Pre-impregnated fibres

The resin is generally applied by an impregnation bath, which is mounted on the carriage. The reinforcement passes between bars in the resin bath which spreads the fibre and allows the resin to penetrate the fibre bundle. Alternatively pre-impregnated fibre may be used. 

Factory made cold-melt pre-impregnated fibre (prepreg) and compatible film adhesive which are simultaneously wrapped onto the bridge and cured under an elevated temperature (heat blanket) of 60°C for 16 hours or 80°C for 4 hours under a 1 bar pressure (Hollaway, 2008). 

This process has a number of advantages over the more conventional autoclave moulding using pre-impregnated carbon fibre ... 

One example of pre-impregnation is melt impregnation, in which roving is pultruded through a resin melt and over cylindrical pins. The pins are designed to spread the fibre bundle or tow, and to entrain a film of liquid resin which becomes drawn into the tow. Another approach is solvent impregnation, which can only be used with soluble thermoplastics. The... 

The properties of composite materials cannot be predicted adequately by considering the fibre and resin constituents one by one. An important mechanism of composite failure under stress is delamination caused by differences between the engineering properties of successive plies or layers. These differences arise from the fact that successive layers may have different fibre orientations [34] or, occasionally, different fibres. It is a feature of laminates made by stacking pre-impregnated layers of reinforcement and is not an issue with, for example, unidirectional pultrusions. The process of delamination has been reviewed by Davies [35]. The fabrication of three-dimensional composites is an important step towards reducing or eliminating unwanted delaminations. Such materials are at an advanced stage of development. 

It is possible to improve the distribution of fibres in the matrix material when the fibres or fibre sheets are mechanically pre-impregnated with the matrix. Such pre-impregnated material is classified as prepreg. In this... 

Pre-impregnated sheet materials called prepregs are available, where the carbon fibres are impregnafed with reactive resins, usually modified epoxy resins. These can be worked on, layed-up and moulded fo shape with heat applied to cure the resins. They are also available with glass fibre/phenol and aramid fibre/phenol combinations. 

Layers of fibre pre-impregnated with resin (prepreg) are applied to a mould and rolled. A rubber bag is placed over the lay-up and the air is removed by means of a vacuum pump. Generally the mould is then placed in an autoclave, which applies further pressure and temperature to cure the resin, or simply in an oven. 

Filament winding The application of a pre-impregnated continuous length of fibre around the outside of a mandrel to produce pipes, pressure vessels and similar articles, is also a form of contact moulding. As with pultrusion, continuous reinforcement is passed through a bath of activated thermosetting resin that is cross-linked by heat, in this case on the mandrel. 

In 2007 Boeing launched their Boeing 787 Dreamliner in which pre-impregnated carbon fibre is used for polymer-matrix composite structural components [10]. 

Fibres appropriate for civil engineering applications are available in three major formats continuous or chopped strands, woven or unwoven fabrics (sheets) and pre-impregnated forms. Commercially available fibres are produced in the form of spooled strands. 

Seismic retrofitting to columns uses filament winding of prepreg (pre impregnated) carbon fibres to produce a jacket which is then upgradable as described previously. 

Impact performance was measured on layered structures which were prepared by stacking pre-impregnated plies of carbon and HP-PE fibre woven fabric (Satin weave 8 H) together and curing them for 2 hours under combined vacuum- and pressure conditions in a hot press at 110°C. After curing samples were postcured for 12 hours at 110 C. All laminates were 4 plies thick (nominal thickness 1,5 mm) and within these 4 plies stacking sequences and HP-PE/carbon ratios were varied. The total volume fraction of fibre in the laminate was 70%. Plane samples of 60 mm x 60 mm were cut from these laminates with a bandsaw. 

Compared to other intermediate product forms such as pre-impregnated tows or powder impregnated fibre bundles, commingled yams are attractive because they possess high flexibility, thus allowing the processing of complex shapes (Svensson et al., 1998). 

An advanced form of this is based on biaxial thermoplastics in the form of fibres (PA, PBT, PET, PP/PPS, PEI, APC-2, or PSUl), with carbon, aramid, and glass pre-impregnated tape. The pre-preg is unidirectional and interlaced in a biaxial form in continuous lengths. The manufacturers claim that an unprecedented width (up to 3.04 m) is possible. 

A pre-impregnated (prepreg) laminate consists of a specially formulated pre-catalysed resin system, using machinery designed to ensure consistency the resin is combined with fibre or fabric reinforcement. 

The high technology thermoplastic aromatic polymers. In the mid-1980s ICI developed a new generation of thermoplastic aronratic polymers, in particnlar the amorphorrs polymer poly ether snlphone (PES) and the senri-crystalline polymer polyetheretherketone (PEEK) (Cogswell, 1989) they also developed the pre-impregnation of continnons fibres... 

Endolign - This is an implantable continuous carbon fibre composite which is used for the replacement of metals in high sustained or cyclic load applications. The ability to control fibre direction means that mechanical properties can be tailored for specific applications. It is supplied as a pre-impregnated tape or as rods that can be heat-formed through processes such a composite flow moulding. 

An alternative approach to building up components in which the fibres are aligned in various directions, which is often favoured with carbon fibres, is to produce a pre-impregnated material, known as a prepreg. Unidirectional fibres are spread out thinly and impregnated with a thermosetting resin which is partially cured or B-staged. The sheet or roll material (which is a fraction of a millimetre in thickness)... 

A process which involves winding fibres or tapes onto a mandrel - these are generally pre-impregnated with resin. 

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