DE112022000159T5 - Fastening screws made from a two-dimensional carbon-carbon composite material produced by laminating anisotropic non-woven fabrics - Google Patents

Abstract

The invention provides a fastening screw made of a two-dimensional carbon-carbon composite material prepared by laminating short carbon fibers using anisotropic non-woven fabrics, wherein the direction of the central axis of the fastening screw is aligned so that this direction of the Y-direction of the two-dimensional carbon-carbon -composite material with an anisotropic property.

Description

field of invention

The present invention relates to two-dimensional carbon-carbon composite fastening screws made by laminating anisotropic non-woven fabrics.

Technical background of the invention

Since a carbon-carbon composite (referred to simply as “C/C composite” or “C/C material”) has a strength and modulus several times higher than that of a conventional carbon or Graphite material, and moreover is lighter in weight than the carbon or graphite material and superior in heat resistance, wear resistance, toughness and thermal conductivity, it has been used as a material for the nozzle of a solid fuel engine, for the nose cone of an ICBM, and for the nose cone and the Leading edge of Space Shuttle wings used.

As mentioned earlier, due to its excellent properties, the carbon-carbon composite material has been used in brakes of airplanes, racing cars, the Shinkansen bullet train and wide-body and heavy-duty vehicles, structural members, pans and heating elements in heat treatment furnaces, forks for handling products in manufacturing furnaces semiconductors and solar cells, and metal processing devices in high-temperature environments. The carbon-carbon composite material is very popular and is usually used in industrial fields.

As mentioned above, with the general use of the carbon-carbon composite in industrial fields, it is necessary to have threaded fasteners for connecting carbon-carbon composite parts or for connecting one carbon-carbon composite part to another To use a part made of a material other than carbon-carbon composite.

In high-temperature environments where carbon-carbon composite parts are applied, even if heat-resistant steel fastening bolts are used, there are problems that sufficient strength cannot be obtained or insufficient strength due to the phenomenon caused by high-temperature creep durability can be achieved. Therefore, in order to connect such parts, fastening bolts made of carbon-carbon composite material have been used (see Patent Document 1).

• (1) Herstellen eines Prepregs durch Auftragen eines Phenolharzes auf ein Flachgewebe unter Verwendung von Kohlenstofffaser-Spinnfäden oder Kohlenstofffaser-Filamenten, und Schneiden des Prepregs mit vorbestimmten Abmessungen
• (2) Laminieren mehrerer der Prepregs und Formen bei 160°C durch eine Heißpresse, um eine Dicke von 20 mm zu erhalten
• (3) Durchführung der Wärmebehandlung (Karbonisierung) durch Erhitzen des geformten Körpers auf 800°C
• (4) mehrmaliges Wiederholen einer Tränkungsimprägnierung und der Wärmebehandlung und Durchführen der Wärmebehandlung (Graphitierung) durch Erhitzen auf 2.000°C als letzte Wärmebehandlung, um Platten aus dem 2D-Kohlenstoff-Kohlenstoff-Verbundmaterial zu erhalten
• (5) Herstellung von Vollgewindebolzen durch Bearbeitung der Platten aus dem 2D-Kohlenstoff-Kohlenstoff-Verbundwerkstoff
• (6) In diesem Fall wird der Bolzen so bearbeitet, dass die Richtung der Mittelachse des Bolzens der Kett- oder Schussrichtung des Flachgewebes entspricht (siehe 1 des Patentdokuments 1).

The fastening bolts made of a 2D (two-dimensional) carbon-carbon composite disclosed in Patent Document 1 are manufactured by the following methods (see paragraphs [0019] and [0020] of Patent Document 1):

• (1) Preparing a prepreg by applying a phenolic resin to a flat fabric using carbon fiber strands or carbon fiber filaments, and cutting the prepreg to predetermined dimensions
• (2) Laminating a plurality of the prepregs and molds at 160°C by a hot press to have a thickness of 20mm
• (3) Conducting heat treatment (carburization) by heating the molded body to 800°C
• (4) Repeating soaking impregnation and the heat treatment a number of times, and performing heat treatment (graphitization) by heating at 2,000°C as the final heat treatment to obtain 2D carbon-carbon composite material sheets
• (5) Manufacture of fully threaded bolts by machining the plates of the 2D carbon-carbon composite
• (6) In this case, the bolt is processed so that the direction of the central axis of the bolt corresponds to the warp or weft direction of the flat weave (see 1 of patent document 1).

As for the fastening bolts made of the 2D (two-dimensional) carbon-carbon composite material by the manufacturing methods explained above, the bolts are made of the plates of the 2D carbon-carbon composite material laminated with the carbon fibers on the flat fabrics, so machined so that the direction of the central axis of the bolt corresponds to a warp or weft direction of the flat weaves. As a result, the pin has the properties that the mechanical properties, such as strength and Young's modulus, and the thermal properties, such as thermal expansion coefficient, in the direction of the center axis of the pin are the same as in the direction perpendicular to the center axis of the pin and parallel to the lamination plane of the flat weave.

State of the art

patent specification

Patent Document 1: Japanese Patent Laid-Open Publication No. 2001-289226

Summary of Inventions

Problems to be solved by the inventions

However, the fastening bolts made of the above two-dimensional carbon-carbon composite material have a problem that the carbon fibers do not sufficiently contribute to the flexural strength of the webs of the fastening bolts, so that the bolts (the fastening bolts) cannot have sufficient strength.

Since the coefficient of thermal expansion of carbon fibers is negative in the fiber direction, the coefficient of thermal expansion of the carbon-carbon composite is extremely small compared to that of graphite or heat-resistant steel. In addition, the coefficient of thermal expansion of the carbon-carbon composite material has an anisotropic property depending on an orientation ratio of carbon fibers, and the coefficient of thermal expansion in a high orientation ratio direction is smaller than that in a low orientation ratio direction.

