Lightning protection composite material with three-dimensional gradient network structure and preparation method thereof

Abstract

The invention relates to the field of structural / functional composite materials, in particular to a lightning protection composite material with a three-dimensional gradient network structure and a preparation method of the lightning protection composite material. Carbon nano tubes are used as raw materials, carbon nano tube chopped fibers with different size distributions are obtained by adopting a wet spinning process, a carbon fiber three-dimensional network structure with a gradient pore structure is used as a construction skeleton, and the carbon fiber three-dimensional network structure is compounded with the carbon nano tube chopped fibers, so that the composite material is obtained. Chopped carbon nano tube fibers are wrapped, wound and adsorbed in a carbon fiber network skeleton with a gradient pore structure to obtain a carbon fiber / carbon nano tube composite three-dimensional gradient network structure layer, the carbon fiber / carbon nano tube composite three-dimensional gradient network structure layer is used as a surface lightning protection layer of the composite material, and then the carbon fiber / carbon nano tube composite three-dimensional gradient network structure layer, glass fibers, carbon fibers and epoxy resin adhesive films are laid in a laminated mode to form a lightning protection layer. And the lightning protection composite material with the three-dimensional gradient network structure is prepared and obtained through resin infiltration curing molding. Therefore, the problems that in the prior art, conductivity is insufficient, density is high, and lightning protection performance and mechanical performance cannot be considered at the same time are solved.

Description

Technical Field

[0001] This invention relates to the field of structural / functional composite materials, specifically to a lightning protection composite material with a three-dimensional gradient network structure and its preparation method, which is suitable for the requirements of aerospace vehicles and other applications for lightning protection, lightweighting, and mechanical properties. Background Technology

[0002] In recent years, with the urgent need for increased speed and weight reduction in aerospace equipment such as aircraft, rockets, and missiles, fiber-reinforced resin matrix composites have been widely used in aircraft design and manufacturing due to their lightweight and high-strength properties. While the use of fiber-reinforced resin matrix composites can significantly reduce fuel consumption and improve the fatigue resistance of aircraft compared to traditional metal materials, their poor electrical conductivity makes their lightning protection performance a significant weakness. Lightning strikes with currents of 40-100 kA can cause catastrophic damage to fiber-reinforced resin matrix composite structures in just a few microseconds. Therefore, based on the extensive application of carbon fiber resin matrix composites and structures in recent years, the domestic and international aerospace industries have increasingly emphasized lightning protection technology for aircraft. Constructing advanced composite materials with integrated structural and functional high-efficiency lightning protection is of great significance for promoting the rapid development of the next generation of spacecraft.

[0003] Currently, the most common method is to improve the surface conductivity of composite materials by flame-spraying a metal layer, laying metal mesh, or applying metal foil to the surface, thereby achieving lightning protection. However, this method has drawbacks such as high density, susceptibility to corrosion, and large thermal deformation. Furthermore, during long-term service, its poor compatibility with the resin matrix can lead to easy peeling. These traditional processes and materials are no longer sufficient to meet the urgent needs of advanced spacecraft for lightweight, high-strength, and highly conductive composite materials.

[0004] Patent CN117359977A discloses a three-dimensional woven preform, a lightning protection composite housing, and its manufacturing method. It relies on normally conductive metal wires to construct a cage-like conductive structure. The density of the metal wires (such as copper wire) is much higher than that of carbon-based materials, resulting in a significant increase in the weight of the composite material. The insulating layer between the metal wires and the fiber bundle affects the continuity of conductivity. The poor compatibility between the metal and the resin matrix poses a risk of galvanic corrosion. Long-term use will lead to a decline in lightning protection performance, and the rigidity of the metal wires will affect the overall mechanical toughness of the composite material.

[0005] Patent CN115384133A discloses a synergistic lightning protection composite material and its preparation method. It employs a layered structure of resin conductive nanomaterials and interlayer conductive layers. Current can only be conducted along the interlayer spaces, resulting in uneven conduction. Its highest conductivity is 2.1 S / cm (210 S / m), indicating insufficient lightning current conduction efficiency. Furthermore, the stacking of interlayer conductive layers increases material density, and the interfacial bonding between the conductive layer and the resin matrix depends on lamination, making it prone to delamination during long-term service.

