A load / heat integrated ordered porous sweating composite structure and a preparation method thereof

Abstract

The application relates to the technical field of aircraft thermal protection, and particularly discloses a preparation method of a bearing / heat-proof integrated ordered porous sweating composite structure, which comprises the following steps: preparing a three-dimensional fiber preform, phthalonitrile resin pouring, cutting processing and aluminum wire removal; and the bearing / heat-proof integrated ordered porous sweating composite structure comprises an ordered porous sweating structure, a cooling working medium flow cavity and a cooling working medium storage tank, the ordered porous sweating structure is a bearing part of a component main body, and the ordered porous sweating structure is provided with a micropore flow channel for sweating cooling; the ordered porous composite material sweating structure of the application can have higher bearing capacity while the sweating cooling performance is considered, and the specific strength is far higher than that of the commonly-used metal and ceramic sweating materials; the bearing and sweating structure functions are simultaneously realized; the hierarchical structure of the sweating structure can be reduced, the overall thickness of the sweating system is reduced, and the negative weight of the aircraft is greatly reduced.

Description

Technical Field

[0001] This invention belongs to the field of aircraft thermal protection technology, specifically relating to an integrated load-bearing / heat-protection ordered porous sweating composite structure and its preparation method. Background Technology

[0002] Due to its high cooling efficiency, sweating cooling technology is one of the most effective cooling methods for hot-end components of modern aircraft. Thanks to the efforts of scholars worldwide, sweating cooling technology has been extensively and thoroughly studied. Current research on sweating cooling mainly focuses on cooling efficiency, neglecting mechanical strength, which significantly limits its application scenarios.

[0003] Furthermore, due to the non-uniform pore structure of traditional sintered porous materials, it is impossible to supply coolant that matches external aerodynamic heat and force under the same driving pressure. This results in the coolant supplied to a localized location precisely absorbing the heat flow entering that location. Therefore, it is essential to develop porous materials with precise geometry and adjustable distributed pores to achieve precise control over the transport and distribution of coolant within the porous structure, thereby enabling efficient cooling of localized hot spots. Thus, developing porous media with high mechanical strength and precise geometry is of great significance for sweat-induced cooling.

[0004] In existing sweating cooling technologies, the high density and low mechanical strength of the sweating materials cannot meet the requirements for lightweight aircraft. Furthermore, when the aircraft surface is subjected to uneven heat loads, traditional sweating structures cannot match the supply of coolant to the external aerodynamic heat, resulting in localized hot spots. Summary of the Invention

[0005] The purpose of this invention is to provide an integrated load-bearing / heat-proof ordered porous sweating composite structure and its preparation method to solve the problems mentioned in the background art.

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

[0007] A method for preparing an integrated load-bearing / heat-resistant ordered porous sweating composite structure includes the following steps:

[0008] Step 1: The carbon fiber bundles and aluminum wires are interwoven into a grid structure according to a certain pattern using three-dimensional weaving technology to obtain a three-dimensional fiber preform. The carbon fiber constitutes the warp and weft yarns, providing overall structural strength, and the aluminum wire constitutes the vertical yarn. The aluminum wire is used to remove the capillary sweating micropores obtained after the process. The diameter of the aluminum wire is between 50 and 300 μm.

[0009] Step 2: Using a vacuum infusion process, phthalic acid resin is infused into the fiber preform obtained in Step 1 for mixing, followed by curing and demolding to obtain the composite material component. After the three-dimensional fiber preform is placed into the vacuum infusion mold, the mold needs to be heated during the vacuum infusion process to ensure good flowability of the phthalic acid resin. The target temperature is 80–120°C. After the resin is fully impregnated, it is placed in an autoclave with a pre-set temperature and pressure program for curing. The curing process includes an impregnation stage, a curing stage, and a cooling stage. The process conditions for each stage are as follows:

[0010] Heating stage: The heating is carried out by vacuum negative pressure linear heating without positive pressure. The target temperature is 160-180℃ and the heating rate is 1-3℃ / min. In the heating stage, before the target temperature is reached, the hot pressing method is vacuum negative pressure linear heating without positive pressure.

[0011] Curing stage: The curing regime for phthalic acid resin is 200℃ for 2 hours, followed by heating at 250℃ for 4 hours. When the system temperature reaches 200℃, the pressurization stage begins. The pressure applied depends on the thickness of the product structure and ranges from 0.5 to 2.0 MPa. The pressurization stage must be maintained until the composite material is fully cured.

[0012] Cooling stage: The pressure during the cooling stage remains at 0.5–2.0 MPa. After cooling to room temperature, the pressure is released. The cooling rate during the cooling process is 0.4–0.6 °C / min.

