A badminton racket rod structure and a production process thereof

Abstract

The present application belongs to the technical field of badminton racket, and particularly relates to a badminton racket rod structure and a production process thereof. The present application adopts a combination scheme of a radial three-layer differentiated composite structure and an axial gradient performance design. From inside to outside in the radial direction, a reinforcing framework layer, a middle functional layer and an outer reinforcing layer are arranged, and each layer respectively undertakes the core functions of torsion resistance and shock absorption, rigid and tough balance and rigid enhancement. Different weaves and ply angle designs are matched to realize performance partition customization of different regions of the racket rod, so that the contradiction that rigidity and shock resistance cannot be considered together is solved.

Description

Technical Field

[0001] This invention belongs to the field of badminton racket technology, specifically relating to a badminton racket shaft structure and its manufacturing process. Background Technology

[0002] The badminton racket shaft is the core load-bearing component of the badminton racket, directly determining the racket's rigidity, torsional resistance, shock absorption, and hitting feel. It is a key factor affecting racket performance. Therefore, an improved badminton racket shaft structure and its manufacturing process have been designed.

[0003] Conventional racket shafts are mostly made of unidirectional carbon fiber rolled in the same direction, with a single layer angle, which cannot balance rigidity and shock absorption. Furthermore, high rigidity layers lead to poor shock absorption, causing hand vibration when hitting the ball. Adding a shock-absorbing structure would significantly reduce the rigidity of the racket shaft, resulting in problems such as insufficient power transfer and ball control accuracy. Summary of the Invention

[0004] To address the aforementioned shortcomings in the existing technology, this invention provides a badminton racket shaft structure and its manufacturing process to solve the problems mentioned in the background technology.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A manufacturing process for a badminton racket shaft structure includes the following steps: S1: Using 3D printing technology, continuous carbon fiber is used as the reinforcing phase and thermoplastic resin is used as the matrix. According to the preset gradient porosity, gradient wall thickness and spiral reinforcing rib structure, a hollow tubular reinforcing skeleton is printed. At the same time, the handle connection section and frame connection section at both ends are printed in one piece. S2: The reinforced skeleton obtained in step S1 is subjected to surface plasma treatment with a treatment power of 80-120W and a treatment time of 5-15min to obtain a surface-activated skeleton. S3: Fix the surface-activated skeleton onto the rotating mold mandrel of the horizontal winding machine. First, the mixed fiber yarn is continuously impregnated with thermosetting resin in the vacuum impregnation chamber, and then wound around the outer wall of the skeleton at a preset weaving angle to form the intermediate functional layer preform. Then, the high modulus carbon fiber yarn is continuously impregnated with thermosetting resin in the vacuum impregnation chamber, and wound around the outer wall of the intermediate functional layer preform at a preset layup angle to form the outer reinforcement layer preform, thus obtaining the racket shaft preform. S4: The preform of the racket arm obtained in step S3, together with the mold mandrel, is sent into the microwave curing equipment. The curing temperature is set to increase gradually from the near end to the far end along the racket arm axis. The racket arm is then cured in stages. After curing, the racket arm is cooled to room temperature in the furnace and demolded to obtain the racket arm blank. S5: The rough shaft blank is ground, polished, cleaned and dried to obtain the finished badminton racket shaft.

[0006] Preferably, in step S1, the thermoplastic resin is any one of polyetheretherketone, polyamide, and polyphenylene sulfide, the printing temperature of 3D printing is 280-400℃, the fill rate gradually increases from 55%-70% to 85%-95% along the axial direction from the proximal end to the distal end, and the printing layer thickness is 0.05-0.15mm.

[0007] Preferably, in step S3, the vacuum degree of the vacuum impregnation chamber is -0.08-0.1 MPa, the thermosetting resin used for impregnation is any one of epoxy resin and phenolic resin, and the impregnation temperature is 35-50℃; the winding tension of the hybrid fiber yarn is 10-20 N, and the winding speed is 25 m / min; the winding tension of the high modulus carbon fiber yarn is 15-25 N, and the winding speed is 36 m / min.

[0008] Preferably, in step S4, the microwave frequency of the microwave curing device is 2450MHz, and the specific process of gradient curing is as follows: the near-end curing temperature is 120-130℃, and the holding time is 10-15min; the middle-end curing temperature is 140-150℃, and the holding time is 15-20min; the far-end curing temperature is 160-170℃, and the holding time is 20-25min; the vacuum degree is maintained at -0.06~-0.08MPa throughout the curing process.

