A wave-absorbing structural composite material and preparation method thereof

Abstract

The present invention provides a composite material for an absorbing structure. The absorbing material comprises, arranged in descending order from top to bottom, a thermal insulation layer, a wave-transmitting layer, a magnetic loss absorbing layer, a reflective layer, and a bearing layer. The magnetic loss absorbing layer comprises multiple magnetic impedance matching layers, the thickness of which increases from the wave-transmitting layer toward the reflective layer. The composite material for an absorbing structure prepared in the present invention exhibits excellent absorbing performance, with an overall electromagnetic wave reflectivity of less than -10 dB, and even less than -15 dB at specific frequencies. Furthermore, the composite material exhibits a tensile strength of 30 MPa or greater, a compressive strength of 100 MPa or greater, a thermal conductivity of 0.6 W / m·K or less, and a linear ablation rate of 0.7 mm / s or less, demonstrating excellent mechanical strength and high-temperature resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of wave-absorbing materials, and in particular to a wave-absorbing structural composite material and a preparation method thereof. Background Art

[0002] When electromagnetic waves emitted by radar strike the surface of an absorbing material, the dielectric within the material converts the waves into other energy sources and dissipates them. Traditional absorbing materials are coated, meaning absorbents are added to the coating material, creating an absorbing coating that is then applied to the surface of the target structure. While coated absorbing materials offer a simple manufacturing process and wide applicability, they still face unavoidable challenges in design and implementation, such as a narrow absorption bandwidth, poor heat resistance, and poor adhesion.

[0003] Radar-absorbing composite materials serve as a component of a target structure. They can bear a certain weight and be formed into various complex shapes to absorb incident electromagnetic waves. Common absorbing composite materials include honeycomb sandwich structures, foam sandwich structures, and short fiber hybrid structures, which can significantly reduce the target component's RCS (radar cross-section).

[0004] However, existing radar-absorbing composite materials suffer from shortcomings such as low strength and poor heat resistance. As targets rapidly advance toward greater speeds and distances, these composite materials struggle to withstand these high-temperature, high-speed conditions, generating heat accumulation due to prolonged, high-speed flight in the atmosphere. This can lead to damage and ablation, significantly limiting their application. Consequently, there is a need to develop composite materials with superior mechanical strength, high-temperature resistance, and excellent absorbing properties. Summary of the Invention

[0005] The present invention provides a wave-absorbing structure composite material and a preparation method thereof. The composite material has the advantages of high strength, high temperature resistance and good wave-absorbing performance.

[0006] In a first aspect, the present invention provides a composite material for an absorbing structure, comprising a thermal insulation layer, a wave-transmitting layer, a magnetic loss absorbing layer, a reflective layer, and a bearing layer arranged in sequence from top to bottom; the magnetic loss absorbing layer comprises a plurality of magnetic impedance matching layers, and the thickness of the magnetic impedance matching layer increases in sequence from the wave-transmitting layer toward the reflective layer.

[0007] Preferably, the number of the magnetic impedance matching layers is 4 to 6;

[0008] The thickness of the magnetic impedance matching layer is 0.3-1 mm; the thickness of adjacent magnetic impedance matching layers increases by 0.1-0.2 mm.

[0009] Preferably, the magnetic impedance matching layer is prepared by mixing phenol-formaldehyde resin and carbonyl iron powder;

[0010] The mass ratio of the phenol-formaldehyde resin to the carbonyl iron powder in the magnetic impedance matching layer decreases from the wave-transmitting layer to the reflective layer.

[0011] More preferably, the mass ratio of the amine novolac resin to the carbonyl iron powder is (0.3-2.5):1; and the reduction range of the mass ratio of the amine novolac resin to the carbonyl iron powder in adjacent magnetic impedance matching layers is 0.3-1.

[0012] Preferably, the thickness of the heat insulation layer is 2-3 mm; the thickness of the wave-transmitting layer is 0.8-1 mm; the thickness of the magnetic loss absorbing layer is 1.8-4.0 mm; and the thickness of the bearing layer is 1-1.2 mm.

[0013] In a second aspect, the present invention provides a method for preparing the wave-absorbing structure composite material according to any one of the first aspects above, the preparation method comprising the following steps:

[0014] (1) providing a reflective layer, and separately preparing a heat-insulating layer, a wave-transmitting layer, a multi-layer magnetic impedance matching layer with different thicknesses, and a bearing layer; compounding the magnetic impedance matching layers in a manner of increasing thickness from top to bottom, and obtaining a magnetic loss absorbing layer after molding;

[0015] (2) The heat-insulating layer, the wave-transmitting layer, the magnetic loss absorbing layer, the reflective layer and the bearing layer are compounded in sequence from top to bottom, and molded to obtain the wave-absorbing structure composite material; wherein, in the magnetic loss absorbing layer, one side of the magnetic impedance matching layer having the largest thickness is in contact with one side of the reflective layer.

[0016] Preferably, in step (1), the heat insulating layer and the bearing layer are both prepared by mixing phenol-formaldehyde resin and quartz fiber, drying them, and then molding them.

[0017] More preferably, the mass ratio of the phenol-formaldehyde resin to the quartz fiber is 1:(0.8-1.0).

[0018] Preferably, in step (1): the preparation method of the wave-transmitting layer is as follows: cyanate resin is coated on the upper and lower surfaces of quartz fiber cloth, and after drying, the wave-transmitting layer is prepared by molding, wherein the number of layers of the quartz fiber cloth is 8 to 10 layers.

[0019] More preferably, in the wave-transmitting layer, the mass ratio of the cyanate resin to the quartz fiber cloth is 1:(0.8-1.0).

[0020] Preferably, in step (1): the preparation method of the magnetic impedance matching layer is as follows: aminephenol-formaldehyde resin and carbonyl iron powder are mixed in different proportions, and magnetic impedance matching layers of different thicknesses are prepared after drying and molding; wherein the mass ratio of the aminephenol-formaldehyde resin to the carbonyl iron powder decreases as the thickness of the magnetic impedance matching layer increases.

[0021] More preferably, the mass ratio of the amine novolac resin and the carbonyl iron powder is (0.3-2.5):1, the mass ratio of the amine novolac resin and the carbonyl iron powder in adjacent magnetic impedance matching layers decreases by 0.3-1; the thickness of the magnetic impedance matching layer is 0.3 mm-1 mm; the thickness of adjacent magnetic impedance matching layers increases by 0.1-0.2 mm.

[0022] Preferably, in step (1), the reflective layer is carbon fiber cloth.

[0023] Preferably, the molding pressure is 2-20 MPa, the temperature is 80-180° C., and the time is 3-9 hours;

[0024] Preferably, during the molding operation, pressure and / or temperature are increased step by step.

[0025] Compared with the prior art, the present invention has at least the following beneficial effects:

[0026] (1) The present invention arranges the wave-absorbing structure composite material into a heat-insulating layer, a wave-transmitting layer, a magnetic loss wave-absorbing layer, a reflecting layer and a bearing layer from top to bottom. The heat-insulating layer is located on the surface of the wave-absorbing structure composite material. It not only has certain high-temperature resistance and mechanical strength, but also has certain wave-transmitting performance. When electromagnetic waves are incident on the surface of the wave-absorbing structure composite material, the electromagnetic waves are incident on the wave-transmitting layer through the heat-insulating layer. A part of the electromagnetic waves are absorbed after passing through the wave-transmitting layer, and the other part of the electromagnetic waves are transmitted to the magnetic loss wave-absorbing layer through the wave-transmitting layer. The magnetic loss medium of the magnetic loss wave-absorbing layer can absorb most of the electromagnetic wave losses, and the electromagnetic waves that are not absorbed by the loss are incident on the reflecting layer, and are reflected again by the reflecting layer to the magnetic loss wave-absorbing layer, and then absorbed by the loss. The present invention realizes multiple absorption of electromagnetic waves by designing a multi-layer structure of the wave-absorbing structure composite material, which can ensure that most of the electromagnetic waves are absorbed. At the same time, in combination with the heat-insulating layer and the bearing layer in the present invention, the wave-absorbing structure composite material in the present invention can have excellent temperature resistance and heat-insulating performance.

