A method for preparing microwave absorbing prepreg based on reducing the deformation of co-cured panels

Abstract

The present invention relates to the technical field of composite material forming, and in particular to a method for preparing an absorbing prepreg based on reducing the deformation of a co-cured panel, comprising the following steps: preparing an absorbing resin, taking part of the absorbing resin and unfolding it into two groups of absorbing film units with the same surface density and compounding them with a transparent fiber to obtain an absorbing prepreg; co-curing the absorbing prepreg with a matrix prepreg into a composite panel I; designing the surface density ratio of the two groups of absorbing films according to the deformation of the composite panel I and the average vertical reflectivity in the X-band, and taking part of the absorbing resin and unfolding it into two groups of absorbing film units with different surface densities and a transparent fiber to obtain an absorbing prepreg based on the surface density ratio; and co-curing the final absorbing prepreg with a matrix prepreg into a composite panel. The technical solution can make the absorbing prepreg have non-uniform deformation, resist the deformation of the co-cured panel, and basically do not affect the stealth performance, greatly reduce the deformation performance of the co-cured parts, and meet the assembly requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material forming, and in particular to a method for preparing a wave-absorbing prepreg based on reducing the deformation of a co-cured plate. Background Art

[0002] Compared with stealth coating, absorbing prepreg has excellent absorbing performance and process performance, and is very likely to replace stealth coating as a new stealth material, which is an important direction for the development of thin-layer absorbing materials in the future. Its characteristic is that absorbing prepreg can be co-cured with matrix prepreg, but the resin system and fiber system of matrix prepreg are different from those of absorbing prepreg. Therefore, during the co-curing process, due to the different thermal expansion coefficients of absorbing prepreg and matrix prepreg, the deformation of the panel is greatly increased, which eventually causes serious deformation of the parts, affecting the subsequent assembly and use.

[0003] Conventional prior art, such as the Chinese patent document with publication number CN115742474A, discloses a low curing deformation absorbing layer plate and its preparation method, which specifically discloses: a low modulus absorbing adhesive film is prepared by compounding a resin matrix, an absorbent, an additive and low modulus small particles; a low modulus glass fiber prepreg is prepared by compounding glass fiber, a resin matrix and low modulus small particles; a carbon fiber prepreg, a low modulus absorbing adhesive film and a low modulus glass fiber prepreg are sequentially laid on the surface of a molding tool, and co-curing molding is performed to obtain a low curing deformation absorbing layer plate. This prior art can significantly reduce the deformation of the absorbing layer plate during molding due to the introduction of low modulus small particles and the use of co-curing molding. The defect of the aforementioned prior art is that the addition of a flexible resin to reduce the deformation of the plate will cause the glass transition temperature of the prepreg to be greatly reduced, thereby reducing the use temperature of the prepreg. Summary of the invention

[0004] In view of the shortcomings of the above-mentioned prior art, the present invention discloses a method for preparing an absorbing prepreg based on reducing the deformation of a co-cured panel. The method adopts a method of observing the deformation of a homogeneous absorbing prepreg and then designing the absorbing resin content on both sides of the absorbing prepreg to make it a non-homogeneous material, so that the absorbing prepreg has non-uniform deformation, thereby resisting the deformation trend of the co-cured panel and finally reducing the overall deformability of the prepared co-cured panel. The details are as follows:

[0005] A method for preparing an absorbing prepreg based on reducing the deformation of a co-cured panel comprises the following steps:

[0006] S1, uniformly mixing the absorbent and the resin matrix to obtain a microwave absorbing resin;

[0007] S2, first take part of the absorbing resin and unfold it into two groups of absorbing film units with the same surface density;

[0008] S3, attaching two groups of absorbing adhesive film units to both sides of the wave-transmitting fiber respectively, and compounding them by hot-melt method to obtain absorbing prepreg;

