Additive manufacturing method of gradient porous ceramic-based composite material

Abstract

The invention relates to an additive manufacturing method of a gradient porous ceramic-based composite material, belongs to the technical field of additive manufacturing, and solves the problems that in the prior art, rapid manufacturing of a gradient porous ceramic structure is difficult to realize, density distribution and boundary of gradient ceramic cannot be accurately controlled, and light weight and high strength are difficult to consider at the same time. The invention discloses an additive manufacturing method of a gradient porous ceramic matrix composite product. The additive manufacturing method comprises the following steps: S1, preparing a ceramic raw material required by each ceramic matrix layer; s2, establishing a three-dimensional model of a gradient porous ceramic matrix composite product, and slicing; s3, prefabricating W layers of two-dimensional fiber fabric prefabricated members; s4, superposing n ceramic matrix layers and W two-dimensional fiber fabric prefabricated parts layer by layer through 3D printing; and S5, degreasing and sintering. Rapid manufacturing of the gradient porous ceramic structure is achieved, the density distribution and boundary of the gradient structure can be accurately controlled, the excellent performance of broadband wave transmission, mechanical strength, light weight, high temperature resistance, corrosion resistance and the like is considered, and the designability of the shape and the function is high.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to an additive manufacturing method for a gradient porous ceramic-based composite material. Background Art

[0002] Gradient porous ceramics are a new type of structural ceramics that combine porous ceramic structures with gradient materials, giving ceramics more superior comprehensive properties such as mechanics, temperature resistance, and broadband wave transmission. Taking the ceramic radome for aircraft as an example, its function is to protect the normal operation of high-speed aircraft electronic equipment, which requires it to have not only good aerodynamic shape and broadband wave transmission performance, but also a certain strength and rigidity to withstand the effects of aerodynamic loads. The manufacturing difficulty of ceramic radomes for aircraft is mainly that it is difficult to combine good broadband wave transmission performance, mechanical strength, lightweight, high temperature resistance, corrosion resistance and other excellent properties. Gradient porous ceramics can solve this problem very well. Different layers can be used to make the radome have a variety of excellent properties. The structure is composed of multiple layers of ceramic materials stacked together, and each layer of ceramic material has different porosity and density, and therefore has different dielectric constants.

[0003] At present, the traditional methods for manufacturing gradient porous ceramic structures mainly include the following three methods:

[0004] 1) Ceramic powders of different particle sizes are used as raw materials. The ceramic powders of different particle sizes are distributed in different areas of the mold by physical methods. After the pressureless sintering process is implemented, different densities can be obtained in different areas of the same structure. This method cannot accurately control the density and interface of each area, and due to the limitation of the mold during the molding process, complex structures cannot be manufactured.

[0005] 2) Add other materials that can volatilize during the sintering process to the ceramic powder raw materials, and use physical methods to make these materials occupy uneven positions in the ceramic powder. After the sintering process, the other added materials will volatilize, and then a ceramic structure with uneven density will be obtained. This method is also difficult to accurately control the density distribution area, and due to the limitation of the mold during the molding process, it is also difficult to form a complex structure.

[0006] 3) Make ceramic structures of different densities, and then assemble them together to form a complete variable density gradient structure. Although this method can control density and boundaries, it has low manufacturing efficiency and is not suitable for structures with complex shapes. The connection of the assembled parts is usually also a very difficult task, and the joints are prone to defects such as peeling and unreliability.

[0007] At present, the preparation technology of gradient ceramic structures is not mature enough, the process is complex and the cost is high. It is impossible to accurately control the density distribution area, and it is difficult to form structures with complex shapes. Especially for gradient porous ceramic structures, how to achieve rapid manufacturing of such ceramics, accurately control the density distribution and boundaries of ceramic gradient structures, and take into account both lightweight and high strength are all great challenges, and there is an urgent need to further explore new preparation methods. Summary of the invention

[0008] In view of the above analysis, the present invention aims to provide an additive manufacturing method for gradient porous ceramic-based composite materials to solve the problems in the prior art that it is difficult to achieve rapid manufacturing of gradient porous ceramic structures, the density distribution and boundaries of gradient ceramic structures cannot be accurately controlled, and it is difficult to achieve broadband wave transmission, lightweight and high strength at the same time.

[0009] The objective of the present invention is achieved through the following technical solutions:

[0010] The present invention provides an additive manufacturing method for a gradient porous ceramic-based composite material product, the additive manufacturing method comprising the following steps:

[0011] Step S1, preparing ceramic raw materials required for forming each ceramic matrix layer of a gradient structure along a gradient direction of the composite material;

[0012] Step S2, establishing a three-dimensional model of a gradient porous ceramic-based composite material product, wherein the XY plane is the gradient direction, and the Z direction perpendicular to the XY plane is set as the layer-by-layer stacking direction, and slicing is performed; wherein each layer of the two-dimensional fiber fabric is contained in the corresponding slice; each layer of the slice includes m gradient regions from the outer surface to the inside of the product, namely, the first gradient region, the second gradient region...the m-1th gradient region, the mth gradient region, 1≤m≤n, n is the number of layers of the gradient structure, and n≥2 is a natural number;

[0013] Step S3, prefabricating a W-layer two-dimensional fiber fabric preform capable of being shaped into a three-dimensional shape; W ≥ 1 and is a natural number;

[0014] Step S4: n ceramic matrix layers and W two-dimensional fiber fabric preforms are stacked layer by layer along the Z direction by 3D printing. When printing a certain layer of slices containing two-dimensional fiber fabrics, the two-dimensional fiber preforms are first accurately laid out in the corresponding order and positioned. Then, ceramic raw materials S1, S2, ... S are placed in m gradient zones, i.e., the first gradient zone, the second gradient zone ... the m-1 gradient zone, the m gradient zone. m-1 , S m ; Obtain the precursor of gradient porous ceramic matrix composite material product:

[0015] Step S5, degreasing and sintering the precursor.

[0016] Furthermore, the main steps of step S1 include: according to the number of layers n of the gradient structure, the composition of the ceramic matrix layer, and the content of each component in each ceramic matrix layer, the raw materials required for each ceramic matrix layer are mixed to obtain the ceramic raw materials S1, S2, ... S required for the first gradient layer, the second gradient layer ... the n-1 gradient layer, and the n gradient layer from the outer surface to the inside of the product. n-1 , S n , n≥2.

[0017] Furthermore, in step S1, the designable variables of the composition of the ceramic matrix layer include the type of ceramic powder, the particle size of the ceramic powder, and the type of resin.

[0018] Furthermore, in step S2, each layer of the two-dimensional fiber fabric covers a partial area or the entire area of ​​k adjacent ceramic matrix layers in the corresponding slice, 2≤k≤n.

[0019] Further, according to the additive manufacturing method of the gradient porous ceramic matrix composite product, the product is a radome, and the radome is a hemispherical shell;

[0020] In step S1, according to the radome having n layers of gradient structure with different densities from the outer surface to the inner surface, i.e., the first density layer, the second density layer ... the n-1th density layer, the nth density layer, and the components of the n density layers and the content ratio of each component in each density layer, a ceramic raw material required for each density layer is prepared;

[0021] In step S2, a three-dimensional model of the radome is established, and the axial direction of the radome is set to the Z direction of layer-by-layer stacking, and a slicing process is performed; wherein each layer of the annular two-dimensional fiber fabric is included in the corresponding slice; each layer of the slice includes a first density area, a second density area, ... an m-1th density area, an mth density area, from the outer surface to the inner surface of the radome, in sequence, 1≤m≤n;

[0022] In step S3, W circular two-dimensional fiber fabrics are prefabricated, the fiber arrangement direction of the circular two-dimensional fiber fabrics is mainly circumferential, and the circumferential fibers are connected by radial fibers to form an integral two-dimensional fiber fabric, and the W circular two-dimensional fiber fabrics are preformed into W circular ring-shaped two-dimensional fiber fabric preforms that can be shaped;

[0023] In step S4, a precursor of the antenna cover is obtained by selective photocuring or laser selective sintering: when printing a certain layer of slices containing two-dimensional fiber fabrics, firstly accurately lay out the corresponding order of circular two-dimensional fiber layer preforms, position them, and then lay or spray ceramic raw materials S1, S2, ... S in m density areas, i.e., the first density area, the second density area ... the m-1 density area, the m density area. m-1 , S m ;

[0024] Furthermore, the densities of the first density layer, the second density layer, ... the n-1th density layer, and the nth density layer of the antenna cover decrease successively from the outer surface to the inner surface.

[0025] Furthermore, in step S1, the components of the n density layers include a ceramic powder and a resin, and the ceramic raw materials S1, S2, ... S of the first density layer, the second density layer ... the n-1th density layer, the nth density layer from the outer surface to the inner surface of the antenna cover are n-1 , S n The content ratio of ceramic powder to resin decreases successively.

[0026] Furthermore, in step S1, the components of the n density layers include n kinds of ceramic powders with different particle sizes and a resin, and the ceramic raw materials S1, S2 ... n-1 , S n The particle size of the ceramic powder increases successively.

[0027] Furthermore, in step S4, the laser selective sintering method specifically includes the following steps:

[0028] Step S411: accurately placing and positioning the two-dimensional fiber fabric preform;

[0029] Step S412: laying or spraying ceramic raw materials in m density areas corresponding to the slice layer;

[0030] Step S413: Scan the current layer with laser to melt the resin in the ceramic raw materials of the m density zones from point to line, from line to surface, and cool and solidify, or melt and heat-cure, to complete the laser selective sintering of the current layer;

[0031] Step S414: the molding printing platform descends one layer and continues printing the next layer.

[0032] Repeat the above steps S411 to S414, or S412 to S414, until the last slice layer is printed.

