RU2458791C2 - Method and tooling for production of hollow axially-symmetric shells (shell of revolution) from composite polymer materials - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to hot shaping of articles with fillers produced by coiling, in particular, to production of closed axially-symmetric shells with straight or flat curvilinear generatrix with constant sign of Gaussian curvature, that may be used in making aircraft engine nacelles. Proposed method comprises layer-by-layer coiling of reinforcing band on mandrel by combined spiral-helix coiling whereat band tension is increased in every next layer. Note here that tension of first layer is selected to reduce mandrel elastic envelopment to hollow shel ID. Said method comprises further the mounting of split mould on made workpiece to form the shel by thermal expansion of mandrel elastic envelopment on binder heating and curing. Tooling comprises mandrel consisting of central rigid part and elastic envelopment fitted thereon, and split mould arranged on mandrel to make cavity for composite material.

EFFECT: high-quality shells with gages outer surface.

2 cl, 2 dwg

Description

Technical field

The invention relates to the field of shaping by molding by means of internal pressure created in the material, as well as to thermoforming of products with fillers obtained by winding, in particular to the production of closed axisymmetric shells with a rectilinear or gentle curvilinear generatrix having a constant sign of Gaussian curvature along its entire length . The invention can be used in the manufacture of engine nacelles for aircraft engines and containers for storing liquids.

State of the art

The manufacture of closed axisymmetric shells with a rectilinear or gentle curvilinear generatrix having a constant sign of Gaussian curvature is carried out by the method of “dry” or “wet” preliminary winding of the reinforcing tape onto the mandrel, followed by molding (pressing at elevated temperature) of the wound workpiece in a rigid closed mold, reproducing the outer surface of the shell (part).

The well-known "METHOD FOR PRODUCING PIPES FROM COMPOSITE MATERIALS" according to the application of the Russian Federation for invention No. 94041265, class C22C 1/09, 1996. According to the application, a method for manufacturing pipes from composite material (CM) based on Me-Al reinforced with non-metallic fibers includes assembling a pipe billet on a thin-walled cylindrical shell, evacuating and hot isostatically pressing the billet from the inside to a rigid forming surface. In this case, the semi-finished product from fibrous KM is heated to 50-60 ° C, then formed on a mandrel whose radius is equal to the average radius of the pipe along the wall thickness. The assembly of the pipe from the semi-finished product is carried out on a substrate of elastic material by sequentially laying it on a diaphragm moving along the substrate with an increase in the pressure of the diaphragm to the substrate 0.04-0.06 kgf / mm of the length of the semi-finished product. The process of pressing the pipe is carried out at 550-560 ° C and an inert gas pressure of 300-350 atm. The cooling of the pipe is carried out in a snap, relieving pressure upon reaching a temperature below the crystallization temperature of the matrix material. As the substrate material, rubber is used.

The disadvantage of this method is that molding in a closed mold by creating excess pressure inside the part by various known methods leads to a decrease in the shell thickness (crimping) pre-wound on a rigid mandrel, which is prevented by the inner layers of the reinforcing material due to its high strength and stiffness. The inner layers perceive the pressing pressure and the outer layers of the shell are not "pressed", voids appear in the shell material.

Also known is “THE METHOD FOR PRODUCING COMPLEX PROFILE PRODUCTS FROM COMPOSITE MATERIALS BY THE METHOD OF CONTINUOUS WINDING” according to the patent of the Russian Federation No. 2089444, class B64C 3/20, B64F 5/00, B32B 33/00, 1995. According to the patent, the method consists in continuous multi-cyclic winding, with constant tension, of the composite material on a rotating mandrel from its end end to the root and back along a combined path. The trajectory consists in each cycle of four spiral sections, two rectilinear transitions along the root end and two circumferential sections that smoothly transition into each other. The starting point of the material laying in each subsequent cycle is shifted relative to the same point of the previous cycle in the direction of the root end, and when performing transitions, the winding-in fasteners are simultaneously wound.

