A wave absorbing layer with low curing deformation and a preparation method thereof

Abstract

The present invention discloses a wave-absorbing layer plate with low curing deformation and a preparation method thereof, belonging to the technical field of structure / stealth composite materials, wherein a low modulus wave-absorbing adhesive film is prepared by compounding a resin matrix, a wave-absorbing agent, an auxiliary agent 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 wave-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 wave-absorbing layer plate with low curing deformation. Due to the introduction of low modulus small particles and the use of co-curing molding, the present invention can significantly reduce the deformation of the wave-absorbing layer plate during molding.

Description

Technical Field

[0001] The present application belongs to the technical field of structural / stealth composite materials, and relates to a wave-absorbing layer plate with low curing deformation and a preparation method thereof. Background Art

[0002] With the continuous development of military detection technology, the battlefield survivability of military targets has been greatly challenged, and an urgent need for stealth performance has also arisen. Absorbing materials reduce radar echoes by dissipating the electromagnetic waves emitted by radar, thereby reducing the probability of targets being discovered by radar. Absorbing interlayer materials, absorbing coatings, absorbing patches and absorbing layers are the main absorbing structures used today and are widely used in various fields.

[0003] The absorbing layer has the characteristics of thin thickness, wide absorbing frequency band, and strong bonding with the base material, and can effectively replace absorbing coatings and absorbing patches. However, as a structural / stealth composite material, the carbon fiber skin is generally a symmetrical and balanced layer, and as a structural functional layer of the absorbing layer, this leads to an asymmetric overall layer structure of the absorbing layer. At the same time, the carbon fiber skin and the absorbing functional layer have different thermal expansion coefficients, resulting in different curing shrinkage capabilities of the two. After curing, a large curing stress will be generated, which will lead to a large deformation of the absorbing layer after curing, affecting the application effect. Summary of the invention

[0004] The purpose of the present invention is to overcome the problem of large deformation of the above-mentioned absorbing layer after curing, and to provide an absorbing layer with low curing deformation and a preparation method thereof. After the absorbing layer is cured and formed, only a small curing deformation occurs, and it can have absorbing performance without changing the original carbon fiber skin layer.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing a wave-absorbing layer with low curing deformation comprises the following steps:

[0007] 1) Weighing a resin matrix, an absorbent, an additive and low modulus small particles according to a mass ratio of (10-25):(35-65):(1-2):(4-8), wherein the low modulus small particles are micron-sized silicone rubber particles, and compounding them to prepare a low modulus absorbing adhesive film;

[0008] 2) Weighing glass fiber, resin matrix and low modulus small particles according to the mass ratio of (19-21):(28-30):1, wherein the low modulus small particles are micron-sized silicone rubber particles, and compounding to prepare a low modulus glass fiber prepreg;

[0009] 3) Symmetrically and evenly layering the carbon fiber prepreg on the surface of the molding tool, and then curing it separately or not separately;

[0010] 4) Laying a low modulus absorbing adhesive film on the surface of the carbon fiber prepreg;

[0011] 5) Laying low modulus glass fiber prepreg on the surface of the low modulus absorbing film;

[0012] 6) Continue to lay an isolation film and a breathable felt on the surface of the low modulus glass fiber prepreg, and then make a vacuum bag, perform co-curing molding in the vacuum bag, and then cool and demold to obtain an absorbing layer plate with low curing deformation.

[0013] Preferably, the resin matrix in steps 1) to 2) is selected from at least one of cyanate resin, epoxy resin, polyurethane resin, phenolic resin, polyimide resin and bismaleimide resin.

[0014] Preferably, the carbon fiber prepreg is a commercially available finished product, which is composited from carbon fiber cloth and a resin matrix.

[0015] Preferably, the absorber is selected from at least one of ferrite powder, carbonyl iron powder, conductive carbon black, carbon fiber, silicon carbide fiber, carbon nanotube and graphene.

[0016] Preferably, the auxiliary agent is one of polyamine, aromatic polyamine, organic acid and acid anhydride.

[0017] Preferably, the particle size of the silicone rubber particles is 10 to 200 μm.

[0018] Preferably, in step 2), the low modulus small particles are firstly mixed with the resin matrix and then the glass fibers are added and rolled to prepare a low modulus glass fiber prepreg.

[0019] Preferably, the thickness of the carbon fiber prepreg is 0.5-5 mm, the thickness of the low modulus wave-absorbing adhesive film is 0.1-4.5 mm, and the thickness of the low modulus glass fiber prepreg is 0.5-2 mm.