[0027] (2) The present invention designs the magnetic loss absorbing layer into a multi-layer magnetic impedance matching layer structure with different thicknesses, and increases the thickness of the magnetic impedance matching layer from the wave-transmitting layer to the reflective layer. This can further ensure that the electromagnetic waves transmitted to the magnetic loss absorbing layer are absorbed as much as possible, thereby further enhancing the absorbing performance of the absorbing structure composite material.

[0028] (3) The absorbing structure composite material prepared in the present invention has excellent absorbing performance, and the overall electromagnetic wave reflectivity is lower than -10dB, and can be lower than -15dB at a specific frequency point; at the same time, the absorbing structure composite material in the present invention has a tensile strength of ≥30MPa, a compressive strength of ≥100MPa, a thermal conductivity of ≤0.6w / m·K, and a linear ablation rate of ≤0.7mm / s, and has excellent mechanical strength and high temperature resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 This is a schematic structural diagram of a wave-absorbing structural composite material provided by the present invention;

[0031] Figure 2 It is a structural schematic diagram of a magnetic loss absorbing layer of a wave absorbing structure composite material provided by the present invention;

[0032] Figure 3 This is a flow chart of a method for preparing a wave-absorbing structure composite material provided by the present invention;

[0033] Figure 4 A graph showing the test results of the wave absorption reflectivity of a wave absorbing structural composite material provided in Example 1 of the present invention;

[0034] Figure 5 A graph showing the test results of the wave absorption reflectivity of a wave absorbing structural composite material provided in Example 2 of the present invention;

[0035] Figure 6 A graph showing the test results of the wave absorption reflectivity of a wave absorbing structural composite material provided in Example 3 of the present invention;

[0036] In the figure: 100 - thermal insulation layer; 200: wave-transmitting layer; 300 - magnetic loss absorbing layer; 301 - first magnetic impedance matching layer; 302 - second magnetic impedance matching layer; 303 - third magnetic impedance matching layer; 304 - fourth magnetic impedance matching layer; 305 - fifth magnetic impedance matching layer; 400 - reflection layer; 500 - bearing layer. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0038] The absorbing structure composite materials in the prior art have poor mechanical strength and are not resistant to high temperatures. Therefore, they are prone to damage and ablation in high temperature and high speed environments, which makes it difficult for the absorbing structure composite materials to achieve good absorbing effects. In view of this, the embodiments of the present invention provide a absorbing structure composite material, such as Figure 1 As shown, it includes a heat insulation layer 100, a wave-transmitting layer 200, a magnetic loss absorbing layer 300, a reflective layer 400 and a bearing layer 500 arranged in sequence from top to bottom; the magnetic loss absorbing layer 300 includes multiple magnetic impedance matching layers, and the thickness of the magnetic impedance matching layer increases in sequence from the wave-transmitting layer 200 to the reflective layer 400.

[0039] In the present invention, a composite material for an absorbing structure (hereinafter referred to as an absorbing material) is designed as a multilayer structure. The direction of electromagnetic wave incidence is defined as the upper surface. The absorbing material includes, from top to bottom, a thermal insulation layer, a wave-transmitting layer, a magnetic loss absorbing layer, a reflective layer, and a bearing layer. The thermal insulation layer and the bearing layer are respectively located on the upper and lower surfaces of the absorbing material, which not only provide the absorbing material with certain thermal insulation performance and mechanical strength, thereby preventing the structure of the absorbing material from being damaged in a high-temperature and high-speed environment, but also have certain wave-transmitting performance. When electromagnetic waves are incident on the surface of the absorbing material, the electromagnetic waves can pass through the thermal insulation layer and enter the wave-transmitting layer. A small portion of the electromagnetic waves is absorbed by the wave-transmitting layer. After most of the electromagnetic waves are incident on the magnetic loss absorbing layer, the electromagnetic waves can be weakened by hysteresis loss. A very small portion of the electromagnetic waves pass through the magnetic loss layer and enter the reflective layer. The reflective layer can reflect them again to the magnetic loss absorbing layer, thereby causing the electromagnetic waves to be absorbed multiple times, thereby effectively improving the absorbing performance of the absorbing material. At the same time, the magnetic loss absorbing layer in the present invention is composed of magnetic impedance matching layers of different thicknesses, and the thickness of the magnetic impedance matching layer increases successively from the wave-transmitting layer to the reflective layer. This can further improve the impedance matching performance of the magnetic loss absorbing layer to electromagnetic waves, thereby further enhancing the absorbing performance of the absorbing material.

[0040] According to some preferred embodiments, the number of the magnetic impedance matching layers 301 is 4 to 6 layers (for example, 4, 5 or 6 layers); the thickness of each magnetic impedance matching layer 301 is 0.3 to 1 mm (for example, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm or 1 mm); the thickness of adjacent magnetic impedance matching layers increases by 0.1 to 0.2 mm (for example, 0.1 mm, 0.12 mm, 0.14 mm, 0.15 mm, 0.18 mm or 0.2 mm).

[0041] In the present invention, the magnetic loss absorbing layer includes multiple layers of magnetic impedance matching layers, and the thickness of each magnetic impedance matching layer is different. When the magnetic loss absorbing layer includes five layers of magnetic impedance matching layers, for example, Figure 2 The thickness of the first magneto-impedance matching layer 301 is the smallest, and then the thicknesses of the second magneto-impedance matching layer 302, the third magneto-impedance matching layer 303, the fourth magneto-impedance matching layer 304 to the fifth magneto-impedance matching layer 305 increase from top to bottom, and the thickness of the fifth magneto-impedance matching layer 305 is the largest. In the present invention, the number of magneto-impedance matching layers is preferably 4 to 6, and more preferably 5. In the present invention, if the number of magneto-impedance matching layers is too low, the absorbing performance of the absorbing material will be reduced. If the number of magneto-impedance matching layers is too large, the thickness of the absorbing material will be too large, and thus the lightweight requirement cannot be met. At the same time, in the present invention, the thickness of the magneto-impedance matching layer is increased from the wave-transmitting layer to the reflective layer, and the amplitude of each increase can be 0.1 to 0.2 mm, which is more conducive to the gradual absorption of electromagnetic waves.

[0042] According to some preferred embodiments, the magnetic impedance matching layer is prepared by mixing phenolic resin and carbonyl iron powder; the mass ratio of phenolic resin and carbonyl iron powder in the magnetic impedance matching layer decreases from the wave-transmitting layer to the reflective layer; the magnetic impedance matching layer of the present invention uses phenolic resin as a matrix and adds carbonyl iron powder to the phenolic resin. The phenolic resin as a matrix can provide a certain mechanical strength for the magnetic impedance matching layer, and the carbonyl iron powder has excellent wave absorbing ability. The two are mixed with each other as the main components of the magnetic impedance matching layer, which can make the magnetic impedance matching have both wave absorbing performance and mechanical strength. At the same time, in the magnetic impedance matching layer, the mass ratio of phenolic resin and carbonyl iron powder increases from the wave-transmitting layer to the reflective layer, and the mass ratio of phenolic resin and carbonyl iron powder decreases with the increase of the thickness of the magnetic impedance matching layer, that is, in the magnetic impedance matching layer with the largest thickness, the mass ratio of phenolic resin and carbonyl iron powder is the smallest; through the design of this structure, the electromagnetic waves incident on the magnetic loss absorbing layer can be absorbed to the maximum extent and the reflection of the electromagnetic waves can be minimized.

