JPH08188469A - Composite material of silicon carbide matrix and fiber and its production - Google Patents

Abstract

PURPOSE: To obtain a composite material composed of silicon carbide matrix and fibers and having improved strength and fracture energy and high reliability by improving the distribution state of ceramic fibers in a fiber bundle as a micro-structure and setting the gap between the ceramic fibers to a suitable level. CONSTITUTION: This composite material 1a consisting of a silicon carbide matrix and fibers is composed of a reaction sintering silicon carbide matrix 4 and fiber bundles 3b obtained by bundling plural ceramic fibers 2 and arranged in the matrix. The average gap between the adjacent ceramic fibers 2 in the fiber bundle 3b is set to be >=1/2 of the diameter of the ceramic fiber 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon carbide (SiC) -based fiber composite material, and more particularly, to a silicon carbide-based fiber composite material having improved strength and fracture energy and having high reliability, and effective for obtaining the characteristics thereof. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Generally, a ceramic sintered body has little strength decrease up to a high temperature, and has various characteristics such as hardness, electric insulation, wear resistance, heat resistance, corrosion resistance, and lightness as compared with conventional metal materials. Since it is excellent, it is used in a wide range of fields as electronic materials and structural materials such as heavy electric equipment parts, aircraft parts, automobile parts, electronic devices, precision machine parts, and semiconductor device materials.

However, the ceramics sintered body is weaker in tensile stress than in compression, and has a defect of so-called brittleness, in which fracture progresses at a stretch under this tensile stress.
For this reason, in order to enable the application of ceramic parts to parts requiring high reliability, it is strongly required to increase the toughness and increase the fracture energy of the ceramic sintered body. .

That is, gas turbine parts, aircraft parts,
Ceramic structural parts used for automobile parts and the like are required to have high reliability in addition to heat resistance and high temperature strength.
For this reason, research on the practical application of ceramic-based composite materials in which composite materials such as fibers, whiskers, plates, and particles made of inorganic substances and metals are dispersed and composited in a matrix sintered body to increase the toughness value and fracture energy value, etc. It is being promoted in research institutions.

For example, several hundred to several thousand ceramic long fibers having a diameter of about 10 μm are usually bundled to form a fiber bundle (yarn), and the fiber bundle is arranged in a two-dimensional or three-dimensional direction to form one direction. Seat (UD seat: Uni-direction sh
eet) or various cloths, or by laminating the above-mentioned sheets or cloths, a preformed body (fiber preform) having a predetermined shape is formed, and inside the preformed body,
Forming a matrix by CVI (Chemical Vaper Infiltration method) or precursor impregnation / mineralization method, or filling the above-mentioned preform with ceramic powder by a casting method and then sintering. A ceramic-based fiber composite material has been developed in which a matrix is formed according to the above and the fibers are compounded in the ceramic matrix.

Here, the ceramic fiber has a diameter of 10
It is mass-produced as a fiber material having a size of about μm and is commercially available as a fiber bundle (yarn) obtained by bundling the fiber material in units of several hundreds to several thousands. The unidirectional sheet and various cloths (woven fabric) are formed by weaving the fiber bundle (yarn).

Therefore, as shown in FIG. 3, the conventional ceramic matrix fiber composite material 1 has a structure in which a fiber bundle 3 formed by bundling a large number of ceramic fibers 2 is arranged in a ceramic matrix 4 when viewed microscopically. Have. That is, the ceramic fibers 2 arranged in the composite material 1
The fiber bundle 3 in which several hundreds to several thousands are densely assembled is set as a unit and dispersed in the matrix 4.

[0008]

However, in the conventional ceramic-based fiber composite material in which the fiber bundles are arranged in the matrix as described above, the filling rate of the matrix in the densely gathered fiber bundles may be low. However, in the composite material as a whole, there are mixed ceramic fibers and monolithic parts with a high matrix fraction. It was In particular, the difference in the fracture mechanism between the fiber-rich portion and the monolithic portion increases to a non-negligible level, and the fracture energy of the material after cracking becomes small, resulting in a problem that high reliability cannot be obtained. .