When the parts made of materials other than the carbon-carbon composite, such as the graphite or the heat-resistant steel, are connected by the fastening bolts made of the carbon-carbon composite, in a harsh environment with a large temperature change and a high temperature when the fastening bolts made of the above two-dimensional carbon-carbon composite material are used because of the difference between the coefficient of thermal expansion of the materials such as graphite or heat-resistant steel and that in the axial direction of the fastening bolts made of the carbon-carbon composite material is large, there arise problems such as the mounting bolts being damaged by the excessive thermal stress caused in the mounting bolts or the mounting bolts loosening at the mounting position by a large change in ambient temperature.

Furthermore, in the above fastening screws made of the two-dimensional carbon-carbon composite material, since the two-dimensional carbon-carbon composite material is made of a flat weave of carbon fiber strands or carbon fiber filaments, the manufacturing cost of the two-dimensional carbon-carbon composite material increases. As a result, there is a problem that the manufacturing cost of the fastening bolts made of the two-dimensional carbon-carbon composite material also increases.

The present inventions have been made against the background of the technical background described above, and the problem to be solved by the present inventions is to provide fastening screws made of a two-dimensional carbon-carbon composite material which have high strength by reducing the degree of contribution of the Carbon fibers to increase the strength of the mounting screws. Further, the problem to be solved by the present invention is to provide fastening bolts made of a two-dimensional carbon-carbon composite material, which can prevent the damage of the fastening bolts made of the carbon-carbon composite material by the thermal Stress caused by the large temperature change in the environment where the fixing screws are used is reduced, and which can reduce loosening at the fixing point.

Further, the problem to be solved by the present invention is to provide the fastening bolts made of the two-dimensional carbon-carbon composite material having the characteristics described above at a low cost.

means of solving the problems

In order to solve the above problems, the first aspect of the invention relates to a fastening screw made of a two-dimensional carbon-carbon composite material made by laminating anisotropic non-woven fabric using short carbon fibers,
wherein the direction of the central axis of the fixing screw is aligned so that the direction corresponds to the Y-direction of the two-dimensional carbon-carbon composite material having the anisotropic property,
wherein the two-dimensional carbon-carbon composite material is made by laminating so that the "main orientation direction" of the anisotropic nonwoven fabrics are aligned in one direction, and the direction of the two-dimensional carbon-carbon composite material corresponding to the "main orientation direction" of the anisotropic nonwoven fabrics as is defined as the X direction, and the direction of the two-dimensional carbon-carbon composite material, which corresponds to the “sub-orientation direction” of the anisotropic nonwoven fabrics, is defined as the Y direction,
wherein the direction of the anisotropic non-woven fabrics in which the large number of short carbon fibers are oriented is defined as a "major orientation direction" and the direction of the anisotropic non-woven fabrics in which the small number of short carbon fibers are oriented is defined as a "sub-orientation direction". .

The second aspect of the invention also relates to the fastening screw according to the first aspect of the invention,
wherein a ratio of the flexural strength in the X direction of the two-dimensional carbon-carbon composite material having the anisotropic characteristic to the flexural strength in the Y direction satisfies the following formula: $$\left[\text{Bending strength in X}-\text{Direction}\right]/\left[\text{Bending strength in Y}-\text{Direction}\right]>1.5$$

Furthermore, the third aspect of the invention relates to the fastening screw according to the first or the second aspect of the invention,
wherein a ratio of the X-directional tensile modulus of elasticity of the two-dimensional carbon-carbon composite material having the anisotropic characteristic to the Y-directional tensile modulus of elasticity of the composite material satisfies the following formula: $$\left[\text{tensile elasticity}\ddot{\text{a}}\text{tsmodule in X}-\text{Direction}\right]/\left[\text{tensile elasticity}\ddot{\text{a}}\text{tsmodul in Y}-\text{Direction}\right]>1.5$$

Furthermore, the fourth aspect of the invention relates to the fastening screw according to one of the first to third aspects of the invention,
wherein a ratio of the thermal expansion coefficient in the X direction of the two-dimensional carbon-carbon composite material having the anisotropic characteristic to the thermal expansion coefficient in the Y direction that satisfies the following formula: $$\begin{array}{l}\left[\text{thermal expansion coefficient in X}-\text{Direction}\right]/[\text{thermal expansion co}-\\ \text{efficient in Y}-\text{Direction}]<0.8\end{array}$$

Effects of the invention

In the present invention, since the fastening bolts are made of the two-dimensional carbon-carbon composite plates by laminating the anisotropic mats using the short carbon fibers, it is possible to make the fastening bolts of the 2D (two-dimensional) carbon-carbon composite material lower cost than by laminating the conventional flat fabrics using the carbon fiber strands or the carbon fiber filaments.

In the fastening screws of the present invention, since the direction of the central axis of the fastening screws is oriented so that this direction corresponds to the Y direction (in which a small number of short zen carbon fibers) of the two-dimensional carbon-carbon composite material having the anisotropic property, it is possible to increase the degree of contribution of the carbon fibers to the bending strength of the webs, and consequently the strength of the bolts (the fastening screws) can be improved.

