RU2396168C2 - Method of producing carbon composite sophisticated shape structures and method to this end - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: set of invention relates to device and method of producing carbon composite truss-shaped structures. Proposed method comprises assembling fixture, laying fittings representing carbon bundles stationary fitting along lengthwise axis of the latter, impregnating with polymer binder and heating to temperature facilitating withdrawing ready structure. Ready structure is withdrawn at temperature approximating to lower limit of polymerisation range. Note also that polymer binder is selected to have vitrification temperature exceeding and approximating said lower limit of polymerisation range. Device comprises workpiece, lower die, inner punch and pressure generating device. Inner punch consists of three elements with their shape mating that of pressure generating device and profile of the truss lengthwise elements. Lower die consists of three elements with their shape mating that of the truss crosswise elements. Note also that pressure generating device represents a silicon chamber with union connected to compressor.

EFFECT: possibility to produce sophisticated shape structures meeting strict requirements to geometry, weight and sizes.

3 cl, 6 dwg

Description

The present invention relates to a technology for manufacturing products using carbon fiber, improves this technology in relation to products of complex shape, and can be used for the manufacture of structures requiring the use of a matrix and punch, the forms of which differ from the known and traditional ones.

Carbon fiber structures added to some solid materials, such as resin, plastic, ceramics, metal, etc., can improve the required physical properties of the manufactured product. These properties include electrical, thermal, or mechanical characteristics. Carbon fiber is also used in combination with a polymer binder.

Polymers, as you know, are substances consisting of macromolecules (molecules containing a large number of valence bound atoms, reaching tens and hundreds of thousands). Macromolecules are often obtained in the polymerization process, in which double bonds are opened in the starting molecules of the substance, due to which polymer chains are formed without isolating other substances. Unlike a molecule, a macromolecule is not the smallest particle of a substance - a carrier of chemical properties. Polymers can be in various states: crystalline, glassy, viscous-flowing and highly elastic. The latter is characteristic only of polymers, in contrast to substances from ordinary molecules (low molecular weight substances). The cooling of a polymer from a viscous flowing melt to glass represents a continuous transition from a mobile system to a solid (see the Physical Encyclopedic Dictionary, Volume Four, Moscow, 1965, p. 94). A normal polymerization cycle is a manufacturer-defined heat treatment process that guarantees the mechanical properties of a material.

A known method [1] of increasing the cracking resistance, strength and heat resistance of a ceramic material by adding carbon fiber at a ratio of components (wt.%): Boron carbide 60-78, silicon carbide 7-22, titanium carbide 3-11, titanium diboride 3 -15, carbon fiber 0.3-15.

A known method of manufacturing a rocket block [2] used in the design of fuel tank compartments. According to one of the options, the compartment is made in the form of two tanks with a common intermediate bottom. The bottom has a cylindrical section in the form of a two-layer shell. The inner layer is the polymeric material, and the outer layer is carbon fiber. On a cylindrical section between the upper and lower bottoms, a three-layer shell is laid out, which includes carbon fiber inner and outer plating and a filler with docking profiles at its ends. An adhesive film is applied to the cylindrical sections of the bottoms. Curing of the layers and gluing of the bottoms is carried out in an autoclave. The result is a reduction in the mass of the rocket block structure at high strength.

A known design of the traction chain for lowering and lifting continuous steel pipes during the operation and repair of oil wells [3]. The chain has friction pads that transmit traction to the pipe. The pads are equipped with plug-in elements (crackers), consisting of four parts, two of which are steel, and two are made of composite material. Carbon fiber was used as the composite material, and the surface area of the steel components of the cracker refers to the surface area of the components made of the composite material, as 1: 1.5. The selected combination of materials and their sizes provides wear resistance and high traction force of friction pads throughout the entire period of operation of a long steel pipe.

Known blade of a thermoplastic composite material, in particular for the tail rotor of a helicopter and the method of its manufacture [4]. The blade contains the lower and upper parts of its shell, the front and rear elements of its filling and the spar of a composite material consisting of the same matrix, thermoplastic and representing a synthetic resin REEK, preferably reinforced with carbon fibers. The method consists in assembling prefabricated in the form of elementary parts: a spar, the lower and upper parts of the blade shell using injection molding of a liquefied thermoplastic composite material with short reinforcing fibers used to form the filling elements of the blade shell. The invention allows to simplify the manufacturing technology of the blade.