[0013] Step 3: The surface of the composite material component obtained in Step 2 is machined to a thickness between 0.1 and 0.3 mm to remove the resin from the surface of the composite material, exposing the aluminum wires of the vertical yarn; then the aluminum wires are removed using an alkaline solution.

[0014] Step 4: After removing the aluminum wire, the ordered porous composite material is ultrasonically cleaned in acetone and anhydrous ethanol to remove any debris that may remain inside. Then it is dried at 80°C for 10 hours to obtain the above-mentioned ordered porous composite material sweating structure.

[0015] An integrated load-bearing / heat-proof ordered porous sweating composite structure includes an ordered porous sweating structure, a cooling medium flow cavity, and a cooling medium storage tank. The ordered porous sweating structure is the load-bearing part of the main component, with a thickness of 1 to 20 mm. The ordered porous sweating structure is provided with microporous channels for sweating and cooling, with a micropore diameter of 50 to 300 μm.

[0016] Preferably, the cooling medium storage tank is provided with a cooling medium, which flows through a cooling medium flow cavity and is cooled by sweating through an ordered porous sweating structure.

[0017] Preferably, the ordered porous sweating composite structure is integrally formed using three-dimensional weaving technology of composite materials.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. The ordered porous composite material sweating structure of the present invention can have high load-bearing capacity while taking into account sweating and cooling performance, and its specific strength far exceeds that of commonly used metal and ceramic sweating materials.

[0020] 2. This invention simultaneously serves as both a load-bearing and sweating structure; it can reduce the hierarchical structure of the sweating structure, decrease the overall thickness of the sweating system, and greatly reduce the negative weight of the aircraft.

[0021] 3. The ordered porous composite material sweating structure of the present invention adopts integrated molding, which reduces the connection problems of traditional sweating structures, thereby reducing the structural complexity of the entire sweating system and improving the reliability of the entire sweating system;

[0022] 4. The ordered porous composite material sweating structure of the present invention is provided with designable interconnected micropores, which reduces the flow resistance of the cooling medium and realizes rapid transport of the cooling medium and rapid response of heat protection; at the same time, the diameter, spatial arrangement, opening position and opening ratio of the micropores can be adjusted to meet the cooling requirements of different areas of the aircraft surface temperature and realize the efficient utilization of the cooling medium. Attached Figure Description

[0023] Figure 1 This is a three-dimensional schematic diagram of the fiber braid of the present invention;

[0024] Figure 2 This is a schematic diagram of the sweating structure of the present invention;

[0025] Figure 3 This is a comparison diagram of the strength of the sweating materials of this invention;

[0026] Figure 4 This is a schematic diagram comparing the cooling efficiency of the present invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1:

[0029] Please see Figure 1 - Figure 4As shown, a method for preparing an integrated load-bearing / heat-resistant ordered porous sweating composite structure includes the following steps:

[0030] Step 1: Carbon fiber bundles and aluminum wires are interwoven into a grid structure according to a certain pattern using three-dimensional weaving technology to obtain a three-dimensional fiber preform. The carbon fiber constitutes the warp and weft yarns, providing overall structural strength, while the aluminum wire constitutes the vertical yarn. The aluminum wire is used to remove the capillary sweating micropores obtained after the process. The diameter of the aluminum wire is between 50 and 300 μm.

[0031] The ordered porous composite material sweating structure described in this invention is integrally molded. The three-dimensional fiber preform includes the entire sweating structure, including the ordered porous sweating structure, the cooling medium flow cavity, and the cooling medium storage tank. In this invention, the diameter of the aluminum wire is directly related to the thickness of the sweating structure. Since the micropores contain capillary forces, the depth-to-diameter ratio (thickness:diameter) is generally between 3 and 60, which can ensure the overall morphology of the micropores and the clean removal of the internal aluminum wires.

[0032] Step 2: Using a vacuum infusion process, phthalic acid resin is infused into the fiber preform obtained in Step 1 for mixing, followed by curing and demolding to obtain the composite material component. After the three-dimensional fiber preform is placed into the vacuum infusion mold, the mold needs to be heated during the vacuum infusion process to ensure good flowability of the phthalic acid resin. The target temperature is 80–120°C. After the resin is fully impregnated, it is placed in an autoclave with a pre-set temperature and pressure program for curing. The curing process includes an impregnation stage, a curing stage, and a cooling stage. The process conditions for each stage are as follows:

[0033] Heating stage: Heating is carried out using a vacuum negative pressure linear heating method without positive pressure. The target temperature is 160-180℃, and the heating rate is 1-3℃ / min. During the heating stage, before the target temperature is reached, the hot pressing method is a vacuum negative pressure linear heating method without positive pressure. This can effectively prevent the overall structure of the three-dimensional fiber preform from deforming, and ensure the fluidity of the resin so that the resin can be further dispersed and impregnated in the three-dimensional fiber preform, filling the internal pores and fully impregnating the three-dimensional fiber braid.