[0009] A badminton racket shaft structure includes a hollow tubular shaft body, wherein the shaft body is provided with an integrally formed reinforcing skeleton layer, an intermediate functional layer and an outer reinforcing layer in a radial direction from the inside to the outside; The reinforcing skeleton layer is an integrally formed porous tubular skeleton. Along the axial direction of the racket body, from the proximal end near the handle to the far end near the frame, the porosity of the reinforcing skeleton layer decreases in a gradient, while the wall thickness increases in a gradient. The intermediate functional layer is a hybrid fiber-reinforced thermosetting resin matrix layer, which covers the outer wall of the reinforcing skeleton layer; The outer reinforcing layer is a carbon fiber reinforced thermosetting resin matrix layer, which covers the outer wall of the intermediate functional layer.

[0010] Preferably, the proximal porosity of the reinforcing skeleton layer is 30%-45%, the distal porosity is 5%-15%, the proximal tube wall thickness is 0.2mm-0.4mm, and the distal tube wall thickness is 0.6mm-1.0mm.

[0011] Preferably, the inner wall of the reinforcing skeleton layer is provided with a spiral reinforcing rib extending along the axial direction, and the spiral reinforcing rib is integrally formed with the reinforcing skeleton layer by 3D printing.

[0012] Preferably, the intermediate functional layer is a two-dimensional woven layer in which basalt fiber and carbon fiber are mixed and woven in a weight ratio of 1:1 to 3:1, the weaving angle of the two-dimensional woven layer is ±30° to ±45°, and the thickness of the intermediate functional layer is 0.3 mm to 0.6 mm.

[0013] Preferably, the outer reinforcing layer is a high-modulus carbon fiber layup, with adjacent layups arranged alternately at an angle of 0° to ±15°, and the thickness of the outer reinforcing layer is 0.4 mm to 0.8 mm.

[0014] Preferably, the reinforcing skeleton layer has a handle connecting section integrally formed at the proximal end and a frame connecting section integrally formed at the distal end. The outer walls of both the handle connecting section and the frame connecting section are provided with annular anti-detachment grooves, which are integrally formed with the reinforcing skeleton layer.

[0015] Compared with the prior art, the present invention has the following advantages: 1. This invention adopts a combination of radial three-layer differentiated composite structure and axial gradient performance design. Radially from the inside out, there are a reinforcing skeleton layer, an intermediate functional layer, and an outer reinforcing layer. Each layer undertakes the core functions of anti-torsion and shock absorption, rigidity and toughness balance, and rigidity enhancement. With different weaving and layering angle design, the performance zoning customization of different areas of the racket shaft is realized, thereby solving the contradiction that rigidity and shock absorption cannot be taken into account at the same time. 2. This invention, through the high porosity and thin-walled structure design of the near end (handle end) of the enhanced skeleton layer, combined with the damping characteristics of the thermoplastic resin matrix, can effectively attenuate the impact vibration of the ball and solve the problem of hand tremors when hitting the ball. At the same time, the middle functional layer adopts a hybrid structure of basalt fiber and carbon fiber, which utilizes the excellent toughness, shock absorption and impact resistance of basalt fiber to further improve the damping and shock absorption effect, and avoids the rigidity loss caused by additional shock absorption structures. 3. This invention significantly improves the bending rigidity and torsional performance of the front end of the racket shaft by enhancing the low porosity and thick wall design of the far end of the reinforced skeleton layer (frame end), combined with the integrally formed spiral reinforcing ribs on the inner wall, reducing racket shaft deformation during impact. The outermost layer is set with a high modulus carbon fiber outer reinforcement layer, which makes full use of the mechanical properties of the outer layer with the greatest stress when the hollow tube is bent, maximizes the axial strength advantage of high modulus carbon fiber, further improves the overall bending modulus and structural stability of the racket shaft, ensures the accurate and efficient transmission of hitting power, and thus solves the problems of insufficient power generation and dissipation and insufficient ball control accuracy. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the three-dimensional structure of a badminton racket shaft provided by the present invention; Figure 2 This is a cross-sectional view of the front view portion of the badminton racket shaft provided by the present invention; Figure 3 This is a schematic diagram of the badminton racket shaft manufacturing process of the present invention. The reference numerals in the accompanying drawings of the instruction manual include: 1. racket shaft body; 2. reinforcing rib; 3. reinforcing skeleton layer; 4. intermediate functional layer; 5. racket frame connecting section; 6. racket handle connecting section; 7. annular anti-detachment groove; and 8. outer reinforcing layer. Detailed Implementation