In the conventional ceramic-based fiber composite material containing a plurality of ceramic fibers as a fiber bundle, most of the overall composite material structure defines a macroscopic structure such as a fiber volume ratio and a fiber directionality. Part,
As described above, there are very few examples in which various characteristics of the composite material are comparatively evaluated by defining the microstructure such as the distribution of the ceramic fibers and the matrix inside the fiber bundle.

According to the findings of the present inventors, the strength and fracture energy of the ceramic-based fiber composite material are not limited to the distribution state of the fiber bundle (yarn) as a macrostructure, but also within the fiber bundle as a microstructure. It is known that the distribution state of ceramic fibers (monofilament) is greatly affected. However, in the conventional method for manufacturing a composite material, since a fiber bundle in which a large number of ceramic fibers are tightly bundled in advance is used, the gap between the ceramic fibers inside the fiber bundle is controlled to be constant to form a microstructure. It was virtually impossible to prescribe. Therefore, since the matrix is not easily formed in the fiber bundle, the strength and fracture energy of the composite material based on the binding force between the fiber and the matrix and the slip resistance between the two become insufficient, and in any case, the entire composite material As a result, there is a problem that the durability is low and it is difficult to apply it to practical parts.

The present invention has been made to solve the above-mentioned problems, and particularly, to improve the distribution state of ceramic fibers in a fiber bundle having a microstructure and to properly set the gap between the ceramic fibers. Accordingly, it is an object of the present invention to provide a highly reliable silicon carbide-based fiber composite material having improved strength and fracture energy, and an effective manufacturing method for obtaining the structure.

[0012]

In order to achieve the above-mentioned object, the inventors of the present invention have made adjacent fibers within a fiber bundle in order to realize a microstructure in which a sufficient matrix is formed even inside the fiber bundle. Various methods of controlling the gap between the ceramic fibers were investigated. As a result, a plurality of ceramic fibers and carbon fibers or organic polymer fibers are bundled to form a fiber bundle (yarn), and the fiber bundle is used to form a preform (fiber preform). Silicon carbide (Si
C) When the matrix was formed, it became possible to arbitrarily adjust the gap between the adjacent ceramic fibers in the fiber bundle. In particular, when this gap is set to be equal to or larger than the radius of the ceramic fibers, it becomes possible for the first time to form a sufficient SiC matrix uniformly between the adjacent ceramic fibers in the fiber bundle, and the dispersed state of the ceramic fibers and the matrix becomes possible. It has been found that the variation of γ is reduced and the initial fracture strength of the composite material as a whole can be significantly improved. Further, since all the ceramic fibers constituting the fiber bundle form an interface with the matrix, all the ceramic fibers contribute to the increase in pull-out resistance of the ceramic fibers after the initial crack growth. Further, since the slip resistance at the interface between the ceramic fiber and the matrix is also increased, it was found for the first time that a silicon carbide-based fiber composite material with increased fracture energy can be obtained. The present invention has been completed based on the above findings.

That is, the silicon carbide-based fiber composite material according to the present invention is a silicon carbide-based fiber composite material in which a fiber bundle formed by bundling a plurality of ceramic fibers is arranged in a matrix made of reaction-bonded silicon carbide. It is characterized in that the average gap between adjacent ceramic fibers in the fiber bundle is set to ½ or more of the diameter of the ceramic fibers. Further, it is desirable to form a sliding layer made of boron nitride (BN) on the surface of the ceramic fiber. Further, the content ratio of the ceramic fibers in the composite material may be set to 5 to 55% by volume.

Here, silicon carbide (SiC) formed by a reaction sintering method is adopted as the ceramics constituting the matrix of the above-mentioned silicon carbide based fiber composite material. Generally, when a silicon carbide (SiC) sintered body is formed by a reaction sintering method, a raw material mixture of a carbon source such as carbon black powder and an aggregate component is formed into a predetermined shape, and the obtained formed body is obtained. Molten Si is impregnated into the compact while being heated to react the carbon source with the Si component to form a dense SiC sintered body.

