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1
Cleland, D. J., und L. Basheer. „Pull-off adhesion testing for concrete repairs“. Magazine of Concrete Research 59, Nr. 10 (Dezember 2007): 771–76. http://dx.doi.org/10.1680/macr.2007.59.10.771.
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Dilik, Tuncer, Seda Erdinler, Ender Hazır, Hüseyin Koç und Salim Hiziroglu. „Adhesion Strength of Wood Based Composites Coated with Cellulosic and Polyurethane Paints“. Advances in Materials Science and Engineering 2015 (2015): 1–5. http://dx.doi.org/10.1155/2015/745675.
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The objective of this study was to determine adhesive strength of particleboard and medium density fiberboard (MDF) finished with two types of paints. Samples were coated using cellulosic and polyurethane based paints. Adhesion strength and coating layer thickness of each sample were measured using pull-off testing method and PosiTector equipment, respectively. The highest adhesion strength value of 3.62 MPa was found for MDF samples coated with paint. Based on the statistical analysis type of substrate significantly influenced overall adhesion strength of the samples while type and layer thickness of paint as well as number of layers applied to the surface of specimens have not affected significantly adhesion resistance of the panels used in this work. It appears that pull-off test can effectively be used to determine and evaluate adhesion strength of the samples considered in the experiments.
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Gustke, Kevin, Jana Gebauer, Rico Drehmann, Andrés Fabián Lasagni und Thomas Lampke. „Enhancement of the Adhesion of Wire Arc Sprayed Coatings on Carbon Fiber-Reinforced Plastic by Surface Laser Structuring“. Coatings 11, Nr. 4 (16.04.2021): 467. http://dx.doi.org/10.3390/coatings11040467.
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Due to their outstanding stiffness-to-weight ratio, fiber-reinforced plastics are established materials for weight reduction in the aerospace and automotive industries. To improve certain properties, such as their low thermal and electrical conductivity, metallic coatings can be applied to the polymer surface. One of the methods used for this purpose is thermal spraying. Studies have shown that the adhesion strength of metallic coatings on polymer surfaces is low. To improve the adhesion strength, the surface of the fiber-reinforced plastics was pretreated with pulsed laser-based methods. This study describes in detail the process chain, the resulting surface conditions and their effect on the adhesion strength of wire arc sprayed copper coatings in pull-off and shear tensile testing. The results show up to ~200% increase in adhesion strength for the laser-structured samples compared to the grit-blasted reference samples in the pull-off test.
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Gorumlu, Serdar, und Burak Aksak. „Sticking to rough surfaces using functionally graded bio-inspired microfibres“. Royal Society Open Science 4, Nr. 6 (Juni 2017): 161105. http://dx.doi.org/10.1098/rsos.161105.
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Synthetic fibrillar adhesives inspired by nature, most commonly by the gecko lizard, have been shown to strongly and repeatedly attach to smooth surfaces. These adhesives, mostly of monolithic construction, perform on par with their natural analogues on smooth surfaces but exhibit far inferior adhesive performance on rough surfaces. In this paper, we report on the adhesive performance of functionally graded microfibrillar adhesives based on a microfibre with a divergent end and a thin soft distal layer on rough surfaces. Monolithic and functionally graded fibre arrays were fabricated from polyurethanes and their adhesive performance on surfaces of varying roughness were quantified from force–distance data obtained using a custom adhesion measurement system. Average pull-off stress declined significantly with increasing roughness for the monolithic fibre array, dropping from 77 kPa on the smoothest (54 nm RMS roughness) to 19 kPa on the roughest (408 nm RMS roughness) testing surface. In comparison, pull-off stresses of 81 kPa and 63 kPa were obtained on the same respective smooth and rough surfaces with a functionally graded fibre array, which represents a more than threefold increase in adhesion to the roughest adhering surface. These results show that functionally graded fibrillar adhesives perform similar on all the testing surfaces unlike monolithic arrays and show potential as repeatable and reusable rough surface adhesives.
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Szymanowski, Jacek, und Łukasz Sadowski. „Adhesion Assessment between Concrete Layers Using the Ultrasonic Pulse Velocity Method“. Applied Mechanics and Materials 797 (November 2015): 145–50. http://dx.doi.org/10.4028/www.scientific.net/amm.797.145.
