Single-stroke breakpoint-free path planning method for 3D printing of variable-wall-thickness honeycomb structure

Abstract

The invention discloses a single-stroke breakpoint-free path planning method for a 3D printing variable-wall-thickness honeycomb structure, and the method comprises the following steps: determining the stress distribution condition of an equal-wall-thickness honeycomb structure continuous carbon fiber reinforced silicon carbide ceramic-based composite material through software simulation, and determining a weakest region and a weakest region; variable-wall-thickness honeycomb printing is arranged in the weakest area and the weaker area; the side length and the offset distance of the honeycomb unit are determined, and a 3D printing path is set, specifically, the odd-number-layer path is different from the even-number-layer path, the outer contours of the honeycomb unit are sequentially printed in the vertical direction through the odd-number-layer path, the honeycomb unit does not completely pass through each honeycomb wall of the honeycomb structure, and the honeycomb structure is not completely formed after printing is completed; and when the next even-numbered layer is printed, missing honeycomb walls of the upper odd-numbered layer are passed twice, so that the missing honeycomb walls are complemented, and a complete variable-wall-thickness honeycomb structure is formed. According to the method, weak spots are effectively strengthened in a targeted mode, the material is not prone to damage, and the mechanical property is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printing of continuous carbon fiber reinforced silicon carbide ceramic matrix composite materials, and in particular to a single-stroke breakpoint-free path planning method for 3D printing of a variable-wall-thickness honeycomb structure. Background Art

[0002] Honeycomb structure continuous carbon fiber reinforced silicon carbide ceramic matrix composites can achieve lightweight while having good compression resistance. When compression tests are carried out on honeycomb structure continuous carbon fiber reinforced silicon carbide ceramic matrix composites with equal wall thickness, they always fail first at the same position, and the stress changes regularly.

[0003] At present, the existing patents have not planned a 3D printing path based on the stress change law of the honeycomb structure. The Chinese patent with publication number CN110181812A discloses a 3D printing method for a continuous carbon fiber honeycomb structure and its perception and recovery method. The honeycomb structure 3D printing path involved has two wall thicknesses on two opposite sides of the hexagon and one wall thickness on the other four sides, such as Figure 6 As shown in the figure, the purpose of variable wall thickness is to complete the 3D printed honeycomb structure, and no targeted reinforcement is performed on the weak points. When compressed, there is stress concentration, which is prone to damage.

[0004] In view of this, the present invention proposes a single-stroke breakpoint-free path planning method for 3D printing of variable-wall-thickness honeycomb structures suitable for continuous carbon fiber reinforced silicon carbide ceramic-based composites. Summary of the Invention

[0005] The purpose of the present invention is to propose a single-stroke breakpoint-free path planning method for 3D printing variable-wall thickness honeycomb structures to solve the problem of obvious weak points in the medium-wall thickness honeycomb structures in the above-mentioned background technology. The continuous carbon fiber of the present invention fully plays the role of bearing, which can effectively improve the efficiency of preparing continuous carbon fiber reinforced silicon carbide ceramic-based composite materials with variable-wall thickness honeycomb structures and improve the mechanical properties.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A single-stroke, breakpoint-free path planning method for 3D printing a honeycomb structure with variable wall thickness, the path planning method comprising the following steps:

[0008] Step 1: Determine the stress distribution of the continuous carbon fiber reinforced silicon carbide ceramic matrix composite material with uniform wall thickness honeycomb structure through software simulation. The specimen is prone to damage at the diagonal. The two end nodes of the honeycomb edge where the diagonal center is located are extended upward and downward to determine the two nearest neighboring edges. The honeycomb edge where the diagonal center is located and the nearest neighboring edge form the weakest area. Find the upper and lower opposite edges of the nearest neighboring edge as the weaker edges. The two nearest neighboring edges have a total of four weaker edges. The two weaker edges on the upper side of the weakest area are connected in a honeycomb to form a weaker area. The two weaker edges on the lower side of the weakest area are connected in a honeycomb to form a weaker area. Set variable wall thickness honeycomb printing in the weakest area and the weaker area.