In the fastening screws of the present invention, since the direction of the central axis of the fastening screws is oriented to correspond to the Y-direction (in which the few short carbon fibers are oriented) of the two-dimensional carbon-carbon composite material having the anisotropic property, it is possible to to provide fastening bolts made of two-dimensional carbon-carbon composite material, which can prevent the damage at the fastening points by the fastening bolts by reducing the thermal stress caused by the large temperature change in the environment where the fastening bolts are used and which the Loosening at the attachment point can reduce.

character list

• [ 1 ] 1 Fig. 12 is a flow chart showing methods for producing anisotropic nonwoven fabrics using short carbon fibers by intentionally changing the orientation ratio of the fibers according to the in-plane direction of the nonwoven fabrics.
• [ 2 ] 2 Fig. 12 is a flow chart showing processes for manufacturing a laminated body of a two-dimensional carbon-carbon composite material using the anisotropic nonwoven fabrics.
• [ 3 ] 3 Fig. 12 shows the laminated body of the two-dimensional carbon-carbon composite material made by laminating the anisotropic nonwoven fabrics using the short carbon fibers and a bolt (a fully threaded bolt) made by cutting out the laminated body and machining.
• [ 4 ] 4 shows the cross-section perpendicular to the central axis (the in 5 shown cross section BB) of the bolt (the fully threaded bolt) made of the two-dimensional carbon-carbon composite material, which is obtained by laminating the in 3 shown anisotropic nonwovens was produced.
• [ 5 ] 5 shows the in 4 AA cross-section shown (the cross-section along the center axis of the bolt) of the bolt (the fully threaded bolt) made of the two-dimensional carbon-carbon composite material made by laminating the anisotropic nonwoven fabrics.
• [ 6 ] 6 shows the device for testing the thermal load capacity of the bolt (the fully threaded bolt).

Detailed description of the embodiments

The embodiments of the present invention are explained below with reference to the figures. The embodiments discussed herein are merely illustrative of the present inventions and do not limit the scope of the present inventions.

First, the methods for producing the anisotropic nonwoven fabrics of the present invention using the short carbon fibers will be explained.

1 Fig. 12 is a flow chart showing the manufacturing processes of the anisotropic nonwoven fabrics of the present invention using the short carbon fibers.

• Schritt 11 zur Herstellung einer gemischten Lösung (eine dispergierende Flüssigkeit, die die Kohlenstofffasern enthält);
• Schritt 12 zur Bildung einer Bahn durch Gießen der gemischten Lösung auf ein Netz eines Maschenförderers; und
• Schritt 13 zum Trocknen der die Kohlenstofffasern verwendenden Bahn.

The processes for producing anisotropic nonwoven fabrics using the short carbon fibers include the following steps:

• Step 11 of preparing a mixed solution (a dispersing liquid containing the carbon fibers);
• step 12 of forming a web by pouring the mixed solution onto a net of a mesh conveyor; and
• Step 13 of drying the web using the carbon fibers.

Incidentally, the dispersion liquid contains a binder to bind the carbon fibers in drying the web using the carbon fibers.

Step 11 of preparing a mixed solution (a dispersion liquid containing the carbon fibers) will be explained below.

As carbon fibers used in the present invention, polyacrylonitrile-based (PAN-based) carbon fibers and pitch-based carbon fibers can be used, and all kinds of fibers treated with flame retardancy, carbonization and graphitization can be used. Short carbon fibers are used in the present invention, with carbon fibers having a length of 1 - 50 mm being preferred. The carbon fibers with a length of 1 - 25 mm are more preferable. However, the length of the carbon fibers is not limited to these.

Further, carbon fibers made by mixing the PAN-based carbon fibers with the pitch-based carbon fibers in a predetermined ratio can be used, and carbon fibers made by combining the carbon fibers treated by the flame retardant treatment, the carbonization, and the graphitization treatment were, can be used.

In commercial carbon fibers, a surface oxidation treatment such as an electric field surface treatment is applied to the surface of the carbon fibers in order to improve the adhesive property between the carbon fibers and a matrix resin in forming a composite material. Further, a sizing agent having epoxy group, hydroxyl group, acrylate group, methacrylate group, carboxyl group or carboxylic acid anhydride group is applied to the surface of the carbon fibers to bind the carbon fibers into carbon fiber bundles.

In the case of the carbon fibers used in the present invention, the surface treatments or sizing agents explained above may be applied to the fibers. The carbon fibers can also be used in such a way that the effects of surface treatments or sizing agents are eliminated.

The proportion by weight of the binder used in the webs of the present invention is, for example, 5-30% by weight using the agent for binding the short carbon fibers together.

As such binders, carboxymethyl cellulose (CMC), water-soluble polyacrylic resin, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, polyester, sodium alginate, dextrin, gelatin, polyvinyl alcohol, etc. can be used.

These binders are decomposed and converted into carbonaceous material by heating at high temperature (e.g. carbonization at more than 400°C). The conversion efficiency from the binders to the carbonaceous material is low. However, since the generated carbonaceous material is distributed homogeneously around each opened carbon fiber and binds the carbon fibers together, the shape of the starting material is definitely maintained even after carbonization.

Since most of the binders are gasified and scattered during the carbonization treatment, the carbonaceous material which is the carbonization product of the binder exists around the carbon fibers, having many voids and being porous.

In the preparation of the mixed solution, the opened (short) carbon fibers and the dispersion liquid composed of the binder and water or an organic solvent such as e.g. B. alcohol, is placed in a certain ratio in a container and then stirred. This creates a mixed solution in which the carbon fibers are homogeneously distributed.

In order to homogeneously disperse the carbon fibers in the mixed solution, it is possible to install an ultrasonic transducer on a wall of the tank and vibrate the mixed solution.

In Step 12 of forming sheets by pouring the mixed solution onto the net of the mesh conveyor, the mixed solution prepared in Step 11 (the dispersing liquid which the Koh containing cellulose fibers) is transferred from the container to a papermaking apparatus by applying pressure, and the webs are produced. As the papermaking apparatus, a Fourdrinier machine, a cylinder machine, a Yankee machine, a twin wire machine and other types of paper machines can be used. The following explains the methods of web formation using the Fourdrinier machine.