[0043] It should be noted that the amine-phenol-formaldehyde resin in the present invention can be directly purchased. The amine-phenol-formaldehyde resin used in the present invention was purchased from Beijing Glass and Steel Institute Composite Materials Co., Ltd.

[0044] In some preferred embodiments, the mass ratio of the phenolic resin and the carbonyl iron powder is preferably (0.3-2.5):1 (for example, it can be 0.3:1, 0.5:1, 0.8:1, 1.0:1, 1.3:1, 1.5:1, 1.8:1, 2.0:1, 2.3:1 or 2.5:1); the mass ratio of the phenolic resin and the carbonyl iron powder in adjacent magnetic impedance matching layers is reduced by 0.3-1 (for example, it can be 0.3, 0.5, 0.8 or 1.0); the present invention further regulates the mass ratio of the phenolic resin and the carbonyl iron powder, and combines the relationship between the thickness of the magnetic impedance matching layer and the mass ratio of the phenolic resin and the carbonyl iron powder, so that the magnetic loss absorbing layer in the present invention has excellent absorbing performance on the basis of good mechanical strength.

[0045] According to some preferred embodiments, the thickness of the thermal insulation layer is 2 to 3 mm (for example, 2 mm, 2.2 mm, 2.5 mm, 2.8 mm or 3 mm); the thickness of the wave-transparent layer is 0.8 to 1 mm (for example, 0.8 mm, 0.9 mm or 1.0 mm); the thickness of the magnetic loss absorbing layer is 1.8 to 4.0 mm (for example, 1.8 mm, 2.0 mm, 2.5 mm, 3 mm, 3.5 or 4 mm); the thickness of the bearing layer is 1 to 1.2 mm (for example, 1.0 mm, 1.1 mm or 1.2 mm).

[0046] The present invention comprehensively considers the structure and thickness of each layer in the absorbing material to ensure that the absorbing material has excellent absorbing performance on the basis of excellent mechanical strength and high-temperature resistance. The absorbing material of the present invention has excellent absorbing performance, with an overall reflectivity of less than -10 dB in the range of 2 to 18 GHz, and a reflectivity of less than -15 dB at specific frequencies. At the same time, the absorbing material of the present invention has a tensile strength of 30 MPa or more, a compressive strength of 100 MPa or more, a thermal conductivity of 0.6 w / m·K or less, and a linear ablation rate of 0.7 mm / s or less. It has excellent mechanical strength and high-temperature resistance, and the absorbing material has strong reliability and applicability in high-temperature and high-speed environments.

[0047] like Figure 3 As shown, the present invention also provides a method for preparing any of the above-mentioned wave-absorbing structure composite materials, the preparation method comprising the following steps:

[0048] (1) providing a reflective layer 400, and separately preparing a heat-insulating layer 100, a wave-transmitting layer 200, a magnetic impedance matching layer of different thicknesses, and a bearing layer 500; compounding the magnetic impedance matching layer in a manner of increasing thickness from top to bottom, and obtaining a magnetic loss absorbing layer 300 after molding;

[0049] (2) The heat insulation layer 100, the wave-transmitting layer 200, the magnetic loss absorbing layer 300, the reflective layer 400 and the bearing layer 500 are compounded in sequence from top to bottom, and molded to obtain the wave-absorbing structure composite material; wherein, in the magnetic loss absorbing layer, one side of the magnetic impedance matching layer with the largest thickness is in contact with one side of the reflective layer.

[0050] In the present invention, when preparing the wave-absorbing structure composite material, a layer of phenol-formaldehyde resin can be first applied to the lower surface of the thermal insulation layer, the wave-transmitting layer, the magnetic loss absorbing layer, the upper and lower surfaces of the reflective layer, and the upper surface of the bearing layer. Then, the thermal insulation layer, the wave-transmitting layer, the magnetic loss absorbing layer, the reflective layer, and the bearing layer are placed in sequence. Finally, the whole is placed in a metal mold with an inner cavity thickness of 7 to 9 mm. After closing the mold, molding is performed. In the present invention, the mold can be placed on a flat hot press for molding. After molding, the wave-absorbing structure composite material can be obtained.

[0051] According to some preferred embodiments, the thermal insulation layer 100 and the bearing layer 500 are both prepared by mixing phenolic resin and quartz fiber, drying them, and then molding them; the mass ratio of the phenolic resin to the quartz fiber is preferably 1:(0.8~1.0) (for example, it can be 1:0.8, 1:0.9 or 1:1.0).

[0052] In the present invention, the heat insulating layer and the load-bearing layer are both prepared by mixing phenolic resin and quartz fiber. The phenolic resin has good high temperature resistance, and the quartz fiber has excellent mechanical properties. The two have good compatibility. The present invention prepares the heat insulating layer and the load-bearing layer by mixing phenolic resin and quartz fiber, and optimizes the mass ratio of phenolic resin and quartz fiber, so that the heat insulating layer and the load-bearing layer not only have excellent mechanical strength and high temperature resistance, but also have good wave transmission performance, which can ensure that electromagnetic waves pass through the heat insulating layer and are incident on the wave-transmitting layer and the magnetic loss absorbing layer to be absorbed; when preparing, the phenolic resin can be mixed with quartz fiber. Phenolic resin and quartz fiber are mixed in proportion, stirred evenly and allowed to stand for 24 hours, then the quartz fiber impregnated with phenolic resin is split and dried, and the dried quartz fiber is placed in a metal mold, and after the mold is closed, it is placed on a flat hot press for molding to obtain a thermal insulation layer; wherein, the depth of the mold cavity is 2 to 3 mm; in the present invention, the preparation method of the bearing layer is the same as the thermal insulation layer method, the difference is that the depth of the metal mold cavity used in preparing the bearing layer is 1.0 to 1.2 mm; it should be noted that, in the present invention, different mold cavity depths can be used to prepare layer structures of different thicknesses.

[0053] The quartz fiber used in the present invention preferably has a tensile breaking force of 7 to 9 N and a length of 5 to 7 cm.

[0054] According to some preferred embodiments, the wave-transmitting layer 200 is prepared as follows: cyanate resin is coated on the upper and lower surfaces of quartz fiber cloth, and after drying, the wave-transmitting layer is prepared by molding, wherein the number of layers of the quartz fiber cloth is 8 to 10 layers (for example, 8 layers, 9 layers, or 10 layers);

[0055] In the wave-transmitting layer 200 , the mass ratio of the cyanate resin to the quartz fiber cloth is preferably 1:(0.8-1.0) (for example, 1:0.8, 1:0.9, or 1:1.0).

[0056] To ensure the temperature resistance and mechanical properties of the wave-transmitting layer, the present invention uses cyanate resin as a matrix and quartz fiber cloth as a reinforcement. The cyanate resin is coated on the upper and lower surfaces of the quartz fiber cloth, and the quartz fiber cloth coated with the cyanate resin is then laid layer by layer. The entire structure is placed in a metal mold, and after the mold is closed, it is placed on a flat hot press for molding. After the mold is opened, the wave-transmitting layer is obtained. The depth of the metal mold is 0.8 to 1.0 mm. The present invention does not impose specific requirements on the thickness of the cyanate resin coating, as long as the cyanate resin is evenly coated on the quartz fiber cloth.

