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Resin permeation molding process of composite material

Sep 18, 2017

With the development of the industry put forward higher demand to the production speed, only rely on handlay up traditional has been difficult to meet the increasing market demand, therefore, the processing technology of automation is an inevitable trend to conform to this trend.

The most common automated forming process is the resin transfer molding process (-ResinTransferMolding), sometimes referred to as liquid forming (LiquidMolding). Resin transfer molding forming process is a very simple principle: it is the first in the metal or composite material in the mold is closed on reinforcing the pre molding material body (preform), and then the resin and catalyst in a certain proportion of measurement and mixed thoroughly, then used injection equipment through the injection port (injectionports) by pressure the resin is injected into a mold, in accordance with the pre designed path to enhance the infiltration process materials. Resin transfer molding requires extremely low viscosity resins, especially when the preform is thicker, a better resin fluidity ensures a more timely and adequate wetting effect. If necessary, the mold and the resin can be heated, but the curing process without using autoclave. However, some of the products used for high temperature are usually subjected to post - cure (postcure) after mold release. Most applications use two-component epoxy resin formulations (two-partepoxyformulation): bismaleimide (Bismaleimideresin) and polyimide resin (polyimideresin). The formulation of components is not too early, usually before injection.

Lightweight resin transfer molding (Light) is a low cost molding process developed in recent years. It is a variant process of resin transfer molding. All the characteristics of light resin transfer molding process has not only, also reduced the requirements of molding process on a series of indicators such as injection pressure, vacuum coupling (coupledwithvacuum), and die cost and rigidity index.

Resin transfer molding process has many remarkable advantages. In general, the molding and resin materials used in the resin transfer molding process are cheaper than prepreg and can be stored at room temperature. With this process, a thicker net forming part can be produced, and many subsequent machining procedures can be removed. The process can also help to produce complex parts with precise dimensions and exquisite surface workmanship.  Another feature of the resin transfer molding process is that it allows the filling of core molding material into the preform prior to die closing to avoid extrusion of the preform during the die closing process. The core mold occupies a low proportion of the entire preform, approximately between 0-2%. In short, the resin transfer molding process can be used as an efficient reproducible automated manufacturing process to greatly reduce the processing time, the traditional hand lay up a few days to shorten the time for a few hours or even minutes.

Different from the resin transfer molding process (pre mixing resin and catalyst into the mold sequence, the reaction injection molding process (RIM) principle is the rapid curing resin and catalyst respectively into the mold. The mixing and chemical reactions are carried out in the mold, not in the mixing head (dispensinghead). Many car manufacturers use structure reaction injection molding (structuralRIM-SRIM) was prepared and the combination of rapid pre molding methods to manufacture automotive structural parts, production of the product does not need to carry out surface treatment with high susceptibility (ClassAfinish). Programmable robots have emerged as a common means of spraying a mixture of chopped glass fiber and adhesive onto a vacuum preform mold. The most important feature of robot spray is the direction of the fiber. In addition, there is a technology related to dry fiber paving (dryfiberplacement) technology, which combines Woven Preforms and resin transfer molding processes. Fiber content of the prepared products amounted to sixty-eight percent, because the whole take automation control process, to ensure low bubble content and stable copy forming effect, and the prepared products without pruning.

Vacuum assisted resin transfer molding process (VARTM) is the fastest growing new forming technology in recent years. The main difference between the vacuum assisted resin transfer molding and resin transfer molding is that VARTM is a kind of method of absorption resin into the mold injection by vacuum, while RTM is the use of pressure to pump into the mould mixture. Vacuum assisted resin transfer molding process (without high temperature or high pressure). For this reason, the VARTM process can be used not only at lower cost tools, but also in the production of complex large parts at one time.

In the VARTM molding process, the fiber reinforcement is placed in a single sided mold covered with a hard or resilient vacuum seal film. Usually the resin is sucked through injection into the mold injection principle design good mouth by vacuum, then according to the pre-set path planned to penetrate into the reinforcing material, which greatly simplifies the infiltration processing fiber (wetout). The fiber content of the product prepared by the process is as high as seventy percent. At present, the technology is mainly used in the fields of ocean, ground transportation and infrastructure.

Resin film infusion (RFI) process is a hybrid forming process, is the intervention molded into a mold, a high viscosity covered below (molecular weight) resin film layer, or the layer is thick, preform with staggered resin interlayer, by heating and vacuum pumping to make mold high molecular weight resin melt mold, uniform and full infiltration of the preform process. A major feature of this molding process is its short resin flow, and a uniform distribution of resin and a high molecular weight resin