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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 20 (1985), S. 3439-3452 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An electron microscropic study of fracture surfaces and microtomed sections of a cured epoxy resin based on a difunctional bisphenol A type resin cured with different amounts ofm-phenylenediamine is presented. Heterogeneities in the range 5 to 100 nm are seen to be present and have relatively higher crosslink density compared to the surrounding matrix. It is observed that the fracture path is around the heterogeneity and not through it. The size of the heterogeneity is a function of curing agent concentration and also of cure cycle. The stoichiometric sample, which has the highest crosslink density and the highest glass transition temperature, has the smallest heterogeneities. On either side of stoichiometry, the heterogeneity size increases. Samples subjected to a more severe post-curing cycle have much larger heterogeneities. The possible physical basis for these differences is discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 254 (1976), S. 795-802 
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Zusammenfassung Es wurde die Adsorption von Freon 113 (1,1,2 Trichlor-1,2,2 Trifluoräthan) an Graphon bei 260–310 °K gemessen und mit der Adsorption von Krypton bei 104–120 °K auf der gleichen Grenzfläche gemessen. Die Adsorptionsisothermen und die daraus resultierenden thermodynamischen Daten waren für beide Adsorbate im gesamten untersuchten Druckbereich ähnlich. Eine Analyse der Daten legt nahe, daß ein Freonmolekiil annähernd das 2,5fache der Fläche eines Kryptonmoleküls auf Graphon beansprucht. Es ist anzunehmen, daß die Freonmoleküle auf dieser Oberfläche und bei diesen Temperaturen in ihren Rotationsfreiheitsgraden gehindert sind und ihre Dipolachsen senkrecht zur Oberfläche liegen.
    Notes: Summary The adsorption of Freon 113 (1,1,2 trichloro-1,2,2 trifluoroethane) at 260–310 K on Graphon was measured and compared with the adsorption of krypton at 104–120 K on the same surface. The adsorption isotherms, and resulting thermodynamics, for both adsorbates were similar over the entire pressure range studied. Surface area analysis of the data suggests that the Freon molecule occupies approximately 2.5 times the area of the krypton molecule on Graphon. Further, the Freon molecules are hindered in their rotational freedom on this surface at these temperatures, with their dipole axes aligning perpendicular to the surface of the Graphon.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 254 (1976), S. 803-811 
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Zusammenfassung Vergleichende Adsorptionsdaten von Freon 113 (1,1,2 Trichlor- 1,2,2 Trifluoräthan) und Krypton an Graphon zeigten ein sehr ähnliches Adsorptionsverhalten im gesamten untersuchten Druckbereich. Ein Freon 113-Molekül beansprucht etwa die 2 1/2-fache Fläche eines Krypton-Moleküls und orientiert sich mit seiner Dipolachse senkrecht zur Graphonoberfläche. Zusätzliche Adsorptionsdaten zeigen, daß das ähnliche Inertverhalten von Krypton und Freon 113 auch bei energetisch heterogenen Oberflächen wie Anatas, Silicium und wasserbedecktem Siliciumdioxid auftritt.
    Notes: Summary Comparative adsorption data for Freon 113 (1,1,2 trichloro-1,2,2 trifluoroethane) and krypton on Graphon, presented in the preceding paper, showed that the adsorption behavior for krypton, measured at 104–120 K, and Freon 113, measured at 250–370 K, were very similar over the entire pressure range studied. The Freon 113 molecule was shown to adsorb with approximately 2.5 times the molecular area of krypton and to orient with its dipole axis perpendicular to the Graphon surface. Additional adsorption data gathered here indicate that the similar inert behavior of krypton and Freon 113 is also shown on heterogeneous energetic surfaces — anatase, silicon and water covered silica. Surface pressures (π) calculated for Freon 113 on surfaces exhibiting low heats of adsorption are approximately equal to the liquid surface tension, while for surfaces with high heats of adsorption, π can be twice as large.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 25 (1990), S. 4194-4202 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this study attempts are made to develop a basic understanding of the interfacial interactions resulting from the combination of aramid fibres with epoxy matrices in composite materials. The interfacial interactions examined are mechanical stresses due to fibre-matrix thermal strains and Poisson's ratio mismatch, covalent chemical bonding, fibre-matrix wetting, and effects of physicochemical weak boundary layers. Both aramid and carbon fibres have been examined to assess the interfacial interactions by comparing the behaviour of these two fibres in the same matrices. The results indicate that the adhesion of aramid fibres to epoxy matrices lack both the mechanical and the chemical interactions present at the carbon-epoxy interface. Aramid fibres exhibit an interfacial shear strength much lower than the expected theoretical value. Direct observation of the aramid-epoxy interface by transmission electron microscopy shows fibrillar separations within the fibre surface, which may be the limiting factor in achieving greater interfacial adhesion.