[0057] According to some preferred embodiments, the magnetic impedance matching layer is prepared as follows: amine-phenol-formaldehyde resin and carbonyl iron powder are mixed in different proportions, and the mixture is dried and molded to prepare magnetic impedance matching layers of different thicknesses; wherein the mass ratio of the amine-phenol-formaldehyde resin to the carbonyl iron powder increases with increasing thickness of the magnetic impedance matching layer;

[0058] In each magnetic impedance matching layer, the mass ratio of the phenol-formaldehyde resin to the carbonyl iron powder is preferably (0.3-2.5):1 (for example, 0.3:1, 0.5:1, 0.8:1, 1.0:1, 1.5:1, 1.8:1, 2:1 or 2.5:1), and the mass ratio of the phenol-formaldehyde resin to the carbonyl iron powder in adjacent magnetic impedance matching layers decreases by 0.3-1 (for example, 0.3, 0.5, 0.8 or 1.0);

[0059] The thickness of each magnetic impedance matching layer is preferably 0.3 mm to 1 mm (for example, 0.3 mm, 0.5 mm, 0.8 mm or 1.0 mm); the thickness of adjacent magnetic impedance matching layers increases by 0.1 to 0.2 mm (for example, 0.1 mm, 0.12 mm, 0.14 mm, 0.15 mm, 0.18 mm or 0.2 mm).

[0060] In the present invention, when preparing a magnetic impedance matching layer, phenolic resin and carbonyl iron powder can be mixed in different mass ratios, allowed to stand for 24 hours, and then dried. The dried mixture is placed in metal molds with different cavity depths, and after the molds are closed, the mixture is placed on a flat hot press for molding. After the molds are opened, magnetic impedance matching layers of different thicknesses are obtained. The mass ratio of phenolic resin to carbonyl iron powder is negatively correlated with the depth of the metal mold. For example, when the mass ratio of phenolic resin to carbonyl iron powder is the largest, the cavity depth of the metal mold is the smallest, i.e., the thickness of the magnetic impedance matching layer prepared is the smallest. A layer of phenolic resin is then applied to the upper surface of the thickest magnetic impedance matching layer, the lower surface of the thinnest magnetic impedance matching layer, and the upper and lower surfaces of other magnetic impedance matching layers of varying thicknesses. The mixture is then placed in order of increasing thickness from top to bottom. Finally, the entire mixture is placed in a metal mold with a cavity depth of 2.8 to 3.3 mm. After the molds are closed, the mixture is placed on a flat hot press for molding. After the molds are opened, the magnetic loss absorbing layer is obtained.

[0061] According to some preferred embodiments, the reflective layer 400 is made of carbon fiber cloth.

[0062] In the present invention, the sizes of the layers in the absorbing structure composite material are the same, and the carbon fiber cloth can be cut into the same size as the other layers and then composited with the other layers; there is no special restriction on the thickness of the carbon fiber cloth in the present invention, and the thickness of the carbon fiber cloth commonly used in the prior art can be used.

[0063] According to some preferred embodiments, the molding pressure is 2 to 20 MPa (for example, 2 MPa, 5 MPa, 8 MPa, 10 MPa, 15 MPa or 20 MPa), the temperature is 80 to 180°C (for example, 80°C, 100°C, 120°C, 150°C or 180°C), and the time is 3 to 9 h (for example, 3 h, 5 h, 7 h, 8 h or 9 h).

[0064] It should be noted that, in the process of preparing the absorbing structure composite material, the molding operation can be carried out under the above-mentioned molding conditions; it can also be optimized according to the actual operation within the above-mentioned conditions. For example, in the present invention, when preparing the thermal insulation layer and the wave-transmitting layer, the molding pressure is preferably 10-20 MPa, the temperature is preferably 80-180°C, and the time is preferably 7-9 hours; when preparing the magnetic impedance matching layer, the molding pressure is preferably 8-10 MPa, the temperature is preferably 80-180°C, and the time is preferably 5-7 hours; when preparing the magnetoresistance loss absorbing layer and the absorbing structure composite material, the molding pressure is preferably 2-5 MPa, the temperature is preferably 80-180°C, and the time is preferably 3-4 hours.

[0065] According to some preferred embodiments, when performing the molding operation, it is preferred to perform step-by-step pressure increase and / or step-by-step temperature increase.

[0066] In the present invention, a flat-plate hot press can be used for molding. The step-by-step pressure increase in the present invention specifically refers to increasing the pressure and temperature to the specified pressure and temperature conditions in batches. The present invention does not specifically limit the number of steps. When performing step-by-step pressure increase and step-by-step temperature increase, operations can be performed according to specific instruments.

[0067] In order to more clearly illustrate the technical solutions and advantages of the present invention, a wave-absorbing structural composite material and a preparation method thereof are described in detail below through several embodiments.

[0068] Example 1:

[0069] (1) Providing a reflective layer, cutting the carbon fiber cloth into a specified size to obtain the reflective layer;

[0070] (11) Preparation of thermal insulation layer: phenol-formaldehyde resin and quartz fiber were mixed in a mass ratio of 1:0.8, allowed to stand for 24 hours, split and dried, and the dried quartz fiber was placed in a metal mold with a cavity depth of 2 mm. After the mold was closed, it was placed on a flat hot press for molding to obtain a thermal insulation layer; the molding parameters were: first, the pressure was increased to 5 MPa, then the pressure was increased to 10 MPa, first, the temperature was increased to 80 ° C, then the temperature was increased to 100 ° C, and hot pressed at the above pressure and temperature for 7 hours;

[0071] (12) Preparation of a wave-transmitting layer: 8 sheets of quartz fiber cloth were cut into the same size as the reflective layer, cyanate resin was scraped onto the surface of the quartz fiber cloth, and then the quartz fiber cloth was stacked layer by layer. After drying, the quartz fiber cloth was placed in a metal mold with a cavity depth of 0.8 mm. After the mold was closed, it was placed on a flat hot press for molding. After the mold was opened, the wave-transmitting layer was obtained; the mass ratio of cyanate resin to quartz fiber cloth was 1:0.8; the molding parameters were: first, the pressure was increased to 5 MPa, then the pressure was increased to 10 MPa, first, the temperature was increased to 80°C, then the temperature was increased to 100°C, and hot pressing was performed at the above pressure and temperature for 7 hours;

[0072] (13) Preparation of magnetic loss absorbing layer: carbonyl iron powder and aminophenol-formaldehyde resin were mixed in a mass ratio of 1:2.4, 1:1.4, 1:0.9, 1:0.6 and 1:0.3 respectively, and after standing for 24 hours, they were placed in metal molds with cavity depths of 0.3 mm, 0.4 mm, 0.5 mm, 0.7 mm and 0.9 mm respectively after drying. After the molds were closed, they were placed on a flat hot press for molding. After the molds were opened, magnetic impedance matching layers with thicknesses of 0.3 mm, 0.4 mm, 0.5 mm, 0.7 mm and 0.9 mm were obtained respectively; they were named as the first magnetic impedance matching layer, the second magnetic impedance matching layer, the third magnetic impedance matching layer, the fourth magnetic impedance matching layer and the fifth magnetic impedance matching layer respectively; molding parameters: first increase the pressure to 5 MPa, then increase the pressure to 8 MPa, first increase the temperature to 100 ° C, then increase the temperature to 120 ° C, and hot press for 5 hours at the above pressure and temperature;

[0073] First, a thin layer of phenol-formaldehyde resin is brushed on the lower surface of the first magnetic impedance matching layer, the upper and lower surfaces of the second, third, and fourth magnetic impedance matching layers, and the upper surface of the fifth magnetic impedance matching layer. Then, the magnetic impedance matching layers are compounded in the order of the first impedance matching layer, the second magnetic impedance matching layer, the third magnetic impedance matching layer, the fourth magnetic impedance matching layer, and the fifth magnetic impedance matching layer. The whole is placed in a metal mold with a cavity depth of 2.8 mm. After the mold is closed, it is placed on a flat hot press for molding. After the mold is opened, a magnetic loss absorbing layer is obtained. The upper surface of the first impedance matching layer is the upper surface of the magnetic loss absorbing layer, and the lower surface of the fifth impedance matching layer is the lower surface of the magnetic loss absorbing layer. The molding parameters are as follows: first, the pressure is increased to 2 MPa, then the pressure is increased to 3 MPa, first, the temperature is increased to 50° C., then the temperature is increased to 100° C., and hot pressing is performed at the above pressure and temperature for 3 hours.