[0033] Optionally, the types of ceramic powders include, but are not limited to, one or a combination of SiC ceramics, Si3N4 ceramics, Al2O3, SiO2, ZrO2, mullite, calcium aluminum silicate glass, lithium aluminum silicate glass, magnesium aluminum silicate glass, borate glass, and quartz glass.

[0034] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0035] (1) The present invention provides an additive manufacturing method for a gradient porous ceramic-based composite material, which utilizes 3D printing technology to realize the integrated molding of a "gradient porous ceramic matrix + fiber reinforcement phase" composite material, and realizes the precise control of the material composition and / or density of different gradient layers. Since the density distribution is closely related to the dielectric constant, the dielectric constant of different gradient layers is highly designable, and the thickness of different gradient layers and the composition and content of the ceramic raw materials required for each gradient layer can be adjusted to obtain the required gradient change of the dielectric constant, thereby better meeting the personalized needs of broadband wave transmission. Furthermore, a two-dimensional fiber fabric distributed layer by layer is designed along the 3D printing stacking direction, and the two-dimensional fiber fabric is used as a reinforcing phase to perform composite reinforcement on the gradient porous ceramic matrix, which can be used to quickly prepare a gradient porous ceramic-based composite material and its products that can take into account the properties of broadband wave transmission, lightweight, high strength, high temperature resistance, corrosion resistance, etc.

[0036] (2) The additive manufacturing method of the gradient porous ceramic matrix composite material proposed in the present invention designs the number of layers of the gradient structure, the composition of the ceramic matrix layer (for example, the type of ceramic powder, the particle size of the ceramic powder, the type of resin), the content of each component in each ceramic matrix layer (for example, the content ratio of ceramic powder and resin), and adjusts the parameters of the degreasing and sintering process. With the help of the additive manufacturing layer-by-layer stacking method, the density distribution and dielectric constant of different gradient layers are highly designable, thereby meeting different functional requirements (for example, broadband wave transmission performance).

[0037] (3) The additive manufacturing method of the gradient porous ceramic-based composite material proposed in the present invention can better meet the personalized requirements of the gradient ceramic material for mechanical properties by designing the number of layers, materials, thickness and fiber arrangement of the two-dimensional fiber fabric, the distribution of the two-dimensional fiber fabric in the ceramic matrix, etc., for the fiber reinforcement phase. That is, the mechanical properties of the composite material and its product prepared by the method provided by the present invention are highly designable.

[0038] (4) The additive manufacturing method of the gradient porous ceramic-based composite material proposed in the present invention integrates the "gradient porous ceramic matrix + fiber reinforcement phase" into an integrated form through 3D printing technology without the need for a mold. The method provided by the present invention is suitable for producing products of various complex shapes and structures. The product shape obtained by this method is highly designable and can better meet the personalized requirements for the shape and structure of gradient ceramics in different application scenarios.

[0039] (5) The additive manufacturing method of the gradient porous ceramic matrix composite material proposed in the present invention integrates the "gradient porous ceramic matrix + fiber reinforcement phase" into an integrated form through 3D printing technology. When printing each layer of slices, the nozzle of the 3D printer can accurately place the ceramic raw materials S1, S2...S according to the motion trajectory planned by the computer software. m-1 , Sm Placed at the preset positions of the m gradient zones contained in the corresponding layer slices, namely the first gradient zone, the second gradient zone...the m-1th gradient zone, and the mth gradient zone, compared with the method of using molds to form gradient ceramic products in the prior art, the method provided by the present invention does not require the use of molds, can accurately control the distribution of the gradient structure, and obtain a gradient structure with clear boundaries.

[0040] (6) The additive manufacturing method of the gradient porous ceramic-based composite material proposed in the present invention integrates the "gradient porous ceramic matrix + fiber reinforcement phase" into an integrated form through 3D printing technology, so that each layer of the gradient structure is tightly combined. Compared with the existing preparation technology (assembling structures of different densities together), the composite materials and products obtained by the method provided by the present invention have firm combinations of different layers of gradient structures and high reliability.

[0041] (7) The additive manufacturing method of gradient porous ceramic-based composite materials proposed in the present invention combines "gradient porous ceramic matrix + fiber reinforcement phase" by means of "prefabricated two-dimensional fiber fabric + additive manufacturing process", thereby realizing the rapid manufacturing of gradient porous ceramic structures. The density distribution and boundaries of the gradient ceramic structures can be precisely controlled, and the excellent properties such as good broadband wave transmission performance, mechanical strength, lightweight, high temperature resistance, and corrosion resistance can be taken into account. The functionality (for example: broadband wave transmission performance) and mechanical properties are highly designable. Therefore, the method has broad application prospects in the fields of aerospace, electronic information, etc. For example, it can be used to manufacture heat-resistant / broadband wave-transparent / lightweight and high-strength integrated radar antenna covers in the aerospace field, and the vertebral body of the front head of high-speed aircraft.

[0042] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0044] Figure 1 An axonometric view of a radome provided in an embodiment of the present invention;

[0045] Figure 2 An XZ cross-sectional schematic diagram of a radome provided in an embodiment of the present invention;

[0046] Figure 3 An XY cross-sectional schematic diagram of a radome provided in an embodiment of the present invention;

[0047] Figure 4 A schematic diagram of a two-dimensional fiber fabric included in a certain layer of slices of a radome provided in an embodiment of the present invention;

[0048] Reference numerals:

[0049] 101 - first density zone; 102 - second density zone; 201 - circular two-dimensional fiber fabric; A - first positioning point; B - second positioning point; C - third positioning point; D - fourth positioning point. DETAILED DESCRIPTION

[0050] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0051] The present invention provides an additive manufacturing method for a gradient porous ceramic-based composite material product, the additive manufacturing method comprising the following steps:

[0052] Step S1, preparing ceramic raw materials required for forming each ceramic matrix layer of a gradient structure along a gradient direction of the composite material;

[0053] Specifically, the main steps of step S1 include: according to the number of layers n of the gradient structure, the composition of the ceramic matrix layer, and the content of each component in each ceramic matrix layer, the raw materials required for each ceramic matrix layer are mixed to obtain the ceramic raw materials S1, S2, ... S required for the first gradient layer, the second gradient layer ... the n-1 gradient layer, the n gradient layer from the outer surface to the inside of the product. n-1 , S n , n ≥ 2 and is a natural number.

[0054] It should be noted that the number of layers n of the gradient structure can be selected according to actual needs, n ≥ 2 and is a natural number;

[0055] Furthermore, the density distribution of the gradient structure can be designed according to actual needs; the density distribution of the first gradient layer, the second gradient layer, ... the n-1 gradient layer, and the nth gradient layer from the outer surface of the product to the inside includes but is not limited to decreasing in sequence, increasing in sequence, first decreasing in sequence and then increasing in sequence, or first increasing in sequence and then decreasing in sequence.

[0056] Furthermore, the thickness distribution of the gradient structure can be designed according to actual needs; the thickness of the n ceramic substrate layers can be the same or different; preferably, the thickness of each ceramic substrate layer is the same.

[0057] It should be noted that the composition of the ceramic matrix layer can be selected according to actual needs; specifically, the composition of the ceramic matrix layer mainly includes ceramic powder, resin and other additives; commercially available ceramic powder, resin and other raw materials for 3D printing can be purchased.

[0058] It is understandable that the designable variables of the composition of the ceramic matrix layer include: the type of ceramic powder, the particle size of the ceramic powder, and the type of resin.

[0059] Optionally, the type of ceramic powder can be selected as needed, including but not limited to SiC ceramics, Si3N4 ceramics, Al2O3, SiO2, ZrO2, mullite, CAS (calcium aluminum silicate) glass, LAS (lithium aluminum silicate) glass, MAS (magnesium aluminum silicate) glass, BS (borate) glass, quartz glass, one or a combination of several of them.

[0060] Optionally, the particle size of the ceramic powder can be selected as needed. By adjusting and designing the particle size of the ceramic powder in each ceramic matrix layer, the density distribution of the gradient structure can be precisely controlled, thereby achieving the purpose of regulating the pore content and dielectric constant of the gradient structure to meet different usage requirements and application scenarios.

[0061] Optionally, the type of resin can be selected as needed, including but not limited to photosensitive resin, or resin that can be melted and bonded after being heated.

[0062] Illustratively, the photosensitive resin includes, but is not limited to, one or a combination of epoxy resin, epoxy acrylate, polyurethane acrylate resin, polyester acrylate resin, and amino acrylate resin.

[0063] Exemplarily, the resin powder that can melt and bond after being heated includes thermoplastic resins such as polystyrene, nylon, polycarbonate, polypropylene and wax powder, or thermosetting resins such as epoxy resin, unsaturated polyester, phenolic resin, amino resin, polyurethane, silicone resin and aromatic heterocyclic resin.

[0064] It should be noted that the content of each component in each ceramic matrix layer can be selected as needed. By adjusting and designing the content of each component in each ceramic matrix layer, the density distribution of the gradient structure can be accurately controlled, thereby achieving the purpose of regulating the pore content and dielectric constant of the gradient structure. For example, the greater the proportion of the resin component in the ceramic matrix layer, the higher the pore content and the lower the density left after the resin is volatilized and discharged after degreasing and sintering, thereby achieving the purpose of adjusting the dielectric constant to meet different usage requirements and application scenarios.

[0065] In one possible design, Figure 1As shown, the gradient porous ceramic-based composite material product is a hemispherical shell, the number of gradient structure layers n=2, the outer layer is a high-density area, and the inner layer is a low-density area; two ceramic raw materials S1 and S2 are prepared, and the gradient structure components include a ceramic powder X and a resin Y. The content ratio of ceramic powder X to resin Y in raw material S1 is K1, and the content ratio of ceramic powder X to resin Y in raw material S2 is K2, K1>K2, raw material S1 is used for the high-density area, and raw material S2 is used for the low-density area.

