40207_22 - FIBER PLACEMENT Don 0. Evans 22 22.1...

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FIBER PLACEMENT 22 Don 0. Evans 22.1 INTRODUCTION When starting a course, the tows are Fiber placement is a unique process combining the differential tow payout capability of fila- ment winding and the compaction and cut-restart capabilities of automatic tape lay- ing. During the fiber placement process, individual prepreg fibers, called tows, are pulled off spools and fed through a fiber deliv- ery system into a fiber placement head (Fig. 22.1). Here they are collimated into a single fiber band and laminated onto a work surface which can be mounted between a headstock and tailstock. restarted and cogpacted onto a surface. As the course is being laid down, the processing head can cut or restart any of the individual tows. This permits the width of the band to be increased or decreased in increments equal to one tow width. Adjusting the band width avoids excessive gaps or overlaps between adjacent courses. At the end of the course, the remaining tows are cut and the head is posi- tioned to the beginning of the next course. During the placement of a course each tow is dispensed at its own speed, allowing each FiberPkementHead r Ti Restart Rollers Collimated Fiber Band Y Controlled Heat Fig. Fiber placement head. Handbook of Composites. Edited by S.T. Peters. Published in 1998 by Chapman & Hall, London. ISBN 0 412 54020 7
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Introduction 477 tow to independently conform to the surface of the part. For example, when the head lami- nates a curved path, the outer tows of the fiber band pull more length than the inner tows. A rolling compaction device, combined with heat for tack enhancement, laminates the tows onto the lay-up surface. This action of pressing the tows onto the work surface (or a previously laid ply) adheres the tows to the lay-up surface and removes trapped air, mini- mizing the need for vacuum debulking. Figure 22.2 is a diagram of a Cincinnati Milacron 'Viper' Fiber Placement System (FPS). This system has seven axes of motion and is CNC controlled. The machine consists of three position axes (carriage, tilt, crossfeed), three orientation axes (yaw, pitch, roll) and an axis to rotate the mandrel. All of these axes are necessary to make sure the processing head is normal to the surface while the machine is laminating tows. The machine also has 24 pro- grammable electronic bidirectional tensioners, which are mounted in a creel. These tensioners provide individual tow payout and maintain a precise tension. The fiber placement head is mounted on the end of the wrist. The head precisely dispenses, cuts, clamps and restarts individual prepreg tows. To increase productivity some machines are equipped with dual mandrel stations (Fig. 22.3). This setup allows two sets of lay-up tools to be placed on the machine, ensuring a constant supply of work for the head. During routine manual operations such as hand lay- ing small plies, inspecting plies, or vacuum debulking on one part set, the head simply shifts to the other mandrel and picks up the program where it left off.
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This note was uploaded on 03/16/2010 for the course MECHANICAL ME765401 taught by Professor Prof.sulis during the Spring '10 term at Institut Teknologi Bandung.

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40207_22 - FIBER PLACEMENT Don 0. Evans 22 22.1...

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