A method for preparing a full-carbon sandwich composite material

Abstract

The present invention discloses a method for preparing a full-carbon sandwich composite material. Specifically, the method comprises the following steps: preparing a hollow core mold and filling it with foam to prepare a solid lightweight core rod; inserting the lightweight core rod into a three-dimensional woven carbon fiber honeycomb fabric; sewing the carbon fiber fabric onto the upper and lower surfaces of the three-dimensional woven carbon fiber honeycomb fabric inserted into the lightweight core rod to prepare an integrated full-carbon sandwich structure fabric; using a vacuum infusion process to uniformly impregnate the integrated full-carbon sandwich structure fabric with resin; heating the mold to the initial curing temperature of the resin and maintaining the temperature, and then separating and demolding the mold; and reinforcing the upper and lower layers of the full-carbon sandwich structure composite material using an autoclave process to prepare a full-carbon fiber honeycomb sandwich composite material with uniform content and high planar accuracy. The material prepared by this method has the advantages of being lightweight, high-strength, and resistant to delamination and peeling; the demolding method is simple and convenient and does not damage the fibers; and the prepared full-carbon sandwich honeycomb composite material has uniform molding quality and high planar accuracy.

Description

Technical Field

[0001] The present invention belongs to the technical field of advanced composite materials and their preparation and forming, and in particular relates to a method for preparing a full-carbon sandwich composite material. Background Art

[0002] Currently, countries are increasingly demanding the application of high-performance space structures. The unique characteristics of the space environment place increasingly stringent demands on the corresponding structural material specifications. Traditional honeycomb core materials in sandwich structures are generally made of porous aluminum alloy honeycomb cores. As honeycomb sandwich structures are increasingly used in various spacecraft products, especially those requiring high precision and high thermal stability, such as antenna reflectors, increasingly stringent requirements are being placed on the thermal stability of the sandwich structures. The fabrication of composite antenna reflectors effectively addresses the impact of aluminum honeycomb deformation and expansion matching issues during the traditional aluminum honeycomb sandwich manufacturing process on the surface accuracy of the final product. Compared to reflectors fabricated using aluminum honeycomb sandwiches, the surface accuracy is improved by four times. The use of an all-carbon structure to fabricate antenna reflectors not only improves the surface accuracy but also significantly reduces thermal deformation. Therefore, research on lightweight carbon fiber honeycomb manufacturing technologies that integrate design, simulation analysis, and process technology is urgently needed to reduce carbon honeycomb density and increase its specific strength and stiffness.

[0003] CN113561522A discloses a device and method for preparing a three-dimensional woven fiber-reinforced honeycomb based on a thermal expansion flexible core mold, which includes a steel core mold, a thermal expansion silicone rubber flexible core mold, a base, a heating furnace, and a diversion valve. The cross-sectional shape of the steel core mold is the same as the shape of the woven honeycomb cells, and the cross-sectional shape of the thermal expansion silicone rubber flexible core mold is slightly smaller than the woven honeycomb cells. The steel core mold and the thermal expansion silicone rubber core mold are used in combination. However, the existing technology has the following technical defects: 1) The molding of the honeycomb core is achieved by a core mold, usually a metal mold, but the mold is heavy, difficult to put on and take off, and easily damages the fibers; 2) It is not an integral molding, and usually a film is used to bond the upper and lower layers to the honeycomb core for a second time. When the temperature is increased and cured, the film melts and flows to the bonding position, forming a glue nodule, which affects the mechanical properties of the overall sandwich structure, and fractures are prone to occur at the film bonding point; 3) The surface layer and the core of the sandwich material are usually vacuum bag pressed, the molding quality is not high, and the resin content uniformity is poor; 4) The preparation method that combines an expandable flexible core mold with a metal core mold cannot accurately control the uniformity of the wall thickness. Summary of the Invention

[0004] The present invention aims to address the issues raised in the aforementioned background technology by providing a high-precision, high-stability, all-carbon fiber sandwich composite antenna reflector and its preparation method, addressing thermal deformation caused by the mismatch between the carbon fiber surface layer and the honeycomb core material and resulting delamination. A fully integrated, layered, all-carbon sandwich structure is proposed, addressing the difficulty of threading and unmolding a continuously woven carbon fiber honeycomb core, improving molding quality, controlling molding precision, and enriching the molding process methods for preparing honeycomb composite materials.

