Carbon fiber preform and carbon / carbon composite material using same

Abstract

The invention relates to a carbon fiber preform and a carbon / carbon composite material using the same. The present invention provides a carbon fiber preform for a carbon / carbon composite material, the carbon fiber preform being a carbon fiber preform before being compounded with carbon, the carbon fiber preform being obtained by integrating a laminate in which two or more sheet-like substrates including a carbon fiber sheet are laminated, in a load displacement curve in a peeling test of the carbon fiber preform, there are recesses having an extreme value 2 adjacent to the protrusions having an extreme value 1, and there are a plurality of protrusions in which the extreme value 1 satisfies two times or more of the extreme value 2, and the bundle strength of the carbon fibers is 0.1 kgf or more and 0.2 kgf or less with respect to the number per 1 tex.

Description

Technical Field

[0001] The present invention relates to the field of carbon / carbon composites. More specifically, it relates to a carbon fiber preform and a carbon / carbon composite using the same. Background Art

[0002] Carbon / carbon composites are high-strength composites obtained by processing with carbon fibers or carbon fiber braids as reinforcing materials and graphite or carbon as the matrix. Carbon / carbon composites have many excellent properties such as light weight, high heat resistance, high durability, high specific strength, high specific modulus, low coefficient of thermal expansion, and heat shock resistance. Therefore, they are widely used in support members for quartz crucibles that melt silicon for photovoltaic power generation, structural members of aerospace vehicles, etc.

[0003] The two most commonly used process methods for preparing carbon / carbon composites are chemical vapor deposition and precursor infiltration pyrolysis. Among them, precursor infiltration pyrolysis uses a porous carbon fiber braid as a preform and asphalt or polymer as a precursor. Through liquid-phase infiltration, the liquid precursor fully penetrates into the porous preform. At high temperature, the precursor undergoes a pyrolysis reaction to generate pyrolytic carbon, and finally a carbon / carbon composite is formed. However, for the obtained carbon / carbon composites, there is a case of interlayer delamination, resulting in problems with the durability of the carbon / carbon composites. Therefore, it is important to improve the delamination strength starting from the preform.

[0004] Patent Document 1 discloses a crucible preform reinforced with continuous carbon fibers. The preform is laminated and reinforced by basic unit layers and continuous fibers, formed by needling technology, and the bottom of the crucible and the connection area between the crucible wall and the bottom are reinforced by continuous fiber winding and laying technology, effectively increasing the content of continuous fibers connected in the overall structure, ensuring the strength required under high load and expansion stress, avoiding cracking of the crucible or detachment of the connection area between the crucible wall and the bottom, and at the same time being able to maintain excellent shape stability.

[0005] Patent Document 2 discloses a high-density carbon fiber needle punched felt, which is formed by laminating and needling structural units composed of a carbon fiber web and a carbon fiber spread fabric. In Patent Document 2, a carbon fiber cloth prepared by using spread fibers is used to replace the commonly used carbon fiber cloth, reducing the thickness of the carbon fiber cloth and reducing the springback phenomenon caused by the gaps between carbon fibers during the needling process, thereby improving the overall density and mechanical strength of the carbon fiber needle punched felt.

[0006] Patent Document 3 discloses a carbon fiber preform, which is formed by laminating and hot-pressing multiple preform structural units. Among the preform structural units of each layer, the second preform structural unit layer and the nth preform structural unit layer both include composite unit layers, where n≥3. When manufacturing the carbon fiber preform in Patent Document 3, the step of separately laying the web in the original needling process of the carbon fiber preform can be omitted, shortening the manufacturing time of the carbon fiber preform and improving production efficiency.

[0007] Patent Document 4 discloses a high-performance carbon fiber needled preform manufactured by a preparation method including specified steps. In Patent Document 4, by adopting a preparation method including specified steps, problems such as large fiber strength loss, limited densification degree, low density and strength of the finally formed product, and problems existing in various applications are solved.

[0008] Prior art documents

[0009] Patent documents

[0010] Patent Document 1: CN103482995B

[0011] Patent Document 2: CN110747578A

[0012] Patent Document 3: CN115214203A

[0013] Patent Document 4: CN114645462A Summary of the invention

[0014] Problems to be solved by the invention

[0015] However, there is still room for improvement in the interlayer delamination of the carbon / carbon composites prepared by using the preforms disclosed in the above Patent Documents 1 to 4.

