Integrated weaving method of multilayer hollow tubular fabric and its composite fabric

Abstract

This invention relates to a method for integrated weaving of multilayer hollow tubular fabrics and the resulting composite fabric. The method involves online weaving to form a coaxially nested core layer, at least one intermediate layer, and a surface tubular skeleton. A first-stage heat treatment using core-sheath structure yarns achieves initial interlayer bonding. Subsequently, an ultrasonically treated zirconium salt solution is injected into the inner cavity and / or interlayer cavities. Under pressure, a programmed gradient temperature rise and electrolytic coupling process is used to reduce and oxidize zirconium ions in situ, generating highly dispersed nano-zirconia on the inner wall of the cavity and the surface of the Z-axis reinforcing fibers, which then tightly bonds with the fabric matrix. This method solves the problems of weak interlayer bonding and uneven dispersion of nanomaterials, achieving structural and functional integration. The resulting composite fabric exhibits high interlayer shear strength and excellent overall performance.

Description

Technical Field

[0001] This application relates to the field of composite material preparation technology, and in particular to an integrated weaving method for multilayer hollow tubular fabrics and the composite fabric thereof. Background Technology

[0002] Textile composite materials mainly refer to new materials prepared through composite processes using high-performance fibers as reinforcement and resin as matrix. They have advantages such as high specific strength, high specific modulus, and strong designability. In recent years, tubular textile composite materials have become increasingly popular and can be widely used in the production of various pipes, pipe shells, bushings, ultra-high temperature insulation pipes, and various structural supports.

[0003] Traditional methods for preparing tubular fabrics typically involve layered weaving or winding followed by bonding. This approach is not only complex and inefficient, but also often results in insufficient interlayer bonding strength, leading to delamination and impacting the mechanical properties and lifespan of the final product. Furthermore, to improve the overall performance of tubular fabrics, such as abrasion resistance, corrosion resistance, and flame retardancy, functional materials are often introduced. However, uniformly and stably incorporating functional nanomaterials into multilayer tubular fabrics, particularly achieving a tight bond with the fabric matrix, remains a significant challenge. Existing methods such as impregnation and coating often fail to guarantee the dispersion and bonding strength of nanomaterials, easily leading to material detachment or performance degradation.

[0004] Chinese patent CN116442536B discloses a dual-pressure composite method for tubular fabrics, comprising: S1: placing an outer membrane on a flat surface and injecting a first pressure into the outer membrane through a first opening, causing the outer membrane to be stretched; S2: inserting an inner membrane into a flexible tubular fabric first, and then inserting the flexible tubular fabric into the outer membrane through the first opening; S3: injecting a second pressure into the inner membrane through a second opening, causing the inner membrane to be stretched, at which point the outer and inner membranes tightly cover the surface of the flexible tubular fabric; S4: removing the first pressure while continuously injecting the second pressure; S5: heating the entire model from the outside of the outer membrane using a heating device until the inner layer of the outer membrane and the outer layer of the inner membrane melt, impregnating the flexible tubular fabric; S6: injecting resin through the first opening while simultaneously drawing a vacuum through a third opening, allowing the resin to penetrate the interior of the flexible tubular fabric. This invention, based on a dual-pressure method, completes the composite of flexible tubular fabrics in one step, reducing the need for flipping the tubular fabric.

[0005] While the above solution addresses the technical issues of uneven dispersion and weak bonding of nanomaterials within tubular fabrics, which can lead to detachment or performance degradation, there are still challenges when the fabric structure is more complex, the interlayer cavities are extremely narrow, or there is a dense Z-axis reinforcement structure. In such cases, the high-concentration, high-viscosity zirconium salt electrolyte may not be able to fully and uniformly penetrate and wet all the predetermined cavities and fiber surfaces. This could result in uneven spatial distribution of the in-situ generation of nano-zirconia, affecting the consistency of the composite material's performance.

[0006] Therefore, we propose an integrated weaving method for multilayer hollow tubular fabrics and its composite fabric. Summary of the Invention

[0007] The purpose of this application is to provide an integrated weaving method for multilayer hollow tubular fabrics and its composite fabric, which aims to solve the problem in the prior art that it is difficult to guarantee the dispersion and bonding strength of nanomaterials, which can easily lead to material detachment or performance degradation.

[0008] To achieve the above objectives, this application provides a method for integrated weaving of multilayer hollow tubular fabrics, comprising the following steps:

[0009] S1. A core layer yarn, at least one intermediate layer yarn, and a surface layer yarn are provided; wherein the core layer and surface layer yarns are core-sheath structure yarns, and the sheath is a melt-bonded material; the intermediate layer yarns include at least non-thermally fusible high-performance fibers for forming a Z-axis reinforcement structure.

[0010] S2. On a special loom, a core tubular skeleton, at least one intermediate tubular skeleton, and a surface tubular skeleton are woven sequentially from the inside out to form a multi-layer tubular fabric blank.

[0011] S3. The multilayer tubular fabric blank obtained in step S2 is subjected to a first-stage heat treatment at a temperature equal to or slightly higher than the melting point of the skin material and a pressure of 0.1-0.3 MPa, so that the contact interfaces of each layer are initially melted and bonded to form a tubular fabric skeleton with a stable cavity structure.

[0012] S4. Inject a zirconium salt solution with a pH of 7-9 that has been ultrasonically treated into the inner cavity and / or interlayer cavities of the tubular fabric skeleton obtained in step S3; then place the tubular fabric skeleton in an electrolytic device that combines heating and pressurization functions, and perform programmed gradient heating and electrolytic coupling treatment while applying a pressure of 0.3-0.6 MPa.

