A carbon fiber composite implant and method of making the same

Abstract

The application provides a carbon fiber composite implant and a preparation method thereof, and belongs to the technical field of medical devices. The carbon fiber composite implant takes a three-dimensional braided carbon fiber whole structure as a reinforcing phase and takes a heteronaphthalene diphenyl type polyarylether resin as a matrix. Carbon fibers are continuously arranged around and are not cut off on a fixing hole of the implant. First, carbon fiber tows are three-dimensionally braided to obtain a preform with a fiber volume fraction of 45% to 50%. Then, the preform is impregnated with a solution to make the resin weight content of the preform reach 35% to 40%. Forced impregnation and fiber axial orientation are realized through melt impregnation and three-zone gradient temperature control pultrusion setting. Finally, the finished product with the fixing hole is integrally molded in one step. The fiber volume fraction of the implant prepared by the application reaches 50% to 65%, the porosity is less than or equal to 1.0%, the delamination resistance is excellent, the elastic modulus is matched with human bones, the stress shielding effect can be reduced, the process is highly continuous, and the application is suitable for the large-scale preparation of various orthopedic implants such as bone plates.

Description

Technical Field

[0001] This application relates to a carbon fiber composite implant and its preparation method, belonging to the field of medical device technology. Background Technology

[0002] Internal fixation of fractures is a routine surgical procedure for treating fractures of the limbs and spine. Currently, the mainstream orthopedic implants used in clinical practice, such as bone plates and intramedullary nails, are mainly made of metal materials such as stainless steel and titanium alloys. Although they have high mechanical strength, their elastic modulus is much higher than that of human bone (the elastic modulus of cortical bone is about 10-20 GPa). This difference in modulus leads to a significant stress shielding effect: the implant bears most of the load, causing the bone at the fixation site to lack the necessary mechanical stimulation for a long time, which in turn leads to bone resorption and osteoporosis. This not only delays the fracture healing process but also makes it easier for refractures to occur after the implant is removed.

[0003] To address the stress shielding defects of metallic implants, carbon fiber reinforced resin (CFRP) composites have gradually become a research hotspot in the field of orthopedic implants. The elastic modulus of CFRP can be controlled through design to a range that matches human bone, thereby eliminating the stress shielding effect. Simultaneously, it possesses advantages such as high specific strength, good biocompatibility, and absence of magnetic resonance imaging artifacts, making it considered an important development direction for next-generation orthopedic internal fixation materials. Current CFRP implants mostly employ a lamination (2D layup) prepreg hot-pressing process, where carbon fiber prepreg is laid layer by layer at a designed angle and then hot-pressed and cured. However, this process has inherent drawbacks that are difficult to overcome: Firstly, the interlayer performance is weak: the layers are only bonded by the resin matrix, resulting in poor interlayer shear strength and impact resistance. Under cyclic loading, delamination failure is likely to occur, which limits the fatigue life of the implant.

[0004] Secondly, there is severe stress concentration around the hole: the fixation hole required for the implant needs to be prepared through subsequent mechanical processing. The drilling process will cut the continuous fiber, making the area around the hole a mechanically weak area. The stress concentration coefficient increases significantly, making it a high-risk location for fatigue fracture of the implant.

[0005] Third, poor product consistency: For implants with complex hollow or variable cross-section structures, it is difficult to precisely control the resin flow path and fiber orientation during hot pressing, which can easily lead to defects such as resin enrichment and fiber buckling, resulting in large fluctuations in the mechanical properties of products within and between batches.

[0006] The emergence of three-dimensional integral weaving technology offers a new approach to solving the aforementioned interlayer and peripore defects. The three-dimensional weaving process allows carbon fibers to interweave in multiple directions within space, forming an integrated mesh structure, fundamentally eliminating the interlayer interfaces of laminated materials and ensuring the continuity of fibers around the pores. However, the dense structure of simple three-dimensional weaving also makes it difficult for resin to achieve sufficient impregnation, limiting the mechanical properties of the final product.

[0007] Currently, there is no solution that can simultaneously take into account the overall structural advantages of three-dimensional weaving and ensure sufficient resin impregnation to achieve excellent interlayer performance and high product quality, which also restricts the clinical application and industrialization of high-performance carbon fiber composite implants. Summary of the Invention

[0008] To address the aforementioned issues, a carbon fiber composite implant and its preparation method are provided. Through a synergistic process route of three-dimensional weaving, solution impregnation, melt pultrusion, and integrated molding, the technical bottleneck of the difficulty in permeating dense woven structures with naphthalene-biphenyl-type polyarylene ether resin is overcome. This method produces orthopedic implants that possess an overall anti-delamination structure, high fiber volume fraction, low porosity, and continuous peripore fibers. The final product exhibits excellent mechanical properties and a good match between its elastic modulus and human bone structure, meeting the long-term service requirements of clinical orthopedic internal fixation.

[0009] According to one aspect of this application, a carbon fiber composite implant is provided, comprising a carbon fiber reinforcing phase and a resin matrix, wherein the carbon fiber reinforcing phase is a three-dimensional braid and the resin matrix is ​​a polyarylene ether resin of the naphthalene-biphenyl type. The carbon fiber composite implant has a fiber volume fraction of 50%-65% and an internal porosity of ≤1.0%; the carbon fiber composite implant is provided with fixing holes, and the carbon fibers are continuously arranged around the fixing holes without being cut.

[0010] The fiber volume fraction of the carbon fiber composite implant is selected from any value between 50% and 65%, for example, the following values ​​or any range formed between the two: 50.0%, 50.1%, 50.2%, 50.3%, 50.4%, 50.5%, 50.6%, 50.7%, 50.8%, 50.9%, 51.0%, 51.1%, 51.2%, 51.3%, 51.4%, 51.5%, 51.6%, 51.7%, 51.8%, 51.9%, 52.0%, 52.1%, 52.2%, 52.3%, 52.4%, 52.5%, 52.6%, 52.7%, 52.8%, 52.9%, 53.0%, 53.1%, 53.2%, 53.3%, 53%... 0.4%, 53.5%, 53.6%, 53.7%, 53.8%, 53.9%, 54.0%, 54.1%, 54.2%, 54.3%, 54.4%, 54.5%, 54.6%, 54.7%, 54.8%, 54.9%, 55.0%, 55.1%, 55.2%, 55.3%, 55.4%, 55.5%, 55.6%, 55.7%, 55.8%, 55.9%, 56.0%, 56.1%, 56.2%, 56.3%, 56.4%, 56.5%, 56.6%, 56.7%, 56.8%, 56.9%, 57.0%, 57.1%, 57.2%, 5 7.3%, 57.4%, 57.5%, 57.6%, 57.7%, 57.8%, 57.9%, 58.0%, 58.1%, 58.2%, 58.3%, 58.4%, 58.5%, 58.6%, 58.7%, 58.8%, 58.9%, 59.0%, 59.1%, 59.2%, 59.3%, 59.4%, 59.5%, 59.6%, 59.7%, 59.8%, 59.9%, 60.0%, 60.1%, 60.2%, 60.3%, 60.4%, 60.5%, 60.6%, 60.7%, 60.8%, 60.9%, 61.0%, 61.1%. 61.2%, 61.3%, 61.4%, 61.5%, 61.6%, 61.7%, 61.8%, 61.9%, 62.0%, 62.1%, 62.2%, 62.3%, 62.4%, 62.5%, 62.6%, 62.7%, 62.8%, 62.9%, 63.0%, 63.1%, 63.2%, 63.3%, 63.4%, 63.5%, 63.6%, 63.7%, 63.8%, 63.9%, 64.0%, 64.1%, 64.2%, 64.3%, 64.4%, 64.5%, 64.6%, 64.7%, 64.8%, 64.9%, 65.0%.

[0011] In one specific embodiment of the present invention, the fiber volume fraction of the carbon fiber composite implant is 52%.

[0012] In one specific embodiment of the present invention, the fiber volume fraction of the carbon fiber composite implant is 62.3%.

[0013] In one specific embodiment of the present invention, the fiber volume fraction of the carbon fiber composite implant is 63.5%.

[0014] The internal porosity of the carbon fiber composite implant is selected from any value between 0% and 1.0%, such as the following values ​​or any range formed between the two: 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%.

[0015] As a specific embodiment of the present invention, the internal porosity of the carbon fiber composite implant is 0.38%.

[0016] As a specific embodiment of the present invention, the internal porosity of the carbon fiber composite implant is 0.28%.

