An embedded spline carbon fiber composite drive shaft, and a preparation method and application thereof

Abstract

The application discloses a kind of embedded spline carbon fiber composite material transmission shaft and preparation method and application, belong to aerospace technical field, the spline is provided by the present application, spline outer wall is equipped with annular locking groove, and inside and outside wall bonding area is equipped with thread;After inside embedding layer winding is carried out on mold core, spline is assembled, then transition layer winding and outside embedding layer winding are sequentially carried out, the winding length of each layer fiber gradually decreases and is close to spline end when transition layer winding, outside embedding layer adopts annular winding and spiral winding alternately, so that the diameter of spline embedding place is greater than the diameter of intermediate carbon fiber pipe, forming two-end thick, middle thin structure, embedded spline carbon fiber composite material transmission shaft is prepared by curing demolding.Effective stress concentration and interlaminar debonding are avoided, the thickening of spline embedding place ensures structural strength, the diameter reduction of middle section fully plays the lightweight advantage of carbon fiber, compared with the same performance aluminum alloy transmission shaft, weight reduction is more than 40%, and the torsion angle performance is better than that of aluminum transmission shaft.

Description

Technical Field

[0001] This invention belongs to the field of aerospace technology, specifically relating to an embedded spline carbon fiber composite drive shaft, its preparation method, and its application. Background Technology

[0002] Lightweighting is key to the development of materials and equipment in the aerospace field. Compared to traditional metal materials, carbon fiber composites can achieve a structural weight reduction of 30% to 60%, while maintaining mechanical properties and service stability. They are a crucial supporting material for energy conservation, emission reduction, and performance upgrades in high-end equipment. Carbon fiber reinforced polymer (CFRP) composites, with their excellent properties such as lightweight, high strength, high modulus, fatigue resistance, and corrosion resistance, have become a core material for lightweight upgrades in aerospace, new energy vehicles, high-end equipment, and drones. The transmission shaft system is one of the heaviest and most critical components in mechanical equipment; its load-bearing capacity and dynamic mechanical properties directly affect the safety and stability of the entire machine. Spline connections, as the core structure for shaft transmission and power coupling, primarily undertake the core functions of torque transmission, precise positioning, and load distribution. In traditional metal structure systems, the spline teeth and matrix are made of the same metal material, resulting in high bonding strength, good wear resistance, and stable positioning accuracy, meeting the transmission requirements of medium- and low-speed, conventional loads. With the iteration of lightweighting technology, the industry is attempting to directly replicate traditional spline structures in carbon fiber composite components, preparing integrated composite splines through composite machining and molding. However, carbon fiber composites are anisotropic layered structures with low interlayer shear strength and weak impact resistance. Traditional spline tooth groove structures exhibit significant stress concentration, making them prone to failure problems such as tooth root cracking, interlayer delamination, and fiber breakage. Furthermore, the surface of the composite has poor wear resistance, and its wear failure rate under long-term alternating loads is much higher than that of metal splines, which seriously restricts the industrial application of carbon fiber composite transmission components.

[0003] To address the mechanical defects and service limitations of traditional composite splines and meet the high-torque, high-speed, long-life, and lightweight requirements of high-end equipment, the embedded spline composite connection structure has emerged. This structure abandons the traditional approach of "directly forming spline teeth from composite materials," adopting a design concept of integrated composite curing of a carbon fiber composite matrix and a metal spline insert. A high-precision metal spline sleeve / spindle is embedded in the end of the carbon fiber composite component, achieving a reliable bond between dissimilar materials through processes such as bonding, extrusion locking, and fiber coating curing. The embedded spline precisely avoids the shortcomings of carbon fiber composites, such as easy fiber damage during machining and insufficient interlayer strength, while retaining the advantages of high precision, high wear resistance, and high load-bearing capacity of metal splines. It is perfectly suited for lightweight transmission scenarios using carbon fiber composites and has broad application prospects in high-end components such as aerospace drive shafts, new energy vehicle half-shafts, and UAV power shafts. Chinese invention patent application CN111043115B discloses a carbon fiber composite load-bearing rod and its manufacturing method. The carbon fiber composite load-bearing rod includes a base shaft and two pre-embedded pipe joints. The outer wall of the base shaft is provided with a first fiber bundle winding layer. The base shaft includes a middle section and connecting sections at both ends. The pre-embedded pipe joints are sleeved on the outside of the first fiber bundle winding layer corresponding to the connecting sections. A second fiber bundle winding layer is also provided outside the first fiber bundle winding layer corresponding to the middle section. The outer surface of the second fiber bundle winding layer and the outer surface of the pre-embedded pipe joints are jointly covered with a third fiber bundle winding layer. This carbon fiber composite load-bearing rod, by setting the fiber winding layer and pre-embedded pipe joints, effectively converts in-plane failure stress into normal compressive failure stress, greatly improving the load-bearing strength of the load-bearing rod and exhibiting excellent tensile, compressive, torsional, fatigue, and impact resistance properties. In this invention, the second fiber bundle winding layer is entirely circumferentially wound to fill all the spline wall thickness positions. For torsional transmission devices, excessive circumferential fiber winding results in poor torsional performance. Chinese invention patent application CN117722428A discloses a carbon fiber shaft drive shaft assembly and its preparation method. The traditional spline structure is directly replicated onto a carbon fiber composite component, and an integral composite spline is prepared by composite machining or molding. However, carbon fiber composite is an anisotropic layered structure with low interlayer shear strength and weak impact resistance. The traditional spline tooth groove structure has significant stress concentration, which easily leads to failure problems such as tooth root cracking, interlayer delamination, and fiber breakage. Chinese invention patent application CN121536007A discloses a carbon fiber composite drive shaft, its preparation method, and its application. It adopts a combination of adhesive bonding or riveting of carbon fiber tube body and metal shaft end / spline sleeve to connect metal splines to the end of carbon fiber tube. Although this solution avoids the defects of directly forming spline teeth from composite material, the spline and composite material are only bonded or riveted at the end, and the connection interface is still a weak link. The load transmission path is single, and there is a risk of debonding and loosening under long-term alternating load. In addition, the spline connection lacks an effective fiber reinforcement structure, which makes it difficult to meet the demanding working conditions of high torque, high speed, and long service life.In addition, most existing carbon fiber drive shafts are designed with a constant diameter tube body, and have not been optimized for local structural reinforcement and lightweighting in the spline connection area.

