As an extension of our Resin Transfer Molding expertise, EDO offers our customers the capability to perform Vacuum Assisted Resin Transfer Molding (VaRTM) for large composite structures.

Structural aerospace parts are Vacuum Assisted Resin Transfer Molded using epoxy, BMI and cyanate ester resins. Fiber forms used include braided, woven, unidirectional and MDWK fabrics made from carbon, Kevlar, Quartz, glass and polyester fiber.

VaRTM is a process wherein liquid resin is transferred into a dry fiber preform located in a mold cavity that has only a single sided tool surface using vacuum only. The VaRTM process offers several engineering advantages for certain classes of parts.

VaRTM parts are formed in an open cavity mold, so not all surfaces are molded to the tool. The opposite side to the tool surface is primarily a vacuum bag surface comprised of transfer media, peel ply fabric, bleeder/breather media, and sealant tape. The single sided tools can be typically CNC machined to high tolerances, so the molded surfaces can be complex in shape and very precise. This is very important for many large components that require control of dimensions, tolerances on only one surface and where surface finish is important. With complex geometries, there are techniques such as caul plates for simultaneously applying vacuum bag pressure (typically 15 PSI) to complex surfaces of different orientation. Caul plates used in the VaRTM process are mainly to control thickness critical areas on the vacuum bag surface of the laminate, but cannot achieve as high a tolerance as RTM using matched metal tools.

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