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  • 1
    Digitale Medien
    Digitale Medien
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1358-1365 
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Interest in the development of polymeric materials for high temperature, electronic and microelectronic applications has led to an increasing number of new polymers. Many of these polymers have complex organic ring structures and semirigid backbones, characteristics that have posed some difficulties for structural analysis. The purpose of this paper is to test and compare two practical nondestructive optical techniques, polarized optical microscopy and polarized refractometry, for the determination of three-dimensional surface and bulk anisotropy in these advanced materials. The optical techniques are first tested on a series of optically homogeneous uniaxially oriented isotactic polypropylene films and then applied to the analysis of high refractive index Kapton (PMDA-ODA) polyimide films. The study includes a test of the validity of the compensator method, including the effect of fringe jumping, the use of polymer retarders, and the tilting technique of Stein.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 259-267 
    ISSN: 0887-6266
    Schlagwort(e): relative dispersion ; birefringence ; fringe jumping ; Kapton PMDA-ODA polyimide ; polypropylene ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The relative dispersion of birefringence, Db, is determined for isotactic polypropylene and Kapton HA PMDA-ODA polyimide films. Db is then used to identify the dependence of dispersion on the orientation of polymers and is interpreted in terms of fringe jumping. Optical relationships between the in-plane birefringence and wavelength are formulated to predict the in-plane birefringence of oriented Kapton HA PMDA-ODA polyimide films at any wavelength. These relations can be used for the direct comparison of the in-plane birefringence of Kapton PMDA-ODA polyimide films obtained from different optical techniques (i.e., polarized microscopy, polarized refractometry, wave guide coupling, etc.). © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Advances in Polymer Technology 9 (1989), S. 253-264 
    ISSN: 0730-6679
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: The effect of the constituent material on the mechanical properties and on the overall crack propagation behavior of uniaxial graphite/epoxy composites was studied using two different types of graphite fibers, i.e., PAN precursor and pitch precursor fibers in combination with an epoxy known for its toughness. The tensile properties and interlaminar shear strength (ILSS) of composites with various fiber volume fraction were studied using an Instron Universal Testing Machine. The fracture surface of composites was studied using scanning electron microscopy (SEM). The surprising result from the tensile tests is that the percent elongation of AS4/epoxy composites was much higher than that of individual components, i.e., the epoxy and the fiber. The stress-strain curves of AS4 fiber/epoxy composites show yielding. The yielding is interpreted to result from shear stress concentration due to the fiber breakage. Two causes of failure mode were observed in this study: (1) ductile plastic deformation by the PAN-based AS4/epoxy composites; (ii) brittle catastrophic failure shown by the pitch-based VSB-16/epoxy composites. The tensile strengths and moduli of the composites increased as the volume fraction of fibers increased. The principal fracture features of AS4/epoxy composites under tension were fiber pullout (bundles and single fibers) and very rough fracture surface due to the pullout of fiber bundles with epoxy, whereas VSB-16/epoxy composites under tensile and bending loads showed only tensile (or compressive) failure. The composites of epoxy/PAN (polyacrylonitrile)-based fibers (AS4) showed greater ILSS than those of the pitch-based fiber (VSB-16)/epoxy. The most characteristic features of the interlaminar shear failure surface of AS4/epoxy composites are delamination and formation of hackles.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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