[0066] In one possible design, Figure 1 As shown, the gradient porous ceramic-based composite material product is a hemispherical shell, the number of gradient structure layers n is 2, the outer layer is a high-density area, and the inner layer is a low-density area; two ceramic raw materials S1 and S2 are prepared, and the gradient structure components include two ceramic powders X1 and X2 and a resin Y, X1 and X2 are the same ceramic powder but have different particle sizes, and the particle size of X1 is smaller than that of X2; raw material S1 includes ceramic powder X1 and resin Y, and the content ratio of the two is K3, raw material S2 includes ceramic powder X2 and resin Y, and the content ratio of the two is also K3; raw material S1 is used for the high-density area, and raw material S2 is used for the low-density area.

[0067] Step S2, establishing a three-dimensional model of a gradient porous ceramic-based composite material product, wherein the XY plane is the gradient direction, and the Z direction perpendicular to the XY plane is set as the layer-by-layer stacking direction, and slicing is performed; wherein each layer of the two-dimensional fiber fabric is contained in the corresponding slice; each layer of the slice includes m gradient regions from the outer surface to the inside of the product, namely, the first gradient region, the second gradient region...the m-1th gradient region, the mth gradient region, 1≤m≤n, n is the number of layers of the gradient structure, and n≥2 is a natural number;

[0068] Specifically, step S2 includes the following steps:

[0069] Step S21: using computer-aided design software to establish a three-dimensional model of a gradient porous ceramic matrix composite material product;

[0070] Specifically, a gradient porous ceramic matrix composite product includes a ceramic matrix and a reinforcement phase;

[0071] Along the gradient direction of the composite material product, the ceramic matrix includes n layers of ceramic matrix layers with different material compositions and / or densities to form a gradient structure, and the reinforcement phase includes W layers of two-dimensional fiber fabrics, which are distributed layer by layer along the Z direction perpendicular to the XY plane, and each layer of the two-dimensional fiber fabric is located inside an adjacent ceramic matrix layer;

[0072] It should be noted that the n ceramic base layers have similar shapes and structures.

[0073] In a possible design, the n ceramic substrate layers are all in the shape of flat plates, and adjacent ceramic substrate layers are stacked to form a gradient structure; the shape of the ceramic substrate is flat, and the structure of the ceramic substrate is a solid body.

[0074] In one possible design, n ceramic matrix layers are all three-dimensional in shape, and adjacent ceramic matrix layers are stacked to form a gradient structure; the stacking here can be understood as: n ceramic matrix layers with similar three-dimensional shapes are in a Russian nesting doll style, stacked one by one. The shape of the ceramic matrix can be a body of revolution, including but not limited to any one of a hemispherical, spherical, conical, truncated cone, cylindrical, or other three-dimensional shapes, including but not limited to any one of a tetrahedron, a triangular pyramid, and a quadrangular pyramid. The structure of the ceramic matrix can be a solid body or a hollow shell, wherein the hollow shell includes an open type or a closed type. Exemplarily, the open type is that the lower end face of the hollow shell is connected to the outside world.

[0075] Based on the shape and structure of the above-mentioned ceramic matrix, the structure of the gradient porous ceramic matrix composite material product is a solid body or a hollow shell, wherein the hollow shell includes an open type or a closed type; the shape of the gradient porous ceramic matrix composite material product includes but is not limited to any one of a flat plate, a hemispherical shape, a sphere, a cone, a truncated cone, a cylinder, a tetrahedron, a triangular pyramid, and a quadrangular pyramid.

[0076] It should be noted that the material composition of the n-layer ceramic substrate layer is different, including but not limited to the following possible designs:

[0077] In a possible design, each ceramic base layer is made of the same ceramic material, and the ceramic materials of the n ceramic base layers are not completely the same;

[0078] In a possible design, some of the n ceramic substrate layers are a combination of two or more ceramic materials, and each of the remaining ceramic substrate layers is made of the same ceramic material, and the ceramic materials of the n ceramic substrate layers are not completely the same.

[0079] It can be understood that for ceramic materials, density, pore content and dielectric constant are closely related. The density of n ceramic matrix layers is different, and the pore content and dielectric constant of the n ceramic matrix layers are also different. By adjusting the raw material formula of the ceramic matrix (for example: the particle size of the ceramic powder, the resin type, the content ratio of the ceramic powder to the resin), the density and / or void content and / or dielectric constant can be changed according to a certain rule along the gradient direction of the composite material.

[0080] It should be noted that the reinforcement phase includes W layers of two-dimensional fiber fabrics distributed layer by layer along the 3D printing stacking direction (ie, Z direction); specifically, the planes where the W layers of two-dimensional fiber fabrics are located are parallel to each other and perpendicular to the 3D printing stacking direction (ie, Z direction).

[0081] Optionally, W layers of two-dimensional fiber fabrics are evenly or non-uniformly distributed layer by layer in the ceramic matrix along the 3D printing stacking direction (ie, Z direction). Preferably, W layers of two-dimensional fiber fabrics are evenly distributed layer by layer in the ceramic matrix along the 3D printing stacking direction (ie, Z direction); W ≥ 1 and is a natural number.

[0082] Preferably, the thickness of the fiber-free ceramic matrix on the upper and lower surfaces of the gradient porous ceramic-based composite material product along the Z direction is not less than 0.1 mm; more preferably, the thickness of the fiber-free ceramic matrix on the upper and lower surfaces of the gradient porous ceramic-based composite material product along the Z direction is not less than 0.5 mm.

[0083] Preferably, the plane size of each layer of two-dimensional fiber fabric is 0.1 mm to 0.5 mm smaller than the plane size of the slice where the corresponding layer of two-dimensional fiber fabric is located.

[0084] Optionally, the material, thickness and fiber arrangement of the W layers of two-dimensional fiber fabric may be the same or different;

[0085] In a possible design, each layer of the two-dimensional fiber fabric has the same material, thickness, and fiber arrangement.

[0086] In one possible design, each layer of the two-dimensional fiber fabric has the same material and thickness, but the fiber arrangement is different.

[0087] Step S22: converting the three-dimensional model of the gradient porous ceramic matrix composite material product into an STL triangulated file, setting the Z direction perpendicular to the XY plane as the layer-by-layer stacking direction, and slicing the STL triangulated file.

[0088] It should be noted that, according to the number of layers n of the gradient structure, correspondingly, each slice includes m gradient zones from the outer surface to the inside of the product, namely, the first gradient zone, the second gradient zone, ... the m-1th gradient zone, the mth gradient zone, 1≤m≤n, and n is the number of layers of the gradient structure;

[0089] For example, Figure 1 As shown, the gradient porous ceramic-based composite material product is a hemispherical shell, and the number of layers n of the gradient structure of the hemispherical shell is 2. Correspondingly, the value of m is 1 or 2. From bottom to top along the Z direction shown in the figure, most of the slices include the first gradient zone 101 and the second gradient zone 102, and only some slices close to the highest point of the hemispherical shell only include the first gradient zone 101.

[0090] In one possible design, the gradient porous ceramic-based composite material product is in the shape of a body of revolution, with the central axis of the body of revolution as the layer-by-layer stacking direction of 3D printing, i.e., the Z direction, and the plane perpendicular to the Z direction, i.e., the XY plane, as the base plane of 3D printing. After slicing, each layer of the slice has a circular or circular gradient structure.

[0091] For example, Figure 2 and Figure 3 As shown, for a hemispherical shell with an open lower portion, the axial direction of the hemispherical shell (i.e., a straight line passing through the center of the sphere and perpendicular to the diameter) is used as the Z direction, and the plane perpendicular to the Z direction is used as the base plane of 3D printing (i.e., the XY plane). After slicing, each layer of slices presents multiple annular or circular gradient structures. In this embodiment, along the Z direction shown in the figure from bottom to top, each of the majority of slices includes a first gradient zone 101 and a second gradient zone 102 in the form of an annular shape, and only some slices close to the highest point of the hemispherical shell include a first gradient zone 101 and a second gradient zone 102 in the form of a circular shape, or only include a first gradient zone 101 in the form of a circular shape.

[0092] Optionally, for shapes such as spheres, after converting the 3D model to an STL file, you can generate supports at the bottom of the 3D model or at a location with a large slope through the software, and then slice the 3D model and the supports and import them into the 3D printing system control host. The supports here are mainly temporary structures added to maintain the shape and stability of the printed object, and can be easily removed after printing.

[0093] It is worth noting that due to the adoption of the gradient structure, the mechanical properties of the structure will be reduced in the low-density area of ​​the ceramic matrix layer. In order to compensate for the reduction in mechanical properties, according to actual needs, a two-dimensional fiber fabric can be designed in the corresponding slice as a reinforcing phase, which can effectively improve the mechanical properties of the product. Compared with the prior art of compensating for the mechanical properties of the low-density area by increasing the thickness, the present invention combines the "gradient porous ceramic matrix + fiber reinforcement phase" through additive manufacturing to minimize the structural weight and improve the mechanical properties of the product. This is of great significance for some special fields such as aerospace, where both lightweight and high performance products are required.

[0094] It should be noted that the number of slices comprising the two-dimensional fiber fabric is P, P≥1 and is a natural number; the number of layers of the two-dimensional fiber fabric is W, W≥1 and is a natural number.

[0095] Preferably, P=W, that is, W layers of two-dimensional fiber fabrics are respectively contained in corresponding W slices.

