Dray Bensahkoun, Delphine (2006) Predictin of the thermoelastic properties of an injection molded short-fiber composite. PhD thesis Mécanique et matériaux, ENSAM 2006ENAM0008.
Abstract
The production of molds for injection of thermoplastics is highly expensive, that is why industrialists would like to be able to correctly predict the final geometry of injected parts. To do it, a rheological calculation coupled to a thermo-mechanical calculation by finite elements, which requires the materials properties, must be carried out in the solid. Today, the mechanical properties that are used in the code are generally not dependent on temperature, neither directly dependent on the local fiber orientation. The purpose of this study is precisely to predict the elastic properties, as well as the thermal expansion coefficients of injection molded short-fiber composites, by using techniques of homogenization. The originality of the work is the estimation of the properties over a broad range of temperatures, as a function of the local fiber orientation. A 1st part presents the methods for measuring the fiber orientation state: in the particular case of injection, where the fibers lie as a majority in the injection plane, we have developed a new technique in order to determine the spatial fiber orientation, which is fast and accurate. It consists in analyzing the image, taken with a Scanning Electron Microscope, of a single section plane cut at a certain angle from the injection direction. In a 2nd part, the thermo-elastic composite properties are evaluated by Mori-Tanaka's model. To take the fiber orientation into account, several methodologies are tested. Eventually, we propose to use a function that is able to describe the shape of the orientation distribution and whose parameters are identified from the 2nd-rank orientation tensor. Predictions obtained in this way appear to be consistent with the measurements of Young's moduli and thermal expansion coefficients.
| Item Type: | PhD Thesis (PhD) |
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| Thesis Supervisor: | Regnier, Gilles |
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| Date: | March 2006 |
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| Board of examiners: | Doghri, I. and Vincent, M. and Dragon, A. and Regnier, Gilles and Gilormini, Pierre and Schmidt, F. and Rossignol, Jean-Michel |
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| Ecole Doctorale: | ED 432 ECOLE DOCTORALE SCIENCES DES METIERS DE L'INGENIEUR |
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| Discipline: | Mécanique et matériaux |
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| Collection (Fonds): | ENSAM |
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| Institution: | ENSAM |
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| Subjects: | 4. Materials Science, Mechanics and Mechanical Engineering |
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| Uncontrolled Keywords: | Injection, Composites, Short-fiber reinforced thermoplastics, Thermo-elastic properties, Fiber orientation, Homogenization, Mori-Tanaka’s model, Injection, Composites, Thermoplastiques chargés de fibres courtes, Propriétés thermo-élastiques, Orientation des fibres, Homogénéisation, modèle de Mori-Tanaka |
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