[0016] The object of the present invention is to provide a carbon fiber preform that can improve the delamination strength of carbon / carbon composites.

[0017] Means for solving the problems

[0018] The inventors of the present application conducted in-depth research to solve the above problems and found that, by having a concave portion with an extreme value 2 adjacent to a convex portion with an extreme value 1 in the load-displacement curve in the delamination test of the carbon fiber preform, and having multiple convex portions where the extreme value 1 satisfies more than twice the extreme value 2, and making the bundle strength of the carbon fiber be 0.1 kgf or more and 0.2 kgf or less relative to the number per 1 tex, the delamination strength of the carbon / carbon composite can be improved, thus completing the present invention.

[0019] The present invention provides the following technical solutions.

[0020] 1. A carbon fiber preform for a carbon / carbon composite material, which is a carbon fiber preform before being combined with carbon.

[0021] The aforementioned carbon fiber preform is obtained by integrating the following laminate, which is formed by laminating two or more sheet-like base materials including carbon fiber sheets.

[0022] In the load-displacement curve in the peel test of the aforementioned carbon fiber preform, there is a concave portion with an extreme value 2 adjacent to a convex portion with an extreme value 1, and there are multiple convex portions where the extreme value 1 satisfies more than twice the extreme value 2.

[0023] The bundle strength of the carbon fiber is 0.1 kgf or more and 0.2 kgf or less per 1 tex number.

[0024] 2. Regarding the above carbon fiber preform, the aforementioned carbon fiber sheet is one or more selected from woven fabrics, felts, and unidirectional sheets using carbon fibers.

[0025] 3. Regarding the above carbon fiber preform, in the load-displacement curve in the peel test of the aforementioned carbon fiber preform, the convex portions are present at equal intervals 5 times or more and 10 times or less within a peel distance of 30 mm.

[0026] 4. Regarding the above carbon fiber preform, the strength of the carbon fiber is 4800 MPa or more and 8200 MPa or less.

[0027] 5. Regarding the above carbon fiber preform, the sizing agent adhesion amount of the carbon fiber is 0% or more and 0.5% or less based on the weight of the carbon fiber.

[0028] 6. A carbon / carbon composite material, which is obtained by carbonizing after combining the aforementioned carbon fiber preform with carbon.

[0029] 7. A crucible, which contains the above carbon / carbon composite material.

[0030] Effects of the Invention

[0031] According to the present invention, it is possible to provide a carbon fiber preform that can improve the peel strength of the carbon / carbon composite material. Brief Description of the Drawings

[0032] Figure 1 Figure 1 It is a schematic diagram showing the stretching by folding the end portion in the peel test of the fiber preform.

[0033] Figure 2 Figure 2 It is a diagram schematically showing the load-displacement curve in the peel test of the carbon fiber preform of Example 1.​​​​

[0034] Figure 3 Figure 3 A diagram schematically showing the load-displacement curve in the peeling test of the carbon fiber preform of Comparative Example 2. Detailed implementation manners

[0035] Hereinafter, preferred manners for implementing the present invention will be described. The implementation manners described below represent an example of representative implementation manners of the present invention, and the scope of the present invention is not narrowly interpreted thereby.

[0036] The present invention relates to a carbon fiber preform for a carbon / carbon composite material, which is a carbon fiber preform before being combined with carbon.

[0037] The aforementioned carbon fiber preform is obtained by integrating the following laminate, which is formed by laminating two or more sheet-like base materials including carbon fiber sheets.

[0038] In the load-displacement curve in the peeling test of the aforementioned carbon fiber preform, there are concave portions having an extreme value 2 adjacent to convex portions having an extreme value 1, and there are multiple convex portions where the extreme value 1 satisfies more than twice the extreme value 2.

[0039] The bundle strength of the carbon fiber is 0.1 kgf or more and 0.2 kgf or less per tex number.

[0040] The form of the carbon fiber sheet used in the present invention is not particularly limited. For example, (i) woven fabric, (ii) braided fabric, (iii) tape, (iv) non-woven fabric, (v) unidirectional sheet formed by making a unidirectionally arranged reinforcing fiber sheet have a stable form using an adhesive or fusible non-woven fabric, sewing yarn, etc., (vi) felt composed of randomly oriented short fibers, etc. Among them, woven fabric, felt, and unidirectional sheet are preferably used, and woven fabric is more preferably used.

