Carbon fiber reinforced resin-based negative poisson ratio speed reducer shell and forming method thereof

Abstract

The invention discloses a carbon fiber reinforced resin-based negative Poisson ratio speed reducer shell and a forming method thereof, and relates to the technical field of speed reducers, carbon fibers are used as reinforcements, impurities on the surfaces of the carbon fibers are removed through pretreatment, then a PDA coating is synthesized on the surfaces of the carbon fibers in situ, an active functional group is introduced, and then caprolactam is used as a monomer to prepare the carbon fiber reinforced resin-based negative Poisson ratio speed reducer shell. PA6 is polymerized on the surface of the PDA coating in situ, molecular-level combination of carbon fibers and PA6 is achieved, in-situ PA6 coated PDA modified carbon fibers are obtained, the in-situ PA6 coated PDA modified carbon fibers and matrix PA6 resin are subjected to blending granulation, mold pressing thermoplastic forming and post-treatment, the speed reducer shell is prepared, and the speed reducer shell is filled with a negative Poisson's ratio structure. The technology can be reproduced, batch production can be achieved, the interface bonding force of the modified composite material is remarkably improved, the modified composite material has light weight, high strength, good heat dissipation and noise reduction performance and icing resistance, the negative Poisson's ratio structure filled inside is matched, vibration generated when a speed reducer works can be effectively attenuated, operation noise is further reduced, and the service life of the speed reducer is prolonged. Good practicability and industrialization prospects are realized.

Description

Technical Field

[0001] This invention relates to the field of speed reducer technology, and more specifically, to a carbon fiber reinforced resin-based negative Poisson's ratio speed reducer housing and its molding method. Background Technology

[0002] As a core component of the transmission system, the performance of the gearbox housing directly determines the system's motion accuracy, operational stability, service life, and noise level. With the development of transmission systems towards lightweight, high-precision, low-noise, and high-reliability designs, higher demands are placed on the material properties and structural design of gearbox housings. Currently, commonly used materials for gearbox housings include cast iron, cast steel, and aluminum alloys. Cast iron has a lower cost and better vibration damping, but it is heavy, prone to corrosion, and difficult to meet lightweight requirements. Cast steel has high strength and toughness, but poor casting performance, high cost, and difficult machining, making it unsuitable for mass production. While aluminum alloys can achieve lightweighting, their insufficient strength and rigidity, poor vibration damping, and tendency to generate significant noise during operation make them unsuitable for high-precision gearboxes.

[0003] To address the shortcomings of metal housings, carbon fiber reinforced thermoplastic composites, with their advantages of lightweight, high strength, and corrosion resistance, are increasingly being used in gearbox housing manufacturing. Among these, carbon fiber reinforced PA6 composites have become the mainstream choice due to their moderate cost and good processing performance. However, in existing technologies, the surface of carbon fiber is inert, resulting in poor interfacial compatibility and weak bonding with PA6 resin. Composites prepared by direct blending are prone to delamination and debonding, severely affecting the mechanical properties and structural stability of the housing. They cannot withstand the vibration loads and torque effects during gearbox operation, limiting their large-scale application in gearbox housings. Furthermore, existing carbon fiber modification methods mostly employ physical modification or conventional chemical modification, which have limited modification effects and easily damage the inherent strength of the carbon fiber, making it difficult to achieve molecular-level bonding between the carbon fiber and PA6 resin, thus failing to fully utilize the performance advantages of the composite material.

[0004] Furthermore, during the operation of a speed reducer, the meshing and rotation of its internal gears and bearings generate continuous vibrations. These vibrations not only reduce the speed reducer's transmission accuracy and service life but also radiate noise outwards through the housing, affecting the stability of the transmission system and the user experience. Existing speed reducer housings mostly employ a single-structure design with limited vibration damping performance. Even those housings with sandwich structures often use ordinary cushioning materials, which are insufficient to effectively attenuate vibrations in the low-to-high frequency range, failing to meet the requirements of high-precision, low-noise transmission systems. Negative Poisson's ratio structures, due to their unique deformation characteristics and excellent energy absorption and vibration damping capabilities, have significant advantages in vibration reduction. However, there is currently no technical solution that combines negative Poisson's ratio structures with carbon fiber reinforced PA6 composite materials for use in speed reducer housing sandwich filling to synergistically achieve lightweight, high-strength, and efficient vibration reduction. Moreover, existing applications of negative Poisson's ratio structures are largely limited to theoretical research, making it difficult to balance structural strength and manufacturing feasibility, and thus failing to meet the actual production and usage requirements of speed reducer housings.

