Resin Transfer Molding (RTM) is a versatile technique for the manufacturing of composite components in production series of 500-5000 units per year. In the RTM process, reinforcements (fabrics, rovings, or a preform) are positioned in a mold, and then resin is injected through vacuum or pressure (or a combination of both). In many cases, the mold is covered with a gelcoat prior to application of the reinforcements. Tooling is made from steel (durable mold for larger series, better surface quality), but may also be made from composites. Combinations of mold materials are also possible.
Compared to Hand Lay-up, Spray-up and Vacuum Infusion techniques, RTM is used for consistently making components in larger production series. Typically parts are smaller, which also make the investment in steel tooling feasible. An additional benefit compared to Hand Lay-up and Spray-up is the significant reduction in styrene emissions.
In comparison to SMC, the RTM process is typically slower (cycle times 3-10 min for RTM, 1-3 min for SMC), and creates more production and cut-off waste. At the same time RTM allows to better position the reinforcements in the mold (more strength and stiffness at critical spots), to obtain high fiber loading and higher mechanical properties as a result, and requires a lower tool investment.
Composite components made in RTM are used in a variety of end-use markets, with Transportation (small series passenger cars, truck components, vans, caravans, and special vehicles) being the most important one. More recently, RTM has been applied for making structural components in passenger cars, using a combination of resin with carbon fiber. These parts combine very high strength and stiffness in combination with very low weight, making them even suitable as chassis components.
Aliancys has multiple products available for RTM processes, sold under Atlac®, Palatal®, Synolite™, and Daron® brands. Depending on the required chemical resistance and mechanical properties, solutions are available in Vinyl Ester, Orthophthalic, Isophthalic and DCPD chemistries. Solutions are available both for use with glass and with carbon fiber reinforcements.