Screw for connecting aerobic long-time hypersonic aircraft and manufacturing method thereof

Abstract

The invention belongs to the technical field of high-temperature fire-resistant composite materials, and discloses a screw for connection of an aerobic long-time hypersonic aircraft and a manufacturing method of the screw. The screw comprises a core body made of a high-temperature alloy material, a heat insulation layer reinforced by a phase-change material and an ablation-resistant shell reinforced by ablation-resistant powder, and the core body and the heat insulation layer are integrally wrapped by the ablation-resistant shell. The screw is ablated through the ablation-resistant shell to prevent heat, and the core body in the screw is protected through phase-change heat absorption and low-thermal-conductivity heat insulation of the heat insulation layer. The screw has long-time anti-ablation capacity and heat insulation capacity and also has the high-temperature strength performance of high-temperature alloy metal, meanwhile, the ablation-resistant shell of the screw integrally wraps the core body and the heat insulation layer, the risk of structural failure caused by high-temperature falling does not exist, the overall reliability of the screw is high, and the screw is suitable for connection of aerobic long-time hypersonic aircrafts. The screw manufacturing method is relatively simple in required equipment, convenient to operate, stable in process, high in production efficiency and suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature refractory composite material technology, specifically relating to a screw for connecting aerobic long-duration hypersonic aircraft and its manufacturing method. Background Technology

[0002] Hypersonic vehicles generate significant heat through friction with the atmosphere during high-speed flight, causing temperatures in areas such as the nose cone and leading edge to reach 1800°C. Furthermore, as the flight distance increases, the flight time within the atmosphere exceeds 1000 seconds. This necessitates that the screws used for vehicle connections possess long-term ablation resistance and high-temperature strength. Resin-based composite materials offer advantages such as ablation resistance and low manufacturing costs; however, they decompose at high temperatures, resulting in a significant decrease in strength. Screws made from these materials cannot meet the high-temperature connection strength requirements of aircraft. Typical high-temperature alloys maintain a tensile strength exceeding 400 MPa at 1200°C, surpassing the room-temperature tensile strength of resin-based composites and carbon / carbon composites (generally not exceeding 300 MPa). High-temperature alloys exhibit a clear advantage in high-temperature strength; however, their melting points generally do not exceed 1400°C, and their ablation resistance is poor.

[0003] In existing technologies, C / SiC ceramic matrix composite screws are commonly used high-temperature and ablation-resistant connecting screws in hypersonic vehicles. C / SiC ceramic matrix composites are carbon fiber reinforced ceramic matrix composites, possessing advantages such as high-temperature resistance, ablation resistance, and oxidation resistance. Due to the property that carbon fibers have higher strength at high temperatures than at room temperature, the high-temperature strength of ceramic matrix composites is superior to that at room temperature, with a tensile strength of 200-400 MPa at 1200℃. The preparation process of C / SiC ceramic matrix composites is complex, requiring interface protection of carbon fibers, followed by more than ten rounds of impregnation and high-temperature pyrolysis using expensive ceramic precursors. The molding cycle of C / SiC ceramic matrix composites generally takes several months, resulting in a long molding cycle and very high costs.

[0004] The company's invention of the ablation-resistant connector (patent application number CN202511431570.0) can be used as a high-temperature resistant connecting screw, but it can only be used under high temperature for a short time, and the working time should not exceed 2 minutes, which cannot meet the connection requirements of aerobic long-duration hypersonic aircraft. Summary of the Invention

[0005] The purpose of this application is to provide a screw for connecting aerobic long-duration hypersonic aircraft and a method for manufacturing the same, aiming to solve the problems of high cost, long cycle time and complex manufacturing process of current C / SiC composite screws for connecting aerobic long-duration aircraft.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] On one hand, a screw for connecting a long-duration hypersonic vehicle with oxygen is provided. The screw includes a core and an ablation-resistant outer shell. The core is composed of an integrally formed frustum and a cylinder. The small end face of the frustum and one end of the cylinder are integrally formed. The cylinder has an external thread in its circumference. A heat insulation layer is bonded to the large end face of the frustum. The core is made of a high-temperature alloy, preferably a nickel-based or cobalt-based high-temperature alloy. The ablation-resistant outer shell is wrapped around the core and the heat insulation layer.

