Method for optimizing connection joint of continuous carbon fiber reinforced SiC matrix composite

Abstract

The present invention discloses a method for optimizing the connection joint of a continuous carbon fiber reinforced SiC matrix composite material, which includes mixing and dispersing phenolic resin, solvent, curing agent and inert filler to form a slurry; performing special-shaped interface machining, connection surface reinforcement and surface treatment at the connection interface on the surface of the Cf / C composite material matrix to be connected; uniformly coating the slurry between the connection surfaces to form a slurry layer; pair-connecting the Cf / C composite materials, and forming a porous connection layer after applying pressure, curing and carbonization; wrapping the connecting piece by the embedding method to perform reactive infiltration, and in-situ generating a SiC composite material phase at the pores of the Cf / C matrix and the porous connection layer. This method increases the connection area, improves the mechanical strength and stability of the connection, and improves the overall failure limit strength of the connecting piece.

Description

Technical Field

[0001] The invention belongs to the technical field of continuous carbon fiber reinforced SiC-based composite material connection, and particularly relates to an interface structure design method for synchronous reaction connection of SiC-based composite materials. Background Art

[0002] With the rapid development of fields such as aerospace, the demand for materials that can withstand high temperatures and extreme environments is increasing. Fiber-reinforced SiC-based composites are attracting widespread attention due to their excellent high-temperature performance, high specific strength and modulus, high degree of densification, and long life. They are currently widely used in the manufacture of aerospace vehicles, aircraft engines, missile nozzles, brake discs, and optical components.

[0003] Fiber-reinforced SiC-based composite materials are usually very complex and large in size. In addition, the SiC-based composite material itself has the characteristics of high hardness and high melting point, which not only increases the difficulty of preparing complex parts, but also increases the processing cost and increases the product preparation cycle. Therefore, it is necessary to adopt a connection method to achieve the preparation of complex-shaped and large-sized structural parts. Connectors prepared by reaction connection have the characteristics of wide application range and not easy to deform and are widely used. However, since the connecting layer is relatively thin, it is difficult to accurately control the connection position of the resin slurry during the coating process, and when the butt connection is usually adopted, the connection area is small and high strength and connection stability cannot be guaranteed. Therefore, it is necessary to structurally design the connection interface, increase the connection area, and strengthen the connection joint. Summary of the Invention

[0004] In order to solve the problems existing in the existing connection technology, such as the difficulty in accurately controlling the connection position of the connection layer, the small connection area actually involved in the connection, and the inability to guarantee the connection strength and stability, the purpose of the present invention is to provide a method for optimizing the connection joints of continuous carbon fiber reinforced SiC-based composite materials.

[0005] The present invention is achieved through the following technical solutions.

[0006] According to an embodiment of the present invention, a method for optimizing a continuous carbon fiber reinforced SiC-based composite material connection joint is provided, comprising the following steps:

[0007] (a) uniformly mixing a phenolic resin, a solvent, a curing agent, and an inert filler in a mass ratio of (1-2):(1-2):(0.1-0.3):(0.35-0.5), and dispersing the mixture to form a slurry;

[0008] (b) C f The surface of the C / C composite material matrix to be connected is processed into a special-shaped interface. fReinforce the C / C composite connection joint and perform surface treatment on the connection interface processed by the special-shaped interface;

[0009] (c) Uniformly apply the said slurry on the treated C / C composite connection surface to form a slurry layer; f between the C / C composite connection surfaces to form a slurry layer;

[0010] (d) Pair and connect the C / C composites coated with the slurry layer, and form a porous connection layer after applying pressure, curing, and carbonization; f Pair and connect the C / C composites coated with the slurry layer, and form a porous connection layer after applying pressure, curing, and carbonization;

[0011] (e) Place the connecting piece on silicon particles, wrap the connecting piece by the embedding method, perform reactive infiltration, and in-situ generate SiC composite phases at the pores of the C / C matrix and the porous connection layer. f in-situ generate SiC composite phases at the pores of the C / C matrix and the porous connection layer.

[0012] Preferably, the solvent is ethylene glycol, diethylene glycol, triethylene glycol or polyethylene glycol.