[0009] Step 2: Determine the side length a and offset distance d of the honeycomb unit, and set the 3D printing path: The odd-numbered layer path is different from the even-numbered layer path. The odd-numbered layer path prints the outer contour of the honeycomb unit in the vertical direction in sequence, and does not completely pass through each honeycomb wall of the honeycomb structure. After printing, the honeycomb structure is not completely formed. When printing the next even-numbered layer, the missing honeycomb wall of the previous odd-numbered layer will be passed twice, thereby completing the missing honeycomb wall and forming a complete variable wall thickness honeycomb structure.

[0010] The end point of the odd-numbered layer path is the starting point of the next even-numbered layer path, and the end point of the even-numbered layer path is the starting point of the next odd-numbered layer path. After one layer is printed, the printing device is lifted from its original position to the starting point of the next layer.

[0011] Furthermore, when printing odd-numbered layers, after passing through a relatively weak area, continue to print a small honeycomb unit with a side length of ad forward, then print a path with a length of a horizontally inward, and then print a path with a side length of ad, a, a, ad downward along the honeycomb contour, and then print a path with a length of ad horizontally outward, and then print a path with a side length of ad, a, a, ad upward along the honeycomb contour, and then continue to print the honeycomb contour along the honeycomb side length a;

[0012] When entering the weakest area, print with side lengths ad, a, a, ad in sequence, then print a path with length ad horizontally inward, then print paths with side lengths ad, a, a, ad upward along the honeycomb contour, then print a path with length a horizontally outward, then print a path with length ad downward, then continue printing along the honeycomb contour with length d;

[0013] When printing the even-numbered layers, the honeycomb contour is printed horizontally in the opposite direction to the printing direction of the odd-numbered layers. After passing the weaker area on the lower side, the length of d is printed horizontally outward, and then a circle of ad length is printed in the counterclockwise direction to return to the main printing path. When entering the weaker area on the lower side again, the length of d is printed horizontally inward, and then a circle of ad length is printed in the counterclockwise direction to return to the main printing path. After passing the weaker area on the upper side, the length of d is printed horizontally outward, and then the main printing path is returned in the clockwise direction. After that, after passing the weaker area on the upper side again, the length of d is printed horizontally outward, and then the main printing path is returned in the clockwise direction until the printing of the current even-numbered layer is completed.

[0014] Furthermore, the variable wall thickness honeycomb printing thickens the honeycomb wall to a corresponding degree by adjusting the printing path according to the degree of weakness at different positions of the honeycomb structure with constant wall thickness;

[0015] When the number of honeycombs changes, the area should be redivided according to the stress distribution in the simulation results, and different numbers of honeycomb walls should be printed for corresponding reinforcement.

[0016] Furthermore, the vertical distance between the centers of the upper and lower layers of 3D-printed pulp strips is smaller than the diameter of the extruded pulp strips.

[0017] Furthermore, the single stroke path without breakpoints is planned as a bundle of continuous carbon fibers and ceramic slurry are continuously formed, and the continuous carbon fibers in the ceramic body have no breakpoints.

[0018] The present invention also protects a continuous carbon fiber reinforced silicon carbide ceramic matrix composite material, which is obtained by 3D printing technology using the path planning method described above; specifically:

[0019] After impregnating the continuous carbon fiber in the prepreg slurry, the continuous carbon fiber is coaxially co-extruded with the chopped carbon fiber / silicon carbide ceramic slurry to print a variable wall thickness honeycomb structure continuous carbon fiber reinforced silicon carbide blank;

[0020] After the green body is dried and carbonized, it is impregnated and cracked to obtain a continuous carbon fiber reinforced silicon carbide ceramic matrix composite material with a variable wall thickness honeycomb structure.

[0021] Furthermore, the prepreg slurry is a mixture of liquid phenolic resin and silicon carbide powder, and the chopped carbon fiber / silicon carbide ceramic slurry is a mixture of liquid phenolic resin, silicon carbide powder and chopped carbon fiber.