[0013] The coupling process includes: applying an electric field simultaneously during the heating process and controlling the electrolysis temperature using a segmented heating method, so that zirconium ions undergo in-situ reduction-oxidation reaction in the solution to generate highly dispersed nano-zirconia on the inner wall of the cavity and the surface of the Z-direction reinforcing fiber, and using heat and pressure to promote its tight bonding with the fabric matrix, ultimately obtaining a composite tubular fabric that is integrally formed and internally composited with in-situ generated nano-zirconia.

[0014] Preferably, in step S4, the mass concentration of the zirconium salt solution is 45% to 70%, and the zirconium salt is selected from one or more of zirconium sulfate, zirconium nitrate, and zirconium chloride.

[0015] Preferably, in step S4, the segmented heating method includes: starting electrolysis at 25°C, heating to 35°C at a rate of 0.5°C to 2.5°C per minute and maintaining electrolysis for 10 to 15 minutes, and then heating to 45°C at a rate of 0.5°C to 2.5°C per minute and maintaining electrolysis for 30 to 80 minutes.

[0016] Preferably, in step S4, the initial voltage corresponding to the applied electric field is 3 to 5 volts, and the current density is 200 mA / cm² to 500 mA / cm².

[0017] Preferably, in step S4, the ultrasonic treatment of the zirconium salt solution is performed at a frequency of 20 kHz to 40 kHz for a duration of 25 min to 45 min.

[0018] Preferably, in step S1, at least a portion of the Z-direction reinforcing fibers are conductive fibers, which serve as the anode or cathode for electrolysis in step S4, so as to preferentially generate nano-zirconia on the fiber surface.

[0019] Preferably, the conductive fiber is carbon fiber or metal fiber.

[0020] Preferably, in step S4, the average particle size of the in-situ generated nano-zirconia is 10 to 50 nanometers.

[0021] Preferably, in step S4, a dispersant, a stabilizer, and a complexing agent are also added to the zirconium salt solution to regulate the morphology and dispersibility of nano-zirconia.

[0022] To achieve the above objectives, this application provides a multilayer composite hollow tubular fabric prepared according to any of the methods described above, wherein the fabric is internally composited with highly dispersed nano-zirconia with an average particle size of 10-50 nanometers, and the nano-zirconia forms a chemical or physical bond with the Z-axis reinforcing fibers and inner wall of the fabric, and its interlaminar shear strength is not less than 20 MPa.

[0023] The beneficial effects of the technical solution of this invention are as follows:

[0024] By employing core-sheath structure yarns and online weaving technology, combined with the first-stage heat treatment, the tubular skeletons of each layer are initially melted and bonded at the contact interface to form a stable cavity structure. This fundamentally solves the problem of insufficient interlayer bonding strength in traditional layered preparation methods, and improves the integrity and mechanical properties of the fabric.

[0025] A zirconium salt solution was ultrasonically treated, followed by programmed gradient heating and electrolytic coupling to generate highly dispersed nano-zirconia ions in situ within the fabric's internal cavities and on the surface of the Z-axis reinforcing fibers. This in-situ generation method avoids nanomaterial aggregation and ensures their uniform distribution within the fabric.

[0026] Applying pressure and heat simultaneously during electrolysis promotes the formation of a tight physical or chemical bond between the in-situ generated nano-zirconia and the fabric matrix (including the inner wall of the cavity and the Z-direction reinforcing fibers), effectively preventing the detachment of nanomaterials and thus significantly improving the overall performance of the composite fabric, such as wear resistance, corrosion resistance, and flame retardancy.

[0027] By precisely controlling process parameters such as pH, concentration, ultrasonic treatment parameters, electrolysis temperature, pressure, voltage, and current density of the zirconium salt solution, the particle size, morphology, and dispersibility of nano-zirconia can be effectively regulated, thereby preparing multilayer composite tubular fabrics with specific performance requirements. In particular, by introducing conductive fibers as electrodes, preferential formation of nano-zirconia in specific regions can be achieved, further optimizing the composite effect. Attached Figure Description

[0028] Figure 1 This is a schematic flowchart of an integrated weaving method for multilayer hollow tubular fabrics according to an embodiment of this application.

[0029] Figure 2 This is a schematic diagram of the structure of a multilayer hollow tubular fabric in one embodiment of this application;

[0030] Figure 3 This is a schematic diagram of the composite processing flow of the integrated weaving and forming method for multilayer hollow tubular fabrics in one embodiment of this application.

[0031] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0032] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0033] Furthermore, descriptions using terms such as "first" and "second" in this application are for descriptive purposes only (e.g., to distinguish identical or similar elements) and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include at least one feature. Additionally, technical solutions from different embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If a combination of technical solutions is contradictory or impossible to implement, such a combination should be considered nonexistent and not within the scope of protection claimed in this application.

[0034] Multilayer hollow tubular fabrics have broad application prospects in aerospace, automotive, chemical, and medical fields due to their unique structure and excellent properties. However, existing technologies generally face some technical challenges in the preparation of such fabrics.

[0035] Traditional methods for preparing tubular fabrics typically involve layered weaving or winding followed by bonding. This approach is not only complex and inefficient, but also often results in insufficient interlayer bonding strength, leading to delamination and affecting the mechanical properties and lifespan of the final product. Furthermore, to improve the overall performance of tubular fabrics, such as abrasion resistance, corrosion resistance, and flame retardancy, functional materials are often introduced. However, uniformly and stably incorporating functional nanomaterials into multilayer tubular fabrics, especially achieving tight bonding with the fabric matrix, remains a significant challenge. Existing methods such as impregnation and coating often fail to guarantee the dispersion and bonding strength of nanomaterials, easily leading to material detachment or performance degradation. Particularly in multilayer hollow tubular structures, effectively introducing nanomaterials into the internal cavities and interlayers, and achieving in-situ growth and tight bonding, is a pressing technological challenge.