In the web forming methods using the Fourdrinier machine, the mixed solution in which the carbon fibers are homogeneously dispersed is fed from the tank into a feeder by pressurization. The feeding device can form a thin, homogeneous and flat sheet on the net because only the dispersing liquid falls through the net of the mesh conveyor when the mixed solution is poured onto the net. Thus, in general, in step 12, the (short) carbon fibers are aligned in random directions and intertwined, and a continuous web of carbon fibers is formed with the binder and the remainder of the dispersion liquid around the carbon fibers. In this step, the dispersing liquid falls through the mesh due to gravity, and most of the dispersing liquid falls.

Further, it is possible to press the endless web containing the residual dispersion liquid to remove the dispersion liquid by various methods after the web is formed by pouring the mixed solution onto the net of the mesh conveyor.

Next, step 13 for drying the web using the carbon fibers will be explained. In the web using the carbon fibers formed by the step 12 of forming the web by pouring the mixed solution onto the net of the mesh conveyor, since the dispersion liquid is not completely removed, the rest of the dispersion liquid is further removed by various methods. For example, it is possible to dry the wet web containing the dispersion liquid by pressing it against a steel drum (cylinder) heated with steam.

Through the steps explained above, the endless web using the (short) carbon fibers is completed. In the conventional endless web using the carbon fibers and manufactured through these steps, the carbon fibers (short) are aligned in random directions and intertwined with each other, and the binders are arranged around the carbon fibers. In addition, the nonwoven fabrics in the continuous web state have a predetermined tackiness due to the remaining binders. After passing through the paper machine, the non-woven fabrics are wound up in a roll or cut into a suitable size in the state of the continuous sheet produced as described above, so that a release paper can be interposed between the non-woven fabrics, if necessary. Then the non-woven fabrics are finished.

In the conventional nonwoven fabrics using the carbon fibers as described above, the short carbon fibers are aligned in random directions in the two-dimensional plane (in the plane of the nonwoven fabrics), so that the mechanical and thermal properties of the carbon fiber nonwoven fabrics in the Level of nonwovens do not have anisotropic properties, but isotropic properties. However, it is possible to produce the non-woven fabrics using the carbon fibers and having anisotropic properties by controlling the processes of the non-woven fabrics.

The non-woven fabrics used for the two-dimensional carbon-carbon composite of the invention are produced by the following method. Namely, the conventional non-woven fabrics are made such that a large number of short carbon fibers are unequally aligned in a papermaking direction (the moving direction of the web of the papermaking apparatus) by adjusting the vertical falling speed of the mixed solution V _L toward the surface of the web and the speed of the web V _P is controlled in step 12 to form the web by pouring the mixed solution onto the net of the mesh conveyor. In this specification, the nonwoven fabrics in which a large number of carbon fibers are intentionally and unevenly aligned in a certain direction are referred to as "anisotropic nonwoven fabrics using carbon fibers" or simply "anisotropic nonwoven fabrics".

Further, in the sheet-shaped anisotropic nonwoven fabric, the direction in which a large number of the carbon fibers are unevenly oriented is referred to as "major orientation direction", and the direction perpendicular to the "major orientation direction" is referred to as "sub-orientation direction".

In the conventional non-woven fabric using the carbon fibers and having nearly isotropic properties, the carbon fibers are bent in every direction. In the anisotropic nonwoven fabrics explained above, however, a large number of carbon fibers intentionally and unevenly oriented in a certain direction, ie, the carbon fibers oriented in the "main orientation direction" are arranged in an almost straight line without being bent.

In the anisotropic nonwoven fabrics explained above, since the ratio of orientation of the carbon fibers has the anisotropic property, the degree of bending of the carbon fibers in the direction in which a large number of carbon fibers are aligned decreases, and these fibers become in an almost straight line arranged. Thus, when the carbon-carbon composites are produced using the anisotropic nonwoven fabrics, the (tensile and flexural) strength and the (tensile and flexural) modulus of elasticity of the carbon-carbon composites in the direction in which a large number of carbon fibers is greatly improved due to the synergistic effect of (a) the effect of aligning a large number of carbon fibers and (b) the effect of reducing the degree of bending of the carbon fibers.

The manufacturing processes of the carbon-carbon composite materials using the anisotropic nonwoven fabrics are explained below.

2 Fig. 12 shows the flow chart showing the processes for producing the carbon-carbon composite materials using the anisotropic webs of the carbon fibers.

In step 21 for laminating the anisotropic nonwoven fabrics, first, the anisotropic nonwoven fabrics made of the carbon fibers are cut to have a predetermined size. Then, a plate having a predetermined shape is formed by laminating a plurality of the nonwoven fabrics.

At this time, the direction of the anisotropic non-woven fabrics in which a large number of carbon fibers are unevenly oriented, namely the "main orientation direction" of the anisotropic non-woven fabrics, is aligned in the same direction, and the direction perpendicular to the direction in which a large number of carbon fibers are oriented non-uniformly oriented, namely the "secondary orientation direction" of the anisotropic nonwoven fabrics, is oriented in the other direction. The "main orientation direction" and the "secondary orientation direction" are therefore two directions that are orthogonal to one another and run along the laminate plane of the laminate body.

Next, step 22 of forming a laminated body using anisotropic nonwoven fabrics by heating and pressing will be explained. In step 22, a molded body at an earlier stage of the carbon-carbon composite materials (referred to as “preform” or “precursor”) is formed by heating and pressing the laminated body of the anisotropic nonwoven fabrics prepared in step 21.

