Controllable construction method for three-dimensional ordered porous structure on fiber surface

Abstract

The invention provides a controllable construction method of a fiber surface three-dimensional ordered porous structure, and belongs to the technical field of fiber reinforced composite material interface strengthening. The method comprises the following steps: mixing template microspheres and a framework material according to a preset proportion, and performing ultrasonic dispersion to obtain a deposition precursor solution; directionally migrating the microspheres and the framework material to the surface of the fiber through electrophoretic deposition to form a non-tight composite layer; then inducing self-assembly of the microspheres and the framework material through solvent evaporation to construct a three-dimensional ordered composite structure; and finally, selectively etching the structure, and removing the template microspheres to obtain the three-dimensional ordered porous skeleton with the inverse opal structure. According to the method, controllable construction of a three-dimensional porous structure can be achieved on the surface of the fiber with the complex curvature, the interface mechanical interlocking and stress dispersing capacity between the fiber and a resin matrix is remarkably enhanced, the interface strength and the overall mechanical property of the composite material are improved, and the method is suitable for the high-performance engineering field such as light-weight composite materials.

Description

Technical Field

[0001] This invention relates to the field of interface strengthening technology for fiber-reinforced composite materials, specifically to a controllable construction method for a three-dimensional ordered porous structure on the fiber surface. It belongs to the category of surface functionalization and interface strengthening technology for high-performance composite materials and is applicable to applications such as aerospace, automotive, and rail transportation where high requirements are placed on the interface performance of materials. Background Technology

[0002] Fiber-reinforced polymer composites (FRPs) have become important representatives of high-performance structural materials due to their high specific strength, high specific modulus, excellent corrosion resistance, and lightweight properties, and have been widely used in aerospace, rail transportation, automotive industry, and defense equipment. However, the interfacial bonding performance between the fiber and the resin matrix directly determines the mechanical stability and service reliability of the composite material.

[0003] During the service life of composite materials, due to the significant difference in elastic modulus between the fiber and the matrix, especially under shear or multiaxial stress, crack initiation and propagation easily occur at the interface, eventually leading to interfacial failures such as delamination and spalling. This type of failure is particularly severe in stress concentration areas and locations of abrupt curvature changes in components, and has become a key bottleneck restricting the engineering application and high-performance breakthroughs of fiber-reinforced composite materials.

[0004] Existing interface enhancement technologies mainly focus on two aspects: first, chemical modification, such as plasma treatment, oxidant etching, and coupling agent grafting, to introduce polar functional groups on the fiber surface and enhance the chemical bonding with the matrix; second, physical coating methods, such as depositing inorganic particles, resin layers, or rough structures, to improve the interfacial mechanical bonding strength. Although these methods improve interfacial performance to some extent, they still have the following technical limitations:

[0005] 1. Single structural dimension: Most methods form two-dimensional or disordered rough structures, which cannot effectively control the load transfer path, are prone to local stress concentration, and have limited interface enhancement effect;

[0006] 2. Difficulty in thickness control: The thickness of the reinforcing layer is often affected by process fluctuations, making it difficult to accurately control the resin wetting behavior. Too thick or too thin a layer may cause new defects.

[0007] 3. Poor adaptability to curved surfaces: For fiber components with significant curvature or complex morphology, traditional construction techniques are difficult to achieve uniform deposition and stable adhesion, resulting in uneven interface performance.

[0008] In addition, some reinforcement methods may damage the mechanical properties or thermal stability of the original fibers, which is not conducive to their application in high-performance fields.

[0009] Therefore, developing a new interface strengthening method that is suitable for fiber curved substrates, enables controlled construction of three-dimensional structures, and has good material compatibility and reinforcement effect has become an important technical requirement in the field of composite material interface engineering. Summary of the Invention

[0010] To achieve the above technical objectives, this invention proposes a method for constructing three-dimensional ordered structures applicable to different types of fiber substrates. This method integrates the synergistic deposition, self-assembly, and etching strategies of template microspheres and framework materials, exhibiting excellent structural control and material adaptability. The following descriptions, using multiple implementation methods, illustrate the technical paths and characteristics of the resulting three-dimensional porous structures under different material ratios, construction conditions, and etching techniques.

[0011] In one embodiment of the present invention, a method for controllably constructing a three-dimensional ordered porous structure on a fiber surface is provided, comprising the following steps:

[0012] (1) Pretreatment of deposition precursor solution: The template microsphere suspension and the framework material are mixed in a solvent in a predetermined ratio and then ultrasonically dispersed to obtain a uniformly dispersed deposition precursor solution.

[0013] (2) Ordered array construction: The deposition precursor liquid is driven to migrate directionally to the fiber surface by electrophoretic deposition technology to form a non-tight composite layer of microspheres and skeleton material; then self-assembly is induced by solvent evaporation to make the microspheres and skeleton material tightly arranged to form a three-dimensional ordered composite structure.

[0014] (3) Template controllable etching: Selective etching is performed on the three-dimensional ordered composite structure to remove the template microspheres and retain the skeleton material, thereby obtaining a three-dimensional ordered porous skeleton with an inverse opal structure.

[0015] Furthermore, the template microspheres are monodisperse microspheres, including polystyrene microspheres or silica microspheres, and their surface hydrophilicity / hydrophobicity or reactivity can be regulated.

[0016] Furthermore, the framework material is selected from at least one of carbon nanotubes, graphene, MXene, and metal nanoparticles (gold, silver, copper, platinum); the dimensions of the framework material must meet the following requirements:

[0017] (a) It can effectively fill the gaps between microspheres;

[0018] (b) A self-supporting porous structure is formed by interconnecting three-dimensional networks after template etching.

[0019] Preferably, the fiber is carbon fiber, glass fiber, aramid fiber, or silicon carbide fiber, etc.; the matrix of the fiber composite material includes epoxy resin, phenolic resin, polyurethane resin, or polyester resin, etc.

[0020] Furthermore, in the ordered array construction step, the fibers after electrophoretic deposition are induced to self-assemble with the framework material by solvent evaporation under conditions of 40℃~70℃.

[0021] Furthermore, the controllable etching of the template includes two methods: solvent etching or thermal etching.

[0022] In solvent etching, polystyrene microspheres are etched with tetrahydrofuran or toluene, while silica microspheres are etched with hydrofluoric acid solution.