[0036] See Figures 1-2 This invention proposes an integrated weaving and forming method for multi-layer hollow tubular fabrics, comprising the following steps:

[0037] S1 provides a core layer yarn 100, at least one intermediate layer yarn 300, and a surface layer yarn 400.

[0038] The core layer 100 and the outer layer yarn 400 are core-sheath structure yarns, with the sheath being a melt-bonded material. The intermediate layer yarn 300 includes at least non-thermally fusible high-performance fibers for forming the Z-direction reinforcement structure 200.

[0039] S2 is woven online from the inside out to form a coaxially nested core layer 100 tubular skeleton, at least one intermediate layer tubular skeleton and a surface layer tubular skeleton, to obtain a multi-layer tubular fabric blank.

[0040] S3 performs a first-stage heat treatment on the multilayer tubular fabric blank obtained in step S2 at a temperature equal to or slightly higher than the melting point of the skin material and a pressure of 0.1-0.3 MPa, so that the contact interfaces of each layer are initially melted and bonded to form a tubular fabric skeleton with a stable cavity structure.

[0041] See Figure 3 S4 involves in-situ nanocomposite treatment of the tubular fabric skeleton, specifically including the following sub-steps:

[0042] S4-1 Inject a zirconium salt solution with a pH of 7-9, which has been ultrasonically treated, into the inner cavity and / or interlayer cavities of the tubular fabric skeleton obtained in step S3; the mass concentration of the zirconium salt solution is 45%-70%, and the zirconium salt is selected from one or more of zirconium sulfate, zirconium nitrate, and zirconium chloride.

[0043] S4-2 places the tubular fabric skeleton in an electrolytic device that combines heating and pressurization functions, and performs programmed gradient heating and electrolytic coupling treatment while applying a pressure of 0.3-0.6MPa.

[0044] The coupling process involves simultaneously applying an electric field during the heating process, with an initial voltage of 3–5 volts and a current density of 200 mA / cm²–500 mA / cm²; and using a segmented heating method to control the electrolysis temperature.

[0045] The segmented heating method includes: starting electrolysis at 25°C, heating to 35°C at a rate of 0.5°C to 2.5°C per minute and maintaining electrolysis for 10 to 15 minutes, and then heating to 45°C at a rate of 0.5°C to 2.5°C per minute and maintaining electrolysis for 30 to 80 minutes.

[0046] During this process, zirconium ions undergo in-situ reduction-oxidation reaction under the action of an electric field, generating highly dispersed nano-zirconia on the inner wall of the cavity and the surface of the Z-direction reinforcing fiber, and tightly bonding with the fabric matrix, ultimately obtaining a composite tubular fabric that is integrally formed and internally composited with in-situ generated nano-zirconia.

[0047] In this embodiment, a multi-layered coaxial tubular skeleton is formed through a one-time online weaving process from the inside out. Combined with the synergistic effect of the core-sheath yarn melt bonding and the Z-axis reinforcing fibers, the interlayer structure is organically integrated. After the first stage of heat treatment, each layer forms a preliminary melt bond at the interface, effectively avoiding the delamination and peeling problems that are common in traditional laminated structures, and significantly improving the interlayer bonding strength and structural integrity. Furthermore, highly dispersed nano-zirconia is uniformly generated on the inner wall of the fabric cavity and the surface of the Z-axis fibers using an in-situ reduction-oxidation reaction of a zirconium salt solution under the coupling of an electric field and temperature. These nanoparticles are firmly bonded to the fiber matrix, significantly enhancing the high-temperature resistance, chemical stability, abrasion resistance, and corrosion resistance of the tubular fabric, while also endowing it with certain catalytic, filtration, or ion exchange functions.

[0048] Furthermore, the non-thermally fusible, high-performance Z-axis reinforcing fibers introduced in the intermediate layer not only support and connect the layers under heat treatment and pressure, but also synergize with the skin layer for fusion bonding. This allows the multi-layered cavity structure to maintain shape stability under complex stress environments, significantly improving its crush resistance and torsional resistance. Compared to traditional step-by-step manufacturing and post-composite processes, this invention integrates weaving, bonding reinforcement, and nanocomposite processes into a continuous process flow, reducing semi-finished product transfer and multiple processing steps, improving production efficiency, and lowering energy consumption and processing costs.

[0049] In one embodiment, the pH of the zirconium salt solution is adjusted in step S01 by adding an amine-containing organic compound, such as ethylenediamine or triethylamine.

[0050] In this embodiment, under a weakly alkaline environment, zirconium ions (Zr) 4 The hydrolysis and polymerization behavior of zirconium hydroxide (ZH⁺) was effectively controlled, avoiding the problems of rapid precipitation or formation of unstable zirconium hydroxide colloids that easily occur under acidic or strongly alkaline conditions. The amine-containing compound, acting as a mild alkali source and complexing agent, can undergo mild coordination with zirconium ions to form a more stable precursor solution system. This not only ensures the homogeneity of the solution during ultrasonic treatment and injection but also provides a controllable and uniform source of reactants for subsequent electrochemical in-situ reactions.

[0051] On the other hand, during programmed gradient heating electrolysis, the weakly alkaline environment combined with a segmented heating strategy facilitates the directional migration of zirconium ions driven by the electric field and their preferential adsorption on the fiber surface. The presence of amine groups may, to some extent, alter the double-layer structure at the electrode / solution interface, lowering the energy barrier for nanoparticle nucleation. Simultaneously, during heating, the amine compounds gradually decompose or desorb, and their release process coordinates with the reduction-oxidation steps of zirconium ions, promoting the layer-by-layer, ordered growth of zirconium dioxide (ZrO2) nanocrystals, thereby obtaining a nanocomposite coating with higher dispersibility and better crystallinity.

