Composites Prepreg moulding

The polymer chosen in the UK for preliminary investigations was the PES, due to its ease of manufacture, its low out-gassing in space and light weight, Hollaway and Thome (1987). Prepreg sheets of the polyethersul-phone/carbon fibre (PES/CF) composite were moulded by the technique of film-stacking technology. 

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. 

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). 

Vacuum bag moulding for retrofitting is a semi-automatic resin infusion under flexible tooling (RIFT) technique, which allows production of quality composites. In the RIFT process, dry GF are pre-formed in a mould and are taken to the side and attached to the structure. A resin supply is then channelled to the prepreg, and both are enveloped in a vacuum bag. The flow of resin into dry GF (preform) develops the composite material and the adhesive bond between composite and structure as well. 

A rather common application of fibre reinforced polymers is car repair. This poor mans technology is translated to the "high tech" area. The most important difference is found in the addition of the word "advanced". For also in the aircraft industry composites is a sticky business. Prepregs are draped in moulds by hand, moreover, they are cured in expensive autoclaves. 

The mechanical properties of FRP composites are dependent upon the ratio of fibre and matrix material, the mechanical properties of the constituent materials, the fibre orientation in the matrix, and ultimately the processing and methods of fabrication, which are the subject of Part II. Chapters discuss prepreg processing, liquid composite moulding (LCM), filament winding processes and pultrusion of advanced fibre-reinforced polymer (FRP) composites. 

LCP/carbon-fibre composites have been developed and are used as secondary composites within the aerospace industry. LCP matrices offer low viscosity for the impregnation of the fibres, and excellent chemical resistance. Impregnation is achieved in a cross-head die, after which the composite panels are prepared by compression moulding the stacked prepreg sheets. 

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