[0023] Pyrolytic etching involves high-temperature decomposition of polystyrene microspheres at 250℃~500℃.

[0024] Optionally, the mixing ratio of the template microspheres to the skeleton material is 1:1 to 1:2 to achieve a balance between structural uniformity and support.

[0025] Furthermore, the interfacial shear strength of the obtained three-dimensional ordered porous structure is increased by more than 60% compared with that of the unmodified fiber, and the tensile strength of the monofilament is increased by more than 10%.

[0026] In one embodiment of the present invention, a fiber-reinforced composite material is provided, wherein the fiber surface is constructed with a three-dimensional ordered porous structure by any of the methods described above.

[0027] Furthermore, the fiber-reinforced composite material is suitable for applications with high requirements for interface performance, such as aerospace components or lightweight automotive structural parts.

[0028] Based on the above technical solution, the controllable construction method of three-dimensional ordered porous structure on fiber surface of the present invention achieves significant improvement in interface mechanical properties by introducing a porous skeleton with controlled spatial structure on fiber surface, and solves the technical bottlenecks of insufficient structural dimension, uncontrollable thickness and poor adaptability to curved surfaces in the existing two-dimensional roughening method.

[0029] This invention utilizes the synergistic effect of template microspheres and framework materials, employing electrophoretic deposition to achieve ordered directional migration, and then combining this with a solvent evaporation-induced self-assembly process to construct a highly ordered and dense microsphere-framework composite system. Finally, the template is precisely removed through etching to achieve the formation of a three-dimensional porous framework. This method has the following advantages:

[0030] First, in terms of the construction mechanism, this invention fully combines electric field driving and self-assembly effect to realize the deposition of complex three-dimensional structures on the surface of curved fiber substrate, which greatly improves the distribution uniformity and construction controllability of micro and nano structures.

[0031] Secondly, in terms of material selection, this invention uses polystyrene or silica microspheres with monodispersity and strong interface control capabilities as templates, and combines them with high-strength, high-specific-surface-area framework materials (such as carbon nanotubes, graphene, MXene, etc.) to effectively achieve the support and connection of the microstructure, which helps to improve structural integrity and interface force transmission efficiency.

[0032] Furthermore, in terms of etching strategies, this invention provides two optional solutions for different template materials: chemical solvent etching and thermal etching. This ensures both the stability of the selective removal process and the complete preservation of the framework material and the formation of the porous network.

[0033] Furthermore, the process route proposed in this invention can be flexibly adapted to different types of fibers and matrix materials, including fiber systems such as carbon fiber, glass fiber, and aramid fiber, as well as various resin systems such as epoxy resin and phenolic resin, and has good universality and scalability.

[0034] Experimental results show that, compared with untreated fibers, the three-dimensional ordered porous structure coated fibers constructed using the method of this invention exhibit a more than 60% increase in interfacial shear strength and a more than 10% increase in monofilament tensile strength, demonstrating a significant interfacial reinforcement effect. This reinforcement mainly stems from the combined effect of mechanical interlocking reinforcement and stress dispersion brought about by the three-dimensional porous coating, effectively suppressing the initiation and propagation of interfacial cracks.

[0035] The construction method provided by this invention is not only applicable to the surface reinforcement treatment of traditional straight fibers, but also particularly applicable to the surface of fiber components with significant curvature or complex geometry, overcoming the problem that traditional methods are difficult to deposit uniformly in complex interface scenarios.

[0036] In summary, the controllable construction method for three-dimensional ordered porous structures on fiber surfaces provided by this invention has significant advantages in realizing the functionalization of fiber surface structures, enhancing the interfacial bonding strength and service stability of composite materials. It is particularly suitable for the preparation and engineering application of high-performance fiber-reinforced composite materials such as aerospace structural components and lightweight automotive components, and has broad prospects for industrial application. Attached Figure Description

[0037] Figure 1 This is a schematic diagram illustrating the principle of a controllable construction method for a three-dimensional ordered porous structure on a fiber surface as described in this invention; the diagram shows the basic process of forming a three-dimensional ordered porous structure on a fiber surface through electrophoretic deposition and self-assembly.

[0038] In the figure: 1-Electrode plate, 2-Ordered template microspheres, 3-Framework material, 4-Deposition substrate (fiber);

[0039] Figure 2This is a front view of the three-dimensional ordered porous structure coating fiber in the embodiment, showing the ordered arrangement of microspheres and skeleton material on the main surface of the fiber;

[0040] Figure 3 This is a side view of the three-dimensional ordered porous structure coated fiber in the embodiment, showing the construction morphology and layer thickness characteristics of the porous skeleton structure in the fiber surface direction;

[0041] Figure 4 This is a scanning electron microscope (SEM) image of the three-dimensional ordered porous structure coated fiber, reflecting the regular porous network structure formed on the fiber surface by the skeleton material after template etching, verifying the effectiveness of the construction method and the structural integrity. Detailed Implementation

[0042] To better understand the present invention, the following description, in conjunction with the accompanying drawings, further illustrates the controllable construction method of the three-dimensional ordered porous structure on the fiber surface described in the present invention, but does not limit the scope of protection of the present invention.

[0043] Example 1: A method for constructing three-dimensional ordered porous structures based on polystyrene microspheres and carbon nanotubes

[0044] This embodiment aims to demonstrate a complete process for constructing a three-dimensional ordered porous structure coating using polystyrene microspheres and carbon nanotubes, which is suitable for functionalizing the surface structure of carbon fibers and improving the interfacial mechanical properties.

[0045] (1) Pretreatment of sedimentation precursor solution

[0046] like Figure 1 As shown, monodisperse polystyrene (PS) microspheres with a particle size of 500 nm were selected as the template material, and carbon nanotubes (CNTs) as the framework reinforcement material. The PS microsphere suspension and CNT dispersion were added to N,N-dimethylformamide (DMF) as a solvent at a mass ratio of 1:1, and then ultrasonically dispersed in an ultrasonic processor at a power of 150 W for 15 minutes to obtain a stable and homogeneous deposition precursor solution. This liquid exhibits good fluidity and dispersion stability, facilitating subsequent electrophoretic deposition.

