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  • Chemistry  (72)
  • Polymer and Materials Science  (40)
  • Chemical Engineering  (35)
  • Atomic, Molecular, and Optical Physics  (1)
  • Glass reinforced composites  (1)
  • Instable interface  (1)
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  • 1
    facet.materialart.
    Unknown
    American Physical Society (APS)
    Publication Date: 2012-05-23
    Description: Author(s): Nicolais L. Guevara, Yujun Wang, and B. D. Esry We calculate the three-body spectrum for identical bosons interacting via attractive 1/ r 2 potentials. We find an infinite number of three-body states even when the pair interactions are too weak to support any two-body states. These new states thus share this surprising scenario with the Efimov effe... [Phys. Rev. Lett. 108, 213202] Published Tue May 22, 2012
    Keywords: Atomic, Molecular, and Optical Physics
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied composite materials 1 (1994), S. 231-245 
    ISSN: 1573-4897
    Keywords: MMC ; Nickel coated graphite ; Squeeze casting ; Instable interface ; Electroplating
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Metal Matrix Composites (MMC's) reinforced with continuous fibers were generally fabricated by a foil-sandwich technique or by liquid metal infiltration. Liquid metal infiltration may be used to cast final shapes in molds containing fiber preforms. It is also used to make composite wire from which may be fabricated panels and shapes by hot-press diffusion bonding or pultrusion. The major drawback of this method is that the molten matrix must wet the fiber for successful infiltration to occur, requiring special fiber surface treatments or matrix additives, and that, molten metals generally dissolve or degrade the fibers, necessitating a barrier coating on the fibers. All these problems can be solved using carbon fibers coated with metallic layers, e.g. nickel. This work analyses an easy method to produce modified carbon fibers by electroplating and the process of its recristallization. The topography of the growth front of the deposit has been studied. At temperatures higher than about 300° C an annealing under vacuum is required, because of the high reactivity of metal coating, nevertheless the heat treatment of metal deposit produces always an embrittled material.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-4897
    Keywords: Flexural fatigue ; Glass reinforced composites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Conclusions Flexural fatigue of uniaxially and biaxially stressed IPN/glass mat composites was investigated using four point bend (4PB) and concentrically loaded (CL) specimen geometries. Regions of nearly constant bending moment between the inner spans of a 4PB beam and within the inner annulus of a CL circular plate yield quasi-uniform uniaxial and biaxial stress, respectively, on the tensile faces. The specimen dimensions were optimized for both loading geometries to give: (1) reduced specimen deflection through maximizing the ratio of the induced tensile stresses to the applied load, (2) minimized contact stresses by maximizing the induced stress with respect to the unit contact load, and (3) a large material volume exposed to the maximum cyclic stress (i.e., statistical fracture initiation). A power model was used to analyze the fatigue data for the 4PB and CL specimens. Both IPN composite materials studied fatigued more rapidly under the more severe loading conditions imposed by the CL specimen geometry. Fractography revealed that debond fracture was the dominant damage process for both geometries. The initial debond cracks were uniformly distributed throughout the stressed regions, confirming the presence of nearly uniform tensile stress. Damage localization followed after further cycling and was characterized by a locally high debond fracture density, fiber fracture, and always occurred where several glass strands crossed near the specimen surface. Final specimen failure resulted from the preferential growth of dominant cracks through the specimen thickness.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1786-1795 
    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 possible multimodal sorption mechanisms in glassy amorphous poly-ether-ether-ketone (PEEK) are presented. By varying the penetrant-polymer affinity, experimental temperature, and external solvent activity, a broad range of sorption behaviors from ideal Fickian diffusion to limiting relaxation controlled kinetics is observed. In particular, water, methylene chloride, and n-heptane sorption kinetics are analyzed and interpreted on the basis of the multiple transport mechanisms. Low uptake liquid n-heptane sorption follows ordinary Fickian diffusion. Analogously, water vapor at low activity, is sorbed in small amounts in the same limiting mode while, at higher activities, the moderately higher penetrant uptakes induce slow relaxation coupled with ideal Fickian diffusion. The highly interacting methylene chloride leads to ideal Fickian diffusion only at very low activities, while anomalous non-ideal Fickian diffusion and limiting Case II and diffusion controlled swelling are observed at moderate and at high solvent activities, respectively. Limiting Case II sorption of methylene chloride in PEEK has been observed only at a very low temperature (-32°C). The optical microscopy observations of cryogenically fractured samples contacted with liquid methylene chloride at 5, 20 and 36°C revealed the presence of a sharp front moving linearly with the square root of time. Solvent induced crystallization in methylene chloride swollen samples was detected by means of differential scanning calorimetry (DSC) and wide angle X-ray scattering (WAXS). Finally, sorption from liquid methylene chloride/n-heptane solutions with varying compositions are presented. The progressive increase of the more high sorbing methylene chloride concentration in the solutions, leads to the same wide variety of sorption behavior observed in the methylene chloride vapor sorptions. The gas chromatographic (GC) analysis indicated that the presence of methylene chloride enhanced the n-heptane sorption in the polymer.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 314-320 