[0013] Preferably, the curing agent is benzenesulfonyl chloride or petroleum sulfonic acid.

[0014] Preferably, the inert filler is a mixture of SiC powder, graphite powder and short carbon fiber; the particle size of the SiC powder is 1 - 1.5 μm, the graphite powder is flaky graphite, and the particle size is 25 - 30 μm.

[0015] Preferably, the C / C composite is prepared by chemical vapor infiltration or resin impregnation carbonization of unidirectional 1D fiber-reinforced carbon fiber preform, bidirectional 2D fiber-reinforced carbon fiber preform, 2.5D fiber-reinforced carbon fiber preform or 3D fiber-reinforced carbon fiber preform. f Preferably, the C / C composite is prepared by chemical vapor infiltration or resin impregnation carbonization of unidirectional 1D fiber-reinforced carbon fiber preform, bidirectional 2D fiber-reinforced carbon fiber preform, 2.5D fiber-reinforced carbon fiber preform or 3D fiber-reinforced carbon fiber preform.

[0016] Preferably, the connection surface of the C / C composite includes a plane, a special-shaped surface or a T-shaped joint, and the special-shaped surface is a serrated, circular arc or concave-convex interface. f Preferably, the connection surface of the C / C composite includes a plane, a special-shaped surface or a T-shaped joint, and the special-shaped surface is a serrated, circular arc or concave-convex interface.

[0017] Preferably, the reinforcement includes carbon cloth bonding and adding reinforcing members;

[0018] Carbon cloth bonding includes cutting carbon fiber cloth, performing oxidation treatment at 500°C - 600°C for 1 - 2 h in an air furnace to increase surface activity, coating adhesive slurry on the oxidized carbon cloth, and pasting it on the connection joint.

[0019] Preferably, the surface roughness of the C / C composite connection surface is 7 - 13 μm. f Preferably, the surface roughness of the C / C composite connection surface is 7 - 13 μm.

[0020] Preferably, in step (d), for the T-shaped joint of the connection interface, reinforce it with carbon cloth coated with slurry, and the reinforcement method is to use Cf The C / C composite material is cut into a prism with right-angled sides. Adhesive slurry is applied to the two side surfaces of the right-angled sides, and it is fixed by fitting with both sides of the T-shaped connection joint.

[0021] Preferably, the curing is carried out by applying a curing pressure of 0.5 - 1 MPa, heating at 70°C - 80°C for 1 h - 2 h, then raising the temperature to 150°C - 180°C and heating for 10 h - 15 h, and then raising the temperature to 700°C - 900°C at a heating rate of 1°C / min and holding for 4 - 6 h for carbonization.

[0022] Preferably, the connecting piece is placed on the silicon particles at the bottom of the graphite crucible, and the connecting piece is wrapped by the embedding method, and reaction infiltration is carried out at a temperature of 1500°C - 1600°C for a holding time of 10 min - 40 min.

[0023] Due to the adoption of the above technical solutions, the present invention has the following beneficial effects:

[0024] 1. By adding inert fillers to the phenolic resin mixed slurry in the present invention, the problems of large volume shrinkage and cracks during the curing and carbonization processes in the case of pure resin connection are solved. And through the subsequent curing and carbonization processes, the preparation and connection of the SiC-based composite material are realized synchronously. It has the advantages of simple process, low raw material price, short production cycle, and matching of the thermal expansion coefficients of the connection layer and the matrix.

[0025] 2. On the basis of synchronously reacting and connecting to prepare the SiC-based composite material connecting piece, the interface structure of the connection joint is designed to reinforce the connection joint, which not only increases the specific connection area of the connection surface but also improves the connection strength.