[0005] Therefore, in response to the technical problems of weak interfacial bonding, difficulty in achieving both lightweight and high strength, poor vibration reduction and noise reduction effects, unreasonable modification process, and imperfect structural design of existing carbon fiber composite gearbox housings, it has become an urgent technical challenge for those skilled in the art to develop a gearbox housing preparation method that can achieve molecular-level bonding between carbon fiber and PA6 resin, possess lightweight, high strength and efficient vibration reduction performance, and whose process is reproducible and suitable for mass production. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a carbon fiber reinforced resin-based negative Poisson's ratio reducer housing and its molding method. The method involves pretreating the carbon fiber, in-situ synthesizing a PDA coating, and in-situ polymerizing and modifying it with PA6 to achieve molecular-level bonding between the carbon fiber and PA6 resin, thereby improving the interfacial bonding strength and mechanical properties of the composite material. The modified carbon fiber is then blended and granulated with the matrix PA6 resin and additives, and thermoplastically molded to prepare a reducer housing with a sandwich structure. The sandwich is filled with a negative Poisson's ratio structure to enhance vibration damping. This invention features a simple and reproducible process suitable for mass production. The prepared reducer housing combines lightweight, high strength, efficient vibration damping, and heat insulation against icing, effectively solving the problems of weak interfacial bonding, poor vibration damping, and difficulty in balancing lightweight and high strength in existing reducer housings. It can meet the requirements of high-precision transmission systems and has good practicality and industrialization prospects.

[0007] The specific solution of this invention is as follows: The first aspect of this invention provides a method for molding a carbon fiber reinforced resin-based negative Poisson's ratio gearbox housing, comprising the following steps: Step 1: Carbon fiber pretreatment to obtain clean carbon fiber; Step 2: In-situ synthesis of PDA coating on carbon fiber surface to obtain PDA-modified carbon fiber; Step 3: PA6 is polymerized in situ on the surface of PAD-modified carbon fiber to obtain in situ PA6-coated PDA-modified carbon fiber. Step 4, Granule preparation: The in-situ PA6-coated PDA-modified carbon fiber, matrix PA6 resin and additives obtained in step 3 are mixed evenly and then processed to form carbon fiber reinforced PA6 composite material granules. The moisture is removed to obtain dry carbon fiber reinforced PA6 composite material granules. Step 5, prepare the reducer housing mold: First, construct a negative Poisson's ratio structure, then construct a reducer housing with a sandwich structure, then fill the sandwich structure of the reducer housing with the negative Poisson's ratio structure to obtain a reducer housing filled with a vibration damping structure, and finally prepare the reducer housing mold by additive manufacturing. Step 6: Prepare carbon fiber reinforced PA6-based negative Poisson's ratio reducer housing: Using the reducer housing mold from Step 5, inject the dried carbon fiber reinforced PA6 composite material granules obtained in Step 4 to obtain the carbon fiber reinforced PA6-based negative Poisson's ratio reducer housing.

[0008] Preferably, the construction steps of the negative Poisson's ratio structure in step five are as follows: To sketch a negative Poisson's ratio element: First, draw a concave hexagon, which includes a parallel and symmetrical top and bottom edge. The two ends of the top and bottom edges are connected by a first and a second hypotenuse, respectively, with the connecting ends of the first and second hypotenuses facing inward. Then, arrange the concave hexagon in a circular array with an array angle of 90° and an array number of 4. All the second hypotenuses form an octagon. Delete the lines inside the octagon to complete the sketch of the negative Poisson's ratio element. Then, the sketch of the negative Poisson's ratio element is extruded and the thin-walled feature is selected. The octagon is filled with a cross to form the negative Poisson's ratio element. Then, the negative Poisson's ratio elements are arranged in a circular array with one of their center lines as the center of rotation. The array angle is 90° and the number of arrays is 2. The two negative Poisson's ratio elements form a cross. Centered on the aforementioned cross, six negative Poisson's ratio units are arranged to form a cube frame. The cube frame is connected to the edge of the cross to form a negative Poisson's ratio structural cell. The negative Poisson's ratio structure is obtained by linearly arranging the cell elements of the negative Poisson's ratio structure along the x, y, and z axes in sequence, with a number of arrays of 2.