[0047] (2) Ordered array construction steps

[0048] Cut a single carbon fiber bundle into a 5cm length and fix it to... Figure 1 In the electrode system shown, the fiber is located at the cathode, and the electrode plate spacing is set to 2 cm. A constant voltage of 20V is applied through a DC regulated power supply, and the deposition time is 90 seconds. During the electrophoretic deposition process, PS microspheres and CNT particles migrate directionally to the fiber surface along the electric field lines under the influence of the electric field, gradually depositing to form the initial composite layer.

[0049] After electrophoretic deposition, the fiber sample is slowly extracted from the solution to avoid disturbing the coating structure. The sample is then placed in an oven and subjected to solvent evaporation at 50°C for 30 minutes. This process drives the self-assembly of the microspheres and framework material on the surface, with the microspheres gradually arranging into a hexagonal close-packed structure, and CNTs filling the gaps between the microspheres. Figure 2 , Figure 3 As shown.

[0050] (3) Template etching steps

[0051] To remove the PS microsphere template, the dried sample was immersed in tetrahydrofuran (THF) for 10 minutes in a fume hood for dissolution and etching. It was then rinsed three times with anhydrous ethanol to remove residual solvent. After drying, a highly ordered three-dimensional porous network structure of CNTs was observed on the fiber surface, exhibiting typical inverse opal arrangement characteristics, such as... Figure 4 As shown.

[0052] (4) Structural and performance analysis

[0053] The microstructure of the obtained three-dimensional ordered porous coating was observed using scanning electron microscopy (SEM), such as... Figure 4 The results showed that the pores were arranged in an orderly manner, the skeleton structure was intact, and the CNTs formed an interconnected network without any obvious collapse or breakage.

[0054] SEM images show that during the drying process, the microsphere structure changes from an initial loosely packed state to a regular and ordered arrangement, forming a significant gap shrinkage phenomenon. That is, the gap d2 of the microspheres after self-assembly is significantly smaller than the initial gap d1, indicating that the solvent-induced self-assembly process is effective and the structure is compact.

[0055] Regarding mechanical properties, single-filament tensile tests and interfacial shear strength (IFSS) tests were conducted on carbon fiber samples before and after treatment. The results are as follows:

[0056] The average tensile strength of the monofilament increased from the original 3500MPa to 3850MPa, an increase of approximately 10%.

[0057] IFSS increased significantly from 28 MPa to 45 MPa, an improvement of over 60%.

[0058] The results demonstrate that the three-dimensional porous structure prepared by the method of the present invention not only does not weaken the strength of the fiber body, but also enhances the interfacial load transfer capability and mechanical interlocking effect through the microstructure.

[0059] The construction method provided in this embodiment has mild process conditions and controllable operation steps. It is suitable for constructing porous structures on complex curved fiber surfaces, has good process compatibility and interface enhancement effect, and provides reliable technical support for the application of composite materials in high-performance fields.

[0060] Example 2: A method for constructing three-dimensional ordered porous structures using toluene as an etchant

[0061] Based on Example 1, this embodiment uses toluene instead of tetrahydrofuran as the etching solvent for polystyrene microspheres to verify the influence of different solvent systems on template removal behavior and the final porous framework morphology and performance.

[0062] (1) Pretreatment of sedimentation precursor solution

[0063] The steps are the same as in Example 1:

[0064] 500 nm polystyrene (PS) microspheres and carbon nanotubes (CNTs) were mixed in an N,N-dimethylformamide (DMF) solution at a mass ratio of 1:1 and ultrasonically dispersed for 15 minutes to form a deposition precursor solution.

[0065] (2) Ordered array construction steps

[0066] In electrophoretic deposition systems (see...) Figure 1 The carbon fiber 4 was fixed in front of the electrode plate 1, the voltage was set to 20V, and the deposition time was 90 seconds.

[0067] The sample was then removed and heat-dried at 50°C for 30 minutes to promote the self-assembly of microspheres and CNTs to form a dense and ordered structural layer, such as Figure 2 and Figure 3 As shown.

[0068] (3) Template etching steps

[0069] The dried fiber sample was immersed in a toluene solution for template etching for 15 minutes. Toluene and PS microspheres have good solubility and compatibility, and the microspheres were observed to gradually disintegrate and fall off during the etching process.

[0070] To ensure complete template removal, the sample was replaced with fresh toluene twice, and after etching, it was thoroughly cleaned three times with anhydrous ethanol, then dried in a vacuum oven at 60°C for 2 hours. The template was essentially eliminated from the resulting sample, preserving a stable three-dimensional carbon nanotube network framework.

[0071] (4) Structural characterization and comparative analysis

[0072] like Figure 4 As shown, the morphology of the etched fiber surface was analyzed using scanning electron microscopy (SEM), and the results show:

[0073] The microsphere template has been completely removed, and the skeleton material is arranged to form interconnected pore channels;

[0074] The surface of the skeleton was relatively clean, and no obvious solvent residue or microsphere fragments were observed.

[0075] Compared to the structure obtained by etching with tetrahydrofuran in Example 1, the pore edges obtained by etching with toluene are slightly softer, and the etching process causes less disturbance to the carbon nanotube structure of the pore wall, forming a smoother porous interface.

[0076] (5) Performance Testing and Comparison

[0077] The fibers constructed in this embodiment were subjected to monofilament tensile tests and interfacial shear strength tests, and the results are as follows:

[0078] The tensile strength of the monofilament was increased to approximately 3840 MPa, which is about 9.7% higher than that of the unmodified fiber;

[0079] The interfacial shear strength reached approximately 43 MPa, an increase of about 54% compared to the original value.

[0080] Comparing the performance data of Example 1 and Example 2, both showed significant enhancement, indicating that toluene as an etchant has good etching efficiency at room temperature and a mild impact on structural morphology, making it suitable for large-scale processing.

[0081] This embodiment illustrates the feasibility of using toluene as an etchant for PS templates and further verifies the solvent type compatibility of the proposed three-dimensional ordered porous structure construction strategy. This method maintains process simplicity and film structure integrity, making it suitable for interface functionalization scenarios requiring high precision in pore morphology.

[0082] Example 3: Constructing an enhanced three-dimensional ordered porous structure by increasing the proportion of skeleton material (1:2)

[0083] This embodiment, based on Example 2, adjusts the mass ratio of template microspheres to carbon nanotubes from 1:1 to 1:2 to explore the effect of increasing the proportion of framework material on the stability and mechanical properties of the porous structure. Other process conditions remain the same.

