analysis of the Adherend and joint failure Surfaces, the results show conclusively that adhesive bond durability is sensitive to the presence of contaminant and the roughness of the Adherend Surface. The presence of contaminant can interfere with the effectiveness of an organosilane coupling agent as a durability improver. A two-step bond degradation model was developed to describe qualitatively the observed bond durability performance and fracture data.
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The Influence of Pre-bond MEK Exposure on Bond Durability
1995Co-Authors: Christina Olsson-jacques, Andrew N. Rider, David ArnottAbstract:Epoxy film adhesive FM73 is used in bonded repairs of military aircraft. Methyl ethyl ketone (MEK) is an organic solvent present in FM73 epoxy film adhesive and is used to degrease Adherends. Prior to bonding additional MEK was introduced at various stages in the normal Adherend Surface preparation. Pre-bond contamination with MEK vapour had no effect on bond durability. However bond durability was significantly decreased when the Adherends were wiped with MEK soaked Kimwipes X-ray photoelectron spectroscopy of the failure Surfaces indicated that the MEK solvent deposited a detrimental layer of hydrocarbon at the adhesive/oxide interface. Excess MEK solvent on the Adherend Surface immediately prior to bonding was absorbed by the adhesive and did not significantly reduce bond durability. This MEK introduced bubble-shaped voids in the adhesive during cure. Although voids can create a low impedance path for destructive water vapour to enter the stressed adhesive the Adherends were still protected by a thin film of cured adhesive.
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Studies of the degradation of metal-adhesive interfaces with Surface analysis techniques
Applied Surface Science, 1993Co-Authors: D. R. Arnott, Andrew N. Rider, Lambrianidis, A.r. Wilson, Ng FarrAbstract:Abstract The application of bonded repairs and reinforcements to aircraft components places an emphasis on Adherend Surface treatment procedures because these treatments can significantly change bond strength and durability. A typical minimum treatment sequence for Alclad 2024-T3 aluminium alloy Adherends includes a solvent degrease, an abrasion with a Scotchbrite ® pad, a clean with a methyl-ethyl-ketone (MEK) soaked tissue and a grit-blast with 45 μm alumina powder. The Adherends are treated with γ-glycidoxy-propyl-trimethoxy-silane (γ-GPTS) coupling agent then bonded with an epoxy film adhesive. The composition of the adherent, the bond durability and the locus of fracture were examined at several stages of the adherent Surface treatment. Boeing wedge tests show that grit-blasting the Adherends creates a more durable adhesive bond than the Scotchbrite ® /MEK treatment and that the application of γ-GPTS improves bond durability in both cases. XPS has shown that the cleaning sequence decreases the concentration of hydrocarbon contaminant on the grit-blasted Adherend to an average thickness of less than 1.5 nm. XPS analyses of the fracture Surfaces indicates that for the grit-blast, grit-blast plus γ-GPTS and Scotchbrite ® /MEK plus γ-GPTS treatments, failure occurs primarily in the oxide film, whereas for the Scotchbrite ® /MEK treatment failure occurs at the adhesive/oxide interface possibly due to weakness induced by contaminant. XPS measurements show that a γ-GPTS overlayer retards the growth of the oxide on aluminium in humid air, until the γ-GPTS overlayer is desorbed. The improved bond durability with the coupling agent may be due to the inhibition of hydration sites on this oxide Surface.
Eui Jin Jun - One of the best experts on this subject based on the ideXlab platform.
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Optimal tubular adhesive-bonded lap joint of the carbon fiber epoxy composite shaft
Composite Structures, 1992Co-Authors: Ki Soo Kim, Won-Seock Kim, Dai Gil Lee, Eui Jin JunAbstract:The effects of adhesive thickness and Adherend Surface roughness on the fatigue strength of the tubular adhesive-bonded single lap joint were experimentally investigated using small fatigue test specimens (??21 mm) whose Adherends were made of S45C carbon steel. From the fatigue experiments, it was found that the optimal arithmetic Surface roughness of the Adherends was about 2 ??m and the optimal adhesive thickness was about 0??15 mm. Also, the manufacturing method of the adhesive-bonded tubular single lap joint was discussed for the reliable and optimal joint quality. Using the optimal adhesive thickness and the optimal Adherend roughness, the prototype torsional adhesive joints for the power transmission shafts (??66 mm) of an automotive or a small helicopter were manufactured and statically tested under torque. The tests were performed on the single lap joint, the single lap joint with scarf, the double lap joint, and the double lap joint with scarf. The one part of the Adherend of the joint was made of high strength carbon fiber epoxy composite material and the other part of the Adherend was made of S45C carbon steel. The stresses of joints were analyzed by the finite element method. In applying the finite element method to the composite Adherends, the smeared laminate properties were used. From the experiments, it was found that the double lap joint was the best among the joints in terms of torque capacity as well as manufacturing cost. ?? 1992.