[0041] Examples of the carbon fiber include polyacrylonitrile (sometimes simply referred to as PAN)-based, rayon-based, and pitch-based carbon fibers. Among them, PAN-based carbon fibers with excellent balance between strength and elastic modulus are preferably used.

[0042] The specification of the carbon fiber is not particularly limited, and 1K, 3K, 6K, 12K, 24K are all acceptable. Carbon fibers of 12K specification are preferably used.

[0043] The type of the carbon fiber is not particularly limited, and examples include T700S, T1100G, etc. manufactured by Toray Industries, Inc. of Japan.

[0044] The tensile strength of the carbon fiber is preferably 4800 MPa or more and 8200 MPa or less, and more preferably 5100 MPa or more and 7200 MPa or less.​​

[0045] From the viewpoint of further improving the purity of silicon, the smaller the amount of Sz contained in the carbon fiber, the better. Considering the actual process level, the amount of Sz is preferably 0.4% or less.

[0046] The carbon fiber may or may not be sized. When sizing is applied, the amount of sizing adhered is preferably 0.5% or less based on the weight of the carbon fiber.

[0047] The sizing agent is not particularly limited, and examples thereof include sizing agents such as polyamide (PA) type, polyurethane (PU) type, polyarylether type, and polyimide (PI) type.

[0048] The number of layers of the laminate is 2 to 50 layers, preferably 20 layers or less.

[0049] As a method for integrating the laminate, examples include 2.5D weaving, three-dimensional braiding, stitching, piercing, needling, etc. Among them, needling or stitching is preferably used.

[0050] The needling process is a process in which a special needle with backward barbs is used to needle the laminate to form a quasi-three-dimensional network structure reinforcement with a certain strength both in the plane and between layers. The preform made by the needling process has the advantages of uniform pore distribution, easy densification and forming, high in-plane and interlayer strength, etc., and has high production efficiency, low cost, and is easy to achieve mass production.

[0051] As a specific needling process, for example, a loom or the like can be used to make a woven fabric from carbon fiber (such as carbon fiber of 12K specification). After stacking multiple layers of the woven fabric, integration is performed by needling. In the needling process, the position of the perforation is carefully adjusted by needling through the stacked substrate and arranging the needles at equal intervals.

[0052] The stitching process is a process in which the laminate is strengthened in the direction perpendicular to the lay-up plane by means of manual stitching or machine stitching, increasing the volume content of continuous fibers in the plane of the material, and thereby improving the interlayer damage tolerance of the material. The stitches passing through the thickness direction of the laminate can greatly improve the interlayer performance of the laminate. The preform made by the stitching process has strong interlayer strength, is not easily delaminated, and the impact damage resistance performance is improved, which can reduce the structural mass and the total manufacturing cost.

[0053] As a specific stitching process, for example, carbon fiber (such as carbon fiber of 1K specification) can be hand-sewn to the laminate at a specified interval to integrate the substrate.

[0054] In the present invention, importantly, in the load-displacement curve in the peeling test of the carbon fiber preform, there is a concave portion with an extreme value 2 adjacent to a convex portion with an extreme value 1, and there are multiple convex portions where the extreme value 1 satisfies more than twice the extreme value 2. Thus, the peeling strength of the carbon / carbon composite material can be significantly improved. The ratio of the convex extreme value 1 to the concave extreme value 2 is preferably 2.1 or more and preferably 2.5 or less.

[0055] In the load-displacement curve in the peeling test of the carbon fiber preform, from the viewpoint of further realizing the technical effects of the present invention (such as significantly improving the peeling strength, etc.), preferably, the intervals of the unevenness are equally spaced. More preferably, the convex portions are present 5 or more and 10 or less times at equal intervals within a peeling distance of 30 mm.

[0056] The load-displacement curve is obtained by the following method.

[0057] A test piece with a width of 50 mm and a length of 300 mm is cut out from the prepared carbon fiber preform, and as shown in the appendix Figure 1 it is divided into two parts in units of 10 layers in the thickness direction. For each part, the end is folded by 50 mm and fixed by clamping with a mechanical testing machine. The peeling test is carried out with the tensile speed of the mechanical testing machine set at 10 mm / min, and the load-displacement is recorded. The ratio of the extreme value 1 to the extreme value 2 is recorded six times and the average value is taken.

