JPH0543337A - Carbon fiber-reinforced composite material and its production - Google Patents

Abstract

PURPOSE:To produce a carbon-fiber reinforced composite material having a high strength by covering the surfaces of carbon fiber substrates with a carbon matrix and further covering the carbon matrix with a ceramic matrix. CONSTITUTION:The whole surfaces of carbon fiber substrates (woven or nonwoven fabrics) are covered with a carbon precursor (a resin, pitch, etc.), which is further covered with a ceramic precursor (Si, Ti, B, etc.) to laminate sheets of the resultant prepreg. The prepared laminated sheets of the prepreg are then burned under pressure to produce a carbon-fiber reinforced composite material in which the carbon matrix and the ceramic matrix are laminated. The objective carbon-fiber reinforced composite material excellent in strength without causing damage to carbon fiber is obtained by providing a reaction protective layer between the carbon fiber and ceramic matrix.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon fiber reinforced composite material having high strength and a method for producing the same.

[0002]

2. Description of the Related Art Carbon fiber reinforced composite materials are used as various super heat resistant materials because they are excellent in heat resistance and oxidation resistance and lightweight. By the way, the production method of this carbon fiber reinforced composite material is roughly divided into (1) a method of densifying by repeating impregnation and firing of a carbon fiber base material into a matrix precursor,
There are (2) a method of filling a carbon fiber base material with a matrix by a chemical vapor deposition method, and (3) a method of laminating a prepreg having a matrix precursor attached to a carbon fiber base material, pressurizing and firing it.

[0003]

However, the above (1),
The method (2) has problems that it takes a lot of time and that the thick material cannot be filled with the ceramics.
Further, in the methods (1) and (3), the matrix ceramics are often difficult to sinter, and a sintering aid is required. However, in the fiber reinforcement, since fibers serve as fillers, a large amount of sintering aid is required as compared with a single material, and there is a problem that the large amount of sintering aid deteriorates the high temperature characteristics of the reinforcement.

On the other hand, as a sintering method for hardly-sinterable ceramics, a reaction sintering method in which a mixture of a ceramic precursor metal or a metal compound and a reactant for supplying carbon is used as a raw material and a reaction is performed during sintering There is. When this method is applied to a carbon fiber reinforced composite material, the carbon fiber, which is a reinforcing fiber, is also an object of the reaction, so that the carbon fiber is damaged and only a composite material having extremely low strength is obtained.

[0005]

DISCLOSURE OF THE INVENTION The present invention is a carbon fiber reinforced composite material and a method for producing the same made to solve the above problems. First, in the composite material, a carbon matrix is provided around a carbon fiber base material. It is characterized in that it is covered and further covered with a ceramic matrix, the manufacturing method is such that the entire surface of the carbon fiber substrate is covered with a carbon precursor, and this carbon precursor is further covered with a ceramic precursor. It is characterized in that prepregs are laminated, pressed and fired.

Here, the manufacturing method of the prepreg is (a) a method of immersing a carbon fiber base material in a matrix precursor,
Either (b) a method of depositing a matrix precursor on a carbon fiber base material by an electrodeposition method, or (c) a method of forming a matrix precursor into a sheet shape and sandwiching the matrix precursor between the carbon fiber base materials. You can use it.

In the methods (a) and (b), the carbon precursor is first attached to the carbon fiber substrate, and then the ceramic precursor is further attached thereon. In the case of the method (c),
The ceramic precursor sheet is sandwiched between the carbon precursor sheets and the carbon fiber base material is alternately laminated. In addition, the carbon precursor is deposited by the method (a) and the ceramic precursor is deposited by the method (c).
A prepreg may be manufactured by combining the methods of (b) and (c).

The carbon fiber base material is a two-dimensional base material, that is, woven cloth, non-woven cloth (felt, paper, mat).
Etc. may be used. As the carbon precursor, one selected from resin, pitch, carbon black, graphite powder, and self-sintering carbon powder is used, and as the ceramic precursor, Si,
A metal simple substance or metal compound selected from Ti, B, Hf, Zr, and W, and a carbon precursor for supplying carbon (selected from resin, pitch, carbon black, graphite powder, and self-sintering carbon powder). A mixture of and may be used.

[0009]

As described above, when the reactive sintering method is used for the carbon fiber reinforced composite material, the carbon fiber which is the reinforcing fiber also becomes a target of the reaction and causes damage to the carbon fiber. The present invention is a combination of the method (3) and the reactive sintering method in the above-mentioned conventional technique, in which the carbon precursor is uniformly adhered to the carbon fiber at the stage of the prepreg before the lamination, The carbon precursor serves as a reaction protection layer without directly contacting the ceramic precursor. Therefore, the firing can be performed without damaging the carbon fiber.

Further, since the deposition of the carbon precursor of the carbon fiber and the deposition of the ceramics precursor on the carbon precursor can be easily controlled for each prepreg unit to be laminated, the carbon matrix layer can be protected against the reaction. Sufficiently, it is possible to produce a material having a uniform structural composition even inside the composite material.

