SiC / SiC composite material stitching repair method and application

Abstract

The application belongs to the technical field of ceramic matrix composite material repair, and relates to a SiC / SiC composite material suture repair method and application. The method can repair the overall defect in the thickness direction of the SiC / SiC composite material by designing a matched suture interface, using a repair body and a suture line made of the same material as the body and being fixed, and combining a densification and reinforcement process, and can ensure that there is a continuous fiber connection between the repaired part and the body, thereby expanding the application range of the SiC / SiC composite material repair, significantly improving the mechanical properties of the composite material after repair, enhancing the reliability and service life of the composite material, and meeting the needs of related fields for high-performance ceramic matrix composite material repair.

Description

Technical Field

[0001] This invention belongs to the field of ceramic matrix composite material repair technology, and particularly relates to a method and application of suture repair of SiC / SiC composite materials. Background Technology

[0002] Continuous ceramic fiber reinforced ceramic matrix composites, represented by SiC / SiC composites, possess the advantages of ceramic materials such as high temperature resistance, high strength, oxidation resistance, and corrosion resistance. At the same time, due to the reinforcement and toughening effect of continuous ceramic fibers, they also have good toughness and impact resistance, and have broad application prospects in high-tech fields such as aviation, aerospace, and nuclear energy.

[0003] Due to the high cost of raw materials, complex manufacturing processes, and long development cycles, SiC / SiC composite components are very expensive to manufacture. Under extreme service conditions such as high temperature, oxidation, high stress, gas erosion, and foreign object impact, SiC / SiC composite components may experience localized damage and failure. Components also face the risk of localized damage during production due to accidental bumps or impacts. Localized damage leading to the failure or scrapping of the entire component incurs significant economic and time costs. Therefore, how to repair damaged areas of SiC / SiC composite components to restore their serviceability is a pressing problem that needs to be solved in the field of SiC / SiC composite component manufacturing.

[0004] Currently, repair technologies for continuous fiber reinforced ceramic matrix composites have several shortcomings. Firstly, existing repair methods mostly focus on repairing surface damage, failing to address overall defects along the thickness direction, thus limiting repair scenarios. Secondly, existing repair technologies lack fiber connections between the repair material and the substrate material. Since continuous fibers play a crucial role in load-bearing and reinforcement in composites, the lack of continuous fiber connections leads to significant differences in the mechanical properties of the repaired area compared to the substrate, making stress concentration more likely under load and reducing the reliability and service life of the repaired composite. These issues make it difficult for existing technologies to achieve a continuous fiber connection between the repaired area and the substrate, limiting material reusability and service life.

[0005] In summary, the existing repair techniques for continuous fiber reinforced ceramic matrix composites have the following technical problems:

[0006] 1. Existing technologies cannot effectively repair overall defects in the thickness direction, resulting in limited repair scenarios;

[0007] 2. The existing repair materials lack continuous fiber connections with the substrate, affecting the mechanical properties and reliability of the repaired area. Summary of the Invention

[0008] The purpose of this invention is to provide a method and application for repairing SiC / SiC composite materials by stitching. By designing a matching stitching interface, using a repair body and sutures made of the same material as the original material for fixation, and combining it with a densification and reinforcement process, it is possible not only to repair overall defects in the thickness direction of SiC / SiC composite materials, but also to ensure a continuous fiber connection between the repaired part and the original material. This expands the application range of SiC / SiC composite material repair and significantly improves the mechanical properties of the repaired composite material, enhancing its reliability and service life, and meeting the needs of related fields for repairing high-performance ceramic matrix composite materials.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for stitching and repairing SiC / SiC composite materials, used for stitching and repairing SiC / SiC composite materials with overall defects in the thickness direction, comprising the following steps:

[0011] S10. Remove the damaged portion of the SiC / SiC composite material to obtain a SiC / SiC composite material body with repairable space;

[0012] S11. Based on the original structural strength design parameters of the damaged part of the SiC / SiC composite material, the load type under actual service conditions, and the mechanical performance requirements after repair, design the geometric shape and size parameters of the body stitching interface. The body stitching interface consists of body stitch holes and body stitch grooves.

[0013] S12. Fabricate a repair body. The material of the repair body is the same as that of the SiC / SiC composite material. The outline and shape of the repair body match the space to be repaired. The geometric shape and dimensional parameters of the repair body's suture interface are the same as those of the body's suture interface.

[0014] S13. To manufacture sutures, wherein the sutures are SiC fiber sutures with a surface coating;

[0015] S14. Place the repair material in the space to be repaired, and align the suture interface of the repair material with the suture interface of the body.

[0016] S15. Fix one end of the suture in one of the main body suture holes, and then guide it into the main body suture groove, repair suture groove, repair suture hole and main body suture hole according to the preset suture path to complete the suturing and fixing.

[0017] As one possible approach, after suture fixation is completed, the SiC / SiC composite suture repair method also includes: brushing liquid organic SiC ceramic precursor onto the suture line and drying and curing it.

[0018] As one possible approach, after drying and curing, the SiC / SiC composite material stitching repair method also includes:

[0019] Densification and reinforcement specifically include:

[0020] After suturing, fixing, drying and curing, the SiC / SiC composite material body is placed in a chemical vapor deposition furnace and heated to the inorganic transformation temperature of the organic SiC ceramic precursor to transform it into SiC ceramic. This process fills the pores inside the suture, between the suture and the suture hole in the body and the suture hole in the repair body, and between the suture groove in the body and the suture groove in the repair body.

[0021] The furnace temperature was then adjusted to the chemical vapor deposition process temperature to perform SiC chemical vapor deposition, and the stitched structure was deposited as a whole to achieve densification and reinforcement.

[0022] Surface treatment specifically includes removing excess material to ensure that the surface condition and dimensions meet design requirements.

[0023] As one possible implementation, when the load type of the damaged part is tensile load, the orientation of the main body suture groove and the repair suture groove is along the tensile load direction; when the load type of the damaged part is compressive load, the normal of the suture interface is along the compressive load direction; when the load type of the damaged part is shear load, an overlapping structure is provided.

[0024] As one possible implementation, the density of the suture interface increases with increasing load, the spacing of the suture interface decreases with increasing load, and the number of suture strands increases with increasing load; wherein, the suture interface includes the body suture interface and the repair suture interface.

[0025] As one possible implementation, the diameters of the main body suture hole and the repair suture hole are equal, denoted as D; the vertical distances from the center to the edge of the main body suture hole and the repair suture hole are equal, denoted as L, where L≥3D; the spacing between adjacent suture holes is H, where H≥2.5D; and the suture holes include both the main body suture hole and the repair suture hole.

[0026] As one possible implementation, the width and depth of the suture groove are equal, and both are equal to the diameter of the suture hole. The suture groove includes a body suture groove and a repair body suture groove. The diameter of the suture hole is 0.02 mm to 2 mm larger than the diameter of the suture.

[0027] Secondly, this invention provides a method for repairing SiC / SiC composite materials by stitching. The SiC / SiC composite material has a rectangular structure, and one edge of the rectangular structure is damaged. The repair method includes the following steps:

[0028] S20. Remove the damaged portion of the SiC / SiC composite material to obtain a SiC / SiC composite material body with a repairable space, wherein the repairable space is an open rectangle;

[0029] S21. Analyze the stress characteristics of the damaged part. Specifically, the stress characteristics are that it is subjected to in-plane tensile loads in two directions parallel to the two adjacent sides of the open rectangle. Based on this, determine the body stitching interface. Specifically, the body stitching interfaces are set at equal intervals in the direction of extension of the side wall and bottom wall of the open rectangle toward the solid part. Each body stitching interface includes a through body stitching groove and a body stitching hole in sequence in the direction of extension toward the solid part.

