Moulding of Prepregs

Non-porous Teflon Caul plate Non porous Teflon 

Bleeder Porous Teflon Laminate Porous Teflon Bleeder 

Non-porous Teflon Tool plate Bagging film 

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Up to 5 2-10 Mass production Hot compression moulding of prepregs Car body elements... 

The following period between 1975 and 1985 was characterized by activities related to the development of prepreg systems for low pressure autoclave moulding, i.e. modification of the resin chemistries to achieve flow, tack and non-volatile cure. These requirements were dictated by the industry to meet the processing techniques already in place for epoxy and polyester resins. 

The mould is cleaned and a release agent or release film is applied. The backing film is removed from the prepreg surface and successive layers of prepreg are placed on the mould and rolled to conform to the mould surface. The layers are applied in a predetermined order and angle to achieve the laminate properties required. 

A solid isophthalic alkyd for the manufacture of prepreg moulding compounds. 

Figure 10.23 Tensile fatigue of prepreg moulded laminates with different types of reinforcement (Harris ef a/.).

Autoclave moulding is typically used in the aerospace industry for the production of high-value composites from prepregs. The laminate, which is covered on both sides by a fine polyester cloth peel-ply (for enhancing the surface effect), is built up on the mould surface. The top surface of the laminate is covered by a porous release film and bleeder cloth. The whole assembly is then covered with a non-porous membrane, which is sealed to the mould, and then placed inside an autoclave as shown in Figure 6.19. 

The use of these sensors is not restricted to high-performance composites, but can be extended to on-line monitoring of resin-transfer moulding (McIUiagger et al, 2000) and glass-polyester prepreg composite cure (Kim and Lee, 2002). 

Finally, the prepreg were stacked unidirectionally (0°) and moulded into coupons of 3 mm thick by 6 mm long by compression moulding at 200°C for 15 mins and then quenching under pressure. 

Scott and Heath (1992) [11] have reported that cost savings ranging from 25% to 40% are possible with liquid moulding raw materials when compared to prepreg. This is substantial as up to 50% of an autoclave component cost can be associated with the raw materials. 

In contrast to the planar reinforcement, the spatial reinforcement structures were produced in a discontinuous two-stage production process. In a first step, the fabric was coated with thermoset epoxy resin which remains in a so called and still shapeable b-stage . Afterwards, the prepreg-fabric was shaped with two moulds as shown in Fig. 6 (left). The moulds were placed in an oven and the fabrics were cured for 20 min at a temperature of about 180 C, Fig. 6 (right), resulting in an inherently stable reinforcement structure. 

As described in chapter 3.1 1ST and ITA already tested alternative ways to bring the B-staged prepreg inside of the concrete into the C-stage (Fig. 7). Thus, there is no further need to use a mould or autoclave process at all. This saves expenses. UV-, microwave or heat-curing systems are not favored by ISF and ITA, because cost intensive equipment would be needed as well as workers who have to deal with it on the construction side. 

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. 

The fibres conform to the mould surface by virtue of the winding tension. However, on a frictionless surface the fibres will take the shortest route between two points on the surface (this is the geodesic path). Therefore it is necessary either to wind a geodesic path or to generate sufficient frictional force to keep the fibres in the chosen path (by using a tacky resin or tacky prepreg). 

Reinforcement fibres—Sampling plans applicable to received batches Plastics—Prepregs—Definitions of terms and symbols for designations Textile glass reinforced plastics—Sheet moulding compound (SMC)—Basis for a... 

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