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V F Karachalios - One of the best experts on this subject based on the ideXlab platform.
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cure shrinkage in epoxy Adhesives
European adhesion conference, 1997Co-Authors: R D Adams, V F KarachaliosAbstract:The build-up of shrinkage over time during curing and on cooling of an epoxy Adhesive has been investigated. A new device, designed and built in-house, was used to measure the shrinkage of the epoxy during cure at room and elevated temperatures. In this investigation, the cure of two epoxy resin systems which consists of one Part Adhesive ESP110 and a two-Part Adhesive has been successfully monitored using this device and through the way of measurement of shrinkage change with time. By careful monitoring of the shrinkage, we have shown that the cure contraction at room temperature is of the order of 3.75% by volume and 1.16% expansion, 3.3% contraction at 60 °C for the two-Part Adhesive. It is also shown how the overall volume change caused by expansion and shrinkage is distributed during the cure process. Finally, using a plot of the variation of the shear modulus of the epoxy with time during cure, presented in a previous paper, approximate formulae for estimating the residual stress caused by shrinkage is given.
Marios K. Chryssanthopoulos - One of the best experts on this subject based on the ideXlab platform.
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selection of carbon fiber reinforced polymer systems for steelwork upgrading
Journal of Materials in Civil Engineering, 2006Co-Authors: Nikolaos K Photiou, L C Hollaway, Marios K. ChryssanthopoulosAbstract:This paper examines the effectiveness of a high and an ultrahigh modulus carbon-fiber-reinforced polymer (CFRP) composite prepreg, both of which have been specifically developed for the civil engineering industry. A film Adhesive, compatible with the matrix material of the CFRP composite, has been introduced. The bonding characteristics of this film Adhesive have been compared with those of a standard two-Part Adhesive - widely used in the construction industry - with those of a two-Part Adhesive - frequently used for high-grade bonding applications in the aerospace industry. The results have shown that when bonding carbon fiber composites to steel, the film Adhesive has more favorable characteristics compared to those of the standard civil engineering Adhesive, though the high-grade, and higher-cost, aerospace Adhesive has superior bonding qualities. It has also been demonstrated that a good understanding of the full load-deformation response of relevant joints, including load-strain and load-extension characteristics, as well as failure mode characterization, is essential. © 2006 ASCE.
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strengthening of an artificially degraded steel beam utilising a carbon glass composite system
Advanced Polymer Composites for Structural Applications in Construction#R##N#Acic 2004, 2004Co-Authors: Nikolaos K Photiou, L C Hollaway, Marios K. ChryssanthopoulosAbstract:The repair and strengthening of deteriorated, damaged and sub-standard steel bridges has become one of the important challenges confronting civil engineers worldwide. To rehabilitate these structures, techniques utilising the lightweight, high strength and corrosion resistance of fibre reinforced polymer (FRP) composites have been proposed. The flexural load carrying capacity of a steel girder can be reinforced significantly by using a two Part Adhesive or a film Adhesive to bond carbon fibre polymer (CFRP) composites its tension flange. This paper discusses the experimental results to investigate the effectiveness of an ultra-high CFRP prepreg in strengthening an artificially degraded beam of rectangular cross-section under four-point loading. Two beams were upgraded, one utilising a U-shaped prepreg unit and the other a flat plate prepreg; both utilised an identical hybrid lay-up of CFRP and glass fibre polymer (GFRP) composite and an Adhesive film to bond it to the steel substrate. In the first upgraded beam, the U-shaped hybrid composite was extended up the vertical sides of the beam, to the neutral axis height. Both beams failed when the ultimate strain of the carbon fibre was reached in the pure moment region; the failure load was equal to the full plastic collapse load of the undamaged beam, thus demonstrating the effectiveness of the proposed upgrading scheme. On re-loading the beams after failure, the U-shaped hybrid upgrade continued to act compositely with the steel beam outside of a well confined region corresponding to the original failure location, whereas the beam with the flat plate upgrade exhibited the typical response of a steel beam, owing to debonding having taken place over practically the entire beam length.
