Vacuum consolidation

Table 5.6 Dimensions of typical disposable vacuum consolidation materials.

Polyurethane board can include a low density foam block for applications from styling models to cutter path verification, and styling. Low density master models from which vacuum-consolidated RP tools and components can be produced. 

A porous release fabric is applied to the lay up to allow the passage of air and excess resin. This is followed by bleeder/breather layers which allow any air to be drawn from the laminate when the vacuum is applied. A vacuum bag is then placed over the laminate, sealed down and the vacuum is applied. The curing cycle now starts either in an oven or in an autoclave which applies both heat and pressure (typically 180°C and 10-20 bar). The action of the pressure from the autoclave or vacuum consolidates the laminate and the individual layers become fused. 

Hansen PM (1997) An investigation into vacuum consolidation as a means of production of large automotive parts. In Backlund J, Zenkert D, Astrom BT (eds) Composites and sandwich stractures proceedings NESCO II, Stockholm Sweden. EMAS, Cradley Heath, 401... 

In section 9.1 various solutions are discussed to make use of these materials and to improve their quality (ripening, use of additives, surcharge, vacuum consolidation, vertical drains, and sandwich structures). In view of the increasing environmental awareness and sand shortage in some regions, the (re-)use of silt and clays as fill material is becoming ever more important. 

Alternatively the strength of soft clay or silt can be improved by using consolidation techniques such as surcharging, vacuum consolidation, etc.. These techniques can be applied above and below the waterline. 

In some cases, the application of surcharge might be impossible for stability reasons or because of a shortage of suitable surcharge material. In such cases the use of vacuum consolidation techniques to improve the shear strength of the cohesive soil might be a suitable alternative. Reference is made to the case study on the use of alternative material in Bremenhaven, see box below. 

The basic working principles of a vacuum consolidation system are sketched in Figure 9.5. 

Figure 9.5 Sketch working principle vacuum consolidation (Menard).

This project demonstrates that dredged sludge can successfully be used as a structural fill provided that the problems associated with its typical properties are addressed adequately. The use of the vacuum consolidation system to increase the shear strength of the sludge has played a key role during... 

In the case of vacuum consolidation using PVDs, there may be a situation in which a soil layer adjacent to the PVDs becomes unsaturated. Consolidation theory under this kind of situation may need to be developed. 

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