[0009] S4, laying the absorbing prepreg along the aerodynamic surface to a target thickness, laying the selected matrix prepreg on the laid absorbing prepreg, and then co-curing to form a composite plate member I of the absorbing prepreg and the matrix prepreg;

[0010] S5, detecting the deformation Q of the composite plate I and the average vertical reflectivity of the composite plate I in the X-band;

[0011] S6, under the condition that the average vertical reflectivity of the composite panel of the product in the X-band is stable, the surface density ratio of the two groups of absorbing films is designed according to the deformation amount Q;

[0012] S7, taking part of the absorbing resin and spreading it into two groups of absorbing film units with different surface densities according to the surface density ratio designed in step S6;

[0013] S8, repeating step S3 to obtain a wave-absorbing prepreg; wherein the wave-absorbing film surface density of the non-aerodynamic surface of the wave-absorbing prepreg is less than the wave-absorbing film surface density of the aerodynamic surface;

[0014] S9, repeating step S4 to co-curing the absorbing prepreg and the matrix prepreg into a composite panel product.

[0015] Preferably, in step S1, the absorbent is one of carbon-based, iron-based, and dielectric-based absorbents, or a composite absorbent of any two or more thereof.

[0016] Preferably, in step S1, the mass fraction of the absorbent to the absorbing resin is 50-90 wt %.

[0017] Preferably, in step S1, the resin matrix is ​​one of epoxy resin, bismaleimide and polyimide, or a composite resin of any two or more thereof.

[0018] Preferably, in step S3 and step S8, the weight percentage of the absorbing resin in the absorbing prepreg is 80-98 wt %.

[0019] Preferably, in step S3, the wave-transmitting fiber is one of glass fiber, quartz fiber, aramid fiber, polyimide fiber, or a composite fiber of any two or more thereof.

[0020] Preferably, in step S4, the target thickness of the absorbing prepreg stacking is 0.2-4 mm.

[0021] Preferably, in step S4, the matrix prepreg is one of carbon fiber prepreg, aramid fiber prepreg and glass fiber prepreg, or a composite prepreg of any two or more thereof.

[0022] Preferably, in step S4, the paving thickness of the matrix prepreg is 0.5-10 mm.

[0023] Beneficial technical effects brought by the present invention:

[0024] The present technical solution proposes a method for preparing an absorbing prepreg based on reducing the deformation of a co-cured panel. When the absorbing resin contents on both sides of the absorbing prepreg are inconsistent, the absorbing resin will shrink toward the side with a larger mass of the absorbing resin during the curing process due to the presence of a large amount of absorbent and resin matrix with high hardness in the absorbing resin. Based on this characteristic, the mass of the absorbing resin on both sides of the absorbing prepreg is designed to resist the deformation caused by the originally homogeneous material. First, an absorbing prepreg with uniform surface density of absorbing resin on both sides of a transparent fiber is prepared, and then co-cured with a matrix prepreg of a specified thickness, and the deformation of the co-cured panel is observed. According to the deformation size, the ratio of the surface density of the absorbing resin on both sides of the absorbing prepreg is designed. In the finally obtained absorbing prepreg, there is a difference in the surface density of the absorbing film units on both sides of the transparent fiber, so that the absorbing prepreg can resist the deformation of the co-cured panel without basically affecting the stealth performance, greatly reducing the deformation performance of the co-cured parts and meeting the assembly requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the basic implementation flow chart of this technical solution. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0027] Therefore, the following detailed description of the invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Example 1

[0029] This embodiment discloses a method for preparing a wave absorbing prepreg based on reducing the deformation of a co-cured plate, as a preferred embodiment of the present invention. Figure 1 As shown, the following steps are included:

[0030] S1, uniformly mixing the absorbent and the resin matrix to obtain the absorbing resin.

[0031] S2, first take part of the absorbing resin and expand it into two groups of absorbing film units with the same surface density. Each group of absorbing film units contains one or more layers of absorbing film, the number of absorbing film layers in the two groups of absorbing film units is the same, and the surface density of all layers of absorbing film is the same.