[0017] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0018] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual images. They should not be construed as limiting the scope of this patent. To better illustrate the embodiments of the present invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0019] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present patent. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0020] In the description of this invention, unless otherwise explicitly specified and limited, the term "connection" or similar designation indicating a connection between components should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0021] like Figure 1-2The invention discloses a manufacturing process for a badminton racket shaft structure. The invention includes a reinforcing skeleton layer 3, an intermediate functional layer 4, and an outer reinforcing layer 8. The reinforcing skeleton layer 3, along the axial direction of the racket shaft body 1, exhibits a gradient decrease in porosity from the proximal end near the handle to the distal end near the frame, while the wall thickness increases in a gradient manner. Specifically, the proximal end has a porosity of 30%–45% and a wall thickness of 0.2 mm–0.4 mm; the distal end has a porosity of 5%–15% and a wall thickness of 0.6 mm–1.0 mm. The high porosity and thin-walled design at the proximal end (grip end) effectively attenuates vibrations during impact, improving grip feel and shock absorption, while also reducing proximal weight and optimizing the overall shaft weight distribution. The low porosity and thick-walled design at the distal end (frame end) significantly improves the bending rigidity and torsional resistance of the racket shaft tip, reducing shaft deformation during impact and ensuring accurate power transmission and explosive output. The inner wall of the reinforcing skeleton layer 3 is provided with a spiral reinforcing rib 2 that extends continuously along the axial direction. The spiral reinforcing rib 2 and the reinforcing skeleton layer 3 are integrally formed by 3D printing without the need for subsequent secondary processing. The spiral reinforcing rib 2 can significantly improve the bending resistance, fatigue resistance and torsion resistance of the hollow tube without significantly increasing the weight of the racket shaft, and prevent the tube from buckling and deforming when hitting the ball. At the same time, the spiral structure can distribute the force and avoid the tube cracking caused by stress concentration. The reinforcing skeleton layer 3 has a handle connecting section 6 integrally formed at its proximal end and a frame connecting section 5 integrally formed at its distal end. Both the handle connecting section 6 and the frame connecting section 5 have annular anti-detachment grooves 7 on their outer walls. The annular anti-detachment grooves 7 are integrally formed with the reinforcing skeleton layer 3. The handle connecting section 6 is used for precise assembly with the racket grip, and the frame connecting section 5 is used for fixing with the T-joint of the racket frame. The annular anti-detachment grooves 7 can form a fitting structure with the assembly components. Combined with the bonding process, this solves the problem of the racket shaft, handle, and frame becoming loose or rotating relative to each other during use. The integral design avoids stress concentration caused by subsequent machining and welding, greatly improving the fatigue life of the connecting parts. The intermediate functional layer 4 is a hybrid fiber-reinforced thermosetting resin matrix layer, uniformly covering the outer wall of the reinforcing skeleton layer 3. It is used to balance the rigidity of the racket shaft and improve the shock absorption effect. The thickness is 0.3mm to 0.6mm. The intermediate functional layer 4 is a two-dimensional woven layer made of basalt fiber and carbon fiber mixed in a weight ratio of 1:1 to 3:1. The weaving angle of the two-dimensional woven layer is ±30° to ±45°. Since basalt fiber has excellent toughness, shock absorption and impact resistance, the higher the proportion of basalt fiber, the better the shock absorption feel, which is suitable for defensive and balanced rackets. The higher the proportion of carbon fiber, the stronger the rigidity, which is suitable for offensive rackets. By weaving at different angles, the axial strength and circumferential torsional performance of the racket shaft can be optimized simultaneously to match the multi-directional force requirements when hitting the shuttlecock. The outer reinforcing layer 8 is a high-modulus carbon fiber reinforced thermosetting resin matrix layer, which is uniformly coated on the outer wall of the intermediate functional layer 4, with a thickness of 0.4mm to 0.8mm. The outer reinforcing layer 8 is formed by winding high-modulus carbon fiber yarn. The modulus of high-modulus carbon fiber is ≥400GPa and the tensile strength is ≥4900MPa. It can maximize the axial strength advantage of carbon fiber. When the hollow tube is bent, the outer structure bears the greatest stress. By placing high-modulus carbon fiber on the outermost layer, the material properties can be fully utilized, which can significantly improve the overall bending modulus, fatigue resistance and structural stability of the racket shaft, reduce the deformation attenuation of the racket shaft after repeated hitting, and extend the service life of the racket.