[0017] As a specific embodiment of the present invention, the internal porosity of the carbon fiber composite implant is 0.9%.

[0018] Optionally, the carbon fiber composite implant is a bone plate; The flexural modulus of the bone plate is 25~55GPa, which matches the elastic modulus of human cortical bone.

[0019] Specifically, the interlaminar shear strength of the bone plate is ≥65MPa, and the flexural strength is ≥750MPa.

[0020] According to another aspect of this application, a method for preparing the carbon fiber composite implant as described above is also provided, comprising the following steps: (1) Three-dimensional weaving: Carbon fiber bundles are woven into a three-dimensional weaving preform by a three-dimensional weaving process, wherein the fiber volume fraction of the three-dimensional weaving preform is 45%~50%; (2) Solution impregnation: Dissolve the naphthalene-biphenyl type polyarylene ether resin in an organic solvent to prepare an impregnation solution. Place the three-dimensional braided preform obtained in step (1) into the impregnation solution for impregnation treatment, and then dry to remove the solvent to obtain a three-dimensional braided preform with a resin weight content of 35%~40% after solution impregnation. (3) Melt impregnation and pultrusion shaping: The three-dimensional braided preform obtained in step (2) is drawn through a melt resin bath at a temperature of T1 for melt impregnation, and then passed into a pultrusion mold for shaping; The pultrusion die is divided into three zones along the traction direction: a first zone, a second zone, and a third zone. The temperature of the first zone of the pultrusion die is T2, the temperature of the second zone is T3, and the temperature of the third zone is T4. Where T1 and T2 are Tg+50℃~Tg+100℃, T3 is Tg+30℃~Tg+80℃, and T4 is Tg-100℃~Tg-50℃; and T2≥T3, T2 T3≤40℃, where Tg is the glass transition temperature of the naphthalene-biphenyl type polyarylene ether resin; (4) Integrated molding: After the pultruded profile blank is preheated to temperature T5, it is placed into the molding mold and pressed and cured at temperature T6 to produce a finished implant with fixing hole in one step. Where T5 is Tg+80℃ ~ Tg+115℃, and T6 is Tg+85℃ ~ Tg+115℃.

[0021] First, in the field of orthopedic implant molding technology, there is a certain technical bias among those skilled in the art: that is, for orthopedic implants with complex anatomical shapes (such as bone plates that conform to the curves of bones), three-dimensional woven preforms can only be finally formed by direct molding.

[0022] However, for high-performance thermoplastic resins (such as PPESK / PPENK), their extremely high melt viscosity is a fundamental obstacle to the molding process's inability to fully impregnate dense three-dimensional braids.

[0023] In this application, a three-dimensional braiding + pultrusion + molding process is employed. Pultrusion provides better compaction capability than molding, ensuring impregnation quality and extremely high fiber content, which is the basis for the better mechanical properties of the final implant. Traditional molding struggles to achieve high-pressure compaction. The dried three-dimensional braided preform and resin film or powder are placed in a mold, relying on the flow of the melted resin during molding for impregnation. For dense three-dimensional braids, the resin flow resistance is high, easily forming "dry spots." Vf is typically low (<55%), where Vf = (total fiber volume / total composite volume) × 100%. The essence of the pultrusion process in this application is high-pressure continuous compaction. The impregnated preform passes through a precision mold under traction force, experiencing extremely high radial pressure, forcing resin flow and eliminating air bubbles, achieving Vf > 60%.

[0024] In traditional 3D braiding + direct molding solutions, when the 3D braided composite material is directly molded, the resin flow path is long, making it difficult to expel trapped air and volatiles, resulting in a porosity typically >2%. The continuous high pressure and directional flow within the implant pultrusion mold of this application effectively eliminate air bubbles, allowing the porosity to be easily controlled to <1%, or even <0.5%.

[0025] Furthermore, since the implant is a beam-like structure that bears bending loads during use, the solution of this application enables the implant to have better axial stiffness / strength. During the molding process, fibers may undergo uncontrollable buckling, wrinkling, or displacement due to the viscous drag of the resin, affecting the orientation of the final mechanical properties. In the pultrusion process of the implant of this application, the fibers are continuously straightened and aligned under tension, with a highly consistent orientation, mainly arranged along the axial direction, which can maximize the axial performance of the fibers.

[0026] Therefore, the role of the "pultrusion" step in this application is not only "shaping" but also a key step in "high-pressure forced micro-impregnation", which solves the core technical problem that thermoplastic resin is difficult to impregnate three-dimensional woven bodies.

[0027] The method of this application adopts a four-in-one synergistic process of "three-dimensional weaving - solution impregnation - melt pultrusion - integrated molding", which breaks through the technical prejudice in this field that "three-dimensional woven orthopedic implants can only be directly molded".

[0028] Specifically, the three-dimensional weaving process prefabricates the overall skeleton structure, ensuring the final product's resistance to delamination. Solution impregnation allows the resin solution to penetrate the loose and porous structure of the three-dimensional weaving preform. After drying, the resin can uniformly adhere to the surface of each fiber monofilament, forming a "resin pre-distribution body." During the subsequent melt pultrusion process, this pre-distribution body fuses with the molten resin in the pultrusion tank to form a homogeneous continuous phase, achieving final densification under the high-pressure shearing action of the pultrusion die.

[0029] The melt pultrusion process achieves high-pressure forced compaction through continuous traction force and radial pressure of the die. Combined with a three-zone gradient temperature control system based on the glass transition temperature, the first zone maintains the resin in a low-viscosity flow state to achieve deep wetting and bubble removal. The second zone achieves viscosity transition and preliminary shaping to stabilize the cross-sectional dimensions. The third zone rapidly cools to complete curing and shaping, ultimately achieving a high fiber volume fraction and extremely low porosity. The subsequent integrated molding process, without destroying the already formed excellent microstructure, molds complex anatomical shapes and fixed holes with continuous fiber wrapping in one go, balancing the high efficiency of continuous production with the precise molding of complex shapes. The batch consistency of the products is higher than that of the intermittent direct molding process.

[0030] The carbon fiber bundle used in step (1) is bare carbon fiber or pretreated carbon fiber bundle. Pretreatment can be sizing, which is a common pretreatment process in the field and is not specifically limited by this invention.

[0031] Optionally, the sizing agent in step (1) is a thermoplastic polymer with a glass transition temperature of not less than 200°C and an elongation at break of not less than 10% for its homopolymer film.

[0032] The sizing agent is selected from at least one of the following: a phenylene ether sulfone containing phenylene biphenyl, a phenylene ether nitrile ketone containing phenylene biphenyl, or a fluorene-containing heterocyclic ether ketone or a phthalocyanine-terminated heterocyclic ether.

[0033] The weight ratio of the naphthalene-biphenyl type polyarylene ether resin to the organic solvent in step (2) is (30~35):(70~65). The remaining volume in step (2) consists of gaps between fibers and fiber bundles, which facilitates the full penetration and wetting of the subsequent resin solution.

[0034] Specifically, the impregnation solution with this ratio has a suitable viscosity and resin solid content, which can ensure that the resin fully wets the surface of a single carbon fiber, and will not cause the fiber bundle to be unable to penetrate due to excessive viscosity, nor will it cause insufficient resin content after drying due to excessively low solid content. This can ensure that the resin content is stable within the target range, providing a uniform raw material basis for subsequent melt impregnation.

[0035] Optionally, the organic solvent in step (2) is N-methylpyrrolidone, and the polyarylene ether resin is polyarylene ether sulfone ketone (PPESK) or polyarylene ether nitrile ketone (PPENK).

[0036] The presence of rigid diazonyl ketone and biphenyl structures in the molecular chain of polyaryl ether resins results in extremely high melt viscosity, making thermoforming difficult and a significant bottleneck restricting their widespread application. Pure PPESK, in particular, exhibits poor melt processability.

[0037] This application avoids the problem of requiring extremely high viscosity flow temperature for direct melt processing of resin by adopting a step-by-step strategy of weaving → solution impregnation → melt pultrusion high-pressure wetting → compression molding. Only part of the wetting task is completed each time, which reduces the difficulty of a single processing.

[0038] Regarding the melt impregnation temperature, T1 and T2 are uniformly set to Tg+50℃~Tg+100℃. In actual production, the Tg of PPESK can be precisely designed between 250 and 370℃ depending on the sulfone / ketone ratio; this application does not impose a specific limitation.