[0026] 3. The design of the special-shaped interface not only enables the connection joint to have the bonding effect of the adhesive but also increases the mechanical biting effect, making the connection of the connecting piece more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings described herein are used to provide a further understanding of the present invention, form a part of this application, and do not constitute an improper limitation to the present invention. In the drawings:

[0028] Figure 1 It is a schematic diagram of the C / C-SiC composite material connecting piece with a serrated interface; f

[0029] Figure 2 It is a schematic diagram of the C / C-SiC composite material connecting piece with an arc-shaped interface; f

[0030] Figure 3 It is a schematic diagram of the C / C-SiC composite material connecting piece with a concave-convex interface; f ​

[0031] Figure 4 It is a T-shaped connection, and the triangular prism-fixed C f / Schematic diagram of the C-SiC composite material connector;

[0032] Figure 5 It is a T-shaped connection, and the carbon cloth-fixed C f / Schematic diagram of the C-SiC composite material connector;

[0033] Figure 6 It is a microscopic schematic diagram of the concave-convex interface design. Specific implementation manners

[0034] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. Here, the illustrative embodiments of the present invention and the description are used to explain the present invention, but do not limit the present invention.

[0035] An embodiment of the present invention provides a method for designing a continuous carbon fiber reinforced SiC matrix composite connection joint, including the following steps:

[0036] Step 1, mix phenolic resin, solvent (ethylene glycol, diethylene glycol, triethylene glycol or polyethylene glycol), curing agent (benzenesulfonyl chloride or petroleum sulfonic acid) and inert filler (SiC powder, graphite powder and short carbon fibers) evenly according to the mass ratio of (1-2):(1-2):(0.1-0.3):(0.30-0.5), and form a slurry after dispersion.

[0037] Among them, the particle size of the SiC powder in the inert filler is 1-1.5 μm, and the graphite powder is flaky graphite with a particle size of 25-30 μm.

[0038] In step 1, when phenolic resin is used as the adhesive for reaction connection, it is necessary to have certain pores after curing and carbonization to allow liquid silicon to infiltrate. Among them, benzenesulfonyl chloride is used as the curing agent. When adding a solvent and a pore-forming agent such as benzenesulfonyl chloride or petroleum sulfonic acid, certain pores will be generated after the phenolic resin is cured, and the content can adjust the pores.

[0039] Among them, phenolic resin usually undergoes volume shrinkage after curing, resulting in defects such as large-size cracks. A large amount of free silicon will be generated during subsequent carbonization and reaction infiltration process connections, affecting the connection strength. Adding inert fillers such as SiC powder, graphite powder or short carbon fibers can effectively prevent the generation of cracks and large pores caused by volume shrinkage and reduce the formation of free silicon.

[0040] Step 2, perform special-shaped interface processing on the surface of the C f / C composite material matrix, for the C fReinforce the connection surface of the C / C composite material to increase the connection area, and perform surface treatment on the connection interface processed by the special-shaped interface.

[0041] Among them, C f The C / C composite material is prepared by chemical vapor infiltration or resin impregnation and carbonization of a unidirectional 1D fiber-reinforced carbon fiber preform, a bidirectional 2D fiber-reinforced carbon fiber preform, a 2.5D fiber-reinforced carbon fiber preform, or a 3D fiber-reinforced carbon fiber preform.

[0042] C f The special-shaped connection surface of the C / C composite material is processed into a flat surface, a special-shaped surface, or a T-shaped joint. The special-shaped surface includes a serrated, arc-shaped, or concave-convex connection interface. In one embodiment, the length of each tooth of the serrated shape is 5-15 mm, and the height is 2-10 mm; the radius of each arc of the arc-shaped is 5-10 mm; the width of each groove of the concave-convex shape is 5-10 mm, the depth of the groove is 5-10 mm, and the interval between each groove is 5-10 mm.

[0043] The main reinforcement methods include two methods: carbon cloth bonding and adding reinforcement parts.

[0044] For carbon cloth bonding reinforcement, the carbon fiber cloth is cut, and it is heat-insulated at 500 °C - 600 °C in an air furnace for 1-2 h for oxidation treatment to increase surface activity. An adhesive slurry is coated on the carbon cloth after oxidation treatment and pasted on the connection joint.

[0045] Through the special-shaped design of the connection interface and appropriate reinforcement methods, on the one hand, the specific connection area of the connection plane is increased, and on the other hand, the special-shaped design will also provide some mechanical biting forces to enhance its connection strength.

[0046] Step 3, uniformly coat the slurry on the processed C f C of the C / C composite material f Between the connection surfaces of the C / C composite material, a slurry layer is formed after docking.