[0096] Preferably, each layer of the two-dimensional fiber fabric covers a partial area or the entire area of ​​k adjacent ceramic matrix layers in the corresponding slice, 2≤k≤n;

[0097] For example, the gradient porous ceramic matrix composite material product comprises three ceramic matrix layers from the outer surface to the inside, namely, the first gradient layer, the second gradient layer, and the third gradient layer (i.e., n=3), and the reinforcement phase comprises a layer of two-dimensional fiber fabric (i.e., W=1), including but not limited to the following possible designs:

[0098] In a possible design, this layer of two-dimensional fiber fabric covers partial areas of the adjacent first gradient layer and the second gradient layer;

[0099] In a possible design, this layer of two-dimensional fiber fabric covers the entire area in the adjacent first gradient layer and the second gradient layer;

[0100] In a possible design, this layer of two-dimensional fiber fabric covers a portion of the adjacent second gradient layer and third gradient layer;

[0101] In one possible design, this layer of two-dimensional fiber fabric covers the entire area in the adjacent second gradient layer and third gradient layer;

[0102] In a possible design, the layer of two-dimensional fiber fabric covers a portion of the adjacent first gradient layer, the second gradient layer, and the third gradient layer;

[0103] In a possible design, this layer of two-dimensional fiber fabric covers the entire area of ​​the adjacent first gradient layer, the second gradient layer and the third gradient layer.

[0104] It should be noted that when slicing, each layer of two-dimensional fiber fabric is contained in the corresponding slice, that is, the ceramic matrix of each slice thickness completely wraps the two-dimensional fiber fabric of this layer, so that the surface is flat after laying each layer of ceramic matrix material to ensure smooth subsequent printing operations, for example, the scraper motion system can move smoothly to lay each layer of printing material;

[0105] In order to meet the above requirements, the slice thickness is greater than the thickness of the two-dimensional fiber fabric; optionally, the thickness of the W layers of two-dimensional fiber fabric can be the same or different, and the maximum thickness in the two-dimensional fiber fabric is set as M1, satisfying N>M1, N is the slice thickness, and M1 is the maximum thickness in the two-dimensional fiber fabric. Optionally, N is 0.025mm~0.5mm; preferably, N is 0.05mm~0.1mm; illustratively, M1=0.08mm, N=0.1mm.

[0106] It should be noted that the first and last layers of the slice are ceramic matrix materials that do not contain fibers, satisfying N<S, where N is the slice thickness, and S is the thickness of the fiber-free ceramic matrix on the upper and lower surfaces of the gradient porous ceramic-based composite material product along the Z direction; optionally, N is 0.025mm~0.5mm; preferably, N is 0.05mm~0.1mm; exemplarily, S=0.6mm, N=0.1mm.

[0107] It can be seen that the slice thickness N is selected based on the thickness of the two-dimensional fiber fabric and the thickness of the fiber-free ceramic matrix on the upper and lower surfaces of the product along the Z direction, ensuring that each layer of the two-dimensional fiber fabric is contained in the corresponding slice, and the first and last layers of the slice are fiber-free ceramic matrix materials to ensure the smooth progress of subsequent printing operations, and that the fiber fabric can be fully covered in the product's shape after molding, ensuring that the product surface is completely flat.

[0108] Optionally, computer-aided design (CAD) software can be selected as needed, including but not limited to AutoCAD, Autodesk Inventor, SolidWorks, CATIA, Pro / E, UG NX, SolidEdge, Onespace, etc.

[0109] Step S3, prefabricating a W-layer two-dimensional fiber fabric preform capable of being shaped into a three-dimensional shape, where W ≥ 1 and is a natural number;

[0110] The specific steps include:

[0111] Step S31: preparing a two-dimensional fiber fabric by weaving;

[0112] Specifically, a plurality of fiber bundles are regularly interlocked alternately by weaving to form a two-dimensional fiber fabric. The weaving method of the two-dimensional fiber fabric can be selected according to needs, including but not limited to weaving, braiding, knitting, etc.

[0113] Preferably, the two-dimensional fiber fabric is woven from continuous fibers.

[0114] It should be noted that the diameter of the fiber bundle used to prepare the two-dimensional fiber fabric is determined according to the slice thickness in step S1 to satisfy N>M1, where N is the slice thickness and M1 is the maximum thickness of the two-dimensional fiber fabric.

[0115] In a possible design, the slice thickness N is 0.05mm~0.1mm. To satisfy N>M1, preferably, the two-dimensional fiber fabric is woven from ultra-small tow continuous fibers, where the ultra-small tow is less than or equal to 1K fiber, 1K means that a bundle of fiber contains 1000 single fibers; more preferably, the two-dimensional fiber fabric is woven from 0.1K~0.8K ultra-small tow continuous fibers.

[0116] For example, the slice thickness N=0.1 mm, the fiber bundle is 0.12K (each bundle has 120 fiber filaments), and the diameter of the filament is 8 μm, which can ensure that the thickness of the prepared two-dimensional fiber fabric is less than 0.1 mm.

[0117] Optionally, the fiber type for preparing the two-dimensional fiber fabric can be selected as needed, including but not limited to one or a combination of silicon carbide fiber, carbon fiber, silicon nitride fiber, boron fiber, basalt fiber, glass fiber, aramid fiber, and alumina (including mullite) fiber.

[0118] It should be noted that the fiber arrangement of the two-dimensional fiber fabric can be selected according to needs (for example, the force direction of the product, etc.), including but not limited to hoop cloth, plain cloth, twill cloth, etc. For example, Figure 4 The circumferential fabric is a fabric in which the fibers are arranged mainly in the circumferential direction. The function of the radial fibers is mainly to connect the circumferential fibers together to form an integral two-dimensional fiber fabric. This is mainly because the circumferential direction is the main force direction of the hemispherical shell.

[0119] Step S32: The two-dimensional fiber fabric is fully infiltrated with a liquid of a thermoplastic or thermosetting resin by a prepreg method and then shaped to form a two-dimensional fiber fabric preform that can be shaped so as to maintain the existing shape when picked up and placed.

[0120] It should be noted that thermosetting resins are resins that are liquid at room temperature but can be cross-linked and cured under heating or light, including high-temperature curing resins or photosensitive resins.

[0121] Optionally, the thermosetting resin can be selected as needed, including but not limited to epoxy resin, epoxy acrylate, polyurethane acrylate resin, polyester acrylate resin, and amino acrylate resin.

[0122] Optionally, the type of thermoplastic resin can be selected as needed, including but not limited to acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polylactic acid (PLA), polyetheretherketone (PEEK), polyethylene terephthalate-1,4-cyclohexadiene dimethylene terephthalate (PETG), high-density polyethylene (HDPE), polystyrene (PS), etc.

[0123] Preferably, the type of resin used to impregnate the two-dimensional fiber fabric in the prepreg method is the same as or similar to the type of resin in the ceramic raw material configured in step S1.

[0124] It should be noted that the prepreg method includes the spray rolling prepreg method and the glue tank rolling prepreg method.

[0125] As an optional embodiment, the main steps of the spray-roll prepreg method include: spraying thermosetting resin liquid on the surface of the two-dimensional fiber fabric, fully infiltrating, combining and compacting the two-dimensional fiber fabric and the resin liquid through a rolling method, and shaping through low-temperature precuring or light precuring to obtain a two-dimensional fiber fabric preform.

[0126] As an optional implementation, the main steps of the glue tank rolling prepreg method include: immersing the two-dimensional fiber fabric in a glue tank containing thermosetting resin liquid, fully impregnating and compacting the two-dimensional fiber fabric and the resin liquid through rolling, and shaping it through low-temperature precuring or light precuring to obtain a two-dimensional fiber fabric preform.

[0127] It should be noted that, for thermosetting resins, the main steps of the above-mentioned rolling method include: squeezing the two-dimensional fiber fabric that is fully soaked in the thermosetting resin liquid by a pair of rotating pressure rollers, and at the same time, heating the pressure rollers to achieve low-temperature pre-curing, or irradiating the two-dimensional fiber fabric passing through the pressure rollers with ultraviolet light or laser to achieve light pre-curing.

[0128] As an optional implementation, the main steps of the spray rolling prepreg method include: spraying thermoplastic resin liquid on the surface of the two-dimensional fiber fabric, fully infiltrating, combining and compacting the two-dimensional fiber fabric and the resin liquid through rolling, cooling at room temperature for shaping, and obtaining a two-dimensional fiber fabric preform.

[0129] As an optional implementation, the main steps of the glue tank rolling prepreg method include: immersing the two-dimensional fiber fabric in a glue tank containing thermoplastic resin liquid, fully impregnating and compacting the two-dimensional fiber fabric and the resin liquid through rolling, cooling at room temperature for shaping, and obtaining a two-dimensional fiber fabric preform.

[0130] It should be noted that for thermoplastic resins, the main steps of the above rolling method include: using a pair of rotating rollers to extrude the two-dimensional fiber fabric that is fully soaked in the thermoplastic resin liquid, and cooling the two-dimensional fiber fabric that has passed through the rollers at room temperature and shaping it.

[0131] In a possible design, a high-temperature curing resin is sprayed on the surface of the two-dimensional fiber fabric, and the pressure roller can be heated in the rolling method to pre-cure the resin on the surface of the two-dimensional fiber fabric passing through the pressure roller at a low temperature, thereby achieving the shaping of the two-dimensional fiber fabric. Exemplarily, the high-temperature curing resin is selected as epoxy resin, and the curing temperature of the epoxy resin is 120°C. The pre-impregnated two-dimensional fiber fabric is pre-cured at a low temperature by a pressure roller preheated to 60°C to become a two-dimensional fiber fabric preform with a certain shape and stiffness.

[0132] In a possible design, the two-dimensional fiber fabric is immersed in a glue tank containing a photosensitive resin liquid, and a certain amount of ultraviolet light or laser can be irradiated to the material passing through the pressure roller in the rolling method, and the photosensitive resin on the surface of the two-dimensional fiber fabric is photo-precured under the action of the laser or ultraviolet light, thereby achieving the shaping of the two-dimensional fiber fabric. Exemplarily, the photosensitive resin is selected as epoxy acrylate, and the two-dimensional fiber fabric pre-impregnated with epoxy acrylate passes through a pair of rotating pressure rollers, and an ultraviolet solid laser is used to irradiate the material passing between the pressure rollers, so that the epoxy acrylate sprayed on the surface of the two-dimensional fiber fabric is photo-precured to become a two-dimensional fiber fabric preform with a certain shape and rigidity.