[0034] Curing stage: The phthalic acid resin curing regime is 200℃ for 2 hours, followed by heating at 250℃ for 4 hours. When the system temperature reaches 200℃, the pressurization stage begins. The pressure applied depends on the thickness of the product structure and ranges from 0.5 to 2.0 MPa. The pressurization stage must be maintained until the composite material is fully cured to ensure that the aluminum wires inside the fiber preform do not deform due to the different thermal expansion rates caused by the temperature increase, thus preventing internal thermal stress.

[0035] Cooling stage: The pressure during the cooling stage remains at 0.5-2.0 MPa. After cooling to room temperature, the pressure is released. The cooling rate during the cooling process is 0.4-0.6℃ / min. In this invention, the cooling rate of 0.4-0.6℃ / min can effectively avoid the generation of residual stress and avoid adverse effects on the performance of the final ordered porous composite material.

[0036] Step 3: The surface of the composite material component obtained in Step 2 is machined to a thickness between 0.1 and 0.3 mm to remove the resin from the surface of the composite material, exposing the aluminum wires of the vertical yarn; then the aluminum wires are removed using an alkaline solution.

[0037] Step 4: After removing the aluminum wire, the ordered porous composite material is ultrasonically cleaned in acetone and anhydrous ethanol to remove any debris that may remain inside. Then it is dried at 80°C for 10 hours to obtain the above-mentioned ordered porous composite material sweating structure.

[0038] When the aspect ratio of the composite material structure is low, the composite material component is immersed in an alkaline solution to dissolve and remove the aluminum wire, resulting in an ordered porous composite material. When the aspect ratio of the composite material structure is high, a pressure device is needed to push the alkaline solution through the capillary pores to ensure that the aluminum wire is completely removed.

[0039] in Figure 3 This is a schematic diagram showing the specific strength of composite materials compared to SiC ceramics, steel, and aluminum alloys. Figure 4 This is a graph showing the cooling efficiency analysis of the composite material of this invention and traditional ceramic materials.

[0040] Depend on Figure 1 and Figure 2 It is known that a sweating structure of an ordered porous composite material integrating load-bearing and heat protection is prepared by using resin-based fiber-reinforced composite materials to replace traditional porous ceramic and porous metal sweating materials to prepare an ordered porous sweating structure with high specific strength and designable cooling working fluid channels.

[0041] This structure has high mechanical properties, good sweating cooling efficiency and rapid flow capability of the cooling medium, and is suitable for components that require active thermal protection, such as the outer surface of hypersonic aircraft.

[0042] The aforementioned integrated load-bearing / heat-resistant ordered porous composite material sweating structure includes an ordered porous sweating structure, a cooling medium flow cavity, and a cooling medium storage tank.

[0043] The sweating structure of the ordered porous composite material integrating load-bearing and heat protection is integrally molded using a high-temperature resistant resin-based composite material. The resin-based composite material itself possesses high specific strength and high specific stiffness, which can significantly reduce weight while meeting load-bearing requirements, thus satisfying the lightweight requirements of the cooling structure. Preferably, the ordered porous sweating structure serves as the load-bearing part of the main component, with a thickness ranging from 1 to 20 mm.

[0044] The ordered porous sweating structure contains microporous channels for sweating and cooling. Preferably, the micropore diameter of the directional porous sweating structure is 50-300 μm.

[0045] The cooling medium is installed in the cooling medium storage tank. The cooling medium flows through the cooling medium flow cavity and is cooled by sweating through the ordered porous sweating structure.

[0046] The ordered porous composite material sweating structure uses high-temperature resistant resin-based composite material as the material of the overall structure, thereby reducing the structural complexity of the entire sweating system and improving the reliability of the entire sweating system; it also reduces the overall thickness of the sweating system, greatly reducing the negative weight of the aircraft.

[0047] The ordered porous composite material sweating structure is equipped with interconnected micropores, which reduces the flow resistance of the cooling medium and enables rapid transport of the cooling medium and rapid response of heat protection. At the same time, the diameter, spatial arrangement, opening position and porosity of the micropores can be adjusted to meet the cooling requirements of different temperature areas on the surface of the aircraft and achieve efficient utilization of the cooling medium.