However, in the present invention, carbon fibers or organic polymer fibers interposed between ceramic fibers are
It is used as a carbon source necessary for reaction sintering. That is, when the carbon fiber is reacted and sintered with the molten Si component, S
It becomes an iC matrix. On the other hand, organic polymer fibers can be carbonized by a simple heat treatment and converted into a carbon source necessary for reaction sintering. The carbonized organic polymer fibers also react and sinter with the Si component, and similarly become a SiC matrix.

Both the carbon fiber and the organic polymer fiber also have a function of controlling the gap between the adjacent ceramic fibers in the fiber bundle. That is, when the fiber bundle (yarn) is formed only by the ceramic fibers as in the prior art, the ceramic fibers 2 and 2 are in close contact with each other as shown in FIG. Alternatively, by interposing the organic polymer fiber, it is possible to easily secure a gap between the ceramic fibers in the fiber bundle. This gap value can be arbitrarily set by changing the compounding ratio of the ceramic fiber and the carbon fiber or the organic polymer fiber.

The carbon fiber and the organic polymer fiber interposed between the ceramic fibers finally become a SiC matrix by the reaction sintering of the Si component. Therefore,
A SiC matrix is sufficiently formed between the ceramic fibers in the fiber bundle, the initial fracture strength of the composite material as a whole can be enhanced, and the pull-out resistance and matrix of the ceramic fibers after the initial crack growth. It is possible to increase the slip resistance at the interface with
A SiC-based fiber composite material having a large breaking energy value can be obtained.

The fiber bundles arranged in the matrix are compounded in a predetermined amount in order to enhance the toughness of the composite material. The fiber bundle is prepared by bundling hundreds to thousands of fine ceramic fibers having a diameter of about 10 μm and carbon fibers or organic polymer fibers into a fiber bundle having a diameter of 0.1 to 1.0 mm. It is used as a unidirectional sheet, a cloth (woven fabric) or a preform (fiber preform) formed by knitting a fiber bundle in a two-dimensional direction or a three-dimensional direction. As the organic polymer fibers, various synthetic fibers such as polyester fibers and natural fibers can be used.

The material of the ceramic fibers constituting the fiber bundle is not particularly limited, and various ceramic fibers can be used. Specific examples of such ceramic fibers include silicon carbide-based fibers (Si
C, SiC-O, Si- Ti-C-O and the like), SiC-coated fibers (core wire, for example C), alumina fibers, zirconia fibers, boron fibers, silicon Motokei nitride fibers, Si ₃ N ₄ coated fibers ( The core wire includes, for example, C) and mullite fiber,
It is preferable to use at least one selected from these.

It is apparent from the experiments conducted by the inventors of the present application that the size of the average gap between the adjacent ceramic fibers in the fiber bundle has a great influence on the initial fracture strength, fracture resistance and peel strength of the composite material. Therefore, in the present invention, the average gap between the ceramic fibers is set to ½ or more of the diameter of the ceramic fibers. Here, the average gap between the adjacent ceramic fibers or the average gap between the closest ceramic fibers is, as shown in FIG. 2, the fiber bundle 3 exposed on the polishing surface of the vertical section of the fiber bundle in the composite material 1a.
It is assumed that 10 pairs of ceramic fibers 2 and 2 are sampled from b and are represented by the arithmetic mean of the gap values W1, W2, ... W10. When the average gap between the ceramic fibers in this fiber bundle is less than 1/2 of the ceramic fiber diameter, a sufficient carbon source cannot be arranged between the ceramic fibers, and reaction sintering causes It becomes difficult to form a sufficient SiC matrix, and it is difficult to obtain a composite material having high strength and breaking energy. On the other hand, when the average gap is set to 1/2 or more of the ceramic fiber diameter, the reaction-sintered SiC matrix formed between the ceramic fibers becomes sufficient, and the initial fracture strength of the composite material as a whole can be increased. Further, since all the ceramic fibers constituting the fiber bundle have a structure in which they are bonded to the SiC matrix, the sliding resistance at the interface also becomes large, and the fracture energy of the composite material can be increased.