[0008] As one possible design, the insulation layer is made of phase change material, fiber needled felt and inorganic ceramics; the weight ratio of quartz fiber needled felt: phase change material: inorganic ceramics is 100:5-10:20-40.

[0009] As one possible design, the phase change material is one or a mixture of Al-Si alloy, Cu-Mg alloy, etc.; the phase change temperature of the phase change material is ≥400℃, and the latent heat of phase change is ≥400KJ / kg.

[0010] As one possible design, inorganic ceramics are obtained by curing inorganic sols; the inorganic sol is one or a mixture of silica sol, aluminum sol, silica-alumina sol, and water glass; the content of the inorganic sol is 10-30%.

[0011] As one possible design, the ablation-resistant shell is composed of chopped quartz fibers, phenolic resin, and ablation-resistant powder; the volume ratio of chopped quartz fibers: phenolic resin: ablation-resistant powder is 30-50: 30-50: 10-20; the length of the chopped quartz fibers is 10-50 mm.

[0012] As one possible design, the phenolic resin is one or a mixture of several types of barium phenolic resin, aminophenolic resin, magnesium phenolic resin, and high carbon phenolic resin; the phenolic resin content is ≥55%; the ablation-resistant powder is one or a mixture of several types of carbides, borides, and oxides of Hf, Zr, and Ti; and the particle size of the ablation-resistant powder is 0.1-10 micrometers.

[0013] On the other hand, a method for manufacturing screws for connecting aerobic long-duration hypersonic vehicles is provided, comprising the following steps:

[0014] S1: Prepare molding mold one. The internal cavity of molding mold one is matched with the shape of the core and the heat insulation layer after they are connected. Prepare molding mold two. The internal cavity of molding mold two is matched with the shape of the screw blank composed of the ablation-resistant outer shell, the core and the heat insulation layer.

[0015] S2: Process the core, and load the core and phase change material modified quartz fiber needled felt into the molding mold;

[0016] S3: Impregnation and curing with inorganic sol; demolding to obtain the screw intermediate;

[0017] S4: Preparation of prepreg for ablation-resistant shell molding;

[0018] S5 inserts the ablation-resistant shell molding prepreg and the screw intermediate prepared in S3 into molding mold two; heat and cure, the temperature of molding mold two is 70-100℃, hold for 2-8h, slowly raise the temperature to 140-200℃, and hold for 8-12h.

[0019] S6: Demold to obtain screw blank, and process to obtain the final screw.

[0020] As one possible design, S2 phase change material modified quartz fiber needled felt includes the following methods:

[0021] Phase change high-temperature alloy powder is evenly sprinkled on the surface of quartz fiber cloth;

[0022] Alternately lay layers of quartz fiber cloth and quartz fiber mesh;

[0023] Quartz fiber cloth and quartz fiber mesh are prepared into quartz needle-punched felt using a needle-punching process.

[0024] As one possible design, the preparation of ablation-resistant prepreg for molding shells includes the following methods:

[0025] Short-cut quartz fiber, phenolic resin, and ablation-resistant powder are initially mixed at a volume ratio of 30-50:30-50:10-20.

[0026] Place in a kneader and mix further for 1-12 hours;

[0027] Vacuum solvent removal treatment of premixed materials, vacuum degree ≤ -0.09Mpa, temperature 70-100℃, time 1-5h.

[0028] As one possible design, inorganic sol impregnation and curing includes the following methods:

[0029] When the vacuum level of the molding mold is ≤-0.09Mpa, the inorganic sol is drawn in and fills the cavity of the molding mold.

