Pressure bag moulding

Variations on this basic process are (i) vacuum bag moulding and (ii) pressure bag moulding. In the former process a flexible bag (frequently rubber) is clamped over the lay-up in the mould and a vacuum is applied between the moulding and the bag. This sucks the bag on to the moulding to consolidate the layers of reinforcement and resin. It also squeezes out trapped air and excess resin. The latter process is similar in principle except that pressure is applied above the bag instead of a vacuum below it. The techniques are illustrated in Fig. 4.67(b) and (c). 

Prepreg draping and consolidation by vacuum or pressure bag moulding, autoclave... 

Figure 5.25. Principle of pressure bag moulding after draping...

Plymol—A variation of the pressure bag moulding process, used to produce cylinders. 

Pressure Bag Moulding—A similar process to vacuum bag moulding, with pressure being applied to a rubber bag to aid consolidation of a laminate. 

Bag moulding processes use pressure applied to uncured resins on the mould in order to compact the laminates and to drive out volatiles. It can be in two different forms vacuum bag or pressure bag moulding. Either of these can be used to supplement curing in the lay-up or spray-up processes. 

In pressure bag moulding, a positive air pressure (of several atmospheres) is used to inflate an elastomeric bag against the part while curing proceeds, which is mostly used for complex hollow shaped parts. Heat is often used to accelerate curing (Figure 9.7b). 

The Manual processes cover methods such as hand lay-up, spray-up, pressure bag and autoclave moulding. 

This process (Figure 5.25) resembles vacuum bag moulding but the vacuum is replaced by pressure. After the composite has been manufactured onto its mould ... 

Autoclave Moulding—A process similar to the pressure bag technique. The lay-up is covered by a pressure bag, and the entire assembly is placed in an autoclave capable of providing heat and pressure for curing the part. The pressure bag is normally vented to the outside. 

Vacuum Bag Moulding—A process in which the lay-up is cured under pressure generated by drawing a vacuum in the space between the lay-up and a flexible sheet placed over it and sealed at the edges. 

Contact Filament Pressure bag Pultrusion Matched-die Continuous moulding winding moulding moulding laminating... 

Autoclave moulding is a modification of the pressure bag method. It is used to produce high quality composites, (i.e., for aerospace applications), where high pressures (up to 0.6 MPa) and high temperatures (up to 700 °C) are used. An autoclave is a pressure vessel inside which the curing reaction occurs. With this process, it is possible to produce composite structures with up to 70 wt% GF reinforcements [5]. However, the autoclave process is rather costly. 

An amine accelerated, short geltime orthophthallc suitable for RTM, cold-press moulding and vacuum/pressure bag. 

A preaccelerated, medium viscosity orthophthalic resin suitable for cold-press moulding, filament winding, vacuum/pressure bag and continuous lamination. 

Pressure bag compacting compacting reinforced plastics moulding by applying air pressure inside a heated vessel, as opposed to vacuum bag compacting (qv). 

The pieces of cloth are then plied up and moulded at about 170°C for 30-60 minutes. Whilst flat sheets are moulded in a press at about lOOOlbf/in (7 MPa) pressure, complex shapes may be moulded by rubber bag or similar techniques at much lower pressures ( 15 Ibf/in ) (0.1 MPa) if the correct choice of resin is made. A number of curing catalysts have been used, including triethanolamine, zinc octoate and dibutyl tin diacetate. The laminates are then given a further prolonged curing period in order to develop the most desirable properties. 

Once the component is laid up on the mould, it is enclosed in a flexible bag tailored approximately to the desired shape and the assembly is enclosed usually in an autoclave, a pressure vessel designed to contain a gas at pressures generally up to 1.5 MPa and fitted with a means of raising the internal temperature to that required to cure the resin. The flexible bag is first evacuated, thereby removing trapped air and organic vapours from the composite, after which the chamber is pressurised to provide additional consolidation during cure. The process produces structures of low... 

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... 

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