Tow bundle

Tow Bundle of twisted or untwisted continuous fibers. A tow may contain tens or hundreds of thousands of individual filaments. 

Manufacturers of composite structures have traditionally used prepreg tape to manufacture structural components. Fibres are initially combined into unidirectional tows (bundles) of fibres combined into fabrics, e.g. by weaving or knitting. The vast majority of the tows employed in woven, braided or knitted reinforcements comprise low twist or untwisted continuous filament yams. Three-dimensional technical textiles can be produced by weaving [5], knitting [6] and braiding [7] or as non-crimp fabrics. 

Staple fibers are short fibers, ranging from less than an inch to a little less than a foot in length, depending on the application. Staple fibers are spun fibers that are produced in either of two somewhat different processes. In the long-spin traditional process, fiber is spun similarly to CF fibers, wound undrawn in a tow (bundle) in one step and then drawn (if desired), crimped (if desired), and cut in a second step. 

They are later processed into other formats in secondary operations. The size of the fibre tow bundle can range from 1000 filaments (IK) to more than 200K. Generally, commercial-grade fibres appropriate for civil engineering applications have 48K or larger filament counts. 

Alternatively, tows of fibers can be passed through a Hquid metal bath, where the individual fibers are wet by the molten metal, wiped of excess metal, and a composite wine is produced. A bundle of such wines can be consoHdated by extmsion to make a composite. Another pressureless Hquid metal infiltration process of making MMCs is the Prim ex process (Lanxide), which can be used with certain reactive metal alloys such as Al—Mg to iafiltrate ceramic preforms. For an Al—Mg alloy, the process takes place between 750—1000°C ia a nitrogen-rich atmosphere (2). Typical infiltration rates are less than 25 cm/h. 

Commercially, stabilization is accomplished by controlled heating in air at temperatures of 200—300°C. A variety of equipment has been proposed for continuous stabilization. One basic approach is to pass a fiber tow through heated chambers for sufficient time to oxidize the fiber. Both Mitsubishi and Toho patents (23,24) describe similar continuous processes wherein the fiber can pass through multiple ovens to increase temperature and reaction rate as the thermal stabiUty of the fiber is increased. Alternatively, patents have described processes where the fiber passes over hot roUs (25) and through fluidized beds (26) to provide more effective heat transfer and control of fiber bundle temperature. 

Tow A large bundle of fibres generally 10,000 or more, not twisted. 

Carbon fibers are the most rigid and strongest of commonly used reinforcements. They are produced by the pyrolysis (high-temperature decomposition) of natural and synthetic materials, such as rayon, polyacrylonitrile (PAN), and pitch (the tacky residue left from the distillation of petroleum or coal tar). Carbon fibers are commercially available in a variety of formats, including single strands and bundles (known as tows). They are midway in density between glass and polymer fibers and are the most expensive of commonly used reinforcements. 

Bundles of yarns from multiple spinnerets are referred to as tow. If the tow is subsequently cut into short specified lengths, it is referred to as staple tow, and the product is staple fiber. Depending on the man-made fiber producer s production equipment, one, two, or all three of the steps just discussed may be executed in either a batchwise or continuous manner. 

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