Resin Infusion with reusable silicone bags
Resin infusion is the process whereby resin is drawn into a dry laminate whilst it is held under vacuum against a rigid mould by a sealed flexible membrane.
The most commonly used membranes consist of a disposable film (vacuum bag) and this film is sealed against the mould edges using a sealant tape.
Silicone can often be used to replace the disposable bag with a reusable and pre-shaped bag which includes an integral sealing system, thus providing very significant savings in application time and materials.
Resin Inlet and venting strategies can be highly adaptable and resin flow can be influenced and accelerated by the use of disposable ‘flow media’ positioned between the vacuum membrane and the laminate.
Resin infusion is particularly relevant when making large structures as tooling costs are relatively low when compared to RTM processes.
Unlike RTM, the ‘B’ surface finish of the resulting laminate is not controlled cosmetically but excellent laminate properties can be achieved.
Volatile emissions can also be dramatically reduced making resin infusion an excellent alternative to large-scale open moulding.
As the resin infusion process has become more widespread so the need to mechanise the handling mixing and delivery of the resin has become more important.
With the use of reusable silicone vacuum bags the drive to streamline the production process is gaining momentum.
The traditional technique of hand-mixing bulk resin becomes impractical and potentially risky when using the process on any significant scale.
Problems with mixing consistency, potential bulk-exotherm and high levels of waste can have a significant impact on the viability of the process.
A meter-mixing machine can be used to simply dispense mixed resin ‘on demand’ into a suitable container but our partners at Composite Integration have taken the technology a step further by pioneering the development of systems capable of injecting ‘directly’ into the infusion process.
Pressure sensors positioned strategically in the mould feedback to the injection machine and enable the process to be completely ‘closed’ with fully automatic quantity and flow-rate control.
The advantages of ‘directly injecting’ include:
- Process repeatability (system leads the operator through the various process stages)
- No bulk-exotherm risk (resin is mixed on-demand)
- No manual resin mixing (manual contact with liquid resin is avoided)
- Internal in-line mixing avoids air entrapment in resin
- Waste reduction (no need to fill bulk feed containers with potentially excess resin)
- Possibility to record process data