[0030] S22. Process SiC / SiC composite material repair body. The outline and shape of the repair body match the space to be repaired. The number, geometry, and size parameters of the repair body's stitching interfaces are the same as those of the body's stitching interfaces.

[0031] S23. Processing the suture, specifically: dividing the continuous SiC fiber bundle into segments according to a preset length and a preset number of strands; placing the segments in a chemical vapor deposition furnace to prepare a boron nitride coating on the surface of the SiC fiber bundle; twisting the preset number of SiC fiber bundles with a preset number of nylon fiber bundles together to complete the preparation of the suture;

[0032] S24. Place the repair body in the space to be repaired, ensuring that the suture interfaces of both are matched and aligned, and secure them with a suture fixture; introduce the sutures sequentially into the paired suture holes of the body and the repair body according to the design requirements, while arranging the sutures in the suture grooves of the body and the repair body to avoid protruding from the surface; brush liquid polycarbosilane onto the sutures until they are completely wetted, and dry them in an oven;

[0033] S25. Densification and reinforcement: The stitched SiC / SiC composite material, together with the stitching device, is placed in a chemical vapor deposition furnace. The temperature is first raised to a first preset temperature and held for a first preset time to convert polycarbosilane into SiC ceramic, which fills the pores inside the suture, between the suture and the suture hole, and between the suture and the suture groove. Then the furnace temperature is adjusted to a second preset temperature, and SiC chemical vapor deposition is performed to deposit the stitched structure as a whole for a second preset time to achieve densification and reinforcement.

[0034] S26. Surface treatment, specifically including the removal of excess material to ensure that the surface condition and dimensions meet design requirements.

[0035] Thirdly, this invention provides an application of a stitching repair method for SiC / SiC composite materials. The rectangular SiC / SiC composite material has a rectangular structure, and the rectangular structure has a fracture defect along the width direction at the central position. The repair method includes the following steps:

[0036] S30. Remove the damaged portion of the SiC / SiC composite material to obtain a SiC / SiC composite material body with repairable space;

[0037] S31. Analyze the stress characteristics of the damaged part. The stress characteristics are in-plane tensile load along the length direction. Based on this, determine the body stitching interface. Specifically, extend the stitching edge along the length direction to thin out the overlapping area. The body stitching interface is opened on the SiC / SiC composite body of the overlapping area and adjacent overlapping area. The body stitching interface extends along the length direction and is evenly distributed along the width direction. The body stitching interface includes body stitching holes and body stitching grooves. At least two body stitching holes with coplanar central axes are opened on the same stitching interface. At least one body stitching hole penetrates the SiC / SiC composite body, and the other body stitching holes penetrate the overlapping area.

[0038] S32. Process the repair body, the structure of which has the same outline, shape, overlapping area and repair seam interface as the SiC / SiC composite material body to be repaired;

[0039] S33. Processing the suture, specifically: dividing the continuous SiC fiber bundle into segments according to a preset length and a preset number of strands; placing the segments in a chemical vapor deposition furnace to prepare a boron nitride coating on the surface of the SiC fiber bundle; twisting the preset number of SiC fiber bundles with a preset number of nylon fiber bundles together to complete the preparation of the suture;

[0040] S34. Align the repair body with the seam interface of the SiC / SiC composite material to be repaired and fix it with the seam fitting; introduce the suture into the paired body suture hole and repair body suture hole in sequence according to the design requirements, while arranging the suture in the body suture groove and repair body suture groove to avoid protruding from the surface; brush liquid polycarbosilane onto the suture until the suture is completely wetted, and dry it in an oven.

[0041] S35. Densification and reinforcement: The stitched SiC / SiC composite material, together with the stitching device, is placed in a chemical vapor deposition furnace. The temperature is first raised to the third preset temperature and held for the third preset time to convert polycarbosilane into SiC ceramic, which fills the pores inside the suture, between the suture and the suture hole, and between the suture and the suture groove. Then the furnace temperature is adjusted to the fourth preset temperature, and SiC chemical vapor deposition is performed to deposit the entire stitched structure for the fourth preset time to achieve densification and reinforcement.

[0042] S36. Surface treatment, specifically including the removal of excess material to ensure that the surface condition and dimensions meet design requirements.

[0043] Fourthly, this invention provides an application of a SiC / SiC composite material stitching repair method, which is used for repairing SiC / SiC composite material parts with overall thickness defects in the aerospace and nuclear energy fields.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] 1. This invention proposes a method for suture repair of SiC / SiC composite materials. Through the design and processing of suture interfaces, processing of repair materials, preparation of sutures, suture fixation, densification reinforcement, and control of surface finishing processes, effective repair of SiC / SiC composite materials can be achieved. Compared with existing repair technologies, this method can repair SiC / SiC composite materials with overall defects in the thickness direction, and can significantly expand the applicable scope of SiC / SiC composite material repair.

[0046] 2. The SiC / SiC composite material stitching repair method provided by the present invention makes full use of the reinforcing and toughening characteristics of continuous fibers, so that there is a continuous fiber connection between the repair part and the main body, which significantly improves the mechanical properties of the repaired composite material and is suitable for complex working environments such as high temperature and high stress, effectively enhancing its reliability and service life. Attached Figure Description

[0047] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0048] Figure 1 This is a flowchart illustrating the implementation of a SiC / SiC composite material stitching and repair method according to the present invention.

[0049] Figure 2 This is a schematic diagram of the damaged SiC / SiC composite material provided in Embodiment 1 of the present invention;

[0050] Figure 3 This is a schematic diagram of the SiC / SiC composite material body to be repaired after the damaged part has been removed, as provided in Embodiment 1 of the present invention;

[0051] Figure 4 This is a schematic diagram of the SiC / SiC composite material body stitching interface design provided in Embodiment 1 of the present invention;

[0052] Figure 5 This is a schematic diagram of the repair material stitching interface design provided in Embodiment 1 of the present invention;

[0053] Figure 6 This is a schematic diagram of the matching and alignment of the SiC / SiC composite material body and the repair material provided in Embodiment 1 of the present invention;

[0054] Figure 7 This is a schematic diagram of the damaged SiC / SiC composite material provided in Embodiment 2 of the present invention;

[0055] Figure 8 This is a schematic diagram of the SiC / SiC composite material body to be repaired after the damaged part has been removed, as provided in Embodiment 2 of the present invention;

[0056] Figure 9 This is a schematic diagram of the SiC / SiC composite material body stitching interface design provided in Embodiment 2 of the present invention;

[0057] Figure 10 This is a schematic diagram of the repair material stitching interface design provided in Embodiment 2 of the present invention;

[0058] Figure 11 This is a schematic diagram of the matching and alignment of the SiC / SiC composite material body and the repair material provided in Embodiment 2 of the present invention.

[0059] Figure label:

[0060] 1-Damaged part, 2-SiC / SiC composite material body to be repaired, 3-Suture hole of body, 4-Suture groove of body, 5-Repair body, 6-Suture hole of repair body, 7-Suture groove of repair body;

[0061] 8-Damaged part, 9-SiC / SiC composite material body to be repaired, 10-Suture hole of body, 11-Suture groove of body, 12-Repair body, 13-Suture hole of repair body, 14-Suture groove of repair body. Detailed Implementation

[0062] To facilitate a clear description of the technical solutions in the embodiments of the present invention, the terms "first" and "second" are used to distinguish identical or similar items with essentially the same function and effect. For example, the first threshold and the second threshold are merely used to distinguish different thresholds and do not limit their order. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and that the terms "first" and "second" are not necessarily different.

[0063] It should be noted that in this invention, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0064] In this invention, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one" or similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, "at least one of a, b, or c" can represent: a, b, c, a combination of a and b, a combination of a and c, a combination of b and c, or a, b, and c, where a, b, and c can be single or multiple.

