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Rapid Automated Induction Lamination (RAIL) of carbon fiber weave and thermoplastic film
2006 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

This work is a continuation of the RAIL - Rapid Automated Induction Lamination - process developed by S. Yarlagadda et al. at the Center for Composite Materials, University of Delaware, USA. The RAIL process was developed and optimized for laminating prepregs, i.e. preimpregnated carbon fibers that are oriented parallel to each other and then formed as a sheet 12” x 36”. These sheets are stacked so that there is always an angle between the fibers of two sheets that are in contact with each other. If the angle is zero degrees there will be no heat generated in the induction heating zone due to the fact that conductive loops are required for heating to occur. This project’s primary goal was to test an alternative combination of carbon fiber and thermoplastic polymer and run it in the existing RAIL machine. Carbon fiber weave would be stacked with thermoplastic film and the result would be a flexible and strong composite. Both raw materials could be delivered to the machine separately, on rolls, and the need for pre- impregnation would be eliminated. This would reduce the raw material cost compared to prepregs. A requirement was that the quality of the final composite had to be at least as good as the same composite manufactured in a hot press. The secondary goal was a continuation of the primary: it consisted of modifications of the RAIL process stages, allowing manufacture of non-flat laminates. For this purpose, aluminum molding dies were designed and manufactured and the process would then be a combination of lamination and a variant of pultrusion. The experiments that were carried out showed that it would be possible to replace prepregs with stacks of carbon fiber weave and thermoplastic film in the RAIL process. All experiments were done with Nylon™ as resin. Optical microscopy revealed that the process can heat the fiber weave enough to melt the resin and then evacuate the air in the stack at the consolidation stage. The cooling seemed sufficient as no voids were created. The preheat zone in the RAIL process was developed because impregnated carbon fibers were used at the time and it was necessary to melt the resin so that contact between the fibers could be achieved. Tests with carbon fiber weave and Nylon™ film indicated that the preheat station was not needed in order to reach the processing temperature because the majority of the heating occurs by induction heating inside each layer of the carbon fiber weave. However, preheating was still used for the evaluated laminates because the temperature distribution across the laminate turned out to be much easier to control with the preheating station active. The resulting laminate is very flexible and can easily be cut if desired. Molding dies were designed and manufactured. The purpose was to give the laminate a profile-type shape directly after the lamination stage. The cooling rollers would then have been replaced by the stationary molding dies.

Place, publisher, year, edition, pages
Keyword [en]
Technology, induction heating, induction, IH, lamination, composites, carbon fibers, carbon fibres, RAIL
Keyword [sv]
URN: urn:nbn:se:ltu:diva-45796ISRN: LTU-EX--06/093--SELocal ID: 375d197d-707c-44b2-8f61-5322dd11b007OAI: diva2:1019093
Subject / course
Student thesis, at least 30 credits
Educational program
Materials Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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