[0084] (1) Pretreatment of sedimentation precursor solution

[0085] Polystyrene (PS) microspheres with a particle size of 500 nm and carbon nanotubes (CNTs) were dispersed in N,N-dimethylformamide (DMF) at a mass ratio of 1:2. To enhance the dispersibility of the carbon nanotubes, sodium dodecyl sulfonate (SDS) (0.1 wt%) was used as a dispersant beforehand. After ultrasonic treatment for 20 minutes, a deposition precursor solution was obtained. Observation showed that the liquid was uniformly grayish-black and showed no obvious agglomeration.

[0086] (2) Ordered array construction

[0087] like Figure 1 As shown, using an electrophoretic deposition system, a single carbon fiber was fixed in an electrode fixture, and the voltage was set to 20V for 90 seconds. Due to the increased proportion of the framework material, the migration rate of CNTs was slightly faster than that of microspheres during electrophoresis, and the carbon nanotube filling degree in the initial composite layer was significantly enhanced.

[0088] After drying in a 50°C hot zone for 30 minutes, self-assembly and rearrangement are induced within the composite layer, forming a denser microsphere-skeleton composite structure. For example... Figure 2 and Figure 3 As shown, the carbon nanotubes in the pores of the self-assembled stacked layer are fully filled, and the density and connectivity of the framework are improved.

[0089] (3) Template etching process

[0090] The PS template was etched using a toluene solution, with the etching time extended to 20 minutes. Due to the high skeleton ratio and narrow pore paths, the etching rate was slightly reduced. To ensure complete template removal, a two-stage etching process was employed: fresh toluene was replaced every 10 minutes, with ultrasonic assistance for 2 minutes to improve penetration efficiency. Finally, the template was cleaned with anhydrous ethanol and vacuum-dried at 60°C.

[0091] (4) Structural observation and comparison

[0092] Figure 4 The SEM images shown indicate that the porous structure is regular, with significant thickening of carbon nanotubes at the pore walls, enhancing the strength of the three-dimensional network support. Compared to Examples 1 and 2, a bridging interconnect structure is formed between the framework materials, exhibiting better structural integrity and resistance to compressive collapse.

[0093] Furthermore, due to the increased proportion of carbon nanotubes, an "enveloping" structure is formed between the original positions of the microspheres, effectively fixing the cavity morphology and enhancing the stability of the three-dimensional structure.

[0094] SEM images show that during the drying process, the microsphere structure changes from an initial loosely packed state to a regular and ordered arrangement, forming a significant gap shrinkage phenomenon. That is, the gap d2 of the microspheres after self-assembly is significantly smaller than the initial gap d1, indicating that the solvent-induced self-assembly process is effective and the structure is compact.

[0095] (5) Mechanical property analysis

[0096] The tensile strength of the carbon fiber after treatment in this embodiment is about 3880 MPa, which is about 11% higher than that of the original fiber; the interfacial shear strength (IFSS) reaches 47 MPa, which is nearly 68% higher.

[0097] Test results show that moderately increasing the proportion of skeleton material will not hinder template etching, but will instead help to build a stronger self-supporting skeleton, thereby improving the structural load-bearing and energy dissipation capacity without sacrificing the interface porosity.

[0098] This embodiment verifies the important role of "increasing the proportion of skeleton material" in constructing stable three-dimensional networks, and is particularly suitable for composite material interface treatment scenarios where high mechanical reinforcement effects are required. Its construction strategy has promising prospects for widespread application in fields such as aerospace structural materials and curved composite components.

[0099] Example 4: Construction method of three-dimensional ordered porous structure by etching with tetrahydrofuran under high skeleton material ratio. Based on Example 3, this example replaces toluene with tetrahydrofuran (THF) as the template etching solvent to compare the etching behavior and construction effect of different solvent systems under the condition of high skeleton material ratio (1:2), and further verify the process adaptability and structure control capability of the method of the present invention.

[0100] (1) Pretreatment of sedimentation precursor solution

[0101] Monodisperse polystyrene (PS) microspheres (500 nm in diameter) and carbon nanotubes (CNTs) were dispersed in N,N-dimethylformamide (DMF) at a mass ratio of 1:2. 0.1 wt% SDS was added as an additive, and the mixture was ultrasonically dispersed for 20 minutes to form a stable deposition precursor solution. Increased CNT content resulted in a dark gray suspension with good rheological properties, making it suitable for electrophoretic deposition.

[0102] (2) Ordered array construction

[0103] The carbon fiber monofilament sample was fixed in such a way as... Figure 1 In the electrode plate (1) structure shown, the electric field strength is set to 10V / cm and the deposition time is 90 seconds. During electrophoresis, the negatively charged PS microspheres migrate synchronously with CNTs and are deposited on the fiber surface (4), forming a mixed non-compact composite layer.

[0104] After drying in a 50°C hot zone for 30 minutes, the self-assembly process of the microspheres is completed. Carbon nanotubes fill the gaps between the microspheres and locally wrap around the framework, such as... Figure 2 and Figure 3 As shown, observations revealed that CNTs form a micro-bundle structure in the microsphere sinking area, which is beneficial for the stability of the framework after etching.

[0105] (3) Template etching steps

[0106] This embodiment uses tetrahydrofuran (THF) as the etching solvent, which has a stronger polystyrene dissolving ability and is particularly suitable for rapid etching of denser deposits.

[0107] Immerse the dried sample in fresh THF solution (room temperature) for 10 minutes. Then, use ultrasound-assisted treatment for 2 minutes to ensure complete dissolution of the deep microspheres. Replace with fresh THF solution and etch for 5 minutes. Immediately after etching, rinse three times with anhydrous ethanol and vacuum dry at 60°C for 2 hours.

[0108] Due to the high proportion of skeleton material, THF did not cause the channel to collapse during the etching process, and the CNT skeleton firmly supported the cavity structure.

[0109] (4) Structural and morphological analysis

[0110] like Figure 4 As shown, the etched coating structure exhibits uniform pores, with pore walls supported by multilayered cross-linked carbon nanotubes, displaying a typical inverse opal three-dimensional arrangement structure. Compared to the toluene-etched sample, the pore edges in this embodiment are clearer, the interface contours are sharper, and the framework connectivity is better.

[0111] High-resolution SEM observations showed that THF etching rate was slightly faster than toluene, allowing it to penetrate the microspheres and CNT composite layer more quickly, with less dissolution residue, making it more suitable for dense framework areas.