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Adhesion assessment between concrete layers with the use of the non-destructive ultrasonic pulse velocity (UPV) method has been described in the article. Two-layer concrete elements, obtained by drilling the core from a large size multilayer element, were the object of testing. The ultrasonic wave velocity of the element and the materials of which its layers were made were assigned for each element. On that basis, the comparative velocity i.e. the velocity at which an ultrasonic wave going through the boundary surface of layers wouldn’t cause any change in the velocity, was determined. The ratio of the two velocities has been compared to adhesion values obtained through the semi-destructive pull-off method. It was revealed that when the ratio of the ultrasonic wave velocity of the element to comparative velocity increases, the pull-off adhesion value also increases.
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Kolegar, Tomas, Martin Matousek, Monika Vilemova und Vladimir Stary. „ADHESION OF BIOCOMPATIBLE TiNb COATING“. Acta Polytechnica CTU Proceedings 8 (30.06.2017): 5–7. http://dx.doi.org/10.14311/app.2017.8.0005.
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Preparation of a coating with a high quality requires good adhesion of the film to the substrate. The paper deals with the adhesion of biocompatible TiNb coating with different base materials. Several materials such as titanium CP grade 2, titanium alloys Ti6Al4V and stainless steel AISI 316L were measured. Testing samples were made in the shape of small discs. Those samples were coated with a TiNb layer by using the PVD method (magnetron sputtering). Onto the measured layer of TiNb an assistant cylinder was stuck using a high strength epoxy adhesive E1100S. The sample with the assistant cylinder was fixed into a special fixture and the whole assembly underwent pull-off testing for adhesion. The main result of this experiment was determining the strength needed to peel the layer and morphology and size of the breakaway. As a result, we will be able to determine the best base material and conditions where the coating will be remain intact with the base material.
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Ullah, Sana, Ronald Weilguny, Sorschag Kurt und Gunter Zieger. „Optimizing Combination of Parameters for Pull-off Adhesion Testing through Design of Experiment Study“. Journal of Nano- and Electronic Physics 10, Nr. 4 (2018): 04007–1. http://dx.doi.org/10.21272/jnep.10(4).04007.
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Heepe, Lars, Alexander E. Kovalev und Stanislav N. Gorb. „Direct observation of microcavitation in underwater adhesion of mushroom-shaped adhesive microstructure“. Beilstein Journal of Nanotechnology 5 (25.06.2014): 903–9. http://dx.doi.org/10.3762/bjnano.5.103.
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In this work we report on experiments aimed at testing the cavitation hypothesis [Varenberg, M.; Gorb, S. J. R. Soc., Interface 2008, 5, 383–385] proposed to explain the strong underwater adhesion of mushroom-shaped adhesive microstructures (MSAMSs). For this purpose, we measured the pull-off forces of individual MSAMSs by detaching them from a glass substrate under different wetting conditions and simultaneously video recording the detachment behavior at very high temporal resolution (54,000–100,000 fps). Although microcavitation was observed during the detachment of individual MSAMSs, which was a consequence of water inclusions present at the glass–MSAMS contact interface subjected to negative pressure (tension), the pull-off forces were consistently lower, around 50%, of those measured under ambient conditions. This result supports the assumption that the recently observed strong underwater adhesion of MSAMS is due to an air layer between individual MSAMSs [Kizilkan, E.; Heepe, L.; Gorb, S. N. Underwater adhesion of mushroom-shaped adhesive microstructure: An air-entrapment effect. In Biological and biomimetic adhesives: Challenges and opportunities; Santos, R.; Aldred, N.; Gorb, S. N.; Flammang, P., Eds.; The Royal Society of Chemistry: Cambridge, U.K., 2013; pp 65–71] rather than by cavitation. These results obtained due to the high-speed visualisation of the contact behavior at nanoscale-confined interfaces allow for a microscopic understanding of the underwater adhesion of MSAMSs and may aid in further development of artificial adhesive microstructures for applications in predominantly liquid environments.
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Goth, Christian, Thomas Kuhn, Gerald Gion und Jörg Franke. „Hot Pin Pull Method – New Test Procedure for the Adhesion Measurement for 3D-MID“. Advanced Materials Research 1038 (September 2014): 115–20. http://dx.doi.org/10.4028/www.scientific.net/amr.1038.115.