[0032] S3, attaching two groups of absorbing adhesive film units to both sides of the wave-transmitting fiber respectively, and compounding them by hot-melt method to obtain absorbing prepreg.

[0033] S4, stacking the absorbing prepreg along the aerodynamic surface to a target thickness, laying the selected matrix prepreg on the stacked absorbing prepreg, and then co-curing to form a composite plate I of the absorbing prepreg and the matrix prepreg. The composite plate I is an intermediate product of the technical solution, and is mainly used as a basis for adjusting the surface density ratio of the two groups of absorbing adhesive films.

[0034] S5, detecting the deformation Q of the composite plate I and the average vertical reflectivity of the composite plate I in the X-band.

[0035] S6. Considering the stability of the mean vertical reflectivity of the composite panel in the X-band, design the surface density ratio of the two groups of absorbing films according to the deformation amount Q. The so-called consideration of the stability of the mean vertical reflectivity of the composite panel in the X-band means that the mean vertical reflectivity of the final composite panel in the X-band does not change much compared with the composite panel I. In addition, the surface density ratio of the two groups of absorbing films designed according to the deformation amount Q can be adjusted multiple times. After each adjustment, a composite panel I is re-prepared in accordance with steps S7, S8 and S4, and then the composite panel I is used as the basis for adjusting the surface density ratio of the two groups of absorbing films until a suitable surface density ratio is obtained.

[0036] S7, according to the surface density ratio designed in step S6, take part of the absorbing resin and expand it into two groups of absorbing film units with different surface densities. Each group of absorbing film units contains one or more absorbing films, and the number of absorbing film layers in the two groups of absorbing film units is the same or different. Under the condition that the number of absorbing film layers in the two groups of absorbing film units is the same, the surface densities of the absorbing films in different layers are different or not completely the same; under the condition that the number of absorbing film layers in the two groups of absorbing film units is different, the surface densities of the absorbing films in different layers are the same, different or not completely the same.

[0037] S8, repeating step S3 to obtain a radar absorbing prepreg; wherein the radar absorbing film surface density of the non-aerodynamic surface of the radar absorbing prepreg is smaller than the radar absorbing film surface density of the aerodynamic surface.

[0038] S9, repeating step S4 to co-curing the absorbing prepreg and the matrix prepreg into a composite panel product.

[0039] The surface density of the absorbing resin is a physical quantity that is closely related to factors such as coating thickness, material composition, and preparation process. It can be seen that as the coating thickness increases, the surface density of the coating will increase. It can be concluded that as the thickness of the absorbing film increases, its surface density will also increase.

[0040] Based on this, the principle of the present technical solution is: when the absorbing resin content on both sides of the absorbing prepreg is inconsistent, since the absorbing resin contains a large amount of absorbents with high hardness and resin matrix, it will shrink toward the side with larger mass of the absorbing resin during the curing process. Therefore, the present technical solution uses this characteristic to design the mass of the absorbing resin on both sides of the absorbing prepreg, so that it can resist the deformation of the originally homogeneous material. Therefore, the present technical solution first prepares an absorbing prepreg with absorbing resin of uniform surface density on both sides of the wave-transmitting fiber, and then co-cures it with a matrix prepreg of a specified thickness, observes the deformation of the co-cured panel (composite panel I), and designs the ratio of the surface density of the absorbing resin on both sides of the absorbing prepreg according to the deformation size, so that it can resist the deformation of the co-cured panel while basically not affecting the stealth performance (average vertical reflectivity in the X-band). In the absorbing prepreg finally obtained, there is a difference in the surface density of the absorbing film units on both sides of the wave-transmitting fiber, that is, the ratio of the non-aerodynamic surface density to the aerodynamic surface density is .

