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  • 1
    Electronic Resource
    Electronic Resource
    The microstructure of rigid polyurethane foams (1982)
    Springer
    Journal of materials science 17 (1982), S. 220-224 
    Details
    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 A study has been made of the microstructure of rigid closed-cell polyurethane foams in the density range 35 to 420 kg m−3. Existing models for the structure of foams of this type have been evaluated using optical and scanning electron microscope techniques. Foams with a density of the order of 35 kg m−3 are shown to be best represented as a pentagonal dodecahedron. Medium density foams from 70 to 300 kg m−3 have a structure described as rounded polyhedra and high-density foams from 300 to 420 kg m−3 have an isolated spherical structure. A relationship between average cell size and density is given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00809056
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  • 2
    Electronic Resource
    Electronic Resource
    The fracture toughness of reinforced polyurethane foam (1978)
    Springer
    Journal of materials science 13 (1978), S. 722-730 
    Details
    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 A microscopic study of the fracture processes occurring in rigid, closed-cell polyurethane foam has been combined with an assessment of toughness using fracture mechanics in order to investigate the reinforcement capability of chopped glass fibres. One aspect of fibre reinforcement is seen as an extension of a mechanism that could be responsible for the relatively high surface energy of the base foam. There is also an increase in modulus, and a further contribution to toughness is derived from fibre pull-out. An optimum, though unspecified, fibre length exists that gives the most efficient reinforcement of the foam considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00570506
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  • 3
    Electronic Resource
    Electronic Resource
    The crystallization and interfacial bond strength of nylon 6 at carbon and glass fibre surfaces (1975)
    Springer
    Journal of materials science 10 (1975), S. 2035-2043 
    Details
    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 The nucleation and crystallization of nylon at the interface in glass-fibre and carbon-fibre reinforced nylon 6 composites has been investigated by electron microscope studies of sectioned and etched bulk specimens and solution cast and melt crystallized thin films. The fracture energies of the composites were obtained from tensile strength tests and the interfacial bond strengths were calculated from fibre pullout measurements. The fibres are shown to nucleate a columnar structure at the interface with marked differences between the structures nucleated by glass fibres and by carbon fibres and also between that nucleated by type I and type II carbon fibres. The structure around glass fibres was non-uniform and influenced to some extent by the presence of the size coating on the fibre surface. In the carbon-fibre composites the columnar structure was due primarily to physical matching of the graphite crystallites. Surface treatment of the carbon fibres to improve chemical bonding is shown to have a significant effect on bond strength which cannot be explained in terms of the columnar structure at the fibre surface. The treated fibres gave rise to only small amounts of fibre pull-out and low fracture energies whereas the untreated fibres showed extensive pull-out which was reflected in high fracture energies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00557481
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  • 4
    Electronic Resource
    Electronic Resource
    The fracture toughness and fracture morphology of polyester resins (1976)
    Springer
    Journal of materials science 11 (1976), S. 1113-1124 
    Details
    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 The change in fracture toughness of an orthophthalate based medium reactivity polyester resin with change in resin flexibility, catalyst content, cure temperature and liquid environment, has been investigated. Various specimen geometries including simple double cantilever beam and tapered double cantilever beam have been used and the results obtained with the different geometries are in good agreement. The critical flaw size for the resin has been determined and an estimate obtained of the radius of the plastic zone under plane strain conditions. The solvent absorption characteristics of the resin were found to be effected by catalyst content, resin flexibility and by residual strains. Observations of the fracture behaviour, using both fracture toughness and tensile specimens have revealed a fracture surface morphology very similar to that of glass but with limited plastic deformation occurring.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02396647
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of microstructure and crystallinity on the tensile properties and fracture behaviour of injection-moulded polytetramethylene terephthalate (1977)
    Springer
    Journal of materials science 12 (1977), S. 141-152 
    Details
    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 The variation in morphology and crystallinity across injection-moulded ASTM bars of the semi-crystalline thermoplastic, polytetramethylene terephthalate (PTMT), has been characterized by optical microscopy and X-ray diffraction techniques and related to the initiation and mode of fracture of the material. Optical microscope observation of microtomed sections reveal a gradual variation of morphology from skin to core with changes in spherulite size and distribution together with flow patterns within the outer skin and core contributing to the overall complexity. An increase in crystallinity has been found to occur in the non-flow regions and the fracture behaviour and modes of deformation have been interpreted in terms of the band structure and related to the flow patterns. A modification of Tadmor's model is shown to adequately represent the mouldfilling process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00738479