[0022] A manufacturing process for a badminton racket shaft structure includes the following steps: S1: Using 3D modeling software, a 3D model of the reinforcing skeleton with gradient porosity, gradient wall thickness, spiral reinforcing ribs 2, end connection sections, and annular anti-detachment grooves 7 is designed based on the performance requirements of the racket shaft. After slicing the model and setting the corresponding printing parameters, it is imported into a continuous fiber 3D printing device. Using continuous fiber reinforced fused deposition modeling (FDM) technology, with continuous carbon fiber as the reinforcing phase and thermoplastic resin as the matrix, a hollow tubular reinforcing skeleton is printed according to the preset model. Simultaneously, the handle connection sections 6, frame connection sections 5, and the annular anti-detachment grooves 7 on the outer wall are printed integrally. The entire molding process requires no... The mold is seamless and requires no secondary processing, avoiding interface defects. The thermoplastic resin is any one of polyetheretherketone (PEEK), polyamide, or polyphenylene sulfide (PPS). The printing temperature is set according to the resin selection: 280-300℃ for polyamide, 300-350℃ for PPS, and 380-400℃ for PEEK. The printing fill rate gradually increases from 55%-70% to 85%-95% along the axial direction of the printing rod, precisely corresponding to the decreasing porosity gradient in the structural design. Porosity = 1 - fill rate. The printing layer thickness is set to 0.05-0.15mm to ensure the surface accuracy and structural density of the printed parts. S2: The reinforced skeleton obtained in step S1 is subjected to low-temperature plasma surface treatment with a treatment power of 80-120W and a treatment time of 5-15min. The treatment process is carried out in an argon atmosphere, thereby etching a micro-nano scale rough structure on the skeleton surface and introducing active functional groups such as hydroxyl and carboxyl groups on the surface, which greatly improves the wettability and adhesion of the skeleton surface, providing a strong bonding interface for the subsequent coating molding of composite layers, and thus solving the problems of low surface energy, poor interfacial bonding force with subsequent thermosetting resins, and easy delamination of 3D printed thermoplastic resin skeletons. S3: The surface-activated skeleton is coaxially fixed on the rotating mold mandrel of the horizontal winding machine. The inner diameter of the mold mandrel is precisely matched with that of the reinforcing skeleton to ensure that the skeleton does not move during the winding process and the coaxiality deviation is ≤0.02mm. Then, the composite layer is wound and formed in two steps. S3.1: First, the mixed fiber yarns blended according to a preset ratio are fed into the vacuum impregnation chamber to complete the continuous vacuum impregnation of thermosetting resin. Then, using a horizontal winding machine, the yarns are evenly wound onto the outer wall of the skeleton at a preset weaving angle of ±30°-±45° to form the intermediate functional layer 4 preform. The vacuum degree of the vacuum impregnation chamber is -0.08~-0.1MPa, which can fully expel air from the inside of the fiber yarns, ensuring that the thermosetting resin completely impregnates each fiber filament and avoiding defects such as air bubbles and dry yarn. The thermosetting resin used for impregnation is either epoxy resin or phenolic resin. The impregnation temperature is controlled at 35-50℃. This temperature range allows the resin to maintain a suitable viscosity, ensuring sufficient fiber impregnation without premature curing that would affect subsequent molding. The winding tension of the mixed fiber yarns is controlled at 10-20N, and the winding speed is 25m / min. Tension control ensures that the yarns are tightly attached to the outer wall of the skeleton, preventing yarn slack and uneven layering, while also preventing excessive tension from breaking the fibers. S3.2: Then, the high-modulus carbon fiber yarn is fed into the vacuum impregnation chamber and continuously impregnated with thermosetting resin under the same vacuum environment and impregnation temperature. It is then uniformly wound around the outer wall of the intermediate functional layer 4 preform at a preset layup angle to form the outer reinforcing layer 8 preform. The winding tension of the high-modulus carbon fiber yarn is controlled at 15-25N and the winding speed is 36m / min. Compared with hybrid fibers, a higher winding tension is used to match the material characteristics of high-modulus carbon fiber, ensure the density of the layup, maximize the axial mechanical properties of carbon fiber, and finally obtain the racket shaft preform. S4: The racket shaft preform obtained in step S3, along with the mold mandrel, is fed into a microwave curing device. A vacuum environment is maintained throughout the curing process. The curing temperature is set in a gradient increase from the proximal end to the distal end along the racket shaft axis for segmented gradient curing. The microwave frequency of the curing device is 2450MHz, and the vacuum degree is maintained at -0.06~-0.08MPa throughout the curing process. This continuously removes small molecule volatiles and residual air generated during curing, further improving the density of the composite material. The specific gradient curing process consists of three independently controlled temperature segments: Proximal end, i.e., handle connection section 6: curing temperature is 120-130℃, heat preservation for 10-15min, low-temperature initial gelation, fixing the layer structure, and avoiding over-curing of thin-walled sections; The middle section, i.e., the middle area of ​​the main body of the stick: the curing temperature is 140-150℃, and the heat is maintained for 15-20 minutes to complete the main cross-linking and curing reaction of the resin and establish the basic mechanical properties. Remote shooting frame connecting section 5: The curing temperature is 160-170℃, and the heat preservation time is 20-25 minutes. The high temperature achieves complete resin curing, ensuring the curing degree and structural stability of the thick-walled section.