[0074] (14) Preparation of the bearing layer: The phenol-formaldehyde resin and the quartz fiber were mixed in a mass ratio of 1:0.8, allowed to stand for 24 hours, and then separated and dried. The dried quartz fiber was placed in a metal mold with a cavity depth of 1 mm. After the mold was closed, it was placed on a flat hot press for molding to obtain a thermal insulation layer; the molding parameters were: first, the pressure was increased to 5 MPa, then the pressure was increased to 10 MPa, first, the temperature was increased to 50 ° C, then the temperature was increased to 100 ° C, and hot pressed at the above pressure and temperature for 7 hours;

[0075] (2) A thin layer of phenol-formaldehyde resin is brushed on the lower surface of the thermal insulation layer, the wave-transmitting layer, the magnetic loss absorbing layer, the upper and lower surfaces of the reflective layer, and the upper surface of the bearing layer. Then, the thermal insulation layer, the wave-transmitting layer, the magnetic loss absorbing layer, the reflective layer, and the bearing layer are compounded together in order. The whole is placed in a metal mold with a cavity depth of 7 mm. After the mold is closed, it is placed on a flat hot press for molding. After the mold is opened, a wave-absorbing structure composite material is obtained; the molding parameters are: first, the pressure is increased to 2 MPa, then the pressure is increased to 3 MPa, first, the temperature is increased to 80°C, then the temperature is increased to 100°C, and hot pressing is carried out at the above pressure and temperature for 3 hours.

[0076] Example 2:

[0077] (1) Providing a reflective layer, cutting the carbon fiber cloth into a specified size to obtain the reflective layer;

[0078] (11) Preparation of thermal insulation layer: phenol-formaldehyde resin and quartz fiber were mixed in a mass ratio of 1:0.9, allowed to stand for 24 hours, separated and air-dried, and the air-dried quartz fiber was placed in a metal mold with a cavity depth of 2.5 mm. After the mold was closed, it was placed on a flat hot press for molding to obtain a thermal insulation layer; the molding parameters were: first, the pressure was increased to 5 MPa, then the pressure was increased to 10 MPa, first, the temperature was increased to 80 ° C, then the temperature was increased to 100 ° C, and hot pressing was performed at the above pressure and temperature for 7 hours;

[0079] (12) Preparation of a wave-transmitting layer: 9 sheets of quartz fiber cloth were cut into the same size as the reflective layer, cyanate ester resin was scraped onto the surface of the quartz fiber cloth, and then the quartz fiber cloth was stacked layer by layer. After drying, the quartz fiber cloth was placed in a metal mold with a cavity depth of 0.9 mm. After the mold was closed, it was placed on a flat hot press for molding. After the mold was opened, the wave-transmitting layer was obtained; the mass ratio of cyanate ester resin to quartz fiber cloth was 1:0.9; the molding parameters were: first, the pressure was increased to 5 MPa, then the pressure was increased to 10 MPa, first, the temperature was increased to 80°C, then the temperature was increased to 100°C, and hot pressing was performed at the above pressure and temperature for 7 hours;

[0080] (13) Preparation of magnetic loss absorbing layer: Carbonyl iron powder and aminophenol-formaldehyde resin were mixed in a mass ratio of 1:2.45, 1:1.45, 1:0.95, 1:0.65, and 1:0.35, respectively. After standing for 24 hours, they were dried and placed in metal molds with cavity depths of 0.35 mm, 0.45 mm, 0.55 mm, 0.75 mm, and 0.95 mm, respectively. After the molds were closed, they were placed on a flat hot press for molding. After the molds were opened, the thicknesses of 0. The magneto-impedance matching layers are 35 mm, 0.45 mm, 0.55 mm, 0.75 mm, and 0.95 mm thick; they are named the first magneto-impedance matching layer, the second magneto-impedance matching layer, the third magneto-impedance matching layer, the fourth magneto-impedance matching layer, and the fifth magneto-impedance matching layer, respectively. The molding parameters are as follows: the pressure is first increased to 5 MPa, then the pressure is increased to 8 MPa, the temperature is first increased to 100°C, then the temperature is increased to 120°C, and hot pressing is performed at the above pressure and temperature for 5 hours;

[0081] First, a thin layer of phenol-formaldehyde resin is brushed on the lower surface of the first magnetic impedance matching layer, the upper and lower surfaces of the second, third, and fourth magnetic impedance matching layers, and the upper surface of the fifth magnetic impedance matching layer. Then, the magnetic impedance matching layers are compounded in the order of the first impedance matching layer, the second magnetic impedance matching layer, the third magnetic impedance matching layer, the fourth magnetic impedance matching layer, and the fifth magnetic impedance matching layer. The whole is placed in a metal mold with a cavity depth of 3.1 mm. After the mold is closed, it is placed on a flat hot press for molding. After the mold is opened, a magnetic loss absorbing layer is obtained. The upper surface of the first impedance matching layer is the upper surface of the magnetic loss absorbing layer, and the lower surface of the fifth impedance matching layer is the lower surface of the magnetic loss absorbing layer. The molding parameters are as follows: first, the pressure is increased to 2 MPa, then the pressure is increased to 3 MPa, first, the temperature is increased to 50° C., then the temperature is increased to 100° C., and hot pressing is performed at the above pressure and temperature for 3 hours.

[0082] (14) Preparation of the bearing layer: phenol-formaldehyde resin and quartz fiber were mixed in a mass ratio of 1:0.9, allowed to stand for 24 hours, and then separated and dried. The dried quartz fiber was placed in a metal mold with a cavity depth of 1.1 mm. After the mold was closed, it was placed on a flat hot press for molding to obtain a thermal insulation layer. The molding parameters were as follows: first, the pressure was increased to 5 MPa, then the pressure was increased to 10 MPa, first, the temperature was increased to 50 ° C, then the temperature was increased to 100 ° C, and hot pressed at the above pressure and temperature for 7 hours.

[0083] (2) A thin layer of phenol-formaldehyde resin is applied on the lower surface of the thermal insulation layer, the wave-transmitting layer, the magnetic loss absorbing layer, the upper and lower surfaces of the reflective layer, and the upper surface of the bearing layer. Then, the thermal insulation layer, the wave-transmitting layer, the magnetic loss absorbing layer, the reflective layer, and the bearing layer are compounded together in order. The whole is placed in a metal mold with a cavity depth of 8 mm. After the mold is closed, it is placed on a flat hot press for molding. After the mold is opened, a wave-absorbing structure composite material is obtained. The molding parameters are as follows: first, the pressure is increased to 2 MPa, then the pressure is increased to 3 MPa, first, the temperature is increased to 80°C, then the temperature is increased to 100°C, and hot pressing is carried out at the above pressure and temperature for 3 hours.