[0022] Furthermore, the drying temperature is 40°C to 80°C, and the carbonization temperature is 700°C to 800°C;

[0023] The process of impregnation and cracking is: first vacuum negative pressure, then 0.7MPa positive pressure impregnation, solidification, and cracking under protective atmosphere. The cracking temperature is 1100℃ to 1200℃.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] By adopting the path planning method of the present invention, single-stroke breakpoint-free 3D printing of continuous carbon fiber reinforced silicon carbide ceramic-based composite materials with variable wall thickness honeycomb structures can be effectively achieved.

[0026] The present invention targets the stress concentration area of ​​the honeycomb structure and thickens the wall thickness to different degrees according to the stress distribution law, so that the stress of the honeycomb structure is evenly distributed.

[0027] The single bundle of continuous carbon fibers of the present invention has no breakpoints and bears load as a whole. The composite material is not easily damaged when compressed. The preparation method of the present invention can improve the mechanical properties of the composite material as a whole and shorten the preparation cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of a single-stroke, non-breakpoint path for a honeycomb structure of equal wall thickness; the left figure is a schematic diagram of the path for the first layer, i.e., the odd-numbered layers, and the right figure is a schematic diagram of the path for the second layer, i.e., the even-numbered layers.

[0029] Figure 2 This is the simulated equivalent stress distribution diagram of the critical point of compression failure of silicon carbide ceramic materials with equal wall thickness honeycomb structure.

[0030] Figure 3 This is the compression failure diagram of silicon carbide ceramic material with equal wall thickness honeycomb structure.

[0031] Figure 4 This is a schematic diagram of a single-stroke, non-breakpoint path of a variable-wall-thickness honeycomb structure provided by the present invention, wherein the left figure is a schematic diagram of the path of the first layer, i.e., the odd-numbered layers, and the right figure is a schematic diagram of the path of the second layer, i.e., the even-numbered layers.

[0032] Figure 5 Schematic diagram of the overall structure of the robotic arm and print head used in an embodiment of the present invention.

[0033] Figure 6 This is a schematic diagram of the continuous printing path in existing literature. DETAILED DESCRIPTION

[0034] To make the technical problems solved, the technical solutions adopted, and the technical effects achieved by the present invention more clear, the technical solutions of the embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0035] It should be understood that the terminology used herein is intended solely to describe particular embodiments and is not intended to limit the invention. Furthermore, for numerical ranges herein, it should be understood that each intervening value between the upper and lower limits of the range is specifically disclosed. Each smaller range between any stated value or stated range, as well as any other stated value or intervening value within the stated range, is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0036] Example 1

[0037] The single-stroke non-breakpoint path planning method for 3D printing a variable-wall-thickness honeycomb structure in this embodiment is used to prepare a continuous carbon fiber reinforced silicon carbide ceramic matrix composite material. The specific process is:

[0038] Step 1: Using the robotic arm as a carrier, according to the weak points of the constant wall thickness honeycomb structure continuous carbon fiber reinforced silicon carbide ceramic matrix composite material, set the variable wall thickness honeycomb structure 3D printing path that the robotic arm can identify on the supporting software of the robotic arm (see Figure 4 ), where the wall thickness at the weakest point is three times the normal wall thickness, and the weakest point is twice the normal wall thickness;

[0039] Step 2: Thermosetting phenolic resin and silicon carbide powder are mixed in a mass ratio of 3:1, and mechanically stirred to form a prepreg slurry. The silicon carbide powder and chopped carbon fiber are mixed in a mass ratio of 5:2, ball milled at a speed of 300r / min for 4h, and rotary evaporated to obtain a composite powder. The phenolic resin and the composite powder are mixed in a mass ratio of 1:2 to obtain chopped carbon fiber / silicon carbide ceramic slurry, which is then placed in a slurry tube. The 6k continuous carbon fiber (6k continuous carbon fiber, i.e., a bundle of continuous carbon fibers containing 6000 continuous carbon fibers) is impregnated in the prepreg slurry and then passed through the fiber tube. The slurry is then extruded through a coaxial co-extrusion device mounted on a robotic arm (see Figure 5 ) and chopped carbon fiber / silicon carbide ceramic slurry are coaxially co-extruded to print a variable wall thickness honeycomb structure continuous carbon fiber reinforced silicon carbide blank;