[0004] Therefore, there is an urgent need to find an embedded spline carbon fiber composite drive shaft, its preparation method, and its application. High-precision metal splines are embedded and installed at the end of the carbon fiber drive shaft. Through the fiber binding of the circumferential locking groove on the outer wall of the spline, the adhesive anchoring of the inner and outer wall threads, and the multiple synergies of the three-layer graded winding structure, reliable bonding of heterogeneous materials and uniform load transmission are achieved, while taking into account both high load-bearing capacity and lightweight advantages. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide an embedded spline carbon fiber composite material drive shaft, its preparation method and application, so as to solve the technical problems of stress concentration, interlayer delamination and insufficient torsional resistance caused by insufficient interlayer strength and weak connection interface of existing carbon fiber composite material drive shafts.

[0006] To achieve the above objectives, the present invention employs the following technical solution: This invention discloses an embedded spline carbon fiber composite material drive shaft, comprising: a carbon fiber composite material as a matrix and splines as inserts, wherein the splines are embedded at both ends of the carbon fiber composite material; The outer wall of the spline is provided with an circumferential locking groove, and both the inner wall bonding area and the outer wall bonding area of ​​the spline are provided with threads; The carbon fiber composite material consists of an inner embedded layer, a transition layer, and an outer embedded layer from the inside out. The diameter of the spline embedding area is larger than the diameter of the carbon fiber tube formed after the intermediate carbon fiber composite material is cured at high temperature.

[0007] This invention also discloses a method for preparing the above-mentioned embedded spline carbon fiber composite drive shaft, comprising: 1) Wrap the fiber prepreg around the pretreated mold core surface at a set winding angle to perform inner embedding layer winding; 2) Provide a spline, roughen the bonding areas of the inner and outer walls of the spline, apply adhesive to the bonding area of ​​the inner wall of the spline, assemble it to both ends of the inner embedded layer and lock it in place. 3) Perform transition layer winding. Start from the non-tooth end root position of the spline and perform circumferential winding of the fiber prepreg. Then, axially wind towards the middle position of the drive shaft and then circumferentially wind to the spline tooth root position. The winding length of each layer of fiber prepreg gradually decreases and moves closer to the spline end until the transition layer is flush with the outer wall of the spline. 4) Perform outer embedding layer winding. Apply adhesive to the bonding area of ​​the spline outer wall and start winding from the circumferential locking groove of the spline outer wall. Alternate between circumferential winding and spiral winding until the set size is reached, so that the diameter of the spline embedding part of the drive shaft is larger than the diameter of the middle carbon fiber tube. 5) After high-temperature curing and demolding, an embedded spline carbon fiber composite material drive shaft is obtained.

[0008] Preferably, in step 1), the winding angle of the fiber prepreg is adjusted within the range of 0-90°; the winding angle of the inner embedding layer is mainly ±45°, supplemented by circumferential winding; The fiber prepreg is T700, T800, T1000, T1100, M40, M55 or M65.

[0009] Preferably, in step 1), the pretreatment of the mold core includes: preheating the mold core at 120-150℃ for 0.5-2 hours and then applying a release agent; the mold core is an aluminum rod, a stainless steel rod, or a fiberglass rod; the release agent is a Dehui water-based solvent-based release agent.

[0010] Preferably, in step 2), the roughening treatment is sandblasting, shot blasting, sandpaper polishing, or thread machining; the outer wall of the spline is provided with a circumferential locking groove, and both the inner wall bonding area and the outer wall bonding area of ​​the spline are provided with threads; the adhesive is epoxy resin structural adhesive.

[0011] Preferably, in step 3), during the circumferential winding of the transition layer fiber prepreg, the overlap of adjacent wound fiber prepregs is 0%-50%.

[0012] Preferably, in step 4), the spiral winding angle of the outer embedding layer is ±45°, and the circumferential winding angle is 0°.

[0013] Preferably, in step 5), before high-temperature curing, the process further includes: completely wrapping the surface of the drive shaft with a polypropylene film in a circumferential winding, wherein the overlap of the polypropylene film winding is 10%-50%; The high-temperature curing temperature is 120-180℃, and the curing time is 1-3 hours.

[0014] Preferably, after demolding, the process further includes: grinding and polishing the surface of the carbon fiber drive shaft, spraying a surface varnish onto the carbon fiber surface, and curing it to obtain an embedded spline carbon fiber composite material drive shaft.

[0015] This invention also discloses the application of the above-mentioned embedded spline carbon fiber composite material drive shaft in aerospace vehicle transmission systems, aircraft high-lift system transmission devices, helicopter tail fin transmission systems, UAV power transmission systems, new energy vehicle drive shafts, or high-end equipment power transmission devices.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses an embedded spline carbon fiber composite drive shaft, using carbon fiber composite material as the matrix and splines as inserts. The splines are embedded at both ends of the carbon fiber composite material. The outer wall of the splines has circumferential locking grooves, and the bonding areas of the inner and outer walls have threads. The carbon fiber composite material includes an inner embedded layer, a transition layer, and an outer embedded layer from the inside out, and the diameter of the spline embedding area is larger than the diameter of the middle carbon fiber tube. The composite structure formed by the integrated curing of the carbon fiber composite matrix and the metal spline insert allows the high precision, high wear resistance, and high load-bearing capacity of the metal splines to synergistically combine with the lightweight, high strength, and fatigue resistance of the carbon fiber composite. The spline teeth are responsible for precise torque transmission and wear resistance, while the composite matrix is ​​responsible for lightweighting and load bearing. The two complement each other's functions through the embedded structure rather than simply superimposing them. The fit between the circumferential locking grooves on the outer wall of the splines and the outer embedded layer ensures the effective transmission of the circumferential tension force of the fibers, and the fit between the inner and outer wall threads and the adhesive ensures the reliability of the adhesive anchoring. The three-layer embedded structure constructs a complete stress transmission gradient at the material level. The structure, characterized by a spline embedding diameter larger than that of the intermediate carbon fiber tube and a wall thickness in the embedding region greater than that in the middle section, directly enhances the torsional section modulus and structural stiffness of the connection area. Conversely, the thinning of the middle section wall fully leverages the lightweight advantages of carbon fiber composites. The smooth transition layer prevents stress concentration at the interface, achieving synergistic optimization of high-load-bearing connection and lightweight tube body. This invention uses carbon fiber composite material as the matrix and metal splines as inserts. Through integrated curing, the splines are completely embedded within the composite end, forming a seamless bonded structure of heterogeneous materials. This fundamentally avoids the failure modes of traditional directly molded composite splines, such as root cracking, interlaminar delamination, and fiber breakage due to low interlaminar shear strength. It also overcomes the weaknesses of weak connection interfaces and single load transfer paths in composite tube and metal part end bonding / riveting. The circumferential locking groove on the outer wall of the spline, in conjunction with the threads on the inner and outer walls, forms a multi-layered mechanical locking system at the structural level. This system combines circumferential fiber binding within the groove with threaded adhesive anchoring, creating a composite connection system that ensures the spline insert and composite matrix maintain reliable connection under long-term alternating loads. The three-layer embedded structure allows the drive shaft to receive torque from the metal spline teeth, which is then evenly distributed to the carbon fiber composite matrix via the insert and composite coating layer. This avoids load concentration in weak areas of the composite, fully leveraging the lightweight and high-strength advantages of carbon fiber composites. The thickened embedded end design ensures the structural integrity of the connection area, while the reduced diameter design in the middle section maximizes weight reduction. The overall performance meets the stringent requirements of high stiffness, torsional resistance, and lightweight in the aerospace field.