The unidirectional sheet formed by knitting the fiber bundle, the fiber woven fabric, and the fiber preform are arranged in the matrix so that the fiber volume ratio (Vf) is 5% or more with respect to the whole composite material. . However, if the fiber volume ratio exceeds 55%, it becomes difficult to uniformly dispose the SiC matrix around each ceramic fiber, and the strength characteristics of the composite material are rapidly deteriorated due to the occurrence of defects such as voids. I will end up. Therefore, the preferable addition amount in which the fiber composite effect effectively appears is in the range of 20 to 40% by volume.

The diameter of the fiber bundle has a great influence on the dispersibility and orientation of the fiber bundle in the molded product and further on the strength characteristics of the composite material. In the present invention, the diameter is 0.1 mm.
Use ~ 1.0 mm continuous fiber bundles. If the diameter is less than 0.1 mm, the toughness improving effect is small, and the diameter is 1.0
If the fiber bundle is thicker than mm, the shape-imparting property may deteriorate, and it becomes difficult to effectively suppress the progress of cracks in a short region.

That is, by using a continuous fiber bundle having a diameter of 0.1 mm to 1.0 mm, it becomes possible to sufficiently secure the effect of improving the toughness by the fiber composite while maintaining a good shape imparting performance. However, if the volume percentage of such a fiber bundle is less than 5%, the toughness improving effect is not sufficiently exerted and the shape-imparting performance is also deteriorated. Therefore, the volume percentage of the fiber bundle may be 5% or more. preferable.

Further, in order to prevent strong adhesion due to the reaction between the ceramic fiber and the matrix or to improve the slippage at the interface between the two, a slipping layer having a thickness of about 0.05 to 2 μm is formed on the surface of the ceramic fiber. Should be formed. This sliding layer is formed by coating the surface of ceramic fibers with boron nitride (BN).

By the above-mentioned sliding layer, ceramic fibers and
The bond strength with the matrix is optimized, and due to this optimum bond strength, the holding strength after the initial fracture can be maintained high, and a composite material having a high toughness value can be obtained.

Further, a single layer having a thickness of 50 μm or more, which is made of only monolithic ceramics containing no fibers, is integrally formed on the entire surface of the composite material so that the fibers and the interface between the fibers and the matrix are not exposed on the surface. By doing so, it is possible to prevent oxidative deterioration and strength reduction due to the exposure of the fibers. Further, it is possible to prevent the slip function from being deteriorated due to the oxidation of the BN component constituting the slip layer formed on the fiber surface, and to effectively prevent the deterioration of the high temperature strength characteristics of the composite material. By forming the monolithic ceramic simple substance layer to a thickness of 500 μm or less, the strength reduction preventing function can be sufficiently exhibited.

The silicon carbide based fiber composite material in which the fiber bundles are arranged in the matrix is manufactured as follows, for example. That is, a method for producing a SiC-based fiber composite material using carbon fibers as a carbon source for reaction sintering, a fiber preform having a predetermined shape is formed by using a fiber bundle obtained by bundling a plurality of ceramic fibers and carbon fibers, A matrix starting material containing a silicon and a carbon source is impregnated into the fiber preform to form a molded article having a predetermined shape,
The molded body obtained is vacuumed or in an inert gas atmosphere.
Reacting and sintering silicon, a carbon source, and carbon fibers by heating in a temperature range of 400 to 1550 ° C. to form a matrix composed of silicon carbide, and integrally combining the fiber preform and the matrix. Is characterized by.

