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Licensed Unlicensed Requires Authentication Published by De Gruyter June 3, 2013

Rheology of Layered Thermoplastic Matrix Composites during Compression Molding

Y. Leterrier and C. G'Sell

Abstract

In view of optimizing the industrial compression molding process of thermoplastic composites, the rheological and microstructural behavior of a polypropylene/glass fiber composite is investigated in model squeeze-flow geometries. The overall stress / strain behavior of the material at various compression rates is recorded and the induced orientation of the fibers is investigated by means of a special electron microscopic characterization method. By contrast to pure polypropylene, it is shown that in the high speed range, the macroscopic flow process is controlled by both the viscous extension and the relative sliding of parallel fibrous layers, the latter becoming unstable when the flow undergoes a rapid transition from divergent to convergent. Under high pressure, voids are dissolved in the polymer melt. In the case of non-isothermal compression, the rheology of the composite is not significantly affected by the cooling of the surface layers. The multilayer plug-flow model based on the sliding mechanism of viscous layers is found to reproduce correctly the experimental stress/strain behavior.


* Mail address: Dr. Yves Leterrier, Laboratoire de Technologie des Composites et Polymères, Département des Matériaux, Ecole Polytechnique Fédérale de Lausannne, CH-1015 Lausaunne, Switzerland

Received: 1995-9-12
Accepted: 1996-5-22
Published Online: 2013-06-03
Published in Print: 1997-03-01

© 1997, Carl Hanser Verlag, Munich