Forming equipment for the production of composite material samples

Abstract

This utility model relates to the manufacture of polymer composite products using vacuum infusion, specifically the production of molding tooling. The proposed tooling can be used to manufacture experimental, control, and standardized samples of aeronautical and rocket-space equipment subject to mechanical and thermal testing conducted by research and testing laboratories at institutes and higher education institutions. The importance of solving the above technical problem stems from the need to create molding tooling for the production of single-unit or small-scale laboratory samples of polymer composite materials that is economically feasible in terms of material and time costs for its manufacture, maintains its spatial configuration under repeated loading cycles and temperature exposures, and does not require complex surface cleaning.The technical objective of the proposed utility model is to create a composite molding tool for the production of polymer composite samples by vacuum infusion with the ability to reproduce their complex spatial configuration through layer-by-layer molding of a polymer shell along the contour of a three-dimensional model.The technical result is achieved in that the equipment is made in the form of a composite mold-forming shell based on fiberglass and an epoxy binder, the working surface of which is formed by successively applying a separating layer of wax, a polymer surface layer and a composite reinforcing layer onto a technological base made of sheet polyvinyl chloride plastic with three-dimensional models of samples fixed to it, wherein after the polymer layer has hardened, the technological base is removed, and the reverse side of the resulting composite shell is reinforced with a polymer matrix with reinforcing fabric, ensuring resistance to multiple cycles of vacuum infusion.

Description

[0001] The utility model relates to the field of manufacturing products from polymer composites using the vacuum infusion method, in particular to the production of molding equipment.

[0002] The proposed equipment can be used for the production of experimental, control and standardized samples of aviation and rocket-space technology products subject to mechanical and thermal-physical tests carried out by research and testing laboratories of institutes and higher educational institutions.

[0003] Molds for producing composite material samples are known. They are made from monolithic metal plates or prefabricated frames with subsequent machining of the working surfaces. Russian Federation Patent for Utility Model No. 171834U1 describes tooling for producing polymer composite structures using vacuum infusion. The tooling comprises a support system made in the form of a profiled monolithic metal element with a system of internal and exhaust channels, while the mold-forming shell is made in the form of a perforated closing sheet with external vacuum channels located on it. The disadvantages of this technical solution include the high metal consumption of the structure and the significant cost of tooling manufacture, as well as the need for complex machining to create sealed vacuum channels, which limits the use of such tooling in laboratory settings for single-unit or small-scale sample production.

[0004] A method for modifying molding tools produced by additive manufacturing is known. According to Russian Federation Patent No. 2845064 C1, layers of dry fabric and unidirectional tape made of glass, carbon, or organic fibers are laid on the molding surface of the tooling blank. A stack of process layers is placed on top, covered with a vacuum bag, and sealed. The dry layers are then impregnated using a vacuum impregnation method, cured, and then the upper composite layer of the molding tooling is mechanically processed. A disadvantage of this method is the need for mandatory subsequent mechanical processing of the surface to achieve the required geometric accuracy, as well as the risk of leakage of the working area during repeated loading cycles and temperature exposure.

[0005] Invention patent RU 2508176 C1 proposes a device for producing samples from castable curable resins. The device's body is formed by detachable side walls and top and bottom covers. The top cover includes elements for connecting the sprue channel to a container for sample material and a vacuum pump. This technical solution does not envisage its use in forming composites with dry reinforcing filler.

[0006] The closest to the claimed utility model in technical essence and the achieved result is a composite form-forming equipment according to the invention patent RU 2716432 C1, which includes a support system in the form of a rectangular hollow parallelepiped made of an equal-flange angle and a form-forming shell installed on it, made of a three-layer honeycomb panel containing a curved part repeating the geometry of the product, turning into a rectilinear part, by means of which the shell rests on the support system.

[0007] This tooling solution is designed for the molding of large-scale industrial products and requires the use of specialized materials (three-layer honeycomb panels, adhesive films, metal profiles), as well as complex support system assembly. These features make the manufacture of such tooling economically impractical for producing single-unit or small-scale laboratory samples of polymer composite materials, and also preclude the possibility of quickly adapting the geometry of the molding elements.

[0008] The technical objective of the proposed utility model is to create a composite molding tool for the production of polymer composite samples by vacuum infusion with the ability to reproduce their complex spatial configuration by layer-by-layer molding of a polymer shell along the contour of a three-dimensional model.

[0009] The importance of solving the above-described technical problem is associated with the need to create molding equipment for obtaining single or small-scale batches of laboratory samples of polymer composite material, which is economically feasible in terms of material and time costs for its production, maintains its spatial configuration during multiple cycles of vacuum infusion and does not require a complex process of cleaning the working surface.

[0010] The technical result is achieved in that the equipment is made in the form of a composite mold-forming shell based on fiberglass and an epoxy binder, the working surface of which is formed by successively applying a separating layer of wax, a polymer surface layer and a composite reinforcing layer onto a technological base made of sheet polyvinyl chloride plastic with three-dimensional models of samples fixed to it, while after the polymer layer has hardened, the technological base is removed, and the reverse side of the resulting composite shell is reinforced with a polymer matrix with reinforcing fabric, ensuring resistance to multiple cycles of vacuum infusion.