[0006] The patent with publication number CN117567835A proposes a polyether ether ketone-based high thermal conductivity electromagnetic shielding composite material with a three-dimensional carbon network structure and its preparation method. It focuses on electromagnetic shielding and thermal conductivity. The conductive network is a uniformly distributed carbon network, which cannot cope with the problem of local current concentration under lightning impact. Its highest conductivity is 512.8 S / m, and the three-dimensional structural stability of expanded graphite depends on polybenzoxazine support, which is prone to structural damage under lightning impact.

[0007] Patent CN115181340A discloses an electromagnetic shielding natural rubber and its preparation method for effectively constructing a three-dimensional conductive network structure. However, the mechanical strength and high-temperature resistance of the natural rubber matrix cannot meet the requirements for structural composite materials used in aircraft. Furthermore, its three-dimensional conductive network relies on the carbonization of a foam template, resulting in poor uniformity of the conductive pathway and a maximum conductivity of only 9.58 S / m, making it unable to conduct large lightning currents of 40-100 kA.

[0008] Therefore, developing a structural / functional integrated composite material that combines high lightning protection performance, low density, and excellent mechanical properties is of great significance for promoting the development of the next generation of spacecraft. Summary of the Invention

[0009] The main objective of this invention is to provide a lightning protection composite material with a three-dimensional gradient network structure and its preparation method, thereby obtaining a carbon fiber polymer-based composite material that combines high lightning protection performance with low density, solving the problems of insufficient conductivity, high density, and inability to balance lightning protection performance and mechanical properties in the prior art.

[0010] To achieve the above technical objectives, the technical solution proposed by this invention is as follows: A lightning protection composite material with a three-dimensional gradient network structure is characterized by using carbon nanotubes as raw materials and employing a wet spinning process to obtain short carbon nanotube fibers with different size distributions. A three-dimensional carbon fiber network structure with a gradient pore structure is used as a framework, which is then combined with the short carbon nanotube fibers. This allows the short carbon nanotube fibers to coat, entangle, and adsorb within the carbon fiber network framework with a gradient pore structure, resulting in a carbon fiber / carbon nanotube composite three-dimensional gradient network structure layer. This layer serves as the surface lightning protection layer of the composite material. Subsequently, it is laminated with a glass fiber layer, a carbon fiber layer, and an epoxy resin film, and then cured and molded by resin impregnation to obtain the lightning protection composite material with a three-dimensional gradient network structure.

[0011] The lightning protection composite material with a three-dimensional gradient network structure is characterized in that the carbon fiber layer is a carbon fiber fabric or a carbon fiber prepreg, wherein the carbon fiber fabric or prepreg is one or more combinations of orthogonal fabric, unidirectional fabric, and twill fabric; the thickness of the carbon fiber fabric or prepreg is 0.2 mm to 1 mm; the diameter of the carbon fiber is 1 μm to 10 μm; the number of single filaments in the carbon fiber bundle used in the carbon fiber fabric or prepreg is 1 K to 48 K; and the density is 1.5 g / cm³. 3 ~2.0 g / cm 3 The number of carbon fiber layers can range from 1 to 50.

[0012] The lightning protection composite material with a three-dimensional gradient network structure is characterized in that the single-walled carbon nanotube raw material is prepared by chemical vapor deposition, and then the carbon nanotubes are dispersed by hydrogen peroxide pretreatment and micro-jet homogenization process. Short carbon nanotube fibers are obtained by wet spinning process. The carbon nanotube fibers have a bundle structure with a bundle diameter of 10 μm to 50 μm.

[0013] The lightning protection composite material with a three-dimensional gradient network structure is characterized in that the carbon fiber / carbon nanotube composite three-dimensional gradient network structure layer is achieved by preparing a dispersion suspension and combining it with wet melt assembly technology to realize the three-dimensional gradient assembly of short-cut carbon nanotube fibers on the carbon fiber three-dimensional network structure. This results in a dense surface composed of overlapping high aspect ratio carbon nanotube fibers, with continuously increasing porosity and decreasing aspect ratio in layers along the vertical direction of the surface, and a surface conductivity of 1×10⁻⁶. 4 S / m ~ 1×10 5 S / m; The weight ratio of carbon nanotubes to carbon fiber three-dimensional network structure is 1:4 to 1:5. The thickness of the carbon fiber / carbon nanotube composite three-dimensional gradient network structure layer is 1.005 mm to 5.005 mm. The carbon nanotube film is the surface layer of the composite three-dimensional gradient network structure layer, and the thickness of the carbon nanotube film is 1 μm to 5 μm.