[0041] Example 2

[0042] This embodiment discloses a method for preparing an absorbing prepreg based on reducing the deformation of a co-cured plate. As a preferred embodiment of the present invention, based on Example 1, in step S1, the absorbent is one of carbon, iron, and dielectric systems, or a composite absorbent of any two or more thereof. The absorbent accounts for 50 to 90 wt% of the mass of the absorbing resin, and the mutual matching of different types of absorbers is mainly used to improve the absorbing performance of the absorbing prepreg. Furthermore, in the steps S3 and S8, the absorbing resin accounts for 80 to 98 wt% of the mass of the absorbing prepreg.

[0043] Example 3

[0044] This embodiment discloses a method for preparing an absorbing prepreg based on reducing the deformation of a co-cured plate. As a preferred embodiment of the present invention, based on Embodiment 1 or 2, in step S1, the resin matrix is ​​one of epoxy resin, bismaleimide and polyimide, or a composite resin of any two or more thereof. The selection of the resin matrix takes into account the use temperature and the process performance of the absorbing prepreg preparation.

[0045] Example 4

[0046] This embodiment discloses a method for preparing a wave-absorbing prepreg based on reducing the deformation of a co-cured plate. As a preferred embodiment of the present invention, based on Embodiment 1, 2 or 3, in step S3, the wave-transmitting fiber is one of glass fiber, quartz fiber, aramid fiber, polyimide fiber, or a composite fiber of any two or more thereof. The fiber used in the wave-absorbing prepreg should have excellent wave-transmitting properties, so that electromagnetic waves enter the inside of the wave-absorbing prepreg and are lost.

[0047] Example 5

[0048] This embodiment discloses a method for preparing an absorbing prepreg based on reducing the deformation of a co-cured panel. As a preferred embodiment of the present invention, based on Embodiment 1, 2, 3 or 4, in step S4, the stacking thickness of the absorbing prepreg is determined according to the type of absorbent used and the absorbent content. Specifically, the target thickness of the absorbing prepreg stacking is 0.2-4 mm. By adjusting the use thickness (target thickness) of the absorbing prepreg, the co-cured panel can absorb electromagnetic waves within the required band and have the best absorbing performance.

[0049] Example 6

[0050] This embodiment discloses a method for preparing an absorbing prepreg based on reducing the deformation of a co-cured panel. As a preferred embodiment of the present invention, based on Embodiments 1, 2, 3, 4 or 5, in step S4, the matrix prepreg is one of carbon fiber prepreg, aramid fiber prepreg and glass fiber prepreg, or a composite prepreg of any two or more thereof. Furthermore, the paving thickness of the matrix prepreg is 0.5 to 10 mm. The thickness ratio of the matrix prepreg can be increased by adjusting the thickness ratio of the matrix prepreg to the absorbing prepreg, and the deformation of the co-cured panel can be further reduced.

[0051] Example 7

[0052] This embodiment discloses a method for preparing an absorbing prepreg based on reducing the deformation of a co-cured panel, as a preferred embodiment of the present invention, that is, based on Embodiments 1, 2, 3, 4, 5 or 6, the surface density, the thickness of the matrix prepreg and the absorbent content are used as variables to prepare co-cured products. The details are as follows:

[0053] (i) Add 70% carbonyl iron to bismaleimide resin to obtain absorbing resin. Prepare the absorbing resin into absorbing film, and compound the absorbing film with aramid fiber to obtain absorbing prepreg. The ratio of the surface density of the absorbing resin on the non-aerodynamic surface of the absorbing prepreg to the surface density of the absorbing resin on the aerodynamic surface is 1:1. Lay 1.0mm absorbing prepreg along the aerodynamic surface, lay 3.0mm carbon fiber prepreg on the laid absorbing prepreg, and bag and package it for co-curing to obtain a 300mm*300mm co-cured board. Turn the absorbing prepreg of the co-cured board upside down on the table. The maximum distance between the absorbing prepreg and the table is measured to be 12.7mm. The average vertical reflectivity of the co-cured board in the X-band is -12.5dB.