[0084] Example 3:

[0085] (1) Providing a reflective layer, cutting the carbon fiber cloth into a specified size to obtain the reflective layer;

[0086] (11) Preparation of thermal insulation layer: phenol-formaldehyde resin and quartz fiber were mixed in a mass ratio of 1:1.0, allowed to stand for 24 hours, separated and air-dried, and the air-dried quartz fiber was placed in a metal mold with a cavity depth of 3 mm. After the mold was closed, it was placed on a flat hot press for molding to obtain a thermal insulation layer; the molding parameters were: first, the pressure was increased to 5 MPa, then the pressure was increased to 10 MPa, first, the temperature was increased to 80 ° C, then the temperature was increased to 100 ° C, and hot pressing was performed at the above pressure and temperature for 7 hours;

[0087] (12) Preparation of a wave-transmitting layer: 10 sheets of quartz fiber cloth were cut into the same size as the reflective layer, cyanate ester resin was scraped onto the surface of the quartz fiber cloth, and then the quartz fiber cloth was stacked layer by layer. After drying, the quartz fiber cloth was placed in a metal mold with a cavity depth of 1.0 mm. After the mold was closed, it was placed on a flat hot press for molding. After the mold was opened, the wave-transmitting layer was obtained; the mass ratio of cyanate ester resin to quartz fiber cloth was 1:1.0; the molding parameters were: first, the pressure was increased to 5 MPa, then the pressure was increased to 10 MPa, first, the temperature was increased to 80°C, then the temperature was increased to 100°C, and hot pressing was performed at the above pressure and temperature for 7 h;

[0088] (13) Preparation of magnetic loss absorbing layer: carbonyl iron powder and aminophenol-formaldehyde resin were mixed in a mass ratio of 1:2.5, 1:1.5, 1:1.0, 1:0.7 and 1:0.4 respectively, and after standing for 24 hours, they were dried and placed in metal molds with cavity depths of 0.4 mm, 0.5 mm, 0.6 mm, 0.8 mm and 1.0 mm respectively. After the molds were closed, they were placed on a flat hot press for molding. After the molds were opened, magnetic impedance matching layers with thicknesses of 0.4 mm, 0.5 mm, 0.6 mm, 0.8 mm and 1.0 mm were obtained respectively; they were named as the first magnetic impedance matching layer, the second magnetic impedance matching layer, the third magnetic impedance matching layer, the fourth magnetic impedance matching layer and the fifth magnetic impedance matching layer respectively; molding parameters: first increase the pressure to 5 MPa, then increase the pressure to 8 MPa, first increase the temperature to 100 ° C, then increase the temperature to 120 ° C, and hot press for 5 hours at the above pressure and temperature;

[0089] First, a thin layer of phenol-formaldehyde resin is brushed on the lower surface of the first magnetic impedance matching layer, the upper and lower surfaces of the second, third, and fourth magnetic impedance matching layers, and the upper surface of the fifth magnetic impedance matching layer. Then, the magnetic impedance matching layers are compounded in the order of the first impedance matching layer, the second magnetic impedance matching layer, the third magnetic impedance matching layer, the fourth magnetic impedance matching layer, and the fifth magnetic impedance matching layer. The whole is placed in a metal mold with a cavity depth of 3.3 mm. After the mold is closed, it is placed on a flat hot press for molding. After the mold is opened, a magnetic loss absorbing layer is obtained. The upper surface of the first impedance matching layer is the upper surface of the magnetic loss absorbing layer, and the lower surface of the fifth impedance matching layer is the lower surface of the magnetic loss absorbing layer. The molding parameters are as follows: first, the pressure is increased to 2 MPa, then the pressure is increased to 3 MPa, first, the temperature is increased to 50° C., then the temperature is increased to 100° C., and hot pressing is performed at the above pressure and temperature for 3 hours.

[0090] (14) Preparation of the bearing layer: The phenol-formaldehyde resin and the quartz fiber were mixed in a mass ratio of 1:1.0, allowed to stand for 24 hours, and then separated and dried. The dried quartz fiber was placed in a metal mold with a cavity depth of 1.2 mm. After the mold was closed, it was placed on a flat hot press for molding to obtain a thermal insulation layer; the molding parameters were: first, the pressure was increased to 5 MPa, then the pressure was increased to 10 MPa, first, the temperature was increased to 50 ° C, then the temperature was increased to 100 ° C, and hot pressed at the above pressure and temperature for 7 hours;

[0091] (2) A thin layer of phenol-formaldehyde resin is applied on the lower surface of the thermal insulation layer, the wave-transmitting layer, the magnetic loss absorbing layer, the upper and lower surfaces of the reflective layer, and the upper surface of the bearing layer. The thermal insulation layer, the wave-transmitting layer, the magnetic loss absorbing layer, the reflective layer, and the bearing layer are then compounded together in order. The whole is placed in a metal mold with a cavity depth of 9 mm. After the mold is closed, it is placed on a flat hot press for molding. After the mold is opened, a wave-absorbing structure composite material is obtained. The molding parameters are as follows: first, the pressure is increased to 2 MPa, then the pressure is increased to 3 MPa, first, the temperature is increased to 80°C, then the temperature is increased to 100°C, and hot pressing is carried out at the above pressure and temperature for 3 hours.

[0092] Example 4:

[0093] Example 4 is basically the same as Example 1, except that: in step (13), a magnetic loss absorbing layer is prepared: carbonyl iron powder and aminophenol-formaldehyde resin are mixed in a mass ratio of 1:2.5, 1:2.0, 1:1.5, and 1:1, respectively. After standing for 24 hours, the mixture is soaked and dried and placed in metal molds with cavity depths of 0.4 mm, 0.6 mm, 0.8 mm, and 1.0 mm, respectively. After the molds are closed, they are placed on a flat hot press for molding. After the molds are opened, magnetic impedance matching layers with thicknesses of 0.4 mm, 0.6 mm, 0.8 mm, and 1.0 mm are obtained, respectively; they are named the first magnetic impedance matching layer, the second magnetic impedance matching layer, the third magnetic impedance matching layer, and the fourth magnetic impedance matching layer, respectively; the molding parameters are: first, the pressure is increased to 5 MPa, then the pressure is increased to 8 MPa, first, the temperature is increased to 100° C., then the temperature is increased to 120° C., and hot pressing is performed at the above pressure and temperature for 5 hours;

[0094] First, a thin layer of phenol-formaldehyde resin is brushed on the lower surface of the first magnetic impedance matching layer, the upper and lower surfaces of the second and third magnetic impedance matching layers, and the upper surface of the fourth magnetic impedance matching layer. Then, the magnetic impedance matching layers are compounded together in the order of the first impedance matching layer, the second magnetic impedance matching layer, and the third magnetic impedance matching layer. The whole is placed in a metal mold with a cavity depth of 2.8 mm. After the mold is closed, it is placed on a flat hot press for molding. After the mold is opened, a magnetic loss absorbing layer is obtained; wherein, the upper surface of the first impedance matching layer is the upper surface of the magnetic loss absorbing layer, and the lower surface of the fourth impedance matching layer is the lower surface of the magnetic loss absorbing layer; the molding parameters are as follows: first, the pressure is increased to 2 MPa, then the pressure is increased to 3 MPa, first, the temperature is increased to 50° C., then the temperature is increased to 100° C., and hot pressing is performed at the above pressure and temperature for 3 hours.

[0095] Example 5:

[0096] Example 5 is basically the same as Example 1, except that: in step (13), a magnetic loss absorbing layer is prepared: carbonyl iron powder and aminophenol-formaldehyde resin are mixed in a mass ratio of 1:0.3, 1:0.6, 1:0.9, 1:1.4, and 1:2.4, respectively, and after standing for 24 hours, they are placed in metal molds with cavity depths of 0.3 mm, 0.4 mm, 0.5 mm, 0.7 mm, and 0.9 mm, respectively, and after closing the molds, they are placed on a flat hot press for molding, and the mixture is opened. After molding, magneto-impedance matching layers with thicknesses of 0.3 mm, 0.4 mm, 0.5 mm, 0.7 mm, and 0.9 mm were obtained, respectively named the first magneto-impedance matching layer, the second magneto-impedance matching layer, the third magneto-impedance matching layer, the fourth magneto-impedance matching layer, and the fifth magneto-impedance matching layer. Molding parameters were as follows: first, the pressure was increased to 5 MPa, then the pressure was increased to 8 MPa, and the temperature was first increased to 100° C., then the temperature was increased to 120° C., and hot pressing was performed at the above pressure and temperature for 5 hours.