[0065] This invention aims to provide a method and application for repairing SiC / SiC composite materials by stitching. By designing a matching stitching interface, using a repair body and sutures made of the same material as the original material for fixation, and combining it with a densification reinforcement process, it is possible not only to repair overall defects in the thickness direction of SiC / SiC composite materials, but also to ensure a continuous fiber connection between the repaired part and the original material. This expands the application range of SiC / SiC composite material repair and significantly improves the mechanical properties of the repaired composite material, enhancing its reliability and service life, thus meeting the needs of related fields for repairing high-performance ceramic matrix composite materials.

[0066] In a first aspect, the present invention provides a method for stitching and repairing SiC / SiC composite materials, used for stitching and repairing SiC / SiC composite materials with overall defects in the thickness direction, comprising the following steps:

[0067] S10. Remove the damaged portion of the SiC / SiC composite material to obtain a SiC / SiC composite material body with repairable space;

[0068] S11. Based on the original structural strength design parameters of the damaged part of the SiC / SiC composite material, the load type under actual service conditions, and the mechanical performance requirements after repair, design the geometric shape and size parameters of the body stitching interface. The body stitching interface consists of body stitch holes and body stitch grooves.

[0069] S12. Fabricate a repair body. The material of the repair body is the same as that of the SiC / SiC composite material. The outline and shape of the repair body match the space to be repaired. The geometric shape and dimensional parameters of the repair body's suture interface are the same as those of the body's suture interface.

[0070] S13. To manufacture sutures, wherein the sutures are SiC fiber sutures with a surface coating;

[0071] S14. Place the repair material in the space to be repaired, and align the suture interface of the repair material with the suture interface of the body.

[0072] S15. Fix one end of the suture in one of the main body suture holes, and then guide it into the main body suture groove, repair suture groove, repair suture hole and main body suture hole according to the preset suture path to complete the suturing and fixing.

[0073] Among them, the body suture interface refers to the connection structure designed according to the original structural strength, actual load and performance requirements. It consists of suture holes and suture grooves and is used to ensure the mechanical transmission between the repair and the body.

[0074] The repair body is made of the same material as the main body, and its outline and shape match the defect space to ensure interface compatibility.

[0075] Among them, the SiC fiber stitches with surface coating can improve the interfacial bonding strength and prevent high-temperature oxidation damage;

[0076] The preset stitching path ensures that the stitches are reasonably distributed within the slots, forming a continuous fiber network.

[0077] Specifically, after the damaged area is precisely removed, a space to be repaired is formed, and the geometric parameters of the suture interface are designed according to mechanical requirements. After the repair body is aligned with the interface of the main body, the suture passes through the hole and groove system according to the preset path to establish the fiber connection of the bridging repair area. During the suturing process, the suture tension control and path optimization can avoid local stress concentration and achieve uniform load transfer.

[0078] Compared with existing technologies, which are limited to surface repair and lack fiber continuity, this solution achieves overall repair in the thickness direction through a three-dimensional stitching structure. The stitching interface and the suture form a biomimetic connection network, effectively restoring the mechanical properties of the material. The introduction of continuous fibers enables the repaired part to form an integral load-bearing structure with the body, avoiding the risk of interface delamination.

[0079] Through the above technical solution, this application can reliably repair structures with thickness defects, forming a continuous fiber-reinforced interface between the repaired part and the main body, significantly improving tensile, shear and impact resistance, and is suitable for complex working environments such as high temperature and high stress, thus extending the service life of components.

[0080] As one possible approach, after suture fixation is completed, the SiC / SiC composite suture repair method also includes: brushing liquid organic SiC ceramic precursor onto the suture line and drying and curing it.

[0081] As one possible approach, after drying and curing, the SiC / SiC composite material stitching repair method also includes:

[0082] Densification and reinforcement specifically include:

[0083] After suturing, fixing, drying and curing, the SiC / SiC composite material body is placed in a chemical vapor deposition furnace and heated to the inorganic transformation temperature of the organic SiC ceramic precursor to transform it into SiC ceramic. This process fills the pores inside the suture, between the suture and the suture hole in the body and the suture hole in the repair body, and between the suture groove in the body and the suture groove in the repair body.

[0084] The furnace temperature was then adjusted to the chemical vapor deposition process temperature to perform SiC chemical vapor deposition, and the stitched structure was deposited as a whole to achieve densification and reinforcement.

[0085] Surface treatment specifically includes removing excess material to ensure that the surface condition and dimensions meet design requirements.

[0086] The inorganic transformation temperature refers to the critical temperature at which an organic precursor decomposes and transforms into an inorganic ceramic phase. As an example, the decomposition initiation temperature of the organic precursor can be determined by measuring the thermal decomposition curve of the organic precursor material using a thermogravimetric analyzer. This initiation temperature is the critical temperature at which the organic precursor transforms into the SiC ceramic phase. The inorganic transformation temperature range must be higher than this critical temperature and lower than the thermal damage threshold of the matrix material.

[0087] The chemical vapor deposition process temperature refers to the gas phase reaction activation temperature required for depositing SiC ceramics. As an example, the furnace temperature is first adjusted to the chemical vapor deposition temperature of SiC material, and then the deposition rate is controlled by adjusting the ratio of silicon source and carbon source gas to achieve sufficient density.

[0088] Pore ​​filling refers to the process of sealing the internal voids of a stitched structure with SiC ceramics formed by precursor conversion. As an example, a staged heating strategy can be used to achieve pore gradient filling.

[0089] Integral deposition refers to the formation of a continuous and dense SiC ceramic layer in the seam area through chemical vapor deposition. As an example, three-dimensional uniform deposition can be achieved through multi-directional rotating tooling.

[0090] Specifically, after suture fixation and surface coating are completed, structural reinforcement is achieved through two-step heat treatment: First, the precursor is ceramized at a specific temperature, and the resulting nanoscale SiC particles can penetrate into the gaps between fiber bundles and interfacial gaps to form a primary bonding network; then, chemical vapor deposition is performed at a higher temperature, and the SiC crystals generated by the vapor reaction are epitaxially grown on the basis of the primary network to form a continuous ceramic phase that runs through the suture area; this process achieves a synergistic improvement in interfacial bonding strength and overall toughness through microstructure control, while the surface treatment process eliminates surface protrusions generated during the deposition process through mechanical processing to ensure a smooth transition between the repair area and the substrate.

[0091] Compared to existing technologies, traditional repair methods, which rely on a single temperature treatment, result in incomplete precursor transformation and residual porosity, leading to numerous defects at the suture joint and making it prone to stress concentration. This invention, through staged temperature control, achieves a complementary effect between precursor transformation and chemical deposition, ensuring both pore filling and interface strengthening.

[0092] In existing technologies, surface treatment often involves simple grinding. This solution, by combining dimensional detection and selective removal, can precisely control the geometric accuracy of the repair area.

[0093] Through the above technical solution, this application effectively solves the technical problems of insufficient bonding strength at the suture interface and easy expansion of porosity defects in traditional repair methods. The synergistic effect of precursor transformation and chemical deposition enables the formation of a gradient transition ceramic structure in the suture area, significantly improving the interface load transfer efficiency; precise surface treatment ensures the geometric matching between the repair area and the substrate, avoiding secondary stress concentration caused by dimensional deviations.

[0094] As one possible implementation, when the load type of the damaged part is tensile load, the orientation of the main body suture groove and the repair suture groove is along the tensile load direction; when the load type of the damaged part is compressive load, the normal of the suture interface is along the compressive load direction; when the load type of the damaged part is shear load, an overlapping structure is provided.

[0095] The orientation of the suture groove in the main body and the suture groove in the repair body along the tensile load direction means that the extension direction of the suture groove is parallel to the direction of the tensile load. As an example, this can be achieved by forming a straight groove consistent with the tensile direction through laser cutting or mechanical processing. This arrangement allows the suture to bear the load along the fiber axis under the action of tensile load, giving full play to the high strength characteristics of SiC fiber.