The disadvantage of this method is that the method does not provide a variable level of tension of the composite material, a necessary factor for obtaining a high-quality molded product.

Closest to the proposed invention in technical essence and the achieved result is "METHOD FOR FORMING PRODUCTS FROM COMPOSITE MATERIAL" according to the patent of the Russian Federation No. 2050283, class B29D 9/00, 1992. According to the patent, the method includes the prefabrication of a mandrel from a foaming material in a mold equipped with a forming cavity and a limiting volume, its cooling and removal from the mold, the subsequent formation of a KM package on the mandrel, pressing and removing the finished product.

The manufacture of the mandrel and the pressing of the product are carried out in one form from a thermoactive material, the dimensions of the forming cavity of which change under the influence of temperature, while the curing of the product is carried out at a temperature lower than the foaming temperature of the mandrel.

The disadvantage of this method is that during the formation of the KM package, the tension is constant, which in the process of forming the product leads to uneven shaping of the product. In addition, the method uses a foam core that sets the geometric shape of the inner surface of the product, while the outer surface of the product has geometric deviations equal to the scatter (inaccuracy) of the actual thickness of the CM package. Also in the method, the product is obtained in two stages, while in the application the product is made in one technological process.

SUMMARY OF THE INVENTION

The objective of the present invention is to develop technology and equipment for the manufacture of closed, whole-molded hollow shells of revolution from high quality PCM with a calibrated outer surface.

The problem is solved due to the fact that the method of manufacturing axisymmetric hollow shells of revolution includes layer-by-layer winding on the mandrel of the reinforcing tape with a binder according to the combined spiral-ring winding scheme with increasing tape tension with each subsequent layer (the level of tension of the first layer is selected from the condition of compression of the elastic shell of the mandrel to the inner diameter of the hollow shell), the installation of a collapsible mold on the resulting workpiece and the molding of the hollow shell due to thermal expansion eniya elastic shell a mandrel during heating and curing the binder.

Equipment for the manufacture of axisymmetric hollow shells of revolution from a polymer composite material contains a mandrel consisting of a central rigid part and an elastic shell placed thereon from a thermally expanding material. The elastic shell has an outer diameter greater than the inner diameter of the hollow shell, and the thickness of the elastic shell is selected depending on the inner diameter of the hollow shell of revolution, the coefficient of thermal expansion of the material of the elastic shell of the mandrel and the curing temperature of the binder polymer composite material. The equipment also includes a rigid collapsible mold with an inner diameter corresponding to the outer diameter of the hollow shell of revolution mounted on the mandrel with the formation of a cavity for accommodating the composite material.

This solution to the problem allows you to get a closed, fully molded shell of high quality with a calibrated outer surface.

The invention is illustrated by drawings.

Figure 1 shows the mandrel for the manufacture of axisymmetric hollow shells with a workpiece located on it;

figure 2 is a section aa.

The implementation of the invention

The method in accordance with the invention is as follows:

- carry out the assembly of the mandrel, putting on an elastic shell of thermally expanding material on the rigid Central part of the mandrel, the diameter of which exceeds the inner diameter of the shell of rotation;

- carry out the installation of the mandrel on the winding machine type NK-8;

- layer by layer on the mandrel form a package of composite material from a reinforcing tape impregnated with a binder according to the scheme of a combined spiral-ring winding with longitudinal reinforcement. In Fig. 1, the layers of material are presented in the form of a reinforcing tape 1. The tape can be assembled from roving threads of the type RVMPN-1200 (fiberglass) or UKN-2500 (carbon fiber) and impregnated with a hot cure binder of the type EDT-10P directly during winding (wet winding) or fed to the winding machine in the form of a pre-impregnated prepreg. In this case, the tension of the tape is produced with an increase with each subsequent layer;