[0133] It should be noted that in order to ensure the smooth progress of 3D printing, the thickness of the two-dimensional fiber preform is less than the slice thickness, satisfying M1≤M2<N, M1 is the maximum thickness of the two-dimensional fiber fabric, M2 is the maximum thickness of the two-dimensional fiber preform, and N is the slice thickness; optionally, N is 0.025mm~0.5mm; preferably, N is 0.05mm~0.1mm.

[0134] It is worth noting that the two-dimensional fiber fabric preform obtained by pre-preg method has good rigidity and can maintain the existing shape of the two-dimensional fiber fabric during the pick-up and placement operations. At the same time, the pre-preg method makes the two-dimensional fiber fabric and the resin fully infiltrated and shaped, which can well maintain the uniformity, stability, integrity and consistency of the two-dimensional fiber fabric in the subsequent 3D printing process and the final product.

[0135] Step S33: Processing the two-dimensional fiber fabric preform into a two-dimensional fiber fabric preform of a required shape, and stacking them in the order of slicing and printing for later use.

[0136] Specifically, the two-dimensional fiber fabric preform is processed into a two-dimensional fiber fabric preform of a desired shape by a cutting process, and the number of layers and the outer contour of the two-dimensional fiber fabric preform are determined according to the two-dimensional fiber fabric in the three-dimensional model of the gradient porous ceramic matrix composite material product established in step S1. For example, Figures 1 to 4 The three-dimensional model is a hemispherical shell containing two layers of gradient structure. If four layers of two-dimensional fiber fabric are set at the 200th, 300th, 400th and 500th layers respectively, then four circular two-dimensional fiber fabric preforms are cut out according to the outer contour of the corresponding slice layer. The outer contour of each circular two-dimensional fiber fabric preform is slightly smaller than the outer contour of the corresponding slice layer to ensure that no fiber is exposed on the product surface after molding.

[0137] Optionally, the cutting process can be selected as needed, including but not limited to automatic cutting, laser cutting, etc. Exemplarily, the automatic cutting method can use a CNC cutting machine to cut the two-dimensional fiber fabric preform to obtain a two-dimensional fiber fabric preform of a desired shape.

[0138] Step S4: n layers of ceramic matrix layers and W layers of two-dimensional fiber fabric preforms are stacked layer by layer along the Z direction by 3D printing. When printing a certain layer of slices containing two-dimensional fiber fabrics, the two-dimensional fiber fabric preforms are first accurately laid out in the corresponding order and positioned. Then, ceramic raw materials S1, S2, ... S are placed in m gradient zones, i.e., the first gradient zone, the second gradient zone ... the m-1 gradient zone, the m gradient zone. m-1 , S m ; Obtain the precursor of gradient porous ceramic matrix composite material product:

[0139] It should be noted that the main steps of accurately laying out the two-dimensional fiber fabric preforms in the corresponding order include: before laying out or spraying a layer of sliced ​​ceramic raw materials, accurately locating the placement position of the two-dimensional fiber fabric preforms of the corresponding layer of the ceramic raw materials to be sprayed by infrared scanning, and laying them on the printed previous layer. Exemplarily, before laying out or spraying a layer of sliced ​​ceramic raw materials, the two-dimensional fiber fabric preforms of the corresponding layer are automatically picked up by a robot, and the placement position of the two-dimensional fiber fabric preforms of the corresponding layer of the ceramic raw materials to be sprayed is accurately located by infrared scanning, and laid on the printed previous layer.

[0140] It should be noted that the main steps of the positioning include: after accurately placing the two-dimensional fiber fabric preform of the corresponding layer, selecting W positioning points on the two-dimensional fiber fabric preform, and scanning the positioning points with laser or ultraviolet light to perform melting positioning (the thermoplastic resin at the positioning point is melted by heat and solidified by cooling) or heat curing positioning (the thermosetting resin at the positioning point is heat cured) or photocuring positioning (the photosensitive resin at the positioning point is photocured under the action of light), similar to the mechanism of metal spot welding, so that the two-dimensional fiber fabric preform is fixed on the printed previous layer to ensure that the two-dimensional fiber fabric preform will not move when the corresponding layer of matrix material is placed later.

[0141] Preferably, the number of positioning points W is ≥ 3, and they are not on a straight line to better ensure effective positioning.

[0142] It should be noted that the main steps of laying or spraying ceramic raw materials in the m density zones include: based on the number of layers n of the gradient structure in step S1 and the n types of ceramic raw materials S1, S2, ..., S2 prepared for each ceramic matrix layer; n-1 , S n, combined with each layer of slices determined in step S2, from the outer surface to the inside of the product, it includes the first gradient zone, the second gradient zone...the m-1 gradient zone, the m gradient zone, 1≤m≤n, n is the number of layers of the gradient structure, and the ceramic raw material S1 is laid or sprayed in the first gradient zone, the ceramic raw material S2 is laid or sprayed in the second gradient zone, and the ceramic raw material S is laid or sprayed in the m-1 gradient zone. m-1 , lay or spray ceramic raw material S in the mth gradient zone m The order of laying or spraying the m gradient zones in each slice layer can be selected as needed, preferably, from the outer layer to the inner layer, or from the inner layer to the outer layer.

[0143] It should be noted that the 3D printing method includes selective photo-stereolithography and laser selective sintering.

[0144] As an optional implementation, 3D printing is performed using a selective photopolymerization method to obtain a precursor of a gradient porous ceramic-based composite material product, including the following steps:

[0145] Step S401: accurately placing and positioning the two-dimensional fiber fabric preform;

[0146] When printing a certain layer of slices containing fibers, the robot automatically picks up the two-dimensional fiber fabric preform of the current layer and accurately positions and places it through infrared scanning. After placing the two-dimensional fiber fabric preform of the current layer, ultraviolet light is used to scan W points on the two-dimensional fiber fabric preform for light curing positioning;

[0147] Preferably, W ≥ 3 and are not on a straight line to ensure effective positioning.

[0148] Step S402: laying or spraying ceramic raw materials in m gradient areas;

[0149] The ceramic raw material is laid or sprayed in the m gradient areas of the corresponding layer through the nozzle of the 3D printer, that is, the ceramic raw material S1 is laid or sprayed in the first gradient area, the ceramic raw material S2 is laid or sprayed in the second gradient area, and the ceramic raw material S is laid or sprayed in the m-1 gradient area. m-1 , lay or spray ceramic raw material S in the mth gradient zone m , until all the ceramic raw materials in the m gradient zones of the corresponding layer are laid or sprayed.

[0150] Step S403: Scan the slice of the current layer with ultraviolet light to solidify it sequentially from point to line and from line to surface, thus completing the light curing of the current layer;

[0151] Step S404: the molding printing platform descends one layer and continues printing the next layer.

[0152] It can be understood that ultraviolet light is used to scan the current layer of slices, so that they are solidified in sequence from point to line and from line to surface, thereby completing the selective photocuring of the current layer; the principle of the selective photocuring is: the ceramic raw materials include ceramic powder and photosensitive resin, the liquid photosensitive resin of which can rapidly undergo photocuring reaction under the irradiation of ultraviolet light of a certain wavelength and intensity, and the molecular weight of the resin increases rapidly, thereby transforming the current layer of material from liquid to solid.

[0153] It should be noted that when printing slices containing two-dimensional fiber fabrics, 3D printing is performed according to steps S401 to S404; when printing slices that do not contain two-dimensional fiber fabrics, 3D printing is performed according to steps S402 to S404, and the above steps are repeated until the last layer of slices is printed to obtain a precursor of a gradient porous ceramic-based composite material product.

[0154] As an optional implementation, 3D printing is performed by laser selective sintering to obtain a precursor of a gradient porous ceramic-based composite material product, including the following steps:

[0155] Step S411: accurately placing and positioning the two-dimensional fiber fabric preform;

[0156] When printing a certain layer of slices containing fibers, the robot automatically picks up the two-dimensional fiber fabric preform of the current layer and accurately positions and places it through infrared scanning. After placing the two-dimensional fiber fabric preform of the current layer, laser scanning is used to scan W points on the two-dimensional fiber fabric preform for melting positioning or thermal curing positioning;

[0157] Preferably, W ≥ 3 and are not on a straight line to ensure effective positioning.

[0158] Step S412: laying or spraying ceramic raw materials in m gradient areas;

[0159] The ceramic raw material is laid or sprayed in the m gradient areas of the corresponding layer through the nozzle of the 3D printer, that is, the ceramic raw material S1 is laid or sprayed in the first gradient area, the ceramic raw material S2 is laid or sprayed in the second gradient area, and the ceramic raw material S is laid or sprayed in the m-1 gradient area. m-1 , lay or spray ceramic raw material S in the mth gradient zone m , until all the ceramic raw materials in the m gradient zones of the corresponding layer are laid or sprayed.

[0160] Step S413: Scan the current layer with laser to solidify it, so that it solidifies from point to line and from line to surface in sequence, thus completing the laser selective sintering of the current layer;

[0161] Step S414: the molding printing platform descends one layer and continues printing the next layer.

[0162] It can be understood that an infrared laser is used to scan the current layer of slices, so that they solidify sequentially from point to line and from line to surface, thereby completing the laser selective sintering of the current layer; the principle of the laser selective sintering is as follows: the ceramic raw materials include ceramic powder and resin powder, wherein the resin powder can be thermoplastic resin powder or thermosetting resin powder, the thermoplastic resin melts under the irradiation of high-intensity laser and cools and solidifies to bond the ceramic powder together to form a ceramic precursor, or the thermosetting resin powder melts and undergoes a thermal curing reaction under the irradiation of high-intensity laser, and after curing, the ceramic powder is bonded together to form a ceramic precursor.