On the other hand, a method for producing a SiC-based fiber composite material using an organic polymer fiber as a carbon source for reaction sintering is as follows.
A fiber preform having a predetermined shape is formed by using a fiber bundle obtained by bundling a plurality of ceramic fibers and organic polymer fibers, and the matrix starting material containing a silicon and carbon source is impregnated into the fiber preform to obtain a predetermined shape. After forming a molded body and heat-treating the molded body in a temperature range of 500 to 1000 ° C. in a non-oxidizing atmosphere to carbonize the organic polymer fibers, 1400 in a vacuum or an inert gas atmosphere. By heating in a temperature range of ˜1550 ° C., silicon and carbon source and carbonized organic polymer fibers are reacted and sintered to form a matrix made of silicon carbide, and the fiber preform and the matrix are integrally combined. It is characterized by

[0029]

According to the silicon carbide-based fiber composite material and the method for producing the same according to the above-mentioned structure, the fiber bundle can be obtained by changing the compounding ratio of the ceramic fiber and the carbon fiber or the organic polymer fiber constituting the fiber bundle before sintering. It is possible to arbitrarily adjust the average gap between adjacent ceramic fibers. Especially, this average gap should be 1/2 of the ceramic fiber diameter.
Because of the above settings, it becomes possible for the first time to form a sufficient SiC matrix between the adjacent ceramic fibers in the fiber bundle. Therefore, the dispersion of the dispersion state of the ceramic fibers and the matrix is reduced, and the initial fracture strength of the composite material as a whole can be significantly improved. Further, since all the ceramic fibers forming the fiber bundle are bonded to the matrix, all the ceramic fibers contribute to the increase in pull-out resistance of the ceramic fibers after the initial crack growth. Further, since the slip resistance at the interface between the ceramic fiber and the matrix also increases, it is possible to provide a silicon carbide-based fiber composite material having an increased fracture energy.

[0030]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

Example 1 500 SiC continuous fibers having a diameter of 14 μm and a diameter of 10
500 μm carbon (C) fibers were bundled to form a fiber bundle (yarn), and a SiC continuous fiber bundle having a diameter of about 0.3 mm in which SiC fibers and carbon fibers were mixed was prepared. Further, this fiber bundle was knitted in a two-dimensional direction to prepare a number of plain weave cloth fabrics.

On the other hand, a mixed powder consisting of 70% by weight of SiC powder having an average particle size of 1.5 μm as an aggregate and 30% by weight of carbon powder having an average particle size of 0.1 μm as a carbon source was prepared, and this mixed powder was prepared. Water 64% to powder 35% by weight.
A matrix slurry was prepared by blending 5% by weight and 0.5% by weight of a dispersant.

Next, the fibrous woven fabric is cut into a square shape having a length of 50 mm and a width of 50 mm to form a large number of fabric pieces.
A preform (fiber preform) obtained by laminating 10 pieces of the woven fabric pieces was placed in a pressure casting mold having a cavity of 0 mm × 5 mm in depth. Next, the matrix slurry was cast into the preformed body under a pressure of 1 to 10 MPa to obtain a formed body.

The molded body 6 obtained as described above has a structure in which a preformed body composed of the fiber bundle 3a is arranged in the matrix molded body 7 as shown in FIG. A plurality of SiC continuous fibers 2 and carbon fibers 5 are mixed in the fiber bundle 3a, and the carbon fibers 5 interposed between the SiC continuous fibers 2 and 2 secure a gap between the adjacent SiC continuous fibers 2 and 2. ing.

Next, the obtained molded body is naturally dried and further degreased at a temperature of 600 to 800 ° C. for 2 hours, then placed in a baking container (sheath) filled with Si powder, and the temperature is 1420 ° C. in vacuum. Si melted in the compact after heating for 3 hours
The reaction sintering is carried out while impregnating the same, and the reaction sintering matrix composed of SiC and Si is synthesized inside and outside the molded body including the inside of the fiber bundle, and the SiC according to Example 1 as shown in FIG. A base fiber composite material 1a was prepared.

As shown in FIG. 2, the SiC-based fiber composite material 1a according to Example 1 has predetermined gaps W1 and W with respect to each other.
A plurality of SiC continuous fibers 2 dispersed at 2, W3 ... Form a fiber bundle 3b.
It has a structure arranged in the iC reactive sintering matrix 4. The carbon fibers 5 existing at the stage of the molded body 6 before the reaction sintering shown in FIG. 1 are converted into the SiC matrix 4 by the reaction sintering with the Si component. Therefore,
Since the SiC matrix 4 is sufficiently formed inside the fiber bundle 3b, the composite material 1a excellent in strength and fracture energy characteristics is obtained.