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The adhesion test of metallic structures on MID (Molded Interconnect Devices) parts is an unsolved issue. So far no method really works reliably. The test methods which are conventionally used are the pull-off test and the shear-test. Both show large standard deviation and the reproducibility is not assured. Nordson DAGE has introduced the new micro-material testing system 4000Plus. This device enables a new test method for the determination of the adhesion strength of MID structures using the hot pin pull (hot bump pull) method. Copper pins (tinned or untinned) are heated up with a user defined temperature profile, soldered to a metallized structure on the MID and then removed vertically upward, while the force is recorded. In this contribution investigations with this new test method are presented.
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Lachance-Tremblay, Éric, Michel Vaillancourt, Daniel Perraton und Hervé Di Benedetto. „Comparison of the moisture damage of bituminous binder coupled with glass and limestone substrate using pull-off test“. Canadian Journal of Civil Engineering 46, Nr. 3 (März 2019): 188–94. http://dx.doi.org/10.1139/cjce-2018-0152.
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In this paper, the moisture susceptibility of different bituminous binders with two substrates (glass and limestone) was investigated. To that end, the tensile strength of different combinations of bituminous binder–substrate bond was measured using a pull-off test. This test was adapted from the pneumatic adhesion tensile testing instrument (PATTI) test to improve repeatability. Samples were tested in dry condition and after a 7-day conditioning in hot water bath (60 °C). An analysis of variance (ANOVA) was performed on the test results. Overall, the results show that in dry condition, the pull-off strength is a function of the bituminous binder type rather than of the substrate type. After water conditioning, an increase in the pull-off strength was observed for the bituminous binder without polymers and coupled with glass substrate. This was associated with an increase in binder stiffness. For the limestone substrate, the effect of water conditioning was significant only for one type of binder.
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Ozdemir, Turgay, Salim Hiziroglu und Mutlu Kocapınar. „Effect of Heartwood and Sapwood Ratio on Adhesion Strength of Finished Wood Species“. Advances in Materials Science and Engineering 2015 (2015): 1–5. http://dx.doi.org/10.1155/2015/418618.
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The objective of this study was to determine adhesion strength of samples from wood species coated with cellulose varnish as function of heartwood and sapwood ratio. Roughness of the specimens from four different species was measured employing stylus type equipment before they were coated with varnish. Pull-off testing unit was employed to determine adhesion strength of the samples. Based on the findings in this work it seems that no significant difference was determined between adhesion strength values of the samples prepared from heartwood and sapwood portions. The highest adhesion strength value of 2.62 N/mm2was found for the beech samples sanded with 80-grit sand paper. Overall rougher surfaces of the samples resulted in higher adhesion strength between finish and substrate.
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Bajat, Jelena, Vesna Miskovic-Stankovic und Dragutin Drazic. „Adhesion of epoxy cataphoretic coatings on Zn alloys“. Journal of the Serbian Chemical Society 72, Nr. 12 (2007): 1383–92. http://dx.doi.org/10.2298/jsc0712383b.
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One of the most important factors in corrosion prevention by protective coatings is the loss of coating adhesion under environmental influence. In this work, the adhesion of epoxy cataphoretic coatings was examined on steel and steel modified by Zn-Fe and Zn-Co alloys. The dry and wet adhesions of epoxy primers were measured by the direct pull-off standardized procedure, as well as indirectly by the NMP test. The corrosion stability of the coated samples was investigated by electrochemical impedance spectroscopy. It was shown that under dry testing conditions all the samples exhibited very good adhesion. However, different trends of adhesion loss of different protective systems during exposure to a corrosive agent (3 % NaCl solution) were observed. The lowest adhesion values were obtained for epoxy coating on the steel substrate. The change in adhesion of the epoxy coating on steel modified by Zn-Co alloy during immersion in 3 % NaCl solution for 24 days was the smallest of all the investigated samples. Electrochemical impedance measurements in 3 % NaCl solution confirmed the good protective properties of this protective system, i.e., greater values of pore resistance were obtained.
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Geambazu, Laura Elena, Cosmin Mihai Cotruţ, Florin Miculescu und Ioana Csaki. „Mechanically Alloyed CoCrFeNiMo0.85 High-Entropy Alloy for Corrosion Resistance Coatings“. Materials 14, Nr. 14 (07.07.2021): 3802. http://dx.doi.org/10.3390/ma14143802.