In the step 22 of forming a laminated body of anisotropic nonwoven fabrics by heating and pressing, the process is performed to convert the binder, which is the organic material and contained in the anisotropic nonwoven fabrics, into the carbonaceous material, which is the inorganic material while the shape of the anisotropic nonwoven fabric laminated body is maintained.

When the carbon-carbon composites preform is formed by heating and pressing the laminated body having a plate-like shape, the laminated body of the carbon fiber nonwoven fabrics is sandwiched between the hot plates of a hot press and heated and pressed by the hot plates.

At this time, the heating temperature should be more than 400°C, and it is possible to convert the binder into the carbonaceous material by heating the laminated body at this temperature.

In the preform of the carbon-carbon composite materials, the binder that binds the short carbon fibers is converted into the carbonaceous material, and the carbonaceous material binds and holds each of the carbon fibers. Thus, it is possible to keep the preformed and plate-like shape of the preform.

In the heating process to form the carbon-carbon composite preform, part of the binders gasify and disappear, and other part of the binders remain as carbon substance-containing material back. This creates voids in the area where the binders outgas and disappear, and a porous material forms.

Next, Step 23 for melting and impregnating pitch or resin will be explained. Step 23 is carried out to fill carbon materials in the vacant holes and the microspaces created between the carbon fibers and to form the dense matrix by impregnating the pitch or the resin into the porous preform of the carbon-carbon composite materials.

First, in step 23, powder or chips of pitch or resin contained in a container are heated and melted. As the pitch used here, a coal tar pitch or a petroleum pitch can be used, and the pitch having high impregnation ability and high conversion efficiency from pitch to carbonaceous material is preferable. Further, as the resin, for example, a thermosetting resin such as a phenolic resin or a furan resin can be used, and the resin having high impregnation ability and high conversion efficiency from the resin to the carbonaceous material is preferable. However, the resin is not limited to the above resins.

Then, the molten pitch or resin is impregnated into the holes and microvoids explained above by dipping the carbon-carbon composite material preform into the container containing the molten pitch or resin.

At this time, it is possible to impregnate the molten pitch or resin into the preform of the carbon-carbon composite materials by setting the preform in the vacuum tank and pouring the molten pitch or resin into the vacuum tank. Further, after immersing the carbon-carbon composite preform in the molten pitch or resin, it is possible to forcibly inject the molten pitch or resin into the interior of the preform by applying pressure to the molten pitch or resin impregnate.

In step 24 of carbonizing the preform impregnated with the molten pitch or resin, the preform of the carbon-carbon composite material impregnated with the molten pitch or resin is heated to about 800°C - 1500°C using a carbonizing furnace and the Pitch or resin impregnated in the preform is converted into the carbonaceous material.

When the molten pitch or resin impregnated in the carbon-carbon composite material preform converts to the carbonaceous material, a part of the molten pitch or resin converts to the carbonaceous material and the other part of the molten pitch or the melted resin gasifies and disappears. In this way, the micro-holes reappear where the molten pitch or resin was impregnated.

In order to fill the microholes newly formed in the preform, step 23 for melting and impregnating the pitch or resin and step 24 for carbonizing the preform impregnated with the melted pitch or resin as explained above may be repeated one or more times.

According to the methods explained above, the carbon-carbon composites are finished.

In step 25 for graphitizing the carbon-carbon composites, it is possible, if necessary, to convert the carbon fibers and the carbon matrix of the carbon-carbon composites into graphite with an advanced crystal structure by carrying out the graphitization treatment of the finished carbon-carbon composites at about 2000° C - 2800°C is further carried out.

In the above description, it is explained that the anisotropic nonwoven fabrics comprise the short carbon fibers and the binder. However, you are not limited to these.

In step 11 for preparing the mixed solution, it is possible to further add kerosene and/or coke powder having no softening property, or the kerosene and/or to further add the coal binder pitch powder which has the softening property, and the petroleum and/or the coal coke powder which does not have the softening property.

Due to the above method, the kerosene and/or coal binder pitch powder having no softening property is scattered into the anisotropic non-woven fabrics and mixed with the binder, or the kerosene and/or coal binder pitch powder having the softening property, and the kerosene and /or the hard coal coke powder, which has no softening property, are sprinkled into the anisotropic non-woven fabrics and mixed with the binder.

As explained above, when manufacturing the carbon-carbon composites using the anisotropic nonwoven fabrics with the binder pitch powder and the coke powder, most or all of the binder pitch powder and the coke powder remain as the carbon matrix in the carbon-carbon composites during the heat treatment in the manufacturing processes . In this way, the density of the carbon-carbon composites can easily be increased. As a result, it is possible to reduce the number of repetitions of the step 23 for melting and impregnating the pitch or resin in the manufacturing processes of the carbon-carbon composite materials or to omit the step 23.

Next, the method of manufacturing the tightening screw 2 from the laminated body 1 of the two-dimensional carbon-carbon composites, which is manufactured by laminating the anisotropic non-woven fabrics using short carbon fibers, will be explained.

In this specification, a "fastening screw 2" is defined as a generic term for a "bolt 2", a "fully threaded bolt 2" and a "nut 2", etc.

The manufacturing method of the fully threaded bolt 2, which is an example of the fastening screw 2, will be explained below.

3 Fig. 12 shows the laminated body 1 of the two-dimensional carbon-carbon composites produced by laminating the anisotropic mats using short carbon fibers, and the fully threaded bolt 2 produced by cutting out the laminated body 1 and machining the same.

The laminated body 1 of the two-dimensional carbon-carbon composites produced by the methods using the anisotropic non-woven fabrics is formed by aligning the directions of the anisotropic non-woven fabrics. Thus, the laminated body 1 has the same directions as those of the anisotropic non-woven fabrics.

