A method for repairing local defects in carbon fiber reinforced ceramic matrix composites

Abstract

This invention discloses a method for repairing local defects in carbon fiber reinforced ceramic matrix composites, characterized by the following steps: preparing a first fiber slurry, comprising carbon fiber, water glass, and ceramic powder; preparing a second fiber slurry, comprising long-fiber boron nitride fibers, ceramic powder, and solvent; preparing a third fiber slurry, comprising short-fiber boron nitride fibers, ceramic powder, polymer monomers, crosslinking agent, initiator, and solvent; impregnating the local defect in the carbon fiber reinforced ceramic matrix composite with the first fiber slurry, filling 60-80% of the defect; then filling with the second fiber slurry, filling the remaining 60-80% of the defect, and then squeezing out excess solvent; then filling with the third fiber slurry to fill the defect, and then curing at room temperature. This method achieves rapid repair of local defects in carbon fiber reinforced ceramic matrix composites without the need for high-temperature heating.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber reinforced ceramic matrix composites, and more specifically to a method for repairing local defects in carbon fiber reinforced ceramic matrix composites. Background Technology

[0002] Carbon fiber reinforced ceramic matrix composites are composite materials with carbon fiber as the reinforcement and multifunctional ceramic phase as the matrix. They combine the excellent properties of high strength, high modulus, low density and chemical stability of carbon fiber with the various thermodynamic, chemical and physical functional properties of different ceramic matrices. Carbon fiber reinforced high temperature resistant ceramic matrix composites are widely used in the aerospace field, especially in the thermal protection systems and structural functional components of aircraft and aero engines.

[0003] However, the preparation process of carbon fiber reinforced high-temperature ceramic matrix composites is complex, involving multiple processes such as preform preparation, ceramic phase introduction, machining, and coating preparation, and the preparation cycle is long. The complexity of the preparation process and the long preparation cycle can easily cause local defects such as holes, bumps, scratches, and machining damage in the composite preform. These defects will expose the internal fibers and matrix of the composite material, affecting the performance of the composite product and thus affecting the application of the composite product in aircraft and aero engines.

[0004] The urgent problem to be solved in this field is how to quickly repair local defects in the preform without heating and sintering to prevent the defective parts from being oxidized and eroded by high temperature, and how to make the repaired finished product have high strength, excellent high temperature resistance and no heat damage to the carbon fiber during use. Summary of the Invention

[0005] The purpose of this invention is to provide a method for repairing local defects in carbon fiber reinforced ceramic matrix composites, which enables rapid repair of local defects in carbon fiber reinforced ceramic matrix composites without the need for high-temperature heating, and the repaired area exhibits high strength, excellent high-temperature resistance, and no thermal damage to the carbon fibers during use.

[0006] This invention provides a method for repairing local defects in carbon fiber reinforced ceramic matrix composites, comprising the following steps:

[0007] Prepare a first fiber slurry, which includes carbon fiber, water glass, and ceramic powder;

[0008] A second fiber slurry is prepared, comprising long boron nitride fibers, ceramic powder, and solvent;

[0009] A third fiber slurry is prepared, wherein the third fiber slurry comprises short boron nitride fibers, ceramic powder, polymer monomers, crosslinking agents, initiators, and solvents;

[0010] The first fiber slurry is impregnated into the local defects of the carbon fiber reinforced ceramic matrix composite material, filling 60-80% of the defects;

[0011] After the first fiber slurry has cured, the second fiber slurry is filled again to fill the remaining 60-80% of the defect. Then, the excess solvent is squeezed out.

[0012] Then fill the defect with the third fiber slurry, and then cure it at room temperature.

[0013] The advantages of this invention over the prior art are as follows: by impregnating the local defects of the carbon fiber reinforced ceramic matrix composite material with a first fiber slurry, filling 60-80% of the defect, the first fiber slurry includes carbon fiber, water glass, and ceramic powder. This allows the carbon fiber to be solidified at the bottom of the defect via water glass, while filling the carbon fiber with ceramic powder facilitates high-temperature resistance during use. Furthermore, by filling 60-80% of the defect with the first fiber slurry, a second and third fiber can be added on top of the first fiber to provide thermal insulation protection for the underlying carbon fiber, preventing oxidation at high temperatures. Simultaneously, the water glass allows the carbon fiber to solidify at room temperature, and when the external temperature is too high during use, even if the high temperature is likely to be transmitted to the surrounding carbon fiber, the solidified water glass will absorb heat, further enhancing strength and improving temperature resistance.