[0030] Immediately stop the vacuum and close the inlet and outlet valves of molding die one;

[0031] The temperature of molding mold 1 is 100-140℃, and it is kept at this temperature for 2-8 hours. Then, the inlet and outlet valves are opened, and the temperature of molding mold 1 is slowly increased to 150-200℃, and it is kept at this temperature for 1-3 hours.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The screw of this invention comprises a core made of a high-temperature alloy material, a heat-insulating layer reinforced with a phase change material, and an ablation-resistant outer shell made of ablation-resistant powder-reinforced ablation-resistant composite material. The ablation-resistant outer shell completely encloses the core and the heat-insulating layer. The screw provides heat protection through ablation resistance of the ablation-resistant outer shell and heat absorption and low thermal conductivity insulation through the phase change of the heat-insulating layer, protecting the core inside the screw. The core then bears the load at high temperatures. The screw possesses both long-term ablation resistance and heat insulation capabilities, as well as the high-temperature strength properties of high-temperature alloy metals. Furthermore, the ablation-resistant outer shell completely encloses the core and the heat-insulating layer, eliminating the risk of structural failure due to high-temperature detachment. The screw exhibits high overall reliability and is suitable for connection in long-duration hypersonic aircraft with aerobic operation.

[0034] 2. The method for preparing the connecting screws for aerobic long-endurance hypersonic vehicles of the present invention requires relatively simple equipment, is easy to operate, has a stable process, and high production efficiency, making it suitable for large-scale industrial production. The connecting screws for aerobic long-endurance hypersonic vehicles manufactured using this method are not only suitable for connecting aerobic long-endurance vehicles, but can also be used for connecting missile and rocket launch devices. Compared with the manufacturing process of C / SiC ceramic matrix composite screws, this method is simpler, lower in cost, and can reduce the molding cycle and cost by more than 80%. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of a screw used for connecting a long-duration hypersonic aircraft with oxygen. The left image is a three-dimensional view of the whole vehicle, and the right image is an internal cross-sectional view.

[0036] Figure 2 An exploded schematic diagram of a connecting screw for a long-duration aerobic hypersonic vehicle;

[0037] Figure 3 A schematic diagram showing the assembly relationship between the screw intermediate and the molding die in a method for manufacturing a screw for connecting aerobic long-duration hypersonic aircraft.

[0038] Figure 4 A schematic diagram showing the assembly relationship between the screw intermediate and the second molding die in a method for manufacturing a screw for connecting aerobic long-duration hypersonic aircraft.

[0039] Figure 5 A diagram showing the positional relationship between a screw and an oxyacetylene nozzle in a method for manufacturing a screw for connecting a long-duration aerobic hypersonic vehicle.

[0040] Figure 6 The images show a comparison of the appearance of the screws after ablation of the shells of Example 1 and Comparative Example 3, which are related to a method for manufacturing screws for connecting aerobic long-duration hypersonic vehicles. The left image is of Example 1, and the right image is of Comparative Example 3.

[0041] In the diagram: 1-Connecting screws for aerobic long-duration hypersonic vehicle; 11-Core; 12-Heat insulation layer; 13-Ablation-resistant outer shell; 14-Cross groove; 2-Mold 1; 21-First upper cover plate; 22-First left half mold; 23-First right half mold; 3-Mold 2; 31-Second upper cover plate; 32-Second left half mold; 33-Second right half mold; 4-Oxyacetylene nozzle; 5-Temperature sensor; Detailed Implementation

[0042] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to specific embodiments.

[0043] Example 1:

[0044] refer to Figure 1 (Screw structure diagram) and Figure 2 (Explosion diagram) The screw is manufactured with a core 11 and an ablation-resistant outer shell 13. The core 11 is composed of an integrally formed frustum and a cylinder, with the small end face of the frustum and one end of the cylinder integrally formed. The cylinder has an external thread in its circumference. The core 11 is made of nickel-based high-temperature alloy and the external thread specification is M12. A heat insulation layer 12 is bonded to the large end face of the frustum. The ablation-resistant outer shell 13 is wrapped around the core 11 and the heat insulation layer 12. A cross groove 14 is formed at the end of the ablation-resistant outer shell 11 near the frustum.