Solbes Ferri Irene - One of the best experts on this subject based on the ideXlab platform.
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Estudio numérico y experimental de fabricación y fractura en materiales híbridos de titanio-material compuesto reforzados con fibra de carbono
2019Co-Authors: Solbes Ferri IreneAbstract:[EN] In the present bachelor’s research two hybrid titanium-unidirectional carbon fiber reinforced polymer specimens have been produced. The design characteristics have been conditioned so as to obtain unbalanced specimens with Adhesive between all hybrid interfaces, therefore the joining method is the so called co-bonding. The dimensions are stated by standards of Double Cantilever Beam (DCB) test, for which the specimens are created. This test allows to find the fracture related properties in mode I, obtaining a consistent characterisation of the hybrid interface. One of the main issues in hybrid Parts is the thermal residual strains and stresses building-up during manufacturing, consequence mainly, of the mismatch between the coefficient of thermal expansion of metallic and composite fractions. In order to evaluate such stresses-strains an optical sensing network has been embedded inside the composite block of the specimens. A total of 5 fiber bragg grating (FBG) sensors in each specimen are used to monitor the temperature and strain evolution inside the laminate during curing cycle of the composite Part (Adhesive is cured in the same cycle). Strains trend show low, quasi-constant values for the most Part of the curing cycle until the cooling phase when strains start to increase notably. This is due to the viscous state of the resin and Adhesive at high temperatures, that avoids the load transfer at interfaces until the polymeric fraction is completely solid when it is cooled. Numerical models simulating the cool-down phase have shown that the stress free temperature of the co-bonded laminate is around 120oC, this is obtained through a comparison with the experimental plots. With this temperature, more accurate results for the residual stresses have been obtained as well as a preliminary evaluation of the final bending displacement of the unbalanced arm.[ES] En el presente proyecto de fin de grado se han fabricado dos especímenes híbridos de titanio y polímero reforzado con fibra de carbono unidireccional. Las características del diseño han sido condicionadas para obtener especímenes desbalanceados, es decir con deformaciones térmicas después del ciclo de curado, con una lámina de adhesivo entre cada una de las interfases híbridas del laminado, usando así el método determinado como co-bonding para uniones en compuestos. Las dimensiones estén determinadas por la normativa estándar del test (Double Cantilever Beam) para el cual han sido producidos los especímenes. Dicho test permite obtener las propiedades relacionadas con el modo I de fractura, consiguiendo así la caracterización de la interfase híbrida. Uno de los mayores problemas en elementos híbridos son las cargas y deformaciones térmicas residuales que se crean durante la fabricación, debidas en su mayoría a la diferencia entre los coeficientes de expansión térmica de la Parte metálica y el compuesto. Con la finalidad de evaluar dichas cargas y deformaciones, una red sensitiva de fibra óptica ha sido insertada dentro del bloque de compuesto de los especímenes. Un total de 5 sensores FBG en cada espécimen son usados para monitorizar la evolución de temperatura y deformaciones durante el ciclo de curado del compuesto. La tendencia de las deformaciones durante la mayoría del ciclo es constante, con valores muy pequeños, hasta el inicio de la fase de enfriado cuando las deformaciones (en este caso compresivas) aumentan notablemente. Este efecto es debido al estado viscoso de la resina y el adherente a altas temperaturas, lo cual reduce la capacidad de transmisión de cargas en las interfase híbridas hasta que la fracción polimérica está completamente sólida. Las simulaciones en modelos MEF de la fase de enfriamiento muestran que la temperatura bajo la cual empiezan a crecer considerablemente las deformaciones y por tanto las cargas térmicas, está sobre 120oC, esta temperatura se ha obtenido mediante comparaciones con las gráficas experimentales. Con esta temperatura, los resultados obtenidos en MEF para las cargas térmicas son más precisos, así como la evaluación preliminar del desplazamiento vertical debido a la curvatura de uno de los brazos del espécimen.Solbes Ferri, I. (2019). Estudio numérico y experimental de fabricación y fractura en materiales híbridos de titanio-material compuesto reforzados con fibra de carbono. http://hdl.handle.net/10251/126342TFG
R D Adams - One of the best experts on this subject based on the ideXlab platform.
