Vacuum Assisted Resin Infusion Molding

Vacuum Assisted Resin Infusion Molding (Vacuum Assisted Resin Infusion Molding), referred to as VARIM process, is a high-performance, low-cost composite material molding process developed on the basis of RTM (Resin Transfer Molding) process. Developed in the late 1980s, VARIM process, as a new liquid composite molding technology (Liquid Composite Molding, referred to as LCM), has been widely used in aerospace, national defense engineering, shipbuilding industry, energy industry, infrastructure engineering and other fields. Attention is paid to it, and it is researched and applied as a key low-cost manufacturing technology by the Composite Affordability Initiative (CAI) implemented by the United States.

picture

???As shown in Figure 1, the basic principle of the VARIM process is to use the flow and penetration of the resin to impregnate the fiber fabric reinforcement material in the closed mold cavity under vacuum negative pressure conditions, and then solidify and form. The basic process of the VARIM process includes:

??(a) Preparation stage. Including single-sided rigid mold design and processing, mold surface cleaning and coating release agent, reinforcement materials (fiber fabrics, preforms, core materials, etc.) and vacuum auxiliary media (release media, high permeability diversion media, gas-conducting medium, etc.) preparation, etc.

??(b) Lay-up stage. On the single-sided rigid mold, the reinforcing material, release cloth, peeling layer medium, high-permeability diversion medium, resin infusion pipeline, vacuum air guidance pipeline, etc. are sequentially laid.

??(c) Sealing stage. Use sealing tape to seal the reinforcing material and vacuum auxiliary medium in the elastic vacuum bag film, and vacuumize to ensure that the sealed mold cavity reaches a predetermined vacuum degree.

??(d) Perfusion phase. Under vacuum negative pressure, the resin glue is introduced into the closed mold cavity through the resin infusion pipeline, and the reinforcement material is fully impregnated.

??(e) Curing stage. Continue to maintain a high degree of vacuum, and the liquid resin undergoes a curing and crosslinking reaction at room temperature or under heating conditions to obtain a product preform.

??(f) Post-processing stage. Including cleaning the vacuum bag film, diversion medium, peeling layer medium, release cloth and other vacuum auxiliary media and demoulding trimming, etc., and finally get the finished product.

Compared with the traditional open molding process and RTM process, the VARIM process has the following advantages:

??(1) The mold cost is low. Compared with the RTM process that requires rigid molds on both sides of the female and male sides, the VARIM process only requires a single-sided rigid mold; compared with the forming mold that needs to withstand high temperature and high pressure in the molding process, the manufacturing cost of the mold is lower, and it is suitable for the design and development of different structures. Large molds with complex shapes.

??(2) The shape of the product is controllable and the size is accurate. The VARIM process has fewer restrictions on the size and shape of the product, and can be used for the molding of large-thickness and large-size structural parts in the fields of aerospace, national defense engineering, shipbuilding, energy industry, and infrastructure engineering, such as rocket shells and wind turbine blades. , Car shells, etc.

??(3) The product has good mechanical properties and high repeatability. Compared with hand lay-up components, the mechanical and mechanical properties of VARIM process molding products can be increased by more than 1.5 times, and the products have high fiber content, low porosity, few structural defects, uniform and smooth surface, and high consistency between components. Therefore, VARIM process The quality of molded products is stable and has good repeatability.

??(4) Good environmental protection. Compared with open molding, the volatilization of styrene, acetone and other volatile organic compounds (VOCs) is as high as 35~45%. Both air pollution and toxic air pollutants are confined in the vacuum bag film, so there is almost no pollution to the environment, which is the most prominent advantage of the VARIM process.

??(5) High production efficiency. The resin under vacuum negative pressure can be quickly introduced into the closed mold cavity along the resin infusion pipeline, and fully and quickly penetrate and impregnate the reinforcement material before gelling, which can integrally form large-scale complex geometric shapes of sandwich and reinforced structural parts. Compared with the mold opening process, the VARIM process can save more than 50% of labor.

Application of VARIM process

???As a new type of composite material forming process, the VARIM process began in the late 1980s. At the beginning, this process was not highly valued by people and failed to realize its potential huge commercial value. Until 1996, due to the successful application on ships, the VARIM process was recognized and valued at the SPI Composite Materials Annual Conference that year. Because the VARIM process has many advantages such as low cost, high product quality, suitable for manufacturing large and complex overall structural parts, etc., after more than ten years of research and application, the VARIM process is no longer limited to the application of the shipbuilding industry, but has been widely used in the world In the construction of many military and civilian facilities, such as military ships, missile cabins, radomes, wind turbine blades, bridges, car shells, refrigerators, etc.

#handlayup?#vacuuminfusion??#vacuuminfusionbody??#vacuuminfusionprocess?#Fiberglass?#fiberglasshandmade??#Fiberglasshandlayup?#RTM