[0045] The insulation layer is 10mm thick, and the weight ratio of quartz fiber needle-punched felt, phase change material, and inorganic ceramic is 100:6:25. In this embodiment, the phase change material is an Al-Si alloy, with a phase change temperature of 580℃ and a latent heat of phase change of 500KJ / Kg. In this embodiment, the inorganic ceramic is prepared using silica sol curing; the silica sol content is 20%.

[0046] This embodiment also provides a method for manufacturing screws for connecting aerobic long-duration hypersonic aircraft, comprising the following steps:

[0047] S1: Prepare molding mold one; the shape of the screw intermediate body formed after the internal cavity of molding mold one is connected with the core and the heat insulation layer matches the shape of the molded mold one.

[0048] Prepare molding die two; the internal cavity of molding die two matches the shape of the screw blank, which is a combination of ablation-resistant outer shell, core, and heat insulation layer.

[0049] Among them, such as Figure 3As shown, the molding die 2 includes a first upper cover plate 21, a first left half mold 22, and a first right half mold 23 that are detachably connected to each other. In use, the screw intermediate formed after the core 11 and the heat insulation layer 12 are connected is located within the internal cavity formed by the connection of the first upper cover plate 21, the first left half mold 22, and the first right half mold 23. It should be noted that the connection between the first upper cover plate 21, the first left half mold 22, and the first right half mold 23 generally adopts a common detachable connection method, such as snap-fit, which will not be elaborated here.

[0050] like Figure 4 As shown, the molding die 3 includes a second upper cover plate 31, a second left half mold 32, and a second right half mold 33 that are detachably connected to each other. In use, the screw blank formed by the screw intermediate body and the ablation-resistant outer shell is placed within the internal cavity formed by the second upper cover plate 31, the second left half mold 32, and the second right half mold 33. It should be noted that the connection between the second upper cover plate 31, the second left half mold 32, and the second right half mold 33 generally adopts a common detachable connection method, such as snap-fit, which will not be elaborated here.

[0051] Before use, clean the surfaces of molding mold one and molding mold two, apply release agent twice, and let them air dry for 30 minutes after each application.

[0052] S2: Process the core, and load the core and phase change material modified quartz fiber needled felt into the molding mold;

[0053] Specifically, the core is screwed into the screw hole of M12 formed by the first left half mold 22 and the first right half mold 23 of the molding mold 2, and then the phase change material modified quartz fiber needle-punched felt is laid on it and the first upper cover plate 21 is covered.

[0054] Phase change material modified quartz fiber needled felt is part of the thermal insulation layer, and the specific preparation process is as follows:

[0055] Al-Si alloy powder is evenly sprinkled on the surface of quartz fiber cloth, and quartz fiber cloth and quartz fiber mesh are alternately laid. The quartz fiber cloth and quartz fiber mesh are then prepared into quartz needle-punched felt by needle punching process, thus obtaining phase change material modified quartz fiber needle-punched felt.

[0056] S3: Impregnation and curing with inorganic sol; demolding to obtain the screw intermediate;

[0057] Specifically: Vacuum the molding mold to a vacuum level of ≤-0.09Mpa, then draw in the silica sol and fill the cavity of the molding mold; immediately stop the vacuum and close the inlet and outlet valves of the molding mold; keep the temperature of the molding mold at 100℃ for 7 hours; open the inlet and outlet valves and slowly raise the temperature of the molding mold to 160℃ for 3 hours.

[0058] S4: Preparation of prepreg for ablation-resistant shell molding;

[0059] Specifically: the chopped quartz fiber length is 20mm, the phenolic resin is barium phenolic resin with a phenolic resin content of 70%; the ablation-resistant powder is zirconium carbide powder with a particle size of 8 micrometers. The chopped quartz fiber:phenolic resin:ablation-resistant powder is initially mixed at a volume ratio of 40:35:10, then further mixed in a kneader for 2 hours. Finally, the premix is ​​vacuum-treated to remove solvent at a vacuum degree ≤ -0.09 MPa, temperature 75℃, and time 4 hours.