[0039] The temperature range used in this application is set based on the following considerations, and the parameters are explained below: Lower limits of T1 and T2: Tg +50℃ Tg+50℃ ensures that the melt is in a low-viscosity viscous flow state. Rheological studies of PPESK / PS blends show that increasing the temperature can reduce the melt viscosity. This limitation is beneficial for the resin to generate strong shear flow in the pultrusion die convergence channel, forcing it to wet the gaps inside the fiber bundle.

[0040] Lower limits of temperature T1 and T2: Tg + 100℃ Specifically, the following conditions are considered: 1. Thermal Decomposition Constraints: The 5% thermal weight loss temperature of PPESK film under nitrogen is typically above 500℃. However, PPESK has a narrow processing temperature range; excessively high temperatures can easily lead to decomposition and carbonization, resulting in defects such as internal micropores and an uneven appearance. Materials like PPENK have a 5% thermal weight loss temperature of 491–510℃, and at 800℃, the residual carbon content is 63%–65%. Temperatures exceeding this range may accelerate thermal degradation.

[0041] 2. Melt index constraint: High flowability polyethersulfone ketone resin products have a melting point of 305-340℃, and the processing and molding temperature is usually not higher than 350℃.

[0042] 3. Viscosity lower limit constraint: Too low melt viscosity will cause excessive resin loss, and during extrusion traction, it will be impossible to build up enough back pressure to complete effective compaction, which will reduce the fiber volume fraction.

[0043] 4. Equipment and cost constraints: For every 10°C increase in temperature, energy consumption and heating element losses increase significantly. Long-term operation above 400°C has a significant impact on the lifespan of mold materials (hard alloy) and heating elements.

[0044] Optionally, the three-dimensional weaving angle in step (2) is ±15°~±25°.

[0045] The three-dimensional weaving angle mentioned in step (2) is selected from any value between ±15° and ±25°, such as the following values ​​or any range formed between the two: ±15°, ±16°, ±17°, ±18°, ±19°, ±20°, ±21°, ±22°, ±23°, ±24°, ±25°.

[0046] In one specific embodiment of the present invention, the three-dimensional weaving angle is ±18°.

[0047] In one specific embodiment of the present invention, the three-dimensional weaving angle is ±20°.

[0048] Specifically, this braiding angle range can achieve a better balance between axial mechanical properties and transverse anti-delamination properties; a smaller braiding angle allows more fibers to be arranged along the axial direction, ensuring the bending strength and modulus of the implant and meeting the load-bearing requirements of orthopedic internal fixation; at the same time, it retains an appropriate amount of transverse interwoven fibers to maintain the shear resistance and anti-delamination advantages of the three-dimensional overall structure, avoiding a decrease in axial load-bearing capacity due to an excessively large braiding angle, or an insufficient interlayer performance due to an excessively small braiding angle.

[0049] Optionally, the melt impregnation in step (3) is carried out with the assistance of mechanical stirring, and the stirring speed is 100~300 rpm.

[0050] Mechanical stirring can drive the molten resin to generate directional flow and shearing action. On the one hand, it reduces the apparent viscosity of the resin, enhances its ability to penetrate into the gaps inside the three-dimensional woven preform, and improves the uniformity of wetting. On the other hand, it can wash away the surface of the preform, remove the entrained micro-bubbles, and further reduce the porosity of the final product.

[0051] Optionally, the immersion time of the three-dimensional braided preform in the molten resin bath in step (3) shall not be less than 60s.

[0052] Optionally, the third zone of the pultrusion die in step (3) is equipped with a forced cooling system, and the cooling rate of the profile is controlled at 5~10℃ / min.

[0053] The cooling rate of the profile in step (3) is selected from any value between 5 and 10℃ / min, such as the following values ​​or any range formed between the two: 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min.

[0054] In one specific embodiment of the present invention, the cooling rate of the profile is 7°C / min.

[0055] In one specific embodiment of the present invention, the cooling rate of the profile is 8°C / min.

[0056] Specifically, this cooling rate can achieve a quenching effect, freezing the polyarylether resin molecular chains before they have enough time to fully relax and arrange themselves in an orderly manner, forming a non-equilibrium glass structure. This structure not only ensures the dimensional accuracy and structural stability of the pultruded profile, but also retains excellent secondary thermoplastic reshaping capability, allowing the blank to soften and deform uniformly after heating in the subsequent molding process, filling complex anatomical cavities without damaging the fiber orientation.

[0057] Optionally, the holding pressure in step (4) is 10-15 MPa and the holding time is 40-60 min.

[0058] The beneficial effects of this application include, but are not limited to: 1. This application addresses the problem that high-viscosity naphthalene-biphenyl polyarylether resin is difficult to impregnate dense three-dimensional braided structures. It adopts a two-stage impregnation scheme of solution impregnation and melt pultrusion, combined with the high-pressure compaction effect of the pultrusion die, which significantly improves the mechanical properties and long-term reliability of the material and breaks through the performance bottleneck of special resin three-dimensional braided implants.

[0059] 2. The flexural modulus of the implant prepared in this application can be precisely controlled in the range of 25-55 GPa, matching the elastic modulus of human cortical bone, effectively eliminating the stress shielding effect commonly found in metal implants, promoting fracture healing, and reducing the risk of postoperative bone resorption and refracture; the naphthalene-biphenyl polyarylene ether resin has excellent resistance to degradation by body fluids and biocompatibility, with no risk of metal ion release and no MRI imaging artifacts, making it suitable for modern clinical diagnosis and treatment needs.

[0060] 3. In this application, the three-dimensional braided preform has fibers that naturally and continuously wrap around the hole processing area, avoiding the problem of fiber cutting of the layup material, reducing stress concentration around the hole, and improving the long-term reliability for clinical use.

[0061] 4. The proposed solution ensures stable product performance both within and between batches during standardized mass production of implants. Traditional direct molding after weaving employs intermittent production, requiring separate loading, mold closing, and mold opening cycles for each product. This process is lengthy, inefficient, and subject to fluctuations in process conditions between cycles, leading to variations in product performance. The pultrusion process used in this application is a continuous process, offering high production efficiency, flexible product lengths, and molds that guarantee a high degree of consistency in product cross-sectional dimensions and performance. Attached Figure Description

[0062] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the melt impregnation and pultrusion shaping sections in the preparation method of this application; Figure 2 This is a longitudinal sectional view of carbon fiber composite plates with different pultrusion forming methods in this application (where the left side is the cross section of a straight composite plate formed by linear pultrusion, and the right side is the cross section of an arc-shaped composite plate formed by bending pultrusion).

[0063] Explanation of symbols in the diagram: 1. Twin-screw extruder; 2. Melt dip tank; 3. First zone; 4. Second zone; 5. Third zone; 6. Pultrusion die. Detailed Implementation

[0064] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0065] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. The reagents and raw materials used in this invention are readily available through conventional means, and unless otherwise specified, they shall be used in accordance with conventional methods in the art or as per the product instructions. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described in this patent are for illustrative purposes only.

[0066] Example 1: Carbon fiber / PPESK composite flat radius and ulna bone plate (for radius and ulna fracture fixation) - standard process without pre-drilled holes S1. Carbon fiber sizing treatment Material: T700SC-12K-50C carbon fiber bundles (dry fiber bundles) from Toray Industries, Inc. of Japan.

[0067] Sizing agent selection: In this embodiment, the sizing agent is poly(phenylene ether sulfone) (PPBES), which has a glass transition temperature of about 214~223℃ and the homopolymer film has good flexibility. PPBES solution-type carbon fiber sizing agents have been reported in the literature (Pan Xiaotong et al., Engineering Plastics Application, 2023, 51(9): 1-7, 26).

[0068] PPBES resin was dissolved in a chloroform / N-methylpyrrolidone mixed solvent (volume ratio 2:8) to prepare a homogeneous solution with a mass concentration of 1.0%~1.5% as a sizing agent.

[0069] Sizing process: The carbon fiber bundle passes through the impregnation tank containing the above sizing agent at a speed of 2~5m / min. The tank is equipped with guide rollers to ensure that the fiber bundle is completely immersed, and the immersion time is not less than 30 seconds.

[0070] Drying: The sized fiber bundles are put into a hot air drying oven and dried at 200~250℃ to remove the solvent and make the sizing agent form a uniform film on the fiber surface.