[0009] Preferably, the specific steps of step one are as follows: Take carbon fiber, add it to a mixture of acetone and deionized water, soak it at room temperature, stirring regularly during the process, then wash it repeatedly until there is no acetone residue, dry it, remove impurities from the surface of the carbon fiber, and obtain clean carbon fiber.

[0010] Preferably, the specific steps of step two are as follows: Prepare a Tris solution, adjust the pH to 8.5, add dopamine hydrochloride, and stir until completely dissolved to obtain a PDA reaction solution; The clean carbon fiber obtained in step one is added to the PDA reaction solution and stirred to allow dopamine to polymerize in situ on the carbon fiber surface to form a uniform PDA nano-coating. After the reaction is complete, the carbon fiber is removed, the residual reaction solution on the surface is cleaned, and after drying, PDA-modified carbon fiber is obtained.

[0011] Preferably, the specific steps of step three are as follows: Take PDA-modified carbon fiber, caprolactam and initiator, add them to the reaction vessel, seal it and evacuate it. Heat it to 120℃ and keep it at that temperature for 2 hours to remove moisture by vacuum dehydration. The temperature was then increased to allow caprolactam to undergo in-situ ring-opening polymerization on the active functional groups of the PDA coating surface, forming a PA6 molecular brush covalently bonded to the carbon fiber. After the reaction was completed, the mixture was cooled to room temperature to obtain in-situ PA6-coated PDA-modified carbon fiber.

[0012] Preferably, the initiator is sodium caprolactam.

[0013] Preferably, the specific steps of step four are as follows: In-situ PA6-coated PDA-modified carbon fiber, matrix PA6 resin, and additives are mixed evenly and fed into a twin-screw extruder for melt blending. After melt blending, the mixture is extruded, drawn into strands, cooled, and pelletized to obtain carbon fiber reinforced PA6 composite material particles. Then, the particles are dried to remove moisture and obtain dry carbon fiber reinforced PA6 composite material granules.

[0014] Preferably, the additives include antioxidant 1098, antioxidant 168, and lubricant.

[0015] The second aspect of the present invention provides a carbon fiber reinforced resin-based negative Poisson's ratio reducer housing, characterized in that it is prepared according to the carbon fiber reinforced resin-based negative Poisson's ratio reducer housing molding method described in the first aspect.

[0016] The beneficial effects of this invention are as follows: Excellent modification effect: PDA coating modifies carbon fiber without damaging the carbon fiber itself. In-situ polymerization of PA6 achieves molecular-level bonding between carbon fiber and resin, increasing interfacial bonding force by more than 40%. The tensile strength and flexural strength of the composite material are significantly improved, ensuring that the reducer housing can withstand vibration loads and torque, and has excellent structural stability. Significant vibration reduction and noise reduction effects: The negative Poisson's ratio structure of the sandwich filling works synergistically with the carbon fiber reinforced PA6 composite material to effectively attenuate vibrations in the low-frequency to high-frequency range, reduce the operating noise of the reducer, and improve the working stability of the transmission system. Balancing lightweight and high strength: Carbon fiber reinforced PA6 composite material has a density much lower than that of metal materials, achieving lightweight gearbox housing while maintaining strength close to that of metal, meeting the requirements of high-precision gearboxes. The process is feasible and suitable for mass production: the entire process is simple and reproducible, the thermoplastic molding method is efficient and cost-effective, and the waste can be recycled, which meets the needs of industrial production. Excellent overall performance: The gearbox housing has good heat insulation, anti-icing and corrosion resistance, is suitable for different working environments, has a long service life and is highly practical. Attached Figure Description

[0017] Figure 1 The steps of the carbon fiber reinforced resin-based negative Poisson's ratio reducer housing molding method of the present invention are described.

[0018] Figure 2 This is a schematic diagram of the structure of the reducer housing of the present invention.

[0019] Figure 3 This is a schematic diagram of the reducer housing structure filled with a negative Poisson's ratio structure according to the present invention.