[0058] In the present invention, it is also important that the bundle strength of the carbon fiber is 0.1 kgf or more and 0.2 kgf or less with respect to the number per 1 tex. Thus, it helps to improve the peeling strength of the carbon / carbon composite material. The bundle strength of the carbon fiber is preferably 0.14 kgf or more and 0.18 kgf or less with respect to the number per 1 tex.

[0059] The bundle strength of the carbon fiber is measured by the following method.

[0060] A 100-mm length is cut out from one bobbin of the carbon fiber, and the weight is measured. The average value of six times is multiplied by 1000 to obtain a representative value of the unit area weight of the carbon fiber.

[0061] Then, a 150-mm length is cut out from each bobbin of the carbon fiber, and both ends are held at 50 mm each in a non-slip manner, and a load is applied in the tensile direction and measured 5 times repeatedly. The tensile speed is set at 60 mm / min. The average value of the obtained maximum loads is used as the representative value of the bundle strength. By dividing the bundle strength by the unit area weight of the carbon fiber, the bundle strength per 1 tex is obtained.

[0062] By carbonizing the obtained carbon fiber preform after carbon composite, a carbon / carbon composite material can be obtained.

[0063] As a specific preparation process of carbon / carbon composites, chemical vapor deposition method or precursor infiltration and pyrolysis method can be cited. The former uses organic low-molecular gases as precursors, and the latter uses thermoplastic resins such as pitch or thermosetting resins such as phenolic resins as matrix precursors. These raw materials undergo a series of complex chemical changes at high temperatures and are converted into matrix carbon. Among them, in the chemical vapor deposition method, carbon is directly deposited in the pores of the green body, and in the precursor infiltration and pyrolysis method, a preform made of carbon fiber is immersed in a liquid impregnating agent, and through a series of processes such as curing, carbonization, and graphitization, carbon / carbon composites are finally obtained. In order to obtain better densification effect, a combination of the two methods can also be used to prepare carbon / carbon composites with ideal density.

[0064] The carbon / carbon composites of the present invention can be used as supports for quartz crucibles for melting silicon of silicon wafers for photovoltaic power generation, structural components of aerospace vehicles, etc.

[0065] Examples

[0066] Hereinafter, the present invention will be described in more detail based on examples. The examples described below represent an example of a representative embodiment of the present invention, and the scope of the present invention is not narrowly interpreted thereby.

[0067] <Fabrication of carbon fiber preform>

[0068] (Example 1)

[0069] As the carbon fiber, T700S-12K manufactured by Toray Industries, Inc., Japan was used, and a woven fabric with a width of 1 m was made from this carbon fiber using a loom. After laminating 20 layers of the obtained woven fabric to obtain a laminate with a thickness of about 6 mm, the laminate was integrated by needling to obtain a carbon fiber preform. Regarding needling, the position of the perforation was adjusted so that the needles penetrated the laminated substrate and the needles were arranged at equal intervals, and the needling density was set to 25-30 needles / cm 2 .

[0070] (Example 2)

[0071] As the carbon fiber, T700S-12K manufactured by Toray Industries, Inc., Japan was used, and a woven fabric with a width of 1 m was made from this carbon fiber using a loom. After laminating 20 layers of the obtained woven fabric to obtain a laminate, carbon fibers of 1K specification were hand-sewn to the obtained laminate at intervals of 5 mm, and the substrate was integrated to obtain a carbon fiber preform.

[0072] (Example 3)

[0073] As the carbon fiber, T1100G-12K manufactured by Toray Industries, Inc., Japan was used. Except for this, the carbon fiber preform was prepared in the same manner as in Example 1.

[0074] (Example 4)

[0075] As the carbon fiber, T1100G-12K manufactured by Toray Industries, Inc., Japan was used. Except for this, a carbon fiber preform was prepared in the same manner as in Example 2.

[0076] (Comparative Example 1)

[0077] As the carbon fiber, T300-12K manufactured by Toray Industries, Inc., Japan was used. Except for this, a carbon fiber preform was prepared in the same manner as in Example 1.

[0078] (Comparative Example 2)

[0079] As the carbon fiber, T700S-12K manufactured by Toray Industries, Inc., Japan was used. Needling was performed in a non-uniform manner. Except for this, a carbon fiber preform was prepared in the same manner as in Example 1. It should be noted that due to the non-uniform needling, there are parts where the needling is too close or too far. In these parts, peeling proceeds unstably before the peeling load increases.

