Unidirectional tape

For simplicity, it will be assumed that the stmcture consists of laminates made with unidirectional tape plies and linear stress—strain response. The equations derived are, in general, valid for other material forms such as fabrics, with some differences that will be pointed out in subsequent sections. 

In practice, a general rule of thumb for scarfing is to remove 12.7 mm per ply. Ply thickness varies depending on the materials used in the original structure, but for carbon fibre unidirectional tape, it can be as thin as 0.127 mm. Clearly a scarf repair on a structure of 6.35 mm thickness (50 plies thick) would approximately translate to a scarf of 635 mm. 

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. 

The systems can include many options surfiice veil, chopped liners, sprayed resin systems, hoop winding strands, helical winding strands, resin bath, unidirectional tape, woven roving tape, pigmented resin surfaces, wax-resin surfaces, gel coats, BPO catalyst, epoxy resins, vinyl ester resins, filled resin systems, abrasive resin systems, polyester foam, syntactic foam, and charting film. 

Distance between adjacent plies in lay-up of unidirectional tape materials. 

Unidirectional tapes consisting of flat bundles of filaments already impregnated with catalysed resin can be used to increase stiffness and strength in specific places, and whole parts can be made from tape, applied under computer control. 

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... 

Graphite fibers are available to the user in a variety of forms continuous filament for filament winding, braiding, or pultrusion chopped fiber for injection or compression molding impregnated woven fabrics and unidirectional tapes for lamination. 

S-glass - unidirectional tape/epoxy Stiffer and stronger than E-glass for more critical applications. 

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. 

Overall, the material maintains and improves the properties of unidirectional cross-ply laminates, giving the benefit of unidirectional tape in larger and more easily processed formats. With very good drape characteristics, it is claimed to be the first real alternative to the compromise often necessary with woven composites. 

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. 

Commercial RP compounds are available in several forms pellets for injection molding or extrusion, unidirectional tape for filament winding and similar applications, sheets for stamping and compression molding, bulk compounds for compression molding, and so on. There are RTP... 

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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