Comparative Example 1 Si used in Example 1 without using carbon fiber
Only 500 C continuous fibers were bundled to form a fiber bundle, and the fiber bundle was knitted in a two-dimensional direction to prepare a plain weave cloth-shaped fiber woven fabric. Hereinafter, as in Example 1, a preform was formed using this fiber woven fabric, and the above-mentioned matrix slurry was cast into the preform to form a formed body. Further, the obtained molded body was placed in a firing container filled with Si powder, and reaction sintering was performed in vacuum at 1420 ° C. for 3 hours to produce a SiC-based fiber composite material according to Comparative Example 1. .

Example 2 500 continuous silicon nitride fibers having a diameter of 10 μm and a diameter of 8 μm
And 500 polyester fibers of the above are bundled to form a fiber bundle, and the fiber bundle is used, and the number ratio of the fiber bundles in the three-dimensional directions (x, y, z directions) is x: y: z = 1: 1: 1. A three-dimensional woven fabric of 0.1 was prepared as a fiber preform. Next, the matrix slurry prepared in Example 1 was cast into the obtained three-dimensional fabric in a reduced pressure atmosphere to obtain a molded body. Further, the obtained molded body is air-dried and further heat-treated in nitrogen at a temperature of 800 to 1000 ° C. for 2 hours to carbonize the polyester fiber, and then placed in a firing container filled with Si powder, and in a vacuum. Temperature 1420 ℃
Example 3 was carried out by heating for 3 hours and performing reaction sintering while impregnating the molded body with molten Si, and synthesizing a reaction sintered matrix composed of SiC and Si inside and outside the molded body including the fiber bundle. A ceramic-based fiber composite material according to No. 2 was manufactured.

Comparative Example 2 Treatment was carried out under the same conditions as in Example 2 except that no polyester fiber was used and a fiber bundle formed by bundling only 500 continuous silicon nitride fibers used in Example 2 was used. A SiC-based fiber composite material according to Comparative Example 2 was prepared. That is, using the above fiber bundle, a three-dimensional woven fabric having a fiber bundle number ratio in the three-dimensional directions (x, y, z directions) of x: y: z = 1: 1: 0.1 is prepared as a fiber preform. did. Next, the obtained three-dimensional fabric was heat-treated in nitrogen at a temperature of 400 ° C. for 2 hours to remove the sizing agent. Further, the matrix slurry prepared in Example 1 was cast into a heat-treated three-dimensional woven fabric in a reduced pressure atmosphere to obtain a molded body. Further, the obtained molded body is air-dried, and further the temperature is 600-80.
After degreasing at 0 ° C. for 2 hours, it was placed in a firing container filled with Si powder and heated in vacuum at a temperature of 1420 ° C. for 3 hours to carry out reaction sintering while impregnating the molded body with molten Si. , SiC and Si inside and around the molded body
A SiC-based fiber composite material according to Comparative Example 2 was manufactured by synthesizing a reactive sintering matrix composed of

In order to evaluate the properties of the SiC-based fiber composite materials according to the examples and comparative examples thus prepared, test pieces were cut out from each material, and three points were obtained at room temperature (20 ° C.) and high temperature (1300 ° C.). A bending strength test was performed to evaluate the initial fracture strength, and the fracture energy at room temperature (20 ° C) and high temperature (1300 ° C) was measured. Here, the fracture energy value of each test piece was calculated by integrating the fracture energy from the shape of the load-displacement curve, setting the reference value 1 in the case of each comparative example, and calculating the magnification against that reference value and displaying each as a relative value. . The measurement results are shown in Table 1 below.

[0041]

[Table 1]

As is clear from the results shown in Table 1 above,
According to the composite material of each example in which the average gap between the adjacent ceramic fibers in the fiber bundle is appropriately controlled, the SiC matrix in the fiber bundle can be densely formed, so that the initial fracture strength becomes high. A composite material having a large fracture resistance even after cracking was obtained. In particular, the bending strengths of the composite materials according to the respective examples were nearly twice as high as those of the comparative examples, while the breaking energy was 10 times or more higher, showing extremely high breaking resistance. .

