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  • Wiley-Blackwell  (9)
  • 1
    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.
    Type of Medium: Electronic Resource
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  • 2
    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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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 18 (1978), S. 1001-1005 
    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: Swelling and hygroelasticity of polymers are discussed in terms of a coefficient of hygroelasticity defined here by analogy with the coefficient of thermal expansion. The relationship between the proposed coefficient and the mechanical properties of the material and the stresses which develop in it is established. The relationship provides means for predicting the lifetime of the polymer under conditions similar to those used for measuring the coefficient of hygroelasticity. The experimentally examined behaviors of two systems, polyester-boiling water and epoxy-methylene chloride at 18°C, are in reasonable agreement with the predictions.
    Additional Material: 6 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 56 (1995), S. 959-966 
    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 microstructure of polyethylene (PE)/PE composites, consisting of the high-density PE (HDPE) matrix and ultrahigh molecular-weight PE (UHMWPE) fibers, was investigated. Single-fiber composites were prepared and analyzed in a hot-stage crystallization unit attached to a polarizing microscope, aiming to find out how the conditions of crystallization affected the transcrystallinity (tc) growth at the fiber-matrix interface. Thermal treatments leading to two extreme microstructures, of either maximum or minimum thickness of the transcrystalline zone, were sought. It was found that a uniform transcrystalline layer was developed on the UHMWPE fiber from the HDPE melt under isothermal conditions, whereas rapid cooling from the melt prevented the generation of tc. The mechanical properties of unidirectional composite laminae either with or without the transcrystalline zone were measured. A comparison of the transverse strength predicted by theoretical models with the experimental values revealed good interfacial adhesion in the PE/PE system. It was shown that the tc growth had a negligible effect on the composite mechanical properties in the longitudinal direction, whereas it resulted in a 50% decrease of the transverse tensile strength and strain to failure. Scanning electron microscopy attributed that observation to premature brittle failure at tc/tc contact regions. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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  • 6
    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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  • 7
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: This article introduces a new compliant and selectively biodegradable filament wound vascular graft and reports the findings of a shorterm implantation study. A basic feature of filament winding is its ability to tailor and better control the mechanical properties of the prosthesis, so that a closer match with the anisotropic properties of native arteries is achieved. The elastomeric vascular grafts comprise poly(ether urethane urea) fibers (Lycra) embedded in a twocomponent matrix consisting of poly(ether urethane) (Pelle- thane) and a highly flexible poly(ethy1ene glycol)/poly(lactic acid) biodegradable segmented copolymer (PELA). Typical tensile modulus values fall in the few megapascals (MPa) range, this being comparable to that of natural arteries. The wound graft exhibits excellent handling and suturability characteristics as well as enhanced burst strength. Furthermore, due to its biodegradable constituent, the prosthesis combines minimal intraoperative blood loss and high healing porosity. The graft displays initially negligible in vitro water permeation, which increases gradually with time. In this short-term study, the prostheses were implanted in the canine carotid, and their biological performance was compared to that of expanded Gore-Tex. The luminal surface of the wound grafts was coated with a thin layer of pseudointima, strongly adhered to the prosthesis surface. Contrasting with the very stiff Gore-Tex grafts, the filament wound prostheses retained their high compliance, being highly pulsatile upon explantation. Histological studies fully corroborated these findings, underscoring the healing properties of these new filament wound vascular prostheses. © 1992 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 2 (1981), S. 132-136 
    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: Moisture penetration at 95°C into glass fiber and graphite fiber-reinforced epoxies is examined in stressed and unstressed materials. The study focuses on the effect of the angle between the stress and the fiber directions on the diffusivities. It is found that the consequence of applying external stresses to composites is an increase in their rate of moisture absorption, their maximum moisture content, and in the diffusion coefficients. As the angle between the loading and fiber directions in increased the rate and the maximum value of moisture absorption also increase. Their ratio, however, remains constant resulting in loading angle independence of the exposure of the composites to water produces a typical damage mechanism which enhances moisture take-up.
    Additional Material: 4 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 6 (1985), S. 9-12 
    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: A model for the effect of external loading on diffusion into the bulk resin matrix of unidirectional 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. The latter is calculated by substracting the volume strain of the fibers from that of the composite. The ratio of the diffusion coefficients in the stressed and unstressed states is expressed as a function of the stress level, the volume fraction of the fibers, and the angle between the applied stress and the fiber direction. Calculations for a glass-fiber-reinforced epoxy composites are presented.
    Additional Material: 4 Ill.
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