[0014] After the first fiber slurry has cured, the second fiber slurry is filled again to fill the remaining 60-80% of the defect. Then, the excess solvent is squeezed out, so that the long boron nitride fibers are dispersed in a three-dimensional network on the surface of the cured first fiber, and the ceramic powder is dispersed in the long boron nitride fiber network. At the same time, the defect is not completely filled, and then the long boron nitride fiber network is filled with short boron nitride fibers introduced by subsequent impregnation.

[0015] The third fiber slurry includes short boron nitride fibers, ceramic powder, polymer monomers, crosslinking agents, and initiators, thereby enabling the long and short boron nitride fibers to be cured at room temperature through polymer monomers, crosslinking agents, and initiators; at the same time, filling the boron nitride fibers with ceramic powder helps to improve high-temperature resistance during use.

[0016] By applying boron nitride fibers to the outermost layer of the defect, the high-temperature resistance of the repaired material can be improved.

[0017] Furthermore, the ceramic powder includes one or more of SiC, ZrC, ZrB2, HfC, TaC, HfB2, and TiB2 powders.

[0018] The beneficial effect of the previous step is that the ceramic powder helps to improve the high-temperature resistance of the repaired area.

[0019] Furthermore, in the preparation process of the first fiber slurry, carbon fiber and ceramic powder are mixed and then added to water glass while stirring; then sodium fluorosilicate is added and stirring is continued to obtain the first fiber slurry; the first fiber slurry is used within 0.5-5 minutes after it is prepared;

[0020] The mass ratio of carbon fiber: ceramic powder: water glass is (55-65):(10-15):(20-25);

[0021] The modulus m of the water glass is 3.2-3.4; the mass concentration of the water glass is 1.38-1.41 g / cm³. 3 .

[0022] The beneficial effect of the previous step is that the mass ratio of carbon fiber: ceramic powder: water glass is (55-65):(10-15):(20-25), which avoids excessive water glass content or high final sodium oxide content, thereby avoiding the problem of high fluidity of glassy substances when the temperature between carbon fiber and ceramic powder is 300-400℃ during use.

[0023] Furthermore, according to claim 1, the long-fiber boron nitride fiber and the short-fiber boron nitride fiber are first modified before being used to prepare the second fiber slurry and the third fiber slurry.

[0024] Furthermore, the modification process for the second and third fiber slurries involves impregnating the surfaces of long-fiber boron nitride fibers and short-fiber boron nitride fibers with silica sol, followed by drying at a temperature of 40-60°C, thereby modifying the long-fiber boron nitride fibers and short-fiber boron nitride fibers.

[0025] The beneficial effect of the previous step is that by modifying the surface of long-fiber boron nitride fibers and short-fiber boron nitride fibers, silica is attached to the surface of the modified fibers. This helps to prevent the boron nitride fibers from being oxidized and decomposed at high temperatures during use. Although silica has a high oxidation resistance temperature, it is prone to softening at higher temperatures. However, it will still adhere to the surface of the boron nitride fibers and will not affect the boron nitride fibers.

[0026] Furthermore, the second fiber slurry preparation process includes the following steps: adding the long boron nitride fiber and ceramic powder to a solvent and stirring to disperse them, thereby obtaining the second fiber slurry; the mass ratio of the long boron nitride fiber to the ceramic powder is (55-65):(10-15);

[0027] The aspect ratio of the long boron nitride fiber is (100-400):1, and the solvent is water.

[0028] The advantage of the previous step is that it facilitates the formation of a three-dimensional spatial network structure with large pores by overlapping long boron nitride fibers.

[0029] Furthermore, the preparation process of the third fiber slurry includes the following steps: mixing the polymer monomer, crosslinking agent, and solvent in proportion, and then adding short boron nitride fiber and ceramic powder and stirring.