The amount of carbon precursor depends on the ceramic material,
The amount must be changed depending on the amount and use of the carbon fiber reinforced composite material, but if it is too small, it will not function as a reaction protection layer, and if it is too large, it will impair the properties of ceramics such as oxidation resistance and wear resistance. become. From the above, the amount of carbon precursor is 5 to the carbon fiber after firing.
It is preferable to control the content within the range of 100% by weight. Further, the ratio of the elemental metal or the metal compound in the ceramic precursor and the carbon precursor supplying carbon is preferably the composition ratio of the produced ceramic.

[0012]

[Test Example] The composite material of the present invention was actually prepared and their bending strength and interlaminar strength were examined together with the comparative example. Examples and comparative examples are as follows.

(Example 1) With respect to a method for producing a prepreg, both a carbon precursor and a ceramics precursor were deposited by the method (a). The PAN-based carbon fiber woven cloth was dipped in the epoxy resin, and the resin was adhered all over the carbon fiber. In this state, the weight ratio of the resin to the carbon fiber woven cloth was 1: 1. Titanium powder having an average particle diameter of 2 μm was well kneaded and dispersed with an epoxy resin and a solvent to prepare a coating material. The weight ratio of titanium powder to resin in this state was 2: 1. The prepreg obtained in step 1 was dipped in the solution to further deposit a ceramics precursor on the surface of the resin to obtain a prepreg. In this state, the weight ratio of titanium powder to carbon fiber woven cloth was 4: 1. The prepreg obtained in (1) was dried, and the prepreg was laminated and pressure-fired to 2000 ° C. to obtain a carbon fiber-reinforced ceramic composite material.

(Example 2) In this example, both the carbon precursor and the ceramics precursor are deposited by the method (b). A carbon powder having an average particle diameter of 10 μm and having self-sinterability was well kneaded with an acrylic amide resin and a solvent, and then dispersed in water to obtain a so-called anionic coating material. In this state, the weight ratio of carbon powder to resin was 2: 1. The PAN-based carbon fiber-based woven fabric was dipped in the dispersion solution of, and a voltage of about 30 V was applied with stirring to deposit the carbon precursor throughout the carbon fibers. In this state, the specific gravity of the carbon powder and the carbon fiber woven cloth was 1: 2 by weight. Silicon powder having an average particle diameter of 2 μm was thoroughly kneaded with an acrylic amide resin and a solvent, and then dispersed in water to obtain an anionic coating material. In this state, the weight ratio of silicon powder to resin was 2: 1. The prepreg obtained in (3) was dipped in the solution, and a voltage of about 30 V was applied with stirring to obtain a prepreg in which a ceramics precursor was further deposited on the surface of the carbon precursor. In this state, the weight ratio of silicon powder to carbon fiber woven cloth was 3: 1. The dried prepregs are laminated to form 20 layers.
It was pressure-fired to 00 ° C. to obtain a carbon fiber reinforced ceramic composite material.

(Embodiment 3) In this embodiment, both the carbon precursor and the ceramic precursor are deposited by the method (c). A carbon precursor sheet was obtained by molding a self-sintering carbon powder having an average particle diameter of 10 μm that was well kneaded with a phenolic resin and a solvent into a sheet. In this state, the weight ratio of carbon powder to resin was 2: 1. Boron powder having an average particle diameter of 3 μm was well kneaded with a phenolic resin and a solvent, and molded into a sheet to obtain a ceramic precursor sheet. In this state, the weight ratio of the boron powder to the resin was 2: 1 and the weight was 4 times that of the carbon precursor sheet. A matrix precursor sheet was prepared by sandwiching both sides of a ceramics precursor sheet with carbon precursor sheets. Matrix precursor sheets with Pitch-based high modulus carbon fiber felt were alternately laminated. Here, the weight ratio of the carbon fiber woven fabric and the matrix precursor sheet is set to 1: 6. The prepreg obtained in 1. was pressure-fired to 2000 ° C. to obtain a carbon fiber reinforced ceramic composite material.

Comparative Example 1 This example is the same as Example 1 except that the carbon precursor was not deposited. A PAN-based carbon fiber woven fabric was dipped in the solution of Example 1 to adhere a ceramics precursor to obtain a prepreg.
In this state, the weight ratio of titanium powder to carbon fiber woven cloth was 4: 1. The dried prepregs are laminated to form 20 layers.
It was pressure-fired to 00 ° C. to obtain a carbon fiber-reinforced ceramic composite material.