[0071] Sizing Amount Control: By adjusting the sizing agent concentration and traction speed, the solid content of the sizing agent on the carbon fiber surface is controlled to be 0.8%~1.5% (relative to fiber weight). This extremely low sizing amount ensures: ① a sufficient protective layer is formed on the surface of the carbon fiber bundle, resulting in good bundle cohesion and no obvious fuzz; ② the main body of the fiber bundle is not filled with resin, and the internal monofilaments can still slide freely relative to each other, maintaining sufficient flexibility to meet the requirements of subsequent three-dimensional weaving.

[0072] The technical effects of this step: The carbon fiber bundle treated with PPBES forms an extremely thin, high-temperature resistant polymer coating on its surface. This coating binds thousands of monofilaments together, improving the fiber bundle's abrasion resistance and anti-pilling ability. Simultaneously, due to the extremely low sizing amount (<2.0%), the monofilaments within the fiber bundle are not filled with resin and can still slide freely relative to each other, maintaining the overall softness of the dry fiber bundle. This allows it to smoothly pass through the yarn guide holes and yarn tubes of the braiding machine to complete three-dimensional braiding. The selected sizing agent has a glass transition temperature much higher than room temperature, ensuring the coating remains a solid film during braiding, effectively protecting the fibers. Furthermore, its Tg is lower than the subsequent melt pultrusion temperature (approximately 360°C), allowing the sizing layer to soften and fuse with the matrix resin during high-temperature processing, forming a strong interfacial bond.

[0073] S2. Three-dimensional woven prefabricated structure: A four-way three-dimensional braiding machine is used, with the braiding angle set at ±20° (a smaller braiding angle is beneficial for providing a higher axial modulus).

[0074] Prefabricated body shape: woven into a solid strip structure with a cross-section of 12mm x 3mm.

[0075] Fiber volume fraction (preform): By controlling the tension of the carbon fiber bundles and the weaving density, the fiber volume fraction of the woven preform is controlled at 48%.

[0076] S3. Solution impregnation: Materials: The resin is PPESK resin with an intrinsic viscosity of 0.45 dL / g synthesized by the Special Engineering Plastics Research Center of Jilin University. The glass transition temperature (Tg) of the PPESK resin used is 256℃.

[0077] Impregnation solution preparation: PPESK particles and N-methylpyrrolidone (NMP) solvent are mixed at a weight ratio of 35:65 and mechanically stirred at 85°C for 6 hours until a uniform, transparent, bubble-free solution is formed.

[0078] Impregnation process: The three-dimensional braided preform obtained in S2 is completely immersed in the above impregnation solution and impregnated at 80~100°C for no less than 60 minutes (90 minutes in this embodiment). During this period, mechanical stirring or ultrasonic vibration is used to ensure that the resin solution fully penetrates into the fiber bundles and the gaps between the monofilaments inside the preform.

[0079] Drying: The impregnated 3D woven preform is immediately placed in an 8-meter-long, three-zone hot air circulating drying oven. The temperature profile is strictly set as follows: Zone 1 100℃, Zone 2 180℃, Zone 3 240℃. The total residence time of the 3D woven preform in the oven is approximately 4 minutes. This process aims to completely evaporate most of the solvent and allow the PPESK resin to partially gel.

[0080] The final impregnated three-dimensional woven preform has a resin weight content of 38±2%. This three-dimensional woven preform is dry, non-sticky, and has a certain degree of flexibility, and can be wound onto a reel and stored at room temperature for later use.

[0081] S4. Melt impregnation and pultrusion shaping refer to Figure 1 The overall process of melt impregnation and pultrusion is as follows: The twin-screw extruder 1 melts and plasticizes the naphthalene-biphenyl type polyarylene ether resin, continuously feeding it into the melt impregnation tank 2. After the preform is fully impregnated with resin in the melt impregnation tank 2, it is fed into the pultrusion die 6. The pultrusion die 6 is divided into three zones along the traction direction: zone 3, zone 4, and zone 5. The preform sequentially undergoes heating and homogenization in zone 3, compaction and debubbling in zone 4, and cooling and shaping in zone 5 before being output, resulting in carbon fiber reinforced polyarylene ether pultruded profiles with stable dimensional accuracy and low internal porosity. Specifically, this includes: (1) Molten Resin Supply Unit Core equipment: A co-rotating twin-screw extruder is preferred. It provides better mixing than a single-screw extruder, ensuring uniform preheating / initial melting of the granules.

[0082] Screw diameter: 40mm; length-to-diameter ratio (L / D): 40:1. The relatively long L / D ratio ensures that the resin has sufficient residence time and thermal history to achieve full melt plasticization.

[0083] Screw configuration: The screw is designed as a modular block, comprising a conveying section, a melting section (configured with kneading blocks to provide high shear and promote melting), a mixing section (ensuring uniform dispersion of pigments or additives, which were not added in this example), and a metering conveying section.

[0084] Temperature control system: The extruder extrusion temperature is set to 340℃, using PID intelligent control with an accuracy of ±1.0℃.

[0085] Feeding system: PPESK resin granules are continuously and precisely fed into the extruder via a loss-in-weight metering feeder. The feeding rate is set and controlled in conjunction with the linear density of the final profile and the target fiber volume fraction.

[0086] (2) Mechanically stirred melt impregnation tank 2 Structure and Heating Method: The immersion tank body is a cylindrical container made of high-temperature resistant stainless steel. Evenly distributed perforations are formed on the outer wall of the tank, through which high-power cylindrical electric heaters (heating rods) are installed.

[0087] Temperature control system: The electric heater is divided into multiple independent temperature control zones (such as upper, middle, and lower zones). Each zone is equipped with a K-type or S-type thermocouple inserted into the tank or attached to the inner wall to monitor the temperature in real time. The signal is transmitted to a multi-channel PID temperature controller, which precisely controls the on / off power of each group of heaters through solid-state relays (SSRs) to achieve highly uniform and stable temperature inside the tank, with a temperature control accuracy of ±2℃.

[0088] Thermal insulation: The tank body is wrapped with multiple layers of high-temperature ceramic fiber felt or aluminum silicate fiber board with a thickness of not less than 50mm to minimize heat loss and improve energy efficiency and temperature stability.

[0089] Mechanical stirring system: Agitator type: Inclined blade turbine agitator. This type of blade generates strong axial and radial fluid flow, combining high shear force and strong circulation capacity, transferring macroscopic flow to the area around the fiber preform to achieve dynamic impregnation.

[0090] Materials and Drive: Both the agitator shaft and blades are made of high-temperature nickel-based alloys (such as Inconel 600) to withstand long-term high-temperature operation. The agitator shaft is connected to the motor above via a magnetic coupling drive system. Magnetic coupling achieves a completely dynamic seal, thoroughly solving the leakage and wear problems that may occur at the shaft seal in high-temperature molten environments, ensuring the long-term sealing and reliability of the system.

[0091] Parameter control: The stirring motor is controlled by a frequency converter, and the speed can be precisely adjusted within the range of 50 to 300 rpm. Considering the viscosity and impregnation requirements of the PPESK melt, the optimal operating speed is set to 150 rpm. At this speed, the melt generates intense but non-turbulent vortices (avoiding excessive air entrainment), creating a comprehensive "scouring" and "kneading" effect on the passing preform.

[0092] Guide roller system: Guide rollers are installed in the trough to allow the preform to pass through the center region of the strong flow field generated by the stirring blades, ensuring that it is subjected to the most effective fluid shearing action.

[0093] (3) Melt impregnation tank 2 Structure and Materials: The impregnation tank is a sealed stainless steel container with an insulated jacket. Its volume ensures sufficient impregnation time for the preform (≥90 seconds). The interior of the tank is polished to a mirror finish (Ra<0.4μm) to reduce resin buildup. The tank lid is openable for easy cleaning and maintenance.

[0094] Temperature control: The temperature of the molten resin in the tank is precisely maintained at (360±5)℃ using a PID controller. Multiple high-precision platinum resistance temperature sensors are embedded in the inner wall of the tank to provide real-time temperature data feedback.

[0095] Guide roller system: Several high-temperature resistant, smooth-surfaced ceramic guide rollers are installed in the tank. These guide rollers guide the preform through the molten resin in an "S" shaped path, ensuring complete immersion and increasing the effective impregnation length. This reduces the apparent viscosity of the resin, enhances its flow and penetration capabilities, breaks up tiny air bubbles that may be trapped within the fiber bundles, and strengthens the resin's wetting of the fiber surface.