- wrap tape layer No. 1 (6) with transverse reinforcement with minimal tension. The condition of tension is chosen from the condition of compression of the elastic shell of the mandrel to the inner diameter of the hollow shell of rotation;

- wrap tape layer No. 2 (7) with spiral reinforcement with a tension exceeding the tension of the first layer, N ₂ > N ₁ ;

- lay out the tape layer No. 3 (8) along the axis of rotation of the part without tension N ₃ = 0;

- wrap tape layer No. 4 (9) with spiral reinforcement with a tension exceeding the tension of the second layer, N ₄ > N ₂ ;

- wrap with tape a layer No. 5 (10) with transverse reinforcement at maximum tension, N ₅ > N ₄ ;

- on a mandrel with a workpiece 4 located on it, parts have parts of a rigid collapsible mold 5;

- close the parts of the rigid mold 5 along the flanges, forming a smooth form-setting surface;

- install the equipment with the mandrel located in it in the furnace;

- carry out heating of the snap and curing the binder (curing mode for the binder EDT-10P - heating to a temperature of 160 + 5 ° C at a speed of 2 ... 3 ° C / min, holding for 3 hours, cooling to 50 ° C at a speed of 2 ... 3 ° C / min);

- remove the snap from the furnace;

- cool the equipment to room temperature;

- carry out the dismantling of the rigid mold 5;

- carry out the dismantling of the rigid mandrel 2;

- remove the elastic shell 3 from the inner cavity of the manufactured shell of revolution.

The method is carried out using snap.

The equipment consists of a special mandrel and a rigid collapsible mold 5.

The mandrel 2 and installed on it a rigid collapsible mold form a closed cavity for accommodating composite material.

The mandrel consists of two elements: the Central rigid part of the mandrel 2 (hereinafter referred to as the rigid mandrel) (Fig.1, 2) with the axis of rotation 11 and the elastic shell of the mandrel 3 placed on it.

The Central rigid part 2 with various forms of the generatrix can be made as monolithic (figure 1), and collapsible.

The elastic shell of the mandrel 3 is made of a thermally expanding material, for example, silicone rubber of the type IRP 1338 or similar, and has its own outer diameter in each section D _elastic , exceeding the inner diameter of the hollow shell of revolution (blank) d _ext . The thickness of the elastic membrane 3 is selected depending on the internal diameter of the manufactured shell rotation d _ext type elastic casing material, the thermal expansion coefficient of the material of the elastic membrane 3 and the curing temperature of the binder of the composite material shell rotation. The elastic shell 3, placed on a rigid mandrel 2, fits snugly against it and is held on it by friction forces.

A rigid collapsible mold 5, defining the surface of the external theoretical contour of the hollow shell of revolution, is made collapsible in order to facilitate the extraction of the finished hollow shell of revolution after molding. A rigid mold 5 consists, for example, of four sections (Fig. 2), each of which has two flanges along the entire length of the joint, ensuring smooth mating along the inner surface of the mold 5. The rigid collapsible mold 5 has a smooth (polished or polished) inner surface with a diameter D in each section. The diameter D corresponds to the outer diameter of the hollow shell of revolution.

Proposed by the present invention, the method is as follows.

First of all, the mandrel is assembled: an elastic shell 3 is pulled onto a rigid mandrel 2. Next, the mandrel is placed on the pins of a winding machine such as NK-8. Then, on the mandrel (on the outer surface of the elastic shell of the mandrel 3), a reinforcing tape with different reinforcement angles is wound and layered in layers. The reinforcing tape is winded with an increase in the level of pre-tension, from the previous layer to the next, N ₁ <N ₂ <N ₄ <N ₅ . The level of tension of the first layer (inner) 6 is selected from the condition of compression elastic shell 3 _unp D to inner diameter d _ext rotation of the casing with the elastic deformation of the shell 3. When winding of each subsequent layer increases the level of tension than the layers with the angle reinforcement in the 0 °, relative to axis of rotation of the shell of rotation (no tension), N ₃ = 0. 10 final (outer) layer of the reinforcing tape is wound with the maximum tension of the conditions for obtaining a predetermined outer diameter d _nap rotation of the casing, in each section, with the elastic deformation of the shell 3 and reduce the blank thickness of the package 4 at a tension of each subsequent layer. The process of forming a PCM package of a shell of revolution can be carried out both by “dry” (from a reinforcing tape pre-impregnated with a binder) and “wet” (a reinforcing tape is assembled from individual threads and impregnated with a binder during winding) by methods.