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High-entropy alloys could provide a solution for corrosion resistance due to their impressive properties. Solid-state processing of high purity Co, Cr, Fe, Ni and Mo metallic powders and consolidation resulted in a bulk material that was further machined into electro spark deposition electrodes. After the stainless steel substrate surface preparation, thin successive layers of the high-entropy alloy were deposited and Pull-Off testing was performed on the newly obtained coating, for a better understanding of the adhesion efficiency of this technique. Good adhesion of the coating to the substrate was proved by the test and no cracks or exfoliations were present. Corrosion resistance testing was performed in a liquid solution of 3.5 wt.% NaCl for 6 h at room temperature and the results obtained validated our hypothesis that CoCrFeNiMo0.85 high-entropy alloys could provide corrosion resistance when coating a stainless steel substrate.
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Duda, Monika, Joanna Pach und Grzegorz Lesiuk. „Influence of Polyurea Composite Coating on Selected Mechanical Properties of AISI 304 Steel“. Materials 12, Nr. 19 (26.09.2019): 3137. http://dx.doi.org/10.3390/ma12193137.
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This paper contains experimental results of mechanical testing of the AISI 304 steel with composite coatings. The main goal was to investigate the impact of the applied polyurea composite coating on selected mechanical properties: Adhesion, impact resistance, static behavior, and, finally, fatigue lifetime of notched specimens. In the paper the following configurations of coatings were tested: EP (epoxy resin), EP_GF (epoxy resin + glass fabric), EP_GF_HF (epoxy resin + glass fabric hemp fiber), EP_PUA (epoxy resin + polyurea) resin, EP_GF_PUA (epoxy resin + glass fabric + polyurea) resin, and EP_GF_HF_PUA (epoxy resin + glass fabric + hemp fiber + polyurea) resin. The highest value of force required to break adhesive bonds was observed for the EP_PUA coating, the smallest for the single EP coating. A tendency of polyurea to increase the adhesion of the coating to the base was noticed. The largest area of delamination during the impact test was observed for the EP_GF_HF coating and the smallest for the EP-coated sample. In all tested samples, observed delamination damage during the pull-off test was located between the coating and the metallic base of the sample.
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Shifa, Madni, Fawad Tariq und Rasheed Ahmed Baloch. „Influence of Carbon Nanotubes on the Interlaminar Properties of Carbon Fiber Aluminum Metal Laminates“. Key Engineering Materials 778 (September 2018): 100–110. http://dx.doi.org/10.4028/www.scientific.net/kem.778.100.
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The present research work describes the fabrication and interlaminar properties testing of carbon fiber aluminum metal laminates (CARALL). CARALL was fabricated through hand layup process followed by compression molding technique and interlaminar properties were assessed through double cantilever beam (DCB) test short beam and flexural test. Different treatments were performed on the surface of aluminum alloy and parameters were optimized to ensure good adhesion between metal sheet and carbon composite layer. Pull-off adhesion test was performed to gauge the adhesion strength of epoxy resin on aluminum alloy sheet. Effect of Multi-wall carbon nanotubes (MWCNTs) was also investigated on the interlaminar properties of CARALL. Treated surface of aluminum alloy sheet was examined under Optical and Field Emission Scanning Electron Microscopy (FE-SEM). Porous surface was evident on aluminum sample due to surface treatment which contributes towards better adhesion between epoxy resin and metal surface through mechanical interlocking and diffusion mechanism. FE-SEM and stereo microscopy was also performed on fractured DCB samples and underlying fracture mechanism was discussed. Test results demonstrated that addition of MWCNTs deteriorated the interlaminar properties of CARALL by weakening the interface between treated aluminum surface and carbon composite.
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Ghozali, Muhammad, Agus Haryono, Asep Handaya Saputra und Evi Triwulandari. „PENGARUH 1,4-BUTANDIOL SEBAGAI POLIOL PADA MODIFIKASI EPOKSI MENGGUNAKAN POLIURETAN“. Jurnal Kimia Terapan Indonesia 17, Nr. 1 (10.06.2015): 1–7. http://dx.doi.org/10.14203/jkti.v17i1.17.
