Vacuum-assisted moulding

A development of the matched-die moulding process is to vacuum assist the resin into the tool. Dry reinforcements are placed in an open tool. The layup is sealed by a flexible vacuum bag and vacuum is applied. The resin is forced under pressure into the... 

Figure 3.6 Vacuum-assisted resin transfer moulding (VARTM).

Abraham D, McIIhagger R. Vacuum assisted resin transfer moulding for high performance carbon fibre composites. In Proceedings of the 4th international conference on automated composites, ICAC95. Nottingham 1995. pp. 299—306. 

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 ... 

The vacuum assisted resin transfer moulding (VARTM) process is a variant of vacuum-infusion RTM in which one of the solid tool faces is replaced by a flexible polymeric film (Fig. 23.14). 

Vacuum infusion process (VIP), generally referred to as vacuum-assisted resin transfer moulding (VARTM), in which the resin is introduced into the mould and the preform at less than atmospheric pressure (i.e. a vacuum). 

On the other hand, if the process is force controlled, so that h is unknown at any instant, Eqs [11.1], [11.3], [11.7] and [11.8] are coupled. This is similar to the situation in resin infusion (RI) and the vacuum-assisted resin transfer moulding (VARTM) process. A convenient way to solve the system in this case is to use an iterative procedure, where h is first estimated, then adjusted until the calculated clamping force converges to the actual value. In the one-dimensional case, the problem can be reduced to a single ODE which can be solved numerically. ... 

Resin infusion (Rl) is also known as the vacuum assisted resin transfer moulding (VARTM) process, vacuum assisted resin infusion (VARI) and Seeman s composite resin infusion moulding process (SCRIMP). In this... 

Hsiao K-T, Devillard M, Advani SG. Simulation based flow distribution network optimization for vacuum assisted resin transfer moulding process. Modelling and Simulation in Materials, Science and Engineering, 2004 12 175-190. DOI 10.1088/0965-0393/12/3/S08. 

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... 

Another type of product is a preform in which the fibres, whether in the form of a mat, fabric or some other construction, are initially formed to a, possibly, complex shape and stabilized with a binder. The preform is placed in a mould and a thermosetting resin injected, sometimes with vacuum assistance, to produce a component (section 11.3). The advantage of this approach is the ability to maintain the fibres in position during a complex moulding operation, increased product quality and improved productivity. 

A variant of low-pressure moulding is catalysed resin injection into matched moulds in which the reinforcement has been preplaced prior to mould closure vacuum applied before resin injection assists mould filling. All these techniques depend on the easy flow of the prepolymer and good wetting of the reinforcement, but preclude the addition of much cheap particulate filler. 

The clamp is manufactured via Vacuum Bag Resin Infusion, a process that is similar to Vacuum Assisted Resin Transfer Moulding, at room temperature. Machining and drilling are required to form the necessary grooves that house the seals and the holes for the fasteners, respectively. Alternative manufacturing approaches may be used, such as wet lay-up and resin transfer moulding. A typical ProAssure Clamp is shown in Figure 12.2. 

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