A known method [5] to reduce the angular vibration of the camshaft relative to the crankshaft in internal combustion engines, in which the camshaft is driven by timing belts. The tension element is a cord in the form of a helical spiral, made of at least one thread containing carbon fiber.

The known design of the support nodes for the placement of satellite equipment on three-layer panels of space platforms [6]. The three-layer panel has an upper and lower skin made of a polymer composite material, between which a honeycomb is placed. The support assembly includes a sleeve fixed to the panel. As a polymer composite material, a tow of carbon or glass fibers impregnated with a foaming adhesive composition was used. The expandable adhesive composition is reinforced with chopped fiber using carbon or glass fibers. Reinforcing the adhesive composition with the named fiber allows it to be strengthened and, accordingly, the junction of the sleeve with a three-layer panel.

A known design of a high-pressure boiler [8], which includes the body of the boiler and fiber reinforced plastic layer formed on the surface of the boiler. The carbon fiber for the boiler has high tensile parameters: it has an elastic modulus of 305 GPa or higher with a relative elongation of 1.45 to 1.70%.

A device is known for the manufacture of carbon fiber dentures [9]. Carbon fibers are placed in an elongated tube, which has an internal arch-shaped denture at the end. The binder is supplied through the tube in a liquid state. After cooling and transition to a solid state, a strong prosthetic bridge is formed, fixed without loops and sharp bends.

Known non-woven reinforcing mesh of carbon microfibers [10]. It can be used as the basis for many products. Being impregnated with resin may have the properties of a metal.

The disadvantages of methods and devices known from the prior art for the manufacture of products of complex shape include their unsuitability for the manufacture of products of a more complex shape, i.e., with hard-set parameters of elements: combinations, for example, weight, geometry of elements, trajectories of product elements on a plane, and t .P.

A known method of laying on the mandrel of longitudinal threadlike reinforcement [7], the closest in technical result to the proposed method and taken as a prototype. This installation method includes, in one embodiment, assembling a cylindrical mandrel with crowns placed in annular rows along the edges of the reinforcement laying section, laying the reinforcement on the mandrel along its longitudinal axis with the help of the reinforcing arm. The mandrel and spreader are driven in a coordinated motion during installation. To obtain filamentous reinforcement, carbon fibers, carbon filaments or bundles drawn from fibers are used. The thread-like reinforcement is impregnated with a polymer binder during installation. It is provided for heating of individual elements of the distributor during installation to a temperature that eliminates the difficulties of tightening the reinforcement.

The proposed technical solution for the method of manufacturing carbon composite products of complex shape coincides with the prototype in the largest number of features, such as assembly of the mandrel, laying of reinforcement on the mandrel along its longitudinal axis, the use of charcoal tows, impregnation with a polymeric binder material, heating to a temperature that excludes difficulties when removing products . The disadvantage of the prototype is the impossibility of its use for the manufacture of products of complex shapes.

There is a method of forming an external thread at the end portion of a pipe billet from which a device for manufacturing such a thread [11] is viewed, which is closest in technical result to the claimed device and is taken as a prototype (for the device). The prototype device consists of a tubular workpiece with an outer diameter of the end portion equal to the inner diameter of the threaded matrix, a threaded matrix with an internal thread, the profile of which corresponds to the profile of the thread produced on the workpiece, and also from a device (which acts as an internal punch), allowing pressure from inside to increase the diameter of the end section with the metal filling the workpiece threaded grooves of the matrix. A feature of the device is the location of the punch inside the device, and the matrix that determines the shape of the finished product, outside. The disadvantage of the device, from the point of view of manufacturing products of a more complex shape (compared with the external thread), is the rather simple shape of the matrix.

The claimed invention is aimed at solving the technical problem of manufacturing carbon composite products of complex shape. Moreover, by “complexity of shape” is meant a complex combination of hard-set parameters, for example, a significant size in one of the directions and / or a significant restriction of the mass of the material used, and / or stringent requirements to the geometry of the product, and / or to their combination together with a given weight and etc.

The need to manufacture such products arose in connection with the construction of an internal support system for electronic components of the charged particle accelerator of the European Nuclear Center, one of the performers of which is the Applicant. For example, the supporting structure of the line of nuclear radiation detectors is a trihedral truss 1200 mm long, consisting of a set of longitudinal and protruding transverse elements 0.2-0.8 mm thick. Another factor complicating the manufacture of such a truss is the high requirements for the accuracy of the finished product, for example, the deviation from the flatness of the base elements over a length of 1200 mm should not exceed 0.1 mm. These are rather stringent conditions for the manufacture of carbon composite products, which have a complex shape.