[0017] This invention discloses a method for preparing an embedded spline carbon fiber composite drive shaft. Through a complete process flow including inner embedding layer winding, spline assembly, transition layer progressive winding, alternating outer embedding layer winding, and curing and demolding, it achieves integrated embedding of metal splines and carbon fiber composites. The circumferential locking groove on the outer wall of the spline, combined with the circumferential winding of the outer embedding layer starting from the groove, creates a binding effect on the spline after curing, firmly encasing the spline within the composite material and effectively preventing delamination and detachment. The threaded structure of the bonding area between the inner and outer walls of the spline, combined with roughening treatment, significantly increases the adhesive contact area and forms a mechanical interlock. Combined with the chemical bonding of the adhesive, this forms a dual connection mechanism of fiber binding and adhesive anchoring, significantly improving torsional and axial pull-out resistance. The progressive design of each layer of the transition layer, with its gradually decreasing winding length and approaching the spline end, achieves a smooth transition in wall thickness between the inner and outer embedding layers, avoiding stress concentration caused by abrupt changes in wall thickness. The outer embedding layer alternates between circumferential and helical windings, diversifying fiber orientation. The 0° circumferential winding provides tension, while the ±45° helical winding provides shear strength, fully leveraging the anisotropic advantages of carbon fiber. This ultimately results in an overall configuration that is thicker at both ends and thinner in the middle, ensuring structural strength at the spline embedding point while maximizing the lightweight advantage of carbon fiber by reducing the diameter of the middle section. Experimental results show that a 1340mm long, 42mm outer diameter carbon fiber drive shaft prepared using this method has a torsion angle of 8.0°, superior to the 9.0° of an aluminum alloy drive shaft of the same specifications. Simultaneously, its weight is only 1.20kg, a reduction of over 40% compared to the 2.01kg of an aluminum alloy drive shaft, achieving a synergistic improvement in both high strength and lightweight design.

[0018] This invention discloses an embedded spline carbon fiber composite driveshaft for applications in aerospace vehicle transmission systems, high-lift aircraft transmission systems, helicopter tail drive systems, UAV power transmission systems, new energy vehicle driveshafts, and high-end equipment power transmission devices. The driveshaft of this invention, through its embedded spline structure achieving reliable bonding of heterogeneous materials, can stably transmit power under harsh conditions of high speed, high torque, and alternating loads, avoiding system failures due to connection failures. Simultaneously, compared to aluminum alloy driveshafts, it achieves a weight reduction of over 40%, directly reducing system rotational inertia, improving transmission efficiency and response speed, and thus bringing overall benefits in fuel economy, range, payload, and handling performance. This driveshaft is particularly suitable for high-lift aircraft transmission systems, which have extremely high requirements for the deformation, transmission accuracy, and connection reliability of transmission components under changes in flight attitude and complex and varied aerodynamic loads. The driveshaft of this invention, with its high torsional stiffness and the anti-delamination and anti-detachment characteristics of the embedded connection, can ensure the precision and safety of high-lift system operation, effectively solving the technical bottleneck of existing carbon fiber driveshafts being unable to enter this core application area due to insufficient performance. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the embedded spline carbon fiber composite material drive shaft disclosed in this invention; Figure 2 This is a cross-sectional view of the embedded spline carbon fiber composite material drive shaft disclosed in this invention; Figure 3 This is an enlarged detail view of the cross-sectional view of the embedded spline carbon fiber composite material drive shaft disclosed in this invention; Figure 4 This is a schematic diagram of the spline disclosed in this invention; wherein, (a) is a cross-sectional view of the spline; (b) is a front view of the spline; and (c) is a left view of the spline.

[0020] Among them, 1. outer embedding layer; 2. transition layer; 3. inner embedding layer; 4. embedding groove; 5. spline; 6. external thread; 7. internal thread. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0023] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0024] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0025] Unless otherwise specified, the components or preferred components involved in this invention can be combined with each other to form new technical solutions.

[0026] In this invention, unless otherwise specified, the numerical range "a~b" is an abbreviation for any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "6~22" indicates that all real numbers between "6~22" have been listed in this document, and "6~22" is simply an abbreviation for these numerical combinations.

[0027] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.

[0028] The term “and / or” as used in this invention refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0029] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0030] Embedded splines, as a novel connection structure adapted to the characteristics of composite materials, break through the technical bottleneck of traditional spline-combination technology, solving the problems of easy delamination between carbon fiber composite layers, easy wear of tooth surfaces, and uneven load distribution. This invention, through innovative design of a novel embedded spline and carbon fiber composite layup structure, provides an embedded spline carbon fiber composite drive shaft, its preparation method, and its application, meeting the application requirements of high-rigidity, lightweight, and torsional-resistant drive shafts. To further optimize the mechanical properties of the carbon fiber drive shaft, the spline 5 provided in this invention uses an added circumferential locking groove on the outer wall of the embedded layer and threads on both the inner and outer walls. During the fiber layup winding process, a dual connection method of fiber locking and adhesive curing is used to combine the spline 5 and the carbon fiber composite material, achieving a reliable connection between the carbon fiber composite and the splines 5 at both ends. Furthermore, through the winding layer design, a mixed layup design with 0° and 0-90° circumferential fiber orientations significantly improves the interlayer tension and torsional resistance, meeting the requirements of transmission devices in high-torsion and high-load systems.