[0005] In order to achieve the object of the present invention, the present invention discloses a method for preparing a full-carbon sandwich composite material, comprising the following steps:

[0006] Step 1: Prepare a hollow core mold and fill the hollow area of ​​the hollow core mold with foam to prepare a solid lightweight core rod;

[0007] Step 2: pre-treating the lightweight core rod and the platform mold, cutting the three-dimensional woven carbon fiber honeycomb fabric, and inserting the lightweight core rod into the three-dimensional woven carbon fiber honeycomb fabric;

[0008] Step 3: Using a stitching method, the carbon fiber fabric is stitched to the upper and lower surfaces of the three-dimensional woven carbon fiber honeycomb fabric inserted into the lightweight core rod to prepare an integrated full-carbon sandwich structure fabric;

[0009] Step 4: Using a vacuum infusion process, the integrated full-carbon sandwich structure fabric is uniformly impregnated with the resin and the fabric; the temperature is raised to the initial curing temperature of the resin and maintained at this temperature, and the core rod shrinkage tension is used to separate and demold the preformed honeycomb cells, thereby completing the preforming of the full-carbon sandwich structure composite material;

[0010] Step 5: Using an autoclave process, the upper and lower layers of the full-carbon sandwich structure composite material are reinforced to prepare a full-carbon fiber honeycomb sandwich composite material with uniform content and high plane accuracy.

[0011] Furthermore, the specific content of step 1 is to determine the design dimensions of the honeycomb wall thickness and side length according to application requirements, select the 3D printing material according to the curing temperature matching of different resin systems, use 3D printing technology to perform 3D printing according to the preset honeycomb wall thickness and side length requirements, and prepare a cavity core mold; fill the cavity area of ​​the cavity core mold with foam glue to prepare a solid lightweight core rod.

[0012] Furthermore, the specific content of step 2 is to cut the three-dimensional woven carbon fiber honeycomb fabric according to the design size and specifications according to the task plan, treat the lightweight core rods with a release agent or release wax, and insert the lightweight core rods into the honeycomb cavity of the three-dimensional woven carbon fiber honeycomb fabric in sequence; use the arrangement of each column of lightweight core rods to squeeze each other to achieve the pore shape in the W direction of the honeycomb, rotate and adjust the relative position of the lightweight core rods in the three-dimensional woven carbon fiber honeycomb fabric to be flat, and form a uniform honeycomb pore grid.

[0013] Furthermore, in step 3, a carbon fiber fabric larger than the size of the three-dimensional woven carbon fiber honeycomb fabric is prepared according to its L-direction length, and carbon fiber yarns are used as sutures on the upper and lower surfaces of the three-dimensional woven carbon fiber honeycomb fabric to sew the three-dimensional woven carbon fiber honeycomb fabric and the carbon fiber fabric together along the intersection of the honeycomb hole wall in the W direction to prepare an integrated full-carbon sandwich structure fabric.

[0014] Furthermore, in step 3, the sewn integrated full-carbon sandwich structure fabric does not contain a film layer, and the overall order is carbon fiber upper layer fabric, three-dimensional woven carbon fiber honeycomb fabric, and carbon fiber lower layer fabric to prepare an integrated full-carbon sandwich structure fabric.

[0015] Furthermore, in step 4, the integrated full-carbon sandwich structure fabric is formed by a vacuum infusion process. Preparatory work is required before forming, specifically, selecting a platform mold that corresponds to the size of the three-dimensional woven carbon fiber honeycomb fabric and has heating conditions, applying a release agent on the platform mold, and laying a release cloth; laying a release cloth and a guide net on the upper end of the vacuum infusion forming device in sequence, laying the first layer of vacuum bag, and arranging the vacuum system, and checking the vacuum degree of the vacuum system.

[0016] Furthermore, in step 4, a vacuum infusion process is used for the integrated full-carbon sandwich structure fabric to uniformly impregnate the resin and the fabric. Specifically, the resin is configured according to the curing agent ratio requirements of the different resin systems used, and then the vacuum infusion molding process is used after defoaming treatment to infuse the resin; the pressure is maintained until the resin completely impregnates the fabric and then heated for curing.