The technical result of the claimed invention is to provide the possibility of manufacturing products of complex shape, including weight restrictions and stringent requirements for the geometry and solidity of ultralight spatial structures.

The specified technical result is achieved by the claimed method of manufacturing carbon composite products of complex shape due to the fact that, in accordance with the invention, including the assembly of the mandrel, laying the reinforcement in the form of carbon bundles on a fixed mandrel along its longitudinal axis, impregnation with a polymer binder material and heating to a temperature excluding Difficulties in the removal of the product, the removal of the finished product is carried out at a temperature close to the lower boundary of the temperature range of the polymerization, but above this boundary, and the polymer the binder material is selected with a glass transition temperature close to the named temperature.

In addition, this technical result is achieved by the fact that in the claimed method of manufacturing carbon composite products of complex shape to correct products having an increased deviation from the nominal, these products are heated to a temperature lying in the range above the glass transition temperature of the polymer binder, but below its destruction temperature , while supporting products on base surfaces lying in parallel planes, with their further cooling in this position.

In addition, this technical result is achieved by the claimed device, shown in a specific example of its implementation in the form of a truss containing a workpiece, a matrix, an inner punch and a device that creates pressure from the inside, the inner punch is made of three elements, the shape of which corresponds to the shape of the device allowing pressure from the inside, and to the profile of the longitudinal elements of the truss, the matrix consists of three elements, the profile of which corresponds to the profile of the transverse truss elements, and the device that creates phenomenon from the inside, made in the form of a silicone chamber with a fitting.

The lower limit of the polymerization temperature range is defined as the temperature at which, during cooling, the polymerization initially consolidates and preserves the mechanical properties of the product, allowing the product to be removed without disturbing the shape. The difference in the linear expansion coefficients of the matrix material (and the punch, if it contains elements that determine the shape of the product) and the product material is the factor that usually leads to the destruction of the product when the matrix cools. Therefore, it is proposed that the product be removed from the matrix according to the claimed method at a temperature at which the difference in the linear expansion coefficients of the matrix material and the product is negligible, and it does not lead to destruction of the product. In this case, the polymerization temperature interval is understood to mean the interval at which the product is in the forming matrix. The polymerization process continues when the product cools outside the matrix, when the mentioned difference in expansion coefficients ceases to affect.

Generally speaking, the manufacture of composite products (composites) using forming matrices is carried out at different temperature conditions, depending on many parameters determined by the requirements for the final product. It is known that composites that have been cured at high temperatures have higher mechanical characteristics with respect to composites cured at room temperature.

So, large hull products, such as, for example, hulls of yachts, are made of composite materials that cure at room temperature. Their heating is not economically justified. The forming matrix for such a process, as a rule, is also made of composite material. The necessary mechanical characteristics of the product in this case can be provided by an increased thickness of the walls of the housing.

In cases where the weight of the product is critical, along with high requirements for mechanical performance and accuracy of forming, composites are used that have a polymer binder of hot curing (about 120 ° -180 ° C). In such processes, as a rule, metal forming matrices are used, for example, in the manufacture of hull elements of airplanes or spacecraft.

High-temperature polymerization has to be applied without fail, for example, to provide vacuum impregnation of the composite fibers or in order to obtain sufficient technological time necessary for laying the composite in a forming matrix.

Known methods for the hot polymerization of composites include heating the forming metal matrix and the composite. The problem is that the linear expansion coefficients of the metal and the composite are different. In some cases, the difference is expressed by a ratio of 1:10. An example is a steel forming matrix and a carbon composite. At a polymerization temperature of 120 ° C, the elongation of the steel forming matrix over a length of one meter is 1.2 mm, while the carbon composite does not lengthen, or even vice versa, is shortened by a certain amount.

Thermal processing of products of simple forms that do not have significant protruding and buried elements does not cause difficulties. In the process of cooling the walls of the forming matrix and the composite slip relative to each other and the destruction of the product does not occur. If the product has protruding or transverse elements, then during cooling, the difference in the coefficients of linear expansion leads to the destruction of the product as a result of compression of the forming matrix. To avoid destruction, a complex product is often divided into simple elements and manufactured separately. In the future, they are assembled.