[0040] Step 3: After the green body is dried at 40°C, 50°C, 60°C, 70°C and 80°C for 8 hours respectively, it is heated to 800°C at a heating rate of 1°C per minute in a nitrogen atmosphere, kept warm for 1 hour for carbonization, then vacuumed for 2 hours and impregnated at a positive pressure of 0.7MPa for 8 hours. After impregnation, it is cured at 160°C. The cured composite green body is heated to 1100°C or 1200°C at a heating rate of 3°C per minute in a nitrogen atmosphere, kept warm for 1 hour and cracked to obtain a variable wall thickness honeycomb structure continuous carbon fiber reinforced silicon carbide ceramic matrix composite material.

[0041] Figure 2 For the basis Figure 1The compression simulation equivalent stress distribution diagram obtained by simulating the printing path 3D modeling of the silicon carbide ceramic material with a honeycomb structure of equal wall thickness. The relative color depth in the figure represents the stress magnitude, and the transition from blue to red indicates that the stress gradually increases. Figure 3 For Figure 1 The compression failure diagram of the honeycomb structure silicon carbide ceramic material with equal wall thickness obtained by printing the printing path. During the compression process, the honeycomb structure silicon carbide ceramic material always fails at the diagonal line. Figure 2 、 Figure 3 The compression direction is longitudinal.

[0042] From the simulation results, it can be seen that the longitudinal honeycomb wall plays the main role in bearing, and multiple wall thicknesses need to be printed in the weak stress areas to strengthen them. Figure 2 Taking the honeycomb structure as an example, according to the stress distribution (the dark area in the figure) combined with Figure 3 The results of the medium compression failure can be roughly divided into three categories for the longitudinal honeycomb wall, with the weakest part being the dark area ( Figure 1 The 19th, 20th, and 21st paths in the first layer of the middle layer are the weaker areas where the dark areas and light areas are evenly distributed ( Figure 1 The 10th, 11th, 12th, 13th, 27th, 28th, 29th, and 30th paths in the first layer (in the middle) and areas with lower stress. The numbers corresponding to the printing paths in the figure, from small to large, represent the order of the printing process. Continuous carbon fibers are continuously deposited on the substrate along the paths under the shear force of the ceramic slurry.

[0043] The honeycomb wall is thickened by printing different numbers of passes in three areas. Three passes are printed at the weakest part, two passes are printed at the weaker part, and one pass is printed at other areas. In order to achieve single-stroke non-breakpoint printing of continuous carbon fiber reinforced silicon carbide ceramic matrix composite materials with variable wall thickness, some transverse honeycomb walls ( Figure 1 The second layer (6, 15, 24, 33, 42, 51) is thickened.

[0044] In the present invention, when the number of honeycombs changes, the area should be re-divided according to the stress distribution in the simulation results, and different numbers of honeycomb walls should be printed for corresponding reinforcement to ensure uniform stress distribution.

[0045] Figure 4 This is a schematic diagram of a single-stroke, non-breakpoint path for a variable-wall-thickness honeycomb structure. In the figure, a complete honeycomb structure is not formed after the first layer is printed. The 14th path should be a double-wall-thickness location, but the first layer only has a single wall thickness on the 14th path. When printing the second layer, the 63rd path is the second wall thickness that was not printed on the first layer. The 38th and 70th paths are the two paths of the second layer, respectively. After every two layers are printed, a complete variable-wall-thickness honeycomb structure is formed.