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  • 6
    Electronic Resource
    Electronic Resource
    The mechanical properties and fracture behaviour of unidirectionally reinforced Nylon 6 (1977)
    Springer
    Journal of materials science 12 (1977), S. 365-372 
    Details
    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 The tensile and shear properties of Nylon 6 polymerizedin situ around unidirectionally aligned carbon and glass fibres have been investigated and the fracture behaviour characterized by optical and scanning electron microscopy. The tensile strengths are found to lie within the limits predicted by the law of mixtures and deviations from the predicted strengths have been correlated with fibre type and surface treatment. The shear strength values follow the same trend and an important mode of fracture in bending is shown to be the compressive failure which accompanies a yield drop in the load deflection curve. Depending upon the fibre type and the properties of the matrix this compressive damage need not lead to catastrophic failure of the composite as, in certain cases, the matrix can undergo substantial deformation before failure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566280
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  • 7
    Electronic Resource
    Electronic Resource
    The effect of polymerization conditions and crystallinity on the mechanical properties and fracture of spherulitic nylon 6 (1975)
    Springer
    Journal of materials science 10 (1975), S. 1127-1136 
    Details
    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 The molecular and structural parameters controlling the mechanical properties, deformation and fracture of spherulitic nylon 6 have been investigated. The nylon was prepared by the anionic polymerization of ε-caprolactam and the polymerization conditions were varied to give samples having a range of spherulite diameter, molecular weight and degree of crystallinity. The tensile properties and fracture mode of the nylon varied considerably with degree of crystallinity and polymerization temperature. High crystallinity and low polymerization temperatures below 423 K gave a brittle material. Polymerization above 423 K resulted in a ductile material which showed a yield drop. In this material final fracture was preceded by the formation of inter and trans spherulitic cracks which coalesced to form a large cavity that led to final failure. In nylon having a low degree of crystallinity, fracture was fibrillar in nature and occurred by the ductile drawing of the material to strains greater than 250%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00541393
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  • 8
    Electronic Resource
    Electronic Resource
    The fracture toughness and fracture morphology of polyester resins (1976)
    Springer
    Journal of materials science 11 (1976), S. 1113-1124 
    Details
    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 The change in fracture toughness of an orthophthalate based medium reactivity polyester resin with change in resin flexibility, catalyst content, cure temperature and liquid environment, has been investigated. Various specimen geometries including simple double cantilever beam and tapered double cantilever beam have been used and the results obtained with the different geometries are in good agreement. The critical flaw size for the resin has been determined and an estimate obtained of the radius of the plastic zone under plane strain conditions. The solvent absorption characteristics of the resin were found to be effected by catalyst content, resin flexibility and by residual strains. Observations of the fracture behaviour, using both fracture toughness and tensile specimens have revealed a fracture surface morphology very similar to that of glass but with limited plastic deformation occurring.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00553121
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  • 9
    Electronic Resource
    Electronic Resource
    The mechanism of reinforcement of polyurethane foam by high-modulus chopped fibres (1977)
    Springer
    Journal of materials science 12 (1977), S. 708-717 
    Details
    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 The morphology and fracture behaviour of polyurethane foams reinforced by short chopped fibres have been investigated. The presence of the fibres is shown to give rise to localized change in the foam morphology and the extent of this depends upon the fibre bundle size which is affected by the surface treatment. The changes in morphology are correlated with changes in the tensile properties of the foams at ambient and cryogenic temperatures. The systems are shown to be matrix limited with failure occurring remote from the interface which assumes a poassive role during tensile fracture. A critical fibre length for reinforcement of polyurethane foam, which depends on matrix shear strength and foam density, is defined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00548161
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  • 10
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    The microstructure of rigid polyurethane foams (1982)
    Springer
    Details
    Publication Date: 1982-01-01
    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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