[0031] The method for preparing an embedded spline carbon fiber composite drive shaft disclosed in this invention includes the following steps: Step 1: Apply release agent to the mold core. First, place the mold core in an oven and preheat it at 120-150℃ for 0.5-2 hours. After taking it out, immediately apply the release agent and let it air dry naturally for later use.

[0032] The mold core is generally a cylindrical rod, including but not limited to aluminum rods, stainless steel rods, fiberglass rods, etc. The preheating conditions for the mold core are a temperature of 120-150 ℃ and a preheating time of 0.5-2 hours; The release agent is a resin product - a solvent-based release agent, manufactured by Qingdao Dehui Fine Chemical Co., Ltd.

[0033] Step 2: Inner Embedding Layer 3 Winding. The mold core coated with release agent is clamped onto the fiber winding machine. The winding program is set, and the fiber prepreg is wound at the set winding angle.

[0034] Among them, fiber prepregs include, but are not limited to, carbon fiber prepregs such as T700, T800, T1000, T1100, M40, M55, and M65, and aramid, quartz, glass and other fiber prepregs can also be used.

[0035] The winding angle should be mainly ±45°, with a small amount of circumferential winding as a supplement.

[0036] Step 3: Spline 5 assembly. Roughen the bonding areas of the inner and outer walls of spline 5. Apply epoxy resin adhesive evenly to the bonding area of ​​the inner wall of spline 5 and assemble it to both ends of the inner embedded layer 3. Lock and position spline 5 using positioning fixtures.

[0037] The spline 5 has threads designed for the bonding area between its inner and outer walls. The threads are then roughened, including but not limited to sandblasting, shot blasting, and sandpaper polishing.

[0038] The adhesive is a high-strength epoxy resin structural adhesive (Loctite E-60HP epoxy adhesive).

[0039] Step 4: Winding the transition layer 2. Begin circumferential winding of the fiber from the root of the non-tooth end of one spline 5, winding axially for 50-100mm towards the center of the drive shaft. Continue circumferential winding until the root of the non-tooth end of the spline 5 is reached, forming one layer. The length of each layer gradually decreases and moves closer to the spline 5 end. Each layer is 5-10mm shorter than the previous layer, until the transition layer 2 is flush with the outer wall of the spline 5, forming the transition layer 2 between the outer embedded layer 1 and the inner embedded layer 3. Repeat the operation to wind the other end.

[0040] Among them, fiber prepregs include, but are not limited to, carbon fiber prepregs such as T700, T800, T1000, T1100, M40, M55, and M65, and aramid, quartz, glass and other fiber prepregs can also be used.

[0041] Circular winding typically involves an overlap of 0%-50% between adjacent wound prepregs.

[0042] Step 5: Winding of the outer embedding layer 1. Apply adhesive evenly to the bonding area on the outer wall of spline 5. Start winding from the embedding groove 4 on the outer wall of spline 5 at one end. Alternate between circumferential and spiral winding. The winding method between the layers of the outer embedding layer 1 can be arbitrarily combined until the set size is reached. The winding of the carbon fiber drive shaft is completed. The diameter of the spline 5 embedding part of the drive shaft is larger, and the diameter of the carbon fiber tube in the middle is smaller, presenting an overall structure of "thick at both ends and thin in the middle". The diameter of the spline 5 embedding part is generally 1.5-3 times the diameter of the carbon fiber tube.

[0043] The transition layer 2 is completed in step 4, and the overall shape is cylindrical and conical, starting from the toothless end face of spline 5. The outer embedding layer 1 consists of multiple layers of fiber winding, each of which can be individually wound circumferentially and helically. The fiber winding structure of the transition layer 2 is only a conical circumferential winding on the end face of spline 5, which can reduce the proportion of circumferential winding fiber layers and greatly improve the torsional performance of the drive shaft. For the spline 5 embedding area, the spline 5 can be individually wound circumferentially to lock the spline 5, and then the entire drive shaft is helically wound. The carbon fiber tube is first formed by fiber winding, then shaped by film winding, and then cured at high temperature to form a carbon fiber composite material product.

[0044] Table 1. Types and number of outer embedding layers

[0045] The fiber prepreg winding angle can be adjusted in the range of 0-90°, and ±45° is more suitable for improving the torsional performance of the drive shaft.

[0046] Step 6: Polypropylene film winding and shaping. Use polypropylene film to completely wrap the surface of the drive shaft that has been wound in a circumferential manner.

[0047] The overlap of polypropylene film wrapping is generally in the range of 10%-50%, and can be adjusted appropriately.

[0048] Step 7: High-temperature curing. The drive shaft wrapped with polypropylene film is placed vertically in an oven for high-temperature curing. After natural cooling, it is demolded using a demolding machine to obtain a carbon fiber drive shaft.

[0049] The curing temperature is generally 120-180 ℃, and the curing time is 1-3 h.

[0050] Step 8: Post-processing. The surface of the carbon fiber drive shaft is ground and polished. A surface varnish can be sprayed onto the carbon fiber surface for surface protection and aesthetic treatment. After curing, a drive shaft with carbon fiber embedded splines for connection is obtained.

[0051] This invention provides a method for preparing an embedded spline carbon fiber composite drive shaft. The structure of this embedded spline carbon fiber composite drive shaft abandons the traditional approach of "directly forming spline teeth from composite material and separately bonding and riveting the inner and outer walls of spline 5". Instead, it adopts an integrated composite curing design concept of carbon fiber composite matrix and metal spline insert. A high-precision metal spline sleeve / spline shaft is embedded and installed at the end of the carbon fiber drive shaft. Reliable bonding of heterogeneous materials is achieved through processes such as bonding, extrusion locking, and fiber coating curing.

[0052] The embedded spline of this invention has an embedding groove 4 on its outer wall, which can increase the circumferential tight winding of the spline 5. The circumferential winding of the fiber in the embedding groove 4 can bind the spline 5 in the carbon fiber prepreg tape. After curing, the spline 5 can be firmly wrapped in the carbon fiber composite material, ensuring that the spline 5 and the carbon fiber composite material are subjected to uniform stress at the connection, and reducing the risk of delamination and detachment.