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Corrosion is a natural phenomenon causing degradation value and function of material. The use of paints and polymer coatings is the most popular method to protect material against corrosion. Polymer coatings used was an epoxy-based organic resin and polyurethane. Generally, those coating materials were used separately. This study carried out the modification of epoxy with polyurethane in order to obtain coating materials as a combination of epoxy and polyurethane. Expectedly, the chemical reaction between epoxy coating-material and polyurethane could improve the characteristics of the obtained coating materials. Synthesis of polyurethane-modified epoxy with 1,4-butanediol as the polyol (ETP-BTD) was conducted by reacting epoxy resin, tolonate and 1,4-butanediol simultaneously at 50 oC for 30 min with dibutyltindilaurate as catalyst. Functional group analysis of ETP-BTD was performed by Fourier Transform Infra Red (FTIR), tensile strength by Ultimate Testing Machine (UTM), adhesion by ASTM D4541 Portable Pull-off Adhesion Testers, water vapor transmission rate by ASTM E96 Desiccant Method and thermal stability was studied using Thermogravimetric Analysis (TGA). The FTIR analysis results showed that there are urethane bonds at 1716-1690 cm-1. These results showed that modification of epoxy using polyurethane increased the tensile strength and adhesion, and also decreased the water vapor transmission rate of epoxy. Keywords: epoxy, modification, polyol, polyurethane, 1.4-butanediol
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Mohamad Ibrahim, M. N., M. E. Izat, A. R. Wahida und C. S. Sipaut. „STUDY ON MOISTURE-CUR ED POLYURETHANE AS UNDERCOATING LAYER FOR METALLIZATION“. ASEAN Journal on Science and Technology for Development 22, Nr. 3 (11.11.2017): 271. http://dx.doi.org/10.29037/ajstd.165.
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In this work a technique of metallizing substrate via electroless plating using moisture-cured polyurethane (MCPU) system as the undercoat is presented. MCPU prepolymer was prepared by mixing polyethylene glycol divinyl ether and diphenylmethane-4, 4’-diisocyanate in 1:1 ratio. The effects of etching time as well as curing period on the surface characteristic of MCPU undercoating were investigated. Contact angle measurements, FTIR and SEM were employed to study the changes on the surface of the treated MCPU undercoatsprior to electroless nickel plating. Electroless plating was performed using nickel bath and visual inspection was performed after completing the electroless plating cycles. Relative increase in wettability of the treated MCPU was observed. The surface became hydrophilic after subjecting to mild etching for 1 minute. SEM analysis revealed different pitted structures on the treated MCPU that were cured at different periods. FTIR analysis of the treated MCPU showed some chemical changes marked by the presence of free hydroxyl group and decrease of CH (methylene), urethane C=O, urethane amide and ether peaks. FTIR also showed the sign of further NCO reaction, which indicates by the decrease of NCO peak and increase of NH and urea C=O peaks. The standard pull-off testing method (ASTM D 4541) was employed to evaluate the adhesion strength of nickel deposits coated on MCPU undercoating layer.The test results revealed that curing period and etching time influence the adhesion performance.The results also show that at a selected curing period, prolong etching time will decrease the adhesion strength. Meanwhile prolong curing period will improve the adhesion strength.
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Zhang, Qiuhong, Betty T. Quinton, Bang-Hung Tsao, James Scofield, Neil Merrett, Jacob Lawson, Kevin Yost und Levi Elston. „Growth and Characterization of Uniform Carbon Nanotube Arrays on Active Substrates“. MRS Proceedings 1752 (2015): 3–14. http://dx.doi.org/10.1557/opl.2015.291.
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ABSTRACTCarbon nanotubes (CNTs) have unique thermal/electrical/mechanical properties and high aspect ratios. Growth of CNTs directly onto reactive material substrates (such as metals and carbon based foam structures, etc.) to create a micro-carbon composite layer on the surface has many advantages: possible elimination of processing steps and resistive junctions, provision of a thermally conductive transition layer between materials of varying thermal expansion coefficients, etc. Compared to growing CNTs on conventional inert substrates such as SiO2, direct growth of CNTs onto reactive substrates is significantly more challenging. Namely, control of CNT growth, structure, and morphology has proven difficult due to the diffusion of metallic catalysts into the substrate during CNT synthesis conditions. In this study, using a chemical vapor deposition method, uniform CNT layers were successfully grown on copper foil and carbon foam substrates that were pre-coated with an appropriate buffer layer such as Al2O3 or Al. SEM images indicated that growth conditions and, most notably, substrate surface pre-treatment all influence CNT growth and layer structure/morphology. The SEM images and pull-off testing results revealed that relatively strong bonding existed between the CNT layer and substrate material, and that normal interfacial adhesion (0.2‒0.5 MPa) was affected by the buffer layer thickness. Additionally, the thermal properties of the CNT/substrate structure were evaluated using a laser flash technique, which showed that the CNT layer can reduce thermal resistance when used as a thermal interface material between bonded layers.