[0060] S5. Reference Figure 4 The ablation-resistant shell molding prepreg obtained in step S4 and the screw intermediate prepared in step S3 are placed into the second left half mold 32 and the second right half mold 33 to form a cavity, and the second upper cover plate 31 is covered; then it is heated and cured at a mold temperature of 80°C for 7 hours; the temperature is slowly increased to 140°C and held for 10 hours.

[0061] S6: Demold to obtain screw blank, and process to obtain the final screw.

[0062] Specifically: the mold is removed by natural cooling to obtain a screw blank. The screw blank is then machined to obtain a screw.

[0063] Example 2:

[0064] The difference from Example 1 is:

[0065] The weight ratio of quartz fiber needled felt, phase change material, and inorganic ceramic in the thermal insulation layer is 100:7:21.

[0066] In this embodiment, inorganic ceramics are prepared by aluminum sol curing in step S3, and the aluminum sol content is 15%.

[0067] Before use, clean the surfaces of molding mold one and molding mold two, apply release agent three times, and let them air dry for 30 minutes after each application.

[0068] Vacuum the molding mold to a vacuum level ≤ -0.09 MPa, then inject aluminum sol into and fill the cavity of the molding mold. Immediately stop the vacuum and close the inlet and outlet valves of the molding mold. Maintain the temperature of the molding mold at 120℃ for 5 hours. Open the inlet and outlet valves and slowly raise the temperature of the molding mold to 170℃, then maintain the temperature for 2 hours.

[0069] In step S4, the phenolic resin is high-carbon phenolic resin with a phenolic resin content of 75%; the ablation-resistant powder is zirconium boride with a particle size of 5 micrometers. Short-cut quartz fibers, phenolic resin, and ablation-resistant powder are initially mixed at a volume ratio of 40:40:15, then further mixed in a kneader for 4 hours. Finally, the premix is ​​vacuum-treated to remove solvent at a vacuum degree ≤ -0.09 MPa, a temperature of 90°C, and a time of 2 hours.

[0070] In step S5, the mold temperature is 90℃ and held for 5 hours; then the temperature is slowly increased to 160℃ and held for 8 hours.

[0071] Example 3:

[0072] The difference from Example 1 is:

[0073] The insulation layer uses AL-Cu alloy as the phase change material; the phase change temperature of the phase change material is 548℃, the latent heat of phase change is 420J / g, and the inorganic ceramic is prepared by curing with aluminosilicate sol; the aluminosilicate sol has a glue content of 16%.

[0074] Before use, clean the surfaces of molding mold one and molding mold two, apply release agent three times, and let them air dry for 30 minutes after each application.

[0075] Vacuum the molding mold to a vacuum level ≤ -0.09 MPa, then inject and fill the mold cavity with the silica-alumina sol. Immediately stop the vacuum and close the mold's inlet and outlet valves; maintain the mold temperature at 135℃ for 3 hours; then open the inlet and outlet valves and slowly raise the mold temperature to 190℃, maintaining it for 1 hour.

[0076] In step S4, the phenolic resin is magnesium phenolic resin, with a phenolic resin content ≥65%. The ablation-resistant powder is hafnium carbide, with a particle size of 3 micrometers. Short-cut quartz fibers, phenolic resin, and ablation-resistant powder are initially mixed at a volume ratio of 45:50:18, then further mixed in a kneader for 8 hours. Finally, the premix is ​​subjected to vacuum desolvation treatment at a vacuum degree ≤-0.09 MPa, a temperature of 95℃, and a time of 1 hour.

[0077] In step S5, heat and cure the mold at 100°C for 2 hours; then slowly raise the temperature to 180°C and hold for 8 hours.

[0078] Comparative Example 1

[0079] Compared to Example 1, the heat insulation layer was removed, but everything else was the same as in Example 1. The screws prepared did not have a heat insulation layer.

[0080] Comparative Example 2

[0081] Compared with Example 1, the fiber needle-punched felt of the insulation layer does not contain phase change material, but is otherwise the same as Example 1. The insulation layer used to prepare the screw does not contain phase change material.