[0047] Among them, the surface roughness of the connected parts has a great influence on the wettability of the slurry and the bonding property of the connection. Excessive roughness will result in poor bonding between the adhesive and the matrix, while too small roughness will reduce the wettability of the adhesive and the matrix, resulting in the lack of adhesive in the connection layer. When the surface roughness of the C / C composite material connection is controlled at 7-13 μm, the connection is better. f When the surface roughness of the C / C composite material connection is controlled at 7-13 μm, the connection is better.

[0048] Step 4, pair and connect the C / C composite material coated with the slurry layer, and use the carbon cloth coated with the slurry to reinforce the connection interface with a T-shaped joint. After applying pressure, curing, and carbonization, a porous connection layer is formed. f For the reinforcement method of the T-shaped joint, C

[0049] For the T-shaped joint reinforcement method, Cf The C / C composite material is cut into a right prism, and an adhesive paste is applied to two side surfaces of the right-angle sides, and then it is fixed by fitting with both sides of the T-shaped connection joint; then a paste is applied to the treated carbon cloth and the reinforcement, and it is placed at the connection interface.

[0050] Apply a curing pressure of 0.5 - 1 MPa to the paired-connected C f / C composite material, cure it by heating at 70 - 80 °C for 1 - 2 h, raise the temperature to 150 - 180 °C and heat for 10 - 15 h, carbonize it at a temperature of 700 - 900 °C with a heating rate of 1 °C / min and keep the temperature for 4 - 6 h to form a porous carbon connection layer.

[0051] Among them, applying pressure during curing is to squeeze out air bubbles and excess paste to reduce the generation of defects. The thickness of the connection layer is achieved through the curing pressure. On the premise of not generating defects, the greater the pressure, the thinner the connection layer and the better the connection effect.

[0052] Step 5: Place the connector on the Si particles at the bottom of the graphite crucible, and then use the embedding method to wrap the connector. React and infiltrate it in a nitrogen atmosphere at a temperature of 1500 °C - 1600 °C for a holding time of 10 - 40 min, and in C f / C matrix and in-situ generate SiC composite material phase at the pores of the porous connection layer.

[0053] Among them, the embedding silicon infiltration connection can realize preparation and connection synchronously, save costs and reduce the experimental period. At the same time, the silicon carbide connection layer also has advantages such as matching thermal expansion coefficients, making the connection effect better.

[0054] The following further illustrates the present invention through different embodiments.

[0055] Example 1

[0056] 1) Mix 10.0 g of phenolic resin, 10.0 g of ethylene glycol, 1.5 g of benzenesulfonyl chloride, 0.1 g of short-cut carbon fiber, 1.5 g of SiC powder, and 1.5 g of graphite powder evenly, pour them into a suction flask, stir them in a water bath at 45 °C and vacuum filter to remove air bubbles, and wait for the temperature to drop to room temperature for standby.

[0057] 2) As Figure 1 shown, cut the C f / C composite material unidirectional 1D fiber-reinforced carbon fiber preform into blocks 1 and 3 with dimensions of 40 mm × 40 mm × 10 mm, and cut it along the midline of the 40 mm × 40 mm surface into two complementary serrated interfaces 2, where the length of each tooth is 10 mm and the height is 5 mm. Polish the two complementary serrated surfaces with sandpaper to make their roughness the same, which is 10 μm.

[0058] Apply the prepared slurry on the surface of the serrated joint surface and reinforce it. Cut the carbon fiber cloth and perform oxidation treatment in an air furnace at 550 °C for 1.5 h to increase surface activity. Apply the adhesive slurry on the oxidized carbon cloth and wrap it around the joint.

[0059] 3) Apply the slurry evenly on the treated C f / C composite C f / C composite joint surfaces, and form a slurry layer after docking.

[0060] 4) Couple the C f / C composites coated with the slurry layer. Apply a pressure of 0.5 MPa, place the connector in an oven, pre-cure at 70 °C for 2 h, and complete curing at 150 °C for 15 h. Place the cured connector in a tube furnace, and under a nitrogen atmosphere, heat up to 900 °C and hold for 4 h for carbonization.

