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Eingeladener Vortrag
- nein (19)
Widely-used methods for characterising the fibre/matrix interface in polymeric composites are the fragmentation test and the droplet test as a special kind of the single-fibre pull-out test. A severe disadvantage of these tests is that non-realistic model samples are investigated which contain only one fibre in the matrix. In order to obtain data about the effect of the different residual stress situations for fibres in such samples and in composites, pull-out tests of E-glass fibres in polystyrene and polycarbonate are performed using samples, where the investigated fibre is surrounded by 0 to 3 other near fibres. Neighbouring fibres can increase the pull-out forces by a factor of three and the interfacial toughness by a factor of four. This has to be taken into account, if the tests are performed not only for comparison reasons but for measuring interface properties.
Energy based characterization of the fibre-matrix interface using the pull-out and push-in test
(1997)
An Advanced Equipment for Single-Fibre Pull-Out test designed to monitor the fracture process
(1993)
Influence of the Interface Strenght on Local Failure Processes in Fiber Reinforced Composites
(1999)
The energy release rate of the fiber/polymer matrix interface: measurement and theoretical analysis
(1995)
The Energy Release Rate of the Fiber/Polymer Matrix Interface: Measurement and Theoretical Analysis
(1997)
Characterisation of the fibre/matrix interface in reinforced polymers by the push-in technique
(1997)
The push-in test is the only micromechanical test method that is not restricted to artificial fibre/matrix arrangements, but allows the in situ characterisation of interfaces in composites fabricated and stressed under realistic conditions. However, with the application of this method to reinforced polymers some problems arise both in the mathematical model for evaluating test data and in the practical performance of the test. Because in some cases the deformation of the relatively compliant polymeric matrices cannot be neglected, an extension of the existing model is required. For this purpose, the elastic energy of the material around the debonded part of the fibre is estimated and included in the energy-balance analysis. Because of the small diameter of the fibres usually used for reinforcing polymers, a test apparatus was designed which ensures a high positioning accuracy in the xy plane as well as in the z direction. In order to minimise thermal and mechanical influences, the microscope for fibre selection and the force sensor/indenter are directly connected together and the apparatus is designed to be stiff in all components. A solid-state bending joint guarantees very precise control of the axial movement. Three examples of the application of this easy-to-handle and low-cost test apparatus are presented briefly in the paper: assess fibre/matrix combinations, measures to improve the interfacial adhesion and the influence of water on the interface.
An advanced equipment for single-fibre pull-out test designed to monitor the fracture process
(1995)
Pull-out of Single Fibres
(1994)
Fatigue Behaviour of High-Performance Fibre-Reinforced Composites with a Thermoplastic Matrix
(1990)
Measurement and theoretical analysis of the interfacial toughness by micromechanical experiments
(1998)
The energy release rate of the fiber/polymer matrix interface: measurement and theoretical analysis
(1995)
Anlaß der Untersuchungen waren die häufig vorgetragenen Vorbehalte gegen die Verwendung "umweltschonend hergestellter" Papiere - sog. Recycling-Papiere ("RC-Papiere") - im Behördenbereich. Drei verschiedene RC-Papier-Sorten wurden auf ihre Verwendbarkeit im erweiterten Bürobereich im Vergleich mit dort üblicherweise eingesetzten herkömmlichen Sorten untersucht, und zwar auf Eignung als Schreib-, Druck- und Kopierpapier sowie als Vorlage zum Kopieren, Fernkopieren und Mikroverfilmen. Ferner wurden die chemischen und physikalischen Kennwerte der Papiere ermittelt und das Verhalten bei künstlicher Alterung geprüft.
Es konnte gezeigt werden, das RC-Papiere für die meisten Anwendungsfälle technisch durchaus geeignet sind. Bei besonderen Anforderungen - z.B. an die Lauf- oder Wiedergabeeigenschaften bei einzelnen Geräten oder Verfahren, an die mechanischen Eigenschaften oder an die Dauerhaftigkeit allgemein - sollten die Grenzen dieser Papiere beachtet werden.