[0014] The lightning protection composite material with a three-dimensional gradient network structure is characterized in that the glass fiber layer is a glass fiber fabric or a glass fiber prepreg, wherein the glass fiber fabric or prepreg is one or more combinations of orthogonal weave, unidirectional weave, and twill weave; the thickness of the glass fiber fabric or prepreg is 0.2 mm to 1 mm; the diameter of the glass fibers is 1 μm to 10 μm; the number of monofilaments in the glass fiber bundles used in the glass fiber fabric or prepreg is 1 K to 48 K; and the density is 1.0 g / cm³. 3 ~5.0 g / cm 3 The number of glass fiber layers can range from 1 to 50.

[0015] The lightning protection composite material with a three-dimensional gradient network structure is characterized by laying up carbon fiber layers and glass fiber layers, attaching a carbon fiber / carbon nanotube composite three-dimensional gradient network structure layer to its surface, and preparing the lightning protection carbon fiber composite material with a three-dimensional gradient network structure by molding.

[0016] The lightning protection composite material with a three-dimensional gradient network structure is characterized in that the carbon fiber three-dimensional network structure is a carbon fiber felt prepared by pre-oxidized fiber winding, vacuum filtration, or integral needle punching, with a density of 0.08 g / cm³. 3 ~0.15 g / cm 3 The thickness is 0.05 mm to 0.5 mm, the electrical conductivity is 400 S / m to 900 S / m, and the porosity is 90% to 99%.

[0017] The lightning protection composite material with a three-dimensional gradient network structure is characterized in that the resin matrix used is a polymer matrix material with good flow properties at room temperature or high temperature, and is made of epoxy resin, phenolic resin, polyimide resin or bismaleimide resin.

[0018] The method for preparing the lightning protection composite material with a three-dimensional gradient network structure is characterized by comprising the following steps: (1) Using carbon nanotubes as raw materials, after chemical vapor deposition, hydrogen peroxide pretreatment and micro-jet homogenization dispersion, carbon nanotube short fibers with different size distributions are prepared by wet spinning process. (2) A three-dimensional carbon fiber network with a gradient pore structure is prepared by pre-oxidized fiber winding molding, vacuum filtration or integral needle punching molding method; (3) Prepare a dispersion suspension and combine it with wet melt assembly technology to composite the carbon nanotube short fibers on the carbon fiber three-dimensional network to prepare a carbon nanotube / carbon fiber three-dimensional gradient network structure composite material. (4) The carbon nanotube / carbon fiber three-dimensional gradient network structure composite material is used as a surface lightning protection layer and is laminated with glass fiber layer, carbon fiber layer and epoxy resin film. (5) The lightning protection composite material is obtained by using vacuum-assisted resin transfer molding, resin conduction molding, autoclave molding, compression molding or hand lay-up molding processes, followed by resin impregnation and curing.

[0019] The design concept of this invention is: To address the challenge of simultaneously achieving significantly enhanced lightning protection performance and reduced density in carbon fiber reinforced resin matrix composites using existing methods, this invention proposes a method that uses high-quality single-walled carbon nanotubes as raw material. This method combines hydrogen peroxide pretreatment with microfluidic homogenization to achieve non-destructive and efficient dispersion of carbon nanotubes. A wet spinning process is employed to achieve dense, oriented arrangement of carbon nanotube fibers through extrusion orientation and traction solidification. By controlling process parameters such as fiber extrusion diameter, porosity, and fiber length, short-cut carbon nanotube fibers with different size distributions are obtained. Using carbon nanotube fibers with different size distributions as building blocks of a gradient three-dimensional network, three-dimensional gradient assembly of short-cut carbon nanotube fibers is achieved by preparing dispersion suspensions of different concentrations and combining them with wet melt assembly technology. This results in a three-dimensional assembly of gradient carbon nanotube fibers with a dense surface composed of overlapping high aspect ratio carbon nanotube fibers, exhibiting continuously increasing porosity and decreasing aspect ratio along the vertical direction of the surface. Using a gradient-structured three-dimensional carbon fiber network (carbon fiber felt) as the basic building block, it is composited with single-walled carbon nanotubes to obtain a carbon fiber / carbon nanotube composite three-dimensional gradient network structure layer. This layer is then laid with carbon fiber cloth and glass fiber cloth layers, and cured with resin to obtain a lightning protection carbon fiber composite material with a three-dimensional gradient network structure. This invention fully leverages the significant advantages of the three-dimensional gradient network structure of carbon fiber felt, combined with the excellent electrical and thermal conductivity and low-density structural characteristics of carbon nanotubes. Through microstructure and micro-interface control, the electrical conductivity, thermal conductivity, and mechanical properties of the composite material system are optimized, resulting in a multi-scale hybrid advanced composite material that combines high lightning protection performance with low density.