[0053] The bonding areas on the inner and outer walls of spline 5 are threaded and roughened before bonding to increase the adhesive contact area, improve the torsional and axial pull-out resistance of the spline 5 connection, and ensure connection reliability. The thickness of the winding layer at the spline 5 embedding area is increased, using ±45° winding as the main method, supplemented by 0° circumferential winding, to ensure the structural strength of the carbon fiber composite material at the spline 5 connection.

[0054] The drive shaft is designed with a structure that is "thick at both ends and thin in the middle". The diameter of the spline 5 embedded part of the drive shaft is larger, while the diameter of the middle carbon fiber tube is smaller. On the one hand, the thickness of the embedded layer is increased to ensure structural strength, and on the other hand, the diameter of the middle carbon fiber tube is reduced to give full play to the lightweight advantages of carbon fiber composites, achieving the dual advantages of high strength and lightweight.

[0055] This invention relates to an embedded spline, a heterogeneous composite structure, whose core consists of a carbon fiber composite matrix, a metal spline insert, and a composite connecting layer. During fabrication, precision-machined alloy steel and aluminum alloy spline inserts are positioned and fixed. Through carbon fiber layup, winding, and molding curing, the composite completely encapsulates the spline insert matrix, exposing only the mating tooth surfaces, achieving a seamless bond between the metal insert and the composite matrix. Torque is received and transmitted through the five tooth surfaces of the metal spline, and then evenly distributed to the carbon fiber composite matrix via the encapsulation layer between the insert and the composite, preventing load concentration in weak areas of the composite. Simultaneously, the high precision of the metal insert ensures mating accuracy, while the carbon fiber composite achieves overall lightweighting, balancing load-bearing capacity and lightweight advantages. A binding and fastening + adhesive bonding composite process further enhances the bonding strength of the heterogeneous materials, eliminating delamination and debonding problems. This device is suitable for transmission systems in the aerospace field and has broad application prospects and practical value.

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0057] Example 1 This invention provides a method for preparing an embedded spline carbon fiber composite drive shaft. The spline 5 is constructed by adding a circumferential locking groove to its outer wall and threads to both its inner and outer walls. During the fiber layup and winding process, a dual connection method of fiber locking and adhesive curing is used to bond the spline 5 and the carbon fiber composite material, achieving a reliable connection between the carbon fiber composite material and the splines 5 at both ends, ultimately resulting in an embedded spline carbon fiber composite drive shaft. The specific steps are as follows: Step 1: Apply release agent to the mold core. First, place the mold core in an oven and preheat it to 150 ℃ for 30 minutes. After taking it out, immediately apply the release agent and let it air dry naturally for later use.

[0058] Step 2: Inner Embedding Layer 3 Winding. The mold core coated with release agent is clamped onto the fiber winding machine. The winding program is set, and the fiber prepreg is wound at the set winding angle.

[0059] The fiber prepreg uses T700 carbon fiber prepreg.

[0060] The winding angle is ±45°.

[0061] Step 3: Spline 5 assembly. Roughen the bonding areas of the inner and outer walls of spline 5. Apply epoxy resin adhesive evenly to the bonding area of ​​the inner wall of spline 5 and assemble it to both ends of the inner embedded layer 3. Lock and position spline 5 using positioning fixtures.

[0062] Roughening processes include, but are not limited to, sandblasting, shot peening, and grinding.

[0063] The adhesive is a high-strength epoxy resin structural adhesive (Loctite E-60HP epoxy adhesive).

[0064] Step 4: Winding the transition layer 2. Begin circumferential winding of the fiber from the non-tooth root of one end of spline 5, winding axially towards the middle of the drive shaft, and then circumferentially winding to the tooth root of spline 5. The winding length of each layer gradually decreases and moves closer to the end of spline 5, until the transition layer 2 is flush with the outer wall of spline 5, forming the transition layer 2 between the outer embedded layer 1 and the inner embedded layer 3. Repeat the operation to wind the other end.

[0065] The fiber prepreg uses T700 carbon fiber prepreg.

[0066] The circumferential winding has an overlap of 5% between adjacent winding prepregs.

[0067] The winding angle is determined by winding in a circumferential direction.

[0068] Step 5: Winding of the outer embedding layer 1. Apply adhesive evenly to the bonding area of ​​the outer wall of spline 5. Start winding from the embedding groove 4 on the outer wall of one end of spline 5. First, perform one layer of circumferential winding, and then wind another layer of fiber prepreg at a winding angle of ±45°. Alternate between circumferential winding and ±45° winding until the set size is reached. The winding of the carbon fiber drive shaft is completed. The diameter of the spline 5 embedding part of the drive shaft is larger, and the diameter of the carbon fiber tube in the middle is smaller, presenting an overall structure of "thick at both ends and thin in the middle".

[0069] The fiber prepreg uses T700 carbon fiber prepreg.

[0070] The winding angle is ±45° and the winding is performed in a circumferential direction.

[0071] Step 6: Polypropylene film winding and shaping. Use polypropylene film to completely wrap the surface of the drive shaft that has been wound in a circumferential manner.

[0072] The polypropylene film is circumferentially wound and overlapped by 30%.

[0073] Step 7: High-temperature curing. The drive shaft wrapped with polypropylene film is placed vertically in an oven for high-temperature curing. After natural cooling, it is demolded using a demolding machine to obtain a carbon fiber drive shaft.

[0074] The curing temperature is 150 ℃ and the curing time is 2 h.

[0075] Step 8: Post-processing. The surface of the carbon fiber drive shaft is ground and polished. A surface varnish can be sprayed onto the carbon fiber surface for surface protection and aesthetic treatment. After curing, a drive shaft with carbon fiber embedded splines for connection is obtained.

[0076] Figure 1This is a schematic diagram of the embedded spline carbon fiber composite material drive shaft disclosed in this invention. As can be seen from the figure, the embedded spline drive shaft is composed of two splines 5 and carbon fiber composite material. The splines 5 are connected to the transmission device and play the role of transmitting torque.

[0077] Figure 2 This is a cross-sectional view of the embedded spline carbon fiber composite material drive shaft disclosed in this invention; Figure 3 This is an enlarged sectional view of the embedded spline carbon fiber composite drive shaft disclosed in this invention. As can be seen from the figure, the inner embedded layer 3 is located inside the spline 5. Adhesive is applied to the internal thread 7 of the spline 5, connecting the inner embedded layer 3 and the spline 5. The transition layer 2 consists of fiber prepreg wound circumferentially around the inner embedded layer 3, forming a smooth transition between the outer embedded layer 1 and the inner embedded layer 3, tightly connecting them and preventing defects caused by the wall thickness step at the spline 5 bonding location during the integral molding process of the embedded spline drive shaft. Adhesive is applied to the external thread 6 of the spline 5, and the embedding groove 4 can lock and embed the fibers. The outer embedded layer 1 and the spline 5 are connected through adhesive, extrusion locking, and fiber coating curing.