[0061] 5) Place the carbonized sample in a graphite crucible, wrap it with silicon particles, and then place it in a vacuum silicon infiltration furnace. Heat up to 1600 °C and hold for 10 min to obtain a C f / C-SiC composite connector with a serrated interface.

[0062] Example 2

[0063] 1) Mix 10.0 g of phenolic resin, 12.0 g of diethylene glycol, 1.5 g of petroleum sulfonic acid, 0.5 g of chopped carbon fiber, 1.6 g of SiC powder, and 1.6 g of graphite powder evenly, pour them into a suction flask, stir in a water bath at 45 °C and vacuum filter to remove bubbles, and wait for the temperature to drop to room temperature for standby.

[0064] 2) As Figure 2 shown, cut the C f / C composite two-way 2D fiber-reinforced carbon fiber preform into blocks 4 and 6 with dimensions of 40 mm × 40 mm × 10 mm, and cut along the midline of the 40 mm × 40 mm surface into two mutually complementary arc-shaped interfaces 5, where the radius of each arc is 5 mm, and the arcs are distributed in an alternating concave-convex pattern. Polish the two mutually complementary arc surfaces with sandpaper to make their roughness the same at 7 μm.

[0065] Apply the prepared slurry on the surface of the arc joint surface and reinforce it. Cut the carbon fiber cloth and perform oxidation treatment in an air furnace at 600 °C for 1 h to increase surface activity. Apply the adhesive slurry on the oxidized carbon cloth and wrap it around the joint.

[0066] 3) Apply the slurry evenly on the treated C f / C composite C f / C composite joint surfaces, and form a slurry layer after docking.

[0067] 4) Pair the C coated with the slurry layer with the C / C composite, then apply a pressure of 0.7 MPa. Put the connector into an oven, pre-cure it at 75 °C for 1.5 h, and complete the curing at 160 °C for 12 h. Put the cured connector into a tubular furnace, and under the atmosphere of nitrogen, heat it up to 800 °C and keep it for 5 h for carbonization. f / C composite pair is connected, and then under the application of a pressure of 0.7 MPa, the connector is placed in an oven, pre-cured at 75 °C for 1.5 h, and cured at 160 °C for 12 h. The cured connector is placed in a tubular furnace, and under the atmosphere of nitrogen, heated to 800 °C and held for 5 h for carbonization.

[0068] 5) Put the carbonized sample into a graphite crucible, wrap it with silicon particles, and then put it into a vacuum silicon infiltration furnace. Heat it up to 1550 °C and keep it for 40 min to obtain a C / C-SiC composite connector with a circular arc interface. f / C-SiC composite connector.

[0069] Example 3

[0070] 1) Mix 15.0 g of phenolic resin, 15.0 g of diethylene glycol, 2.5 g of benzenesulfonyl chloride, 0.4 g of chopped carbon fiber, 2.3 g of SiC powder, and 2.3 g of graphite powder evenly, pour them into a suction flask, stir them in a water bath at 45 °C and vacuum filter to remove bubbles. After the temperature drops to room temperature, set it aside for use.

[0071] 2) As shown, cut the 2.5D fiber-reinforced carbon fiber preform of the C / C composite into blocks 7 and 9 with dimensions of 40 mm × 40 mm × 10 mm, and cut it along the midline of the 40 mm × 40 mm surface into two complementary concave-convex interfaces 8, where the width of each groove is 5 mm, the depth of the groove is 5 mm, and the interval between each groove is 5 mm. Polish the two complementary concave-convex surfaces with sandpaper to make their roughness the same, which is 8 μm. Figure 3 shown, cut the C / C composite 2.5D fiber-reinforced carbon fiber preform into blocks 7 and 9 with dimensions of 40 mm × 40 mm × 10 mm, and cut it along the midline of the 40 mm × 40 mm surface into two complementary concave-convex interfaces 8, where the width of each groove is 5 mm, the depth of the groove is 5 mm, and the interval between each groove is 5 mm. Polish the two complementary concave-convex surfaces with sandpaper to make their roughness the same, which is 8 μm. f / C composite 2.5D fiber-reinforced carbon fiber preform is cut into blocks 7 and 9 with dimensions of 40 mm × 40 mm × 10 mm, and cut along the midline of the 40 mm × 40 mm surface into two complementary concave-convex interfaces 8, where the width of each groove is 5 mm, the depth of the groove is 5 mm, and the interval between each groove is 5 mm. The two complementary concave-convex surfaces are polished with sandpaper to make their roughness the same, which is 8 μm.