[0097] First, a thin layer of phenol-formaldehyde resin is brushed on the lower surface of the first magnetic impedance matching layer, the upper and lower surfaces of the second, third, and fourth magnetic impedance matching layers, and the upper surface of the fifth magnetic impedance matching layer. Then, the magnetic impedance matching layers are compounded together in the order of the first impedance matching layer, the second magnetic impedance matching layer, the third magnetic impedance matching layer, the fourth magnetic impedance matching layer, and the fifth magnetic impedance matching layer. The whole is placed in a metal mold with a cavity depth of 2.8 mm. After the mold is closed, it is placed on a flat hot press for molding. After the mold is opened, a magnetic loss absorbing layer is obtained; wherein, the upper surface of the first impedance matching layer is the upper surface of the magnetic loss absorbing layer, and the lower surface of the fifth impedance matching layer is the lower surface of the magnetic loss absorbing layer. The molding parameters are as follows: first, the pressure is increased to 2 MPa, then the pressure is increased to 3 MPa, first, the temperature is increased to 50° C., then the temperature is increased to 100° C., and hot pressing is performed at the above pressure and temperature for 3 hours.

[0098] Example 6:

[0099] Example 6 is basically the same as Example 5, except that: in step (13), the magnetic loss absorbing layer is prepared: carbonyl iron powder and aminophenol-formaldehyde resin are mixed in a mass ratio of 1:0.6, 1:0.6, 1:0.6, 1:0.6, and 1:0.6, respectively. After standing for 24 hours, the mixture is soaked and dried, and then placed in metal molds with cavity depths of 0.3 mm, 0.4 mm, 0.5 mm, 0.7 mm, and 0.9 mm, respectively. After the molds are closed, they are placed on a flat hot press for molding. After the mold is opened, magneto-impedance matching layers with thicknesses of 0.3 mm, 0.4 mm, 0.5 mm, 0.7 mm, and 0.9 mm are obtained respectively; they are named as the first magneto-impedance matching layer, the second magneto-impedance matching layer, the third magneto-impedance matching layer, the fourth magneto-impedance matching layer, and the fifth magneto-impedance matching layer respectively; the molding parameters are as follows: first, the pressure is increased to 5 MPa, then the pressure is increased to 8 MPa, first, the temperature is increased to 100°C, then the temperature is increased to 120°C, and hot pressing is carried out at the above pressure and temperature for 5 hours.

[0100] Example 7:

[0101] Example 7 is basically the same as Example 1, except that: in step (11), when preparing the thermal insulation layer, the phenol-formaldehyde resin and the quartz fiber are mixed in a mass ratio of 1:0.5, left to stand for 24 hours, split and dried, and the dried quartz fiber is placed in a metal mold with a cavity depth of 5 mm. After the mold is closed, it is placed on a flat hot press for molding to obtain the thermal insulation layer.

[0102] Example 8:

[0103] Example 8 is basically the same as Example 1, except that: in step (12), a wave-transmitting layer is prepared: 5 sheets of quartz fiber cloth are cut into the same size as the reflective layer, cyanate resin is respectively scraped on the surface of the quartz fiber cloth, and then the quartz fiber cloth is stacked layer by layer, and after drying, it is placed in a metal mold with a cavity depth of 0.5 mm. After the mold is closed, it is placed on a flat hot press for molding, and the wave-transmitting layer is obtained after the mold is opened; the mass ratio of cyanate resin to quartz fiber cloth is 1:0.5.

[0104] Comparative Example 1:

[0105] Comparative Example 1 is basically the same as Example 1, except that: in step (13), a magnetic loss absorbing layer is prepared: carbonyl iron powder and aminophenol-formaldehyde resin are mixed in mass ratios of 1:2.4, 1:1.4, 1:0.9, 1:0.6, and 1:0.3, respectively, and after standing for 24 hours, they are dried and placed in metal molds with cavity depths of 0.9 mm, 0.7 mm, 0.5 mm, 0.4 mm, and 0.3 mm, respectively. After the molds are closed, they are placed on a flat hot press for molding, and after the molds are opened, magnetic impedance matching layers with thicknesses of 0.9 mm, 0.7 mm, 0.5 mm, 0.4 mm, and 0.3 mm are obtained, respectively; they are named the first magnetic impedance matching layer, the second magnetic impedance matching layer, the third magnetic impedance matching layer, the fourth magnetic impedance matching layer, and the fifth magnetic impedance matching layer, respectively;

[0106] First, a thin layer of phenol-formaldehyde resin is brushed on the lower surface of the first magnetic impedance matching layer, the upper and lower surfaces of the second, third, and fourth magnetic impedance matching layers, and the upper surface of the fifth magnetic impedance matching layer. Then, the magnetic impedance matching layers are composited together in the order of the first impedance matching layer, the second magnetic impedance matching layer, the third magnetic impedance matching layer, the fourth magnetic impedance matching layer, and the fifth magnetic impedance matching layer. The whole is placed in a metal mold with a cavity depth of 2.8 mm. After the mold is closed, it is placed on a flat hot press for molding. After the mold is opened, a magnetic loss absorbing layer is obtained; wherein, the upper surface of the first impedance matching layer is the upper surface of the magnetic loss absorbing layer, and the lower surface of the fifth impedance matching layer is the lower surface of the magnetic loss absorbing layer.

[0107] Comparative Example 2:

[0108] Comparative Example 2 is basically the same as Comparative Example 1, except that: in step (13), a magnetic loss absorbing layer is prepared: carbonyl iron powder and aminophenol-formaldehyde resin are mixed in mass ratios of 1:2.4, 1:1.4, 1:0.9, 1:0.6, and 1:0.3, respectively, and after standing for 24 hours, they are dried and placed in metal molds with cavity depths of 0.5 mm, 0.5 mm, 0.5 mm, 0.5 mm, and 0.5 mm, respectively. After the molds are closed, they are placed on a flat hot press for molding, and after the molds are opened, magnetic impedance matching layers with thicknesses of 0.5 mm, 0.5 mm, 0.5 mm, 0.5 mm, and 0.5 mm are obtained, respectively; they are named as the first magnetic impedance matching layer, the second magnetic impedance matching layer, the third magnetic impedance matching layer, the fourth magnetic impedance matching layer, and the fifth magnetic impedance matching layer, respectively.

[0109] Comparative Example 3:

[0110] Comparative Example 3 is basically the same as Example 1, except that: in step (13), a magnetic loss absorbing layer is prepared: carbonyl iron powder and aminophenol-formaldehyde resin are mixed in a mass ratio of 1:4, 1:1.4, 1:1.4, 1:1.4, and 1:1.4, respectively, and after standing for 24 hours, they are dried and placed in metal molds with cavity depths of 0.5 mm, 0.5 mm, 0.5 mm, 0.5 mm, and 0.5 mm, respectively. After the molds are closed, they are placed on a flat hot press for molding, and after the molds are opened, magnetic impedance matching layers with thicknesses of 0.5 mm, 0.5 mm, 0.5 mm, 0.5 mm, and 0.5 mm are obtained, respectively; they are named as the first magnetic impedance matching layer, the second magnetic impedance matching layer, the third magnetic impedance matching layer, the fourth magnetic impedance matching layer, and the fifth magnetic impedance matching layer, respectively.

[0111] Comparative Example 4:

[0112] Comparative Example 4 is substantially the same as Example 1, except that in step (11), the thermal insulation layer is silica aerogel.