[0020] Figure 4 This is a schematic diagram illustrating the construction of the negative Poisson's ratio structure of the present invention, wherein, Figure 4 (a) is a sketch of a negative Poisson's ratio element. Figure 4 (b) is Figure 4 (a) Schematic diagram after stretching. Figure 4 (c) is a schematic diagram of the negative Poisson's ratio element. Figure 4 (d) is a schematic diagram of two negative Poisson's ratio units forming a cross shape. Figure 4 (e) is Figure 4 A schematic diagram of a negative Poisson's ratio element after translation and replication in (d). Figure 4 (f) is a schematic diagram of a negative Poisson's ratio cell. Figure 4 (g) is a schematic diagram of a negative Poisson's ratio structure. Detailed Implementation

[0021] The technical solutions of the present invention will now be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention.

[0022] This embodiment provides a method for molding a carbon fiber reinforced resin-based negative Poisson's ratio gearbox housing. Please refer to [link to relevant documentation]. Figure 1 It includes the following steps: Step 1: Carbon fiber pretreatment to obtain clean carbon fiber.

[0023] In this embodiment, the specific operation of step one is as follows: Take 100g of carbon fiber and add it to a mixed solution of 500g acetone and 500g deionized water. Soak it at room temperature for 12 hours, stirring regularly during the process. Then wash it repeatedly with deionized water until there is no acetone residue. Place it in a 60℃ oven and dry it for 8 hours to remove impurities such as sizing agent and oil stains from the surface of the carbon fiber, and obtain clean carbon fiber.

[0024] Among them, T300 type short-cut or continuous carbon fiber can be selected as the reinforcement.

[0025] During carbon fiber production, its surface is typically coated with a sizing agent (such as an epoxy resin coating). In subsequent processing, it may also become contaminated with oil and other impurities. Acetone, as a powerful organic solvent, can effectively dissolve and remove these impurities. Removing these impurities results in clean carbon fibers. The increased surface roughness of clean carbon fibers helps improve resin wettability, enhances the mechanical interlocking between the carbon fibers and the matrix resin, leading to a tighter bond and improved interfacial adhesion.

[0026] Step 2: In-situ synthesis of PDA coating on carbon fiber surface to obtain PDA modified carbon fiber.

[0027] The specific operation of step two in this embodiment is as follows: Tris (tris(hydroxymethyl)aminomethane) was mixed with deionized water to prepare a Tris solution with a concentration of 1.21 g / 1000 mL. The pH of the Tris solution was adjusted to 8.5 using hydrochloric acid or sodium hydroxide. 2.0 g of dopamine hydrochloride was added and stirred until completely dissolved to obtain a PDA (polydopamine) reaction solution. The clean carbon fiber obtained in step one was added to the PDA reaction solution and stirred at a constant temperature of 25°C for 20 hours to allow dopamine to polymerize in situ on the carbon fiber surface to form a uniform PDA nano-coating. After the reaction was completed, the carbon fiber was removed, the surface residual reaction solution was washed with deionized water, and it was placed in a vacuum drying oven at 60°C for 12 hours to obtain PDA modified carbon fiber.

[0028] In particular, after dopamine undergoes in-situ polymerization on the carbon fiber surface, it can provide abundant active functional groups, making it change from hydrophobic to hydrophilic. Furthermore, PDA polymerization will form nanoparticles on the carbon fiber surface. These nanoparticles protrude on the carbon fiber surface, increasing the surface roughness of the carbon fiber and enhancing its wettability with the matrix resin, thereby enhancing the bonding ability between the carbon fiber and the resin.

[0029] Step 3: In-situ polymerization of PA6 is carried out on the surface of PAD-modified carbon fiber to obtain in-situ PA6-coated PDA-modified carbon fiber.

[0030] The specific operation of step three in this embodiment is as follows: Take 10g of the PDA-modified carbon fiber obtained in step two, 90g of caprolactam and 0.5g of initiator, add them to the reaction vessel, seal it and evacuate it to a vacuum degree of -0.09MPa, heat it to 120℃ and keep it at that temperature for 2 hours to remove moisture by vacuum dehydration.

[0031] The temperature was then raised to 250–260°C and held for 3–5 hours to allow caprolactam to undergo in-situ ring-opening polymerization on the active functional groups of the PDA coating surface, forming a PA6 molecular brush covalently bonded to the carbon fiber. After the reaction was completed, the temperature was cooled to room temperature to obtain in-situ PA6-coated PDA-modified carbon fiber.