[0052] Furthermore, the nano-zirconia generated at the site not only physically adheres to the fiber surface, but in a weakly alkaline reaction environment, some hydroxyl (-OH) groups on the fiber surface may undergo more effective chemical reactions with the zirconium precursor or intermediate products, forming stronger interfacial bonds. This further enhances the bonding force between the nano-reinforcing phase and the fabric matrix (especially the Z-axis reinforcing fibers), facilitates stress transfer, and further improves the mechanical properties and durability of the composite material. Moreover, the selected organic amine compounds, such as ethylenediamine and triethylamine, can achieve relatively complete decomposition or participate in the reaction under the stated process conditions (temperature, electric field), and are unlikely to remain in the final product, reducing the need for post-processing.

[0053] In one embodiment, the zirconium salt solution in step S01 is further provided with a dispersant and a stabilizer, wherein the dispersant is selected from one or more of polyethylene glycol, polyvinyl alcohol, and polyacrylic acid, and the stabilizer is a combination of sodium dodecyl sulfate and a polyelectrolyte.

[0054] In this embodiment, a specific dispersant and stabilizer are synergistically introduced into the zirconium salt solution in step S01, resulting in a deep optimization of the physicochemical properties of the solution system. This complements the aforementioned pH adjustment strategy, jointly ensuring the high controllability and excellent repeatability of the in-situ nanocomposite process. It also significantly reduces the surface tension of the zirconium salt solution, allowing it to quickly and fully penetrate into the dense fiber gaps and interlayer cavities of the tubular fabric skeleton, and even coat the surface of the Z-axis reinforcing fibers. This ensures that the reaction interface (fiber surface) of the subsequent electrochemical reaction is maximized for exposure and utilization, fundamentally avoiding the problem of uneven distribution of nanocomposite materials caused by local enrichment or drying of the solution.

[0055] Specifically, polymeric dispersants such as polyethylene glycol (PEG), polyvinyl alcohol (PVA), or polyacrylic acid (PAA) can effectively isolate zirconium ion clusters and potential initial nanonuclei through steric hindrance, preventing Ostwald ripening or sedimentation during storage, ultrasonic treatment, and injection. Simultaneously, sodium dodecyl sulfate (SDS), as an anionic surfactant, adsorbs onto the particle surface, imparting a negative charge and further enhancing dispersion stability through electrostatic repulsion. The addition of polyelectrolytes allows for fine-tuning of the system's zeta potential based on their ionic properties (such as anionic sodium polyacrylate or cationic polydiallyldimethylammonium chloride), synergistically building a stronger electrostatic stability barrier with SDS. This dual stabilization mechanism of "steric hindrance + electrostatic double layer" enables high-concentration (45%~70%) zirconium salt solutions to maintain extremely low viscosity growth rates and excellent uniformity over extended periods, laying the foundation for uniform injection into complex cavity structures in multilayer fabrics.

[0056] Furthermore, during programmed gradient temperature electrolysis, the dispersant and stabilizer molecules adsorbed on the fiber surface can regulate the local concentration and diffusion rate of zirconium ions after reaching the fiber surface under the drive of the electric field, providing more and more uniform active sites for the nucleation of zirconium dioxide nanocrystals. The presence of polyelectrolytes may affect the orientation of crystal growth through the selective interaction between their functional groups and zirconium ions. This causes the formation process of nano-zirconia to evolve from "random deposition" to "directional assembly," thereby ensuring that the obtained nanocomposite coating has better dispersibility and a denser and more continuous bond with the fiber surface.

[0057] In one embodiment, the ultrasonic frequency in step S02 is 20kHz to 40kHz. The ultrasonic duration in step S02 is 25min to 45min.

[0058] In one preferred embodiment, the ultrasonic frequency in step S02 is 30 kHz and the ultrasonic time is 35 min.

[0059] In one embodiment, in step S03, at least a portion of the Z-axis reinforcing fibers in the tubular fabric skeleton are conductive fibers, such as carbon fibers or metal fibers, which directly serve as electrodes during electrolysis.

[0060] In this embodiment, when the conductive fiber is used directly as the electrode, the electric field lines can be distributed directly at an extremely high density on the surface of each conductive fiber and in the surrounding micro-region. This ensures that the migration path of zirconium ions under the action of the electric field is extremely short and the target is clear—directly tending towards the fiber surface serving as the electrode. Compared with the use of an external monolithic electrode, this "point-to-point" localized electrochemical action mode greatly improves the efficiency of the electrochemical reaction and the current utilization rate. The reaction interface is the fiber interface itself that needs to be reinforced. Therefore, the in-situ generated nano-zirconia can nucleate and grow on the fiber surface in the most direct and compact way, fundamentally ensuring the high uniformity and density of the nanocomposite layer on the Z-direction reinforced structure 200, and avoiding coating thickness differences caused by uneven electric field distribution.

[0061] Furthermore, conductive fibers (especially carbon fibers) possess abundant active functional groups and conductive networks on their surfaces. During electrolysis, the current flows directly through the fibers, causing specific electrochemical activation on their surfaces, potentially generating more active sites conducive to the heterogeneous nucleation of nanoparticles. Simultaneously, the in-situ electrochemical growth of nano-zirconia on the fiber electrode surface, during its initial nucleation process, may generate stronger electronic interactions and even chemical bonds with the carbon lattice or metal oxide layer on the fiber surface, forming a strong coupling interface between the fiber and nanoparticles. This interface not only exhibits bonding forces far exceeding physical adhesion but also enables the effective transfer of stress and electrical / thermal fields. This maximizes the synergistic reinforcing effect between the conductive fibers and the nano-functional phases, while the conductive fibers fulfill both structural reinforcement (Z-axis) and conductive (electrode) functions. Consequently, this significantly improves the overall mechanical properties (such as interlaminar shear strength and impact resistance) and functional stability of the composite fabric.