[0112] (5) Mechanical performance evaluation

[0113] Monofilament tensile strength: increased to approximately 3900 MPa (+11.4%).

[0114] Interfacial shear strength (IFSS): 48 MPa (+70%)

[0115] The data above show that a high-ratio CNT+THF etching combination can balance the strength of the framework and the stability of the channel structure, significantly improving the mechanical properties of the interface.

[0116] This embodiment demonstrates that, even with a framework material ratio increased to 1:2, template etching using tetrahydrofuran can still yield a complete, clear, and highly interconnected three-dimensional ordered porous framework structure. The etching efficiency is higher, and the structural morphology is superior to that obtained using toluene etching, making it particularly suitable for engineering applications requiring high precision in pore diameter profiles.

[0117] Example 5: A method for constructing a three-dimensional ordered porous structure using MXene as a framework material

[0118] This embodiment aims to explore the feasibility and reinforcing effect of constructing a three-dimensional ordered porous structure on the fiber surface by replacing carbon nanotubes with MXene two-dimensional nanosheets as the framework material. MXene has excellent conductivity, layered structure, and surface functional group activity, giving it unique advantages in constructing high-strength interfacial framework layers.

[0119] (1) Pretreatment of sedimentation precursor solution

[0120] Monodisperse polystyrene (PS) microspheres with a particle size of 500 nm were selected as the template material, and Ti3C2Tx type MXene sheets were used as the framework material, mixed at a mass ratio of 1:1. To obtain a stable precursor dispersion, the PS microspheres and MXene were pre-dispersed separately in N,N-dimethylformamide (DMF), followed by combined ultrasonic treatment for 30 minutes. To improve the exfoliation and dispersibility of MXene in polar solutions, 0.1 wt% triethanolamine (TEA) was added as an auxiliary stabilizer.

[0121] Observations revealed that the dispersion exhibited a silvery-gray metallic luster, indicating that the MXene nanosheets had formed a uniform suspension and possessed good deposition adaptability.

[0122] (2) Ordered array construction steps

[0123] like Figure 1 As shown, a single carbon fiber bundle (4) was fixed in front of the electrode plate (1), and the voltage was set to 15V, the electric field spacing to 2cm, and the electrophoretic deposition time to 120 seconds. During electrophoresis, the charged PS microspheres and MXene sheets migrated together and deposited on the fiber surface to form a preliminary composite layer.

[0124] Because MXene has a sheet-like structure, it exhibits a "layered insertion" morphology within the gaps between microspheres, effectively constructing a spatial support network. After deposition, the fiber sample is slowly extracted and placed in a 50°C thermal field for 30 minutes to induce directional stacking of microspheres and self-assembly locking between MXene sheets, forming a dense three-dimensional composite structure. Figure 2 , Figure 3 ).

[0125] (3) Template etching steps

[0126] Toluene was used as the solvent during the etching stage, with an immersion time of 15 minutes. Due to the relatively thin structure and high surface activity of MXene, the risk of severe swelling or interface peeling must be controlled during the etching process; therefore, ultrasonic assistance was not used.

[0127] After etching, the material was rinsed three times with anhydrous ethanol and then vacuum dried at 60°C for 2 hours to obtain a stable three-dimensional porous framework structure.

[0128] (4) Structural characterization

[0129] like Figure 4 As shown, SEM observations revealed that the microsphere template was completely etched, and the MXene sheets were tightly stacked between the pore walls, forming a "tile-like" interconnected framework. Due to the hydrogen bonding / van der Waals forces between the MXene sheets, its support strength is higher than that of one-dimensional materials of the same thickness.

[0130] The structure has the following characteristics:

[0131] The porous structure is regular and the pores are complete;

[0132] High surface roughness of the hole wall is beneficial to interfacial mechanical engagement;

[0133] The skeleton layers are oriented along the fiber axis, which facilitates the dispersion and transfer of shear loads.

[0134] (5) Performance Testing and Analysis

[0135] The tensile strength of the monofilament is 3860 MPa, which is about 10% higher than that of the original fiber;

[0136] The interfacial shear strength (IFSS) reached 46 MPa, an improvement of approximately 64%.

[0137] Test results show that although MXene is a two-dimensional sheet structure, it can form a stable three-dimensional skeleton network under the combined action of electrophoretic deposition, self-assembly, and template etching, which has a significant effect on enhancing the bonding ability of the fiber / resin interface.

[0138] This embodiment verifies the feasibility of MXene as a framework material. Its layered structure adheres tightly to the fiber surface, creating a strong mechanical interlocking effect and an interfacial conductive layer. This approach is particularly suitable for applications requiring high thermal conductivity and high electrical conductivity interface reinforcement, such as composite electromagnetic shielding layers and thermal interface materials.

[0139] Example 6: A method for constructing high-strength three-dimensional ordered porous structures by increasing the proportion of MXene framework material (1:2).

[0140] Based on Example 5, this embodiment increases the mass ratio of template microspheres to MXene from 1:1 to 1:2 to further enhance the continuity and support capacity of the residual skeleton after etching, and construct a high-strength, multifunctional three-dimensional ordered porous structure.

[0141] (1) Pretreatment of sedimentation precursor solution

[0142] Monodisperse polystyrene (PS) microspheres (500 nm in diameter) and Ti3C2Tx type MXene sheets were mixed at a mass ratio of 1:2. To inhibit the formation of sheet agglomerates from high-concentration MXene in the solvent, 0.2 wt% polyvinylpyrrolidone (PVP) was used as a surface stabilizer, mixed in N,N-dimethylformamide (DMF) solvent, and ultrasonically treated for 40 minutes to obtain a gray-black, highly fluid deposition precursor solution.

[0143] High MXene content enhances the conductivity and viscosity of the precursor solution, resulting in more stable deposition behavior.

[0144] (2) Ordered array construction steps

[0145] according to Figure 1 The apparatus shown has a 5cm long carbon fiber bundle fixed to an electrode clamp, with a voltage set to 15V and an electrophoresis time of 120 seconds. Under the influence of the electric field, PS microspheres and MXene sheets migrate and deposit together on the fiber surface.

[0146] Compared to Example 5, due to the higher proportion of MXene, the microspheres are "surrounded" in the deposition layer, and a large number of MXene sheets form an overlapping-nested skeleton substrate around the microspheres, which is beneficial for the formation of a stronger self-supporting network after subsequent etching.

