Introduction of RTM molding process and classification
1. RTM molding process and classification
RTM refers to a process technology in which a low-viscosity resin flows in a closed mold, infiltrates the reinforcing material, and solidifies and forms. It belongs to the liquid forming or structural liquid forming technology category of composite materials. The specific method is to put reasonably designed, cut or mechanized pre-formed reinforcing materials in the designed mold in advance. The mold needs to be sealed and tightened around the periphery to ensure smooth flow of the resin; after the mold is closed, a certain amount of resin is injected. After the resin is cured, the mold can be demolded to obtain the desired product.
SMC, BMC molding, injection molding, RTM, and VEC technologies are all closed-mold molding processes. Due to the formulation of environmental laws and the improvement of product requirements, open-mold composite materials are increasingly restricted, which has prompted the application of closed-mold molding technology, especially in recent years, has promoted the innovation and development of RTM technology.
2. Types of RTMs
The RTM process started in the 1950s. At present, the RTM molding process has been widely used in construction, transportation, telecommunications, health, aerospace and other fields. Several RTM technologies are described below.
01. RTM, resin transfer molding. This technology is derived from polyurethane technology, the mold is closed during molding, and resin is injected into the preform with a low glass fiber content, about 20-45%.
02. VARIT, vacuum-assisted resin transfer injection molding. The technology utilizes a vacuum to draw resin into the preform, and it can also be pressed into the resin, with a vacuum of about 10-28 inches of mercury.
03. VARTM, vacuum-assisted resin transfer injection molding. Products generally have fewer pores, and the glass fiber content can be increased.
04. VRTM, vacuum resin transfer molding.
05. VIP, vacuum impregnation method.
06, VIMP, variable impregnation plastic method. The resin is moved by means of vacuum or its own weight, compacting the impregnation.
07. TERTM, thermal expansion RTM. A core material is inserted into the preform, the resin is impregnated and the mold and molded part are heated. The core material expands when heated, compacting the layup. Using this compaction, combined with surface compression molding.
08. RARTM, rubber-assisted RTM. In the TERTM method, the core material is not used but rubber is used instead. The rubber mold compresses the molded product, so that the pores are greatly reduced, and the glass fiber content can be as high as 60-70%.
09. RIRM, resin injection cycle molding. A combination of vacuum and pressure alternately injects resin into multiple molds, circulating the resin until the preform is fully saturated.
10. CIRTM, Co-Injection RTM. Co-injection RTM, which can inject several different resins, can also use several preforms, can utilize vacuum bags and flexible surface molds.
11. RLI, resin liquid impregnation (infiltration) stains. The resin is injected into the lower mold, the preform is put into the upper mold, and the upper mold is heated and molded with the molding pressure of the autoclave. Heating reduces the viscosity of the resin, provides good fluidity, and facilitates penetration.
12. SCRIMPTM Seaman Composites resin impregnation molding method. apply for patent. The resin is impregnated under pressure by using a vacuum bag, which has a fast impregnation speed and a wide area. The resin can also be fully impregnated in the thickness direction of the preform, and vacuum bags and soft-faced molds must be used.
13. RTM, resin transfer molding. This technology is derived from polyurethane technology, the mold is closed during molding, and resin is injected into the preform with a low glass fiber content, about 20-45%.
14. The core technology of VECTM virtual design composite material VEC is the patented "floating mold" idea. A composite pair of molds is mounted between two liquid-filled steel pressure vessels, and the molds form a seal along the entire length of the vessel, which is filled with a compressible thermally conductive liquid, usually water.
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