[0020] Preferably, the co-curing conditions are: pressure 0.4-0.5 MPa, heating at 130° C. and keeping warm for 2 hours.

[0021] Preferably, a demoulding material is brushed on the surface of the molding tool in advance and dried.

[0022] A wave absorbing layer plate with low curing deformation is prepared by the above method.

[0023] The beneficial effects achieved by the present invention are as follows:

[0024] 1. The structure of the wave absorbing layer prepared by the method of the present invention is: from bottom to top, carbon fiber prepreg, low modulus wave absorbing adhesive film and low modulus glass fiber prepreg, wherein the carbon fiber prepreg provides structural function for the entire wave absorbing layer and also serves as a reflective layer of the wave absorbing functional layer; the low modulus wave absorbing adhesive film serves as an absorbing loss layer of the wave absorbing functional layer, providing the wave absorbing layer with wave absorbing performance; the low modulus glass fiber prepreg serves as an impedance matching layer of the wave absorbing functional layer, which can improve the wave absorbing characteristics of the wave absorbing layer. The low modulus wave absorbing adhesive film and the low modulus glass fiber prepreg can obtain different wave absorbing properties by adjusting the layer structure.

[0025] 2. In the method proposed by the present invention, the carbon fiber prepreg has a symmetrical and balanced layer structure, which can be cured and formed separately. In this way, the carbon fiber skin after forming will not be deformed, which is convenient for direct replacement and application with the existing structure, and also convenient for structural simulation calculation and curing deformation analysis of the entire product; then the absorbing film and glass fiber prepreg are directly laid on the surface of the cured carbon fiber skin, and then co-bonded and cured. The carbon fiber prepreg can also not be cured separately, but after the carbon fiber prepreg, low modulus absorbing film and low modulus glass fiber prepreg are laid, they are co-cured and formed together, which can simplify the curing procedure, reduce one curing process, and save human resources and costs.

[0026] 3. In the method proposed by the present invention, the absorbing film uses a low modulus absorbing film, which is added with low modulus small particles, which can effectively reduce the elastic modulus of the absorbing film itself, thereby ensuring a low curing deformation. Moreover, the addition amount of the low modulus small particles should not be too high or too low. If the addition amount is too low, the elastic modulus improvement effect is weak and the curing deformation still exists; and if the addition amount is too high, the absorbing performance of the absorbing film is adversely affected.

[0027] 4. In the method proposed by the present invention, the reason why the low modulus absorbing film is co-cured is that the absorbing film is a low modulus absorbing film. After curing, it has a low elastic modulus and weak deformation ability. Therefore, it can be co-cured with carbon fiber prepreg. After the overall curing, no large curing stress will be generated, and the deformation curing degree is small.

[0028] 5. In the method proposed by the present invention, the glass fiber prepreg is a low-modulus glass fiber prepreg, to which low-modulus small particles are added. The low-modulus small particles can effectively reduce the elastic modulus of the absorbing film itself, and compared with the general prepreg, it has a lower curing deformation ability.

[0029] 6. In the method proposed in the present invention, the reason why low modulus glass fiber prepreg is co-cured is that the glass fiber prepreg is a low modulus glass fiber prepreg. After curing, it has a low elastic modulus and weak deformation ability. Therefore, it can be co-cured with carbon fiber prepreg and low modulus absorbing film. After the overall curing, no large curing stress will be generated, and the deformation curing degree is small.

[0030] 7. The method proposed in the present invention can prepare an absorbing layer plate with low curing deformation, which can be a flat product or a product with a curvature change, and the product size is not restricted by the absorbing layer plate.

[0031] 8. The traditional absorbing layer structure represented by carbon fiber skin and absorbing film is an asymmetric layer structure, and the thermal expansion coefficients of the carbon fiber skin and the absorbing film do not match, which will cause the absorbing layer to produce large deformation after co-curing, affecting engineering applications. In the method proposed by the present invention, the introduction of low modulus small particles into the absorbing film can reduce the thermal expansion coefficient of the absorbing film, so that the carbon fiber skin and the absorbing film have similar thermal expansion coefficients. After co-curing, the absorbing layer does not produce or only produces a small deformation; by controlling the addition amount of low modulus small particles, the deformation degree of the absorbing layer after co-curing can be effectively controlled to obtain the desired deformation, greatly improving the engineering application of the absorbing layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic structural diagram of the wave-absorbing layer plate with low curing deformation of the present invention.