[0011] The stated technical result is achieved through the interplay between the design and technological features of the utility model. The use of a sheet of polyvinyl chloride plastic as a technological base with attached three-dimensional models ensures the formation of the initial geometry of the mold cavity, and their subsequent removal after curing allows for the repeated use of the finished tooling without the complex process of cleaning its working surface. The sequential application of a release wax and a polymer surface layer creates a smooth, chemically inert surface, preventing adhesion of the molding material to the tooling and reducing the formation of surface defects and porosity in molded samples. A composite reinforcing layer creates a load-bearing shell that evenly distributes pressure during vacuuming and prevents deformation of the molding elements during impregnation and curing of the binder.A reinforcing layer on the back of the working surface compensates for internal shrinkage stresses during resin polymerization, preventing changes in the working surface's shape. These features, taken together, ensure precise reproduction of the formed specimens' geometry in full compliance with regulatory requirements for tensile, compression, bending, interlaminar shear, impact strength, thermal conductivity, and thermogravimetric analysis testing.

[0012] Fig. 1 shows a three-dimensional visualization of the resulting equipment - in isometric view.

[0013] Fig. 2 shows a three-dimensional visualization of the resulting equipment - bottom view.

[0014] The composite molding tool is manufactured on a technological base made of sheet polyvinyl chloride plastic. Three-dimensional models of samples, prefabricated using additive manufacturing from readily available engineering thermoplastics, in particular acrylonitrile butadiene styrene, are fixed to the technological base using a fast-acting cyanoacrylate-based adhesive. The use of additive manufacturing methods allows for the creation of initial molds of the desired spatial configuration, including complex geometric elements, without the use of expensive equipment and time-consuming machining. The distance between adjacent models of the fixed samples is maintained within the range of 10 to 80 millimeters (Fig. 1). Sides of sheet polyvinyl chloride plastic are formed around the perimeter of the working area, forming a closed contour for additional stability of the tooling (Fig. 2).

[0015] The surface of the base, models, and sides is degreased, and then sequentially coated with 4-5 layers of release wax. Allow at least 30 minutes between coats. Polishing is performed before applying the next coat. After the final release coat has fully cured, a matrix polymer surface coat (e.g., gelcoat) with a hardener is applied. The mixture is distributed in an even layer over the entire work area, including the inner surface of the sides, by mechanically leveling with a hand tool until a continuous film is achieved, free of unpainted areas and drips. Once the polymer surface coat is tack-free, which occurs within 3-4 hours at room temperature, a thick mixture of chopped fiberglass and epoxy resin with a hardener in a 100:50 weight ratio is applied to the surface.The specified thickness of this layer is between 2-3 millimeters and is achieved by gradual installation with mechanical compaction. Monitoring is performed using a thickness gauge before polymerization begins.

[0016] Then the surface is covered with fiberglass and glass veil patches with a density of 20 to 300 g / m 2 The layers are laid in an overlapping pattern, starting with the materials of the lowest density and progressing to those of the highest density, which promotes gradual compaction of the structure and reduces air entrapment. The composite shell cures within 24 hours at ambient temperature. After curing, the PVC base is removed from the reverse side, while the side railing remains as part of the structure for additional rigidity.

[0017] To reduce internal stresses and eliminate possible defects, the reverse side (Fig. 2) of the resulting composite shell of the tool (working surface) is additionally filled with epoxy resin with medium-density fiberglass placed inside, corresponding to the dimensions of the tool.

[0018] The subsequent technological process, including the placement of dry reinforcing filler into the forming elements of the working surface of the resulting tooling, a sealing bundle, a binder supply line, a vacuum line with a resin trap and the subsequent application of a vacuum bag along the contour of the applied bundle, will make it possible to obtain molded samples from polymer composite materials using the vacuum infusion method.

[0019] The use of the claimed composite molding equipment ensures the precise reproduction of spatial configurations of the geometry of samples made of polymer composite materials of varying complexity, eliminates the need for a complex process of cleaning the working surface of the equipment and allows its use in multiple technological cycles of vacuum infusion.

[0020] List of references:

[0021] 1. No. 171834U1;

[0022] 2. No. 2845064 C1;

[0023] 3. No. 2508176 C1;

[0024] 4. No. 2716432 C1.

Claims

A composite molding tool for producing samples from polymer composite materials, comprising a molding shell and a support system, characterized in that the working surface is made in the form of a multilayer composite structure, sequentially formed on a technological base made of sheet polyvinyl chloride plastic with three-dimensional models of samples fixed thereto and including a separating layer of wax, a polymer surface layer and a composite reinforcing layer based on fiberglass and an epoxy binder, wherein the reverse side of the tooling structure is reinforced with a polymer binder with reinforcing fabric, and a side fence is integrated along the perimeter of the working area, which cannot be dismantled after molding.

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