[0096] The normal direction of the suture interface along the compressive load direction means that the joint surface between the repair and the body is perpendicular to the direction of the compressive load. As an example, this can be achieved by adjusting the assembly angle of the repair so that the normal of the joint surface coincides with the pressure direction. This design allows the suture interface to bear uniform normal stress under compressive load, avoiding shear failure.

[0097] Among them, the overlapping structure refers to the formation of a stepped or overlapping contact surface in the repair area. As an example, it can be achieved by processing a stepped overlapping surface at the edge of the damaged area; this structure improves shear resistance by increasing the contact area and mechanical interlocking effect.

[0098] Specifically, under tensile load conditions, the seam grooves are arranged along the load direction so that the seam fibers are under axial tension, and the fiber strength utilization rate is optimized.

[0099] Under compression conditions, the normal direction of the suture interface is consistent with the load direction, so that a stable pressure transmission path is formed between the repair and the body.

[0100] For shear loads, lap joints effectively disperse shear stress by increasing the frictional resistance of the contact surfaces and the mechanical interlocking effect.

[0101] By designing corresponding stitching structures for different load types, the repair area can form a load-bearing mode that matches the original material, thus avoiding stress concentration or interface delamination caused by load type mismatch.

[0102] Compared to existing technologies, traditional repair methods do not consider the impact of different load types on the suture structure, and the use of a single suture method makes the repaired area prone to interface cracking or fiber breakage under complex loads. This invention, through load type identification and targeted structural design, ensures that the suture fiber arrangement direction is consistent with the principal stress direction, and that the load-bearing mode of the suture interface is adapted to the load type, significantly improving the load-bearing efficiency and service stability of the repair structure.

[0103] Through the above technical solution, this invention can optimize the stitching structure parameters according to the actual load type, so that the mechanical properties of the repaired area are effectively matched with the base material. Under different load conditions such as tension, compression, and shear, the repaired area can achieve continuous fiber stress transfer, avoiding local stress concentration caused by structural mismatch, thereby improving the overall strength and fatigue resistance of the repaired component.

[0104] As one possible implementation, the density of the suture interface increases with increasing load, the spacing of the suture interface decreases with increasing load, and the number of suture strands increases with increasing load; wherein, the suture interface includes the body suture interface and the repair suture interface.

[0105] The density of suture joints refers to the number of suture joints per unit area. As an example, it can be achieved by increasing the number of suture holes and suture grooves. Its function is to disperse the load transfer path by increasing the distribution density of suture points and avoid local stress concentration.

[0106] The spacing between suture interfaces refers to the distance between adjacent suture interfaces. As an example, this can be achieved by reducing the spacing between suture holes. Its function is to improve the overall load-bearing capacity of the connection structure by shortening the length of the load transmission path.

[0107] The number of strands in a suture refers to the number of fiber bundles contained in a single suture. As an example, this can be achieved by increasing the number of twists in the fiber bundles. Its function is to enhance the tensile strength of a single suture to meet the mechanical requirements under high load conditions.

[0108] Specifically, as the load on the repair area increases, the density of the suture joints is configured to increase synchronously. For example, in repair areas subjected to high tensile loads, the number of suture holes and suture grooves can be set to 1.5 times the baseline density. The spacing between adjacent suture joints is configured to decrease synchronously. For example, in repair areas subjected to high shear loads, the suture hole spacing can be adjusted to 60% of the baseline spacing. The number of suture strands is configured to increase synchronously. For example, in repair areas subjected to high compressive loads, the number of suture fiber bundles can be set to twice the baseline number of strands. Through the coordinated adjustment of these three factors, the load transfer path of the repair area is optimized into a multi-level distributed structure, and the interfacial bonding strength between the sutures and the body and repair is dynamically adapted to the actual load level.

[0109] Compared to existing technologies, current repair methods typically use fixed values ​​for the density, spacing, and suture parameters of the suture joints, making dynamic optimization impossible based on load variations. This leads to stress concentration or insufficient connection strength in high-load areas. This solution establishes a correlation mechanism between suture parameters and load strength, creating a positive match between the load-bearing capacity of the suture structure and the mechanical requirements of the repair area, thereby eliminating localized weak points.

[0110] Through the above technical solution, this application solves the problems of uneven stress distribution and insufficient connection strength caused by fixed suture parameters in traditional repair methods. It enables the suture structure in high-load areas to achieve uniform load transfer through adaptive parameter adjustment, avoids debonding or breakage failure of the repair interface due to local overload, and ensures the consistency of mechanical properties between the repaired part and the body material.

[0111] As one possible implementation, the diameters of the main body suture hole and the repair suture hole are equal, denoted as D; the vertical distances from the center to the edge of the main body suture hole and the repair suture hole are equal, denoted as L, where L≥3D; the spacing between adjacent suture holes is H, where H≥2.5D; and the suture holes include both the main body suture hole and the repair suture hole.

[0112] Here, D refers to the diameter of the suture hole. As an example, it can be achieved by mechanical drilling or laser processing. Its size is determined according to the suture diameter and material strength, for example, it can be 0.5mm to 5mm. This parameter is used to ensure that the suture has enough room to move in the hole and that the connection strength will not decrease due to excessive gaps.

[0113] Where L refers to the minimum distance from the center of the suture hole to the edge of the material. As an example, it can be determined by stress simulation using 3D modeling software. For example, it can be 1.5mm to 15mm. This parameter is used to prevent edge breakage of the suture site under stress.

[0114] Here, H refers to the distance between the centers of adjacent suture holes. As an example, it can be achieved by an equidistant array arrangement, for example, it can be 1.25mm to 12.5mm. This parameter is used to control the suture density to match the strength requirements under different load conditions.

[0115] Specifically, by setting the diameter of the suture holes in the body and the repair to the same size, uniform contact pressure is ensured when the suture passes through the hole. The distance from the center to the edge of the suture hole is set to be more than three times the hole diameter, ensuring sufficient tear resistance in the material edge area under tensile or shear loads. The spacing between adjacent suture holes is limited to more than 2.5 times the hole diameter, ensuring that the distribution density of suture points meets mechanical performance requirements while avoiding material structure weakening due to excessively small hole spacing. For example, in implementation, a five-axis machining center can be used to simultaneously machine 1mm diameter suture holes on both the repair and the body, with the hole center distance from the edge maintained at more than 6mm and the spacing between adjacent holes controlled at more than 5mm.

[0116] Compared to existing technologies, current repair methods typically lack a systematic design for the positional parameters of suture holes, which can easily lead to stress concentration at the edges of the repaired area or insufficient suture density. This solution, however, establishes a mechanically based design criterion for suture parameters by defining the quantitative relationship between suture hole diameter, edge distance, and hole spacing. For example, when the material is subjected to high tensile loads, a combination of smaller hole diameter and larger hole spacing can be used to optimize weight distribution while ensuring connection strength.

[0117] Through the above technical solution, this application can effectively balance the load-bearing capacity and material integrity of the repaired area, prevent local stress concentration caused by improper suture hole placement, and ensure that the suture structure and the base material form a continuous and stable mechanical transmission path. This design principle allows for flexible adjustment of suture parameters for different working conditions. For example, in high-temperature and high-pressure environments, the hole diameter can be appropriately increased to compensate for differences in thermal expansion, thereby significantly improving the reliability and service life of the repair structure.

[0118] As one possible implementation, the width and depth of the suture groove are equal, and both are equal to the diameter of the suture hole. The suture groove includes a body suture groove and a repair body suture groove. The diameter of the suture hole is 0.02 mm to 2 mm larger than the diameter of the suture.