Such a technological process leads to a rise in the cost of production of the product, and in some cases to a decrease in its technical parameters. In order to carry out the manufacturing process of monolithic spatial structures of complex shapes from a hot hardening composite in a forming matrix having different linear expansion coefficients with the composite, according to the claimed invention, it is proposed to remove the product at a temperature close to the lower boundary of the polymerization temperature range without cooling it.

However, at the indicated temperature, the composite does not have high mechanical characteristics and removal of the product at this temperature, generally speaking, can lead to loss of shape of the product or its complete destruction, especially if the complex product being manufactured consists of thin elements that form an extended spatial structure. To correct the shape of such products, according to the invention, it is proposed to carry out a thermal correction process, which consists in heating the product to a temperature higher than the glass transition temperature of the binder, but below the temperature of its destruction, while simultaneously supporting the product on base surfaces lying in parallel planes, with further cooling of the product in like that. At a temperature of destruction, the properties of the material as a binder are violated.

The essence of the claimed invention is illustrated by specific examples of the device for implementing the proposed method, in particular on the example of the reference truss of the channel of the charged particle accelerator, and is illustrated in Fig.1-6.

The manufacturing process of the carbon composite trihedral truss begins with the preparation of the molding tool (Figure 1). This tool consists of three internal punches of the same shape 1, 2, 3, an external matrix made in the form of a base 4 and two side elements 5, 6, as well as a silicone chamber in the form of a tube with a fitting 7, which simultaneously serves as a pressure generating device from the inside, and can be connected to the compressor through the nozzle. The punches and the outer matrix have grooves that are filled with a semi-finished composite material (prepreg) during the assembly of the device. As an example, FIG. 2 shows grooves (more clearly).

The assembly of the device begins with the screws connecting the two side elements 5 and 6 (Figure 1) of the matrix along their entire length, which are fixed in position with support on a screwed edge - a position in the form of the letter "V". In the open part one of the punches 1 is laid with a prepreg laid along it. A round silicone chamber with a fitting is superimposed on this punch. Between the camera and the side elements of the matrix, the remaining two punches 2 and 3 with a prepreg are stacked. In figure 3. shows a partially assembled device, the designation of the elements on which corresponds to the designations in figure 1. Additionally shown is a longitudinally laid prepreg 8. Next, the device is closed by a base 4 (FIG. 1) with a prepreg laid in grooves and screwed. The end surfaces of the assembly are closed with metal plates to avoid extrusion of the silicone chamber when air is being pumped from the compressor. The arrangement of all the assembly elements in the cross section is shown in Figure 4, on which: 1 - the punch element, which is laid first during the assembly process, 2, 3 - other punch elements, 4 - the matrix base on which the device is placed after assembly, 5, 6 - lateral elements of the matrix, 7 - silicone chamber, 8 - two longitudinal elements of the product, 9 - longitudinal element, the prepreg of which is laid first when assembling the device with the punch element 1. Three heating elements 10 are attached to the external elements of the matrix 4, 5 and 6 Appearance of devices -keeping for manufacturing articles in the form of truss is illustrated in Figure 5. together with a processor that sets the required temperature mode of polymerization.

In the manufacture of the farm, an M55JB brand carbon prepreg was used, which has the desired properties, which were mentioned above. For additional fixation of the prepreg in the grooves, a Teflon film 10-30 μm thick was glued onto the middle part of the plane of each matrix element.

When the operating temperature is reached, the compressor is switched on and the carbon reinforcement is compressed. Working pressure is about 3 kg / cm ² . The pressure in the silicone chamber is held for at least 1 hour (i.e. until the glass transition of the binder). The polymerization process for the epoxy binder used at a temperature of 125 ° C lasts 2 hours from the moment the temperature “exits” when heated to its nominal value.

An important feature of the process is that disassembly is carried out without disconnecting the electric heaters located on the outer planes of the matrices from the power supply, and thus the operating temperature is maintained, which ensures that the carbon composite truss is preserved from destruction during matrix cooling.

The manufacturing process ends with the removal of the finished farm. For this, a partial disassembly is carried out, namely, the pressure relief in the silicone pipe to zero, unscrewing the end plates and pulling the rubber chamber. Next produce:

- pulling three punches, because their smooth surfaces and their shape make it possible,

- further disassembly of the matrix. To do this, turn the assembly into position “V” with the base up and unscrew all the screws securing the base. The base (at this stage) is not removed.