The directions of the laminated body 1 of the two-dimensional carbon-carbon composite materials used in the present invention are defined as follows.

The direction corresponding to the “principal orientation direction” of the two-dimensional carbon-carbon composite materials produced by lamination so that the “principal orientation direction” of the anisotropic nonwoven fabrics is aligned in one direction is defined as the X direction, and the direction that corresponds to the “sub-orientation direction” of the two-dimensional carbon-carbon composite material is defined as the Y-direction.

The full-threaded bolt 2 is made of the laminated body 1 of the two-dimensional carbon-carbon composite material having two directions, the X-direction and the Y-direction, so as to have the in 3 shown directions.

Namely, the center axis of the fully threaded bolt 2 corresponds to the Y direction of the laminated body 1, and the direction perpendicular to the center axis of the fully threaded bolt 2 corresponds to the X direction of the laminated body 1 (see 3 ).

The method of cutting out the raw material of the fully threaded bolt 2 from the laminated body 1 of the two-dimensional carbon-carbon composite and finishing the fully threaded bolt 2 by machining the raw material is not limited. It is possible to manufacture the fully threaded bolt 2 using known machines such as a band saw, a milling machine, a lathe, etc.

4 shows the cross section perpendicular to the central axis of the fully threaded bolt 2 produced as described above.

5 shows the cross-section AA (the cross-section along the central axis of the bolt) of the in 4 shown fully threaded bolt 2. The X-direction and the Y-direction of the laminated body 1 made of the two-dimensional carbon-carbon composite material are as in FIG 3 shown aligned.

In general, in the screw 2 made by machining the laminated body 1 of the carbon-carbon composites, the ribs in the in 4 In the areas P shown, the axial load of the screw 2. The same applies to the fully threaded screw 2 of the present invention.

In the fully-threaded screw 2 of the present invention, the “X-direction” (in which the large number of carbon fibers are aligned) of the laminated body 1 faces each other in the P regions. As a result, it is possible to increase the contribution of the carbon fibers to the strength of the stud bolt 2 and increase the strength of the stud bolt 2 drastically.

embodiments

The carbon-carbon composites having a plate-like shape were produced using the anisotropic nonwoven fabrics as explained above.

Using these non-woven fabrics as raw material, fully threaded bolts 2 of nominal sizes M8 and M12 were manufactured, and a static load test and a thermal load test for the bolts 2 were performed.

1. 1. Herstellungsverfahren von Kohlenstoff-Kohlenstoff-Verbundwerkstoffen mit plattenförmiger Gestalt unter Verwendung der (anisotropen) Vliesstoffe

Details on the manufacturing processes of the two-dimensional (plate-shaped) carbon-carbon composite materials and on these tests are explained below.

1. 1. Manufacturing method of carbon-carbon composite materials having a plate-like shape using the (anisotropic) non-woven fabrics

In this embodiment, the anisotropic nonwoven fabrics were made using the pitch-based and short carbon fibers so that the large number of the short carbon fibers were oriented unevenly in the papermaking direction. Thus, the amount of the carbon fibers oriented in the direction perpendicular to the papermaking direction decreased by the increased amount of the carbon fibers oriented in the papermaking direction. Thus, the papermaking direction corresponds to the "major orientation direction" of the anisotropic nonwoven fabrics, and the direction perpendicular to the papermaking direction corresponds to the "minor orientation direction" of the anisotropic nonwoven fabrics.

Incidentally, the anisotropic nonwoven fabrics used in this embodiment include only the carbon fibers and the binder and do not contain the binder pitch powder and the coke powder.

Further, the amount of the carbon fibers in the anisotropic nonwoven fabrics was controlled so that the content (volume fraction) of the carbon fibers in the final carbon-carbon composite materials was 40%.

In step 21 of laminating the anisotropic non-woven fabrics of the manufacturing method of the laminated body 1 of the two-dimensional carbon-carbon composite materials, the anisotropic non-woven fabrics were laminated so that the "major orientation direction" of the anisotropic non-woven fabrics corresponded to the X-direction of the laminated body 1 and the "sub-orientation direction" of the anisotropic nonwoven fabrics corresponded to the Y-direction of the laminated body 1.

Thus, the large number of carbon fibers were aligned in the X direction of the laminated body 1 and the small number of carbon fibers in the Y direction of the laminated body 1.

Step 23 for melting and impregnating the pitch or resin and Step 24 for carbonizing the preform were each carried out in sequence. Step 25 for graphitizing the carbon-carbon composite materials was carried out at 2500°C.

The specimens were cut from the five sheets of the carbon-carbon composite materials experimentally produced in the embodiment. Then, flexural strength, tensile elastic modulus and thermal expansion coefficient in X and Y directions were measured using the test pieces. The results of the measurements are shown in Table 1 (each measurement shows the average of the measurements of the five panels). Incidentally, the ratios of the flexural strength σ _x σ _y , the tensile elastic modulus E _x /E _y and the coefficient of thermal expansion α _x /α _y in the X and Y directions are also shown in Table 1. Table 1 Properties of the two-dimensional and anisotropic carbon-carbon composites positions X direction Y direction Flexural strength σ _x , σ _y 350MPa 140MPa Tensile elastic modulus E _x , E _y 75GPa 20GPa Coefficient of thermal expansion α _X , α _y 0.46×10 ^-6 1/K 0.62×10 ^-6 1/K Ratio of bending strength σ _x /σ _y 2.50 Ratio of tensile elastic modulus E _x /E _y 3.75 Ratio of thermal expansion coefficient 0.74

In the two-dimensional and anisotropic carbon-carbon composites produced in this embodiment, the flexural strength ratio and the ratio of tensile elastic modulus in the X-direction and Y-direction were 2.50 and 3.75, respectively. Thus, the anisotropic properties of more than 1.5, which could not be achieved by the two-dimensional carbon-carbon composite materials using the conventional isotropic nonwoven fabrics, were realized.