[0023] After curing, furnace cooling is used to avoid stress concentration caused by rapid cooling and to prevent deformation and cracking of the drumstick. After cooling to room temperature, the drumstick blank is demolded to obtain a complete drumstick blank. S5: After demolding, the rough blank of the racket shaft is ground, polished, washed and dried to obtain the finished badminton racket shaft.

[0024] Example 1: The enhanced skeleton is pre-designed using 3D modeling software. The skeleton is a hollow tubular structure with a total axial length of 220mm. Along the axial direction, from the proximal end (handle end) to the distal end (frame end), the porosity gradually decreases from 40% to 10%, and the tube wall thickness gradually increases from 0.3mm to 0.8mm. The inner wall is integrally formed with a spiral reinforcing rib with a pitch of 20mm and a rib height of 0.2mm. The handle connection section, frame connection section, and annular anti-detachment groove on the outer wall are integrally formed at both ends. A continuous fiber-reinforced fused deposition modeling (FDM) 3D printing process was adopted, using continuous carbon fiber as the reinforcing phase and polyamide (PA) as the thermoplastic resin matrix. The printing temperature was 290℃, and the printing fill rate gradually increased from 60% at the proximal end to 90% at the distal end along the axial direction. The printing layer thickness was 0.1mm, and a complete reinforced skeleton was obtained by printing. The obtained reinforced skeleton was placed in an argon atmosphere plasma treatment device with a treatment power of 100W and a treatment time of 10min to complete surface etching and introduction of active functional groups, resulting in a surface-activated skeleton. The surface-activated skeleton was coaxially fixed on the rotating mold mandrel of a horizontal winding machine to ensure that the mold mandrel and the inner hole size of the skeleton were precisely matched, with a coaxiality deviation of ≤0.02mm. A hybrid fiber yarn, a 2:1 weight blend of basalt fiber and carbon fiber, was fed into a vacuum impregnation chamber. The vacuum level was controlled at -0.09 MPa. Epoxy resin was used as the thermosetting resin, and the impregnation temperature was 40°C. After continuous vacuum impregnation, the yarn was uniformly wound onto the outer wall of the skeleton at a braiding angle of ±37°, with a winding tension of 15 N and a winding speed of 25 m / min, forming a 0.45 mm thick intermediate functional layer preform. High-modulus carbon fiber yarn with a modulus of 450 GPa and a tensile strength of 5000 MPa was then fed into a vacuum impregnation chamber with the same parameters for resin impregnation at 0° and ±12° intervals. The layup angle is adjusted, and the material is evenly wound around the outer wall of the intermediate functional layer preform. The winding tension is 20N, the winding speed is 36m / min, and the outer reinforcing layer preform with a thickness of 0.6mm is formed, resulting in the racket shaft preform. The racket shaft preform, along with the mold mandrel, is then fed into a microwave curing device. The microwave frequency is set to 2450MHz, and the vacuum degree is maintained at -0.07MPa throughout the curing process. A segmented gradient curing process is adopted: near-end curing temperature 125℃, holding temperature 12min; middle-end curing temperature 145℃, holding temperature 18min; far-end curing temperature 165℃, holding temperature 22min. After curing, the material is cooled to room temperature in the oven and demolded to obtain a racket shaft blank. The racket shaft blank is then subjected to surface grinding, polishing, ultrasonic cleaning with anhydrous ethanol, and hot air drying at 80℃ to obtain the finished balanced badminton racket shaft. In another embodiment: Based on Example 1, to further improve shock absorption performance and reduce the overall weight of the racket shaft, foaming material can be injected into the inner cavity of the reinforcing frame obtained in step S1. Specifically: during the preparation in step S1, a pre-reserved injection port is made in the reinforcing frame, and then the connection section between the racket handle and the racket frame is temporarily sealed. Before injecting the foaming precursor, a layer of water-soluble release agent (such as polyvinyl alcohol) is uniformly coated on the inner wall of the reinforcing frame. After drying, a temporary barrier layer is formed to prevent the precursor from seeping out from the pores of the frame. Epoxy resin-based foaming precursor (containing epoxy resin, curing agent, and foaming agent azodicarbonamide, with a foaming agent mass fraction of 1.5%~3.0%) is injected into the inner cavity of the skeleton through the reserved injection port. After filling, the skeleton is sealed. Then, the reinforced skeleton is placed in an oven at 90~110℃ for constant temperature foaming for 20~30 minutes. During the foaming process, the skeleton axis is kept horizontal to ensure that the foam expands evenly and fits tightly against the inner wall. After foaming, the skeleton is naturally cooled to room temperature to obtain a closed-cell foamed core layer with a density of 0.2~0.4 g / cm³ and a foaming rate of 25%~40%. The reinforced skeleton with the foamed core layer is then subjected to subsequent plasma treatment and winding molding. The introduction of the foamed core layer can further absorb the impact vibration, improve the damping characteristics, and hardly increase the weight of the racket shaft, achieving a synergistic optimization of lightweight and high shock absorption.