[0163] It should be noted that when printing slices containing two-dimensional fiber fabrics, 3D printing is performed according to steps S411 to S414; when printing slices that do not contain two-dimensional fiber fabrics, 3D printing is performed according to steps S412 to S414, and the above steps are repeated until the last layer of slices is printed to obtain a precursor of a gradient porous ceramic-based composite material product.

[0164] Step S5, degreasing and sintering the precursor;

[0165] Specifically, the precursor of the gradient porous ceramic-based composite material product obtained in step S4 is degreased and sintered;

[0166] Degreasing: The precursor of the gradient porous ceramic-based composite material product is placed in a degreasing furnace, in which the resin in the precursor and the resin pre-impregnated in the two-dimensional fiber fabric in step S3 are slowly and completely discharged, and the resin is completely volatilized under high temperature to form pores, thereby obtaining a porous ceramic structure.

[0167] Sintering: Place the powder in a high-temperature sintering furnace for sintering. The ceramic powder is melted and bonded together. After sintering to a dense consistency, the final gradient porous ceramic-based composite material product is obtained.

[0168] In a possible design, debinding and sintering can be performed in the same furnace, and debinding can be performed first and then sintering by controlling parameters such as temperature and heating rate.

[0169] It should be noted that the sintering process can be pressureless sintering or isostatic sintering; by adjusting the parameters of the sintering process (mainly pressure and temperature), gradient ceramic structures of different densities can be obtained. Specifically, the density of the sintered product generally depends on the size of the pressure and the temperature. The greater the pressure and the higher the temperature, the higher the density. Pressureless sintering has no pressure, and the product density is lower than that of isostatic sintering. Furthermore, different densities correspond to different densities, and different densities correspond to different pore contents and dielectric constants. Therefore, by adjusting the sintering process, process parameters, etc., the density distribution of the gradient structure can be controlled, thereby achieving the purpose of regulating the pore content and dielectric constant of the gradient structure to meet different usage requirements and application scenarios.

[0170] The specific process parameters of debinding and sintering can be selected and set from the process parameters of debinding and sintering of ceramic materials in the prior art.

[0171] According to the above-mentioned additive manufacturing method of the gradient porous ceramic-based composite material product, the product is a radome, and the radome is a hemispherical shell;

[0172] In step S1, according to the fact that the antenna cover has n layers of ceramic base layers with different densities from the outer surface to the inner surface, a gradient structure is formed, namely, the first density layer, the second density layer ... the n-1th density layer, the nth density layer, and the components of the n density layers and the content ratio of each component in each density layer, the ceramic raw material required for each density layer is prepared, and n≥2;

[0173] In step S2, a three-dimensional model of the radome is established, the axial direction of the radome is set to the Z direction of layer-by-layer stacking, and a slicing process is performed; wherein each layer of the annular two-dimensional fiber fabric is contained in the corresponding slice; each layer of the slice includes a first density area, a second density area, ... an m-1th density area, an mth density area, from the outer surface to the inner surface of the radome, in sequence, 1≤m≤n;

[0174] In step S3, W circular two-dimensional fiber fabrics are prefabricated, wherein the fiber arrangement direction of the circular two-dimensional fiber fabrics is mainly circumferential, and the circumferential fibers are connected by radial fibers to form an integral two-dimensional fiber fabric, and the W circular two-dimensional fiber fabrics are preformed into W circular ring-shaped two-dimensional fiber fabric preforms that can be shaped;

[0175] In step S4, a precursor of the antenna cover is obtained by selective photocuring or laser selective sintering: when printing a certain layer of slices containing two-dimensional fiber fabrics, firstly accurately lay out the corresponding order of circular two-dimensional fiber fabric preforms, position them, and then lay or spray ceramic raw materials S1, S2, ... S in m density areas, i.e., the first density area, the second density area ... the m-1 density area, the m density area. m-1 , S m .

[0176] In a possible design, the densities of the first density layer, the second density layer, ... the n-1th density layer, and the nth density layer of the antenna cover decrease successively from the outer surface to the inner surface.

[0177] In a possible design, the components of the n density layers include a ceramic powder and a resin, and the ceramic raw materials S1, S2, ... S of the first density layer, the second density layer ... the n-1 density layer, the n density layer from the outer surface to the inner surface of the antenna cover are n-1 , S n The content ratio of ceramic powder to resin decreases successively.

[0178] In a possible design, the components of the n density layers include n kinds of ceramic powders with different particle sizes and a resin, and the ceramic raw materials S1, S2, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16, S17, S18, S19, S20, S21, S22, S30, S31, S32, S33, S34, S35, S36, S37, S38, S39, S40, S41, S42, S43, S44, S45, S46, S47, S48, S49, S50, S51, S52, S53, S54, S55, S56, S57, S58, S59, S60, S61, S62, S63, S64, S n-1 , S n The particle size of the ceramic powder increases successively.

[0179] As an optional implementation, a 3D printing method is used to obtain a precursor of the antenna cover by using a selective photo-stereolithography method, and the selective photo-stereolithography method specifically includes the following steps:

[0180] Step S401: accurately placing and positioning the two-dimensional fiber fabric preform;

[0181] When printing a certain layer of slices containing fibers, the robot automatically picks up the two-dimensional fiber fabric preform of the current layer and accurately positions and places it through infrared scanning. After placing the two-dimensional fiber fabric preform of the current layer, ultraviolet light is used to scan W points on the two-dimensional fiber fabric preform for light curing positioning;

[0182] Preferably, W ≥ 3 and are not on a straight line to ensure effective positioning.

[0183] Step S402: laying or spraying ceramic raw materials in m density areas corresponding to the slice layer;

[0184] The ceramic raw material is laid or sprayed in the m density areas of the corresponding layer through the nozzle of the 3D printer, that is, the ceramic raw material S1 is laid or sprayed in the first density area, the ceramic raw material S2 is laid or sprayed in the second density area, and the ceramic raw material S is laid or sprayed in the m-1th density area. m-1 , lay or spray ceramic raw material S in the mth density zone m , until all the ceramic raw materials in the m density zones of the corresponding layer are laid or sprayed.

[0185] Step S403: Scan the current slice layer with ultraviolet light to make the resin in the ceramic raw material of the m density zones undergo photocuring reaction from point to line and from line to surface in sequence, thus completing the photocuring of the current layer;

[0186] Step S404: the molding printing platform descends one layer and continues printing the next layer.

[0187] It should be noted that when printing slices containing two-dimensional fiber fabrics, 3D printing is performed according to steps S401 to S404; when printing slices that do not contain two-dimensional fiber fabrics, 3D printing is performed according to steps S402 to S404, and the above steps are repeated until the last layer of slices is printed to obtain the precursor of the antenna cover.

[0188] As an optional implementation, a laser selective sintering method is used for 3D printing to obtain a precursor of the antenna cover, and the laser selective sintering method specifically includes the following steps:

[0189] Step S411: accurately placing and positioning the two-dimensional fiber fabric preform;

[0190] When printing a certain layer of slices containing fibers, the robot automatically picks up the two-dimensional fiber fabric preform of the current layer and accurately positions and places it through infrared scanning. After placing the two-dimensional fiber fabric preform of the current layer, laser scanning is used to scan W points on the two-dimensional fiber fabric preform for melting positioning or thermal curing positioning;

[0191] Preferably, W ≥ 3 and are not on a straight line to ensure effective positioning.

[0192] Step S412: laying or spraying ceramic raw materials in m density areas corresponding to the slice layer;

[0193] The ceramic raw material is laid or sprayed in the m density areas of the corresponding layer through the nozzle of the 3D printer, that is, the ceramic raw material S1 is laid or sprayed in the first density area, the ceramic raw material S2 is laid or sprayed in the second density area, and the ceramic raw material S is laid or sprayed in the m-1th density area. m-1 , lay or spray ceramic raw material S in the mth density zone m , until all the ceramic raw materials in the m density zones of the corresponding layer are laid or sprayed.

[0194] Step S413: Scanning the current layer with laser for curing, so that the resin in the ceramic raw materials of the m density zones is sequentially melted from point to line, from line to surface, and cooled and solidified, or melted and thermally cured, to complete the laser selective sintering of the current layer;

[0195] Step S414: the molding printing platform descends one layer and continues printing the next layer.

[0196] It should be noted that when printing slices containing two-dimensional fiber fabrics, 3D printing is performed according to steps S411 to S414; when printing slices that do not contain two-dimensional fiber fabrics, 3D printing is performed according to steps S412 to S414, and the above steps are repeated until the last layer of slices is printed to obtain the precursor of the antenna cover.

[0197] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments.

[0198] Embodiment 1:

[0199] This embodiment provides an additive manufacturing method for a gradient porous ceramic-based composite antenna cover.

[0200] like Figure 1 As shown, the antenna cover is a hemispherical shell, including two inner and outer layers of ceramic matrix layers with different densities formed by 3D printing and 200 layers of annular two-dimensional fiber fabrics, the outer layer (i.e., the first density zone 101) is a high-density zone; the thickness of the outer layer is 8 mm; the inner layer (i.e., the second density zone 102) is a low-density zone, and the thickness of the inner layer is 8 mm; the outer diameter of the lower opening of the hemispherical shell is 400 mm, and the height of the hemispherical shell is 200 mm; along the central axis of the hemispherical shell, i.e., the Z direction, the two layers of ceramic matrix layers and the 200 layers of annular two-dimensional fiber fabrics are stacked layer by layer by 3D printing, the 200 layers of annular two-dimensional fiber fabrics are parallel to each other and are evenly distributed layer by layer along the XY plane perpendicular to the Z direction, and the two-dimensional fiber fabrics are completely coated inside the ceramic matrix; the thickness of each layer of two-dimensional fiber fabric is less than 0.1 mm, and the plane size of each layer of two-dimensional fiber fabric is 0.2 mm smaller than the plane size of the slice where the corresponding layer of two-dimensional fiber fabric is located.