[0046] Figure 4The first layer of honeycomb can be considered as printed in the longitudinal direction. After the longitudinal outer honeycomb wall is printed at the two thickened honeycomb walls ( Figure 4 First layer, pass 13), switch to printing the inner honeycomb structure ( Figure 4 The first layer, step 14), prints the inner honeycomb structure completely ( Figure 4 (23rd pass of the first layer), the printing direction can return to the printing direction of the outer honeycomb wall to continue printing the remaining paths. This printing method can avoid large-angle deflection of continuous carbon fibers at the connection between the two paths during printing, providing high-quality support for the second layer. The remaining two thickened honeycomb walls are printed in the same way. After the two thickened honeycomb walls are printed, the three thickened honeycomb walls are naturally printed.

[0047] Figure 4 The entire second layer of honeycombs can be considered to be printed in the horizontal direction, and the missing honeycomb walls of the first layer are completed by printing along the corresponding path based on the first layer.

[0048] Figure 4 The unnumbered paths are flat panels. Starting from the starting point, the arrows point to the printing order. The first and second layers in the figure correspond to the actual positions. The end point of the first layer is lifted from its original position to become the starting point of the second layer.

[0049] Figure 4 The mid-plane panel is located on one side of the honeycomb wall. The contact area between the plane panel and the variable wall thickness honeycomb structure is large, and the bonding effect is better, which is conducive to enhancing performance.

[0050] Furthermore, 6k continuous carbon fiber can be replaced by continuous carbon fibers of different specifications such as 1k, 3k and 12k.

[0051] The vertical distance between the centers of the upper and lower layers of 3D printed pulp strips (i.e., the printing height) is smaller than the diameter of the extruded pulp strips, which can ensure good bonding between layers and between lanes.

[0052] Example 2

[0053] In this embodiment, the impregnation method in step 2 is to place the continuous carbon fibers into a pre-impregnation slurry pool and disperse the continuous carbon fibers by ultrasonication for 15 minutes, thereby ensuring good impregnation efficiency.

[0054] In step three, the solution used for impregnation is polycarbosilane solution, and the solution is impregnated and cracked six times. The cracking temperatures are 1100°C, 1100°C, 1200°C, 1100°C, 1200°C, and 1100°C, and the atmosphere is nitrogen.

[0055] Example 3

[0056] The single-stroke non-breakpoint path planning method for 3D printing a honeycomb structure with variable wall thickness in this embodiment includes the following steps:

[0057] Step 1: Determine the stress distribution of the continuous carbon fiber reinforced silicon carbide ceramic matrix composite material with uniform wall thickness honeycomb structure through software simulation. The specimen is prone to damage at the diagonal. The two end nodes of the honeycomb edge where the diagonal center is located are extended upward and downward to determine the two nearest neighboring edges. The honeycomb edge where the diagonal center is located and the nearest neighboring edge form the weakest area. Find the upper and lower opposite edges of the nearest neighboring edge as the weaker edges. The two nearest neighboring edges have a total of four weaker edges. The two weaker edges on the upper side of the weakest area are connected in a honeycomb to form a weaker area. The two weaker edges on the lower side of the weakest area are connected in a honeycomb to form a weaker area. Set variable wall thickness honeycomb printing in the weakest area and the weaker area.

[0058] Step 2: Determine the side length a and offset distance d of the honeycomb unit, and set the 3D printing path: The odd-numbered layer path is different from the even-numbered layer path. The odd-numbered layer path prints the outer contour of the honeycomb unit in the vertical direction in sequence, and does not completely pass through each honeycomb wall of the honeycomb structure. After printing, the honeycomb structure is not completely formed. When printing the next even-numbered layer, the missing honeycomb wall of the previous odd-numbered layer will be passed twice, thereby completing the missing honeycomb wall and forming a complete variable wall thickness honeycomb structure.

[0059] The end point of the odd-numbered layer path is the starting point of the next even-numbered layer path, and the end point of the even-numbered layer path is the starting point of the next odd-numbered layer path. After one layer is printed, the printing device is lifted from its original position to the starting point of the next layer.