[0020] The advantages and beneficial effects of this invention are: 1. This invention prepares carbon nanotube chopped fibers with ultra-high electrical conductivity and fully leverages the advantages of the high conductivity, large porosity, and low density of the three-dimensional gradient network structure of carbon fiber felt. By composited with single-walled carbon nanotube chopped fibers exhibiting excellent conductivity, a carbon fiber / carbon nanotube composite three-dimensional gradient network hybrid composite material is obtained. This material is then layered with carbon fiber cloth and glass fiber cloth to construct a highly oriented layered gradient multi-scale hybrid structure with conductive, thermally insulating, and structural strength layers. This effectively improves the lightning protection performance of the carbon fiber composite material, especially by reducing density. While meeting current requirements for high-efficiency lightning protection, it effectively avoids excessive weight gain. Furthermore, the three-dimensional network of the carbon fiber felt facilitates thorough resin impregnation; on the other hand, the carbon nanotube chopped fibers form mechanically interlocked bridging microstructures between the carbon fiber felt and the polymer, enhancing the interfacial bonding between the three-dimensional carbon fiber felt and the polymer, thereby significantly improving the mechanical properties of the carbon fiber composite material.

[0021] 2. This invention achieves simultaneous improvement in lightning protection performance and weight reduction of carbon fiber laminated composite materials by organically combining a three-dimensional gradient network structure of carbon fiber felt with high-conductivity single-walled carbon nanotube bundles, and by comprehensively regulating the micro-nano structure and lightning protection mechanism of the composite material. The electrical conductivity of the composite material was tested, showing a conductivity of 700 S / m to 1500 S / m. Furthermore, the out-of-plane thermal conductivity of the composite material was tested, showing an out-of-plane thermal conductivity of 0.5 W / (m·K) to 1.5 W / (m·K). The mechanical properties of the composite material were tested, showing a flexural modulus of 45 GPa to 70 GPa. Attached Figure Description

[0022] Figure 1 Optical microscope image of a single-walled carbon nanotube / carbon fiber felt / carbon fiber / glass fiber / epoxy resin composite material.

[0023] Figure 2 This is a schematic diagram of the vertical cross-section of a hybrid composite material integrating structural and lightning protection features. In the diagram, 1 represents a carbon fiber prepreg layer, 2 a glass fiber prepreg layer, 3 a three-dimensional gradient network structure composite material layer of carbon nanotubes / carbon fiber felt, and 4 an epoxy resin layer. Detailed Implementation

[0024] To facilitate understanding of the present invention, a more comprehensive description will be provided below. The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural modifications made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

[0025] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0026] In its specific implementation, this invention uses high-quality single-walled carbon nanotubes as raw materials. A combination of hydrogen peroxide pretreatment and microfluidic homogenization processes is used to achieve non-destructive and efficient dispersion of carbon nanotubes. A wet spinning process is employed to achieve dense, oriented arrangement of carbon nanotube fibers through extrusion orientation and traction coagulation. By controlling process parameters such as fiber extrusion diameter, porosity, and fiber length, short-cut carbon nanotube fibers with different size distributions are obtained. Using carbon nanotube fibers with different size distributions as building blocks of a gradient three-dimensional network, three-dimensional gradient assembly of short-cut carbon nanotube fibers is achieved by preparing dispersion suspensions of different concentrations and combining them with wet melt assembly technology. This results in a dense three-dimensional assembly of gradient carbon nanotube fibers formed by overlapping high aspect ratio carbon nanotube fibers, with continuously increasing porosity and decreasing aspect ratio along the vertical direction of the surface. Using a gradient-structured carbon fiber three-dimensional network as the basic building block, it is combined with single-walled carbon nanotubes to obtain a carbon fiber / carbon nanotube composite three-dimensional gradient network structure layer. This layer is then laid with carbon fiber cloth and glass fiber cloth, and cured with resin to obtain a lightning protection composite material with a three-dimensional gradient network structure.