[0017] Furthermore, the preforming of the full-carbon sandwich structure composite material is completed in step 4, specifically, pre-heating to the initial curing temperature of the resin and keeping it warm and pressurized for a corresponding time. At this time, the spatial morphology of the honeycomb lattice is controlled by the size of the lightweight core rod, and the thickness and size of the honeycomb lattice are ensured to complete the preforming of the full-carbon sandwich structure composite material; further heating to a temperature node exceeding the glass transition temperature of the 3D printed material according to the resin curing curve, and keeping it warm for a corresponding time. At this stage, the honeycomb lattice has been initially cured and formed, and the cavity core mold prepared by 3D printing in the lightweight core rod is made of plastic material. As the temperature rises, the cavity core mold exceeds the glass transition critical point and undergoes a high elastic state change to a semi-solid gel state. At this time, the cavity core mold wraps the foaming agent filled therein to produce a shrinkage reaction and separates from the inner wall of the cured honeycomb lattice; stopping heating, breaking the vacuum on the surface of the full-carbon sandwich structure, cutting open the first layer of vacuum bag, and opening holes in the upper layer of the full-carbon sandwich composite material (using a wedge, a wooden stick, etc.) to remove the shrunk lightweight core rod from the lattice.

[0018] Furthermore, the specific content of preparing the full carbon fiber honeycomb sandwich composite material in step 5 is to add carbon fiber fabric to the upper and lower layers of the preformed full carbon sandwich composite material for reinforcement and impregnation with resin. At the same time, a limit plate with a certain weight is placed on the top reinforcement surface layer to accurately limit the thickness of the full carbon sandwich honeycomb during the curing process. The laying order is release cloth, lower layer reinforcement fabric, preformed full carbon sandwich composite material, upper layer reinforcement fabric, release cloth, limit plate, breathable felt, second layer vacuum bag, and the vacuum system is arranged to test the vacuum degree of the vacuum system. The vacuum bag is sealed and evacuated and then placed in an autoclave. Heat up and cure, the heating rate is 2°C / min, and the pressure in the tank is maintained at 0.1~0.3MPa. All temperatures are based on the autoclave platform mold temperature detected by thermocouples. According to the curing curve of the different resin systems used, pressurize and heat until completely cured and formed, and then naturally drop to room temperature for decompression and demolding. The excess size of the edge of the formed full-carbon honeycomb sandwich composite material is cut and the surface is treated to prepare a full-carbon fiber honeycomb sandwich composite material with uniform content and high plane precision.

[0019] Furthermore, the resins used include epoxy resin, cyanate ester, phenolic resin, polyimide resin, silicon-containing arylacetylene resin, and polyarylacetylene resin.

[0020] Furthermore, 3D printing materials include ABS plastic and PLA plastic.

[0021] Furthermore, the structural form of the cavity core mold prepared by 3D printing is not limited to triangles, quadrilaterals, pentagons and hexagons.

[0022] Compared with existing technologies, this invention offers significant advancements in the following areas: 1) Designing a hollow core mold fabricated using 3D printing technology and filling the cavity with a polyurethane expandable foaming agent to create a lightweight core rod for forming the 3D woven honeycomb cells. This lightweight core mold is lightweight and low-cost; 2) Using a stitching method, the carbon fiber surface layer is sewn together with the 3D woven honeycomb core to create a fully integrated, layered, all-carbon sandwich structure. This solves the thermal deformation problem caused by delamination between the carbon fiber surface layer and the honeycomb core, resulting in a lightweight, high-strength structure that resists delamination and peeling. 3) After the carbon fiber honeycomb core is initially solidified and formed, it has obvious pore characteristics. When the temperature is further increased, the 3D printing material melts, and the 3D cavity core mold is in a semi-solid gel state. The foam glue wrapped inside produces a shrinkage reaction and separates from the solidified and formed pore wall. After the upper layer of the sandwich structure is opened, the core mold can be easily removed from the honeycomb pores by using wedges, wooden sticks, etc. without damaging the fibers. The demoulding method is simple and convenient. 4) In the autoclave molding preparation, the limiting plate is used to accurately limit the thickness of the full-carbon sandwich honeycomb during the curing process to ensure the consistency and uniformity of the thickness after curing. The prepared full-carbon sandwich honeycomb composite material has uniform molding quality and high plane accuracy. 5) The preparation cost is low, the internal quality of the product is good, the wall thickness is uniform, and the molding accuracy is high.