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Liu, Kang. „Experimental Study on Bond Characterization of Hybrid-Bonded FRP to Concrete Interfaces“. Advanced Materials Research 790 (September 2013): 375–80. http://dx.doi.org/10.4028/www.scientific.net/amr.790.375.
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Pure adhesive bond of FRP to concrete is not only weak but also unreliable in a long term. This problem can be effectively overcome by a newly developed bond enhancement system the hybrid bonded FRP system (HB-FRP) in which small mechanical fasteners are used to augment the bond. In this paper, the bond behaviors of EB-FRP and HB-FRP joints were experimentally investigated by employing the single shear pull-off test on three EB-FRP and seven HB-FRP specimens with different bond lengths. Experimental testing is reported for characterization of the interfacial bond of the HB-FRP system.
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Salakhova, R. K., A. B. Tikhoobrazov, T. B. Smirnova und S. G. Kirilin. „Nickel plating of carbon and fiberglass with the purpose of increasing the erosion resistance of PCM structures“. Strengthening Technologies and Coatings, 2021, 221–27. http://dx.doi.org/10.36652/1813-1336-2021-17-5-221-227.
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A method is proposed for increasing the erosion resistance of carbon and fiberglass by electrolytic deposition of a wear-resistant nickel coating on polymer composite materials. An assessment of the relative erosion resistance was carried out and the rate of erosional destruction of nickel-plated polymer composite materials was calculated when testing materials on the EI-01 laboratory installation for erosional wear developed by the authors. The effect of plasma treatment (atmospheric pressure plasma) of the surface of carbon and fiberglass on the adhesion strength of the nickel coating to the base, which was determined by the pull-off method using an Elcometer 106 adhesion meter, was studied.
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Zhou, Bo, Nicholas Randall und Barton Prorok. „Correlation between Adhesion Strength and Thin film/Substrate Mechanical Properties using the Nano-Scratch Technique“. MRS Proceedings 1297 (2011). http://dx.doi.org/10.1557/opl.2011.651.
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ABSTRACTScratch testing, as a mature technique for coating adhesion quantification, has been widely adopted by both industrial and academic fields in recent years. Following the urgent needs of very small materials characterization, nano-scratch testing has gradually replaced the traditional pull-off test for the study of ultra-thin film properties. In this research, the relationship between the adhesion strength and film/substrate mechanical properties was investigated to provide fundamental but crucial knowledge of the scratch mechanism. Scratch tests were performed on different film/substrate combinations using a Nano Scratch Tester with a sphero-conical diamond indenter. A progressive load mode was employed to cause coating failure during scratch on the film surface. The critical values of different failure mechanisms, such as cracking and delamination were accurately determined according to the scratch panorama image, penetration and residual depth data. In addition, the hardness (H) and modulus (E) values of the thin films and substrates were measured with an Ultra Nanoindentation Tester. The scratch critical failure loads were then plotted versus film/substrate H and E ratios. A unique relationship was found between these parameters that could help understand the true mechanism behind scratch adhesion and leverage this methodology to a new theoretical level.
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Thimons, L. A., A. Gujrati, A. Sanner, L. Pastewka und T. D. B. Jacobs. „Hard-material Adhesion: Which Scales of Roughness Matter?“ Experimental Mechanics, 01.07.2021. http://dx.doi.org/10.1007/s11340-021-00733-6.