    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: Dynamic-mechanical and dielectric characterization of the cold crystallization of PEEK has been performed in order to develop a non-destructive evaluation method of crystallinity in thermoplastic matrices. The Avrami approach is applied here to describe the Poly(ether ether ketone) (PEEK) crystallization kinetics after an appropriate reduction of dynamic-mechanical and dielectric parameters. Avrami exponents obtained from dielectric characterization are comparable with those obtained with DSC measurements reported in literature, while the exponents obtained from the dynamic-mechanical characterization are higher, reflecting also changes in the aspect ratio of the growing crystals. Variations in the glass transition temperature detected during cold crystallization are analyzed and analogies between PEEK and PET are discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 18 (1974), S. 2809-2818 
    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: Viscosity measurements made by a cone-plate viscometer on polyisobutylene in decalin solutions at different concentrations and their corresponding glass bead suspensions with filler loadings up to 40% by volume are reported. The range of shear rate $ \dot \gamma $ investigated is between 0.1 and 1000 sec-1. The solutions show shear-thinning behavior, and the relative viscosity ηr of the slurries generally decreases with increasing shear rate. The results indicate two different types of mechanism, respectively at high and low shear rates. At low $ \dot \gamma $, the relative viscosity can be correlated extending relations already well known for suspensions in Newtonian liquids which are based on the mechanism of aggregate disruption. The behavior at high $ \dot \gamma $ values is believed to be due to the influence of the filler on the flow properties of macromolecules, in particular on relaxation time. Through a shifting procedure, an increase in relaxation time which depends on filler content and not on polymer concentration is shown.
    Additional Material: 9 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 33 (1987), S. 2077-2086 
    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 application of ultraviolet (UV)-curable polymeric coatings provides optical fibers with improved strength, microbending resistance, and long-term durability. To ensure constant optical properties of the glass fibers during their life, fully polymerized coatings are needed. Test methods capable of determining the degree of cure and the consistency of the polymeric materials used are therefore required by the fiber technology. This investigation deals with the description of a calorimetric test method for the direct determination of the prepolymer reactivity and its final degree of cure. The analytical technique uses a modified differential scanning calorimeter (DSC) capable of direct measurements of heat fluxes generated during the UV-activated polymerization of photoinitiated acrylic prepolymers. Finally, the degree of cure and the glass transition temperatures were determined for the polymerized coating also in presence of sorbed moisture.
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 37 (1989), S. 381-392 
    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 kinetics of diffusion of water from different activity vapors and liquid phase have been investigated in glassy amorphous poly(aryl ether ether ketcne) (PEEK) films at the temperature of 60°C and in glassy semicrystalline PEEK sheets at different temperatures, respectively. In the case of the amorphous PEEK films (250 μm thick) the data at low activity levels were interpreted by means of a purely Fickian mechanism. At higher activity levels the material has shown the presence of a relaxation process; in this case the data have been interpreted using a model proposed by Berens and Hopfenberg. Equilibrium sorption isotherm is also reported. Liquid water sorption in semicrystalline (30%) PEEK sheets (2 mm thick) has been determined to follow the classical Fickian mechanism. The water uptake values obtained for both amorphous and semicrystalline PEEK, confirm the good moisture and liquid water resistance of this kind of high performance thermoplastic polymer.
    Additional Material: 7 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 75-82 
    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: Water sorption in epoxy based materials was analyzed by dielectric spectroscopy using remote sensors. A method to determine diffusion coefficients from the changes in permittivity during water absorption is proposed and was verified experimentally by comparison with standard water gain measurements. Although the technique is limited by electrode polarization phenomena, it is sensitive to the presence of water molecules and is capable of detecting different levels of water concentration as a function of frequency. The utilization of remote sensors demonstrated the capability of dielectric analysis to be applied both in the laboratory environment, and on a larger scale, as a nondestructive technique for monitoring environmental changes in actual polymer matrix composite parts.
    Additional Material: 11 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 658-665 
    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: Phase behavior, thermal, rheological and mechanical properties plus morphology have been studied for a binary polymer blend. The blend is phenolphthalein polyethersulfone (PES-C) with a thermotropic liquid crystalline polymer (LCP), a condensation copolymer of p-hydroxybenzoic acid with ethylene terephthalate (PHB-PET). It was found that these two polymers from optically isotropic and homogeneous blends by means of a solvent casting method. The homogeneous blends undergo phase separation during heat treatment. However, melt mixed PES-C/PHB-PET blends were heterogeneous based upon DSC and DMA analysis and SEM examination. Addition of LCP in PES-C resulted in a marked reduction of melt viscosity and thus improved processability. Compared to pure PES-C, the charpy impact strength of the blend containing 2.5% LCP increased 2.5 times. Synergistic effects were also observed for the mechanical properties of blends containing 〈 10% LCP. Particulates, ribbons, and fibrils were found to be the typical morphological units of PHB-PET in the PES-C matrix, which depended upon the concentration of LCP and the processing conditions.
    Additional Material: 13 Ill.
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