[0023] In order to more clearly illustrate the functional characteristics and structural parameters of the present invention, further description is given below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0025] Figure 1 This is a schematic diagram of the molding and preparation method of a full-carbon sandwich composite material

[0026] Figure 2 It is a schematic diagram of a lightweight mandrel;

[0027] Figure 3 It is a schematic diagram of an integrated full-carbon sandwich structure fabric;

[0028] Figure 4 It is a schematic diagram of a full carbon fiber honeycomb sandwich composite material;

[0029] The accompanying drawings are marked as follows: 1. Cavity core mold; 2. Foam; 3. Lightweight core rod; 4. Integrated full-carbon sandwich structure fabric; 5. Lower layer reinforced carbon fiber fabric; 6. Upper layer reinforced carbon fiber fabric; 7. Release cloth; 8. Limiting plate; 9. Platform mold; 10. Breathable felt; 11. Vacuum bag; 12. Sealing strip; 13. Upper layer carbon fiber fabric; 14. Three-dimensional woven carbon fiber honeycomb fabric; 15. Lower layer carbon fiber fabric; 16. Suture line; 17. Full carbon fiber honeycomb sandwich composite material. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] Example

[0032] A method for forming and preparing a full-carbon sandwich composite material comprises the following steps:

[0033] (1) According to the performance parameters of the design match, the honeycomb side length is designed to be 12.8 mm, and the 3D printing consumables are made of PLA material. A regular hexagonal cavity core mold with a side length of 12.8 mm and a wall thickness of 1 mm is prepared by 3D printing, and the cavity area of ​​the cavity core mold is filled with polyurethane foam, and the excess enriched foam is removed to prepare a solid lightweight core rod;

[0034] (2) The lightweight core rods are treated with a release agent or a release wax, and the lightweight core rods are sequentially inserted into the honeycomb cavity of the three-dimensional woven carbon fiber honeycomb fabric. The lightweight core rods are arranged in a mutually squeezed manner to realize the pore shape in the W direction of the honeycomb. The relative position of the lightweight core rods in the three-dimensional woven carbon fiber honeycomb fabric is rotated and adjusted to be flat to form a uniform honeycomb pore grid.

[0035] (3) Cutting the three-dimensional woven carbon fiber honeycomb fabric in the L direction to prepare a slightly larger carbon fiber fabric, and using a stitching method, using carbon fiber yarn as stitching lines on the upper and lower surfaces of the three-dimensional woven carbon fiber honeycomb fabric, stitching the three-dimensional woven honeycomb fabric and the carbon fiber fabric together along the intersection of the honeycomb hole wall in the W direction to prepare an integrated full-carbon sandwich structure fabric.

[0036] (4) Before vacuum infusion molding of the integrated full-carbon sandwich structure fabric, preparation work is performed. A platform mold corresponding to the size of the three-dimensional woven carbon fiber honeycomb fabric and having heating conditions is selected, and a release agent is applied to the platform mold and a release cloth is laid. The release cloth and the guide net are laid in sequence on the upper end of the vacuum infusion molding device, the first layer of vacuum bag is laid, and the vacuum system is arranged to check the vacuum degree of the vacuum system.

[0037] (5) An epoxy resin system is selected, and the resin is configured and defoamed according to the ratio requirements of the resin and the curing agent. The integrated full-carbon sandwich structure fabric is then formed using a vacuum infusion process to uniformly impregnate the resin and the fabric. The pressure is maintained until the resin completely impregnates the fabric and then heated and cured.

[0038] (6) Preheating to the resin initial curing temperature of 60℃ and keeping it warm and pressurized for 2 hours. At this time, the spatial shape of the honeycomb grid is controlled by the size of the lightweight core rod, and the thickness and size of the honeycomb wall are guaranteed to complete the preforming of the full carbon sandwich structure composite material. Further heating to 130℃ according to the resin curing curve and keeping it warm for 2 hours. During this stage, the honeycomb grid has been initially cured and formed, and the PLA cavity core mold prepared by 3D printing in the lightweight core rod undergoes a high elastic state change to a semi-solid gel state as the temperature rises above the glass transition critical point. At this time, the cavity core mold wraps the foaming agent filled in it and produces a shrinkage reaction, separating from the inner wall of the cured honeycomb grid. Stop heating, break the vacuum on the surface of the full carbon sandwich structure, cut open the first layer of vacuum bag, and make holes in the upper layer of the full carbon sandwich composite material. Use wedges, wooden sticks, etc. to remove the shrunken lightweight core rod from the grid.