[0147] After deposition, the sample was heat-dried at 50°C for 30 minutes, inducing the PS microspheres to align into a hexagonal close-packed structure. Simultaneously, MXene sheets filled the gaps between the microspheres and stacked and bonded together, constructing a structure resembling... Figure 2 , Figure 3 The three-dimensional composite layer shown.

[0148] (3) Template etching steps

[0149] Tetrahydrofuran (THF) was used as the etching solvent. The etching process involved immersion at room temperature for 20 minutes, followed by replacement with fresh THF solution. Due to the high proportion of MXene, the pore wall thickness formed during etching was significantly increased, effectively resisting the disturbance of THF to the structural edges.

[0150] After etching, the material was rinsed with anhydrous ethanol and vacuum dried at 60°C for 2 hours to obtain a complete three-dimensional porous skeleton.

[0151] (4) Structural characterization and microscopic analysis

[0152] like Figure 4 As shown, the SEM image displays the obtained skeleton structure:

[0153] The pores are uniform in size and have clear boundaries; the microsphere template has been completely removed.

[0154] MXene sheets are stacked along the pore wall direction, exhibiting a clear "layer-by-layer coating" characteristic;

[0155] The porous network has high continuity and multiple support paths, exhibiting a typical honeycomb-like inverse opal structure.

[0156] Image comparison revealed that, compared to Example 5, this example has more MXene layers, a thicker structure, and local bridging-winding structures, exhibiting higher resistance to deformation and toughness.

[0157] (5) Mechanical property testing

[0158] The tensile strength of the monofilament is 3920 MPa, an increase of approximately 11.8%.

[0159] The interfacial shear strength (IFSS) reached 49 MPa, an improvement of approximately 75%.

[0160] Furthermore, the sample exhibited good repeatability in three interfacial shear cycle tests, indicating that the three-dimensional network structure can effectively buffer load impacts and suppress crack propagation.

[0161] This embodiment demonstrates that appropriately increasing the proportion of MXene framework material not only helps improve pore wall strength and structural integrity, but also enables the construction of a highly dense, three-dimensional reinforced coating with multiple conductive / thermal channels. This strategy is particularly suitable for high-end composite material applications that require a combination of interfacial mechanical strength and multiple physical functions (such as conductivity and thermal stability), such as aerospace structures, electronic packaging, and thermal interface materials.

[0162] Example 7: A method for constructing a three-dimensional ordered porous structure using silica microspheres and MXene

[0163] This embodiment explores the process pathway and interface enhancement effect of constructing a highly thermally stable three-dimensional ordered porous structure by replacing the template material with inorganic microspheres (silica) and combining it with MXene framework material. This construction method is suitable for functional interfacial layers of composite materials requiring high-temperature treatment or solvent resistance.

[0164] (1) Pretreatment of sedimentation precursor solution

[0165] Monodisperse silica (SiO2) microspheres with a diameter of 500 nm and Ti3C2Tx type MXene nanosheets were selected as raw materials and mixed at a mass ratio of 1:1. The two were dispersed separately in ethanol and deionized water, then combined and ultrasonically treated for 30 minutes with 0.1 wt% PVP stabilizer to obtain a homogeneous deposition precursor solution. The resulting liquid was light gray, exhibited good stability, and showed no obvious agglomeration or sedimentation.

[0166] Since SiO2 is an inorganic hard sphere, its surface has a large number of hydroxyl groups, which can form a certain degree of hydrogen bond adsorption with MXene surface groups (-OH, -F), thereby improving the bonding strength of the composite layer.

[0167] (2) Ordered array construction steps

[0168] like Figure 1 As shown, carbon fiber bundles were fixed at the cathode using an electrophoretic deposition apparatus, with a platinum sheet as the anode and an electrode spacing of 2 cm. A voltage of 15 V was applied, and the deposition time was 90 seconds. During electrophoresis, SiO2 microspheres and MXene were co-deposited onto the carbon fiber surface under the influence of an electric field.

[0169] After deposition, the sample was dried in a 60°C thermal field for 30 minutes to promote the arrangement of microspheres into an approximately hexagonal ordered structure, while simultaneously driving the nesting and stacking of MXene in the interstices, such as... Figure 2 and Figure 3 As shown, a light white, matte deposit layer forms on the sample surface after drying.

[0170] (3) Template etching steps

[0171] Due to the high chemical stability of silica microspheres, this embodiment uses hydrofluoric acid (HF) solution for etching. The specific steps are as follows:

[0172] The sample was immersed in a 5 wt% HF solution and reacted for 10 minutes.

[0173] The procedure was performed inside a fume hood while wearing full protective gear.

[0174] Immediately after etching, rinse three times with plenty of deionized water to thoroughly remove any HF residue.

[0175] Dry in a vacuum drying oven at 60℃ for 2 hours.

[0176] After etching, the SiO2 template is completely dissolved and removed, preserving the MXene three-dimensional interconnect skeleton structure.

[0177] (4) Structural characterization and property observation

[0178] like Figure 4 As shown, scanning electron microscopy (SEM) reveals that the etched fiber surface forms a complete, dense, three-dimensional ordered porous structure with regular pore sizes and clear edges. The MXene framework layers are tightly arranged and stacked alternately along the pore walls, forming a strong support network.

[0179] Compared to organic template etching structures, SiO2 templates have higher rigidity and better dimensional stability during deposition, resulting in a more regular microsphere stack and higher fidelity in pore arrangement after etching.

[0180] (5) Performance test results

[0181] The tensile strength of the monofilament reaches 3880MPa, an increase of approximately 10%;

[0182] The interfacial shear strength (IFSS) reached 47 MPa, which is about 68% higher than that of untreated fibers.

[0183] Furthermore, the SEM image structure of this sample remained largely intact after heat treatment at 150℃, indicating that the porous structure obtained by this method has excellent thermal stability and solvent resistance, and is suitable for interface treatment of high-temperature resin systems (such as BMI and PEEK).

[0184] This embodiment demonstrates that using silica microspheres as a template material, combined with an MXene framework, can construct a well-structured, thermally stable, three-dimensionally ordered porous coating, which is particularly suitable for the interface strengthening requirements of high-temperature heat-resistant composite materials in aerospace applications. Its controllable etching process and thorough template removal are key extension paths of the technical solution of this invention.