[0060] When printing odd-numbered layers, after passing through a relatively weak area, continue forward to print a small honeycomb unit with a side length of ad, then print a path with a length of a horizontally inward, and then print a path with a side length of ad, a, a, ad downward along the honeycomb contour. Then, print a path with a length of ad horizontally outward, and then print a path with a side length of ad, a, a, ad upward along the honeycomb contour, and then continue printing the honeycomb contour along the honeycomb side length a.

[0061] When entering the weakest area, print with side lengths ad, a, a, ad in sequence, then print a path with length ad horizontally inward, then print paths with side lengths ad, a, a, ad upward along the honeycomb contour, then print a path with length a horizontally outward, then print a path with length ad downward, then continue printing along the honeycomb contour with length d;

[0062] When printing the even-numbered layers, the honeycomb contour is printed horizontally in the opposite direction to the printing direction of the odd-numbered layers. After passing the weaker area on the lower side, the length of d is printed horizontally outward, and then a circle of ad length is printed in the counterclockwise direction to return to the main printing path. When entering the weaker area on the lower side again, the length of d is printed horizontally inward, and then a circle of ad length is printed in the counterclockwise direction to return to the main printing path. After passing the weaker area on the upper side, the length of d is printed horizontally outward, and then the main printing path is returned in the clockwise direction. After that, after passing the weaker area on the upper side again, the length of d is printed horizontally outward, and then the main printing path is returned in the clockwise direction until the printing of the current even-numbered layer is completed.

[0063] In the present invention, the offset distance d=ab, a is the side length of the hexagon when the honeycomb is printed with constant wall thickness, and b is the side length of the small hexagon when the honeycomb is printed with variable wall thickness.

[0064] In the present invention, inside and outside, up and down are relative concepts. The direction of the printed path is defined as outside, and the direction of the unprinted area is defined as inside. The area of ​​the odd-numbered layer close to the starting point is defined as top, and the area close to the end point is defined as bottom.

[0065] The variable-wall-thickness honeycomb printing path in this invention uses simulation to determine the stress distribution of a uniform-wall-thickness honeycomb structure before path planning. Based on the degree of weakness at different locations within the uniform-wall-thickness honeycomb structure, the printing path is adjusted to increase the honeycomb wall thickness accordingly. A single-stroke, seamless printing path involves continuous carbon fiber and ceramic slurry forming a continuous pattern. This continuous carbon fiber forms the ceramic body without breakpoints, ensuring the entire structure can withstand the load.

[0066] The printing path of the first layer should avoid large-angle deflection as much as possible to provide good support for the 3D printing process of the second layer.

[0067] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

[0068] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A single-stroke, non-breakpoint path planning method for 3D printing of variable-wall-thickness honeycomb structures, characterized in that: The path planning method comprises the following steps: Step 1: Determine the stress distribution of the continuous carbon fiber reinforced silicon carbide ceramic matrix composite material with uniform wall thickness honeycomb structure through software simulation. The specimen is prone to damage at the diagonal. The two end nodes of the honeycomb edge where the diagonal center is located are extended upward and downward to determine the two nearest neighboring edges. The honeycomb edge where the diagonal center is located and the nearest neighboring edge form the weakest area. Find the upper and lower opposite edges of the nearest neighboring edge as the weaker edges. The two nearest neighboring edges have a total of four weaker edges. The two weaker edges on the upper side of the weakest area are connected in a honeycomb to form a weaker area. The two weaker edges on the lower side of the weakest area are connected in a honeycomb to form a weaker area. Set variable wall thickness honeycomb printing in the weakest area and the weaker area. Step 2: Determine the side length a and offset distance d of the honeycomb unit, and set the 3D printing path: The odd-numbered layer path is different from the even-numbered layer path. The odd-numbered layer path prints the outer contour of the honeycomb unit in the vertical direction in sequence, and does not completely pass through each honeycomb wall of the honeycomb structure. After printing, the honeycomb structure is not completely formed. When printing the next even-numbered layer, the missing honeycomb wall of the previous odd-numbered layer will be passed twice, thereby completing the missing honeycomb wall and forming a complete variable wall thickness honeycomb structure. The end point of the odd-numbered layer path is the starting point of the next even-numbered layer path, and the end point of the even-numbered layer path is the starting point of the next odd-numbered layer path. After one layer is printed, the printing device is lifted from its original position to the starting point of the next layer.