[0039] (7) Add carbon fiber fabric to the upper and lower layers of the preformed full carbon sandwich composite material for reinforcement and impregnation with resin. At the same time, place a solid fiberglass flat plate with a certain weight on the top reinforcement surface layer as a limit plate to accurately limit the thickness of the full carbon sandwich honeycomb during the curing process. The laying order is release cloth, lower layer reinforcement fabric, preformed full carbon sandwich composite material, upper layer reinforcement fabric, release cloth, limit plate, breathable felt, second layer vacuum bag, and arrange the vacuum system to test the vacuum degree of the vacuum system. After the vacuum bag is sealed and evacuated, it enters the autoclave and heats up for curing. The heating rate of the autoclave is 2℃ / min, and the pressure in the tank is maintained at 0.1~0.3MPa. All temperatures are based on the mold temperature of the autoclave platform detected by the thermocouple. According to the resin system curing curve of 130℃×2h+160℃×2h+180℃×2h+200℃×2h, it is completely cured and formed, and then naturally drops to room temperature for decompression and demolding. The excess size of the edge of the formed full-carbon honeycomb sandwich composite material is cut and the surface is treated to prepare a full-carbon fiber honeycomb sandwich composite material with uniform content and high plane precision.

[0040] Specifically, in this embodiment, the resin used in the entire molding process is not limited to epoxy resin, cyanate ester, phenolic resin, polyimide resin, silicon-containing arylacetylene resin, and polyarylacetylene resin.

[0041] Specifically, in this embodiment, the 3D printing material includes ABS plastic and PLA plastic.

[0042] Specifically, in this embodiment, the structural form of the cavity core mold prepared by 3D printing is not limited to triangle, quadrilateral, pentagon and hexagon.

[0043] like Figure 1-4 As shown, a cavity core mold 1 is prepared, and a foam glue 2 is filled into the cavity area of ​​the cavity core mold 1 to obtain a solid lightweight core rod 3; the lightweight core rod 3 and the platform mold 9 are pretreated, a three-dimensional woven carbon fiber honeycomb fabric 14 is cut, and the lightweight core rod is inserted into the three-dimensional woven carbon fiber honeycomb fabric 15; the upper carbon fiber fabric 13 and the lower carbon fiber fabric 15 are sewn together by a suture line 16 on the upper and lower sides of the three-dimensional woven carbon fiber honeycomb fabric 14 inserted into the lightweight core rod to prepare an integrated full-carbon sandwich structure fabric 4; a vacuum induction process is used to uniformly impregnate the integrated full-carbon sandwich structure fabric 4 with resin and fabric; the temperature is raised to the initial curing temperature of the resin and kept warm, and the core rod shrinkage tension is used to separate and demould the preformed honeycomb cells to complete the preforming of the full-carbon sandwich structure composite material; a hot press process is used to use the lower layer reinforcement carbon fiber fabric 5 and the upper layer reinforcement carbon fiber fabric 6 to reinforce the upper and lower layers of the full-carbon sandwich structure composite material to prepare a full-carbon fiber honeycomb sandwich composite material 17 with uniform content and high plane accuracy.

[0044] like Figure 1This is a schematic diagram of a method for forming and preparing a full-carbon sandwich composite material. The method involves sequentially laying a lower layer of reinforced carbon fiber fabric 5, an integrated full-carbon sandwich structure fabric 4, a lower layer of reinforced carbon fiber fabric 6, a demoulding cloth 7, a limiting plate 8, a breathable felt 10, and a vacuum bag 11 on a platform mold 9. The laid-up materials are then sealed with a sealing strip 12, and a vacuum system is arranged to test the vacuum degree. The material is then pushed into an autoclave device under pressure maintenance, and pressurized and heated according to the curing curve of the different resin systems used until the full-carbon honeycomb sandwich composite material is completely cured and formed. The material is then naturally cooled to room temperature, depressurized, and demoulded. The excess dimensions of the formed full-carbon honeycomb sandwich composite material are cut and surface treated to prepare a full-carbon fiber honeycomb sandwich composite material 17 with uniform content and high plane precision. Among them, the autoclave equipment includes a control system to achieve high-precision control of process parameters such as pressure, temperature, and cooling throughout the entire process; the vacuum system, including a vacuum pump, pipelines, vacuum gauges and vacuum valves, is used to provide vacuum conditions for the sealed all-carbon honeycomb sandwich composite material; the heating system, including stainless steel electric heating tubes, high-temperature fans, air duct plates, insulation layers and temperature control systems, is used to provide heating power to meet the temperature conditions for resin curing; the pressurization system, including compressors, gas tanks, pressure control valves, pipelines, pressure transmitters and pressure gauges, is used to provide uniform pressure for the molding of all-carbon honeycomb sandwich composite materials and improve quality consistency; the blowing system, including circulating fans, air guide plates and air guide covers, is used to accelerate heat flow conduction and circulation, and provide assistance for uniform molding of composite materials; the cooling system is used for circulating water cooling to reduce the temperature inside the tank.