[0201] The additive manufacturing method of the radome comprises the following steps:

[0202] Step S1, preparing ceramic raw materials required for each ceramic base layer;

[0203] In this embodiment, the number of layers of the gradient structure is n=2, the outer layer (ie, the first density region 101 ) is a high-density region, and the inner layer (ie, the second density region 102 ) is a low-density region.

[0204] Gradient structure components: including a ceramic powder (ie, silicon nitride powder with an average particle size of 50 μm) and an epoxy resin (ie, epoxy resin liquid with a weight average molecular weight of 500).

[0205] The content of each component in each layer of the gradient structure: the first density area 101 includes 80wt% of silicon nitride powder and 20wt% of epoxy resin; the second density area 102 includes 75wt% of silicon nitride powder and 25wt% of epoxy resin;

[0206] According to the above content ratio, the silicon nitride powder and the epoxy resin are fully mixed to obtain the ceramic raw materials S1 and S2 required for the first density area 101 and the second density area 102;

[0207] Step S2, using UG (Unigraphics NX) software to establish a three-dimensional model of the radome; then converting the three-dimensional model into an STL triangulated file required by the additive manufacturing system, slicing the STL triangulated file, and realizing the conversion of the three-dimensional model into a two-dimensional thin film model.

[0208] like Figure 2 and Figure 3 The radome is a hemispherical shell with an open bottom. The symmetry axis of the hemispherical shell (i.e., a straight line passing through the center of the sphere and perpendicular to the diameter) is used as the Z direction, and the plane perpendicular to the Z direction is used as the base plane of 3D printing (i.e., the XY plane). The slice thickness is 0.1 mm. After slicing, the Z direction is from bottom to top, such as Figure 3 As shown, each of most slices includes annular first density zone 101 and second density zone 102, and only some slices close to the highest point of the hemispherical shell include circular first density zone 101 and second density zone 102, or only include circular first density zone 101.

[0209] According to the height of the hemispherical shell of the antenna cover of 200mm and the slice thickness of 0.1mm, the total number of slices is calculated to be 2000. According to actual needs, 200 slices are selected and a layer of two-dimensional fiber fabric is designed in each of the 200 slices, that is, a total of 200 circular two-dimensional fiber fabrics are designed, evenly distributed in the 100th to 1700th slices, the 100th slice contains the first circular two-dimensional fiber fabric, and the rest are arranged according to the following distribution rule: 7 slices (without fabric) + 1 layer (containing a layer of two-dimensional fiber fabric). The plane size of each layer of two-dimensional fiber fabric is 0.2mm smaller than the plane size of the slice where the corresponding layer of two-dimensional fiber fabric is located, and the thickness of each layer of two-dimensional fiber fabric is the same and less than 0.1mm. The planes where the 200 circular two-dimensional fabrics are located are parallel to each other and are perpendicular to the layer-by-layer stacking direction of 3D printing, that is, the Z direction.

[0210] Step S3, prefabricating 200 layers of circular ring-shaped two-dimensional fiber fabric preforms capable of being shaped into a three-dimensional shape;

[0211] Step S31: Use ultra-small bundles of 0.12K silicon nitride fibers (each bundle has 120 fiber filaments, and the diameter of the filaments is 8 μm) to weave 200 circular two-dimensional fiber fabrics. The fiber arrangement in each circular two-dimensional fiber fabric is annular, that is, the fiber arrangement direction is mainly annular. The function of the radial fibers is mainly to connect the annular fibers together to form an integral two-dimensional fiber fabric. This is mainly because the annular direction is the main force direction of the hemispherical shell.

[0212] Step S32: 200 circular two-dimensional fiber fabrics are fully infiltrated with epoxy resin liquid and shaped by using a glue tank rolling pre-impregnation method to preform into a two-dimensional fiber fabric preform that can be shaped; specifically, 200 circular two-dimensional fiber fabrics are immersed in a glue tank containing epoxy resin liquid, and the two-dimensional fiber fabrics infiltrated with epoxy resin are squeezed by a rotating pair of hot pressing rollers (temperature is 60°C) through a rolling method, so that the fabric passing through the rollers is fully infiltrated, combined and compacted with the epoxy resin liquid under this action, and the epoxy resin is pre-cured at low temperature at 60°C to form 200 circular two-dimensional fiber fabric preforms with a certain shape and rigidity, which is convenient for maintaining the existing shape of the two-dimensional fiber fabric during the picking and placing operations, so as to ensure the operability of the placement and positioning during the subsequent 3D printing. By controlling the immersion and / or rolling parameters, the thickness of each two-dimensional fiber fabric preform is ensured to be less than 0.1mm, so as to ensure that when the layer is printed, the ceramic raw material can completely wrap the two-dimensional fiber fabric.

[0213] Step S33: Using a numerically controlled cutting machine to cut the 200 circular two-dimensional fiber fabric preforms to obtain 200 circular two-dimensional fiber fabric preforms of the required shape, and stacking them in the order of slice printing for later use. Figure 4 As shown, each layer of the annular two-dimensional fiber fabric preform 201 covers the entire area of ​​the slice of this layer, that is, the two ceramic raw materials S1 and S2 of this layer will be coated on this piece of two-dimensional fiber fabric, and the plane size of each layer of the annular two-dimensional fiber fabric preform 201 is 0.2 mm smaller than the plane size of the slice where the corresponding layer of the two-dimensional fiber fabric preform is located, so as to ensure that when this layer is printed, the ceramic raw materials can completely wrap the two-dimensional fabric.

[0214] Step S4: 3D printing is performed using a selective photo-stereolithography method to obtain a precursor of the antenna cover, including the following steps:

[0215] Step S401: accurately placing and positioning the two-dimensional fiber fabric preform;

[0216] When printing a layer of slices containing fibers, the robot automatically picks up the circular two-dimensional fiber fabric preform of the current layer and accurately positions it through infrared scanning. After placing the two-dimensional fiber fabric preform of the current layer, ultraviolet light is used to scan four points on the two-dimensional fiber fabric preform for photocuring positioning. The four points are distributed in a rectangular dot matrix (such as Figure 4 The first positioning point A, the second positioning point B, the third positioning point C, and the fourth positioning point D);

[0217] Step S402: laying or spraying ceramic raw materials;

[0218] Through the nozzle of the 3D printer, along the Z direction from bottom to top, most of the slices contain two density areas. In this case, the ceramic raw material S1 is laid or sprayed in the first density area 101, and the ceramic raw material S2 is laid or sprayed in the second density area 102 until the ceramic raw materials of the two density areas of the corresponding layer are laid or sprayed. When approaching the highest point of the hemisphere along the Z direction, a few slices only include the first density area 101. In this case, the ceramic raw material S1 is laid or sprayed in the first density area 101 until the ceramic raw materials of one density area of ​​the corresponding layer are laid or sprayed.

[0219] Step S403: Use ultraviolet light to scan the slice of the current layer, so that it solidifies from point to line and from line to surface in sequence, and completes the selected area light curing of the current layer, so that the epoxy resin of the current layer is transformed from liquid to solid;

[0220] Step S404: the molding printing platform descends one layer and continues printing the next layer.

[0221] It should be noted that when printing slices containing circular ring-shaped two-dimensional fiber fabric preforms (for example, the 100th layer, the 108th layer), 3D printing is performed according to steps S401 to S404; when printing slices that do not contain circular ring-shaped two-dimensional fiber fabric preforms, 3D printing is performed according to steps S402 to S404, and the above steps are repeated until the last layer of slices is printed to obtain the precursor of the antenna cover.

[0222] Step S5, degreasing and sintering;

[0223] Degreasing: The precursor obtained in step S4 is placed in a sintering furnace for degreasing treatment; in the sintering furnace, the epoxy resin in the precursor of the antenna cover, including the epoxy resin pre-impregnated in the two-dimensional fiber fabric in step S3, will be completely discharged, and the resin will completely volatilize under high temperature to form pores, so that a porous ceramic structure can be obtained.

[0224] Sintering: The degreased product is further sintered in a sintering furnace to obtain the final radome product. For specific parameters, see Table 1;

[0225] Table 1: Specific process parameters for debinding and sintering:

[0226]

[0227] Through the above steps, the obtained radome includes two ceramic substrate layers with different densities, the outer layer is 2.8g / cm 3 Porous silicon nitride ceramics, inner layer 2.0g / cm 3 The porous silicon nitride ceramic has different densities in the inner and outer layers, and thus different pore contents and dielectric constants, which can achieve excellent broadband wave transmission performance; at the same time, since the antenna cover adopts a "gradient porous ceramic matrix + fiber reinforced phase" composite structure, it is not necessary to increase the thickness of the low-density area to obtain better mechanical properties, thereby minimizing the structural weight and meeting the high requirements of the product for mechanical properties. This is of great significance for achieving lightweight and high performance of the antenna cover on high-speed aircraft.

[0228] The antenna cover in this embodiment adopts an additive manufacturing method. Compared with the three traditional methods of producing this sandwich structure in the prior art, the production efficiency is increased by more than 60%, and rapid manufacturing is achieved without being restricted by molds; at the same time, the porosity and density distribution of different gradient layers can be accurately controlled, so as to achieve the purpose of regulating the dielectric constants of different gradient layers; because it is 3D printed in one piece, different density areas are tightly combined, compared with the method of producing this sandwich structure in the prior art (assembling structures of different densities together), it effectively solves the problems of loose connection and low reliability between the assembled components.