[0062] Furthermore, by setting some of the Z-axis fibers as built-in electrodes, the external electrolysis device can be simplified or redesigned. The device may no longer require complex built-in electrode networks or difficult-to-align contact devices; it only needs to ensure a reliable electrical connection with the conductive fiber bundles at the fabric ends. This reduces equipment complexity and the requirements for precise positioning of the fabric preform, improving process operability and repeatability. Simultaneously, since the electric field is naturally established from the inside out (or from specific layers) through the conductive fiber network, it is more conducive to ensuring the uniformity of the electrochemical environment within the entire three-dimensional fabric skeleton.

[0063] In one embodiment, the segmented heating method in step S03 includes the following steps:

[0064] S03-1 Before starting electrolysis, adjust the temperature inside the electrolysis device to 25℃;

[0065] S03-2 The temperature of step S03-1 is gradually increased to 35°C at a rate of 0.5°C to 2.5°C per minute;

[0066] When the temperature reaches the first stage temperature of 35℃, maintain this temperature and continue electrolysis for 10 to 15 minutes.

[0067] S03-4 After electrolysis in step S03-3 is completed, continue to raise the temperature to the final operating temperature of 45℃ at a rate of 0.5℃~2.5℃ per minute;

[0068] S03-5 Continue the electrolysis process for 30-80 minutes on the tubular fabric skeleton that has reached the final working temperature in step S03-4.

[0069] In this embodiment, the initial stage (25°C to 35°C and maintained electrolysis) corresponds to a mild "induction period" or "pre-nucleation period." Under the synergy of this relatively low temperature and electric field, zirconium ions or complex precursors migrating to the surface of the fibers (especially conductive fibers serving as electrodes) are fully adsorbed and form stable initial nucleation sites. The mild conditions at this stage avoid instantaneous, massive, and disordered nucleation caused by excessively rapid reactions, laying a uniform substrate for subsequent growth. The subsequent increase in temperature to 45°C and maintenance for a long period initiates the "steady-state growth period." The higher temperature provides sufficient energy to promote the controlled growth of the already formed nuclei through continued ion deposition, while the electric field continuously drives the replenishment of new precursors.

[0070] On the other hand, through two holding periods at 35℃ and 45℃, the continuous electrolysis not only allows the nanoparticles to continue growing, but more importantly, it promotes the "maturation" and rearrangement of the initially deposited particles. Under the continuous influence of the electric field and temperature, the interfacial energy between nanoparticles is optimized, the particle connections are tighter, and the overall density of the coating is improved. At the same time, the sufficient reaction time provided by the holding period allows the zirconium precursor or the generated zirconium oxide to have more opportunities to form stronger chemical bonds (such as MOC or MO-Si bonds) with the functional groups (such as hydroxyl groups) on the fiber surface, thereby significantly enhancing the interfacial bonding strength between the nanocoating and the fiber matrix, especially with the Z-axis conductive fibers that serve as electrodes.

[0071] Furthermore, a gradual heating rate of 0.5℃ to 2.5℃ per minute ensures dynamic coordination between system temperature changes, the migration and diffusion rate of reactants (zirconium ions) under the electric field, and the surface reaction rate. This also maintains a relatively stable ion concentration near the reaction interface throughout the temperature rise process, achieving a uniform increase in coating thickness and reducing internal stress caused by abrupt changes in the reaction rate. Simultaneously, the entire heating program (maximum 45℃) is carefully controlled within a relatively low temperature range, thereby maximizing the protection of the fabric skeleton's structural integrity while ensuring sufficient electrochemical reactivity, avoiding substrate damage or performance degradation due to improper process temperature.

[0072] Example 2

[0073] This embodiment also provides a method for integrated weaving of multi-layer hollow tubular fabrics, including the following steps:

[0074] S1 provides a core layer yarn 100, at least one intermediate layer yarn 300, and a surface layer yarn 400.

[0075] The core layer 100 and the outer layer yarn 400 are core-sheath structure yarns, with the sheath being a melt-bonded material. The intermediate layer yarn 300 includes at least non-thermally fusible high-performance fibers for forming the Z-direction reinforcement structure 200.

[0076] S2 is woven online from the inside out to form a coaxially nested core layer 100 tubular skeleton, at least one intermediate layer tubular skeleton and a surface layer tubular skeleton, to obtain a multi-layer tubular fabric blank.

[0077] S3 performs a first-stage heat treatment on the multilayer tubular fabric blank obtained in step S2 at a temperature equal to or slightly higher than the melting point of the skin material and a pressure of 0.1-0.3 MPa, so that the contact interfaces of each layer are initially melted and bonded to form a tubular fabric skeleton with a stable cavity structure.

[0078] Step S4 involves in-situ nanocomposite treatment of the tubular fabric skeleton. In step S4, the zirconium salt solution has a mass concentration of 50%, the zirconium salt is zirconium nitrate, and the pH value is 8. The ultrasonic treatment frequency is 30 kHz, and the time is 30 min.

[0079] The segmented heating process is as follows: electrolysis begins at 25℃, the temperature is increased to 35℃ at 1.0℃ / min and electrolyzed for 12min, and then the temperature is increased to 45℃ at 1.5℃ / min and electrolyzed for 60min.

[0080] The initial electrolysis voltage was 4V, and the current density was 300mA / cm². The Z-axis reinforcing carbon fiber in the middle layer served as the cathode. The resulting composite tubular fabric exhibited an interlaminar shear strength of 25MPa.

[0081] Example 3

[0082] This embodiment is basically the same as Embodiment 2, except that in step S4, the zirconium salt solution has a mass concentration of 60%, and the zirconium salt is a mixture of zirconium sulfate and zirconium chloride. The ultrasonic treatment frequency is 35 kHz, and the time is 40 min.