2. The path planning method according to claim 1, characterized in that: When printing odd-numbered layers, after passing through a relatively weak area, continue forward to print a small honeycomb unit with a side length of ad, then print a path with a length of a horizontally inward, and then print a path with a side length of ad, a, a, ad downward along the honeycomb contour. Then, print a path with a length of ad horizontally outward, and then print a path with a side length of ad, a, a, ad upward along the honeycomb contour, and then continue printing the honeycomb contour along the honeycomb side length a. When entering the weakest area, print with side lengths ad, a, a, ad in sequence, then print a path with length ad horizontally inward, then print paths with side lengths ad, a, a, ad upward along the honeycomb contour, then print a path with length a horizontally outward, then print a path with length ad downward, then continue printing along the honeycomb contour with length d; When printing the even-numbered layers, the honeycomb contour is printed horizontally in the opposite direction to the printing direction of the odd-numbered layers. After passing the weaker area on the lower side, the length of d is printed horizontally outward, and then a circle of ad length is printed in the counterclockwise direction to return to the main printing path. When entering the weaker area on the lower side again, the length of d is printed horizontally inward, and then a circle of ad length is printed in the counterclockwise direction to return to the main printing path. After passing the weaker area on the upper side, the length of d is printed horizontally outward, and then the main printing path is returned in the clockwise direction. After that, after passing the weaker area on the upper side again, the length of d is printed horizontally outward, and then the main printing path is returned in the clockwise direction until the printing of the current even-numbered layer is completed.

3. The path planning method according to claim 1, wherein: The variable wall thickness honeycomb printing thickens the honeycomb wall to a corresponding degree by adjusting the printing path according to the weakness of different positions of the honeycomb structure with constant wall thickness; When the number of honeycombs changes, the area should be redivided according to the stress distribution in the simulation results, and different numbers of honeycomb walls should be printed for corresponding reinforcement.

4. The path planning method according to claim 1, wherein: The vertical distance between the centers of the upper and lower layers of 3D printed pulp strips is smaller than the diameter of the extruded pulp strips.

5. The path planning method according to claim 1, wherein: The single stroke path without breakpoints is planned as a bundle of continuous carbon fibers and ceramic slurry are continuously formed, and the continuous carbon fibers in the ceramic body have no breakpoints.

6. A continuous carbon fiber reinforced silicon carbide ceramic matrix composite material, characterized in that: The composite material is obtained by 3D printing technology using the path planning method described in any one of claims 1 to 5; specifically: After impregnating the continuous carbon fiber in the prepreg slurry, the continuous carbon fiber is coaxially co-extruded with the chopped carbon fiber / silicon carbide ceramic slurry to print a variable wall thickness honeycomb structure continuous carbon fiber reinforced silicon carbide blank; After the green body is dried and carbonized, it is impregnated and cracked to obtain a continuous carbon fiber reinforced silicon carbide ceramic matrix composite material with a variable wall thickness honeycomb structure.

7. The composite material according to claim 6, characterized in that The pre-impregnation slurry is a mixture of liquid phenolic resin and silicon carbide powder, and the chopped carbon fiber / silicon carbide ceramic slurry is a mixture of liquid phenolic resin, silicon carbide powder and chopped carbon fibers.

8. The composite material according to claim 6, characterized in that The drying temperature is 40°C to 80°C, and the carbonization temperature is 700°C to 800°C; The process of impregnation and cracking is: first vacuum negative pressure, then 0.7MPa positive pressure impregnation, solidification, and cracking under protective atmosphere. The cracking temperature is 1100℃ to 1200℃.

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