[0072] Apply the prepared slurry on the surface of the concave-convex connection surface and reinforce it. Cut the carbon fiber cloth and oxidize it in an air furnace at 500 °C for 2 h to increase the surface activity. Apply the adhesive slurry on the oxidized carbon cloth and wrap it around the connection joint.

[0073] 3) Apply the slurry evenly between the C / C composite connection surfaces of the treated C / C composite, and form a slurry layer after docking. f / C composite connection surfaces of the treated C / C composite, and form a slurry layer after docking. f / C composite connection surfaces of the treated C / C composite, and form a slurry layer after docking.

[0074] 4) Pair the C / C composite coated with the slurry layer, apply a pressure of 1 MPa, put the connector into an oven, pre-cure it at 75 °C for 2 h, and complete the curing at 170 °C for 10 h. Put the cured connector into a tubular furnace, and under the atmosphere of nitrogen, heat it up to 850 °C and keep it for 6 h for carbonization. f / C composite pair coated with the slurry layer is connected, under the application of a pressure of 1 MPa, the connector is placed in an oven, pre-cured at 75 °C for 2 h, and cured at 170 °C for 10 h. The cured connector is placed in a tubular furnace, and under the atmosphere of nitrogen, heated to 850 °C and held for 6 h for carbonization.

[0075] 5) Place the carbonized sample into a graphite crucible, wrap it with silicon particles, and then put it into a vacuum silicon infiltration furnace. Heat it up to 1550 °C and hold for 30 min to obtain C with a concave-convex interface f / C-SiC composite connector. The microstructure design of the concave-convex interface is shown in Figure 6 the figure.

[0076] Example 4 (Prism reinforcement)

[0077] 1) Mix 20.0 g of phenolic resin, 20.0 g of polyethylene glycol, 1.0 g of benzenesulfonyl chloride, 0.2 g of chopped carbon fiber, 2.0 g of SiC powder, and 2.0 g of graphite powder evenly, pour them into a suction flask, stir in a water bath at 45 °C and vacuum filter to remove bubbles, and wait for the temperature to drop to room temperature for later use.

[0078] 2) As Figure 4 shown in the figure, cut the C f / C composite 3D fiber-reinforced carbon fiber preform into blocks with dimensions of 10 = 40 mm × 30 mm × 10 mm, 14 = 40 mm × 40 mm × 10 mm, and two right triangular prisms 11 and 12 with a height of 40 mm and a right-angled side of 10 mm. Use sandpaper to polish the planes of the T-shaped column block 10 with dimensions of 40 mm × 10 mm, the plane of the T-shaped bottom block 14 with dimensions of 40 mm × 40 mm, and the two mutually perpendicular planes of the right triangular prisms 11 and 12 with dimensions of 40 mm × 10 mm to make their roughness the same at 12 μm.

[0079] Apply the prepared slurry on the surface of the concave-convex connection surface and carry out reinforcement. Cut the carbon fiber cloth and perform oxidation treatment in an air furnace at 550 °C for 2 h to increase surface activity. Apply the adhesive slurry on the oxidized carbon cloth and wrap it around the connector.

[0080] 3) Evenly apply the slurry between the processed C f / C composite C f / C composite connection surfaces. After docking, a slurry layer 13 is formed.

[0081] 4) Pair and connect the C f / C composites coated with the slurry layer, and use the carbon cloth coated with the slurry to cut the C f / C composites into right triangular prisms. The materials form T-shaped joints 10 and 14, and the right triangular prisms 11 and 12 are placed along the right-angled sides on both sides of the T-shaped joint as reinforcement, and a curing pressure of 0.9 MPa is applied. Then put it into an oven, pre-cure at 70 °C for 2 h, and complete curing at 170 °C for 12 h. Put the cured connector into a tube furnace, and under the atmosphere of nitrogen, heat it up to 750 °C and hold for 4.5 h for carbonization.