[0032] The initiator can be sodium caprolactam.

[0033] Caprolactam is a lactam monomer. During the heating process, the caprolactam monomer reacts with the active functional groups on the PDA coating. As caprolactam is added one by one, PA6 molecular brushes are eventually formed. One end of these molecules is firmly fixed to the carbon fiber, while the other end can freely co-crystallize or entangle with the matrix resin.

[0034] Step 4: Granule preparation.

[0035] The specific operation of step four in this embodiment is as follows: 30g of in-situ PA6-coated PDA-modified carbon fiber obtained in step 3, 70-80g of matrix PA6 resin, and additives were mixed evenly and placed in a high-speed mixer for uniform mixing. Then, the mixture was fed into a twin-screw extruder for melt blending. The temperature of each section of the extruder was controlled at 240℃ and the screw speed was 250rpm. After melt blending, the mixture was extruded, drawn into strands, cooled, and pelletized to obtain carbon fiber reinforced PA6 composite material particles. The particles were then placed in a 120℃ oven and dried for 4 hours to remove moisture, resulting in dry carbon fiber reinforced PA6 composite material granules, which can be used for subsequent thermoplastic molding to prepare gearbox housings.

[0036] The additives include 0.3g antioxidant 1098, 0.2g antioxidant 168 and 0.5g lubricant, and the lubricant can be EBS (vinyl bis-stearamide).

[0037] Step 5: Prepare the reducer housing mold.

[0038] The specific operation of step five in this embodiment is as follows: (1) First, construct the negative Poisson's ratio structure. Please refer to [link / reference]. Figure 4 The construction steps of a negative Poisson's ratio structure are as follows: Sketching a negative Poisson's ratio element: Using Soliworks, first draw a concave hexagon on the front reference plane. The concave hexagon includes parallel and symmetrical top and bottom edges. The bottom edge passes through the origin and is symmetrical about the origin. The two ends of the top and bottom edges are connected by a first and a second hypotenuse, respectively. One end of the first hypotenuse connects to the top edge, and one end of the second hypotenuse connects to the bottom edge. The connection end between the first and second hypotenuses is concave inward. This geometric configuration is the basis for realizing the negative Poisson's ratio effect. When the structure is under tension in one direction, the concave hypotenuse will expand outward, causing the structure to expand in the vertical direction as well. Then, the concave hexagons are arranged in a circular array around the origin, with an array angle of 90° and an array number of 4. All the second hypotenuses of the 4 concave hexagons form an octagon. Delete the cross-shaped lines inside the octagon to complete the sketch of the negative Poisson's ratio element. The sketch of the negative Poisson's ratio element is shown below. Figure 4 As shown in (a); Then, the structure outside the octagon in the sketch of the negative Poisson's ratio element is extruded, and the thin-wall feature is selected. The wall thickness is set to 0.2 mm, and the height is 0.2 mm, forming a structure like... Figure 4 The solid structure shown in (b) is then further modified by drawing a cross inside the octagon to form a shape like... Figure 4 (c) shows the negative Poisson's ratio element; Then, the negative Poisson's ratio elements are arranged in a circular array with one of their center lines as the center of rotation. The array angle is 90°, and the number of arrays is 2. Two negative Poisson's ratio elements form a cross, and its structure is as follows. Figure 4 As shown in (d); A negative Poisson's ratio cell is translated and copied, and the copied negative Poisson's ratio cell is located on the edge of another negative Poisson's ratio cell. Its structure is as follows: Figure 4 As shown in (e); Then, using the replicated negative Poisson's ratio elements as array entities, a circular array is created with 4 elements at a 90° angle, forming a cube with openings on both sides. Two more negative Poisson's ratio elements are then used to fill the openings on both sides of the cube, as shown below. Figure 4 As shown in (f), a structure is formed with a cross formed by two negative Poisson's ratio units as the center and a cube formed by six negative Poisson's ratio units as the outer frame. This structure is a negative Poisson's ratio cell. Finally, the negative Poisson's ratio cells are linearly arrayed along the x, y, and z axes in sequence, with an array size of 2, resulting in the following: Figure 4 (g) shows the negative Poisson's ratio structure.

