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Chouffart Q.,University of Liege | Simon P.,3B The Fibreglass Company | Terrapon V.E.,University of Liege
Journal of Materials Processing Technology | Year: 2016

The manufacturing process of glass fibers used for the reinforcement of composite materials consists in drawing a free jet of a molten glass at high temperature into fibers using a winder. This process is sensitive to numerous disturbances that can cause the fiber to break during the drawing process, and thus reduce the process efficiency. The underlying physics of the forming of a single fiber is investigated here through numerical simulations, and results are validated with measurements obtained on a dedicated experimental unit. Both a two-dimensional axisymmetric and a simplified one-dimensional model are used to simulate the high-temperature region before glass transition. The influence of key parameters and physical mechanisms on the internal stress is investigated through a sensitivity analysis. The simplified model is then used to identify the optimal operating window and to assess the impact of temperature inhomogeneities at the bushing plate. Results show that the initial region close to the tip is critical, and that a low cooling rate reduces the stress. Operating at high tip temperature, large drawing velocity and small tip radius is then found to be the best strategy to minimize the stress. Finally, it is shown that the heat pattern of the bushing plate is one of the most important causes for disturbance in the process. © 2015 Elsevier B.V. All rights reserved. Source


Chouffart Q.,University of Liege | Simon P.,3B The Fibreglass Company | Terrapon V.E.,University of Liege
Computational Methods for Coupled Problems in Science and Engineering V - A Conference Celebrating the 60th Birthday of Eugenio Onate, COUPLED PROBLEMS 2013 | Year: 2013

The physics of glass fiber drawing is studied through numerical simulations and experimental measurements, with a focus on the fluid region, from the hole tip at the bushing plate to the glass transition point. The influence of the different heat transfer mechanisms is investigated to understand their respective impact on fiberization, such as fiber radius attenuation and internal stresses. Numerical predictions are then compared to experimental data measurements obtained from a dedicated fiberization unit. Numerical and experimental results show a good agreement. In particular, it is found that the ambient air temperature and the radiation have an important impact on the fiber cooling rate. Moreover, for a prescribed fiber diameter, internal stresses are lower when operating at a higher temperature. Source


Chouffart Q.,University of Liege | Simon P.,3B The Fibreglass Company | Terrapon V.E.,University of Liege
Proceedings of the 15th International Heat Transfer Conference, IHTC 2014 | Year: 2014

The manufacturing process of glass fibers used for the reinforcement of composite material consists in drawing a glass melt at high temperature through an array of thousands of small orifices (i.e., the bushing plate) into fibers using a winder. This process is sensitive to numerous disturbances that can cause a fiber to break during the drawing process. This paper analyzes how the stress in the fiber depends on the controlling parameters of the process. The approach relies on numerical simulations and sensitivity analysis. Both a semi-analytical one-dimensional model and a more complex two-dimensional axisymmetric model are used. It is first found that radial variations across the fiber are small compared to changes in the axial direction and that the onedimensional approximation is accurate enough to describe the major trends in the process. Sensitivity analyses on some physical parameters controlling the heat transfers and on process parameters are then performed to identify strategies to reduce the axial stress. In particular, it is shown that, for a given fiber diameter, the stress is minimized if the glass melt temperature and the drawing velocity are increased. This approach is then applied to quantify the effect of inhomogeneous heat patterns on a bushing plate with a large number of fibers. Source


Veit U.,Friedrich - Schiller University of Jena | Houet Y.,3B The Fibreglass Company | Laurent D.,3B The Fibreglass Company | Russel C.,Friedrich - Schiller University of Jena
Thermochimica Acta | Year: 2015

The liquidus temperatures (TL) of good glass forming systems within the CaO-SiO2-MgO-Al2O3 system (CMAS) were evaluated. The determination of TL via differential thermal analysis (DTA) was studied in terms of reproducibility and was compared with results from the gradient furnace method. Seventeen different glass compositions within the CaO-SiO2-MgO-Al2O3 system were melted from technical raw materials. Since those glasses are reluctant to crystallize, a prior heat treatment was necessary to induce crystallization. The onset and the endpoint of the melting peaks of pre-crystallized materials were measured with a heating rate of 2 K/min and compared with the liquidus temperatures obtained by the gradient furnace method (following the ASTM standard procedure C 829-81 [1]). The endpoint temperatures of the melting peaks were closest to the results determined via the ASTM procedure. Most endpoint results via DTA differ by not more than 10 K compared to the liquidus temperatures. Because of the simultaneous crystallization pretreatment of many different compositions, the small amount of glass needed, and the speed of the DTA, this technique may be a valuable option to estimate the liquidus temperature of complex multicomponent glasses. © 2015 Published by Elsevier B.V. Source

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