[0083] The segmented heating process is as follows: electrolysis begins at 25℃, the temperature is increased to 35℃ at 2.0℃ / min and electrolyzed for 10min, and then the temperature is increased to 45℃ at 1.0℃ / min and electrolyzed for 70min.

[0084] The initial voltage for electrolysis is 5V, and the current density is 400mA / cm².

[0085] The zirconium salt solution also contains 0.5% polyvinylpyrrolidone (PVP) as a dispersant and 0.2% citric acid as a stabilizer.

[0086] The interlaminar shear strength of the resulting composite tubular fabric is 28 MPa.

[0087] Example 4

[0088] This embodiment is basically the same as Embodiment 3, except that in step S4, the zirconium salt solution has a mass concentration of 55%, and the zirconium salt is zirconium chloride. The ultrasonic treatment frequency is 25 kHz, and the time is 35 min.

[0089] The segmented heating process is as follows: electrolysis begins at 25℃, the temperature is increased to 35℃ at 0.8℃ / min and electrolyzed for 15min, and then the temperature is increased to 45℃ at 2.0℃ / min and electrolyzed for 40min.

[0090] The initial electrolysis voltage is 3.5V, and the current density is 250mA / cm².

[0091] The interlaminar shear strength of the resulting composite tubular fabric is 22 MPa.

[0092] Comparative Example 1

[0093] This comparative example employs a method similar to that used in the preparation of traditional composite materials, namely, pre-preparing nano-zirconia powder and then filling it into a pre-formed fabric skeleton through physical impregnation, in order to contrast with the in-situ synthesis method of the present invention.

[0094] The specific steps are as follows:

[0095] First, nano-zirconia powder was prepared using a co-precipitation method: a 0.5 mol / L zirconium nitrate solution and a 1 mol / L ammonia solution were added dropwise to a reactor, with the pH controlled between 9 and 10, to generate zirconium hydroxide precipitate. After washing and drying, the precipitate was calcined at 500℃ for 3 hours to obtain zirconium dioxide powder with an average particle size of approximately 80 nanometers.

[0096] Then, the above-mentioned nano-zirconia powder was mixed with aqueous epoxy resin and dispersant to prepare an impregnation slurry with a solid content of 30%. A tubular fabric skeleton with a multi-layered cavity structure was prepared using the same weaving and preliminary hot-pressing process as in Example 2. Subsequently, the skeleton was placed in a vacuum impregnation tank, and the zirconia slurry was injected. The mixture was held under a vacuum of -0.09 MPa for 30 minutes to remove air from the cavities and promote slurry penetration. After impregnation, the tubular fabric was removed and cured at 120°C for 2 hours to allow the epoxy resin to crosslink and set.

[0097] The performance of the composite tubular fabric was tested, as shown in Table 1 below.

[0098] Table 1 Comparison of the properties of the composite tubular fabrics prepared in Example 2 and the comparative example.

[0099] project Example 2 Comparative Example 1 (Physical Impregnation Method) Functionalization methods In-situ electrolytic synthesis Physical impregnation of pre-made powder Pressure coupling A pressure of 0.3-0.6 MPa is applied simultaneously during electrolysis. Vacuum negative pressure impregnation, without synchronous pressure Z-axis enhancement effect As an electrode, nanoparticles are preferentially generated. Only as a mechanical reinforcement Average particle size of nanoparticles 25nm (controllable) 80nm (pre-fabrication) Interlaminar shear strength 25MPa 8MPa

[0100] As can be seen from Table 1 above, Comparative Example 1 employs a completely different functionalization path. The core difference lies in the fact that the present invention generates nano-zirconia in situ within the fabric skeleton, while Comparative Example 1 physically fills in pre-prepared powder. This fundamental difference leads to a huge performance gap.

[0101] On the other hand, in the method of the present invention, nanoparticles "grow" on the fiber surface under the action of an electric field and form a tight chemical or physical bond with the matrix; while in Comparative Example 1, the particles are only adhered to the fiber by epoxy resin, and the interfacial bonding force is weak.

[0102] Furthermore, the present invention ensures sufficient penetration of the solution and densification of the particles through pressure coupling, while the vacuum impregnation of Comparative Example 1 is unable to completely remove the gas in the tiny cavities, resulting in uneven distribution.

[0103] Therefore, the interlaminar shear strength (25 MPa) of the present invention (Example 2) is more than three times that of Comparative Example 1 (8 MPa).

[0104] Comparative Example 2

[0105] This comparative example employs a method of functionalizing the yarn before weaving, which is intended to be compared with the present invention's method of performing in-situ functionalization after molding.

[0106] The specific steps are as follows:

[0107] First, nano-zirconia powder with an average particle size of 50 nanometers is mixed with thermosetting resin prepolymer and solvent to prepare a functionalized slurry. The core layer 100 yarn (core-sheath structure yarn) is impregnated with this slurry, with the liquid content controlled at 25%, and then pre-dried. Subsequently, the pre-impregnated core layer 100 yarn is integrated with the intermediate layer yarn 300 and surface layer yarn 400 (the same as in Example 2) and undergoes the same gradient hot pressing and functional curing treatment.

[0108] The performance of the composite tubular fabric was tested, as shown in Table 2 below.

[0109] Table 2 compares the properties of the composite tubular fabrics prepared in Example 2 and the comparative example.