- loosening of the screws tightening the lateral matrix elements until a gap is formed between the contacting surfaces,

- removal of the base and excavation of the finished carbon composite farm, because the lateral elements of the matrix after loosening the screws have a small "camber" and do not interfere with removal.

The peculiarity and uniqueness of the claimed invention lies in the fact that it solves the problem of creating radiation-transparent spatial structures intended for the precise placement of large arrays of position-sensitive nuclear radiation detectors in the channel of a charged particle accelerator. High thermomechanical properties of the supporting structure were provided. The minimum allowable quantities of the substance with the required atomic number ensured the radio transparency of this design. The manufacturing technology of monolithic ultralight structures of a given shape from carbon fiber was implemented for the first time. The problem itself arose in connection with the development of the central part of the experiment — a charged particle accelerator at the Large Hadron Collider (studies were conducted within the framework of the well-known International ALICE Project of the CERN European Nuclear Center), of which Russia is one of the participants, including one of the performers of which is the Applicant (St. Petersburg State University), where it was required to ensure the necessary radiation transparency of the ALICE internal track system. The contribution of carbon fiber support structures to reducing transparency was no more than 0.2%. Tests of the claimed invention (mechanical - for deflection and deviations from geometric parameters at the required weight load) were carried out at the Central Design Bureau of Mechanical Engineering (TsKBM) and the All-Russian Research Institute of Metrology (VNIIM) of St. Petersburg with the direct participation of the Applicant (SPbU), and thermal tests for thermomechanical stability were performed in one of the laboratories of CERN (Switzerland) with the direct participation of the authors of the claimed invention.

The claimed invention can be used for the manufacture of products of complex shape on the example of the above farm. From the above example, it is seen that in the manufacture of products of complex shape, the choice of materials, the relative position of the elements of the matrix, punch and pressure generating device are important. The departure from the traditional concept of the appointment of a punch as an element that creates only pressure expands the choice of the possible shape of the product. This is possible by creating an appropriate profile of the surface of the punch in contact with the product, which makes it easier to remove the finished product. New opportunities open up when using not one, but several devices that create pressure.

The invention has a wide scope of application: elements, components, systems, parts of equipment, instruments and devices used in space and aviation developments. These can be elements and systems of space telescopes, antennas, mirrors, large solar panels, ultralight manipulator elements, radiation-transparent devices for hadron therapy, for example, a carbon fiber patient chair, and many other products used in medicine for diagnostics and treatment.

Information sources

1. RF patent No. 2101262, cl. СВВ 35/563, 1996.

2. RF patent No. 2191720, cl. B64G 1/22, 2000.

3. RF patent No. 2152505, cl. ЕВВ 19/084, 1999.

4. RF patent No. 2113379, class. B64C 27/473, 1993.

5. RF patent No. 2300675, cl. F16G 1/28, 2003.

6. RF patent №2242369, cl. B32B 3/12, 2003.

7. RF patent No. 2223860, cl. B29C 53/56, 2002 (prototype method).

8. Patent EP 1659331, cl. F17C 1/06, 2004.

9. Patent EP 1578301, cl. A61C 13/01, 2003.

10. Patent EP 1686208, cl. D04H 3/00, 2004.

11. RF patent №2323058, cl. B21D 51/10, 2006 (prototype device).

Claims (3)

1. A method of manufacturing carbon composite products, including the assembly of the mandrel, laying the fittings in the form of coal tows on a fixed mandrel along its longitudinal axis, impregnation with a polymer binder material and heating to a temperature that excludes difficulties when removing the finished product, characterized in that the finished product is removed at a temperature close to the lower boundary of the temperature range of the polymerization, and the polymer binder material is selected with a glass transition temperature above and close to the lower boundary of the temperature interval shaft polymerization. 2. The method according to claim 1, characterized in that to correct the finished product having an increased deviation from the nominal value, this product is clamped between the base flat surfaces located in parallel planes, heated to a temperature lying in the range above the glass transition temperature of the polymer binder , but below the temperature of its destruction, and carry out the cooling process of the product in this position. 3. A device for the manufacture of carbon composite products having the shape of a truss, including a workpiece, a die, an inner punch and a device that creates pressure from the inside, characterized in that the inner punch is made of three elements, the shape of which corresponds to the shape of the device that creates pressure from the inside, and the longitudinal profile truss elements, the matrix consists of three elements, the profile of which corresponds to the profile of the transverse truss elements, and the device that creates pressure from the inside is made in the form of a silicone chamber with a fitting That can be connected to the compressor.

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