[0027] like Figure 2As shown, the structural / lightning protection integrated hybrid composite material of embodiments 1-3 of the present invention is laid in layers in the order of "outer surface → inner surface": the upper surface is a layer of carbon nanotube / carbon fiber felt three-dimensional gradient network structure composite material layer 3, immediately below it is a composite area of ​​an epoxy resin layer 4 and two glass fiber prepreg layers 2, and the lower surface is ten layers of carbon fiber prepreg layer 1 (corresponding to the black and white alternating layered area in the lower part of the figure). The function and structure of each layer correspond: the carbon nanotube / carbon fiber felt three-dimensional gradient network structure composite material layer 3 serves as the core layer of surface lightning protection, directly bearing lightning strikes; the epoxy resin layer 4 and the glass fiber prepreg layer 2 are combined to form a bonding buffer area, realizing the connection between the protective layer and the structural layer; the carbon fiber prepreg layer 1 adopts 0° / 90° orthogonal layup (black and white layered schematic diagram in the figure), providing core mechanical support and assisting in current conduction. After each layer is impregnated and cured with resin, an integrated structure is formed. The lightning current is dispersed through the three-dimensional gradient network structure composite material layer 3 of carbon nanotube / carbon fiber felt (the blue arrow in the figure represents the current flowing through the short carbon nanotube fibers in the three-dimensional gradient network structure composite material layer 3 of carbon nanotube / carbon fiber felt, which is laterally dispersed through the three-dimensional gradient network). After being buffered by the glass fiber prepreg layer 2 and the epoxy resin layer 4, the connection between the protective layer and the structural layer is achieved, and the direct breakdown of the current is blocked (the "×" at the red arrow in the figure is indicated). The carbon fiber prepreg layer 1 assists in the conduction and finally grounds the ground. At the same time, the Joule heat (green arrow in the figure) is evenly dissipated through the gradient network to avoid local overheating.

[0028] The present invention will be further described below with reference to specific embodiments, but the invention is not limited to the embodiments described: Example 1

[0029] In this embodiment, the specific preparation parameters for the carbon nanotube / carbon fiber felt / carbon fiber / glass fiber / epoxy resin composite material are as follows: Single-walled carbon nanotubes were selected and prepared by chemical vapor deposition. After hydrogen peroxide pretreatment and microfluidic homogenization, the carbon nanotubes were dispersed and chopped into short carbon nanotube fibers with a bundle diameter of 20 μm and a sheet conductivity of 80 mΩ / sq were obtained by wet spinning.

[0030] The carbon fiber fabric layers are made of T700 unidirectional carbon fiber prepreg, with each layer having a thickness of 0.15 mm and a fiber areal density of 150 g / m³. 2 The epoxy resin content is 30wt%, and it is laid up in 10 layers.

[0031] The fiberglass cloth layers are made of S17500 unidirectional fiberglass prepreg, with each layer having a thickness of 0.15 mm and a fiber areal density of 175 g / m². 2 The epoxy resin content is 30wt%, and it is laid up in 2 layers.

[0032] The carbon fiber three-dimensional gradient network structure uses carbon fiber felt prepared by integral needle punching, with an areal density of 50 g / m³. 2 It has a porosity of 90%, a thickness of 0.26 mm, and an electrical conductivity of 700 S / m.

[0033] Short carbon nanotube fibers are produced by mixing single-walled carbon nanotubes with chlorosulfonic acid to form a liquid crystal spinning solution. The spinning solution is then slowly injected into a high-speed rotating N-methylpyrrolidone coagulation bath at a rate of 0.01 mL / min using an injection pump. Under the shear force of the coagulation bath, the spinning solution breaks into uniform single-walled carbon nanotube short fibers.

[0034] A three-dimensional gradient network structure composite material was prepared by introducing short carbon nanotube fibers into the surface of a three-dimensional carbon fiber felt network using a wet melting method. The weight ratio of carbon nanotubes to carbon fiber felt was 1:5, and the thickness of the carbon nanotube layer was 100 μm to 200 μm.

[0035] Using carbon fiber prepreg as the matrix, the laminated material was cured under high temperature and pressure through a molding process. The laminated material was then cured according to the curing process specified for the prepreg to obtain a structural lightning protection integrated hybrid composite material. Due to the compression effect of the template on the horizontally laid carbon nanotube / carbon fiber felt composite film and carbon fiber prepreg, the thickness of the resulting structural lightning protection integrated hybrid composite material was 1.72 mm.

[0036] The electrical conductivity of the composite material was tested and found to be 10¹⁵ S / m. Furthermore, the thermal conductivity of the composite material was tested and found to be 0.86567 W / (m·K). The mechanical properties of the composite material were tested and found to have a flexural modulus of 61 GPa.