[0110] project Example 2 Comparative Example 2 (Yarn Pre-impregnation Method) Functionalization timing After the fabric is formed, it is synthesized in situ within the cavity. Before weaving, the core layer 100 yarn is pre-impregnated. Functional range Distributed throughout the inner cavity, between layers, and on the Z-axis fiber surface Limited to the surface of the core layer 100 yarn Impact of process on functional layers No impact; functionalization will take place after the structure has stabilized. Friction during the weaving process may cause the coating to peel off. Z-axis enhancement effect As an electrode, nanoparticles are preferentially generated. Used solely as a mechanical reinforcement, without functionalization. Interlaminar shear strength 25MPa 12MPa

[0111] The comparison in Table 2 above reveals the significant impact of the timing and scope of functionalization on performance. In this invention (Example 2), in-situ functionalization is performed after the fabric structure is fully stable. This allows the nanoparticles to be uniformly distributed throughout all cavity walls, particularly forming a strong bond with the Z-axis reinforcing fibers that penetrate each layer, thus constructing a three-dimensional functional network. In contrast, the pre-impregnation method in Comparative Example 2 limits functionalization to the core layer 100 yarn, failing to reach the interlayer and Z-axis fibers. More importantly, during the complex weaving process, the yarn undergoes repeated bending and friction, inevitably leading to partial detachment of the pre-impregnation coating, resulting in functional loss and performance instability. Therefore, although Comparative Example 2 exhibits superior performance compared to physical impregnation, its interlayer shear strength of 12 MPa is still significantly lower than the 25 MPa of this invention.

[0112] Comparative Example 3

[0113] This comparative example uses the same in-situ electrolytic synthesis scheme as the present invention, but without applying pressure during the electrolysis process.

[0114] The specific steps are as follows:

[0115] First, a multi-layered tubular fabric skeleton was woven and preliminarily hot-pressed and bonded according to the method of Example 3. Then, a zirconium salt solution that had been ultrasonically treated was injected. Subsequently, the tubular fabric skeleton was placed in an electrolysis device, but without applying a pressure of 0.3-0.6 MPa, and electrolysis was performed only in an open state using the same segmented heating method and electrical parameters (initial voltage 5V, current density 400 mA / cm²) as in Example 3. After electrolysis, the skeleton was removed, cleaned, and dried.

[0116] The performance of the composite tubular fabric was tested, as shown in Table 3 below.

[0117] Table 3 compares the properties of the composite tubular fabrics prepared in Example 3 and the comparative example:

[0118] project Example 3 Comparative Example 3 (No Pressure Coupling) Electrolysis process Electrochemical-thermo-pressure coupling Electrochemical-thermal coupling only Apply pressure Yes (0.3-0.6MPa) no Nanoparticle binding state Embedded into the fiber gaps under pressure, resulting in a tight bond. Loose attachment, weak bond Bubble effect Pressure helps to expel air bubbles Bubbles tend to get trapped, hindering the reaction. Interlaminar shear strength 28MPa 10MPa

[0119] The significant value of "pressure coupling" is clearly evident in Table 3. In this invention (Example 3), a pressure of 0.3-0.6 MPa was applied during electrolysis. This pressure played several crucial roles: First, it "pressed" the in-situ generated nano-zirconia particles into the microscopic gaps on the fiber surface, forming a strong mechanical bond; second, the pressure promoted the penetration of the electrolyte into the deepest part of the fabric, ensuring the uniformity of functionalization; finally, the pressure helped to expel bubbles generated during electrolysis, avoiding functional defects caused by bubble retention. Comparative Example 3 lacked this crucial pressure, resulting in loose bonding and discontinuous distribution of the generated nanoparticles with the matrix, causing its interlaminar shear strength to plummet to 10 MPa, less than half that of this invention (Example 3).

[0120] Comparative Example 4

[0121] This comparative example uses the same in-situ electrolytic synthesis scheme as the present invention, but the tubular fabric skeleton used does not contain Z-direction reinforcing fibers, aiming to verify the dual role of the Z-direction reinforcing structure 200 in functionalization and mechanical reinforcement.

[0122] The specific steps are as follows:

[0123] First, a multi-layered tubular fabric skeleton without Z-axis reinforcing fibers is woven, with other yarns and weaving processes identical to those in Example 2. Then, preliminary hot-press bonding is performed. Subsequently, a zirconium salt solution is injected under exactly the same conditions as in Example 2, followed by electrochemical-hot-press coupling treatment.

[0124] The performance of the composite tubular fabric was tested, as shown in Table 4 below.

[0125] Table 4 compares the properties of the composite tubular fabrics prepared in Example 2 and the comparative example:

[0126] project Example 2 Comparative Example 4 (without Z-axis enhancement) Fabric structure Including Z-direction augmentation network No Z-axis reinforcement, only stacked structure Electrode settings Z-axis carbon fiber as cathode External electrode Nanoparticle distribution Forming a three-dimensional network that runs through all layers Mainly limited to the inner walls of each layer Interlayer connection method Nanoparticles + Z-axis fiber dual connection Mainly relies on nanoparticle connections Interlaminar shear strength 25MPa 14MPa

[0127] The data in Table 4 highlights the central role of the Z-axis reinforced structure 200. In this invention (Example 2), the Z-axis reinforcing fibers not only act as "steel bars" penetrating each layer, significantly improving interlayer delamination resistance, but more importantly, their conductivity makes them ideal built-in electrodes. This allows electrochemical reactions to occur uniformly in three-dimensional space along these "highways," and the generated nano-zirconia firmly "stitches" the layers together, forming a mechanically and functionally integrated reinforcing network. In contrast, Comparative Example 4, lacking Z-axis fibers, relies solely on nanoparticles generated on the inner walls of each layer for interlayer bonding, failing to form an effective three-dimensional penetrating structure. Therefore, although its performance is superior to conventional methods, its interlayer shear strength of 14 MPa is still significantly lower than the 25 MPa of this invention.

[0128] In summary, this invention enables the direct "growth" of nanoparticles within the fabric skeleton, achieving a tight bond with the matrix from the molecular level to the microstructure. In contrast, physical impregnation methods rely solely on resin "adhesion," resulting in weak interfacial bonding and a significant performance gap. Furthermore, functionalization is performed only after the fabric structure is fully stable, avoiding damage to the functional coating during weaving. More importantly, it allows for a leap in functionalization from the "thread" to the "volume," constructing a functional network that runs through the entire three-dimensional structure—an effect unmatched by pre-impregnation methods.