[0082] Comparative Example 3

[0083] Compared to Example 1, the prepreg for the ablation-resistant shell does not contain ablation-resistant powder, but otherwise remains the same as in Example 1. The ablation-resistant shell for the screw is not reinforced with ablation-resistant powder.

[0084] Comparative Example 4

[0085] Compared with Example 1, when processing the blank to obtain the screw, the ablation-resistant shell on the surface of the core is completely removed, and the ablation-resistant shell on the surface of the heat insulation layer is retained. Otherwise, it is the same as Example 1. The ablation-resistant shell of the screw is only wrapped around the heat insulation layer.

[0086] The cross-shaped grooves on the surface of the screw's ablation-resistant outer shell were machined away. A temperature sensor was connected to the tail of the core. The ablation retreat of the screw's outer shell and the stopping temperature of the core were tested according to the oxy-acetylene flame test method specified in the national military standard GJB 323A-1996. The specific ablation conditions were: oxygen flow rate of 1512 L / h, pressure of 0.4 MPa; acetylene flow rate of 1116 L / h, pressure of 0.095 MPa; oxygen to acetylene mixing ratio of 1.35; and flame heat flux density of 4 ± 0.2 MW / m³. 2 The nozzle inner diameter is 2mm, the vertical distance between the nozzle and the screw's ablation-resistant outer shell is 20mm, and the ablation time is 1000s; the positional relationship between the oxyacetylene nozzle and the screw is as follows: Figure 5 As shown.

[0087] The results of the oxyacetylene ablation test on the screws of Examples 1-3 and Comparative Examples 1-4 are as follows, as shown in Table 1 below:

[0088] 1. At 220 seconds of the test, the ablation-resistant outer shell of the screw in Comparative Example 4 fell off, and the ablation test was not completed.

[0089] 2. The ablation retreat amounts of Examples 1-3 and Comparative Examples 1-3 are 3.5mm, 2.5mm, 2.9mm, 2.8mm, 3.1mm, and 9.8mm, respectively. The ablation retreat amounts of the ablation-resistant shells of Examples 1-3 and Comparative Examples 1-2 are relatively small, while the ablation retreat amount of Comparative Example 3 is significantly larger.

[0090] 3. The core tail temperatures at the time of shutdown in Examples 1-3 and Comparative Examples 1-3 were 510℃, 450℃, 500℃, 1200℃, 780℃, and 1050℃, respectively. The core tail temperature in Examples 1-3 was relatively low, and the high-temperature alloy core had high strength at this temperature, which could meet the requirements of high-temperature connection. The screw in Comparative Example 1 had no heat insulation layer inside, and the core tail temperature was the highest. The screw in Comparative Example 2 had no phase change material inside the heat insulation layer, and the core tail temperature increased by about 270℃ compared with Example 1. The screw in Comparative Example 3 had no ablation-resistant powder reinforcement in the outer shell, and the outer shell had a large amount of ablation retreat, resulting in a high core tail temperature.

[0091] Table 1. Summary of oxyacetylene ablation test results for screws in Examples 1-3 and Comparative Examples 1-4

[0092] Examples / Comparative Examples Ablation retreat (mm) Parking temperature (°C) Remark Example 1 3.5 510 Example 2 2.5 450 Example 3 2.9 500 Comparative Example 1 2.8 1200 No insulation layer Comparative Example 2 3.1 780 Thermal insulation layer without phase change material Comparative Example 3 9.8 1050 The ablation-resistant shell contains no ablation-resistant powder. Comparative Example 4 - - The ablated outer shell detached after 220 seconds.

[0093] The results of the oxyacetylene ablation test on the above screws show that:

[0094] 1. The screws of Examples 1-3 have intact structures after ablation, small shrinkage of the ablation-resistant outer shell after ablation, and low core temperature. The screws of Examples 1-3 are suitable for connection of aerobic long-duration hypersonic aircraft.

