Vacuum-assist resin injection

Liquid Composite Molding (LCM) is the common name for several similar processes for the manufacturing of polymeric fiber reinforced composites. Widely used processes that belong to this class are Resin Transfer Molding (RTM), Vacuum-Assisted Resin Injection (VARI), and Structural-Reaction Injection Molding (S-RIM). 

A widely used method of laminate construction is by the contact moulding process or hand lay-up . In this, a layer of catalysed unreinforced resin, known as the gelcoat , is brushed or sprayed onto the mould and allowed to cure and then layers of reinforcing-fibre impregnated with resin are built up behind (Fig. 6.3). Variations of this include resin injection and vacuum-assisted resin injection in closed moulds. After removal of the cured moulding from the mould, the gelcoat forms the outer skin and as such performs the two functions of decoration and protection ... 

Lotus, producers of composite cars since 1957, took a big step forward in 1974 with its new Elite (see Fig. 5.2). This was manufactured by the new VARI process (Vacuum Assisted Resin Injection), in which the two halves of the body are moulded in matched tools, and subsequently bonded together (see Fig. 5.3). The only chassis is a backbone top-hat section in steel otherwise the stability of the body is ensured by integral foam beams (see Fig. 5.4). These foam beams are used to locate and support uni-directional glass rovings, before the polyester resin is injected. The result is an extremely strong body, of which the present Esprit is the latest example. The Lotus system is extremely effective, but no claims are made that it will ever meet the cost and production needs of the mass market. The De Lorean... 

In the vacuum injection process (Vacuum Assisted Resin Injection [VARlj), which is the most simple resin injection process, molds with a fixed and a flexible mold half and molds with two fixed mold halves are used (Figure 1.227). The textile semifinished part is inserted into the cavity, the mold is closed, and a vacuum is applied. The vacuum ensures that the mold stays closed and the reinforced structure is compacted. After opening the inlet, the structure is impregnated by infusing the matrix into the fiber material. After curing, the finished component can be removed from the mold. 

Vacuum assisted resin injection additional vacuum can be used in mold cavity to assist resin filling of fiber preforms. 

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