[0229] After the antenna cover in this embodiment is reinforced with continuous fibers, the circumferential mechanical properties (main force direction) of the hemispherical shell are improved by at least 10% with almost no increase in weight. It should be noted that this embodiment is only used to illustrate the principles of the present invention, and the fiber content is relatively small. As the fiber content increases, the mechanical properties can be further significantly improved.

[0230] Embodiment 2:

[0231] The difference between this embodiment and Embodiment 1 is that in step S1, the gradient structure components include two ceramic powders, namely, the first is silicon nitride powder with an average particle size of 30 μm, the second is silicon nitride powder with an average particle size of 80 μm, and an epoxy resin (i.e., epoxy resin liquid with a weight average molecular weight of 500).

[0232] The content of each component in each layer of the gradient structure: the first density area 101 includes 80wt% of silicon nitride powder (average particle size of 30μm) and 20wt% of epoxy resin; the second density area 102 includes 80wt% of silicon nitride powder (average particle size of 80μm) and 20wt% of epoxy resin;

[0233] The final outer layer density of the radome is 2.9g / cm 3 , the inner layer density is 1.9g / cm 3 .

[0234] Embodiment 3:

[0235] The difference between this embodiment and embodiment 1 is that in step S1, the gradient structure component includes a ceramic powder (i.e., silicon nitride powder with an average particle size of 50 μm) and an epoxy resin (i.e., epoxy resin powder with a weight average molecular weight of 7000);

[0236] Step S4: 3D printing is performed using a laser selective sintering method to obtain a precursor of the antenna cover, including the following steps:

[0237] Step S411: accurately placing and positioning the two-dimensional fiber preform;

[0238] When printing a layer of slices containing fibers, the robot automatically picks up the two-dimensional fiber fabric preform of the current layer and accurately positions and places it through infrared scanning. After placing the two-dimensional fiber fabric preform of the current layer, laser scanning is used to perform thermal curing positioning on four points on the two-dimensional fiber fabric preform. The four points are distributed in a rectangular lattice (such as Figure 4 ABCD four points);

[0239] Step S412: laying or spraying ceramic raw materials;

[0240] Through the nozzle of the 3D printer, along the Z direction from bottom to top, most of the slices contain two density areas. In this case, the ceramic raw material S1 is laid or sprayed in the first density area 101, and the ceramic raw material S2 is laid or sprayed in the second density area 102 until the ceramic raw materials of the two density areas of the corresponding layer are laid or sprayed. When approaching the highest point of the hemisphere along the Z direction, a few slices only include the first density area 101. In this case, the ceramic raw material S1 is laid or sprayed in the first density area 101 until the ceramic raw materials of one density area of ​​the corresponding layer are laid or sprayed.

[0241] Step S413: Use an infrared laser to scan the current layer slice, so that it solidifies from point to line and from line to surface in sequence, and completes the laser selective sintering of the current layer; the principle of the laser selective sintering is: the epoxy resin powder in the ceramic raw material melts and undergoes a thermal curing reaction under the irradiation of a high-intensity laser, and after curing, the ceramic powder is bonded together to form a ceramic precursor.

[0242] Step S414: the molding printing platform descends one layer and continues printing the next layer.

[0243] Among them, when printing a slice containing a ring-shaped two-dimensional fiber fabric preform (for example, the 100th layer, the 108th layer), 3D printing is performed according to steps S411 to S414; when printing a slice that does not contain a ring-shaped two-dimensional fiber fabric preform, 3D printing is performed according to steps S412 to S414, and the above steps are repeated until the last layer of slices is printed to obtain the precursor of the antenna cover.

[0244] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. An additive manufacturing method for a gradient porous ceramic matrix composite product, characterized in that: The additive manufacturing method comprises the following steps: Step S1, preparing ceramic raw materials required for forming each ceramic matrix layer of a gradient structure along a gradient direction of the composite material; Step S2, establishing a three-dimensional model of a gradient porous ceramic-based composite material product, wherein the XY plane is the gradient direction, and the Z direction perpendicular to the XY plane is set as the layer-by-layer stacking direction, and slicing is performed; wherein each layer of the two-dimensional fiber fabric is contained in the corresponding slice; each layer of the slice includes m gradient regions from the outer surface to the inside of the product, namely, the first gradient region, the second gradient region...the m-1th gradient region, the mth gradient region, 1≤m≤n, n is the number of layers of the gradient structure, and n≥2 is a natural number; Step S3, prefabricating a W-layer two-dimensional fiber fabric preform capable of being shaped into a three-dimensional shape; W ≥ 1 and is a natural number; Step S4: n ceramic matrix layers and W two-dimensional fiber fabric preforms are stacked layer by layer along the Z direction by 3D printing. When printing a certain layer of slices containing two-dimensional fiber fabrics, the two-dimensional fiber preforms are first accurately laid out in the corresponding order and positioned. Then, ceramic raw materials S1, S2, ... S are placed in m gradient zones, i.e., the first gradient zone, the second gradient zone ... the m-1 gradient zone, the m gradient zone. m-1 , S m ; Obtain the precursor of gradient porous ceramic matrix composite material product: Step S5, degreasing and sintering the precursor.

2. The additive manufacturing method of the gradient porous ceramic matrix composite product according to claim 1, characterized in that: The main steps of step S1 include: according to the number of layers n of the gradient structure, the composition of the ceramic matrix layer, and the content of each component in each ceramic matrix layer, the raw materials required for each ceramic matrix layer are mixed to obtain the ceramic raw materials S1, S2, ... S required for the first gradient layer, the second gradient layer ... the n-1 gradient layer, the n gradient layer from the outer surface to the inside of the product. n-1 , S n , n≥2.

3. The additive manufacturing method of the gradient porous ceramic matrix composite product according to claim 2, characterized in that: In step S1, the designable variables of the composition of the ceramic matrix layer include the type of ceramic powder, the particle size of the ceramic powder, and the type of resin.

4. The additive manufacturing method of the gradient porous ceramic matrix composite product according to claim 1, characterized in that: In step S2, each layer of the two-dimensional fiber fabric covers a partial area or the entire area of ​​k adjacent ceramic matrix layers in the corresponding slice, 2≤k≤n.

5. The additive manufacturing method of the gradient porous ceramic matrix composite product according to claim 1, characterized in that: The product is a radome, and the radome is a hemispherical shell; In step S1, according to the radome having n layers of gradient structure with different densities from the outer surface to the inner surface, i.e., the first density layer, the second density layer ... the n-1th density layer, the nth density layer, and the components of the n density layers and the content ratio of each component in each density layer, a ceramic raw material required for each density layer is prepared; In step S2, a three-dimensional model of the radome is established, and the axial direction of the radome is set to the Z direction of layer-by-layer stacking, and a slicing process is performed; wherein each layer of the annular two-dimensional fiber fabric is included in the corresponding slice; each layer of the slice includes a first density area, a second density area, ... an m-1th density area, an mth density area, from the outer surface to the inner surface of the radome, in sequence, 1≤m≤n; In step S3, W circular two-dimensional fiber fabrics are prefabricated, wherein the fiber arrangement direction of the circular two-dimensional fiber fabrics is mainly circumferential, and the circumferential fibers are connected by radial fibers to form an integral two-dimensional fiber fabric, and the W circular two-dimensional fiber fabrics are preformed into W circular ring-shaped two-dimensional fiber fabric preforms that can be shaped; In step S4, a precursor of the antenna cover is obtained by selective photocuring or laser selective sintering: when printing a certain layer of slices containing two-dimensional fiber fabrics, firstly accurately lay out the corresponding order of circular two-dimensional fiber layer preforms, position them, and then lay or spray ceramic raw materials S1, S2, ... S in m density areas, i.e., the first density area, the second density area ... the m-1 density area, the m density area. m-1 , S m .

6. The additive manufacturing method of the gradient porous ceramic matrix composite product according to claim 5, characterized in that: The density of the first density layer, the second density layer, ... the n-1th density layer, and the nth density layer decreases in sequence from the outer surface to the inner surface of the antenna cover.

7. The additive manufacturing method of the gradient porous ceramic matrix composite product according to claim 5, characterized in that: In step S1, the components of the n density layers include a ceramic powder and a resin, and the ceramic raw materials S1, S2 ... n-1 , S n The content ratio of ceramic powder to resin decreases successively.

8. The additive manufacturing method of the gradient porous ceramic matrix composite product according to claim 5, characterized in that: In step S1, the components of the n density layers include n kinds of ceramic powders with different particle sizes and a resin, and the ceramic raw materials S1, S2, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16, S17, S18, S19, S20, S21, S22, S30, S31, S32, S33, S34, S35, S36, S37, S38, S39, S40, S41, S42, S43, S44, S45, S46, S47, S48, S49, S50, S51, S52, S53, S54, S55, S56, S57, S58, S59, S60, S61, S62, S63, S64, S n-1 , S n The particle size of the ceramic powder increases successively.

9. The additive manufacturing method of the gradient porous ceramic matrix composite product according to claim 5, characterized in that: In step S4, the laser selective sintering method specifically includes the following steps: Step S411: accurately placing and positioning the two-dimensional fiber fabric preform; Step S412: laying or spraying ceramic raw materials in m density areas corresponding to the slice layer; Step S413: Scan the current layer with laser to melt the resin in the ceramic raw materials of the m density zones from point to line, from line to surface, and cool and solidify, or melt and heat-cure, to complete the laser selective sintering of the current layer; Step S414: the molding printing platform descends one layer and continues printing the next layer. Repeat the above steps S411 to S414, or S412 to S414, until the last slice layer is printed.

10. The additive manufacturing method of the gradient porous ceramic matrix composite product according to claim 3, characterized in that: The types of the ceramic powder include, but are not limited to, one or a combination of SiC ceramics, Si3N4 ceramics, Al2O3, SiO2, ZrO2, mullite, calcium aluminum silicate glass, lithium aluminum silicate glass, magnesium aluminum silicate glass, borate glass, and quartz glass.

Images