[0096] (4) Impregnation process The woven preform is drawn into the impregnation tank at a constant speed of 0.8 m / min. In the molten PPESK at 360°C, the original resin from the solution method in the preform rapidly softens and melts, fusing with the newly added resin in the tank to form a homogeneous continuous phase. During the impregnation period of 112.5 seconds, the low-viscosity molten resin is forcibly penetrated into every tiny gap inside the preform, achieving deep wetting between fiber bundles and even at the monofilament level within the bundle. At this point, the preform is in a state of "resin supersaturation".

[0097] After impregnation, the mold continuously enters the pultrusion mold 6, which is directly connected to the impregnation tank.

[0098] (5) Pultrusion die 6 structure Pultrusion Die 6: Employs a monolithic carbide die. The die cavity cross-section resembles a bone plate structure, divided into three functional zones from the inlet to the outlet. Its dimensions are precisely calculated and rheologically simulated. Entry region (convergence region): The cross-section gradually shrinks, applying initial compression to the material.

[0099] Intermediate zone (parallel zone): The cross-section is constant, and it is the main area for compaction and wetting.

[0100] Export area (sizing area): The final finishing area to ensure the final dimensional accuracy and surface finish of the product.

[0101] Heating and Cooling: The mold is covered by three independent heating jackets (corresponding to zones one, two, and three), using ceramic heating rods with uniform power density. Each heating jacket is equipped with an independent PID temperature controller and thermocouple, with a temperature control accuracy of ±1.5℃. Cooling channels are also drilled inside zone three of the mold, connected to a high-precision mold temperature controller for rapid and controllable cooling.

[0102] (6) Three-zone temperature setting Zone 1, Section 3 (340℃): This temperature is still much higher than the Tg of PPESK, ensuring that the resin maintains extremely low viscosity and is in the optimal viscous flow state.

[0103] Function: Under this high pressure (generated by the reaction of traction force), the low-viscosity resin generates strong shear flow within the converging channel of the mold, which can thoroughly wet the last blind area inside the fiber bundle and effectively merge and extrude microbubbles. This zone is the most critical step in achieving a porosity of less than 0.4%.

[0104] Zone 2, Section 4 (305℃): The material temperature is lowered to near the Tg of PPESK. The viscosity of the resin begins to increase significantly in this zone, transitioning from a viscous flow state to a highly elastic state.

[0105] Function: While maintaining a certain degree of fluidity, the resin begins to initially set. The pressure in this zone mainly serves to maintain the shape and continue defoaming, ensuring that the product's cross-sectional dimensions transition stably to the final specifications.

[0106] Zone 3 (200℃): In this zone, cooling water is pumped in by a mold temperature controller to force-cool the profile at a rate of 8℃ / min. The purpose is to rapidly reduce the temperature of the PPESK resin below its glass transition temperature (Tg), causing it to transition from a viscous flow state to a glassy state. The relatively fast rate of 8℃ / min is chosen to achieve a "quenching" effect, freezing the PPESK molecular chains before they have sufficient time to relax and achieve localized ordered alignment, forming a non-equilibrium glassy state. This state endows the profile blank with excellent reheat softening and reshaping capabilities during subsequent molding.

[0107] (7) Traction and cutting Traction Machine: A tracked, double-clamping traction machine is adopted. Both its upper and lower tracks are covered with high-temperature resistant polyurethane pads to provide tremendous clamping force without damaging the product surface. The traction machine is driven by a servo motor, with its speed stably controlled at 0.6 m / min and fluctuation less than ±0.5%. The traction force is monitored in real time by a pressure sensor and is stable at around 2100 N.

[0108] Online monitoring and cutting: At the end of the production line, a laser diameter gauge monitors the product dimensions in real time. Then, an automatic flying saw cuts the continuous profile to the required length.

[0109] Ultimately, the produced profiles have a smooth, mirror-like surface and precise dimensions of 12.00mm × 2.31mm ± 0.05mm.

[0110] S5. Integrated molding This step aims to use high-quality pultruded profile blanks to manufacture a final product with a complex three-dimensional anatomical shape and functional fixing holes through precision thermoforming.

[0111] (1) Billet preparation and preheating Blank Calculation: Calculate the volume of the final pultrusion plate based on its 3D model. The blank volume should be approximately 5% larger than the net volume of the mold cavity to compensate for material flow and ensure effective molding pressure. Accordingly, cut the pultruded profile into blanks measuring 105mm (length) × 12mm (width) × 2.31mm (thickness).

[0112] Preheating: Place the billet evenly on a high-temperature resistant tray and put it into a forced-circulation air oven. Set the preheating temperature to (340±5)℃, which is much higher than the Tg of PPESK, allowing the entire billet to soften uniformly and quickly to a highly elastic / viscous flow state. Set the preheating time to 8 minutes to ensure that the core in the thickness direction also reaches the set temperature. The purpose of preheating is to reduce the deformation resistance of the billet in the mold, so that the subsequent molding mainly completes the "shape change" rather than "densification", thereby protecting the fiber structure.

[0113] (2) Precision mold system The mold consists of an upper mold, a lower mold, a mold core system, a heating and cooling system, and an ejection system.

[0114] Mold cavity design and machining: The mold cavity is precisely milled on mold steel using a five-axis CNC machine tool, based entirely on the digital anatomical model of the radius and ulna bone plate. The thermal shrinkage rate (0.4%) of PPESK material when cooled to room temperature was fully considered during the design, and the mold cavity dimensions were accurately compensated.

[0115] Core System (Critical): The core used to form the fixing hole is made of tungsten-cobalt cemented carbide (YG15) with a heat treatment hardness of HRA≥92 to withstand enormous lateral pressure. The working section of the core is designed with a 1.5° draft angle, and the top is machined with a 0.15mm radius to reduce stress concentration and facilitate demolding. The core has an independent hydraulic core-pulling mechanism, driven by a hydraulic cylinder inside the mold, which can accurately and smoothly pull it out before the main mold opens, greatly protecting the fragile hole wall forming surface.

[0116] Temperature control system: The mold is equipped with a cylindrical heating rod and a spiral cooling channel. Zoned temperature control technology ensures uniform temperature in the mold cavity and core.

[0117] (3) Molding process Mold preheating and filling: Start the mold temperature controller and heat the mold to (300±5)℃ and keep it stable. The purpose of mold preheating is to reduce the temperature difference with the high-temperature blank (340℃) and prevent the blank from curing too early. The mold preheating temperature of 300℃ and the blank preheating temperature of 340℃ form a 40℃ temperature difference, which avoids rapid cooling of the blank surface and guides the resin to flow in an orderly manner using the temperature gradient, resulting in the best filling effect.

[0118] If the mold is preheated to 340℃, the same temperature as the billet, no heat exchange will occur after the billet is placed in. However, when molding begins, the mold needs to be closed and pressurized. If the temperature of the billet remains high during the pressing process, and the resin viscosity is too low, the fibers may be dispersed or misaligned. The temperature difference creates a temperature gradient, allowing the resin to flow orderly from the high-temperature interior of the billet to the low-temperature mold wall, which helps to fill the details of the mold cavity (such as the cavity). If the mold and the billet are at the same temperature, the flow driving force is only pressure, which can easily lead to turbulence or disordered fiber orientation, but is also more energy-efficient. The operator uses a special fixture to quickly and accurately place the preheated billet into the predetermined position in the lower mold cavity.

[0119] Mold closing and first-stage pressurization (flow filling): The press starts closing the mold at a relatively low speed (15 mm / s). As the upper and lower molds are about to contact the blank, the speed is further reduced to achieve smooth contact.

[0120] After contact, the pressure linearly increases to 5 MPa within 20 seconds and is maintained for 30 seconds.

[0121] The purpose of this stage is to allow the softened billet to slowly and smoothly fill all corners of the mold cavity, like a piece of soft clay, under relatively low pressure, especially in the areas where the joint plates gradually thin out at both ends. The pressure holding process is to allow sufficient time for air to escape from the venting channels within the mold cavity and to relax the material stress.

[0122] Second stage of pressurization (hole stage forming): After the first stage of pressure holding is completed, the pressure is gradually increased to the final 12MPa within 30 seconds.

[0123] Simultaneously, the mold temperature is raised from 300℃ to 350℃ using a mold temperature controller. This temperature is higher than the Tg of PPESK, providing sufficient energy for the molecular chains to move, promoting full molecular chain reorganization and physical entanglement, thereby achieving optimal mechanical properties and dimensional stability.

[0124] The material is held at 12 MPa pressure and 350°C for 40 minutes. This is the most critical thermoforming stage. Under high pressure, the material undergoes significant plastic flow. The main body of the blank is pressed into all parts of the mold cavity, while the material around the mold core is squeezed outwards, thus forming a dense, fixed-hole structure that is integrally bent and wrapped by continuous three-dimensional braided fibers. The fibers are not cut, but rather the structure is rearranged.