[0037] Example 2

[0038] In this embodiment, the specific preparation parameters for the carbon nanotube / carbon fiber felt / carbon fiber / glass fiber / epoxy resin composite material are as follows: Single-walled carbon nanotubes were selected and prepared by chemical vapor deposition. After hydrogen peroxide pretreatment and microfluidic homogenization, the carbon nanotubes were dispersed and chopped into short carbon nanotube fibers with a bundle diameter of 5 μm and a sheet conductivity of 20 mΩ / sq were obtained by wet spinning.

[0039] The carbon fiber fabric layers are made of T700 unidirectional carbon fiber prepreg, with each layer having a thickness of 0.15 mm and a fiber areal density of 150 g / m³. 2 The epoxy resin content is 30wt%, and it is laid up in 10 layers.

[0040] The fiberglass cloth layers are made of S17500 unidirectional fiberglass prepreg, with each layer having a thickness of 0.15 mm and a fiber areal density of 175 g / m². 2 The epoxy resin content is 30wt%, and it is laid up in 2 layers.

[0041] The carbon fiber three-dimensional gradient network structure uses carbon fiber felt prepared by integral needle punching, with an areal density of 50 g / m³. 2 It has a porosity of 90%, a thickness of 0.27 mm, and an electrical conductivity of 700 S / m.

[0042] Short carbon nanotube fibers are produced by mixing single-walled carbon nanotubes with chlorosulfonic acid to form a liquid crystal spinning solution. The spinning solution is then slowly injected into a high-speed rotating N-methylpyrrolidone coagulation bath at a rate of 0.01 mL / min using an injection pump. Under the shear force of the coagulation bath, the spinning solution breaks into uniform single-walled carbon nanotube short fibers.

[0043] A three-dimensional gradient network structure composite material was prepared by introducing short carbon nanotube fibers into the surface of a three-dimensional carbon fiber felt network using a wet melting method. The weight ratio of carbon nanotubes to carbon fiber felt was 1:5, and the thickness of the carbon nanotube layer was 60 μm to 100 μm.

[0044] Using carbon fiber prepreg as the matrix, the laminated material was cured under high temperature and pressure through compression molding. The laminated material was then cured according to the curing process specified for the prepreg to obtain a structural lightning protection integrated hybrid composite material. Due to the compression effect of the template on the horizontally laid carbon nanotube / carbon fiber felt composite film and carbon fiber prepreg, the thickness of the resulting structural lightning protection integrated hybrid composite material was 1.48 mm.

[0045] The electrical conductivity of the composite material was tested and found to be 1173 S / m. Furthermore, the thermal conductivity of the composite material was tested and found to be 0.8856 W / (m·K). The mechanical properties of the composite material were tested and found to have a flexural modulus of 55 GPa.

[0046] Example 3

[0047] In this embodiment, the specific preparation parameters for the carbon nanotube / carbon fiber felt / carbon fiber / glass fiber / epoxy resin composite material are as follows: Single-walled carbon nanotubes were selected and prepared by chemical vapor deposition. After hydrogen peroxide pretreatment and microfluidic homogenization, the carbon nanotubes were dispersed and then chopped into short carbon nanotube fibers with a bundle diameter of 50 μm and a sheet conductivity of 100 mΩ / sq were obtained by wet spinning.

[0048] The carbon fiber fabric layers are made of T700 unidirectional carbon fiber prepreg, with each layer having a thickness of 0.15 mm and a fiber areal density of 150 g / m³. 2 The epoxy resin content is 30wt%, and it is laid up in 10 layers.

[0049] The fiberglass cloth layers are made of S17500 unidirectional fiberglass prepreg, with each layer having a thickness of 0.15 mm and a fiber areal density of 175 g / m². 2 The epoxy resin content is 30wt%, and it is laid up in 2 layers.

[0050] The carbon fiber three-dimensional gradient network structure uses carbon fiber felt prepared by integral needle punching, with an areal density of 50 g / m³. 2 It has a porosity of 90%, a thickness of 0.26 mm, and an electrical conductivity of 700 S / m.

[0051] Short carbon nanotube fibers are produced by mixing single-walled carbon nanotubes with chlorosulfonic acid to form a liquid crystal spinning solution. The spinning solution is then slowly injected into a high-speed rotating N-methylpyrrolidone coagulation bath at a rate of 0.01 mL / min using an injection pump. Under the shear force of the coagulation bath, the spinning solution breaks into uniform single-walled carbon nanotube short fibers.