[0095] 2. In the preparation of the screw in Comparative Example 1, the heat insulation layer inside the screw was removed. The heat of oxyacetylene was directly conducted to the core after passing through the ablation-resistant outer shell, resulting in the core having the highest temperature, which exceeded the working temperature of the core high-temperature alloy and could not meet the connection requirements of the aerobic long-duration hypersonic aircraft.

[0096] 3. In the preparation of the screw in Comparative Example 2, the phase change material in the screw insulation layer was omitted. High-temperature metal phase change materials have high latent heat of fusion, reaching over 400 J / g. When the phase change material reaches its phase change temperature, it absorbs heat through a solid-liquid phase change. As the temperature rises, the phase change material near the ablation-resistant outer shell begins to vaporize. The latent heat of vaporization of the phase change material can reach over 10 MJ / g, more than 20 times its latent heat of fusion. The phase change material can absorb a large amount of heat through the solid-liquid-gas transformation. Compared to Example 1, the absence of a phase change material in the insulation layer of the screw in Comparative Example 2 is the main reason for the significant increase in core temperature.

[0097] 4. In the preparation of the screws in Comparative Example 3, there was no ablation-resistant phenolic reinforcement inside the ablation-resistant shell. A comparison of the appearance of the ablation-resistant shells of Example 1 and Comparative Example 3 after ablation is shown below. Figure 6The left figure shows Example 1, and the right figure shows Comparative Example 3. Under high-temperature oxidation, the ablation-resistant powder and phenolic resin are ceramicized, forming a high-melting-point ceramic oxide on the surface. This prevents oxygen from oxidizing and eroding the internal matrix. After ablation, the material has a dense appearance with few pores, while protecting the fibers and reducing the overall ablation retreat. The ablation retreat of Example 1 is about 3.5 mm. The right figure shows Comparative Example 3. Under high-temperature oxidation, the phenolic resin decomposes and carbonizes, and then gradually oxidizes and disappears. After ablation, the material has many pores, and the fibers lose their protection and are lost under the action of high-temperature airflow. The overall ablation retreat is significantly increased. The ablation retreat of Comparative Example 3 is about 9.8 mm. The ablation-resistant powder has an important influence on the ablation performance of the ablation-resistant shell.

[0098] 5. In the preparation of screws in Comparative Example 4, the ablation-resistant shell only covered the heat insulation layer and did not completely wrap the heat insulation layer and the core. The poor integrity of the screw was the main reason why the ablation-resistant shell fell off during the ablation process.

[0099] Through the above experiments and analyses, it was found that the ablation-resistant powder can form an antioxidant ceramic body with phenolic resin at high temperatures, improving the ablation and heat resistance of the ablation-resistant shell. Adding a heat insulation layer inside the screw, reinforced with phase change materials, enhances the heat insulation and absorption capacity of the insulation layer. The ablation-resistant shell completely encapsulates the core and insulation layer, reducing the risk of shell detachment at high temperatures and improving the overall reliability of the screw. The aforementioned structural and material design is crucial for the screw's applicability to long-duration, high-speed aerobic aircraft. Furthermore, compared to existing C / SiC ceramic matrix composite screws, the molding cycle is ≤10 days, and the cost is ≤50 yuan, resulting in a reduction of over 80% in both overall cost and cycle time.

[0100] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A connecting screw for a long-duration aerobic hypersonic vehicle, characterized in that, The screw includes a core and an ablation-resistant outer shell; the core is composed of an integrally formed frustum and a cylinder, the small end face of the frustum and one end of the cylinder are integrally formed, the cylinder has an external thread in the circumference, and a heat insulation layer is bonded to the large end face of the frustum; the core is made of a high-temperature alloy, preferably a nickel-based or cobalt-based high-temperature alloy; the ablation-resistant outer shell is wrapped around the core and the heat insulation layer.

2. The screw for connecting a long-duration hypersonic aircraft according to claim 1, characterized in that, The insulation layer is made of phase change material, fiber needled felt and inorganic ceramics; the weight ratio of quartz fiber needled felt: phase change material: inorganic ceramics is 100:5-10:20-40.