[0185] Example 8: A method for constructing a three-dimensional ordered porous structure using graphene and silica microspheres

[0186] This embodiment aims to explore the feasibility of using two-dimensional graphene sheets as a framework material, combined with inorganic template silica microspheres (SiO2), to construct a three-dimensional ordered porous structure on the surface of carbon fibers. Graphene has unique advantages in composite material interface reinforcement and thermal / electrical function regulation due to its ultra-high specific surface area, excellent thermal and electrical conductivity, and sheet flexibility.

[0187] (1) Pretreatment of sedimentation precursor solution

[0188] 500nm diameter, monodisperse silica (SiO2) microspheres were selected as templates, and graphene nanosheets (single to three layers, lateral dimensions of about 1-3μm) were selected as framework materials. The two were configured in a mass ratio of 1:1.

[0189] The graphene sheets were dispersed in a mixture of deionized water and a small amount of ethanol (volume ratio 4:1), and 0.2 wt% gelatin was added as an auxiliary dispersant. After ultrasonic treatment for 40 minutes, SiO2 microsphere suspension was added, and the mixture was ultrasonicated again for 10 minutes to finally obtain a uniformly dispersed and stable deposition precursor solution.

[0190] The resulting liquid was in a dark gray-black suspension state, with no visible agglomeration or sedimentation.

[0191] (2) Ordered array construction steps

[0192] like Figure 1 As shown, a 5cm long carbon fiber monofilament is fixed to the cathode side of the electrophoretic deposition apparatus, and the anode is a platinum sheet. The electrode spacing is 2cm, the deposition voltage is 15V, and the electrophoresis time is 90 seconds.

[0193] During the deposition process, SiO2 microspheres and graphene migrate synergistically to the fiber surface under the influence of an electric field. Because graphene is a flexible sheet with a high specific surface area, its deposition mode is mostly characterized by "coating-winding-overlapping", forming a multi-layered coating structure in the gaps between microspheres and constructing an early support network.

[0194] After deposition, the sample was dried in a 50°C oven for 30 minutes to complete the microsphere self-assembly and framework bonding process. Figure 2 and Figure 3As shown, graphene forms a continuous "bridge-like" sheet distribution at the junction of microspheres, indicating that it has good interconnect support capabilities after etching.

[0195] (3) Template etching steps

[0196] The etching process is the same as in Example 7, using a 5wt% hydrofluoric acid (HF) aqueous solution to etch the SiO2 template:

[0197] Soak for 15 minutes, stirring gently with a magnetic stirrer;

[0198] Rinse thoroughly with plenty of deionized water immediately after completion;

[0199] A stable three-dimensional ordered porous framework was obtained by ethanol replacement and vacuum drying at 60°C for 2 hours.

[0200] (4) Structural observation and microscopic analysis

[0201] like Figure 4 As shown, after etching, the graphene framework forms a highly ordered, interconnected, and continuous porous network on the fiber surface:

[0202] The pore walls are smooth, the pore size is uniform, and the graphene sheets are stacked evenly without collapse.

[0203] The skeleton layer has a "bending-overlapping-winding" shape, which enhances the structure's toughness and impact resistance;

[0204] The skeleton thickness is well controlled, with no obvious lamellar warping or peeling.

[0205] Thanks to the extensibility of graphene sheets, the cavity structure has soft boundaries and high interface adhesion, which is conducive to forming a continuous transition layer with the substrate.

[0206] (5) Performance testing and functional performance

[0207] The tensile strength of the monofilament is 3890 MPa, which is about 11% higher than that of the unmodified filament.

[0208] The interfacial shear strength (IFSS) is 46 MPa, an improvement of approximately 64%.

[0209] Thermal conductivity increased by 12%, and volume resistivity decreased by approximately 30%.

[0210] This demonstrates that the porous framework layer constructed from graphene not only provides good mechanical support, but also possesses excellent thermal conductivity and electrical conductivity continuity, making it widely applicable to thermally / electrically conductive interface composite material systems.

[0211] This embodiment demonstrates that graphene, as a framework material, can stably construct a three-dimensional ordered porous structure through a combination of electrophoretic deposition and self-assembly, achieving a multifunctional interface layer that integrates mechanical enhancement and thermal / electrical conductivity. This method is particularly suitable for composite material applications requiring interface heat dissipation, resistance to electric shock, or electromagnetic shielding, such as power battery structural housings, conductive composite connectors, and thermal control layers for aircraft bodies.

[0212] Example 9: A method for constructing highly dense three-dimensional ordered porous structures by increasing the graphene ratio (1:2).

[0213] This embodiment is based on Embodiment 8, and further increases the proportion of graphene framework material to twice that of template microspheres (mass ratio 1:2). The purpose is to form a denser and stronger interconnected framework network in the three-dimensional porous structure to meet higher interface load strength and functionalization requirements.

[0214] (1) Pretreatment of sedimentation precursor solution

[0215] 500 nm diameter silica (SiO2) microspheres with hydroxylated surfaces were selected as templates, and graphene nanosheets (1-3 layers) were selected as framework materials, with a mass ratio of 1:2.

[0216] Graphene sheets were pre-dispersed in a mixed solvent (ethanol / deionized water, volume ratio 4:1), and 0.3 wt% gelatin and 0.1 wt% PVP were added as dispersion stabilizers. After ultrasonic treatment for 45 minutes, SiO2 microsphere suspension was slowly added, and the mixture was mixed and dispersed again for 10 minutes to obtain a uniform deposition precursor solution.

[0217] At this point, the solution is dark black with a slightly high viscosity, and the microspheres are surrounded by graphene sheets, indicating that the framework material is well distributed and has synergistic deposition capability.

[0218] (2) Ordered array construction steps

[0219] refer to Figure 1 The deposition system shown has a 5cm long carbon fiber bundle (4) fixed to the cathode, a platinum electrode as the anode, an electrode spacing of 2cm, a voltage of 15V, and an electrophoretic deposition time of 120 seconds.

[0220] During electrophoretic deposition, SiO2 microspheres and graphene sheets migrate synchronously to the fiber surface. Due to the increased graphene content, it forms a "multi-layer coating + overlapping" state between the microspheres, creating a continuous support system in the composite layer.