[0129] Furthermore, the synchronously applied pressure is not only a physical means to promote solution penetration and particle densification, but also a core guarantee to ensure that nanoparticles and fiber matrix form a strong mechanical bond and eliminate reaction defects. Without this step, the performance will be greatly reduced. At the same time, the "Z-direction reinforced structure 200" is not only a "steel bar" to improve interlayer strength, but also an "electrode" to guide electrochemical reactions and build a three-dimensional functional network.

[0130] In addition, the present invention provides a multilayer composite hollow tubular fabric prepared by any of the above-mentioned integrated weaving and forming methods for multilayer hollow tubular fabrics, wherein the fabric is internally composite with highly dispersed nano-zirconia with an average particle size of 10-50 nanometers, and the nano-zirconia forms a chemical or physical bond with the Z-direction reinforcing fibers and inner wall of the fabric, and its interlaminar shear strength is not less than 20 MPa.

[0131] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, apparatus, article, or method for integrated weaving of multilayer hollow tubular fabrics that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, apparatus, article, or method for integrated weaving of multilayer hollow tubular fabrics. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, apparatus, article, or method for integrated weaving of multilayer hollow tubular fabrics that includes that element.

[0132] The above description is only a preferred embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural changes made based on the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A method for integrated weaving and forming of multi-layer hollow tubular fabrics, characterized in that, Includes the following steps: S1. A core layer yarn, at least one intermediate layer yarn, and a surface layer yarn are provided; wherein the core layer and surface layer yarns are core-sheath structure yarns, and the sheath is a melt-bonded material; the intermediate layer yarns include at least non-thermally fusible high-performance fibers for forming a Z-axis reinforcement structure. S2. On a special loom, a core tubular skeleton, at least one intermediate tubular skeleton, and a surface tubular skeleton are woven sequentially from the inside out to form a multi-layer tubular fabric blank. S3. The multilayer tubular fabric blank obtained in step S2 is subjected to a first-stage heat treatment at a temperature equal to or slightly higher than the melting point of the skin material and a pressure of 0.1-0.3 MPa, so that the contact interfaces of each layer are initially melted and bonded to form a tubular fabric skeleton with a stable cavity structure. S4. Inject a zirconium salt solution with a pH of 7-9 that has been ultrasonically treated into the inner cavity and / or interlayer cavities of the tubular fabric skeleton obtained in step S3; then place the tubular fabric skeleton in an electrolytic device that combines heating and pressurization functions, and perform programmed gradient heating and electrolytic coupling treatment while applying a pressure of 0.3-0.6 MPa. The coupling process includes: applying an electric field simultaneously during the heating process and controlling the electrolysis temperature using a segmented heating method, so that zirconium ions undergo in-situ reduction-oxidation reaction in the solution to generate highly dispersed nano-zirconia on the inner wall of the cavity and the surface of the Z-direction reinforcing fiber, and using heat and pressure to promote its tight bonding with the fabric matrix, ultimately obtaining a composite tubular fabric that is integrally formed and internally composited with in-situ generated nano-zirconia.

2. The integrated weaving and forming method for multi-layer hollow tubular fabrics according to claim 1, characterized in that, In step S4, the mass concentration of the zirconium salt solution is 45% to 70%, and the zirconium salt is selected from one or more of zirconium sulfate, zirconium nitrate, and zirconium chloride.

3. The integrated weaving and forming method for multi-layer hollow tubular fabrics according to claim 1, characterized in that, In step S4, the segmented heating method includes: starting electrolysis at 25°C, heating to 35°C at a rate of 0.5°C to 2.5°C per minute and maintaining electrolysis for 10 to 15 minutes, and then heating to 45°C at a rate of 0.5°C to 2.5°C per minute and maintaining electrolysis for 30 to 80 minutes.

4. The integrated weaving and forming method for multi-layer hollow tubular fabrics according to claim 1, characterized in that, In step S4, the initial voltage corresponding to the applied electric field is 3 to 5 volts, and the current density is 200 mA / cm² to 500 mA / cm².

5. The integrated weaving and forming method for multi-layer hollow tubular fabrics according to claim 1, characterized in that, In step S4, the ultrasonic treatment of the zirconium salt solution is performed at a frequency of 20 kHz to 40 kHz for a duration of 25 min to 45 min.

6. The integrated weaving and forming method for multi-layer hollow tubular fabrics according to claim 1, characterized in that, In step S1, at least a portion of the Z-axis reinforcing fibers are conductive fibers, which serve as the anode or cathode for electrolysis in step S4, so as to preferentially generate nano-zirconia on the fiber surface.

7. The integrated weaving and forming method for multi-layer hollow tubular fabrics according to claim 7, characterized in that, The conductive fiber is carbon fiber or metal fiber.

8. The integrated weaving and forming method for multi-layer hollow tubular fabrics according to claim 1, characterized in that, In step S4, the average particle size of the in-situ generated nano-zirconia is 10-50 nanometers.

9. The integrated weaving and forming method for multi-layer hollow tubular fabrics according to claim 8, characterized in that, In step S4, a dispersant, stabilizer and complexing agent are also added to the zirconium salt solution to regulate the morphology and dispersibility of nano-zirconia.

10. A multilayer composite hollow tubular fabric prepared by the method according to any one of claims 1-9, characterized in that, The fabric is internally composited with highly dispersed nano-zirconia with an average particle size of 10-50 nanometers, and the nano-zirconia forms a chemical or physical bond with the Z-direction reinforcing fibers and inner wall of the fabric, with an interlaminar shear strength of not less than 20 MPa.

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