[0078] Figure 3 This is a schematic diagram of the spline disclosed in this invention. As can be seen from the figure, the internal thread 7 and the external thread 6 can increase the adhesive contact area, increase the force between the fiber prepreg and the spline 5, and prevent slippage during fiber winding. Fiber winding in the embedding groove 4 can embed and lock the spline 5 in the carbon fiber composite material. Through adhesive bonding, compression locking, and fiber coating curing, the spline 5 connection is ensured to be firm.

[0079] The torsion angle and mass of the carbon fiber drive shaft prepared using this invention were compared with those of an aluminum alloy drive shaft that meets the same performance requirements. The results are shown in Table 1. The carbon fiber drive shaft has a length of 1340 mm, an outer diameter of 42 mm, and an inner diameter of 35 mm. The corresponding aluminum alloy drive shaft that meets the performance requirements has an outer diameter of 42 mm, an inner diameter of 38 mm, and a length of 1340 mm.

[0080] Table 2. Performance Comparison of Embedded Spline Carbon Fiber Composite Material Driveshaft and Aluminum Driveshaft

[0081] Table 2 compares the performance of embedded spline carbon fiber composite drive shafts with aluminum drive shafts. As can be seen from the table, the carbon fiber drive shaft has significantly better torsional performance than the aluminum drive shaft when the wall thickness is smaller. The carbon fiber drive shaft is also stronger than the aluminum drive shaft and has a significant weight reduction advantage, with a weight reduction of up to 40%.

[0082] Example 2 This invention provides a method for preparing an embedded spline carbon fiber composite drive shaft. The spline 5 is constructed by adding a circumferential locking groove to its outer wall and threads to both its inner and outer walls. During the fiber layup and winding process, a dual connection method of fiber locking and adhesive curing is used to bond the spline 5 and the carbon fiber composite material, achieving a reliable connection between the carbon fiber composite material and the splines 5 at both ends, ultimately resulting in an embedded spline carbon fiber composite drive shaft. The specific steps are as follows: Step 1: Apply release agent to the mold core. First, place the stainless steel rod mold core in an oven and preheat it to 120℃ for 2 hours. After taking it out, immediately apply Dehui water-based solvent-based release agent and let it air dry naturally for later use.

[0083] Step 2: Inner Embedding Layer 3 Winding. The mold core coated with release agent is clamped onto the fiber winding machine. The winding program is set, and the fiber prepreg is wound at the set winding angle.

[0084] The fiber prepreg uses T800 carbon fiber prepreg.

[0085] The winding angle is ±45°.

[0086] Step 3: Spline 5 assembly. Roughen the bonding area of ​​the inner and outer walls of spline 5 by machining threads. Apply Loctite E-60HP epoxy structural adhesive evenly to the bonding area of ​​the inner wall of spline 5 and then assemble it to both ends of the inner embedding layer 3. Lock and position spline 5 using positioning fixtures.

[0087] Step 4: Winding the transition layer 2. Begin circumferential winding of the fiber from the non-tooth root of one end of spline 5, axially winding towards the center of the drive shaft, and then circumferentially winding to the tooth root of spline 5. The overlap of adjacent wound prepregs is 0%. The winding length of each layer gradually decreases and moves closer to the spline 5 end until the transition layer 2 is flush with the outer wall of spline 5, forming the transition layer 2 between the outer embedded layer 1 and the inner embedded layer 3. Repeat the operation to wind the other end.

[0088] The fiber prepreg uses T800 carbon fiber prepreg.

[0089] The winding angle is determined by winding in a circumferential direction.

[0090] Step 5: Winding of the outer embedding layer 1. Apply Loctite E-60HP epoxy structural adhesive evenly to the bonding area on the outer wall of spline 5. Begin winding from the embedding groove 4 on the outer wall of one end of spline 5. First, perform a circumferential wrapping layer, then wrap a layer of fiber prepreg at a winding angle of ±45°. Alternate between circumferential and ±45° winding until the set size is reached. The winding of the carbon fiber drive shaft is complete. The diameter of the spline 5 embedding area of ​​the drive shaft is larger, while the diameter of the middle carbon fiber tube is smaller, resulting in an overall structure that is "thick at both ends and thin in the middle".

[0091] The fiber prepreg uses T800 carbon fiber prepreg.

[0092] The winding angle is ±45° and the winding is performed in a circumferential direction.

[0093] Step 6: Polypropylene film winding and shaping. Use polypropylene film to completely wrap the surface of the drive shaft that has been wound in a circumferential manner.

[0094] The polypropylene film is circumferentially wound and overlapped by 10%.

[0095] Step 7: High-temperature curing. The drive shaft wrapped with polypropylene film is placed vertically in an oven and cured at 120°C for 3 hours. After natural cooling, it is demolded using a demolding machine to obtain the carbon fiber drive shaft.

[0096] Step 8: Post-processing. The surface of the carbon fiber drive shaft is ground and polished, and a surface varnish is sprayed onto the carbon fiber surface for surface protection and beautification. After curing, a drive shaft with carbon fiber embedded splines for connection is obtained.

[0097] Example 3 This invention provides a method for preparing an embedded spline carbon fiber composite drive shaft. The spline 5 is constructed by adding a circumferential locking groove to its outer wall and threads to both its inner and outer walls. During the fiber layup and winding process, a dual connection method of fiber locking and adhesive curing is used to bond the spline 5 and the carbon fiber composite material, achieving a reliable connection between the carbon fiber composite material and the splines 5 at both ends, ultimately resulting in an embedded spline carbon fiber composite drive shaft. The specific steps are as follows: Step 1: Apply release agent to the mold core. First, place the fiberglass rod mold core in an oven and preheat it at 125℃ for 1.8 hours. After taking it out, immediately apply Dehui water-based solvent-based release agent and let it air dry naturally for later use.

[0098] Step 2: Inner Embedding Layer 3 Winding. The mold core coated with release agent is clamped onto the fiber winding machine. The winding program is set, and the fiber prepreg is wound at the set winding angle.

[0099] The fiber prepreg uses T1000 carbon fiber prepreg.