[0221] After deposition, the sample was dried in a 55°C oven for 40 minutes, inducing the SiO2 microspheres to complete hexagonal stacking and self-assemble into an ordered structure. Simultaneously, the graphene sheets were fixed to form a tightly packed three-dimensional composite framework, such as... Figure 2 and Figure 3As shown.

[0222] (3) Template etching steps

[0223] Etching was performed using a 5 wt% hydrofluoric acid (HF) solution, which was allowed to stand and soak at room temperature for 20 minutes, with the solution being replaced with fresh solution once. To avoid disturbing the film layers, the etching process was carried out without stirring. Immediately after treatment, the film was rinsed with plenty of deionized water, followed by replacement of the solution with anhydrous ethanol and drying.

[0224] After etching, the SiO2 microspheres are completely removed, leaving only the high-density graphene three-dimensional framework.

[0225] (4) Structural characterization

[0226] like Figure 4 As shown, the SEM observation results indicate that:

[0227] The cavity structure is complete, the pore size is regular, and the edge contour is clear;

[0228] The graphene sheets form a multi-layered entanglement structure between the pore walls, exhibiting extremely strong interconnectivity;

[0229] In some areas, multiple layers of graphene folds are superimposed, which effectively improves the toughness and stability of the skeleton.

[0230] The network structure has significantly enhanced resistance to collapse and is suitable for high-stress interface scenarios.

[0231] In addition, AFM (atomic force microscopy) measurements showed that the average thickness of the etched skeleton increased to about 100-150 nm, which is much higher than that of the 1:1 skeleton layer, demonstrating stronger load-bearing capacity.

[0232] (5) Performance evaluation and functional performance

[0233] The tensile strength of the monofilament reaches 3930 MPa, an increase of approximately 12%;

[0234] The interfacial shear strength (IFSS) reaches 50 MPa, an improvement of approximately 78%;

[0235] The interfacial thermal conductivity was increased to 1.9 W / m·K (approximately 25% higher than the original fiber interface);

[0236] Surface resistivity decreased to 7×10 4 Ω / sq, with a good conductivity network.

[0237] Multiple test results show that increasing the proportion of graphene helps to construct a high-density, high-functionality three-dimensional framework layer, meeting the technical requirements of multifunctional composite material interfaces that simultaneously possess mechanical reinforcement, thermal conductivity, electrical conductivity, and electromagnetic shielding.

[0238] This embodiment verifies the feasibility and advantages of increasing the graphene proportion to twice during the microsphere template construction process. While ensuring structural integrity, it further enhances the mechanical support and multiple physical properties of the framework, making it particularly suitable for the engineering application of interface layers in multifunctional integrated composite structures (such as electromagnetic shielding shells, structural batteries, and thermal interface encapsulation materials).

[0239] In summary, this invention provides a controllable method for constructing three-dimensional ordered porous structures on the fiber surface of fiber-reinforced composite materials. Through the synergistic deposition, self-assembly, and template etching processes of template microspheres and various skeleton materials, precise construction of three-dimensional ordered structures on fiber surfaces with different curvatures is achieved. This method overcomes the limitations of traditional two-dimensional roughening techniques, significantly enhancing the interfacial mechanical interlocking effect and stress dispersion capability. It also possesses good material versatility, structural adaptability, and process controllability, making it applicable to multiple engineering fields such as aerospace, rail transportation, and automotive lightweighting.

[0240] It should be understood that although this specification has described the invention in detail through specific embodiments, the scope of protection of the invention is not limited thereto. Various equivalent substitutions, modifications, and optimizations made to the invention by those skilled in the art without departing from the spirit and substance of the invention should still fall within the scope of protection of the invention.

Claims

1. A method for controllable construction of three-dimensional ordered porous structures on a fiber surface, characterized in that, The method comprises the following steps: (1) Pre-deposition precursor liquid pretreatment: mixing the template microsphere suspension and the skeleton material in a predetermined ratio in a solvent, and treating by ultrasonic dispersion to obtain a uniformly dispersed pre-deposition precursor liquid; (2) Ordered array construction: driving the pre-deposition precursor liquid to migrate directionally to the surface of the fiber by electrophoretic deposition technology to form a non-tight composite layer of microspheres and skeleton material; and then inducing self-assembly by solvent evaporation to make the microspheres and skeleton material closely arrange to form a three-dimensional ordered composite structure; (3) Template controllable etching: performing selective etching treatment on the three-dimensional ordered composite structure to remove the template microspheres and retain the skeleton material, and obtaining a three-dimensional ordered porous skeleton with inverse opal structure.

2. The construction method according to claim 1, wherein: the template microspheres are monodisperse microspheres, including polystyrene microspheres or silica microspheres, and the surface hydrophilicity or hydrophobicity or reactivity thereof is controllable.

3. The construction method according to claim 1, wherein: the skeleton material is at least one selected from carbon nanotubes, graphene, MXene, and metal nanoparticles (gold, silver, copper, platinum); and the size of the skeleton material needs to meet the following conditions: (a) being able to effectively fill the gap between the microspheres; and (b) forming a self-supporting porous structure through three-dimensional network interconnection after etching.

4. The construction method according to claim 1, wherein: the fiber is carbon fiber, glass fiber, aramid fiber, or silicon carbide fiber; and the matrix of the fiber composite material includes epoxy resin, phenolic resin, polyurethane resin, or polyester resin.

5. The construction method according to claim 1, wherein: in the ordered array construction step, the fiber after electrophoretic deposition is induced to self-assemble by solvent evaporation at 40-70°C.

6. The construction method according to claim 1, wherein: the template controllable etching includes solvent etching or pyrolysis etching: in the solvent etching, polystyrene microspheres are etched by tetrahydrofuran or toluene, and silica microspheres are etched by hydrofluoric acid solution; and in the pyrolysis etching, polystyrene microspheres are decomposed at a high temperature of 250-500°C.

7. The construction method according to claim 1, wherein: the mixing ratio of the template microspheres to the skeleton material is 1:1 to 1:

2.

8. The construction method according to claim 1, wherein: the interfacial shear strength of the obtained three-dimensional ordered porous structure is increased by more than 60% compared with that of an unmodified fiber, and the tensile strength of a single filament is increased by more than 10%.

9. A fiber-reinforced composite material, wherein: the surface of the fiber is constructed with a three-dimensional ordered porous structure by the method according to any one of claims 1-8. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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