[0030] Add the initiator and stir for 0.5-1.5 minutes to obtain the third fiber slurry; the third fiber slurry should be used within 1-5 minutes after preparation.

[0031] The advantage of the previous step is that it enables the long-fiber boron nitride fiber and the short-fiber boron nitride fiber to be uniformly dispersed and cured at room temperature, while avoiding the problem of uneven curing in different parts.

[0032] Furthermore, the mass ratio of the short boron nitride fiber, ceramic powder, polymer monomer, crosslinking agent, initiator, and solvent is (55-65):(10-15):(20-25):(0.25-1.25):(0.4-0.75):(20-30);

[0033] The aspect ratio of the short boron nitride fiber is (10-40):1.

[0034] The beneficial effect of the previous step is that, through the above material ratio of the third fiber slurry, high bonding strength can be achieved while avoiding the reduction in strength caused by excessive organic content; the short boron nitride fibers with an aspect ratio of (10-40):1 are dispersed between the grid formed by the long boron nitride fibers, improving the toughness of the repaired area and enhancing the impact resistance during use.

[0035] Furthermore, the polymerizing monomer includes a first polymerizing monomer and a second polymerizing monomer; the mass ratio of the first polymerizing monomer to the second polymerizing monomer is (60-70):(30-40);

[0036] The first polymerizing monomer includes acrylamide or methyl acrylate;

[0037] The second polymerizing monomer includes propoxyglycerol triacrylate and / or ethoxytrimethylolpropane acrylate;

[0038] The crosslinking agent is NN-methylenebisacrylamide; the solvent is water, and the solvent temperature is 40-80℃.

[0039] The advantages of the previous step are that, by using the first polymer monomer, which includes acrylamide or methyl acrylate, the curing rate is relatively fast and the curing reaction is relatively stable, avoiding unevenness of the repair surface caused by violent reaction and unstable internal structure; and the low viscosity of the first polymer monomer is conducive to dispersion.

[0040] It also benefits from a higher degree of cross-linking during high-temperature initiator-induced polymerization and curing, thus achieving high strength at the repair site, and it only decomposes at an ambient temperature of 500-600℃ during use.

[0041] The second monomers include propoxyglycerol triacrylate and / or ethoxytrimethylolpropane acrylate. During curing, the polymerization rate of the second monomers is very fast, which is conducive to rapid curing and rapid crosslinking. However, the molecular weight of the crosslinks is not very high, but it is beneficial to improve the strength during instantaneous curing.

[0042] Using NN-methylenebisacrylamide as the crosslinking agent facilitates partial crosslinking during curing, thereby increasing the strength during curing. It also facilitates further crosslinking during use after curing and repair, as the ambient temperature rises, thus increasing the strength of the repaired area.

[0043] The curing rate is increased by using a solvent temperature of 40-80℃.

[0044] Furthermore, the initiator includes a first initiator, a second initiator, and a third initiator; the mass ratio of the first initiator, the second initiator, and the third initiator is (6-7):(3-4):(0.6-1.2).

[0045] The first initiator is potassium sulfate or ammonium persulfate; the second initiator is 2,3-dimethyl-2,3-diphenylbutane; and the third initiator is sodium bisulfite or ferrous chloride.

[0046] The beneficial effect of the previous step is that, by using the first initiator and the third initiator, the polymer monomers can be rapidly cured during the repair process without violent reactions, and the polymerization reaction is stable. At the same time, the second initiator is beneficial for the finished material after repair and curing to further crosslink some of the polymer monomers under the initiation of the second initiator when exposed to the rise in external ambient temperature during use. This not only consumes the heat conducted by the environment, but also improves the strength. Detailed Implementation

[0047] To better understand the technical solution of the present invention, the present invention will be further described below with reference to specific embodiments.

[0048] Example 1:

[0049] This embodiment provides a method for repairing local defects in carbon fiber reinforced ceramic matrix composites, including the following steps:

[0050] A first fiber slurry is prepared, comprising carbon fiber, water glass, and ceramic powder; the ceramic powder comprises SiC, ZrC, HfC, and TiB2 powder.