[0025] Comparative Example 1: T700 carbon fiber unidirectional prepreg and epoxy resin matrix were selected. The thickness of a single prepreg sheet was 0.12 mm. The carbon fiber prepreg was laid up in the same direction at 0° and rolled on a steel mold mandrel of the same specifications as in Example 1. The total layup thickness was 1.4 mm. After rolling, heat shrink tape was evenly wrapped around the preform to obtain the racket shaft preform. The preform was sent into an autoclave and a constant temperature curing process was adopted. The curing temperature was 150°C, the holding time was 30 min, and the curing pressure was 0.6 MPa. After curing, the preform was cooled to room temperature in the furnace, demolded, and the heat shrink tape was removed to obtain the racket shaft blank. The surface grinding, polishing, cleaning, and drying processes were the same as in Example 1 to obtain the finished badminton racket shaft. The total length and basic inner and outer diameter of the racket shaft were completely consistent with those in Example 1.

[0026] Comparative Example 2: Lacking axial gradient performance design, the remaining raw materials and basic structure are consistent with Example 1. The specific process is as follows: A hollow tubular reinforcing skeleton was prepared using 3D printing technology, with a continuous carbon fiber reinforced polyamide matrix. The porosity of the skeleton was uniformly 25% throughout, and the wall thickness was uniformly 0.55 mm throughout. No spiral reinforcing ribs were set on the inner wall. The printing temperature was 290℃, and the printing layer thickness was 0.1 mm, resulting in a reinforcing skeleton with uniform wall thickness and porosity. The basic dimensions were the same as in Example 1. The same plasma treatment process as in Example 1 was used to obtain a surface-activated skeleton. The same winding process for the intermediate functional layer and outer reinforcing layer as in Example 1 was used to obtain the racket shaft preform. A constant temperature curing process was used throughout, with a curing temperature of 150℃, a holding time of 30 min, a microwave frequency of 2450MHz, and a vacuum degree of -0.07MPa. After curing, the racket shaft was cooled in the furnace and demolded to obtain a racket shaft blank. The same post-processing process as in Example 1 was used to obtain the finished badminton racket shaft.