[0113] Comparative Example 5:

[0114] Comparative Example 5 is basically the same as Example 1, except that in step (12), the wave-transmitting layer is a glass fiber reinforced fiberglass plate.

[0115] Comparative Example 6:

[0116] Comparative Example 6 is basically the same as Example 1, except that: in step (13), when preparing the magnetic loss absorbing layer, the carbonyl iron powder is replaced by acetylene black, and the phenol-formaldehyde resin is replaced by epoxy resin.

[0117] Comparative Example 7 is basically the same as Example 1, except that: in step (2), a thin layer of phenol-formaldehyde resin is brushed on the lower surface of the thermal insulation layer, the wave-transmitting layer, the upper and lower surfaces of the magnetic loss absorbing layer and the reflective layer, and the upper surface of the bearing layer. Then, the thermal insulation layer, the reflective layer, the magnetic loss absorbing layer, the wave-transmitting layer and the bearing layer are compounded together in order, and the whole is placed in a metal mold with a cavity depth of 7 mm. After the mold is closed, it is placed on a flat hot press for molding, and after the mold is opened, the wave-absorbing structure composite material is obtained.

[0118] Comparative Example 8:

[0119] Comparative Example 8 is basically the same as Example 1, except that: in step (1) and step (2), the heat insulation layer and the load-bearing layer are removed, that is, the wave-absorbing structure composite material does not include the heat insulation layer and the load-bearing layer.

[0120] Comparative Example 9:

[0121] Comparative Example 9 is basically the same as Example 1, except that: in step (1) and step (2), the magnetic loss absorbing layer is removed, that is, the absorbing structure composite material does not include a magnetic loss absorbing layer.

[0122] Comparative Example 10:

[0123] Comparative Example 10 is basically the same as Example 1, except that: in step (1) and step (2), the reflective layer is removed, that is, the wave-absorbing structure composite material does not include a reflective layer.

[0124] The absorbing structural composite materials (abbreviated as absorbing materials) prepared in Examples 1 to 8 and Comparative Examples 1 to 10 were subjected to mechanical strength, temperature resistance and absorbing performance tests respectively. The test methods are as follows. The test structures are shown in Tables 1 and Figures 1 to 3 As shown;

[0125] Tensile strength test method: GB / T1447-2005 "Test method for tensile properties of fiber reinforced plastics";

[0126] Compression strength test method: GB / T1448-2005 "Test method for compression properties of fiber reinforced plastics";

[0127] Linear ablation rate test method: GJB328B-2018 "Ablation Test Method for Ablative Materials";

[0128] Thermal conductivity test method: GB / T3139-2005 "Test method for thermal conductivity of fiber reinforced plastics";

[0129] Radar absorbing performance test method: GJB2038A-2011 "Test method for reflectivity of radar absorbing materials".

[0130] Table 1

[0131]

[0132] As shown in Table 1, the absorbing materials prepared in Examples 1 to 3 of the present invention have a tensile strength of ≥30 MPa, a compressive strength of ≥100 MPa, a thermal conductivity of ≤0.6 w / m·K, and a linear ablation rate of ≤0.7 mm / s, and have excellent mechanical strength and high temperature resistance. Figures 3 to 6 It can be seen that the absorbing material prepared in the embodiment of the present invention has excellent absorbing performance. In the frequency band of 2 GHz to 18 GHz, the reflectivity of the absorbing material is lower than -10 dB, and can be lower than -15 dB at specific frequency points.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A wave-absorbing structural composite material, characterized in that: The invention comprises a heat-insulating layer, a wave-transmitting layer, a magnetic loss absorbing layer, a reflecting layer and a bearing layer arranged in sequence from top to bottom; the magnetic loss absorbing layer comprises a plurality of magnetic impedance matching layers, the thickness of which increases in sequence from the wave-transmitting layer to the reflecting layer; the heat-insulating layer and the bearing layer are both prepared by mixing phenolic resin and quartz fiber, drying them in the air, and then molding them; the mass ratio of the phenolic resin to the quartz fiber is 1: (0.8-1.0); the magnetic impedance matching layer is prepared by mixing phenolic resin and carbonyl iron powder. The method comprises the following steps: the mass ratio of the aminephenol-formaldehyde resin and the carbonyl iron powder in the magnetic impedance matching layer decreases from the wave-transmitting layer to the reflective layer; the mass ratio of the aminephenol-formaldehyde resin and the carbonyl iron powder is (0.3-2.5):1; the mass ratio of the aminephenol-formaldehyde resin and the carbonyl iron powder in adjacent magnetic impedance matching layers decreases by 0.3-1; the number of magnetic impedance matching layers is 4-6; the thickness of each magnetic impedance matching layer is 0.3-1 mm; and the thickness of adjacent magnetic impedance matching layers increases by 0.1-0.2 mm.

2. The wave-absorbing structural composite material according to claim 1, characterized in that: The thickness of the heat insulation layer is 2-3 mm; the thickness of the wave-transmitting layer is 0.8-1 mm; the thickness of the magnetic loss absorbing layer is 1.8-4.0 mm; and the thickness of the bearing layer is 1-1.2 mm.

3. A method for preparing a composite material of an absorbing structure according to any one of claims 1 to 2, characterized in that: The preparation method comprises the following steps: (1) providing a reflective layer, and preparing a heat-insulating layer, a wave-transmitting layer, a magnetic impedance matching layer of different thicknesses, and a bearing layer respectively; compounding the magnetic impedance matching layer in a manner of increasing thickness from top to bottom, and obtaining a magnetic loss absorbing layer after molding; the heat-insulating layer and the bearing layer are both prepared by mixing phenolic resin and quartz fiber, drying them in the air, and then molding them; the mass ratio of the phenolic resin to the quartz fiber is 1:(0.8-1.0); in each magnetic impedance matching layer, the mass ratio of the phenolic resin to the carbonyl iron powder is (0.3-2.5):1, and the mass ratio of the phenolic resin to the carbonyl iron powder in adjacent magnetic impedance matching layers decreases by 0.3-1; (2) The heat insulation layer, the wave-transmitting layer, the magnetic loss absorbing layer, the reflective layer and the bearing layer are compounded in sequence from top to bottom, and molded to obtain the wave-absorbing structure composite material; wherein, in the magnetic loss absorbing layer, one side of the magnetic impedance matching layer having the largest thickness is in contact with one side of the reflective layer; and during the molding operation, step-by-step pressure increase and / or step-by-step temperature increase are performed.

4. The preparation method according to claim 3, characterized in that In step (1): The preparation method of the wave-transmitting layer is as follows: cyanate resin is coated on the upper and lower surfaces of quartz fiber cloth, and after drying, the wave-transmitting layer is prepared by molding, wherein the number of layers of the quartz fiber cloth is 8 to 10.

5. The preparation method according to claim 4, characterized in that In the wave-transmitting layer, the mass ratio of the cyanate resin to the quartz fiber cloth is 1:(0.8-1.0).

6. The preparation method according to claim 3, characterized in that In step (1): The preparation method of the magnetic impedance matching layer is as follows: amine phenolic resin and carbonyl iron powder are mixed in different proportions, and then dried and molded to prepare magnetic impedance matching layers of different thicknesses; wherein the mass ratio of the amine phenolic resin to the carbonyl iron powder decreases as the thickness of the magnetic impedance matching layer increases.

7. The preparation method according to claim 6, characterized in that The thickness of each magnetic impedance matching layer is 0.3 mm to 1 mm; the thickness of adjacent magnetic impedance matching layers increases by 0.1 mm to 0.2 mm.

8. The preparation method according to claim 3, characterized in that The reflective layer is made of carbon fiber cloth.

9. The preparation method according to any one of claims 3 to 8, characterized in that The molding pressure is 2-20 MPa, the temperature is 80-180° C., and the time is 3-9 hours.

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