[0051] The preparation process of the first fiber slurry involves mixing carbon fiber with ceramic powder, then adding it to water glass while stirring; then adding sodium fluorosilicate and continuing to stir to obtain the first fiber slurry; the first fiber slurry is to be used within 3 minutes after preparation.

[0052] The mass ratio of carbon fiber: ceramic powder: water glass is 60:12:22;

[0053] The modulus of the water glass is m = 3.3; the mass concentration of the water glass is 1.40 g / cm³. 3 ;

[0054] The first fiber slurry is impregnated into local defects in the carbon fiber reinforced ceramic matrix composite material, filling 70% of the defects.

[0055] A second fiber slurry is prepared, comprising long boron nitride fibers, ceramic powder, and solvent. The preparation process of the second fiber slurry includes the following steps: adding the long boron nitride fibers and ceramic powder to the solvent at a mass ratio of 60:12 and stirring to disperse, thereby obtaining the second fiber slurry.

[0056] The aspect ratio of the long boron nitride fiber is 260:1, and the solvent is water;

[0057] After the first fiber slurry has cured, the second fiber slurry is filled again to fill the remaining 70% of the defect. Then, the excess solvent is squeezed out.

[0058] A third fiber slurry is prepared, wherein the third fiber slurry comprises short boron nitride fibers, ceramic powder, polymer monomers, crosslinking agents, initiators, and solvents;

[0059] The preparation process of the third fiber slurry includes the following steps: mixing the polymer monomer, crosslinking agent, and solvent in proportion, and then adding short boron nitride fiber and ceramic powder and stirring.

[0060] Add the initiator and stir for 1 minute to obtain the third fiber slurry; the third fiber slurry should be used within 3 minutes after preparation;

[0061] The mass ratio of the short boron nitride fiber, ceramic powder, polymer monomer, crosslinking agent, initiator, and solvent is 60:12:22:0.75:0.56:25.

[0062] The aspect ratio of the short boron nitride fiber is 25:1;

[0063] The polymeric monomers include a first polymeric monomer and a second polymeric monomer; the mass ratio of the first polymeric monomer to the second polymeric monomer is 65:35.

[0064] The first monomer comprises acryloyl; the second monomer comprises propoxylated glycerol triacrylate;

[0065] The crosslinking agent is N-methylenebisacrylamide; the solvent is water, and the solvent temperature is 60°C.

[0066] The initiator comprises a first initiator, a second initiator, and a third initiator; the mass ratio of the first initiator, the second initiator, and the third initiator is 6.5:3.5:0.9.

[0067] The first initiator is potassium sulfate; the second initiator is 2,3-dimethyl-2,3-diphenylbutane; and the third initiator is sodium bisulfite.

[0068] Then fill the defect with the third fiber slurry, and then cure it at room temperature.

[0069] Example 2:

[0070] The contents that are the same as in Example 1 will not be repeated here; the different aspects of this embodiment compared to Example 1 are as follows:

[0071] This embodiment provides a method for repairing local defects in carbon fiber reinforced ceramic matrix composites, which further includes the following steps:

[0072] Before the preparation of the second and third fiber slurries, the long-fiber boron nitride fibers and short-fiber boron nitride fibers are modified. The modification process of the second and third fiber slurries involves impregnating the surface of the long-fiber boron nitride fibers and short-fiber boron nitride fibers with silica sol, and then drying them at a temperature of 50°C to modify the long-fiber boron nitride fibers and short-fiber boron nitride fibers.

[0073] The ceramic powder includes SiC, ZrB2, TaC, and HfB2;

[0074] The first fiber slurry should be used within 1 minute after it is prepared;

[0075] The mass ratio of carbon fiber: ceramic powder: water glass is 62:14:23;

[0076] The first fiber slurry was impregnated into the local defects of the carbon fiber reinforced ceramic matrix composite material, filling 78% of the defects.

[0077] The long boron nitride fiber and ceramic powder are added to a solvent at a mass ratio of 63:14 and stirred and dispersed to obtain the second fiber slurry.