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 25 (1990), S. 4186-4193 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Despite considerable attempts to increase aramid-epoxy adhesion, to date, the adhesion levels achieved between aramid fibres and epoxy matrices are less than optimum for some applications. A combination of the aramid fibres' morphology, physical and chemical properties, and the interfacial mechanical stresses is responsible for the lack of success in increasing aramid-epoxy adhesion level. A key to improving the aramid-epoxy adhesion is a basic understanding of the interfacial mechanisms by which fibre and matrix interact. There is a considerable number of publications on aramid fibres and their composites. This paper reviews some of the literature relevant to aramid-epoxy bonding mechanisms.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 28 (1993), S. 569-610 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Two major areas of enquiry exist in the field of fibre-matrix adhesion in composite materials. One is the fundamental role that fibre-matrix adhesion plays on composite mechanical properties. The other is what is the “best” method used to measure fibre-matrix adhesion in composite materials. Results of an attempt to provide an experimental foundation for both areas are reported here. A well-characterized experimental system consisting of an epoxy matrix and carbon fibres was selected in which only the fibre surface chemistry was altered to produce three different degrees of adhesion. Embedded single-fibre fragmentation tests were conducted to quantify the level of fibre-matrix adhesion. Observation of the events occurring at the fibre breaks led to the documentation of three distinct failure modes coincident with the three levels of adhesion. The lowest level produced a frictional debonding, the intermediate level produced interfacial crack growth and the highest level produced radial matrix fracture. High fibre volume fraction composites made from the same material were tested for on- and off-axis, as well as fracture, properties. Results indicate that composite results can be explained if both differences in adhesion and failure mode are considered. It will be further demonstrated that fibre-matrix adhesion is an “optimum” condition which has to be selected for the stress state that the interface will experience. The embedded single-fibre fragmentation test is both a valuable measurement tool for quantifying fibre-matrix adhesion as well as the one method which provides fundamental information about the failure mode necessary for understanding the role of adhesion on composite mechanical properties.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 16 (1995), S. 415-420 
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Complex fiber-matrix interactions occur in the processing of glass fiber reinforced polymeric composites, because of the proprietary, complex composition of commercial sizings applied to the glass fiber surface. Research involving a vinyl ester resin system and three model commercial glass fiber sizings, having varying levels of solubility in the resin, has shown that micro-dielectrometry can provide important information about interactions and may be useful as a tool in optimizing sizing-matrix resin interactions. Two distinct types of interactions may be monitored by micro-dielectrometry: The initial resin swelling of the sizing, as well as the dissolution of the sizing into the resin. An estimate of the times associated with swelling and dissolution of the sizing into the matrix resin can be made from micro-dielectric measurements to optimize composite processing.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 30 (1985), S. 4467-4493 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The moisture transport characteristics of a difunctional epoxy resin cured with different amounts of metaphenylene diamine, using two cure cycles, are reported. Besides studying the kinetics of moisture sorption at 20, 50, 75, and 100°C, the investigations also included measurement of thermal expansion coefficients and dynamic mechanical transition of the dry and wet samples. The moisture sorption of the sample is shown to be related to its specific volume and hence to its fractional free volume. In the glassy state, the free volume is apparently in the form of frozen voids, and moisture sorption/desorption at this temperature is of the Langmuir type with little or no bond formation. At higher temperatures the free volume is generated predominantly through segmental motion of the α transition. The Henry's Law mode becomes operative, and the moisture can now form bonds. The possible effect of nonuniform crosslink density on moisture sorption is also considered.
    Additional Material: 26 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 25 (1985), S. 812-823 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The tensile mechanical properties and fracture toughness of a Bisphenol-A type difunctional epoxy resin, cured with different amounts of metaphenylene diamine, using two cure cycles, were determined over a range of temperature. The tensile modulus in the glassy state was seen to be predominantly related to intermolecular packing, while in the rubbery state crosslink density was the important factor. Yielding appeared to be due to an increase in free volume as a result of dilatation during the tensile test and was related to a critical shear stress. The large strain properties like tensile strength, elongation-to-break, and toughness showed a more complex dependence on chemical structure, molecular architecture, intermolecular packing, and crosslink density. The roles played by the relaxation processes in determining mechanical properties are highlighted.
    Additional Material: 22 Ill.
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  • 10
    Publication Date: 1993-01-01
    Print ISSN: 0022-2461
    Electronic ISSN: 1573-4803
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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