CAMX Demonstration: Aerospace Manufacturers Elevate Vacuum Infusion Process (VIP) with Process Materials from Aerovac
Composites One recently made its industry debut at JEC World in Paris, the leading international composites show. JEC showcases a full spectrum of processes, materials, and composite solutions to the global composites industry.
Applications and techniques for aerospace composites manufacturing
Prior to JEC World, technical support experts from Composites One demonstrated at CAMX 2021 the process of vacuum infusion for a carbon fiber UAV wing skin for a propeller-driven aircraft.
Technicians explained the importance of preparing the mold surface adequately to allow for the release of the part for a cosmetic finish and to ensure the tool is not damaged. In many aerospace applications, multiple coats of semi-permanent mold release are applied, which can create build-up on the mold and lead to a poor release or transfer, and subsequent coats wetting out on the mold. The demonstration featured a one-coat mold release from Composites One supplier, Chem Trend, as an alternative to semi-permanent mold release.
With the vacuum infusion process (VIP), materials are added to the mold in dry form. Once infused, the part achieves a similar fiber volume and void content as with prepreg or other composites manufacturing processes. To prepare the mold surface, dry carbon fiber reinforcement fabric is laid. Composites One supplier, Vector Ply, provides stitched non-crimped fabric of carbon fiber, aramid or e-glass. Eighteen oz. fabric with micromesh for vacuum infusion was used for the CAMX demonstration, as well as fusion consumables that allow for labor reduction when assembling vacuum and resin distribution manifolds.
The process materials used in the demonstration included Infuply flow media from Aerovac, a combination knitted woven mesh and perforated release film, offering energy efficiency with the applications of two layers at once. A durable 200g bagging film was used with performance capabilities up to 120 degrees Celsius/250 degrees Fahrenheit, ideal for the aero-composites application. Sealant tape was then used to seal the bag to the edges, with pleats added manually.
In the infusion process, the bag is ideally up to 30% larger than the part for sufficient slack to conform to the geometry of the part. Adding pleats helps take up slack and ensures the bag is sealed airtight.
Resin injection process
Under the bag, feed lines were set up with one main feed line connected to the resin pump. This allows operators to feed the entire part through one feed point, with branches extending from the line for an easily timed injection. A single injection port, versus a sequential feed, also minimizes hoses and other process materials needed, along with the opportunity for leaks, and can cut down labor involved with vacuum infusion.
The demonstration used an injection system for polyester and vinyl ester resins from Composites One supplier, Magnum Venus Products (MVP). The technicians preset the strokes of catalyzed resin to be injected into the tool. A vacuum pump from RTM North was used, with two reservoirs for a good initial drawdown of the part, and the vacuum pump connected to a resin catch pot. Once the bag begins to pull down from vacuum pull, operators check the perimeter for leaks and address any pockets of air while watching a gauge for the vacuum level. At this point in the process, a vacuum drop test can be performed to ensure optimal vacuum level and recirculation of materials to make sure resin is flowing well.
If you are implementing closed mold processes like vacuum infusion process, Composites One offers on-site training and assistance in your facility to apply composites manufacturing processes to wing skin or other aerospace composite parts. Our technical team helps manufacturers achieve controlled flow for full wet out and good surface cosmetics.
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