[0027] Comparative Example 3: The plasma surface treatment process is missing, but the other raw materials, structural design, and process parameters are completely consistent with Example 1. The specific preparation process is as follows: The plasma surface treatment process in Example 1 is omitted. The 3D-printed reinforcing skeleton is directly subjected to the subsequent winding molding process. The raw materials, parameters and operation procedures of the remaining S1, S3, S4 and S5 are completely consistent with those in Example 1, and the finished badminton racket shaft is obtained.

[0028] The badminton racket shafts prepared in Example 1, Comparative Examples 1, 2, and 3 were subjected to performance tests in a standard environment of 25°C and 50% relative humidity. The test items, execution standards, and test results are as follows, verifying the core advantages of the technical solution of this invention: Flexural modulus: According to GB / T1449-2005 "Test Method for Flexural Properties of Fiber Reinforced Plastics", the three-point bending method was used for testing, with a span of 100 mm and a loading speed of 2 mm / min. Torsional strength: Tested using a torsion testing machine with a clamping length of 150 mm and a torsion speed of 2° / min, and the maximum breaking torque was recorded; Shock absorption performance: The impact vibration attenuation rate was tested using an accelerometer. The same impact load was applied to the racket frame end while the handle end was fixed, and the vibration acceleration attenuation rate was recorded within 10ms. The higher the attenuation rate, the better the shock absorption performance. Interlaminar shear strength: Tested according to GB / T1450.1-2005 "Test Method for Interlaminar Shear Strength of Fiber Reinforced Plastics" to characterize the interfacial bonding performance of composite materials; Fatigue life: Using a fatigue testing machine, a 30% ultimate bending load was applied at a cycle frequency of 5Hz, and the number of cycles until the racket shaft cracked was recorded.

[0029] The test results are as follows: Compared with Comparative Example 1, Embodiment 1 of the present invention significantly improves the bending modulus, torsional strength, and vibration attenuation rate, resolving the contradiction of "rigidity and shock absorption being mutually exclusive" in traditional racket shafts. At the same time, by adjusting the fiber ratio and gradient parameters, performance customization can be achieved for different scenarios such as offense, balance, and defense, verifying the core advantages of the radial three-layer differentiated composite structure and axial gradient performance design of the present invention. Comparative Example 2, lacking axial gradient porosity, gradient wall thickness design, and spiral reinforcing rib structure, exhibits significantly lower rigidity, shock absorption, and fatigue resistance compared to Example 1. This demonstrates that the axial gradient design of the present invention is a key technology for achieving customized performance of the racket shaft and balancing rigidity and shock absorption. Comparative Example 3, due to the lack of plasma surface treatment, showed a significant decrease in interlaminar shear strength and fatigue life, and was prone to interlaminar delamination failure. This proves that the plasma surface treatment process of the present invention is the core process for solving the problem of poor interfacial bonding between the thermoplastic skeleton and the thermosetting composite layer, and ensuring the stability and service life of the racket shaft structure.

[0030] The above are merely embodiments of the present invention. The circuits, electronic components, and modules involved are all prior art, fully achievable by those skilled in the art, and require no further explanation. The scope of protection in this application does not involve improvements to the software and methods. Commonly known structures and characteristics in the solutions are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all prior art in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A manufacturing process for a badminton racket shaft structure, characterized in that, Includes the following steps: S1: Using 3D printing technology, continuous carbon fiber is used as the reinforcing phase and thermoplastic resin is used as the matrix. According to the preset gradient porosity, gradient wall thickness and spiral reinforcing rib structure, a hollow tubular reinforcing skeleton is printed. At the same time, the handle connection section and frame connection section at both ends are printed in one piece. S2: The reinforced skeleton obtained in step S1 is subjected to surface plasma treatment with a treatment power of 80-120W and a treatment time of 5-15min to obtain a surface-activated skeleton. S3: Fix the surface-activated skeleton onto the rotating mold mandrel of the horizontal winding machine. First, the mixed fiber yarn is continuously impregnated with thermosetting resin in the vacuum impregnation chamber, and then wound around the outer wall of the skeleton at a preset weaving angle to form the intermediate functional layer preform. Then, the high modulus carbon fiber yarn is continuously impregnated with thermosetting resin in the vacuum impregnation chamber, and wound around the outer wall of the intermediate functional layer preform at a preset layup angle to form the outer reinforcement layer preform, thus obtaining the racket shaft preform. S4: The preform of the racket arm obtained in step S3, together with the mold mandrel, is sent into the microwave curing equipment. The curing temperature is set to increase gradually from the near end to the far end along the racket arm axis. The racket arm is then cured in stages. After curing, the racket arm is cooled to room temperature in the furnace and demolded to obtain the racket arm blank. S5: The rough shaft blank is ground, polished, cleaned and dried to obtain the finished badminton racket shaft.