[0125] Cooling and demolding: After the pressure holding period, heating is immediately stopped and the cooling system is activated. Cooling water flows through the mold channels at a set flow rate, controlling the mold's cooling rate to approximately 3°C / min. Slow cooling is used to reduce internal stress caused by temperature gradients and prevent warping or deformation of the product. Throughout the cooling process, a low pressure of 8 MPa is maintained to constrain the product's shape.

[0126] Cooling stops when the mold temperature drops to 180℃ (which is far below the Tg of PPESK).

[0127] Core pulling and mold opening: First, activate the hydraulic system to smoothly and vertically pull the mold core back. Then, the press opens the mold. Finally, the ejection mechanism actuates, ejecting the finished bone plate from the mold cavity.

[0128] (4) Post-processing After the product is removed, use a micro-grit wheel or special tools to trim any tiny burrs caused by the mold parting surface. Then, polish the surface manually or mechanically with sandpaper of different grits. Finally, clean, sterilize, and package the product.

[0129] Example 2: Fabrication of carbon fiber / PPESK composite radius and ulna bone plates (for radius and ulna fracture fixation) - Pre-drilled hole weaving process The matrix material in this embodiment is the same as that in embodiment 1. The difference is that the three-dimensional weaving stage adopts a pre-reserved hole process, the pultrusion adopts a low compression ratio scheme, and the molding stage uses a die core to refine the hole size.

[0130] S1 and S3 are the same as in Example 1; S2. Three-dimensional woven prefabricated structure: A four-way three-dimensional braiding machine is used, with the braiding angle set at ±20° (a smaller braiding angle is beneficial for providing a higher axial modulus).

[0131] Precast shape: Woven into a solid plate-like structure with a cross-section of 12mm × 2.8mm. During the weaving process, based on the location of the fixing holes in the bone plate (e.g., 4–6 holes per plate, 2.7mm in diameter), a pre-drilled hole weaving technique is used (e.g., temporarily avoiding fibers in this area or using a mandrel to temporarily leave channels), directly weaving out the outline of the fixing holes. The fiber volume fraction of the precast is controlled at 48%.

[0132] S4. Melt impregnation and pultrusion shaping The structure of the molten resin supply unit, the mechanically stirred molten impregnation tank 2, and the temperature control and stirring parameters are all the same as in Example 1. The temperature of the molten resin in the impregnation tank is stable at 360±5℃, and the stirring speed is 150rpm.

[0133] (1) Impregnation process The woven preform is drawn into the impregnation tank at a constant speed of 0.8 m / min, and the impregnation time is about 112.5 seconds, achieving deep impregnation at the single filament level between and within the fiber bundles.

[0134] (2) Pultrusion die 6: The die structure is the same as in Example 1, and adopts a low compression ratio design: the cavity thickness of pultrusion die 6 is compressed from the preform thickness of 2.8mm to 2.6mm, with a compression ratio of about 7%. Due to the low compression ratio, the reserved hole remains open after pultrusion, and the diameter is slightly reduced from 2.7mm to about 2.5mm, while the roundness remains basically unchanged. During molding, the die core is refined to the design size.

[0135] (3) Three-zone temperature setting The temperature settings for the three zones of the mold are the same as in Example 1: Zone 1: 340℃, Zone 2: 305℃, Zone 3: 200℃; Zone 3, Zone 5, has a cooling rate of approximately 8℃ / min, achieving quenching-type cooling.

[0136] (4) Traction and cutting Traction Machine: A tracked, double-clamping traction machine is adopted. Both its upper and lower tracks are covered with high-temperature resistant polyurethane pads to provide tremendous clamping force without damaging the product surface. The traction machine is driven by a servo motor, with its speed stably controlled at 0.6 m / min and fluctuation less than ±0.5%. The traction force is monitored in real time by a pressure sensor and is stable at around 1100 N.

[0137] Online monitoring and cutting: At the end of the production line, a laser diameter gauge monitors the product dimensions in real time. Then, an automatic flying saw cuts the continuous profile to the required length.

[0138] In this embodiment, since the preform already has fixing holes, a low compression ratio pultrusion process is used to avoid excessive radial pressure causing the holes to close.

[0139] Pultruded profile dimensions: 12.00mm × 2.60mm ±0.05mm S5. Integrated molding This step aims to use high-quality pultruded profile blanks to manufacture a final product with a complex three-dimensional anatomical shape and functional fixing holes through precision thermoforming.

[0140] (1) Billet preparation and preheating Blank Calculation: Calculate the volume of the final pultrusion plate based on its 3D model. The blank volume should be approximately 5% larger than the net volume of the mold cavity to compensate for material flow and ensure effective molding pressure. Accordingly, cut the pultruded profile into blanks measuring 105mm (length) × 12mm (width) × 2.60mm (thickness).

[0141] Preheating: Place the billet evenly on a high-temperature resistant tray and put it into a forced-circulation air oven. Set the preheating temperature to (340±5)℃, which is much higher than the Tg of PPESK, allowing the entire billet to soften uniformly and quickly to a highly elastic / viscous flow state. Set the preheating time to 8 minutes to ensure that the core in the thickness direction also reaches the set temperature. The purpose of preheating is to reduce the deformation resistance of the billet in the mold, so that the subsequent molding mainly completes the "shape change" rather than "densification", thereby protecting the fiber structure.

[0142] (2) Precision mold system The mold structure is consistent with that of Example 1. The mold cavity is processed according to the anatomical model of the radius and ulna bone plate and compensated for 0.4% heat shrinkage. The fixed hole mold core is made of YG15 cemented carbide, with a 1.5° draft angle in the working section, a 0.15mm radius at the top, and an independent hydraulic core pulling mechanism.

[0143] (3) Detailed explanation of the molding process Mold preheating and filling: Start the mold temperature controller and heat the mold to (300±5)℃ and keep it stable. The mold preheating temperature of 300℃ and the billet preheating temperature of 340℃ form a 40℃ temperature difference, which avoids rapid cooling of the billet surface and guides the resin to flow in an orderly manner by utilizing the temperature gradient, resulting in the best filling effect.

[0144] Operators use special fixtures to quickly and accurately place the preheated blank into the predetermined position in the lower mold cavity, ensuring that the reserved hole is precisely aligned with the mold core.

[0145] Mold closing and first stage pressurization (flow filling): The press closes the mold at a speed of 15mm / s, and slows down to make smooth contact when it approaches the blank; within 20 seconds after contact, the pressure rises linearly to 5MPa, and is held for 30 seconds to complete the filling and venting of the mold cavity, so that the blank can smoothly fill all parts of the mold cavity, especially the gradually thinning areas at both ends of the joint plate.

[0146] Second stage of pressurization (hole stage forming): After the first stage of pressure holding, the pressure is gradually increased to 12 MPa within 30 seconds, while the mold temperature is raised to 350℃. The mold is then held at this temperature and pressure for 40 minutes. During the pressure holding process, the mold core is used to refine the pre-reserved holes, correcting the hole shape deviations generated during pultrusion. At the same time, the material undergoes plastic flow, forming a fixed hole structure that is entirely wrapped by continuous three-dimensional woven fibers, with the fibers remaining continuous and uncut.

[0147] Cooling and demolding: After the pressure holding period, heating is immediately stopped and the cooling system is activated. Cooling water flows through the mold channels at a set flow rate, controlling the mold's cooling rate to approximately 3°C / min. Slow cooling is used to reduce internal stress caused by temperature gradients and prevent warping or deformation of the product. Throughout the cooling process, a low pressure of 8 MPa is maintained to constrain the product's shape.

[0148] Cooling stops when the mold temperature drops to 180℃ (which is far below the Tg of PPESK).

[0149] Core pulling and mold opening: First, activate the hydraulic system to smoothly and vertically pull the mold core back. Then, the press opens the mold. Finally, the ejection mechanism actuates, ejecting the finished bone plate from the mold cavity.

[0150] (4) Post-processing After trimming, polishing, and cleaning, the finished bone plate is obtained. The subsequent sterilization and packaging process is the same as in Example 1.

[0151] Example 3: Preparation of carbon fiber / poly(aryl ether nitrile ketone) (PPENK) composite bone plate In this embodiment, the matrix is ​​replaced with poly(arylethernitrile ketone) (PPENK) resin.

