Composite materials have been used for many years in various fields of industry and construction. Products of this kind significantly increase the characteristics of the elemental base in technology, electronic devices and building materials. In this case, the composites differ among themselves in operational properties determined by the manufacturing technology. The introduction of a vacuum material manufacturing technique into the production process, for example, allows one to obtain high-quality carbon. However, until recently, the problem of eliminating excess resin remained, the presence of which caused the fragility of the product. To maximize the physical properties of the material through the removal of resins, vacuum infusion is used, which, although it does not guarantee the complete elimination of negative technological factors, allows to endow the final product with optimal technical qualities at low cost.
Method Overview
The essence of the method is to create a vacuum inside the working cavity, due to which the reinforcing material is impregnated and the resins are drawn in. As with other modern methods for producing composites, a vacuum is used as a molding cavity - as a rule, a special film bag is used to organize the process. Unlike the common method of contact molding, the vacuum infusion unit, which includes a special matrix with dry filler, allows the production of fiberglass with a minimum content of porous inclusions and a higher degree of reinforcement. For some consumers, another difference in this technique is important. It involves a significant reduction in the emission of harmful substances. In particular, the amount of styrene is reduced, the presence of which often becomes an obstacle when using products in the construction of residential buildings.
Execution technology
First of all, a filler is laid on the prepared snap-in with vacuum, which can be represented by special substances and combined canvases. Then technological layers are laid, due to which in the future the uniform distribution of the binder component should be ensured. Next, a vacuum is directed to the technological package, the binder tolerance channel opens, under the influence of an already active vacuum, the voids are simultaneously filled and the filler is impregnated. The percentage of porosity depends on the ambient temperature at which the vacuum infusion is performed. The technology for implementing the method in an industrial environment, on average, ensures the preservation of 1-0.5% of the pores relative to the total mass of the composite product.
Vacuum Infusion Equipment
The basis for the installation of infusion is the matrix mentioned above. This is a platform in some way, the average dimensions of which can correspond to the usual square-shaped laminate panel and the area of the production workshop. From the point of view of the quality of the composite obtained, it is more important to trim the matrix, on which the quality of the supply of the binder and the function of the vacuum depend. The vacuum pump for infusion is responsible for the formation of vacuum in the system, with the help of which uniform pressure of consumables in the matrix platform is ensured. In other words, it creates the effect of absorption of the binder components.
To capture the resin, a special trap is also used, which is a sealed container. This technological element collects excess resin formed during the impregnation of the reinforcing material. The trap also protects the pump from penetrating into it the same resins. The work of infusion is impossible without quality fittings. The infrastructure of this part is represented by fittings and tubes that organize the operation of the supply channels of the binder material.
Matrix Fillers
The materials used for placement in the basic equipment are related to reinforcement. Actually, they form the basis of the future product and to the greatest extent determine its operational properties. Depending on the direction of production, these can be carbon fillers, basalt fabrics for insulating materials, Kevlar aramids, etc. A separate group includes materials for vacuum infusion, from which fiberglass is subsequently obtained. It includes traditional fiberglass fabrics, glass roving, glass veils and glass mat. Combined fabrics are also becoming more common. In particular, due to the combination of different technical and physical properties, aramid-carbon and aramid-basalt fillers are popular.
Supporting materials
This group of materials is used only for organizing the infusion process itself and is not part of the final product. As the operation is completed, such substances are removed. The main component of this type is sacrificial tissue, which is designed to form a smooth inner cavity of the workpiece, which forms a vacuum infusion. The equipment is also protected by this fabric from extruded resins. The protective function of the sacrificial material is determined by the resistance of its structure to external influences and minimal adhesion. In addition, the list of obligatory auxiliary materials includes a conductive mesh designed to remove air and supply resin to the reinforcing base. In preparing the matrix, a vacuum film is also used. It is distinguished by an increased tensile modulus of about 400% and the ability to withstand temperatures above 100 ° C.
Binder component
The binder has a great responsibility, therefore high demands are placed on it. This should be a material with a low degree of viscosity and exothermic peak, and at the same time high viability. The substance corresponding to these parameters will ensure quick absorption of the reinforcing material and maintain an optimal working structure. For this, special resins are used, thanks to which vacuum infusion can provide impregnation of substrates with a thickness of up to 10 mm. High vitality is of particular importance in working with large products - this quality helps to complete the process before gelatinization.
Binder Supply Organization
The organization of the infusion process in two ways is practiced: circular and parallel. In the first case, the channel is placed along the perimeter of the matrix, and the binder feed points are located in the niche of the vacuum ring. As a result, the movement of the resin is organized in the direction from the center point to the perimeter. At the same time, leakage of air flows is excluded, since vacuum infusion will close the channel in the ring.
The organization of the parallel distribution of the binder involves the opposite placement of the vacuum channel and the resin feed point. In this case, the movement of the resin occurs from one side to the other. The disadvantages of this scheme include just the leakage of air around the perimeter of the equipment, which is eliminated with an annular resin supply.
Product Quality Factors
Control of several parameters of the organization of the production process will minimize the risk of obtaining a final product of unsatisfactory quality . First of all, vacuum tightness refers to them - the shell material should not have holes or places of loose contact with the filler. Further, the viscosity index of the resin, which should not exceed 600 MPa * s, is taken into account, otherwise the process will be slow and more likely to allow the formation of voids. Much depends on the quality of the laying of tissue layers. The factory method of vacuum infusion is particularly demanding on the distribution of layers of carbon material. Correct laying without uneven sections will increase the chances of getting a composite that is balanced in its internal structure.
Conclusion
Artificial materials are actively replacing traditional raw materials in the market. This process covers a wide variety of areas. The distribution of synthetic plastics is determined by the beneficial performance properties that are endowed with the same carbon or fiberglass. In this context, vacuum infusion is only one of the technological means to ensure high technical and physical qualities of the material obtained. Initially, technologists developed this method as a tool to get rid of the negative aspects of production. In particular, infusion reduced the presence of voids in the structure of the material. In the future, the method also demonstrated other positive qualities, which were expressed both in increasing environmental cleanliness and in reducing financial costs for production.