[0100] The winding angle is ±45°.

[0101] Step 3: Spline 5 assembly. The bonding areas of the inner and outer walls of spline 5 are roughened by shot blasting. After evenly applying Loctite E-60HP epoxy structural adhesive to the bonding areas of the inner wall of spline 5, it is assembled to both ends of the inner embedding layer 3. The spline 5 is then locked and positioned using positioning fixtures.

[0102] Step 4: Winding the transition layer 2. Begin circumferential winding of the fiber from the non-tooth root of one end of the spline 5, winding axially towards the center of the drive shaft, and then circumferentially winding to the tooth root of the spline 5. The overlap of adjacent wound prepregs is 50%. The winding length of each layer gradually decreases and moves closer to the spline 5 end until the transition layer 2 is flush with the outer wall of the spline 5, forming the transition layer 2 between the outer embedded layer 1 and the inner embedded layer 3. Repeat the operation to wind the other end.

[0103] The fiber prepreg uses T1000 carbon fiber prepreg.

[0104] The winding angle is determined by winding in a circumferential direction.

[0105] Step 5: Winding of the outer embedding layer 1. Apply Loctite E-60HP epoxy structural adhesive evenly to the bonding area on the outer wall of spline 5. Begin winding from the embedding groove 4 on the outer wall of one end of spline 5. First, perform a circumferential wrapping layer, then wrap a layer of fiber prepreg at a winding angle of ±45°. Alternate between circumferential and ±45° winding until the set size is reached. The winding of the carbon fiber drive shaft is complete. The diameter of the spline 5 embedding area of ​​the drive shaft is larger, while the diameter of the middle carbon fiber tube is smaller, resulting in an overall structure that is "thick at both ends and thin in the middle".

[0106] The fiber prepreg uses T1000 carbon fiber prepreg.

[0107] The winding angle is ±45° and the winding is performed in a circumferential direction.

[0108] Step 6: Polypropylene film winding and shaping. Use polypropylene film to completely wrap the surface of the drive shaft that has been wound in a circumferential manner.

[0109] The polypropylene film is circumferentially wound with an overlap of 50%.

[0110] Step 7: High-temperature curing. The drive shaft wrapped with polypropylene film is placed vertically in an oven and cured at 180°C for 1 hour. After natural cooling, it is demolded using a demolding machine to obtain the carbon fiber drive shaft.

[0111] Step 8: Post-processing. The surface of the carbon fiber drive shaft is ground and polished, and a surface varnish is sprayed onto the carbon fiber surface for surface protection and beautification. After curing, a drive shaft with carbon fiber embedded splines for connection is obtained.

[0112] Example 4 This invention provides a method for preparing an embedded spline carbon fiber composite drive shaft. The spline 5 is constructed by adding a circumferential locking groove to its outer wall and threads to both its inner and outer walls. During the fiber layup and winding process, a dual connection method of fiber locking and adhesive curing is used to bond the spline 5 and the carbon fiber composite material, achieving a reliable connection between the carbon fiber composite material and the splines 5 at both ends, ultimately resulting in an embedded spline carbon fiber composite drive shaft. The specific steps are as follows: Step 1: Apply release agent to the mold core. First, place the aluminum rod mold core in an oven and preheat it to 130℃ for 1.5 hours. After taking it out, immediately apply Dehui water-based solvent-based release agent and let it air dry naturally for later use.

[0113] Step 2: Inner Embedding Layer 3 Winding. The mold core coated with release agent is clamped onto the fiber winding machine. The winding program is set, and the fiber prepreg is wound at the set winding angle.

[0114] The fiber prepreg is mainly made of M40 carbon fiber prepreg, supplemented by T1100, M55 and M65 carbon fiber prepreg as a combination of different winding layers (the inner embedding layer 3 uses M40, the transition layer 2 uses T1100, and the outer embedding layer 1 uses M55 and M65 alternately laid).

[0115] The winding angle is ±45°.

[0116] Step 3: Spline 5 assembly. Roughen the bonding areas of the inner and outer walls of spline 5 by sanding. Apply Loctite E-60HP epoxy structural adhesive evenly to the bonding area of ​​the inner wall of spline 5 and then assemble it to both ends of the inner embedding layer 3. Lock and position spline 5 using positioning fixtures.

[0117] Step 4: Winding the transition layer 2. Begin circumferential winding of the fiber from the non-tooth root of one end of spline 5, winding axially towards the center of the drive shaft, and then circumferentially winding to the tooth root of spline 5. The overlap of adjacent wound prepregs is 25%. The winding length of each layer gradually decreases and moves closer to the spline 5 end until the transition layer 2 is flush with the outer wall of spline 5, forming the transition layer 2 between the outer embedded layer 1 and the inner embedded layer 3. Repeat the operation to wind the other end.

[0118] The fiber prepreg uses T1100 carbon fiber prepreg.

[0119] The winding angle is determined by winding in a circumferential direction.

[0120] Step 5: Winding of the outer embedding layer 1. Apply Loctite E-60HP epoxy structural adhesive evenly to the bonding area on the outer wall of spline 5. Begin winding from the embedding groove 4 on the outer wall of one end of spline 5. First, perform a circumferential wrapping layer, then wrap a layer of fiber prepreg at a winding angle of ±45°. Alternate between circumferential and ±45° winding until the set size is reached. The winding of the carbon fiber drive shaft is complete. The diameter of the spline 5 embedding area of ​​the drive shaft is larger, while the diameter of the middle carbon fiber tube is smaller, resulting in an overall structure that is "thick at both ends and thin in the middle".

[0121] The fiber prepreg uses alternating layers of M55 and M65 carbon fiber prepregs.

[0122] The winding angle is ±45° and the winding is performed in a circumferential direction.

[0123] Step 6: Polypropylene film winding and shaping. Use polypropylene film to completely wrap the surface of the drive shaft that has been wound in a circumferential manner.

[0124] The polypropylene film is circumferentially wound and overlapped by 20%.

[0125] Step 7: High-temperature curing. The drive shaft wrapped with polypropylene film is placed vertically in an oven and cured at 130°C for 2.5 hours. After natural cooling, it is demolded using a demolding machine to obtain the carbon fiber drive shaft.

[0126] Step 8: Post-processing. The surface of the carbon fiber drive shaft is ground and polished, and a surface varnish is sprayed onto the carbon fiber surface for surface protection and beautification. After curing, a drive shaft with carbon fiber embedded splines for connection is obtained.