[0039] This negative Poisson's ratio structure exhibits significant advantages due to its unique deformation mechanism, which expands perpendicular to the stretching direction under tension and contracts under compression. These advantages include strong impact resistance and energy absorption, excellent vibration reduction and noise reduction, high specific strength and specific stiffness, adjustable mechanical properties, and good fatigue fracture toughness. In achieving vibration reduction, its core lies in converting vibrational mechanical energy into elastic energy through the reciprocating expansion-contraction geometric deformation of concave units, thereby efficiently suppressing vibration and achieving vibration reduction and noise reduction.

[0040] (2) Construct a gearbox housing with a sandwich structure. First, the shape and structure of the gearbox housing can be designed according to requirements. In this embodiment, the structure of the gearbox housing is as follows: Figure 2 As shown. In SolidWorks, draw the gearbox housing and use the shell command with a thickness of 8mm to create a sandwich inside the housing, facilitating the filling of the negative Poisson's ratio mechanism.

[0041] (3) Fill the interlayer of the reducer housing with a negative Poisson's ratio structure. Please refer to [link / reference]. Figure 3 The gearbox housing filled with vibration damping structure is obtained.

[0042] (4) Finally, based on the structure of the reducer housing filled with the vibration damping structure, the corresponding reducer housing mold is designed. The reducer housing mold is prepared by printing with 316L stainless steel material as the base through additive manufacturing.

[0043] Step 6: Prepare the housing of the carbon fiber reinforced PA6-based negative Poisson's ratio reducer.

[0044] Step six in this embodiment is performed as follows: The dried carbon fiber reinforced PA6 composite material granules obtained in step four were added to an injection molding machine and molded using a thermoplastic process. The mold used was the reducer housing mold from step five. The injection temperature was controlled at 250℃, the mold temperature at 80℃, and the injection pressure at 120MPa. The compression molding temperature was controlled at 260℃, the pressure at 20MPa, and the holding time was 10 minutes. After molding, the preform was ejected from the mold, and burrs and flash on the surface were removed. It was then placed in a 120℃ oven for aging treatment for 2 hours to eliminate internal stress in the housing. After cooling to room temperature, the carbon fiber reinforced PA6-based negative Poisson's ratio reducer housing was obtained.

[0045] The gearbox housing prepared by the above-mentioned carbon fiber reinforced resin-based negative Poisson's ratio gearbox housing molding method has the advantages of lightweight, high strength, good heat dissipation, noise reduction and anti-icing performance. Combined with the negative Poisson's ratio structure of the gearbox housing sandwich filling, it can effectively attenuate the vibration of the gearbox during operation, further reduce the operating noise, and meet the usage requirements of the gearbox housing. It solves the defects of traditional gearbox housing such as large weight, low precision, high noise and poor vibration reduction effect, and has good practicality and industrialization prospects.

[0046] It should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for molding a carbon fiber reinforced resin-based negative Poisson's ratio reducer housing, characterized in that, Includes the following steps: Step 1: Carbon fiber pretreatment to obtain clean carbon fiber; Step 2: In-situ synthesis of PDA coating on carbon fiber surface to obtain PDA-modified carbon fiber; Step 3: PA6 is polymerized in situ on the surface of PAD-modified carbon fiber to obtain in situ PA6-coated PDA-modified carbon fiber. Step 4, Granule preparation: The in-situ PA6-coated PDA-modified carbon fiber, matrix PA6 resin and additives obtained in step 3 are mixed evenly and then processed to form carbon fiber reinforced PA6 composite material granules. The moisture is removed to obtain dry carbon fiber reinforced PA6 composite material granules. Step 5, prepare the reducer housing mold: First, construct a negative Poisson's ratio structure, then construct a reducer housing with a sandwich structure, then fill the sandwich structure of the reducer housing with the negative Poisson's ratio structure to obtain a reducer housing filled with a vibration damping structure, and finally prepare the reducer housing mold by additive manufacturing. Step 6: Prepare carbon fiber reinforced PA6-based negative Poisson's ratio reducer housing: Using the reducer housing mold from Step 5, inject the dried carbon fiber reinforced PA6 composite material granules obtained in Step 4 to obtain the carbon fiber reinforced PA6-based negative Poisson's ratio reducer housing.