2. The manufacturing process of a badminton racket shaft structure according to claim 1, characterized in that, In step S1, the thermoplastic resin is any one of polyetheretherketone, polyamide, and polyphenylene sulfide. The printing temperature of 3D printing is 280-400℃, the fill rate gradually increases from 55%-70% to 85%-95% along the axial direction from the proximal end to the distal end, and the printing layer thickness is 0.05-0.15mm.

3. The manufacturing process of a badminton racket shaft structure according to claim 1, characterized in that, In step S3, the vacuum degree of the vacuum impregnation chamber is -0.08-0.1MPa, the thermosetting resin used for impregnation is any one of epoxy resin and phenolic resin, and the impregnation temperature is 35-50℃; the winding tension of the hybrid fiber yarn is 10-20N, and the winding speed is 25m / min; the winding tension of the high modulus carbon fiber yarn is 15-25N, and the winding speed is 36m / min.

4. The manufacturing process of a badminton racket shaft structure according to claim 1, characterized in that, In step S4, the microwave frequency of the microwave curing equipment is 2450MHz, and the specific process of gradient curing is as follows: the near-end curing temperature is 120-130℃, and the holding time is 10-15min; the middle-end curing temperature is 140-150℃, and the holding time is 15-20min; the far-end curing temperature is 160-170℃, and the holding time is 20-25min; the vacuum degree is maintained at -0.06~-0.08MPa throughout the curing process.

5. A badminton racket shaft structure, characterized in that, The racket includes a hollow tubular racket body, which is provided with an integrally formed reinforcing skeleton layer, an intermediate functional layer and an outer reinforcing layer in a radial direction from the inside to the outside. The reinforcing skeleton layer is an integrally formed porous tubular skeleton. Along the axial direction of the racket body, from the proximal end near the handle to the far end near the frame, the porosity of the reinforcing skeleton layer decreases in a gradient, while the wall thickness increases in a gradient. The intermediate functional layer is a hybrid fiber-reinforced thermosetting resin matrix layer, which covers the outer wall of the reinforcing skeleton layer; The outer reinforcing layer is a carbon fiber reinforced thermosetting resin matrix layer, which covers the outer wall of the intermediate functional layer.

6. A badminton racket shaft structure according to claim 5, characterized in that, The proximal porosity of the reinforcing skeleton layer is 30%–45%, the distal porosity is 5%–15%, the proximal wall thickness is 0.2 mm–0.4 mm, and the distal wall thickness is 0.6 mm–1.0 mm.

7. A badminton racket shaft structure according to claim 5, characterized in that, The inner wall of the reinforcing skeleton layer is provided with spiral reinforcing ribs extending along the axial direction, and the spiral reinforcing ribs are integrally formed with the reinforcing skeleton layer by 3D printing.

8. A badminton racket shaft structure according to claim 5, characterized in that, The intermediate functional layer is a two-dimensional woven layer in which basalt fiber and carbon fiber are mixed and woven in a weight ratio of 1:1 to 3:

1. The weaving angle of the two-dimensional woven layer is ±30° to ±45°, and the thickness of the intermediate functional layer is 0.3mm to 0.6mm.

9. A badminton racket shaft structure according to claim 5, characterized in that, The outer reinforcing layer is a high-modulus carbon fiber layup, with adjacent layups arranged alternately at an angle of 0° to ±15°, and the thickness of the outer reinforcing layer is 0.4 mm to 0.8 mm.

10. A badminton racket shaft structure according to claim 5, characterized in that, The reinforcing skeleton layer has an integrally formed handle connecting section at the proximal end and an integrally formed frame connecting section at the distal end. The outer walls of both the handle connecting section and the frame connecting section are provided with annular anti-detachment grooves, which are integrally formed with the reinforcing skeleton layer.

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