[0052] A three-dimensional gradient network structure composite material was prepared by introducing short carbon nanotube fibers into the surface of a three-dimensional carbon fiber felt network using a wet melting method. The weight ratio of carbon nanotubes to carbon fiber felt was 1:5, and the thickness of the carbon nanotube layer was 180 μm to 200 μm.

[0053] Using carbon fiber prepreg as the matrix, the laminated material was cured under high temperature and pressure through a molding process. The laminated material was then cured according to the curing process specified for the prepreg to obtain a structural lightning protection integrated hybrid composite material. Due to the compression effect of the template on the horizontally laid carbon nanotube / carbon fiber felt composite film and carbon fiber prepreg, the thickness of the resulting structural lightning protection integrated hybrid composite material was 1.80 mm.

[0054] The electrical conductivity of the composite material was tested and found to be 955 S / m. Furthermore, the thermal conductivity of the composite material was tested and found to be 0.68549 W / (m·K). The mechanical properties of the composite material were tested and found to have a flexural modulus of 66 GPa.

[0055] like Figure 1The image shows an optical microscope photograph of a single-walled carbon nanotube / carbon fiber mat / carbon fiber / glass fiber / epoxy resin composite material. The upper region of the image shows the single-walled carbon nanotube / carbon fiber mat composite structure: short-cut single-walled carbon nanotube fibers (fine fibers) are uniformly coated and wound around the surface of the carbon fiber mat (porous network), forming a continuous three-dimensional network structure. There is no obvious agglomeration or separation between the carbon nanotubes and the carbon fiber mat, demonstrating the uniform composite effect of the wet melt assembly process. The middle region of the image shows the glass fiber / epoxy resin interface: the glass fiber is fully impregnated with epoxy resin, and there are no obvious gaps at the fiber-resin interface, reflecting the compactness of the resin impregnation process. The lower region of the image shows the carbon fiber / epoxy resin interface: the carbon fiber and epoxy resin are tightly bonded, with carbon fibers at different layup angles (corresponding to...) Figure 2 The 0° / 90° orthogonal lay-ups are arranged in an orderly manner, with no slippage or delamination between layers, demonstrating the structural integrity of the lamination curing process. Consequently, the functional components exhibit tight interfacial bonding and a uniform and continuous microstructure, further proving that the preparation process can achieve integrated composite of carbon nanotubes, carbon fiber mat, glass fiber, carbon fiber, and epoxy resin, exhibiting excellent lightning protection and mechanical properties.

[0056] The results show that this invention fully leverages the significant advantages of the three-dimensional gradient network structure of carbon fiber felt, and combines the excellent electrical and thermal conductivity of carbon nanotubes with their low-density structural characteristics. Through microstructure and micro-interface regulation, the electrical conductivity, thermal conductivity, and mechanical properties of the composite material system are optimized, resulting in a multi-scale hybrid advanced composite material that combines high lightning protection performance with low density.

Claims

1. A lightning protection composite material with a three-dimensional gradient network structure, characterized in that, Using carbon nanotubes as raw material, short carbon nanotube fibers with different size distributions are obtained through wet spinning. A three-dimensional carbon fiber network structure with a gradient pore structure is used as the skeleton and combined with the short carbon nanotube fibers. The short carbon nanotube fibers are coated, wrapped, and adsorbed in the carbon fiber network skeleton with a gradient pore structure to obtain a carbon fiber / carbon nanotube composite three-dimensional gradient network structure layer. This layer is used as the surface lightning protection layer of the composite material. Then, it is laminated with a glass fiber layer, a carbon fiber layer, and an epoxy resin film. After resin impregnation and curing, a lightning protection composite material with a three-dimensional gradient network structure is prepared.

2. The lightning protection composite material with a three-dimensional gradient network structure according to claim 1, characterized in that, The carbon fiber layer is made of carbon fiber fabric or carbon fiber prepreg, which is one or more combinations of cross-woven, unidirectional, and twill fabrics. The thickness of the carbon fiber fabric or carbon fiber prepreg is 0.2 mm to 1 mm, the diameter of the carbon fiber is 1 μm to 10 μm, and the number of single filaments in the carbon fiber tow used in the carbon fiber fabric or carbon fiber prepreg is 1 K to 48 K, with a density of 1.5 g / cm³. 3 ~2.0 g / cm 3 The number of carbon fiber layers can range from 1 to 50.