[0127] In summary, the present invention discloses an embedded spline carbon fiber composite drive shaft, its preparation method, and its application. Through an integrated process of inner embedded layer 3 winding, spline 5 assembly, transition layer 2 progressive winding, outer embedded layer 1 alternating winding, and curing and demolding, a metal spline insert with an outer wall having a circumferential locking groove and an inner and outer wall bonding area having threads is embedded in the end of the carbon fiber composite drive shaft. This forms a configuration where the diameter of the spline 5 embedded part is larger than the diameter of the middle carbon fiber tube, with thicker ends and a thinner middle. In this configuration, the winding length of each layer of the transition layer 2 gradually decreases and moves closer to the spline 5 end to achieve a smooth transition in wall thickness. The outer embedded layer 1 is wound alternately with circumferential winding and helical winding to form a multi-fiber orientation. Finally, a reliable combination of heterogeneous materials is achieved through a dual connection mechanism of fiber circumferential binding and adhesive thread anchoring. This invention effectively solves the technical problems of weak interlayer bonding, weak connection interface, easy delamination, easy debonding, and insufficient torsional resistance in the spline connection of existing carbon fiber composite drive shafts. Experiments show that the carbon fiber drive shaft with a length of 1340mm and an outer diameter of 42mm prepared by this invention has a torsion angle of 8.0°, which is better than the 9.0° of aluminum alloy drive shafts of the same specifications. The weight is only 1.20kg, which is more than 40% lighter than the 2.01kg of aluminum alloy drive shafts. It has both high load-bearing capacity and significant lightweight advantages, and can be widely used in aerospace vehicle transmission systems, high-lift aircraft transmission systems, helicopter tail drive systems, UAV power transmission systems, new energy vehicle drive shafts, and high-end equipment power transmission devices.

[0128] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An embedded spline carbon fiber composite material drive shaft, characterized in that, include: The carbon fiber composite material serves as the matrix, and the spline (5) serves as the insert, the spline (5) being embedded at both ends of the carbon fiber composite material; The outer wall of the spline (5) is provided with an circumferential locking groove, and the bonding area of ​​the inner wall of the spline (5) and the bonding area of ​​the outer wall of the spline (5) are both provided with threads; The carbon fiber composite material comprises, from the inside out, an inner embedded layer (3), a transition layer (2), and an outer embedded layer (1). The diameter of the spline (5) embedded in the spline is larger than the diameter of the carbon fiber tube formed after the intermediate carbon fiber composite material is cured at high temperature.

2. The method for preparing an embedded spline carbon fiber composite drive shaft according to claim 1, characterized in that, include: 1) Wrap the fiber prepreg around the pretreated core surface at a set winding angle to perform inner embedding layer (3) winding; 2) Provide a spline (5), roughen the bonding area of ​​the inner wall of the spline (5) and the bonding area of ​​the outer wall of the spline (5), apply adhesive to the bonding area of ​​the inner wall of the spline (5) and assemble it to both ends of the inner embedded layer (3) and lock it in place. 3) Perform transition layer (2) winding. Start from the non-tooth end root position of the spline (5) and perform circumferential winding of the fiber prepreg. Then, axially wind towards the middle position of the drive shaft and then circumferentially wind to the tooth root position of the spline (5). The winding length of each layer of fiber prepreg gradually decreases and moves closer to the spline (5) end until the transition layer (2) is flush with the outer wall of the spline (5). 4) Perform outer embedding layer (1) winding, apply adhesive to the bonding area of ​​the spline (5) outer wall, start winding from the circumferential locking groove of the spline (5) outer wall, alternate between circumferential winding and spiral winding until the set size is reached, so that the diameter of the spline (5) embedding part of the drive shaft is larger than the diameter of the middle carbon fiber tube. 5) After high-temperature curing and demolding, an embedded spline carbon fiber composite material drive shaft is obtained.

3. The method for preparing the embedded spline carbon fiber composite drive shaft according to claim 2, characterized in that, In step 1), the winding angle of the fiber prepreg is adjusted in the range of 0-90°; the winding angle of the inner embedding layer (3) is mainly ±45°, supplemented by circumferential winding; The fiber prepreg is T700, T800, T1000, T1100, M40, M55 or M65.

4. The method for preparing the embedded spline carbon fiber composite drive shaft according to claim 2, characterized in that, In step 1), the pretreatment of the mold core includes: preheating the mold core at 120-150℃ for 0.5-2 hours, and then applying a release agent; the mold core is an aluminum rod, a stainless steel rod, or a fiberglass rod; the release agent is Dehui water-based solvent-based release agent.

5. The method for preparing the embedded spline carbon fiber composite drive shaft according to claim 2, characterized in that, In step 2), the roughening treatment is sandblasting, shot blasting, sandpaper polishing or thread processing; the outer wall of the spline (5) is provided with an circumferential locking groove, and the inner wall bonding area and the outer wall bonding area of ​​the spline (5) are both provided with threads; the adhesive is epoxy resin structural adhesive.

6. The method for preparing the embedded spline carbon fiber composite drive shaft according to claim 2, characterized in that, In step 3), during the circumferential winding of the transition layer (2) fiber prepreg, the overlap of adjacent wound fiber prepregs is 0%-50%.

7. The method for preparing the embedded spline carbon fiber composite drive shaft according to claim 2, characterized in that, In step 4), the spiral winding angle of the outer embedding layer (1) is ±45° and the circumferential winding angle is 0°.

8. The method for preparing the embedded spline carbon fiber composite drive shaft according to claim 2, characterized in that, In step 5), before high-temperature curing, the following steps are included: using a polypropylene film to completely wrap the surface of the drive shaft in a circumferential winding manner, wherein the overlap of the polypropylene film winding is 10%-50%; the high-temperature curing temperature is 120-180℃, and the curing time is 1-3h.

9. The method for preparing the embedded spline carbon fiber composite drive shaft according to claim 2, characterized in that, After demolding, the process also includes grinding and polishing the surface of the carbon fiber drive shaft, spraying a clear varnish onto the carbon fiber surface, and curing it to obtain an embedded spline carbon fiber composite material drive shaft.

10. The application of the embedded spline carbon fiber composite material drive shaft as described in claim 1 in aerospace vehicle transmission systems, aircraft high-lift system transmission devices, helicopter tail fin transmission systems, UAV power transmission systems, new energy vehicle drive shafts, or high-end equipment power transmission devices.

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