Unidirectional reinforced tapes

Applications. Boron fibers are used as unidirectional reinforcement for epoxy composites in the form of preimpregnated tape. The material is used extensively, mostly in fixed and rotary wing military aircrafts for horizontal and vertical stabilizers, mdders, longerons, wing doublers, and rotors. They are also used in sporting goods. Another application is as reinforcement for metal matrix composites, in the form of an array of fibers pressed between metal foils, the metal being aluminum in most applications. 

Schledjewski, R. and LatriUe, M., Processing of unidirectional fiber reinforced tapes Fundamentals on the way to a process simulation tool (ProSim FRT) , Composites Science and Technology, 2003, 63, 2111. 

In principle, all fibres available for FRP can also be used as reinforcement in prepregs, the most common ones being carbon and glass fibres. Polymeric fibres made from aramid or polyethylene are also quite coimnon, as are inorganic basalt fibres, or natural fibres like hemp or flax. Often, the fibres are directly impregnated to make unidirectional (UD) tapes. Alternatively, they can first be transformed into fabric products, such as woven fabrics or non-crimp fabrics (NCF), and then impregnated to create multi-directional prepregs. 

As seen for unidirectionally reinforced composites, the bidirectionally reinforced composites based on PP (as reported by Alcock et al. [6]) or PET (as reported by Hine et al. [136]) possess much lower mechanical properties than PE-based systems. Alcock et al. reported the creation of PP tapes with a tensile stiffness of 15 GPa and composites based on woven tape fabrics with a tensile stiffness of 7.4 GPa [6]. 

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. 

An advanced reinforcements system identifies QBT. It is the name for a biaxial thermoplastic (PA, PBT, PET, PP/PPS, PEI, APC-2, Radel), carbon, aramid, and glass pre-impregnated tape. It is unidirectional, interlaced in biaxial form, in continuous lengths and very large width (up to 10 ft). It maintains and improved properties of unidirectional cross-ply laminates, giving the benefit of unidirectional tape in larger and more easily processed formats. It is claimed to be first real alternative to a woven composites compromise, with good drape. 

Hand lay-up Individual plies of reinforcement placed in open mould and impregnated with catalysed resin by hand tool, e.g. roller unidirectional tape can be used Large structures, e.g. boat hulls, chemical tanks... 

Films were produced for experimentation by melt (2) or solution (6) processes developed in our laboratory. The melt process is similar to commercial processes for producing composite parts from unidirectional pre-impregnated tape. Woven fabric reinforced composites are impregnated by submerging the fabric in an epoxy solution. Thus, the solution process which is primarily emphasized in this study provides additional information to characterize and compare matrices produced by the two processes. 

Thermoset or thermoplastic, fiber-reinforced unidirectional tape is laid automatically by a programmed dispensing machine to form a desired shape. A gantry system provides the necessary lay-down motions of the tape head, producing either flat or contoured surfaces. 

Circumferential Banding Tape. Each layer was banded with a unidirectional glass reinforced epoxy tape before application of the Kapton interlayer insulation. The purpose of the tape was to restrain radial conductor motion, and secondarily, to bridge between teeth tops. The tape used was 3M Company 4 cm wide. Scotch-ply (R) Type 1003. The first application of the tape was half-lapped and the next layer was butted, thus providing 3 layers of tape or approximately 0.76 mm of tape buildup. To cure the banding tape, the whole coil was placed in a forced air oven and heated to 423 K for 16 h. Four thermocouples were inserted in the various layers to different depths to make sure that the coil interior reached the required temperature. 

In addition to wet systems, where reinforcements are resin-coated during the process, more convenient prepregs are available that can be used for many applications. Suppliers assist in the selection of preimpregnated materials, which are available as unidirectional, woven, and nonwoven tape, tow, mat, and so forth. 

With respect to the research in this field, all-polypropylene (PP) composites have been extensively studied. Hine et al. investigated the influence of fabrication parameters that control the hot-compaction behavior of woven-oriented PP [23,24], The results indicated that molecular weight, crystallinity, reinforcement shape and the weave style are important for controlling the composites performance. Alcock et al. created unidirectional all-PP composite laminates from co-extruded three layer tape of PP (with a copolymer homopolymer copolymer structure) via filament winding [12]. The specific mechanical properties were comparable to those reported for a commercial unidirectional glass fiber reinforced PP. 

First and foremost, the very low density of SR-PP composites should be highlighted. The formation of cavities in the amorphous areas during the stretching of the original tapes causes the density to decrease (experimentally) to values as low as 0.77 g/cm in unidirectional composites [26,73]. Due to the micro-cavities, which are usually closed during hot-compaction [20], a density of 0.91 g/cm is usually achieved for self-reinforced fiber composites. This value equals approximately that of the original, unreinforced PP-material. 

The term PAEK composite generally means a continuous fibre reinforced material and mostly refers to continuous carbon fibre reinforced products. These can come as unidirectional tape or woven cloth which is then used to form melt-processed components. 

Tooling and the configuration of the reinforcement have a great influence on the curing process selected, and vice-versa. The choice between unidirectional tape and woven fabric frequently has been made on the basis of the greater strength and modulus attainable with the tape, particularly in applications which compression strength is important. There are other factors that should be included in the trade, as shown on Table 4.23. 

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