[0119] The equal width and depth of the suture groove refers to a square cross-section. As an example, this can be formed by machining or laser etching. This design allows the suture to be evenly stressed in the groove and maximizes the contact area with the substrate.

[0120] The difference between the suture hole diameter and the suture diameter refers to the gap between the inner diameter of the hole and the outer diameter of the suture being controlled within the range of 0.02mm to 2mm. As an example, this can be achieved through precision drilling. This gap design ensures that the suture can be smoothly threaded through while reserving filling space for subsequent densification processing.

[0121] Specifically, during the docking process between the repair and the substrate, the uniformly sized suture grooves and suture holes form a continuous channel, enabling the sutures to form a three-dimensional network structure at the interface. When the suture diameter is slightly smaller than the channel diameter, frictional damage during threading is avoided, while ensuring that the precursor can fully penetrate into the gaps during chemical vapor deposition. In the densification stage, the SiC ceramic formed by the precursor transformation can completely fill the voids between the sutures and the hole walls, ultimately forming a continuous reinforced structure without interface defects.

[0122] Compared to existing technologies, traditional repair methods lack a systematic approach to suture channel size design, often resulting in insufficient bonding strength due to excessively large gaps between the suture and the hole wall, or difficulties in threading due to excessively small gaps. This solution, by defining the geometric relationship between the suture groove and the suture hole, ensures both construction feasibility and interface strengthening through the provision of reasonable gaps, overcoming the stress concentration problem caused by discontinuous fiber connections in existing technologies.

[0123] Through the above technical solution, this application effectively improves the load transfer efficiency of the suture interface, enabling the repaired area to achieve uniform stress distribution through a continuous fiber network when subjected to complex loads. The optimized gap design between the suture and the substrate significantly improves the interfacial bonding strength, avoids the risk of secondary cracking caused by local stress concentration, and ensures that the repaired area has mechanical properties comparable to the original substrate.

[0124] Secondly, this invention provides a method for repairing SiC / SiC composite materials by stitching. The SiC / SiC composite material has a rectangular structure, and one edge of the rectangular structure is damaged. The repair method includes the following steps:

[0125] S20. Remove the damaged portion of the SiC / SiC composite material to obtain a SiC / SiC composite material body with a repairable space, wherein the repairable space is an open rectangle;

[0126] S21. Analyze the stress characteristics of the damaged part. Specifically, the stress characteristics are that it is subjected to in-plane tensile loads in two directions parallel to the two adjacent sides of the open rectangle. Based on this, determine the body stitching interface. Specifically, the body stitching interfaces are set at equal intervals in the direction of extension of the side wall and bottom wall of the open rectangle toward the solid part. Each body stitching interface includes a through body stitching groove and a body stitching hole in sequence in the direction of extension toward the solid part.

[0127] S22. Process SiC / SiC composite material repair body. The outline and shape of the repair body match the space to be repaired. The number, geometry, and size parameters of the repair body's stitching interfaces are the same as those of the body's stitching interfaces.

[0128] S23. Processing the suture, specifically: dividing the continuous SiC fiber bundle into segments according to a preset length and a preset number of strands; placing the segments in a chemical vapor deposition furnace to prepare a boron nitride coating on the surface of the SiC fiber bundle; twisting the preset number of SiC fiber bundles with a preset number of nylon fiber bundles together to complete the preparation of the suture;

[0129] S24. Place the repair body in the space to be repaired, ensuring that the suture interfaces of both are matched and aligned, and secure them with a suture fixture; introduce the sutures sequentially into the paired suture holes of the body and the repair body according to the design requirements, while arranging the sutures in the suture grooves of the body and the repair body to avoid protruding from the surface; brush liquid polycarbosilane onto the sutures until they are completely wetted, and dry them in an oven;

[0130] S25. Densification and reinforcement: The stitched SiC / SiC composite material, together with the stitching device, is placed in a chemical vapor deposition furnace. The temperature is first raised to a first preset temperature and held for a first preset time to convert polycarbosilane into SiC ceramic, which fills the pores inside the suture, between the suture and the suture hole, and between the suture and the suture groove. Then the furnace temperature is adjusted to a second preset temperature, and SiC chemical vapor deposition is performed to deposit the stitched structure as a whole for a second preset time to achieve densification and reinforcement.

[0131] S26. Surface treatment, specifically including the removal of excess material to ensure that the surface condition and dimensions meet design requirements.

[0132] Among them, the body stitching interface refers to the hole and groove structure that is evenly distributed along the width direction and extends along the length direction. Specifically, it can be formed by combining laser drilling and milling. This structure can achieve continuous distribution of the stitches in the tensile load direction.

[0133] Among them, the body suture hole with coplanar central axis refers to the central axis of multiple holes located in the same plane. Specifically, it can be achieved by using a three-dimensional positioning fixture in conjunction with the drilling process. This design can ensure that the suture is subjected to uniform force under tensile load.

[0134] Among them, boron nitride coating refers to a ceramic coating covering the surface of SiC fiber bundles. Specifically, it can be prepared by chemical vapor deposition process. This coating can improve the oxidation resistance of the suture and reduce inter-fiber friction damage.

[0135] Among them, nylon fiber bundle twisting refers to twisting a preset number of nylon fibers and SiC fiber bundles together to form a composite yarn. Specifically, it can be achieved by using a ring twisting machine. This structure can improve the flexibility of the thread and enhance the interfacial bonding force.

[0136] Specifically, when a rectangular SiC / SiC composite material is damaged with a notch on one edge, the damaged area is first removed by machining to create a repair space. Based on the characteristic that the damaged area is simultaneously subjected to in-plane tensile loads, body stitching interfaces are machined at equal intervals along the edge of the repair area, specifically extending from the sidewalls and bottom walls of the open rectangle towards the solid portion. The repair body is machined to a geometry that perfectly matches the damaged area, and its stitching interfaces maintain the same distribution parameters as the body. A suture formed by twisting SiC and nylon fibers is inserted into a pre-defined path through matching slots for mechanical locking. Impregnation with liquid polycarbosilane and subsequent high-temperature conversion processes create a ceramic phase bond between the suture and the matrix. Finally, a continuous and dense SiC ceramic layer is formed in the stitched area using chemical vapor deposition, achieving a match between the mechanical properties of the repair structure and the body material.

[0137] Compared to existing technologies, traditional repair methods can only treat surface damage and rely on adhesives for bonding, failing to create a continuous fiber-reinforced structure in the thickness direction. This method, by designing a through-hole suture interface in the damaged area, forms a three-dimensional continuous fiber-reinforced network between the repair and the substrate, effectively transferring tensile loads and suppressing interfacial delamination. The composite twisted suture enhances flexibility while maintaining high-temperature performance, solving the problem of brittle fracture in pure ceramic fibers. The staged densification process achieves integrated pore filling and structural reinforcement, overcoming the drawbacks of traditional single-deposition processes that easily generate internal defects.

[0138] Through the above technical solution, this invention can achieve full-thickness repair of SiC / SiC composite materials with edge defects on one side, maintaining the continuity of load transfer between the repaired area and the substrate under tensile loads. The through-hole suture interface design significantly reduces the risk of stress concentration, and the composite twisted suture maintains stable interfacial bonding strength at high temperatures. The staged densification process ensures that the internal pores of the suture structure are fully filled, making the tensile properties of the repaired area consistent with those of the undamaged area.

[0139] Thirdly, this invention provides an application of a stitching repair method for SiC / SiC composite materials. The rectangular SiC / SiC composite material has a rectangular structure, and the rectangular structure has a fracture defect along the width direction at the central position. The repair method includes the following steps:

[0140] S30. Remove the damaged portion of the SiC / SiC composite material to obtain a SiC / SiC composite material body with repairable space;

[0141] S31. Analyze the stress characteristics of the damaged part. The stress characteristics are in-plane tensile load along the length direction. Based on this, determine the body stitching interface. Specifically, extend the stitching edge along the length direction to thin out the overlapping area. The body stitching interface is opened on the SiC / SiC composite body of the overlapping area and adjacent overlapping area. The body stitching interface extends along the length direction and is evenly distributed along the width direction. The body stitching interface includes body stitching holes and body stitching grooves. At least two body stitching holes with coplanar central axes are opened on the same stitching interface. At least one body stitching hole penetrates the SiC / SiC composite body, and the other body stitching holes penetrate the overlapping area.