To form the external contour (since) of the hollow shell of rotation, a collapsible mold 5 is installed, combined and closed on the flanges using bolted joints on a mandrel with a wound blank 4.

After the mold 5 is mounted on the mandrel, the snap is removed from the winding machine and installed in the furnace on special devices where the part is molded. A variant of the built-in heating elements in the body of the mandrel and the mold is possible. In the case of built-in heating elements, curing is carried out in the workshop without using a furnace.

In the process of heating in the furnace, the binder cures, and the molding pressure is created due to the constrained thermal expansion of the elastic mandrel 3 in a closed volume of equipment and compression by the reinforcing tape 1 of the final layer of the shell of revolution. The enclosed volume of the tooling is formed by the rigid part of the mandrel 2 and the inner surface of the mold 5. As a result, after molding, the outer surface of the rotation shell is “calibrated”. In this case, the inner layers of the workpiece, “crimped” by the outer layer, have an “excess” turn length and can qualitatively “push through” the entire package of the reinforcing material of the shell of revolution (the lengths of the turns of the spirals exclude their additional tension when expanding the elastic mandrel by the amount of “crimping” the PCM package and do not interfere with the molding process). The finished shell of rotation has an outer diameter equal to the inner diameter of the mold. After the curing process is complete, the equipment is removed from the furnace and cooled to room temperature. After the equipment has cooled, carry out the dismantling of the mold 5, removing it by sectors. Next, a rigid mandrel is dismantled by pulling it from the elastic mandrel on which the rotation sheath is located. After that, from the cavity of the finished shell of rotation, an elastic mandrel is removed as a "stocking", pulling it toward a larger diameter of the shell of rotation.

Due to the fact that the winding with variable tension used in this method does not prevent an even distribution of pressure over the thickness of the workpiece, stability (repeatability), high quality and high strength characteristics are ensured during the manufacture of the rotation sheath. The application of this method and such equipment will allow the production of solid-formed large-sized shells of revolution with a calibrated outer surface. In addition, the use of a high-performance dry winding method reduces the complexity of the product and be competitive in the market.

Claims (2)

1. Equipment for the manufacture of axisymmetric hollow shells of revolution from a polymer composite material, comprising a mandrel consisting of a central rigid part and an elastic shell placed thereon from a thermally expanding material having an external diameter greater than the inner diameter of the resulting shell, and a thickness selected depending on the inner the diameter of the hollow shell, the coefficient of thermal expansion of the material of the elastic shell of the mandrel and the curing temperature of the binder polymer composition ionic material, and a rigid dismountable mold with an inner diameter corresponding to the outer diameter of the hollow shell mounted on a mandrel to form a cavity for placement of the composite material. 2. A method of manufacturing axisymmetric hollow shells of revolution from a polymer composite material, including layer-by-layer winding on a mandrel, consisting of a central rigid part and an elastic shell placed on it with an outer diameter exceeding the inner diameter of the hollow shell reinforcing tape with a binder, according to a combined spiral ring winding with increasing tension of the tape with each subsequent layer, while the level of tension of the first layer is selected from the condition of compression of the elastic shell of the mandrel to ext friction diameter of the hollow shell, establishing a dismountable mold to obtain a preform molding hollow shell due to thermal expansion of the elastic shell binder mandrel during heating and curing, cooling and dismantling the mold, removing the rigid part of the mandrel and removing the elastic membrane.

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