[0054] (ii) Add 70% carbonyl iron to bismaleimide resin to obtain absorbing resin. Prepare the absorbing resin into absorbing film, and compound the absorbing film with aramid fiber to obtain absorbing prepreg. The ratio of the surface density of the absorbing resin on the non-aerodynamic surface of the absorbing prepreg to the surface density of the absorbing resin on the aerodynamic surface is 1:2. Lay 1.0mm absorbing prepreg along the aerodynamic surface, lay 3.0mm carbon fiber prepreg on the laid absorbing prepreg, and bag and package it for co-curing to obtain a 300mm*300mm co-cured panel. Turn the absorbing prepreg of the co-cured panel downward on the table, and the maximum distance between the absorbing prepreg and the table is measured to be 4.1mm. The average vertical reflectivity of the co-cured panel in the X-band is -12.8dB.

[0055] (III) Add 70% carbonyl iron to bismaleimide resin to obtain absorbing resin. Prepare the absorbing resin into absorbing film, and compound the absorbing film with aramid fiber to obtain absorbing prepreg. The ratio of the surface density of the absorbing resin on the non-aerodynamic surface of the absorbing prepreg to the surface density of the absorbing resin on the aerodynamic surface is 1:8. Lay 1.0mm absorbing prepreg along the aerodynamic surface, lay 3.0mm carbon fiber prepreg on the laid absorbing prepreg, and bag and package it for co-curing to obtain a 300mm*300mm co-cured panel. Turn the absorbing prepreg of the co-cured panel downward on the table, and measure the maximum distance between the absorbing prepreg and the table to be 2.6mm. The average vertical reflectivity of the co-cured panel in the X-band is -13.2dB.

[0056] (IV) Add 70% carbonyl iron to bismaleimide resin to obtain absorbing resin. Prepare the absorbing resin into absorbing film, and compound the absorbing film with aramid fiber to obtain absorbing prepreg, and the ratio of the surface density of the absorbing resin on the non-aerodynamic surface of the absorbing prepreg to the surface density of the absorbing resin on the aerodynamic surface is 1:2. Lay 1.0mm absorbing prepreg along the aerodynamic surface, lay 3.8mm carbon fiber prepreg on the laid absorbing prepreg, bag and package it, and co-curing it to obtain a 300mm*300mm co-cured board. Turn the absorbing prepreg of the co-cured board upside down on the table, and measure that the maximum distance between the absorbing prepreg and the table is 3.6mm. The average vertical reflectivity of the co-cured board in the X-band is -12.8dB.

[0057] (V) Add 60% carbonyl iron to bismaleimide resin to obtain absorbing resin. Prepare the absorbing resin into absorbing film, and compound the absorbing film with aramid fiber to obtain absorbing prepreg, the ratio of the surface density of the absorbing resin on the non-aerodynamic surface of the absorbing prepreg to the surface density of the absorbing resin on the aerodynamic surface is 1:2. Lay 1.0mm absorbing prepreg along the aerodynamic surface, lay 3.0mm carbon fiber prepreg on the laid absorbing prepreg, bag and package it, and co-curing it to obtain a 300mm*300mm co-cured board. Turn the absorbing prepreg of the co-cured board upside down on the table, and measure the maximum distance between the absorbing prepreg and the table to be 4.8mm. The average vertical reflectivity of the co-cured board in the X-band is -7.9dB.

[0058] In this way, the following list of factors affecting the deformation of the cured plate is obtained:

[0059]

[0060] As can be seen from the table above, the factors that affect the deformation of the co-cured panel include the absorbent content, the surface density ratio of the absorbing resin on both sides of the wave-transmitting fiber, and the thickness of the matrix prepreg. If the absorbent content is changed, the average vertical reflectivity in the X-band will change significantly. Therefore, without considering changing the absorbent content, the surface density ratio of the absorbing resin on both sides of the wave-transmitting fiber and the thickness of the matrix prepreg can be considered. This technical solution is a study on changing the surface density ratio of the absorbing resin on both sides of the wave-transmitting fiber. It can be seen from the tests (i), (ii) and (iii) that as the surface density ratio of the absorbing film on the non-aerodynamic surface and the aerodynamic surface of the absorbing prepreg decreases, the deformation of the co-cured panel gradually decreases, and will not cause a significant change in the average vertical reflectivity in the X-band.