[0078] The aspect ratio of the long boron nitride fiber is 380:1;

[0079] After the first fiber slurry has cured, the second fiber slurry is filled again to fill the remaining 78% of the defect. Then, the excess solvent is squeezed out.

[0080] The third fiber slurry is obtained after stirring for 1.3 minutes; the third fiber slurry is used within 2 minutes after preparation.

[0081] The mass ratio of the short boron nitride fiber, ceramic powder, polymer monomer, crosslinking agent, initiator, and solvent is 63:14:23:1.23:0.7:28.

[0082] The aspect ratio of the short boron nitride fiber is 38:1;

[0083] The polymeric monomers include a first polymeric monomer and a second polymeric monomer; the mass ratio of the first polymeric monomer to the second polymeric monomer is 68:32.

[0084] The first polymeric monomer includes methyl acrylate;

[0085] The second polymerizing monomer includes ethoxytrimethylolpropane acrylate;

[0086] The solvent is water, and the solvent temperature is 75°C;

[0087] The initiator comprises a first initiator, a second initiator, and a third initiator; the mass ratio of the first initiator, the second initiator, and the third initiator is 6.8:3.8:1.1.

[0088] The first initiator is ammonium persulfate; the third initiator is ferrous chloride.

[0089] Example 3:

[0090] The contents that are the same as in Example 1 will not be repeated here; the different aspects of this embodiment compared to Example 1 are as follows:

[0091] This embodiment provides a method for repairing local defects in carbon fiber reinforced ceramic matrix composites, which further includes the following steps:

[0092] Before the long-fiber boron nitride fibers and short-fiber boron nitride fibers are prepared into the second and third fiber slurries, they are first modified. The modification process of the second and third fiber slurries is as follows: the surface of the long-fiber boron nitride fibers and short-fiber boron nitride fibers is impregnated with silica sol and then dried at a temperature of 45°C to modify the long-fiber boron nitride fibers and short-fiber boron nitride fibers.

[0093] The ceramic powder includes SiC, ZrC, HfB2, and TiB2;

[0094] The first fiber slurry should be used within 1 minute after it is prepared;

[0095] The mass ratio of carbon fiber: ceramic powder: water glass is 57:11:21;

[0096] The first fiber slurry is impregnated into local defects in the carbon fiber reinforced ceramic matrix composite material, filling 65% of the defects.

[0097] The long boron nitride fiber and ceramic powder are added to a solvent at a mass ratio of 56:11 and stirred and dispersed to obtain the second fiber slurry.

[0098] The aspect ratio of the long boron nitride fiber is 150:1;

[0099] After the first fiber slurry has cured, the second fiber slurry is filled again to fill the remaining 65% of the defect. Then, the excess solvent is squeezed out.

[0100] The third fiber slurry is obtained after stirring for 0.6 minutes; the third fiber slurry is used within 4 minutes after preparation.

[0101] The mass ratio of the short boron nitride fiber, ceramic powder, polymer monomer, crosslinking agent, initiator, and solvent is 56:11:21:0.35:0.5:22.

[0102] The aspect ratio of the short boron nitride fiber is 16:1;

[0103] The polymeric monomers include a first polymeric monomer and a second polymeric monomer; the mass ratio of the first polymeric monomer to the second polymeric monomer is 62:38.

[0104] The first polymeric monomer includes methyl acrylate;

[0105] The second polymerizing monomer includes ethoxytrimethylolpropane acrylate;

[0106] The solvent is water, and the solvent temperature is 55°C;

[0107] The initiator comprises a first initiator, a second initiator, and a third initiator; the mass ratio of the first initiator, the second initiator, and the third initiator is 6.2:3.2:0.7.

[0108] The first initiator is ammonium persulfate; the third initiator is ferrous chloride.

[0109] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, the above-described features have similar functions to (but are not limited to) those disclosed in this application.