[0152] S1 is the same as in Example 1; S2. Three-dimensional woven prefabricated structure: A four-way three-dimensional braiding machine was used, with the braiding angle set at ±18°, to weave a solid plate-shaped preform with a cross-section of 12mm × 3mm. By controlling the tension of the carbon fiber bundles and the braiding density, the fiber volume fraction of the woven preform was controlled at 50%.

[0153] S3. Solution impregnation: Materials: T700SC-12K-50C carbon fiber bundles from Toray Industries, Japan. The resin is PPENK resin synthesized by the Special Engineering Plastics Research Center of Jilin University, with an intrinsic viscosity of 0.50 dL / g and a Tg value of 275℃.

[0154] Impregnation solution preparation: PPENK particles and N-methylpyrrolidone (NMP) solvent are mixed at a weight ratio of 32:68 and mechanically stirred at 90°C for 7 hours until a uniform, transparent, bubble-free solution is formed.

[0155] Impregnation process: The three-dimensional braided preform obtained in S2 is completely immersed in the above impregnation solution and impregnated at 80~100°C for no less than 60 minutes (70 minutes in this embodiment). During this period, mechanical stirring or ultrasonic vibration is used to ensure that the resin solution fully penetrates into the fiber bundles and the gaps between the monofilaments inside the preform.

[0156] Drying: The impregnated 3D woven preform is immediately placed in an 8-meter-long, three-zone hot air circulating drying oven. The temperature profile is strictly set as follows: Zone 1 110℃, Zone 2 190℃, Zone 3 250℃. The total residence time of the 3D woven preform in the oven is approximately 4.5 minutes. This process aims to completely evaporate most of the solvent and allow the PPENK resin to partially gel.

[0157] The final impregnated three-dimensional woven preform has a resin weight content of 37±2%. This three-dimensional woven preform is dry, non-sticky, and has a certain degree of flexibility, and can be wound onto a reel and stored at room temperature for later use.

[0158] S4. Melt impregnation and pultrusion shaping (1) Molten Resin Supply Unit The core equipment is a co-rotating twin-screw extruder 1 with a screw diameter of 40mm and a length-to-diameter ratio of 40:1. The screw has a modular configuration, including a conveying section, a melting section, a mixing section, and a metering conveying section.

[0159] Temperature control system: The extruder extrusion temperature is set to 370℃, using PID intelligent control with an accuracy of ±1.0℃.

[0160] Feeding system: PPENK resin granules are continuously and precisely added through a loss-in-weight metering feeder, and the feeding rate is controlled in conjunction with the profile linear density and the target fiber volume fraction.

[0161] (2) Mechanically stirred melt impregnation tank 2 The tank structure, heating method, and insulation structure are the same as in Example 1; the stirrer adopts an inclined blade turbine-type stirring paddle, made of Inconel 600 high-temperature nickel-based alloy, and uses a magnetic coupling transmission system.

[0162] To meet the viscosity and impregnation requirements of the PPESK melt, the stirring speed was set to 180 rpm. At this speed, the melt generates appropriate shearing and circulation, creating a comprehensive scouring and kneading effect on the preform while preventing air entrainment through turbulence. The temperature of the molten resin in the tank was stabilized at 360±5℃. Ceramic guide rollers were used to guide the preform through the resin in an "S" shaped path, extending the effective impregnation path.

[0163] (3) Detailed explanation of the impregnation process The woven preform is drawn into the impregnation tank at a constant speed of 0.7 m / min. In the molten PPENK at 370±3℃, the solution-based resin contained in the preform quickly softens and melts, fusing with the resin in the tank to form a homogeneous continuous phase. During the impregnation time of about 113 seconds, the molten resin is forced to penetrate into the tiny gaps inside the preform, achieving deep wetting at the monofilament level between and within the bundle, and the preform reaches a resin supersaturation state.

[0164] (4) Pultrusion die 6 structure Pultrusion Die 6: Employs a monolithic carbide die. The die cavity cross-section resembles a bone plate structure, divided into three functional zones from the inlet to the outlet. Its dimensions are precisely calculated and rheologically simulated. Entry region (convergence region): The cross-section gradually shrinks, applying initial compression to the material.

[0165] Intermediate zone (parallel zone): The cross-section is constant, and it is the main area for compaction and wetting.

[0166] Export area (sizing area): The final finishing area to ensure the final dimensional accuracy and surface finish of the product.

[0167] Heating and Cooling: The mold is covered by three independent heating jackets (corresponding to zones one, two, and three), using ceramic heating rods with uniform power density. Each heating jacket is equipped with an independent PID temperature controller and thermocouple, with a temperature control accuracy of ±1.5℃. Cooling channels are also drilled inside zone three of the mold, connected to a high-precision mold temperature controller for rapid and controllable cooling.

[0168] (5) Three-zone temperature setting Zone 3 (365℃): The temperature is much higher than the Tg of PPENK. The resin maintains a low viscosity viscous flow state and completes the final wetting and bubble removal under high pressure shear flow. It is the key section to achieve low porosity.

[0169] Zone 2, Section 4 (325℃): As the material temperature decreases, the resin viscosity increases significantly, transitioning from a viscous flow state to a highly elastic state. While maintaining moderate fluidity, it initially sets and stabilizes the cross-sectional dimensions.

[0170] Zone 5 (220℃): The PPENK molecular chains are quenched and cooled at a rate of about 7℃ / min through a forced cooling system, freezing them before they can fully relax and arrange themselves in an orderly manner, forming a non-equilibrium glass structure, which preserves excellent thermoplastic reshaping ability for subsequent molding.

[0171] (6) Traction and Cutting Traction Machine: A tracked, double-clamping traction machine is adopted. Both its upper and lower tracks are covered with high-temperature resistant polyurethane pads to provide tremendous clamping force without damaging the product surface. The traction machine is driven by a servo motor, with its speed stably controlled at 0.7m / min. The traction force is monitored in real time by a pressure sensor and is stable at around 2300N.

[0172] Online monitoring and cutting: At the end of the production line, a laser diameter gauge monitors the product dimensions in real time. Then, an automatic flying saw cuts the continuous profile to the required length.

[0173] Ultimately, the produced profiles have a smooth, mirror-like surface and precise dimensions of 12.00mm × 2.31mm ± 0.05mm.

[0174] S5. Integrated molding This step aims to use high-quality pultruded profile blanks to manufacture a final product with a complex three-dimensional anatomical shape and functional fixing holes through precision thermoforming.

[0175] (1) Billet preparation and preheating Blank Calculation: Calculate the volume of the final pultrusion plate based on its 3D model. The blank volume should be approximately 5% larger than the net volume of the mold cavity to compensate for material flow and ensure effective molding pressure. Accordingly, cut the pultruded profile into blanks measuring 105mm (length) × 12mm (width) × 2.31mm (thickness).

[0176] The blanks are evenly placed on a high-temperature resistant tray and preheated in a forced-circulation air oven at 355±5℃ for 10 minutes to soften the blanks to a highly elastic / viscous flow state, thereby reducing subsequent deformation resistance and protecting the fiber structure.

[0177] (2) Precision mold system The mold structure is the same as in Example 1. The mold cavity is machined according to the anatomical model and compensates for the thermal shrinkage rate. The fixed hole mold core is made of YG15 cemented carbide and is equipped with an independent hydraulic core pulling mechanism. The mold has a built-in cylindrical heating rod and spiral cooling water channel for zoned temperature control.

[0178] (3) Molding process Mold preheating and loading: Start the mold temperature controller to heat the mold to 320±5℃ and keep it stable. The mold and the blank will form a temperature difference of about 35℃, which will guide the resin to flow in an orderly manner and avoid the fibers from being scattered.

[0179] Operators use special clamps to quickly and accurately place the preheated blank into the predetermined position in the lower mold cavity.

[0180] Mold closing and first stage of pressurization: The press closes the mold at a speed of 15mm / s, and slows down to make smooth contact when it approaches the blank; the pressure rises linearly to 5MPa within 20 seconds, and is held for 35 seconds to complete the filling and venting of the mold cavity.

[0181] Second stage of pressurization: After the first stage of holding pressure is completed, the pressure is gradually increased to 13MPa within 30 seconds, and the mold temperature is raised to 390℃. Under this condition, the pressure is held for 50 minutes to allow the material to fully plastically flow and form a fixed hole structure with continuous fiber surrounding it. At the same time, the resin molecular chains are fully reorganized and entangled to ensure mechanical properties and dimensional stability.