Claims

1. A method for preparing an absorbing prepreg based on reducing the deformation of a co-cured panel, characterized in that: The following steps are involved: S1, uniformly mixing the absorbent and the resin matrix to obtain a microwave absorbing resin; S2, first take part of the absorbing resin and unfold it into two groups of absorbing film units with the same surface density; S3, attaching two groups of absorbing adhesive film units to both sides of the wave-transmitting fiber respectively, and compounding them by hot-melt method to obtain absorbing prepreg; S4, laying the absorbing prepreg along the aerodynamic surface to a target thickness, laying the selected matrix prepreg on the laid absorbing prepreg, and then co-curing to form a composite plate member I of the absorbing prepreg and the matrix prepreg; S5, detecting the deformation Q of the composite plate I and the average vertical reflectivity of the composite plate I in the X-band; S6, under the condition that the average vertical reflectivity of the composite panel of the product in the X-band is stable, the surface density ratio of the two groups of absorbing films is designed according to the deformation amount Q; S7, taking part of the absorbing resin and spreading it into two groups of absorbing film units with different surface densities according to the surface density ratio designed in step S6; S8, repeating step S3 to obtain a wave-absorbing prepreg; wherein the wave-absorbing film surface density of the non-aerodynamic surface of the wave-absorbing prepreg is less than the wave-absorbing film surface density of the aerodynamic surface; S9, repeating step S4 to co-curing the absorbing prepreg and the matrix prepreg into a composite panel product.

2. A method for preparing an absorbing prepreg based on reducing the deformation of a co-cured panel as claimed in claim 1, characterized in that: In the step S1, the absorbent is one of carbon-based, iron-based, and dielectric-based absorbents, or a composite absorbent of any two or more thereof.

3. A method for preparing an absorbing prepreg based on reducing the deformation of a co-cured panel as claimed in claim 1, characterized in that: In the step S1, the absorbent accounts for 50-90 wt % of the absorbing resin.

4. A method for preparing an absorbing prepreg based on reducing the deformation of a co-cured panel as claimed in claim 1, characterized in that: In the step S1, the resin matrix is ​​one of epoxy resin, bismaleimide and polyimide, or a composite resin of any two or more thereof.

5. A method for preparing an absorbing prepreg based on reducing the deformation of a co-cured panel as claimed in claim 1, characterized in that: In the step S3 and step S8, the absorbing resin accounts for 80-98 wt % of the absorbing prepreg.

6. A method for preparing an absorbing prepreg based on reducing the deformation of a co-cured panel as claimed in claim 1, characterized in that: In the step S3, the wave-transmitting fiber is one of glass fiber, quartz fiber, aramid fiber, polyimide fiber, or a composite fiber of any two or more thereof.

7. A method for preparing an absorbing prepreg based on reducing the deformation of a co-cured panel as claimed in claim 1, characterized in that: In step S4, the target thickness of the absorbing prepreg is 0.2-4 mm.

8. A method for preparing an absorbing prepreg based on reducing the deformation of a co-cured panel as claimed in claim 1, characterized in that: In step S4, the matrix prepreg is one of carbon fiber prepreg, aramid fiber prepreg and glass fiber prepreg, or a composite prepreg of any two or more thereof.

9. A method for preparing an absorbing prepreg based on reducing the deformation of a co-cured panel as claimed in claim 1, characterized in that: In the step S4, the paving thickness of the matrix prepreg is 0.5-10 mm.

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