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cure shrinkage in epoxy Adhesives
European adhesion conference, 1997Co-Authors: R D Adams, V F KarachaliosAbstract:The build-up of shrinkage over time during curing and on cooling of an epoxy Adhesive has been investigated. A new device, designed and built in-house, was used to measure the shrinkage of the epoxy during cure at room and elevated temperatures. In this investigation, the cure of two epoxy resin systems which consists of one Part Adhesive ESP110 and a two-Part Adhesive has been successfully monitored using this device and through the way of measurement of shrinkage change with time. By careful monitoring of the shrinkage, we have shown that the cure contraction at room temperature is of the order of 3.75% by volume and 1.16% expansion, 3.3% contraction at 60 °C for the two-Part Adhesive. It is also shown how the overall volume change caused by expansion and shrinkage is distributed during the cure process. Finally, using a plot of the variation of the shear modulus of the epoxy with time during cure, presented in a previous paper, approximate formulae for estimating the residual stress caused by shrinkage is given.
Nikolaos K Photiou - One of the best experts on this subject based on the ideXlab platform.
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selection of carbon fiber reinforced polymer systems for steelwork upgrading
Journal of Materials in Civil Engineering, 2006Co-Authors: Nikolaos K Photiou, L C Hollaway, Marios K. ChryssanthopoulosAbstract:This paper examines the effectiveness of a high and an ultrahigh modulus carbon-fiber-reinforced polymer (CFRP) composite prepreg, both of which have been specifically developed for the civil engineering industry. A film Adhesive, compatible with the matrix material of the CFRP composite, has been introduced. The bonding characteristics of this film Adhesive have been compared with those of a standard two-Part Adhesive - widely used in the construction industry - with those of a two-Part Adhesive - frequently used for high-grade bonding applications in the aerospace industry. The results have shown that when bonding carbon fiber composites to steel, the film Adhesive has more favorable characteristics compared to those of the standard civil engineering Adhesive, though the high-grade, and higher-cost, aerospace Adhesive has superior bonding qualities. It has also been demonstrated that a good understanding of the full load-deformation response of relevant joints, including load-strain and load-extension characteristics, as well as failure mode characterization, is essential. © 2006 ASCE.
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strengthening of an artificially degraded steel beam utilising a carbon glass composite system
Advanced Polymer Composites for Structural Applications in Construction#R##N#Acic 2004, 2004Co-Authors: Nikolaos K Photiou, L C Hollaway, Marios K. ChryssanthopoulosAbstract:The repair and strengthening of deteriorated, damaged and sub-standard steel bridges has become one of the important challenges confronting civil engineers worldwide. To rehabilitate these structures, techniques utilising the lightweight, high strength and corrosion resistance of fibre reinforced polymer (FRP) composites have been proposed. The flexural load carrying capacity of a steel girder can be reinforced significantly by using a two Part Adhesive or a film Adhesive to bond carbon fibre polymer (CFRP) composites its tension flange. This paper discusses the experimental results to investigate the effectiveness of an ultra-high CFRP prepreg in strengthening an artificially degraded beam of rectangular cross-section under four-point loading. Two beams were upgraded, one utilising a U-shaped prepreg unit and the other a flat plate prepreg; both utilised an identical hybrid lay-up of CFRP and glass fibre polymer (GFRP) composite and an Adhesive film to bond it to the steel substrate. In the first upgraded beam, the U-shaped hybrid composite was extended up the vertical sides of the beam, to the neutral axis height. Both beams failed when the ultimate strain of the carbon fibre was reached in the pure moment region; the failure load was equal to the full plastic collapse load of the undamaged beam, thus demonstrating the effectiveness of the proposed upgrading scheme. On re-loading the beams after failure, the U-shaped hybrid upgrade continued to act compositely with the steel beam outside of a well confined region corresponding to the original failure location, whereas the beam with the flat plate upgrade exhibited the typical response of a steel beam, owing to debonding having taken place over practically the entire beam length.