[0082] 5) Put the carbonized sample into a graphite crucible, wrap it with silicon particles, and then put it into a vacuum silicon infiltration furnace. Heat it up to 1550 °C and keep it warm for 30 min to obtain the C fixed by a triangular prism f / C-SiC composite material connector.

[0083] Example 5 (carbon cloth reinforcement)

[0084] 1) Put 18.0 g of phenolic resin, 18.0 g of ethylene glycol, 3.0 g of benzenesulfonyl chloride, 0.4 g of chopped carbon fiber, 1.8 g of SiC powder, and 1.8 g of graphite powder into a suction flask. Stir in a water bath at 45 °C and vacuum filter to remove bubbles. After the temperature drops to room temperature, set aside.

[0085] 2) As Figure 5 shown, cut the C f / C composite material into T-shaped columns 15 with dimensions of 15 = 40 mm × 30 mm × 10 mm and 19 = 40 mm × 40 mm × 10 mm. Sand the 40 mm × 10 mm plane of the block-shaped T-shaped column 15 and the 40 mm × 40 mm plane of the block-shaped T-shaped bottom 19 to make their roughness the same at 9 μm.

[0086] Apply the prepared slurry on the surface of the joint surface and carry out reinforcement. Cut the carbon fiber cloth and keep it in an air furnace at 500 °C for 2 h for oxidation treatment to increase surface activity. Apply the adhesive slurry on the oxidized carbon cloth and wrap it around the joint.

[0087] 3) Uniformly apply the slurry between the C f / C composite materials of the treated C f / C composite material joint surfaces. After docking, a slurry layer 18 is formed.

[0088] 4) Flatten the T-shaped joints 15 and 19 formed by the materials and the carbon cloths 16 and 17 coated with slurry after treatment along both sides of the T-shaped joint, and apply a curing pressure of 1 MPa to prevent warping. Then put it into an oven, pre-cure at 80 °C for 1 h, and complete curing at 180 °C for 10 h. Put the cured connector into a tube furnace, and under the atmosphere of nitrogen, heat it up to 700 °C and keep it warm for 6 h for carbonization.

[0089] 5) Put the carbonized sample into a graphite crucible, wrap it with silicon particles, and then put it into a vacuum silicon infiltration furnace. Heat it up to 1500 °C and keep it warm for 30 min to obtain the T-shaped joint C fixed by carbon cloth connection f / C-SiC composite material connector.

[0090] Comparative Example 1

[0091] 1) Mix 10.0 g of phenolic resin, 10.0 g of ethylene glycol, 1.5 g of benzenesulfonyl chloride, 0.1 g of chopped carbon fiber, 1.5 g of SiC powder, and 1.5 g of graphite powder evenly, pour them into a suction flask, stir in a water bath at 45 °C and vacuum filter to remove air bubbles, and wait for the temperature to drop to room temperature for later use.

[0092] 2) Cut the C f / C composite material into blocks with dimensions of 40 mm × 20 mm × 10 mm, and sand the 20 mm × 10 mm surface to be joined with 800-mesh sandpaper to keep the same roughness of 8 μm.

[0093] 3) Coat the prepared slurry on the surface of the joining surface for butt joint. Apply a pressure of 0.7 MPa, put the joined parts into an oven, pre-cure at 75 °C for 2 h, and complete curing at 160 °C for 10 h. Put the cured joined parts into a tube furnace, and under a nitrogen atmosphere, heat up to 850 °C and hold for 6 h for carbonization.

[0094] 4) Put the carbonized sample into a graphite crucible, wrap it with silicon particles, and then put it into a vacuum silicon infiltration furnace, heat up to 1600 °C and hold for 40 min to obtain a C f / C-SiC composite material joined part.

[0095] The following Table 1 shows the performance indexes of the C f / C-SiC composite material joined parts prepared in Examples 1-5 and Comparative Examples of the present invention.

