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  • 1
    Digitale Medien
    Digitale Medien
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1705-1721 
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The ultrasonic welding process is modeled using a five part model that includes mechanics and vibration of the parts, viscoelastic heating, heat transfer, flow and wetting, and intermolecular diffusion. The model predicts that melting and flow occur in steps, which has been confirmed by experiments. The model also indicates the possibility of monitoring joint quality by measuring the dynamic mechanical impedance of the parts during welding, which has also been verified experimentally by indirectly monitoring the magnitude of the impedance. via measurements of both the power and the acceleration of the base. When the melt fronts of the energy directors meet, at the end of welding, the dynamic impedance of the composites' interface is shown to rise rapidly. This raises the possibility of developing closed loop control procedures for the ultrasonic welding of thermoplastic composites. Ultrasonic welding of polyetheretherketone (PEEK) graphite APC-2 composites produced joints with excellent strengths.
    Zusätzliches Material: 31 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 7 (1986), S. 84-90 
    ISSN: 0272-8397
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: Graphite epoxy composites which are exposed to high humidity environments suffer a loss in their shear and transverse properties. In addition to the effect of moisture on the matrix, thermodynamic theories suggest that the interface may suffer irreversible damage. In this study, we investigated if fiber surface treatments could improve fiber matrix adhesion as well as the wet composite properties. Plasma polymerization was used to generate very thin coatings with the polar component of the surface energy varying from 1.8 to 5.3 (dyne/cm)1/2. These coatings were characterized by ESCA and SEM, and a micro-Wilhelmy technique was used to determine the dispersive and polar components of the surface energy. The uniaxial composites made with the treated fibers were tested wet and dry in short beam shear. It was found, as is well known, that the dry shear properties could be improved by up to 40 percent. Two effective treatments were oxygen etching and polymerization with methylmethacrylate monomer. However, all the wet samples failed at the same stress regardless of the surface treatment used. These results strongly suggest that the shear and transverse properties of the wet composites are dominated by the epoxy and cannot be improved by interface treatments.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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