3. The screw for connecting a long-duration hypersonic aircraft according to claim 2, characterized in that, The phase change material is one or a mixture of Al-Si alloy and Cu-Mg alloy; the phase change temperature of the phase change material is ≥400℃ and the latent heat of phase change is ≥400KJ / kg.

4. The screw for connecting aerobic long-duration hypersonic aircraft according to claim 2, characterized in that, Inorganic ceramics are obtained by curing inorganic sols; the inorganic sol is one or a mixture of silica sol, alumina sol, silica-alumina sol, and water glass; the content of the inorganic sol is 10-30%.

5. A screw for connecting a long-duration hypersonic aircraft according to claim 1, characterized in that, The ablation-resistant outer shell is composed of chopped quartz fibers, phenolic resin, and ablation-resistant powder; the volume ratio of chopped quartz fibers: phenolic resin: ablation-resistant powder is 30-50: 30-50: 10-20; the length of the chopped quartz fibers is 10-50 mm.

6. A screw for connecting a long-duration hypersonic aircraft according to claim 5, characterized in that, The phenolic resin is one or a mixture of several types of barium phenolic resin, aminophenolic resin, magnesium phenolic resin, and high carbon phenolic resin; the phenolic resin content is ≥55%; the ablation-resistant powder is one or a mixture of several types of carbides, borides, and oxides of Hf, Zr, and Ti; the particle size of the ablation-resistant powder is 0.1-10 micrometers.

7. A method for manufacturing a connecting screw for a long-duration hypersonic vehicle with oxygen as described in any one of claims 1-6, characterized in that, It includes the following steps: S1: Prepare molding mold one. The internal cavity of molding mold one is matched with the shape of the core and the heat insulation layer after they are connected. Prepare molding mold two. The internal cavity of molding mold two is matched with the shape of the screw blank composed of the ablation-resistant outer shell, the core and the heat insulation layer. S2: Process the core, and load the core and phase change material modified quartz fiber needled felt into the molding mold; S3: Impregnation and curing with inorganic sol; demolding to obtain the screw intermediate; S4: Preparation of prepreg for ablation-resistant shell molding; S5 inserts the ablation-resistant shell molding prepreg and the screw intermediate prepared in S3 into molding mold two; heat and cure, the temperature of molding mold two is 70-100℃, hold for 2-8h, slowly raise the temperature to 140-200℃, and hold for 8-12h. S6: Demold to obtain screw blank, and process to obtain the final screw.

8. A method for manufacturing a connecting screw for a long-duration hypersonic vehicle according to claim 7, characterized in that, S2 phase change material modified quartz fiber needled felt, comprising the following methods: Phase change high-temperature alloy powder is evenly sprinkled on the surface of quartz fiber cloth; Alternately lay layers of quartz fiber cloth and quartz fiber mesh; Quartz fiber cloth and quartz fiber mesh are prepared into quartz needle-punched felt using a needle-punching process.

9. A method for manufacturing a connecting screw for a long-duration hypersonic vehicle according to claim 7, characterized in that, The preparation of prepregs for ablation-resistant shell molding includes the following methods: Short-cut quartz fiber, phenolic resin, and ablation-resistant powder are initially mixed at a volume ratio of 30-50:30-50:10-20. Place in a kneader and mix further for 1-12 hours; Vacuum solvent removal treatment of premixed materials, vacuum degree ≤ -0.09Mpa, temperature 70-100℃, time 1-5h.

10. A method for manufacturing a connecting screw for a long-duration aerobic hypersonic vehicle according to claim 7, characterized in that, Inorganic sol impregnation and curing include the following methods: When the vacuum level of the molding mold is ≤-0.09Mpa, the inorganic sol is drawn in and fills the cavity of the molding mold. Immediately stop the vacuum and close the inlet and outlet valves of molding die one; The temperature of molding mold 1 is 100-140℃, and it is kept at this temperature for 2-8 hours. Then, the inlet and outlet valves are opened, and the temperature of molding mold 1 is slowly increased to 150-200℃, and it is kept at this temperature for 1-3 hours.

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