[0142] S32. Process the repair body, the structure of which has the same outline, shape, overlapping area and repair seam interface as the SiC / SiC composite material body to be repaired;

[0143] S33. Processing the suture, specifically: dividing the continuous SiC fiber bundle into segments according to a preset length and a preset number of strands; placing the segments in a chemical vapor deposition furnace to prepare a boron nitride coating on the surface of the SiC fiber bundle; twisting the preset number of SiC fiber bundles with a preset number of nylon fiber bundles together to complete the preparation of the suture;

[0144] S34. Align the repair body with the seam interface of the SiC / SiC composite material to be repaired and fix it with the seam fitting; introduce the suture into the paired body suture hole and repair body suture hole in sequence according to the design requirements, while arranging the suture in the body suture groove and repair body suture groove to avoid protruding from the surface; brush liquid polycarbosilane onto the suture until the suture is completely wetted, and dry it in an oven.

[0145] S35. Densification and reinforcement: The stitched SiC / SiC composite material, together with the stitching device, is placed in a chemical vapor deposition furnace. The temperature is first raised to the third preset temperature and held for the third preset time to convert polycarbosilane into SiC ceramic, which fills the pores inside the suture, between the suture and the suture hole, and between the suture and the suture groove. Then the furnace temperature is adjusted to the fourth preset temperature, and SiC chemical vapor deposition is performed to deposit the entire stitched structure for the fourth preset time to achieve densification and reinforcement.

[0146] S36. Surface treatment, specifically including the removal of excess material to ensure that the surface condition and dimensions meet design requirements.

[0147] The overlapping area refers to the structural extension formed through thinning processing, used to increase the contact area between the repair and the substrate. This can be achieved through mechanical milling or laser cutting, and this design can disperse stress concentration under tensile loads. The substrate suture interface refers to a uniformly distributed perforated structure along its length, which can be achieved through CNC drilling and wire cutting. Multi-level connection points are formed by coplanarly arranged through-holes and non-through-holes, enhancing the load-bearing continuity of the suture structure. The boron nitride coating is an insulating layer covering the surface of the SiC fibers, which can be prepared using chemical vapor deposition. This coating prevents interfacial reactions between the fibers and the matrix at high temperatures, maintaining the mechanical properties of the suture. The nylon fiber bundle refers to organic fibers twisted together with the SiC fibers, which can be achieved using a twin-strand twisting machine. During subsequent high-temperature treatment, the nylon fibers decompose to form porous channels, facilitating the penetration and filling of ceramic precursors.

[0148] Specifically, when a rectangular SiC / SiC composite material suffers a central fracture defect, the irregular broken edges are first removed by machining to form a rectangular repair space. Based on the characteristic that the fracture surface mainly bears in-plane tensile loads, a stepped overlap structure is machined on both sides of the repair area, and two rows of suture slots parallel to the load direction are arranged in the transition area between the overlap area and the substrate. The repair body is prefabricated using the same material system as the substrate, and its overlap surface geometry is completely mirror-symmetrical to the substrate. The sutures are made of a blend of SiC fibers with a boron nitride coating and nylon fibers, and are cyclically threaded along the path of "substrate hole - repair slot - repair hole - substrate slot" during suturing, forming a three-dimensional mesh connection structure. After the sutures are impregnated with liquid polycarbosilane and dried to form temporary fixation, they are then processed in stages in a chemical vapor deposition furnace: the first stage involves a medium-temperature conversion to ceramicize the precursor and fill the micropores; the second stage involves high-temperature deposition at the suture interface to generate a continuous SiC ceramic layer, ultimately achieving structural continuity between the repair area and the substrate in terms of both the fiber reinforcement phase and the ceramic matrix.

[0149] In some specific embodiments, the thinning amount of the overlapping area can be 30%-50% of the body thickness, the suture hole diameter can be 0.5-2 mm, and the spacing between adjacent holes can be 2.5-3 times the hole diameter. When twisting the sutures, the ratio of SiC fiber to nylon fiber strands can be 3:1 to 5:1, and the thickness of the boron nitride coating can be 0.1µm-1µm. The first stage temperature of chemical vapor deposition can be 800℃-1000℃, and the second stage temperature can be 1000-1200℃.

[0150] Compared to existing technologies, traditional repair methods only employ surface bonding or localized filling when dealing with through-fractures, failing to reconstruct the continuous load-bearing network of the fiber-reinforced phase. This method, through the design of an overlapping structure and multiple rows of suture grooves, creates a fiber connection channel spanning the entire thickness between the repair and the matrix. Combined with a staged densification process, this reconstructs a three-dimensional composite structure of fiber-matrix-interface at the microscale. Compared to repair methods relying solely on adhesives or deposited layers, this suture-reinforced structure effectively transfers in-plane loads and prevents interlaminar delamination failure at the repair interface.

[0151] Through the above technical solution, this invention can effectively repair through-fracture damage in the width direction of SiC / SiC composite materials and rebuild the continuous fiber-bearing structure of the material in the tensile load direction. The multi-row perforated groove arrangement of the suture interface, combined with the three-dimensional stitching method, significantly improves the interfacial bonding strength between the repair area and the substrate. The staged densification process maintains the mechanical properties of the suture while achieving a seamless transition of the matrix material, making the repaired composite material close to the original material properties in terms of tensile strength, fracture toughness, and high-temperature stability.

[0152] Fourthly, this invention provides an application of a SiC / SiC composite material stitching repair method, which is used for repairing SiC / SiC composite material parts with overall thickness defects in the aerospace and nuclear energy fields.

[0153] Thickness-direction overall defects refer to three-dimensional defects where the damaged area extends through the entire thickness of the composite material component. This can be achieved by machining the damaged portion to create a repairable space with a continuous structure. Repairing this type of defect requires restoring the material's continuous load-bearing structure in the thickness direction. Aerospace, nuclear energy, and aerospace components refer to parts that operate in high-temperature, high-stress, oxidative corrosion, or radiation environments. Examples include hot-end components of gas turbine engines, spacecraft thermal protection systems, and nuclear reactor cladding tubes. These components have stringent requirements for the high-temperature resistance, mechanical integrity, and environmental corrosion resistance of the repaired area.

[0154] Specifically, for SiC / SiC composite components such as combustion chamber liners of aero-engines that have through-thickness damage, a three-dimensional suture connection is achieved by designing a suture interface that matches the structure of the original material and using SiC fiber sutures coated with SiC ceramic precursors. This creates a continuous fiber reinforcement network that extends through the thickness between the repair and the original material. The suture structure is then densified using a chemical vapor deposition process, enabling the repaired area to achieve mechanical properties and operational stability similar to the original material.

[0155] Compared to existing technologies, traditional repair techniques can only address surface scratches or shallow damage and cannot rebuild the fiber reinforcement network in the thickness direction. This method, however, achieves continuous fiber distribution throughout the defect area through a three-dimensional stitching structure, solving the problem of mismatched mechanical properties between the repaired area and the original material in existing technologies. Compared to repair methods that only use bonding or local deposition, the stitched reinforcement structure formed by this method is more suitable for the complex load conditions required in aerospace equipment.