Claims

1. A method for repairing a local defect of a carbon fiber-reinforced ceramic matrix composite, characterized by, Includes the following steps: Prepare a first fiber slurry, which includes carbon fiber, water glass, and ceramic powder; A second fiber slurry is prepared, comprising long boron nitride fibers, ceramic powder, and solvent; The aspect ratio of the long boron nitride fiber is (100-400):1; A third fiber slurry is prepared, wherein the third fiber slurry comprises short boron nitride fibers, ceramic powder, polymer monomers, crosslinking agents, initiators, and solvents; The aspect ratio of the short boron nitride fiber is (10-40):1; The first fiber slurry is impregnated into the local defects of the carbon fiber reinforced ceramic matrix composite material, filling 60-80% of the defects. After the first fiber slurry has cured, the second fiber slurry is filled again to fill the remaining 60-80% of the defect. Then, the excess solvent is squeezed out. Then fill the defect with the third fiber slurry, and then cure it at room temperature.

2. The method of claim 1, wherein the carbon fiber reinforced ceramic matrix composite is a carbon fiber reinforced silicon carbide matrix composite. The ceramic powder includes one or more of SiC, ZrC, ZrB2, HfC, TaC, HfB2, and TiB2 powders.

3. The method for repairing local defects in carbon fiber reinforced ceramic matrix composites according to claim 1, characterized in that, The preparation process of the first fiber slurry involves mixing carbon fiber with ceramic powder, then adding it to water glass while stirring; then adding sodium fluorosilicate and continuing to stir to obtain the first fiber slurry; the first fiber slurry is to be used within 0.5-5 minutes after preparation. The mass ratio of carbon fiber: ceramic powder: water glass is (55-65):(10-15):(20-25).

4. The method for repairing local defects in carbon fiber reinforced ceramic matrix composites according to claim 1, characterized in that, The long-fiber boron nitride fibers and short-fiber boron nitride fibers are modified before being used to prepare the second and third fiber slurries.

5. The method for repairing local defects in carbon fiber reinforced ceramic matrix composites according to claim 4, characterized in that, The modification process for the second and third fiber slurries involves impregnating the surfaces of long-fiber boron nitride fibers and short-fiber boron nitride fibers with silica sol, followed by drying at a temperature of 40-60℃, thereby modifying the long-fiber boron nitride fibers and short-fiber boron nitride fibers.

6. The method for repairing local defects in carbon fiber reinforced ceramic matrix composites according to claim 1, characterized in that, The second fiber slurry preparation process includes the following steps: adding the long boron nitride fiber and ceramic powder to a solvent and stirring to disperse them, thereby obtaining the second fiber slurry; the solvent is water.

7. The method for repairing local defects in carbon fiber reinforced ceramic matrix composites according to claim 1, characterized in that, The preparation process of the third fiber slurry includes the following steps: mixing the polymer monomer, crosslinking agent, and solvent in proportion, and then adding short boron nitride fiber and ceramic powder and stirring. Add the initiator and stir for 0.5-1.5 minutes to obtain the third fiber slurry; the third fiber slurry should be used within 1-5 minutes after preparation.

8. The method for repairing local defects in carbon fiber reinforced ceramic matrix composites according to claim 1, characterized in that, The mass ratio of the short boron nitride fiber, ceramic powder, polymer monomer, crosslinking agent, initiator and solvent is (55-65): (10-15): (20-25): (0.25-1.25): (0.4-0.75): (20-30).

9. The method for repairing local defects in carbon fiber reinforced ceramic matrix composites according to claim 8, characterized in that, The polymeric monomers include a first polymeric monomer and a second polymeric monomer; the mass ratio of the first polymeric monomer to the second polymeric monomer is (60-70):(30-40). The first polymerizing monomer includes acrylamide or methyl acrylate; The second polymerizing monomer includes propoxyglycerol triacrylate and / or ethoxytrimethylolpropane acrylate; The crosslinking agent is NN-methylenebisacrylamide; the solvent is water, and the solvent temperature is 40-80℃.

10. The method for repairing local defects in carbon fiber reinforced ceramic matrix composites according to claim 8, characterized in that, The initiator comprises a first initiator, a second initiator, and a third initiator; the mass ratio of the first initiator, the second initiator, and the third initiator is (6-7):(3-4):(0.6-1.2). The first initiator is potassium sulfate or ammonium persulfate; the second initiator is 2,3-dimethyl-2,3-diphenylbutane; and the third initiator is sodium bisulfite or ferrous chloride.