In addition, the ratio of the coefficient of thermal expansion in the X and Y directions was 0.74. That is, the anisotropic property of less than 0.8, which could not be achieved by the carbon-carbon two-dimensional composite materials using the conventional isotropic nonwoven fabrics, was realized.

Next, a comparative example will be explained. In the comparative example, the non-woven fabrics were manufactured so that the large number of carbon fibers were not oriented unevenly in a specific direction. Thus, the short carbon fibers were oriented approximately uniformly and scattered in the plane of the non-woven fabrics, and the non-woven fabrics had isotropic properties in the plane of the fabrics. Except for the above point, there was no difference between the manufacturing methods of the non-woven fabrics in the embodiment and the comparative example.

Furthermore, there was no difference between the manufacturing methods of the carbon-carbon composite materials with the plate-like in the manufacturing methods of the carbon-carbon composite materials with the plate-like shape of the comparative example, except for the point that the laminated body was made by laminating the isotropic nonwoven fabrics Shape in the embodiment and the comparative example.

Test pieces were cut from the five sheets of the isotropic carbon-carbon composite materials experimentally produced in Comparative Example. Then, using the test pieces, flexural strength, tensile elastic modulus and thermal expansion coefficient were measured.

The results of the measurements are shown in Table 2 (each measurement shows the average of the measurements of the five panels). Table 2 Properties of two-dimensional and isotropic carbon-carbon composites Characteristics flexural strength σ 190MPa Tensile Modulus of Elasticity E 40GPa Thermal expansion coefficient α 0.51×10 ^-6 1/K

2. Static load test for the bolts 2 (the fully threaded bolts 2)

In the exemplary embodiment, the bolts 2 (the fully threaded bolts 2) were machined from the two-dimensional and anisotropic carbon-carbon composite materials explained above in such a way that the bolts 2 in 3 have shown direction. Namely, the direction of the central axis of the fully threaded bolts 2 was aligned so that this direction corresponded to the Y-direction of the two-dimensional and anisotropic carbon-carbon composite materials. In the exemplary embodiment, the fully threaded bolts 2 were produced with the nominal sizes M8 and M12.

For comparison with the embodiment, the fully threaded bolts 2 of Comparative Example 1 and Comparative Example 2 were manufactured. In Comparative Example 1, the fully threaded bolts 2 with nominal sizes M8 and M12 made of the two-dimensional and anisotropic carbon-carbon composites explained above were machined so that the direction of the center axis of the fully threaded bolts 2 corresponded to the X-direction of the two-dimensional and anisotropic carbon-carbon composites .

Furthermore, in comparative example 2, the fully threaded bolts 2 with the nominal sizes M8 and M12 were produced from the two-dimensional and isotropic carbon-carbon composite materials explained in the comparative example.

Metal nuts 4 were attached to both ends of the fully threaded bolts 2 of nominal sizes M8 and M12 of the working example, comparative example 1 and comparative example 2, and the static load test (the tensile load test) for the fully threaded bolts 2 was performed by stretching the bolts 2 so that the nuts 4 were spaced apart along the central axis of the fully threaded bolts 2. The results of the test are shown in Table 3. Table 3 Results of the static load test for the fully threaded bolts 2 of the embodiment and comparative examples 1 and 2 positions Strength of the threaded part of M8 bolts Strength of the threaded part of M12 bolts Embodiment Screws 2 such that the direction of the central axis of the screws corresponds to the Y-direction (the “sub-orientation direction” of the carbon fibers) of the two-dimensional and anisotropic carbon-carbon composite material 211 kg 811 kg Comparative Example 1 Bolts 2 such that the direction of the central axis of the bolts corresponds to the X-direction (the “main orientation direction” of the carbon fibers) of the two-dimensional and anisotropic carbon-carbon composite materials 137 kg 549 kg Comparative example 2 Screws made of the two-dimensional and isotropic carbon-carbon composites 2 181 kg 692 kg

From these results, it can be seen that the fully threaded bolts 2 of the embodiment (bolts manufactured so that the direction of the central axis of the bolts corresponds to the Y-direction (the “sub-orientation direction” of the carbon fibers) of the two-dimensional and anisotropic carbon-carbon composites) have excellent strength compared to the fully threaded bolts 2 of Comparative Example 1 (bolts manufactured so that the direction of the central axis of the bolts is the X-direction (the "main orientation direction" of the carbon fibers) of the two-dimensional and anisotropic carbon-carbon composite materials corresponds) and Comparative Example 2 (bolts made of the two-dimensional and isotropic carbon-carbon composite materials).

3. Checking the thermal load capacity of the screws 2

The thermal load capacity test was carried out. The test specimens were the same screws as the fully threaded bolts 2 with the nominal sizes M8 and M12 of the design example (the bolts made of the two-dimensional and anisotropic carbon-carbon composites) used in the static load test, and the same bolts as the fully threaded bolts 2 of nominal sizes M8 and M12 of Comparative Example 2 (the bolts made of the two-dimensional and isotropic carbon-carbon composites) used in the static load test.

The thermal endurance test was performed according to the following procedure.

First, the fully threaded bolt 2 was inserted into a through hole in the center of an isotropic graphite spacer 3 as shown in FIG 6 1, and the nuts 4 made of the isotropic graphite were connected to both ends of the fully threaded bolt 2. Then the isotropic graphite spacer and nuts and fully threaded bolts of nominal size M8 or M12 were integrated by tightening the nuts to a specified torque.