(Comparative Example 2) In this example, a mixture of the carbon precursor and the ceramics precursor used in Example 2 was used as a matrix precursor. A self-sintering carbon powder having an average particle size of 10 μm and a silicon powder having an average particle size of 2 μm were thoroughly kneaded with an acrylic amide resin and a solvent, and then dispersed in water to obtain a so-called anionic paint. In this state, the ratio of carbon powder, silicon and resin was 1: 3: 2 by weight. A PAN-based carbon fiber woven fabric was dipped in the dispersion liquid, and a voltage of about 30 V was applied with stirring to obtain a prepreg in which a matrix precursor was deposited on the carbon fibers. In this state, the ratio of the raw material powder to the carbon fiber woven fabric is 3.
It was 5: 1. The dried prepregs are laminated to form 20 layers.
It was pressure-fired to 00 ° C. to obtain a carbon fiber-reinforced ceramic composite material.

(Comparative Example 3) In this example, the carbon precursor of Example 2 was not deposited. A PAN-based carbon fiber woven fabric was dipped in the solution of Example 2 and a voltage of about 30 V was applied with stirring to deposit a ceramic precursor all over the carbon fiber. In this state, the ratio of the silicon powder to the carbon fiber woven cloth is 3.
It was 5: 1. The dried prepregs are laminated to form 20 layers.
It was pressure-fired to 00 ° C. to obtain a carbon fiber-reinforced ceramic composite material.

(Comparative Example 4) In this example, the carbon precursor of Example 3 was not deposited. The Pitch-based high elastic modulus carbon fiber felt and the ceramic precursor sheet obtained in Example 3 were alternately laminated. Here, the weight ratio of the carbon fiber woven fabric and the ceramics precursor sheet is set to 1: 4. The prepreg obtained in 1. was pressure-fired to 2000 ° C. to obtain a carbon fiber reinforced ceramic composite material.

With respect to the carbon fiber reinforced composite materials obtained in Examples 1 to 3 and Comparative Examples 1 to 4, the bending strength and the interlayer strength in the direction perpendicular to the layer direction were measured. The shape of the sample is bending strength: thickness x width x span = 5 mm x 7
mm × 30 mm, interlayer strength: thickness × length × width = 4 mm × 4
It is mm × 20 mm. The results are shown in Table 1.

[0021]

[Table 1]

As shown in the table, there is a large difference between the system using the carbon fiber woven cloth having a high coefficient of thermal expansion of the matrix and the strong orientation of the carbon fibers, that is, Example 1 and Comparative Example 1. There is. In Example 1, the bending strength was 5 times or more and the interlayer strength was 3 times or more as compared with Comparative Example 1 having no protective layer made of a carbon matrix, and its effectiveness was confirmed.
Also, in the fracture surface observation with a microscope, in Comparative Example 1, many cracks and delamination of carbon fibers and matrix were observed, but in Example 1, it was significantly reduced. Furthermore, in the comparative example, the surface of the carbon fiber was rough due to the reaction with the matrix, but such a phenomenon was not observed in the examples.

On the other hand, Comparative Example 2 in which a mixture of carbon precursor and ceramics precursor was used as a matrix precursor,
In terms of bending strength, it is superior to Comparative Example 3 having no reaction protection layer, but the bending strength and interlayer strength of Example 2 having a carbon precursor attached and a reaction protection layer are lower.

It was confirmed that the bending strength and the interlayer strength of Example 3 were also improved as compared with Comparative Example 4 having no reaction protection layer. In all the comparative examples, the surface of the carbon fiber was rough due to the reaction with the matrix, but no such phenomenon was observed in the examples.

[0025]

As described above, according to the present invention,
By providing the reaction protection layer between the carbon fiber and the ceramic matrix, it is possible to obtain a carbon fiber reinforced composite material having excellent strength without causing damage to the carbon fiber.
Further, the material of the present invention can control the adhesion amount of the carbon precursor and the ceramics precursor in the unit of the prepreg to be laminated, so that it has a uniform composition even in the inside, and is industrially useful as a heat-resistant and oxidation-resistant material. Some are extremely large.

Claims (5)

[Claims] 1. A carbon fiber reinforced composite material characterized in that the surface of a carbon fiber base material is covered with a carbon matrix, and the surface thereof is further covered with a ceramic matrix. 2. A carbon precursor is entirely covered with a carbon precursor,
A method for producing a carbon fiber reinforced composite material, which comprises stacking a prepreg in which the carbon precursor is further covered with a ceramics precursor, and applying pressure and firing. 3. The carbon fiber reinforced composite material according to claim 1 or the carbon fiber reinforced composite material according to claim 2, wherein the carbon fiber base material is a two-dimensional base material, that is, a woven fabric or a non-woven fabric. Manufacturing method. 4. The carbon fiber reinforced composite material according to claim 1, wherein the carbon precursor is selected from resin, pitch, carbon black, graphite powder, and self-sintering carbon powder. Item 3. A method for producing a carbon fiber reinforced composite material according to item 2. 5. The ceramic precursor is Si, Ti,
The carbon fiber reinforced composite material according to claim 1 or claim 2, which is composed of a mixture of a simple metal or a metal compound selected from B, Hf, Zr and W and a carbon precursor for supplying carbon. Of manufacturing a carbon fiber reinforced composite material of.