[0048] The ordered porous composite material sweating structure serves as both a load-bearing and sweating structure, thereby reducing the structural complexity of the entire sweating system and improving its reliability; it also reduces the overall thickness of the sweating system, significantly reducing the negative weight of the aircraft.

[0049] The directional porous sweating structure utilizes a three-dimensional weaving technique for composite materials to achieve its integral molding. The ordered porous composite material incorporates chemically soluble or physically (including pyrolysis and melting) filaments into a fiber-reinforced preform using a three-dimensional weaving technique. After the composite material is molded, these filaments are removed using chemical or physical methods, resulting in a porous structure containing custom-designed flow channels and micropores.

[0050] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an integrated load-bearing / heat-resistant ordered porous sweating composite structure, characterized in that, Includes the following steps: Step 1: The carbon fiber bundles and aluminum wires are interwoven into a grid structure according to a certain pattern using three-dimensional weaving technology to obtain a three-dimensional fiber preform. The carbon fiber constitutes the warp and weft yarns, providing overall structural strength, and the aluminum wire constitutes the vertical yarn. The aluminum wire is used to remove the capillary sweating micropores obtained after the process. The diameter of the aluminum wire is between 50 and 300 μm. Step 2: Using a vacuum infusion process, phthalic acid resin is infused into the fiber preform obtained in Step 1 for mixing, followed by curing and demolding to obtain the composite material component. After the three-dimensional fiber preform is placed into the vacuum infusion mold, the mold needs to be heated during the vacuum infusion process to ensure good flowability of the phthalic acid resin. The target temperature is 80~120℃. After the resin is fully impregnated, it is placed in an autoclave with a pre-set temperature and pressure program for curing. The curing process includes an impregnation stage, a curing stage, and a cooling stage. The process conditions for each stage are as follows: Heating stage: The heating is carried out by vacuum negative pressure linear heating without positive pressure. The target temperature is 160~180℃ and the heating rate is 1~3℃ / min. In the heating stage, before the target temperature is reached, the hot pressing method is vacuum negative pressure linear heating without positive pressure. Curing stage: The curing regime for phthalic acid resin is 200℃ for 2 hours, followed by heating at 250℃ for 4 hours. When the system temperature reaches 200℃, the pressurization stage begins. The pressure applied depends on the thickness of the product structure and is 0.5~2.0MPa. The pressurization stage must be maintained until the composite material is fully cured. Cooling stage: The pressure during the cooling stage remains at 0.5~2.0MPa. After cooling to room temperature, the pressure is released. The cooling rate during the cooling process is 0.4~0.6℃ / min. Step 3: The surface of the composite material component obtained in Step 2 is machined to a thickness between 0.1 and 0.3 mm to remove the resin from the surface of the composite material, exposing the aluminum wires of the vertical yarn; then the aluminum wires are removed using an alkaline solution. Step 4: After removing the aluminum wire, the ordered porous composite material is ultrasonically cleaned in acetone and anhydrous ethanol to remove any debris that may remain inside. Then it is dried at 80°C for 10 hours to obtain the above-mentioned ordered porous composite material sweating structure.

2. The method for preparing a load-bearing / heat-resistant integrated ordered porous sweating composite structure according to claim 1, characterized in that: When the aspect ratio of the composite material component is low, the component is immersed in an alkaline solution to dissolve and remove the aluminum wire, resulting in an ordered porous composite material. When the aspect ratio of the composite material component is high, a pressure device is needed to push the alkaline solution through the capillary pores to ensure that the aluminum wire is completely removed.

3. A load-bearing / heat-resistant integrated ordered porous sweating composite structure prepared by the preparation method according to any one of claims 1-2, characterized in that: It includes an ordered porous sweating structure, a cooling medium flow cavity, and a cooling medium storage tank. The ordered porous sweating structure is the load-bearing part of the main body of the component, and its thickness is 1 to 20 mm. The ordered porous sweating structure is provided with microporous channels for sweating and cooling, and the micropore diameter is 50 to 300 μm.

4. The integrated load-bearing / heat-resistant ordered porous sweating composite structure according to claim 3, characterized in that: The cooling medium is provided in the cooling medium storage tank. The cooling medium flows through the cooling medium flow cavity and is cooled by sweating through the ordered porous sweating structure.

5. The integrated load-bearing / heat-resistant ordered porous sweating composite structure according to claim 3, characterized in that: The ordered porous sweating composite structure uses three-dimensional weaving technology of composite materials to achieve the integral molding of its structure.

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