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Abstract Background Surface topography strongly modifies adhesion of hard-material contacts, yet roughness of real surfaces typically exists over many length scales, and it is not clear which of these scales has the strongest effect. Objective: This investigation aims to determine which scales of topography have the strongest effect on macroscopic adhesion. Methods Adhesion measurements were performed on technology-relevant diamond coatings of varying roughness using spherical ruby probes that are large enough (0.5-mm-diameter) to sample all length scales of topography. For each material, more than 2000 measurements of pull-off force were performed in order to investigate the magnitude and statistical distribution of adhesion. Using sphere-contact models, the roughness-dependent effective values of work of adhesion were measured, ranging from 0.08 to 7.15 mJ/m2 across the four surfaces. The data was more accurately fit using numerical analysis, where an interaction potential was integrated over the AFM-measured topography of all contacting surfaces. Results These calculations revealed that consideration of nanometer-scale plasticity in the materials was crucial for a good quantitative fit of the measurements, and the presence of such plasticity was confirmed with AFM measurements of the probe after testing. This analysis enabled the extraction of geometry-independent material parameters; the intrinsic work of adhesion between ruby and diamond was determined to be 46.3 mJ/m2. The range of adhesion was 5.6 nm, which is longer than is typically assumed for atomic interactions, but is in agreement with other recent investigations. Finally, the numerical analysis was repeated for the same surfaces but this time with different length-scales of roughness included or filtered out. Conclusions The results demonstrate a critical band of length-scales—between 43 nm and 1.8 µm in lateral size—that has the strongest effect on the total adhesive force for these hard, rough contacts.
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Palecek, A. M., H. L. Schoenfuss und R. W. Blob. „Sticking to it: testing passive pull-off forces in waterfall-climbing fishes across challenging substrates“. Journal of Experimental Biology, 16.12.2020, jeb.228718. http://dx.doi.org/10.1242/jeb.228718.
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The pelvic sucker of Hawaiian waterfall climbing gobies allows these fishes to attach to substrates while climbing waterfalls 10s-100s of meters tall. Climbing ability varies by species and may be further modulated by the physical characteristics of the waterfall substrate. In this study, we investigated the influence of surface wettability (hydrophobic vs. hydrophilic surface charges) and substrate roughness on the passive adhesive system of four species of gobies with different climbing abilities. Overall, passive adhesive performance varied by species and substrate with the strongest climbers showing the highest shear pull-off forces, particularly on rough surfaces. Thus, differences in passive adhesive performance may help to explain the ability of some species to migrate further upstream than others and contribute to their ability to invade new habitats.
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Dähne, Felix, Heike Meißner, Klaus Böning, Christin Arnold, Ralf Gutwald und Elisabeth Prause. „Retention of different temporary cements tested on zirconia crowns and titanium abutments in vitro“. International Journal of Implant Dentistry 7, Nr. 1 (20.07.2021). http://dx.doi.org/10.1186/s40729-021-00349-4.
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Abstract Purpose The aim of the present study was to examine the retention force of monolithic zirconia copings cemented with various temporary cements on implant abutments in vitro. Methods Sixty exercise implants with pre-screwed implant abutments were embedded in resin. Subsequently, 60 CAD/CAM manufactured zirconia copings were divided into three main groups [Harvard Implant Semi-permanent (HAV), implantlink semi Forte (IMP), Temp Bond NE (TBNE)]. The zirconia copings were cemented on the implant abutments and loaded with 35 N. Specimens were stored in distilled water (37 °C) for 24 h. Half of the test specimens of each group were subjected to a thermocycling (TC) process. Retention force was measured in a universal testing machine. Using magnifying glasses, the fracture mode was determined. Statistical analysis was performed applying the Kruskal-Wallis test, the post hoc test according to Dunn-Bonferroni and a chi-square test of independence. Results Without TC, IMP showed the highest retention of the three temporary luting agents (100.5 ± 39.14 N). The measured retention forces of IMP were higher than those of HAV (45.78 ± 15.66 N) and TBNE (61.16 ± 20.19 N). After TC, retention was reduced. IMP showed the greatest retentive strength (21.69 ± 13.61 N, three fail outs). HAV and TBNE showed pull-off forces of similar magnitude (17.38 ± 12.77 N and 16.97 ± 12.36 N, two fail outs). The fracture mode analysis showed different results regarding the tested cements before and after TC (facture type before/after TC): IMP (III+II/III), HAV (I/II) and TBNE (III/III). There were clear differences of the fracture modes regarding the examination before and after TC. Conclusions Within the limits of this study, IMP showed the highest pull-off forces under the chosen test conditions. All three temporary luting agents showed lower retention forces after TC. Retention values in the individual cement classes were very heterogeneous. Easy cement removal in the crown lumen favours the dominance of adhesive cement fractures on the abutment and adhesive/cohesive cement fractures on the abutment with HAV appears advantageous in case of recementation of the superstructure.