[0045] like Figure 2 This is a schematic diagram of a lightweight core rod. The design size of the core rod side length is determined according to application requirements. A cavity core mold 1 is prepared using 3D printing technology, and foam glue 2 is filled in its cavity area. The lightweight core rod 3 is prepared by curing and molding.

[0046] like Figure 3 It is a schematic diagram of an integrated full-carbon sandwich structure fabric. The upper layer carbon fiber fabric 13 and the lower layer carbon fiber fabric 15 are cut to be slightly larger than the L-direction length of the three-dimensional woven carbon fiber honeycomb fabric. The upper and lower surfaces of the three-dimensional woven carbon fiber honeycomb fabric 14 are sewn together along the W direction at the intersection of the honeycomb hole walls using carbon fiber sutures 16 to prepare an integrated full-carbon sandwich structure fabric.

[0047] like Figure 4 It is a schematic diagram of a full carbon fiber honeycomb sandwich composite material. The excess size of the boundary of the formed full carbon honeycomb sandwich composite material is cut and the surface is treated to prepare a full carbon fiber honeycomb sandwich composite material 17 with uniform content and high plane precision.

[0048] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0049] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a full-carbon sandwich composite material, characterized in that: The following steps are involved: Step 1: Prepare a hollow core mold and fill the hollow area of ​​the hollow core mold with foam to prepare a solid lightweight core rod; Step 2: pre-treating the lightweight core rod and the platform mold, cutting the three-dimensional woven carbon fiber honeycomb fabric, and inserting the lightweight core rod into the three-dimensional woven carbon fiber honeycomb fabric; Step 3: Using a stitching method, the carbon fiber fabric is stitched to the upper and lower surfaces of the three-dimensional woven carbon fiber honeycomb fabric inserted into the lightweight core rod to prepare an integrated full-carbon sandwich structure fabric; Step 4: Using a vacuum infusion process on the integrated full-carbon sandwich structure fabric to uniformly impregnate the resin and fabric; The temperature is raised to the initial curing temperature of the resin and kept warm, and the core rod is separated from the preformed honeycomb cells by shrinkage tension to complete the preforming of the full carbon sandwich structure composite material; Step 5: Using an autoclave process, the upper and lower layers of the full-carbon sandwich structure composite material are reinforced to prepare a full-carbon fiber honeycomb sandwich composite material with uniform content and high plane accuracy; The specific content of step 1 is to determine the design dimensions of honeycomb wall thickness and side length according to application requirements, select 3D printing materials according to the curing temperature matching of different resin systems, use 3D printing technology to perform 3D printing according to the preset honeycomb wall thickness and side length requirements, and prepare a cavity core mold; fill the cavity area of ​​the cavity core mold with foam glue to prepare a solid lightweight core rod; The preforming of the full-carbon sandwich structure composite material in step 4 is specifically completed by preheating to the initial curing temperature of the resin and keeping it warm and pressurized for a corresponding time. At this time, the spatial morphology of the honeycomb lattice is controlled by the size of the lightweight core rod, and the thickness and size of the honeycomb lattice are guaranteed to complete the preforming of the full-carbon sandwich structure composite material; further heating to a temperature node exceeding the glass transition temperature of the 3D printed material according to the resin curing curve, and keeping it warm for a corresponding time. During this stage, the honeycomb lattice has been initially cured and formed, and the cavity core mold prepared by 3D printing in the lightweight core rod is made of plastic material. As the temperature rises, the cavity core mold exceeds the glass transition critical point and undergoes a high elastic state change to a semi-solid gel state. At this time, the cavity core mold wraps the foaming agent filled therein to produce a shrinkage reaction and separates from the inner wall of the cured honeycomb lattice; stop heating, break the vacuum on the surface of the full-carbon sandwich structure, cut open the first layer of vacuum bag, open holes in the upper layer of the full-carbon sandwich composite material, and remove the shrunk lightweight core rod from the lattice.