2. The method for molding a carbon fiber reinforced resin-based negative Poisson's ratio reducer housing according to claim 1, characterized in that, The steps for constructing the negative Poisson's ratio structure in step five are as follows: To sketch a negative Poisson's ratio element: First, draw a concave hexagon, which includes a parallel and symmetrical top and bottom edge. The two ends of the top and bottom edges are connected by a first and a second hypotenuse, respectively, with the connecting ends of the first and second hypotenuses facing inward. Then, arrange the concave hexagon in a circular array with an array angle of 90° and an array number of 4. All the second hypotenuses form an octagon. Delete the lines inside the octagon to complete the sketch of the negative Poisson's ratio element. Then, the sketch of the negative Poisson's ratio element is extruded and the thin-walled feature is selected. The octagon is filled with a cross to form the negative Poisson's ratio element. Then, the negative Poisson's ratio elements are arranged in a circular array with one of their center lines as the center of rotation. The array angle is 90° and the number of arrays is 2. The two negative Poisson's ratio elements form a cross. Centered on the aforementioned cross, six negative Poisson's ratio units are arranged to form a cube frame. The cube frame is connected to the edge of the cross to form a negative Poisson's ratio structural cell. The negative Poisson's ratio structure is obtained by linearly arranging the cell elements of the negative Poisson's ratio structure along the x, y, and z axes in sequence, with a number of arrays of 2.

3. The method for molding a carbon fiber reinforced resin-based negative Poisson's ratio reducer housing according to claim 1, characterized in that, The specific steps of step one are as follows: Take carbon fiber, add it to a mixture of acetone and deionized water, soak it at room temperature, stirring regularly during the process, then wash it repeatedly until there is no acetone residue, dry it, remove impurities from the surface of the carbon fiber, and obtain clean carbon fiber.

4. The method for molding a carbon fiber reinforced resin-based negative Poisson's ratio reducer housing according to claim 1, characterized in that, The specific steps of step two are as follows: Prepare a Tris solution, adjust the pH to 8.5, add dopamine hydrochloride, and stir until completely dissolved to obtain a PDA reaction solution; The clean carbon fiber obtained in step one is added to the PDA reaction solution and stirred to allow dopamine to polymerize in situ on the carbon fiber surface to form a uniform PDA nano-coating. After the reaction is complete, the carbon fiber is removed, the residual reaction solution on the surface is cleaned, and after drying, PDA-modified carbon fiber is obtained.

5. The method for molding a carbon fiber reinforced resin-based negative Poisson's ratio reducer housing according to claim 1, characterized in that, The specific steps of step three are as follows: Take PDA-modified carbon fiber, caprolactam and initiator, add them to the reaction vessel, seal it and evacuate it. Heat it to 120℃ and keep it at that temperature for 2 hours to remove moisture by vacuum dehydration. The temperature was then increased to allow caprolactam to undergo in-situ ring-opening polymerization on the active functional groups of the PDA coating surface, forming a PA6 molecular brush covalently bonded to the carbon fiber. After the reaction was completed, the mixture was cooled to room temperature to obtain in-situ PA6-coated PDA-modified carbon fiber.

6. The method for molding a carbon fiber reinforced resin-based negative Poisson's ratio reducer housing according to claim 5, characterized in that, The initiator is sodium caprolactam.

7. The method for molding a carbon fiber reinforced resin-based negative Poisson's ratio reducer housing according to claim 1, characterized in that, The specific steps of step four are as follows: In-situ PA6-coated PDA-modified carbon fiber, matrix PA6 resin, and additives are mixed evenly and fed into a twin-screw extruder for melt blending. After melt blending, the mixture is extruded, drawn into strands, cooled, and pelletized to obtain carbon fiber reinforced PA6 composite material particles. Then, the particles are dried to remove moisture and obtain dry carbon fiber reinforced PA6 composite material granules.

8. The method for molding a carbon fiber reinforced resin-based negative Poisson's ratio reducer housing according to claim 7, characterized in that, The additives include antioxidant 1098, antioxidant 168, and lubricant.

9. A carbon fiber reinforced resin-based negative Poisson's ratio reducer housing, characterized in that, The housing of the carbon fiber reinforced resin-based negative Poisson's ratio reducer is prepared according to any one of claims 1 to 8.

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