Prepreg Moulding

The advantage of this process is that the reinforcement (in the form of long fibres) is already impregnated with a partially cured resin. Either vacuum or light pressure (in an autoclave) is required to consolidate layers during curing. The cure schedule for optimum properties will have already been determined by the material supplier. 

There is a close analogy to press moulding of long fibres, in the sense that the materials are pre-selected, though the temperatures and pressures are lower. 

Prepreg materials are thin, typically 0.2 mm thick, so that many layers are required to obtain a reasonable thickness, which does permit layers to be orientated so as to obtain specified properties. Drape can be a problem because of the continuous nature of the fibre so care is required in laying up. 

The principal data from other chapters are listed in Table 11.15. 

The principal reasons for using prepreg moulding are listed in Table 11.16. 

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Prepreg moulding High-quality product, reproducibility, no need of impregnation, minimum material wastage High cost Epoxy, bismaleimides, polyimide... 

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

Manufacture was achieved by prepreg moulding followed by a post cure regime of 1 hour at 175°C, Aen 4 hours at 190°C. 

The first two materials are based on an unspecified epoxy resin, though the resin and size will be compatible. The second two composites are made with Stratyl 108, a polyester resin. The S-2 glass composite is an epoxy prepreg system. Manufacture was achieved by contact or prepreg moulding. 

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

Table 11.16 Principal considerations for using prepreg moulding...

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