[0156] Through the above technical solution, this application can effectively restore the integrity of the fiber-reinforced structure in the thickness defect area, ensure the load-bearing capacity of the repaired part under extreme environments such as high-temperature gas erosion and high-energy particle radiation, significantly improve the repairability and service reliability of key products such as hot-end components of aero engines and nuclear reactor components, and reduce the economic losses caused by the overall scrapping due to local damage.

[0157] To facilitate understanding of the technical solution of this application, further explanation is provided below with reference to specific embodiments.

[0158] Example 1

[0159] A rectangular SiC / SiC composite material part measuring 1000mm × 1000mm × 5mm has a chipped edge on one side. The following steps are used to repair it.

[0160] (1) Design and processing of the suture interface: The damaged part 1 of the SiC / SiC composite material was removed by subtractive processing to obtain the SiC / SiC composite material body 2 to be repaired. The stress characteristics of the damaged area are that it is subjected to in-plane tensile loads in two directions parallel to the two adjacent sides of the rectangle. The suture interface design drawing was completed, and the main parameters are as follows: the suture spacing is 10 mm, the diameter of the suture hole 3 is 1 mm, the distance between the suture hole and the suture edge is 10 mm, the direction of the suture is perpendicular to the suture edge it crosses, the width of the suture groove 4 is 1 mm, the depth of the suture groove 4 is 1 mm, and the suture specification is 0.5K continuous SiC fiber bundles of 2 strands combined. According to the suture interface design drawing, the suture hole 3 and the suture groove 4 were processed by machining.

[0161] (2) Repair material processing: The repair body 5 is processed using the same SiC / SiC composite material as the SiC / SiC composite material body 2 to be repaired. The repair body 5 has a contour, surface, repair suture hole 6 and repair suture groove 7 that match the SiC / SiC composite material body 2 to be repaired. The repair body 5 and the SiC / SiC composite material body 2 to be repaired can be assembled to obtain the required complete material shape.

[0162] (3) Suture preparation: According to the suture specification design requirements, the 0.5K continuous SiC fiber bundle was divided into 9 strands with a length of 600mm. The SiC fiber bundle was placed in a chemical vapor deposition furnace to prepare a boron nitride coating on the surface of the SiC fiber bundle. The 3 strands of SiC fiber bundle were twisted together with 1 nylon fiber bundle to complete the preparation of 3 sutures.

[0163] (4) Suturing and Fixing: Align the SiC / SiC composite material body 2 and the repair body 5 according to the design requirements and fix them with a suture fixture. Insert the suture into the paired suture holes 3 and 6 of the body and the repair body in sequence according to the design requirements, while arranging the suture in the suture groove 4 of the body and the suture groove 7 of the repair body to avoid protruding from the surface. Apply liquid polycarbosilane to the suture until the suture is completely wetted, and dry it in an oven at 200°C for 5 hours.

[0164] (5) Densification and reinforcement: The stitched SiC / SiC composite material, along with the stitching fixture, is placed in a chemical vapor deposition furnace. The temperature is first raised to 900℃ and held for 2 hours to convert polycarbosilane into SiC ceramic, filling the pores inside the suture, between the suture and the suture hole, and between the suture and the suture groove. The furnace temperature is then adjusted to 1000℃ for SiC chemical vapor deposition, and the stitched structure is deposited as a whole for 20 hours to achieve densification and reinforcement.

[0165] (6) Surface finishing: Remove the sewing fixture from the SiC / SiC composite material, finish the surface of the SiC / SiC composite material, remove excess material, and make the surface condition and size meet the design requirements.

[0166] Example 2

[0167] A rectangular SiC / SiC composite material part measuring 100mm × 10mm × 4.5mm has a fracture along its width at the center. The following steps are used to repair it.

[0168] (1) Design and processing of the suture interface: The damaged part 8 of the SiC / SiC composite material is removed by subtractive processing to obtain the SiC / SiC composite material body 9 to be repaired. The load-bearing design requirement of the damaged area is an in-plane tensile load of 800N along the length direction. The suture interface design drawing is completed, and the main parameters are as follows: a 10mm×10mm overlap area is set along the suture edge. The thickness of the SiC / SiC composite material body 9 to be repaired and the repair body 12 in the overlap area are both 2.25mm. The spacing between adjacent sutures is 2.5mm. The spacing between the body suture holes 10 corresponding to the same suture is 5mm. The body suture hole 10 is 3mm away from the interface edge. The diameter of the body suture hole 10 is 0.7mm. The suture direction is along the length direction. The body suture groove 11 is 0.7mm wide and 0.7mm deep. The suture specification is one strand of continuous SiC fiber bundle of 0.5K. According to the suture interface design drawing, the body suture hole 10 and body suture groove 11 are processed by machining.

[0169] (2) Repair material processing: The repair body 12 is processed using the same SiC / SiC composite material as the SiC / SiC composite material body 9 to be repaired. The repair body 12 has a contour, surface, repair suture hole 13, and repair suture groove 14 that match the SiC / SiC composite material body 9 to be repaired. The repair suture hole 13 of the repair body 12 in the overlapping area is aligned with the body suture hole 10 of the SiC / SiC composite material body 9 in the overlapping area. The repair body 12 and the SiC / SiC composite material body 9 to be repaired can be assembled to obtain the required complete material shape.

[0170] (3) Thread preparation: According to the suture specification design requirements, the continuous SiC fiber bundle of 0.5K is divided into one strand with a length of 100mm. The SiC fiber bundle is placed in a chemical vapor deposition furnace to prepare a pyrolytic carbon coating on the surface of the SiC fiber bundle. One strand of SiC fiber bundle is twisted together with one strand of aramid fiber bundle to complete the preparation of one suture.

[0171] (4) Suturing and Fixing: Align the SiC / SiC composite material body 9 to be repaired with the repair body 12 according to the design requirements and fix them with a suture fixture. Insert the suture into the paired suture holes 10 and 13 of the body and the repair body in sequence according to the design requirements, while arranging the suture in the suture groove 11 and the suture groove 14 of the body to avoid protruding from the surface. Apply liquid polycarbosilane to the suture until the suture is completely wetted, and dry it in an oven at 200°C for 5 hours.

[0172] (5) Densification and reinforcement: The stitched SiC / SiC composite material, along with the stitching fixture, is placed in a chemical vapor deposition furnace. The temperature is first raised to 900℃ and held for 2 hours to convert polycarbosilane into SiC ceramic, filling the pores inside the suture, between the suture and the suture hole, and between the suture and the suture groove. The furnace temperature is then adjusted to 1100℃ for SiC chemical vapor deposition, and the stitched structure is deposited as a whole for 12 hours to achieve densification and reinforcement.

[0173] (6) Surface finishing: Remove the sewing fixture from the SiC / SiC composite material, finish the surface of the SiC / SiC composite material, remove excess material, and make the surface condition and size meet the design requirements.

[0174] The tensile properties of the repaired SiC / SiC composite material along its length were tested using a universal testing machine. The results showed that the maximum tensile load reached 1525N, which meets the design load requirement of 800N.

[0175] Comparative Example 1

[0176] In contrast, a high-temperature bonding repair technique was used to repair the same overlapping structure test piece. The test piece obtained had no continuous fiber connection between the repair material and the main body. The maximum tensile load was 539N, which could not meet the design requirement of 800N.

[0177] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings, disclosure, and other materials. In this specification, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude multiple components. A single processor or other unit can implement several functions listed in the specification. While certain measures are described in different embodiments, this does not mean that these measures cannot be combined to produce good results.

[0178] Although the invention has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made therein without departing from the spirit and scope of the invention. Accordingly, this specification and drawings are merely illustrative of the invention and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if such modifications and modifications fall within the scope of the invention and its equivalents, the invention is also intended to include such modifications and modifications.