[0080] <Measurement of the weight per unit area (g / 1000m) of carbon fiber>

[0081] A 100-mm length was cut from one spool of carbon fiber, and the weight was measured. The average value of six measurements was multiplied by 1000 to obtain a representative value of the weight per unit area of the carbon fiber.

[0082] <Measurement of bundle strength>

[0083] A 150-mm length was cut from each spool of carbon fiber. Each end was held at 50 mm without slipping, and a load was applied in the tensile direction and measured five times repeatedly. The tensile speed was set at 60 mm / min. The average value of the maximum loads obtained was used as the representative value of the bundle strength. The bundle strength was divided by the weight per unit area of the carbon fiber to obtain the bundle strength per 1 tex.

[0084] <Peeling test>

[0085] Test pieces with a width of 50 mm and a length of 300 mm were cut from the carbon fiber preforms prepared in each example and comparative example. As shown in the attachment Figure 1 , they were divided into two parts in units of 10 layers in the thickness direction. For each part, the ends were folded over by 50 mm and clamped and fixed with a mechanical testing machine (device of TFRC). The tensile speed of the mechanical testing machine was set at 10 mm / min, and a peeling test was performed according to the JIS L1086-2013 standard, and the load-displacement was recorded. The peeling distance was set at 100 mm. The ratio of the six extreme values 1 to extreme values 2 was recorded, and the average value was entered in Table 1.

[0086] <Tensile strength of carbon fiber>

[0087] According to GB / T 26749-2022, impregnate with epoxy resin to make a wire harness test piece. Use a mechanical testing machine to measure the tensile strength at a speed of 10 mm / min.

[0088] <Sz amount>

[0089] Cut out 3 g of carbon fiber, keep it at 500 °C for 30 minutes, and calculate the Sz amount from the weight ratio before and after heating.

[0090] <Evaluation>

[0091] (Composite bending test)

[0092] Under vacuum conditions, inject epoxy resin into the carbon fiber preforms prepared in each example and comparative example, and cure the resin to make a composite. Cut out a test piece with a span length of 150 mm and a width of 10 mm from the made composite, use a mechanical testing machine manufactured by Instron with a 10 t load cell, set the speed of the crosshead to 1 mm / min, and perform a three-point bending test. Perform the test 5 times, and record the average value in Table 1.

[0093] <Results>

[0094] Show the results of each example and comparative example in Table 1.

[0095] [Table 1]

[0096]

[0097] As shown in Table 1, in Examples 1 to 4, it can be confirmed that the results of the composite bending test are all excellent. In contrast, in Comparative Examples 1 and 2, since the convex extreme value / concave extreme value and / or bundle strength do not fall within the scope of the present invention, the results of the composite bending test are significantly deteriorated. It should be noted that the same trend is also shown when formed into a carbon / carbon composite material.

Claims

1. A carbon fiber preform for a carbon / carbon composite material, which is a carbon fiber preform before being combined with carbon. The carbon fiber preform is obtained by integrating the following laminate, which is formed by laminating two or more sheet-like base materials including carbon fiber sheets. In the load-displacement curve in the peel test of the carbon fiber preform, there is a concave portion with an extreme value 2 adjacent to a convex portion with an extreme value 1, and there are multiple convex portions where the extreme value 1 satisfies more than twice the extreme value 2. The bundle strength of the carbon fiber is 0.1 kgf or more and 0.2 kgf or less per 1 tex number.

2. The carbon fiber preform according to claim 1, wherein, The carbon fiber sheet is one or more selected from woven fabrics, felts, and unidirectional sheets using carbon fibers.

3. The carbon fiber preform according to claim 1 or 2, wherein, In the load-displacement curve in the peel test of the carbon fiber preform, the convex portions are present at equal intervals 5 times or more and 10 times or less within a peel distance of 30 mm.

4. The carbon fiber preform according to claim 1 or 2, wherein The tensile strength of the carbon fiber is 4800 MPa or more and 8200 MPa or less.

5. The carbon fiber preform according to claim 1 or 2, wherein The sizing agent adhesion amount of the carbon fiber is 0% or more and 0.5% or less based on the weight of the carbon fiber.

6. A carbon / carbon composite material, which is obtained by carbonizing after combining the carbon fiber preform according to any one of claims 1 to 5 with carbon.

7. A crucible, which comprises the carbon / carbon composite material according to claim 6.

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