On the other hand, in each comparative example, since the gap between the adjacent ceramic fibers in the fiber bundle is too small,
Since the formation of the matrix layer in the fabric bundle is insufficient, the function of preventing the crack growth at the interface between the fiber bundle and the matrix is insufficient, the strength retention ratio after the initial cracking also decreases, and the fracture resistance decreases. .

[0044]

As described above, according to the silicon carbide-based fiber composite material and the method for producing the same according to the present invention, the average gap between the adjacent ceramic fibers in the fiber bundle can be adjusted arbitrarily. In particular, since the average gap is set to ½ or more of the ceramic fiber diameter, it becomes possible for the first time to form a sufficient SiC matrix between adjacent ceramic fibers in the fiber bundle. Therefore, the dispersion of the dispersion state of the ceramic fibers and the matrix is reduced, and the initial fracture strength of the composite material as a whole can be significantly improved. Further, since all the ceramic fibers forming the fiber bundle are bonded to the matrix, all the ceramic fibers contribute to the increase in pull-out resistance of the ceramic fibers after the initial crack growth. Further, since the slip resistance at the interface between the ceramic fiber and the matrix also increases, it is possible to provide a silicon carbide-based fiber composite material having an increased fracture energy.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts showing an arrangement state of each fiber before sintering of a silicon carbide-based fiber composite material according to the present invention.

FIG. 2 is a cross-sectional view of essential parts showing an embodiment of a silicon carbide-based fiber composite material according to the present invention.

FIG. 3 is a cross-sectional view of a main part showing a configuration of a conventional ceramics-based fiber composite material in which a ceramics fiber bundle is arranged in a matrix.

[Explanation of symbols]

1,1a Ceramics-based fiber composite material (SiC-based fiber composite material) 2 Ceramics fiber (SiC continuous fiber) 3,3a, 3b Fiber bundle (yarn) 4 Matrix (reaction-sintered SiC matrix) 5 Carbon fiber 6 Molded body 7 Matrix Molded product D Diameter of ceramics fiber W1, W2, W3 ... Gap between ceramics fibers

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location C04B 35/80 K G L

Claims (5)

[Claims] 1. A silicon carbide-based fiber composite material in which a fiber bundle formed by bundling a plurality of ceramic fibers is arranged in a matrix made of reaction-bonded silicon carbide, and an average gap between adjacent ceramic fibers in the fiber bundle. Is set to ½ or more of the ceramic fiber diameter, a silicon carbide based fiber composite material. 2. The silicon carbide based fiber composite material according to claim 1, wherein a sliding layer made of boron nitride (BN) is formed on the surface of the ceramic fiber. 3. The silicon carbide based fiber composite material according to claim 1, wherein the content ratio of the ceramic fibers in the composite material is 5 to 55% by volume. 4. A fiber preform having a predetermined shape is formed by using a fiber bundle in which a plurality of ceramic fibers and carbon fibers are bundled, and the fiber preform is impregnated with a matrix starting material containing a silicon and a carbon source. A molded body of a predetermined shape is formed, and the obtained molded body is heated in a vacuum or in an inert gas atmosphere to carry out reaction sintering of silicon with a carbon source and carbon fibers to form a matrix made of silicon carbide. Then, the above-mentioned fiber preform and the matrix are integrally compounded to provide a silicon carbide based fiber composite material. 5. A fiber preform having a predetermined shape is formed by using a fiber bundle obtained by bundling a plurality of ceramic fibers and organic polymer fibers, and the fiber preform is impregnated with a matrix starting material containing a silicon and carbon source. At least a molded product having a predetermined shape is formed, and the resulting molded product is heat-treated to carbonize the organic polymer fibers, and then heated in a vacuum or an inert gas atmosphere to remove silicon, a carbon source, and carbonization. A method for producing a silicon carbide-based fiber composite material, characterized in that a matrix made of silicon carbide is formed by reaction sintering with the organic polymer fiber described above, and the fiber preform and the matrix are integrally combined.