2. The method for preparing a full-carbon sandwich composite material according to claim 1, characterized in that: The specific content of step 2 is to cut the three-dimensional woven carbon fiber honeycomb fabric according to the design size and specifications according to the task plan, treat the lightweight core rod with a release agent or release wax, and insert the lightweight core rod into the honeycomb cavity of the three-dimensional woven carbon fiber honeycomb fabric in sequence; use the arrangement of each column of lightweight core rods to squeeze each other to achieve the pore shape of the honeycomb in the W direction, rotate and adjust the relative position of the lightweight core rod in the three-dimensional woven carbon fiber honeycomb fabric to be flat, and form a uniform honeycomb pore grid.

3. The method for preparing a full-carbon sandwich composite material according to claim 1, characterized in that: In step 3, a carbon fiber fabric larger than the size of the three-dimensional woven carbon fiber honeycomb fabric is prepared according to its L-direction length. Carbon fiber yarns are used as sutures on the upper and lower surfaces of the three-dimensional woven carbon fiber honeycomb fabric to sew the three-dimensional woven carbon fiber honeycomb fabric and the carbon fiber fabric together along the intersection of the honeycomb hole wall in the W direction to prepare an integrated full-carbon sandwich structure fabric.

4. The method for preparing a full-carbon sandwich composite material according to claim 1, characterized in that: In step 3, the sewn integrated full-carbon sandwich structure fabric does not contain a film layer, and the overall order is carbon fiber upper layer fabric, three-dimensional woven carbon fiber honeycomb fabric, and carbon fiber lower layer fabric to prepare an integrated full-carbon sandwich structure fabric.

5. The method for preparing a full-carbon sandwich composite material according to claim 1, characterized in that: In step 4, the integrated full-carbon sandwich structure fabric is formed by vacuum infusion process. Preparation work is required before forming, specifically, selecting a platform mold that corresponds to the size of the three-dimensional woven carbon fiber honeycomb fabric and has heating conditions, applying a release agent on the platform mold, and laying a release cloth; laying the release cloth and the guide net on the upper end of the vacuum infusion forming device in sequence, laying the first layer of vacuum bag, and arranging the vacuum system, and checking the vacuum degree of the vacuum system.

6. The method for preparing a full-carbon sandwich composite material according to claim 1, characterized in that: In step 4, the integrated full-carbon sandwich structure fabric is subjected to a vacuum infusion process to uniformly impregnate the resin and fabric. Specifically, the resin is configured according to the curing agent ratio requirements of the different resin systems used, and then the resin is infused using a vacuum infusion molding process after defoaming treatment; the pressure is maintained until the resin completely impregnates the fabric and then heated for curing.

7. The method for preparing a full-carbon sandwich composite material according to claim 1, characterized in that: The specific contents of preparing the full carbon fiber honeycomb sandwich composite material in step 5 are as follows: adding carbon fiber fabrics to the upper and lower layers of the preformed full carbon sandwich composite material for reinforcement and impregnation with resin; at the same time, placing a limit plate with a certain weight on the uppermost reinforcement surface layer to accurately limit the thickness of the full carbon sandwich honeycomb during the curing process; laying out in the order of release cloth, lower layer reinforcement fabric, preformed full carbon sandwich composite material, upper layer reinforcement fabric, release cloth, limit plate, breathable felt, second layer vacuum bag, arranging the vacuum system, and testing the vacuum degree of the vacuum system; the vacuum bag is sealed and evacuated and then placed in the autoclave; The temperature is raised for curing at a rate of 2°C / min, and the pressure in the tank is maintained at 0.1~0.3MPa. All temperatures are based on the temperature of the autoclave platform mold detected by thermocouples. The temperature is raised under pressure according to the curing curve of the different resin systems used until the product is fully cured and formed. The product is then naturally cooled to room temperature for pressure relief and demoulding. The excess size of the formed full-carbon honeycomb sandwich composite material is cut and surface treated to produce a full-carbon fiber honeycomb sandwich composite material with uniform content and high plane accuracy.

8. The method for preparing a full-carbon sandwich composite material according to claim 7, characterized in that: The resins used include epoxy resin, cyanate ester, phenolic resin, polyimide resin, silicon-containing arylacetylene resin or polyarylacetylene resin.

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