[0182] Cooling and demolding: After the pressure holding is completed, stop heating, turn on the cooling system, control the cooling rate to about 2℃ / min, maintain 8MPa constraint pressure during the cooling process to reduce internal stress and prevent warping; after the mold temperature drops to 200℃ (far below the Tg of PPENK), first pull out the mold core smoothly, and then open the mold to eject the finished product.

[0183] (4) Post-processing After the product is removed, use a micro-grit wheel or special tools to trim any tiny burrs caused by the mold parting surface. Then, polish the surface manually or mechanically with sandpaper of different grits. Finally, clean, sterilize, and package the product.

[0184] Comparative Example 1: Bone plate prepared by direct molding process of three-dimensional braided PPESK preform Using the same three-dimensional woven PPESK preform (48% fiber volume fraction, 12mm × 3mm cross section) as in Example 1, bone plates of the same specifications were prepared according to conventional direct molding processes in the art.

[0185] The dried woven preform and PPESK resin film were alternately laid into the bone plate mold. The mold was heated to 360°C and gradually pressurized to 12MPa for 60 minutes. Then, it was cooled to 180°C at a rate of 3°C / min for demolding. The fixing holes were then machined by mechanical drilling.

[0186] Experimental Example The products prepared in Examples 1-3 and Comparative Example 1 were subjected to experimental performance tests. The fiber volume fraction was tested according to ASTM D3171 standard, the porosity was determined by micro-CT scanning, the flexural strength and flexural modulus were tested according to ASTM D790 standard, and the interlaminar shear strength (ILSS) was tested according to ASTM D2344 standard. The results are shown in Table 1.

[0187] Table 1 Test results of each embodiment and comparative example

[0188] In summary, Examples 1 and 3 of this application represent standard process schemes without pre-reserved holes. High compaction is achieved through high compression ratio pultrusion, with the fiber volume fraction stable in the range of 62% to 64% and the porosity controlled below 0.4%. Example 2 employs a process route of pre-reserved hole weaving + low compression ratio pultrusion. By appropriately reducing the degree of compaction, higher fiber continuity around the holes is achieved. The fiber volume fraction can be adjusted to 48% to 55% according to the pore size, and the porosity is ≤1.0%. Its overall performance is still significantly better than the traditional direct molding process under the same conditions.

[0189] Specifically, Example 1 (standard process without pre-drilled holes) adopts an "integrated molding direct hole formation" approach. The pultruded profile itself is a complete, solid sheet material without holes. During the molding stage, a fixed hole structure is extruded in one step through a hard alloy core built into the mold, while the material softens and is under pressure. The fibers around the holes naturally rearrange with the plastic flow of the resin, continuously bending and wrapping around the sidewall of the core. There is no step of mechanical drilling to cut the fibers throughout the process, ultimately achieving the effect of "fiber without cutting". This solution focuses on high performance and high efficiency, with simpler process steps and higher static mechanical properties. It is suitable for conventional bone plate products with high requirements for strength and modulus and a pursuit of mass production efficiency.

[0190] Example 2 (Pre-drilled Hole Weaving Process) adopts a route of "weaving pre-drilled channels + low compression ratio pultrusion for shape preservation + molding finishing". In the three-dimensional weaving stage, the channels are pre-drilled using a mandrel. If the same high compression ratio as in Example 1 were used, the radial pressure would directly collapse and deform the channels, making it impossible to retain the complete pre-drilled hole structure. Therefore, to maintain the channel shape, a low compression ratio design is used to avoid channel collapse. Finally, in the molding stage, the size and roundness of the holes are calibrated using a mandrel. The peri-hole fibers are continuously arranged along the channels from the weaving stage without being cut throughout the process. The fiber continuity and orientation integrity are higher than the molding rearrangement scheme. This scheme emphasizes high fatigue and high reliability, with more perfect peri-hole fiber continuity, making it suitable for orthopedic implant scenarios with extremely high requirements for cyclic loads and fatigue life (such as long-term fixation implants in weight-bearing areas).

[0191] Comparing Example 2 with Comparative Example 1, it can be seen that the fiber volume fractions are similar, but the product prepared by the pultrusion process of the present invention has a bending strength of about 21% and an interlaminar shear strength of about 31%. This proves that even with a low compression ratio pre-drilled hole scheme, the advantages of the pultrusion process in terms of regular fiber axial orientation and uniform matrix wetting are still significantly better than the traditional three-dimensional braiding direct molding process.

[0192] Furthermore, the preparation method of this application is not only applicable to radius and ulna bone plates, but can also be used to prepare various orthopedic internal fixation implants such as intramedullary nails, spinal fixation rods, interbody fusion devices, and pelvic fixation plates by adjusting the cross-sectional shape, weaving parameters, and molding die structure of the three-dimensional woven preform. The core process principle and effect of "three-dimensional weaving-solution impregnation-melt pultrusion-integrated molding" are consistent with the above embodiments and are all within the protection scope of this invention.

[0193] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A carbon fiber composite implant, characterized in that, It is prepared by comprising a carbon fiber reinforcing phase and a resin matrix, wherein the carbon fiber reinforcing phase is a three-dimensional braided body and the resin matrix is ​​a polyarylene ether resin of the naphthalene-biphenyl type; The carbon fiber composite implant has a fiber volume fraction of 50%-65% and an internal porosity of ≤1.0%; the carbon fiber composite implant is provided with fixing holes, and the carbon fibers are continuously arranged around the fixing holes without being cut.

2. The carbon fiber composite implant according to claim 1, characterized in that, The carbon fiber composite implant is a bone plate; The flexural modulus of the bone plate is 25~55GPa, which matches the elastic modulus of human cortical bone.

3. A method for preparing a carbon fiber composite implant as described in any one of claims 1-2, characterized in that, Includes the following steps: (1) Three-dimensional weaving: Carbon fiber bundles are woven into a three-dimensional weaving preform by a three-dimensional weaving process, wherein the fiber volume fraction of the three-dimensional weaving preform is 45%~50%; (2) Solution impregnation: Dissolve the naphthalene-biphenyl type polyarylene ether resin in an organic solvent to prepare an impregnation solution. Place the three-dimensional braided preform obtained in step (1) into the impregnation solution for impregnation treatment, and then dry to remove the solvent to obtain a three-dimensional braided preform with a resin weight content of 35%~40% after solution impregnation. (3) Melt impregnation and pultrusion shaping: The three-dimensional braided preform obtained in step (2) is drawn through a melt resin bath at a temperature of T1 for melt impregnation, and then passed into a pultrusion mold for shaping; The pultrusion die is divided into three zones along the traction direction: a first zone, a second zone, and a third zone. The temperature of the first zone of the pultrusion die is T2, the temperature of the second zone is T3, and the temperature of the third zone is T4. Where T1 and T2 are Tg+50℃~Tg+100℃, T3 is Tg+30℃~Tg+80℃, and T4 is Tg-100℃~Tg-50℃; and T2≥T3, T2 T3≤40℃, where Tg is the glass transition temperature of the naphthalene-biphenyl type polyarylene ether resin; (4) Integrated molding: After the pultruded profile blank is preheated to temperature T5, it is placed into the molding mold and pressed and cured at temperature T6 to produce a finished implant with fixing hole in one step. Where T5 is Tg+80℃ ~ Tg+115℃, and T6 is Tg+85℃ ~ Tg+115℃.

4. The preparation method according to claim 3, characterized in that, The weight ratio of the naphthalene-biphenyl polyarylene ether resin to the organic solvent in step (2) is (30~35):(70~65).

5. The preparation method according to claim 4, characterized in that, The organic solvent in step (2) is N-methylpyrrolidone, and the polyarylene ether resin is polyarylene ether sulfone ketone or polyarylene ether nitrile ketone.

6. The preparation method according to claim 3, characterized in that, In step (1), the three-dimensional weaving angle is ±15°~±25°.

7. The preparation method according to claim 3, characterized in that, The melt impregnation described in step (3) is carried out with the assistance of mechanical stirring at a speed of 100~300 rpm.

8. The preparation method according to claim 3, characterized in that, In step (3), the immersion time of the three-dimensional braided preform in the molten resin bath shall not be less than 60s.

9. The preparation method according to claim 3, characterized in that, The third zone of the pultrusion die in step (3) is equipped with a forced cooling system, and the cooling rate of the profile is controlled at 5~10℃ / min.

10. The preparation method according to claim 3, characterized in that, In step (4), the holding pressure during the molding process is 10-15 MPa, and the holding time is 40-60 min.

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