Claims

1. A method of stitching repair of SiC / SiC composite material, characterized by, The application relates to a SiC / SiC composite material suture repair method for repairing a whole defect in a thickness direction. S10. Removing a damaged part of the SiC / SiC composite material to obtain a SiC / SiC composite material body with a space to be repaired; S11. Designing geometric shapes and size parameters of a body suture interface according to original structural strength design parameters of the damaged part of the SiC / SiC composite material, a load type in actual service conditions and mechanical property requirements after repair, wherein the body suture interface is composed of a body suture hole and a body suture groove; S12. Preparing a repair body, wherein the repair body is made of the same material as the SiC / SiC composite material, the profile and surface of the repair body match the space to be repaired, and geometric shapes and size parameters of a repair body suture interface are the same as those of the body suture interface; S13. Preparing a suture, wherein the suture is a SiC fiber suture with a surface coating; S14. Placing the repair body in the space to be repaired and matching and aligning the repair body suture interface with the body suture interface; S15. Fixing one end of the suture in one of the body suture holes and then introducing the suture into the body suture groove, the repair body suture groove, the repair body suture hole and the body suture hole according to a preset threading path to complete suture fixing; After the suture fixing is completed, the SiC / SiC composite material suture repair method further comprises: applying a liquid organic SiC ceramic precursor on the suture and drying and curing the suture; After the drying and curing, the SiC / SiC composite material suture repair method further comprises: densification and reinforcement, specifically comprising the following steps: placing the SiC / SiC composite material body after the suture fixing and the drying and curing in a chemical vapor deposition furnace, first increasing the temperature to an inorganic conversion temperature of the organic SiC ceramic precursor to convert the organic SiC ceramic precursor into a SiC ceramic, and filling the pores between the suture, the body suture hole and the repair body suture hole and between the suture, the body suture groove and the repair body suture groove; and then adjusting the furnace temperature to a chemical vapor deposition process temperature to perform SiC chemical vapor deposition on the suture structure to realize densification and reinforcement; surface treatment, specifically comprising the following steps: removing the excess to make the surface state and size meet the design requirements.

2. The SiC / SiC composite sewn repair method of claim 1, wherein, When the load type of the damaged part is a tensile load, the body suture groove and the repair body suture groove are arranged along the tensile load direction; when the load type of the damaged part is a compression load, the normal direction of the suture interface is along the compression load direction; and when the load type of the damaged part is a shear load, a lap joint structure is arranged.

3. The SiC / SiC composite sewn repair method of claim 1, wherein, The density of the suture interface increases with the increase of the load, the interval of the suture interface decreases with the increase of the load, and the number of suture strands increases with the increase of the load; wherein the suture interface comprises the body suture interface and the repair body suture interface.

4. The SiC / SiC composite sewn repair method of claim 1, wherein, The diameters of the body suture hole and the repair body suture hole are equal and are denoted as D, the vertical distance from the center to the edge of the body suture hole and the repair body suture hole is equal and is denoted as L, L>=3D; the interval of the adjacent suture holes is H, H>=2.5D, and the suture hole comprises the body suture hole and the repair body suture hole.

5. The SiC / SiC composite sewn repair method of claim 4, wherein, The width and depth of the suture groove are equal to the diameter of the suture hole, and the suture groove includes a body suture groove and a repair body suture groove; the diameter of the suture hole is 0.02mm to 2mm larger than the diameter of the suture.

6. A method of stitching repair of SiC / SiC composite material, characterized by, The SiC / SiC composite material is in a rectangular structure, one side edge of the rectangular structure is notched and damaged, and the repair method comprises the following steps: S20. Remove the damaged part of the SiC / SiC composite material to obtain a SiC / SiC composite material body having a space to be repaired, and the space to be repaired is an open rectangle; S21. Analyze the stress characteristics of the damaged part, and the stress characteristics are simultaneously subjected to in-plane tensile load in two directions parallel to the adjacent two edges of the open rectangle, and based on this, the body suture interface is determined, specifically: the side wall of the open rectangle and the direction of the bottom wall extending to the solid part are arranged with equal interval body suture interfaces, and each body suture interface sequentially comprises a through body suture groove and a body suture hole in the direction of extending to the solid part; S22. Process the SiC / SiC composite repair body, the contour and profile of the repair body match the space to be repaired, and the number, geometric shape and size parameters of the repair body suture interface are the same as those of the body suture interface; S23. Process the suture, specifically: divide the continuous SiC fiber bundle according to the preset length and the preset number of strands; after division, place it in a chemical vapor deposition furnace to prepare a boron nitride coating on the surface of the SiC fiber bundle; twist the SiC fiber bundle with a preset number of strands and a preset number of nylon fiber bundles together to complete the preparation of the suture; S24. Place the repair body in the space to be repaired, and align the suture interfaces of the two and fix them by relying on the suture tooling; introduce the suture into the paired body suture hole and repair body suture hole according to the design requirements, and at the same time arrange the suture in the body suture groove and the repair body suture groove to avoid the protruding surface; brush liquid polycarbosilane on the suture until the suture is completely wet, and then dry it in an oven; S25. Consolidation: place the sutured SiC / SiC composite material and the suture tooling in a chemical vapor deposition furnace, first heat to a first preset temperature, keep warm for a first preset time, and convert the polycarbosilane to SiC ceramic, fill the pores inside the suture, between the suture and the suture hole, and between the suture and the suture groove, then adjust the furnace temperature to a second preset temperature, and perform SiC chemical vapor deposition for a second preset time to achieve densification and reinforcement; S26. Surface treatment, specifically including removing excess material to make the surface state and size meet the design requirements.

7. A method of stitching repair of SiC / SiC composite material, characterized by, The rectangular SiC / SiC composite material is in a rectangular structure, the rectangular structure is broken and damaged in the central position along the width direction, and the repair method comprises the following steps: S30. Remove the damaged part of the SiC / SiC composite material to obtain a SiC / SiC composite material body having a space to be repaired; S31. Analyze the stress characteristics of the damaged part, the stress characteristics are in-plane tensile load along the length direction, and based on this, determine the body stitching interface, specifically: thinning processing of the lap region along the stitching edge to the length direction, the lap region and the SiC / SiC composite material body near the lap region are provided with body stitching interfaces, the body stitching interfaces extend along the length direction and are uniformly distributed along the width direction; the body stitching interface includes a body stitching hole and a body stitching groove, at least two body stitching holes with the same central axis are provided on the same stitching interface, at least one body stitching hole penetrates the SiC / SiC composite material body, and the remaining body stitching holes penetrate the lap region; S32. Process the repair body, the repair body structure has the same contour, profile, lap region and repair body stitching interface as the SiC / SiC composite material body to be repaired; S33. Process the suture, specifically: divide the continuous SiC fiber bundle according to the preset length and the preset number of strands; after division, place it in a chemical vapor deposition furnace to prepare a boron nitride coating on the surface of the SiC fiber bundle; twist the SiC fiber bundle with a preset number of strands and a preset number of nylon fiber bundles together to complete the preparation of the suture; S34. Align the repair body with the stitching interface of the SiC / SiC composite material to be repaired and fix it with the stitching tool; introduce the suture into the paired body suture hole and repair body suture hole according to the design requirements, at the same time, arrange the suture in the body suture groove and the repair body suture groove to avoid protruding the surface; brush liquid polycarbosilane on the suture until the suture is completely soaked, and then dry it in an oven; S35. Densification and reinforcement: place the stitched SiC / SiC composite material together with the stitching tool in a chemical vapor deposition furnace, first heat to a third preset temperature, keep it for a third preset time, so that the polycarbosilane is converted into SiC ceramic, and the pores between the suture, the suture and the suture hole, and the suture and the suture groove are filled, then adjust the furnace temperature to a fourth preset temperature, perform SiC chemical vapor deposition, and deposit the entire stitching structure for a fourth preset time to achieve densification and reinforcement; S36. Surface treatment, specifically including removing excess material, so that the surface state and size meet the design requirements.

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