IBEX 365 News
How to Apply Vacuum for Successful Infusions
From Airtech Advanced Materials Group
Resin infusion relies on differential pressure created by a vacuum bag to compress dry fabrics, transport the resin and infuse into the part. So vacuum distribution is vital. To infuse successfully, Airtech has a range of vacuum manifold products to distribute your vacuum before and during infusions.
The function of the vacuum manifold is to provide an open passage between the vacuum pump and the dry fabric lay-up. In addition, it provides the pressure differential required to push the resin into the dry fabric and achieve complete wet out. Typically, the vacuum manifold is positioned around the periphery of the fabric lay-up with at least a 25mm gap to provide a resin brake. The purpose of the resin brake is to slow the resin flow speed down. This will prevent resin from a completely saturated section of the laminate from flooding the vacuum manifold, before the entire infusion is complete.
A traditional, low-cost vacuum manifold construction is a PE Spiral Tube mounted on Airhold 10CBS Double Backed Tape. These products are placed on the flange of a tool and provide a non-crushable open path for the vacuum manifold. This spiral tube construction is covered in peel ply that is connected to the edge of the laminate to act as a resin brake and provide a vacuum link.
In order to speed up the lay-up of vacuum bagging consumables, Vac-Brake was developed. This is a combination vacuum manifold and resin brake for the periphery of resin infusion mouldings. Vac-Brake features a spiral tube sewn into a technical textile. Positioned around the edge of the part it distributes even vacuum and provides a resin brake preventing resin waste and choking of the vacuum manifold. Vac-Brake R is constructed using a breathable, self-releasing technical textile called PP200. This product can be placed up to or on top of the laminate as it is self-releasing. Vac-Brake C is a more economical version without self-release and can be placed on top of release film.
If a mould tool does not have a large flange for a resin brake and vacuum manifold Dahlvac MB80 is the perfect solution. This product is a combined resin brake and vacuum manifold that can be attached to the periphery of a mould using Airtac spray adhesive or Airhold 10CBS double-sided tape. It consists of an internal spiral tube that is wrapped in a layer of Dahltexx SP2. The spiral tube provides a good non-crushable path for airflow and the Dahltexx SP2 allows breathability while preventing resin from entering the vacuum channel due to its microporous properties. The need for a large flange is eliminated as the Dahltexx SP2 material will not allow resin to pass through into the spiral tube, whilst continuing to maintain a pressure differential, resulting in an even distribution of resin through the dry fabric.
Vacuum can be applied over the surface of a composite laminate using Dahlpac MC79. It is an easy to use strip material that will maintain vacuum with no resin bleed out and little part mark-off. Dahlpac MC79 is constructed with Dahltexx SP2 fabric which breathes efficiently and can control resin flow due to its microporous nature. Dahlpac MC79 ensures complete resin wet out and avoids dry patches by achieving efficient total air removal with vacuum distribution over the part surface. This allows for faster infusions, with multiple resin feeds, as there is no risk of dryness where resin flow fronts merge. For example, stringer profiles can be infused using Dahlpac MC79 as a vacuum manifold on top of them, with no dry patches.