[0096] Table 1

[0097]

[0098] Among them, the specific joining area of the joining surface is calculated according to the following formula:

[0099] Specific joining area = actual joining area / planar joining area of the comparative example

[0100] It can be seen from Table 1 that under the condition of the same curing pressure (0.7 MPa) and similar joining layer thickness, the joining surface area (157%) obtained by the method of the present invention is much larger than that of the comparative example. The specific joining area of the specially shaped joining interface has varying degrees of improvement compared to the joining area of the planar joining. This is equivalent to that under the premise of the same bearing capacity, due to the increase in the joining area, the force borne per unit area will decrease, thereby increasing the overall failure limit strength. Through experimental verification, compared with a single planar joining, the joining strength of the joined parts with specially shaped design and reinforcement has increased by more than 20%.

[0101] The present invention is not limited to the above embodiments. Based on the technical solutions disclosed in the present invention, those skilled in the art can make some substitutions and deformations to some of the technical features without creative labor according to the disclosed technical content, and these substitutions and deformations are all within the protection scope of the present invention.

Claims

1. A method for optimizing the joint of continuous carbon fiber reinforced SiC matrix composite, characterized in that, Comprising the following steps: (a) Mix phenolic resin, solvent, curing agent and inert filler evenly according to the mass ratio of (1 - 2):(1 - 2):(0.1 - 0.3):(0.35 - 0.5), and form a slurry after dispersion; The inert filler is a mixture of SiC powder, graphite powder and chopped carbon fiber; the particle size of the SiC powder is 1 - 1.5 μm, the graphite powder is flaky graphite with a particle size of 25 - 30 μm; (b) Perform special-shaped interface machining on the surface to be joined of the C f / C composite matrix, reinforce the C f / C composite joint, and perform surface treatment on the connection interface after special-shaped interface machining; Reinforcement is carried out including carbon cloth lamination and adding reinforcing members; Carbon cloth lamination includes cutting carbon fiber cloth, performing oxidation treatment at 500°C - 600°C for 1 - 2 h in an air furnace to increase surface activity, coating an adhesive slurry on the oxidized carbon cloth, and pasting it on the connection joint; (c) Uniformly apply the said slurry on the treated connection surface between C f / C composite materials to form a slurry layer; (d) Pairwise connect the C coated with the slurry layer f / C composite materials, and form a porous connection layer after applying pressure, curing, and carbonization; Reinforce the carbon cloth with a coated paste for a T-shaped joint as the connection interface. The reinforcement method is to cut the C f / C composite material into a right-angled prism, apply an adhesive paste on the two side surfaces of the right-angled sides, and fit and fix them to both sides of the T-shaped connection joint; (e) Place the connecting piece on the silicon particles, wrap the connecting piece by the embedding method, and carry out reactive infiltration to in-situ generate SiC composite phases at the pores of the C f / C matrix and the porous connecting layer.

2. The method according to claim 1, wherein The solvent is ethylene glycol, diethylene glycol, triethylene glycol or polyethylene glycol; The curing agent is benzenesulfonyl chloride or petroleum sulfonic acid.

3. The method according to claim 1, characterized in that, The said C f / C composite material is obtained by chemical vapor infiltration or resin impregnation and carbonization of unidirectional 1D fiber reinforced carbon fiber preform, bidirectional 2D fiber reinforced carbon fiber preform, 2.5D fiber reinforced carbon fiber preform or 3D fiber reinforced carbon fiber preform.

4. The method according to claim 1, characterized in that, The said C f The surface roughness of the joint surface of the C / C composite material is 7 to 13 μm.

5. The method according to claim 1, wherein The curing is to apply a curing pressure of 0.5 - 1 MPa, heat at 70°C - 80°C for 1 - 2 h, raise the temperature to 150°C - 180°C and heat for 10 - 15 h, then raise the temperature to 700°C - 900°C at a heating rate of 1°C / min, and keep warm for 4 - 6 h for carbonization.

6. The method according to claim 1, characterized in that, Place the connecting piece on the silicon particles at the bottom of the graphite crucible, wrap the connecting piece by the embedding method, and carry out reaction infiltration at a temperature of 1500°C - 1600°C and a holding time of 10 min - 40 min.

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