Fibre-resin preform mouldings

In Resin Transfer Moulding preformed Carbon fibre and fabrics are placed in a mould along with the other components required to make the product. The mould is closed and premixed epoxy resin is injected into the fibrous mat. 

Resin transfer moulding (RTM) As above, but long fibre reinforcement preform cut to shape and placed in cavity instead of using premixed short fibres. One half of mould cavity can be flexible Large, complex shapes for automotive and aerospace use. Relatively fast cycles... 

A further development is resin transfer moulding (RTM), in which long fibre reinforcement fabrics are cut to shape as preforms and placed in the mould cavity, before the resin is injected. This is potentially a slow process and one alternative is for the preforms to be made rapidly by spraying short fibres onto a suitably shaped pattern coated with an adhesive or binder. 

Resin transfer moulding (RTM) is a low-pressure variation of transfer moulding where, instead of granules or preforms, a pre-mixed resin and catalyst (hardener) is injected into a closed mould containing dry glass, carbon or aramid fibre reinforcement. When the resin has cooled, the mould is opened and the composite part ejected. The resins used include polyester, vinylester, epoxies, phenolics and methyl methacrylate combined with pigments and fillers. Applications include small complex aircraft and automotive components as well as automotive body parts, baths and containers. 

Natural fibre composites are prepared using various composites manufacturing methods such as compression moulding, injection moulding, Resin transfer moulding (RTM) and vacuum bagging. The preforms are mostly fibres, fabrics or non-... 

Resin infusion technology is a process using a dry fibre laminate preform. A dry stack of fabric material is placed into a mould tool the fabric is sometimes... 

New glass fibre-reinforcement products for u.se in fibre-directed preform processes are another focus of development, designed specifically for liquid composite moulding applications such as resin transfer moulding with thermoset polyesters. 

In resin transfer moulding, the resin is injected into a mould containing layers of fibres or a preform at low pressure. The process cycle time is less than 3 minutes, and the fibre content of the composite product is up to 50%. The advantages of the process are design flexibility, ability to manufacture larger structures, low cost (thanks to the low pressures involved) and rapid manufacture. As with sheet moulding, resin transfer moulding is widely used in the automotive industry to manufacture a variety of parts for cars and other vehicles. 

RFI In this process, instead of injecting the film into the mould, sheets of resin are produced as thin films and placed on the bottom or top or both of the preform. Tool inserts are placed around the preform and the assembly placed in vacuum bag. When the tool is heated and pressurised, the resin film or films melt, flow into the preform and are cured. Advantages include higher fibre volume fractions and less expensive moulds. 

CIRTM This process allows two or more resins to be simultaneously injected into the mould. Advantages include the ability to create multi-layer and multi-resin structures. CRTM Also known as injection compression moulding, the process involves a gap between the mould surface and the fibre perform (Figure 3.10). Resin is injected into the gap and the mould closed to compress the resin into the fibre preform. This reduces the injection pressure and fill time required in RTM. 

In the Usui process for producing tapered pipes, the glass fibre reinforcement is wound round a tapered mandrel to make a preform. This is inserted into the mould in the centrifugal machine and the mandrel removed. Resin is poured in and the mold tilted to a pre-determined angle and then rotated until the resin has cured. 

High performance composites for this industry must have continuous reinforcement. This contrasts with the chopped fibres used in reinforced RIM (known as RRIM) [1], where short fibres are injected into the moulding via a slurry in one (or both) of the reactant streams. The use of a continuous reinforcement necessitates the placement of the reinforcing package (preform) in the mould prior to dispensing the epoxy resin system. This... 

The CRTM process is described schematically in Fig. 11.1. The filling stage comprises a combination of injection and compression driven flows. Unlike RTM, the mould is not completely closed prior to the initiation of filling. The mould is closed to some predetermined position, which results in lower overall fibre volume fraction, and hence a lower global resin flow resistance offered by the preform. It is also possible to leave a small empty cavity on... 

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