3. The lightning protection composite material with a three-dimensional gradient network structure according to claim 1, characterized in that, Single-walled carbon nanotube raw materials are prepared by chemical vapor deposition, and then carbon nanotubes are dispersed by hydrogen peroxide pretreatment and microfluidic homogenization process. Short carbon nanotube fibers are obtained by wet spinning process. The carbon nanotube fibers have a bundle structure with a bundle diameter of 10 μm to 50 μm.

4. The lightning protection composite material with a three-dimensional gradient network structure according to claim 1, characterized in that, The carbon fiber / carbon nanotube composite three-dimensional gradient network structure was achieved by preparing a dispersion suspension and combining it with wet melt assembly technology to realize the three-dimensional gradient assembly of short-cut carbon nanotube fibers on a carbon fiber three-dimensional network structure. This resulted in a dense three-dimensional assembly of high aspect ratio carbon nanotube fibers, characterized by continuously increasing porosity and decreasing aspect ratio along the vertical direction of the surface, with a surface conductivity of 1×10⁻⁶. 4 S / m ~ 1×10 5 S / m; The weight ratio of carbon nanotubes to carbon fiber three-dimensional network structure is 1:4 to 1:

5. The thickness of the carbon fiber / carbon nanotube composite three-dimensional gradient network structure layer is 1.005 mm to 5.005 mm. The carbon nanotube film is the surface layer of the composite three-dimensional gradient network structure layer, and the thickness of the carbon nanotube film is 1 μm to 5 μm.

5. The lightning protection composite material with a three-dimensional gradient network structure according to claim 1, characterized in that, The glass fiber layer is a glass fiber fabric or glass fiber prepreg, which is one or more combinations of cross-woven, unidirectional, and twill fabrics. The thickness of the glass fiber fabric or glass fiber prepreg is 0.2 mm to 1 mm, the diameter of the glass fibers is 1 μm to 10 μm, the number of monofilaments in the glass fiber bundles used in the glass fiber fabric or glass fiber prepreg is 1 K to 48 K, and the density is 1.0 g / cm³. 3 ~5.0 g / cm 3 The number of glass fiber layers can range from 1 to 50.

6. The lightning protection composite material with a three-dimensional gradient network structure according to claim 1, characterized in that, Carbon fiber and glass fiber layers are laid up, and a carbon fiber / carbon nanotube composite three-dimensional gradient network structure layer is attached to its surface. Lightning protection carbon fiber composite material with a three-dimensional gradient network structure is prepared by molding.

7. The lightning protection composite material with a three-dimensional gradient network structure according to claim 1, characterized in that, The three-dimensional carbon fiber network structure is a carbon fiber felt prepared by pre-oxidized fiber winding, vacuum filtration, or integral needle punching, with a density of 0.08 g / cm³. 3 ~0.15 g / cm 3 The thickness is 0.05 mm to 0.5 mm, the electrical conductivity is 400 S / m to 900 S / m, and the porosity is 90% to 99%.

8. The lightning protection composite material with a three-dimensional gradient network structure according to claim 1, characterized in that, The resin matrix used is a polymer matrix material with good flow properties at room temperature or high temperature, such as epoxy resin, phenolic resin, polyimide resin or bismaleimide resin.

9. A method for preparing a lightning protection composite material with a three-dimensional gradient network structure as described in any one of claims 1 to 8, characterized in that, Includes the following steps: (1) Using carbon nanotubes as raw materials, after chemical vapor deposition, hydrogen peroxide pretreatment and micro-jet homogenization dispersion, carbon nanotube short fibers with different size distributions are prepared by wet spinning process. (2) A three-dimensional carbon fiber network with a gradient pore structure is prepared by pre-oxidized fiber winding molding, vacuum filtration or integral needle punching molding method; (3) Prepare a dispersion suspension and combine it with wet melt assembly technology to composite the carbon nanotube short fibers on the carbon fiber three-dimensional network to prepare a carbon nanotube / carbon fiber three-dimensional gradient network structure composite material. (4) The carbon nanotube / carbon fiber three-dimensional gradient network structure composite material is used as a surface lightning protection layer and is laminated with glass fiber layer, carbon fiber layer and epoxy resin film. (5) The lightning protection composite material is obtained by using vacuum-assisted resin transfer molding, resin conduction molding, autoclave molding, compression molding or hand lay-up molding processes, followed by resin impregnation and curing.

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