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  • 1
    ISSN: 1573-4897
    Keywords: transcrystanninity ; microcomposites ; fragmentation ; thermal stresses ; interfacial shear strength
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Based on the compressive thermal fragmentation test and model proposed recently, a transcrystalline phase grown adjacent to the surface of a high modulus carbon fibre embedded in polycarbonate was found to lower the thermal stresses in the fibre. The interfacial shear stress, calculated from the compressive stress profile generated by the model, was lowered in the presence of a transcrystalline layer. It is proposed that the transcrystalline layer reduces the radial stresses acting on the fibre, thereby reducing the friction component of the interfacial bond strength.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 22 (1987), S. 2435-2446 
    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 diffusion of water into unidirectional Kevlar fibre reinforced epoxy resins was studied as a function of fibre orientation and, for unidirectional (0°) composites, as a function of volume fraction (Vf). As the angle increased from 0 to 90°, the diffusivity increased dramatically; i.e. as more and more fibre-ends were exposed to the shorter diffusion path, the diffusivity increased. The equilibrium weight gain of water (M∞) in the composites increased with theV f of the fibre. M∞ of Kevlar fibre was calculated to be 4.9%. At a constantV f, specimens of the same thickness and width but different lengths were used to determineD 22, the diffusion coefficient of the composite along the fibre, andD 22, the diffusion coefficient transverse to the fibre. The initial data for the percentage weight gain against the square root of time were non-linear, which was attributed to the anisotropy of the diffusion process. The anisotropy arises from the much higher value ofD 11 as compared toD 22. AsV f increased from 0.37 to 0.59,D 11 increased from about 0.83 to about 4.2 × 10−12m2 sec−1, whereasD 22 decreased from 0.21 to 0.033 × 10−12 m2 sec−1. Thus, the ratioD 11/D 22 increased from 3 to over 100 as U increased. The experimental sorption data could be fitted satisfactorily with these diffusion coefficients.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 15 (1980), S. 631-634 
    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 Swelling and hygroelasticity of unidirectional glass fibre-reinforced epoxy composites in boiling water is studied with respect to the angle θ between the direction of orientation and the direction of measured dimensional change. The results are expressed in terms of the dependence of θ of a hygroelasticity coefficient. A very good agreement is observed between the experimental results and the theoretical equation, already verified in the case of the angular dependence of the coefficient of thermal expansion. This is taken as additional support for the analogy between thermoelastic and hygroelastic behaviour in composites. The experimental longitudinal and transverse hygroelasticity coefficients are found to be different from predictions based on Schapery's equation. However, it is shown that these equations can produce possible valid estimates of μ L and μ T provided the mechanical properties of the swollen constituent materials are used.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 21 (1986), S. 26-30 
    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 model for the effect of external uniaxial loading on the equilibrium moisture content in uni-directional composite materials is proposed. The model attributes the effect to a change in the free volume of the resin matrix, which is equal to its volume strain.M ∞ of the stressed state is calculated as a function of the stress level, the volume fraction of the fibres and the angle between the applied stress and the fibre direction. Moisture absorption experiments were performed on pure epoxy matrix and on graphite-epoxy composites. The effect of the parameters mentioned above onM ∞ was examined, and excellent agreement was found between the experimental and the calculated values. For stresses which were applied in the direction of the fibres (θ = O°) the experiment showed thatM ∞ decreased with the increase in the stress. We attribute this anomaly to the generation of residual stresses in the composite due to swelling.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 13 (1977), S. 363-364 
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 11 (1975), S. 534-536 
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 7
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 17 (1977), S. 799-802 
    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: Investigated are the swelling and hygroelasticity of a unidirectional glass fiber-reinforced epoxy composite subjected to boiling water for 24 hrs. By analogy with thermoelasticity, a coefficient of hygroelasticity is defined and shown to be predictable from the coefficients of the constituent materials by Schapery's equations. A mechanism for water penetration into the composite which combines capillarity and diffusion is proposed on the basis of the results of the water take-up as a function of the composite specimen width (fiber length).
    Additional Material: 5 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 50 (1993), S. 503-512 
    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: Drawing on the difference in melting points of UHMPE fiber (150°C) and HDPE matrix (130°C), single-polymer composites were fabricated under various processing conditions. Because of the chemical similarity of the composite components, good bonding at the fiber-matrix interface could be expected. The matrix, the fiber, and unidirectional composite laminae were studied using TMA and DSC analyses, a hot-stage crystallization unit attached to a polarizing microscope, and an universal tensile testing machine. The TMA showed negative thermal expansion of the fiber over the complete temperature range of the experiment. Three regimes of contraction according to the values of the thermal expansion coefficient were detected. DSC analyses of either the fiber or the composite specimens did not show any appreciable changes after various thermal treatments. They also showed no evidence of fiber relaxation during manufacture, probably because of the pressure-related transverse constraint. The tensile strength and modulus values of the composite appeared to be fairly high and close to those reported for other composites reinforced with polyethylene (PE) fibers. An apparent maximum on the temperature dependencies of tensile properties was observed. A study of the matrix microstructure did not give any proof of transcrystalline growth at the fiber-matrix interface even for chemical or plasma surface-treated fibers. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 870-877 
    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 hygroelastic behavior of polymers, in which the diffusion mechanism is characterized by a sharp advancing boundary between the swollen shell and the core, was studied. A highly anisotropic swelling response was observed. The an-isotropy of the swelling strains was caused by the mechanical constraints exerted by the stiff core on the penetrated shell. The swollen systems were viewed as analogous to a composite material comprising a stiff fiber embedded hi a soft matrix. The size and relative dimensions of the core were found to be the crucial factor determining the antsotropic response en-countered. The experimental system employed was of poly(methyl methacrylate).
    Additional Material: 11 Ill.
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  • 10
    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: Polymers in which the diffusion mechanism was characterized by a sharp advancing boundary between the swollen shell and the core showed a highly anisotropic swelling response. The anisotropy of the swelling strains was caused by the mechanical constraints exerted mutually by the two regions of the specimen. The swelling stresses developing during the process eventually led to fracture of the polymer specimen. An analytical model which explained the modes of failure of the polymer under the swelling stresses was developed. The proposed approach was based on the general analogy existing between the studied swollen specimens and composite materials. A model for the prediction of the anisotropic hygroelastic response of the swollen systems was also proposed.
    Additional Material: 13 Ill.
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