The integrated test specimens were then heated to 1200°C and 2000°C in an inert gas atmosphere. After the integrated test specimens had cooled down to room temperature, the thermal load capacity of the fully threaded bolts 2 with the nominal sizes M8 and M12 was evaluated by means of an external check to determine whether the test specimens had been damaged.

The results of the thermal endurance test are shown in Table 4. Table 4 Results of the thermal load test of the fully threaded bolts 2 Size High temperature 1200°C 2000°C Embodiment Screws 2 such that the direction of the central axis of the screws corresponds to the Y-direction (the “sub-orientation direction” of the carbon fibers) of the two-dimensional and anisotropic carbon-carbon composite materials M8 No damage. No looseness No damage. No looseness M12 No damage. No looseness No damage. No looseness Comparative example 2 M8 bolts made of the two-dimensional and isotropic carbon-carbon composites 2. M8 The screws 2 were damaged. The nuts 4 were jammed. The screws 2 were damaged. The nuts 4 were jammed. M12 M12 screws 2 were damaged M12 bolts 2 were damaged Nuts 4 were jammed.

Assuming that the fully-threaded bolts 2 were assembled with the spacer 3 made of isotropic graphite, which has a coefficient of thermal expansion greater than that of the carbon-carbon composites by a factor of 1, the fully-threaded bolts 2 (bolts manufactured in such a way that the The direction of the central axis of the screws corresponded to the Y-direction (the "sub-orientation direction" of the carbon fibers) of the two-dimensional and anisotropic carbon-carbon composite materials) of the exemplary embodiment, although the integrated test specimens were exposed to large temperature differences (1200°C and 2000°C), neither damage nor loosening of the thread.

In contrast, in the fully threaded bolts 2 (made of the two-dimensional and isotropic carbon-carbon composite materials) of Comparative Example 2, damage to the thread due to the thermal stress was observed in all the test specimens.

The fully threaded bolts 2 of the exemplary embodiment are therefore superior to the fully threaded bolts 2 of comparative example 2 with regard to the thermal load capacity. In the fully threaded bolts 2 of the embodiment, the effect of reducing the thermal stress is remarkable.

The remarkable thermal stress reducing effect is considered to be due to the synergistic effect of the following two effects. First is thermal expansion coefficient in the central axis direction of the fully threaded bolts 2 of the embodiment is larger than that of the fully threaded bolts 2 of Comparative Example 2 and almost equal to the thermal expansion coefficient of the isotropic graphite spacer 3, and on the other hand, the tensile elastic modulus in the central axis direction of the fully threaded bolts 2 of the embodiment is smaller than that of the fully threaded bolt 2 of Comparative Example 2.

Reference List

1

laminated body of a two-dimensional and anisotropic carbon-carbon composite

2

Threaded fastener (a bolt, a fully threaded bolt and a nut)

3

spacers

4

Mother

11

Step to prepare a mixed solution

12

A step of forming a web by pouring a mixed solution onto a net of a mesh conveyor

13

Step of drying a web using carbon fibers

21

Step of laminating anisotropic non-woven fabrics

22

A step of forming a laminated body using anisotropic nonwoven fabrics by heating and pressing

23

Step of melting and impregnating a pitch or a resin

24

Step of carbonizing a preform impregnated with molten pitch or molten resin

25

Step of graphitization of carbon-carbon composites

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• JP2001289226 [0008]

Claims (4)

Fastening screw made of a two-dimensional carbon-carbon composite material made by laminating anisotropic non-woven fabrics using short carbon fibers, the direction of the central axis of the fixing screw is oriented so that this direction corresponds to the Y-direction of the two-dimensional carbon-carbon composite material with anisotropic characteristics, wherein the two-dimensional carbon-carbon composite material is made by laminating so that the "principal orientation direction" of the anisotropic nonwoven fabrics are aligned in one direction and the direction of the two-dimensional carbon-carbon composite material corresponding to the "principal orientation direction" of the anisotropic nonwoven fabrics is X -direction, and the direction of the two-dimensional carbon-carbon composite material, which corresponds to the "sub-orientation direction" of the anisotropic nonwoven fabrics, is defined as the Y-direction, wherein the direction of the anisotropic non-woven fabrics in which many short carbon fibers are oriented is defined as a “major orientation direction” and the direction of the anisotropic non-woven fabrics in which few short carbon fibers are oriented is defined as a “sub-orientation direction”. fastening screw claim 1 , where the ratio of the flexural strength in the X-direction of the two-dimensional carbon-carbon composite having the anisotropic property to the flexural strength in the Y-direction satisfies the following formula: $$\left[\text{Bending strength in X}-\text{Direction}\right]/\left[\text{Bending strength in Y}-\text{Direction}\right]>1.5$$

fastening screw claim 1 or 2 , where the ratio of the X-directional tensile modulus of elasticity of the two-dimensional carbon-carbon composite material having anisotropic characteristics to the Y-directional tensile modulus of elasticity satisfies the following formula: $$\left[\text{tensile elasticity}\ddot{\text{a}}\text{tsmodule in X}-\text{Direction}\right]/\left[\text{tensile elasticity}\ddot{\text{a}}\text{tsmodul in Y}-\text{Direction}\right]>1.5$$

Fastening screw with thread according to one of Claims 1 until 3 , where the ratio of the coefficient of thermal expansion in the X direction of the two-dimensional carbon-carbon composite material having anisotropic characteristics to the coefficient of thermal expansion in the Y direction satisfies the following formula: $$\begin{array}{l}\left[\text{thermal expansion coefficient in the X}-\text{Direction}\right]/[\text{thermal expansion}-\\ \text{voltage coefficient in the Y}-\text{Direction}]<0.8\end{array}$$

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