[0033] In the figure: 1- low modulus glass fiber prepreg, 2- low modulus absorbing film, 3 is carbon fiber skin. DETAILED DESCRIPTION

[0034] In order to make the above features and advantages of the present invention more obvious and easy to understand, embodiments are given below and described in detail with reference to the accompanying drawings.

[0035] Example 1

[0036] 1) Weigh cyanate resin, ferrite powder, polyamine additive and low modulus small particles according to a mass ratio of 10:35:1:4, wherein the low modulus small particles are silicone rubber particles with a particle size of 10 μm, and prepare a low modulus absorbing adhesive film by compounding.

[0037] 2) Weigh glass fiber, epoxy resin and low modulus small particles according to a mass ratio of 19:28:1, wherein the low modulus small particles are silicone rubber particles with a particle size of 10 μm, firstly mix the low modulus small particles with the resin matrix, and then roll-press the glass fiber to prepare a low modulus glass fiber prepreg.

[0038] 3) Apply demoulding material on the surface of the molding tooling, wait for it to dry, and then lay 0.5mm carbon fiber prepreg in a symmetrical and balanced manner.

[0039] 4) Continue to lay 0.1mm low modulus absorbing film on the surface of the laid carbon fiber prepreg.

[0040] 5) Continue to lay 0.5mm low modulus glass fiber prepreg on the surface of the laid low modulus absorbing film.

[0041] 6) Continue to lay the isolation film and breathable felt on the surface of the laid low modulus glass fiber prepreg, and then prepare the vacuum bag. After passing the air tightness test, heat it to 130°C and keep it warm for 2 hours, pressurize it to 0.4MPa and co-curing it. After the molding tool is cooled to room temperature, demold it to obtain an absorbing layer with low curing deformation, such as Figure 1 shown.

[0042] Example 2

[0043] 1) Epoxy resin, carbonyl iron powder, aromatic polyamine additive and low modulus small particles are weighed in a mass ratio of 25:65:1:8, wherein the low modulus small particles are silicone rubber particles with a particle size of 100 μm, and a low modulus absorbing film is prepared by compounding.

[0044] 2) Weigh glass fiber, epoxy resin and low modulus small particles according to a mass ratio of 20:30:1, wherein the low modulus small particles are silicone rubber particles with a particle size of 100 μm, firstly mix the low modulus small particles with the resin matrix, and then roll-press the glass fiber to prepare a low modulus glass fiber prepreg.

[0045] 3) Apply demoulding material on the surface of the molding tooling, wait for it to dry, and then lay 5mm carbon fiber prepreg in a symmetrical and balanced manner.

[0046] 4) Continue to lay 4.5mm low modulus absorbing film on the surface of the laid carbon fiber prepreg.

[0047] 5) Continue to lay 2mm low modulus glass fiber prepreg on the surface of the laid low modulus absorbing film.

[0048] 6) Continue to lay the isolation film and breathable felt on the surface of the laid low modulus glass fiber prepreg, and then prepare the vacuum bag. After passing the air tightness test, heat it to 130°C and keep it warm for 2 hours, pressurize it at 0.5MPa for co-curing molding. After the molding tool is cooled to room temperature, demold it to obtain an absorbing layer board with low curing deformation.

[0049] Example 3

[0050] 1) Weighing polyurethane resin, silicon carbide fiber, organic acid additive and low modulus small particles according to a mass ratio of 20:50:2:6, the low modulus small particles are silicone rubber particles with a particle size of 200 μm, and compounding them to prepare a low modulus absorbing adhesive film.

[0051] 2) Weigh glass fiber, phenolic resin and low modulus small particles according to the mass ratio of 21:269:1, the low modulus small particles are silicone rubber particles with a particle size of 200 μm, firstly mix the low modulus small particles with the resin matrix, and then roll-press the glass fiber to prepare a low modulus glass fiber prepreg.

[0052] 3) Apply demoulding material on the surface of the molding tooling, wait for it to dry, and then lay 2mm carbon fiber prepreg in a symmetrical and balanced manner.

[0053] 4) Continue to lay 2mm low modulus absorbing film on the surface of the laid carbon fiber prepreg.

[0054] 5) Continue to lay 1.5mm low modulus glass fiber prepreg on the surface of the laid low modulus absorbing film.

[0055] 6) Continue to lay the isolation film and breathable felt on the surface of the laid low modulus glass fiber prepreg, and then prepare the vacuum bag. After passing the air tightness test, heat it to 130°C and keep it warm for 2 hours, pressurize it at 0.4MPa and co-curing it. After the molding tool is cooled to room temperature, demold it to obtain an absorbing layer board with low curing deformation.

[0056] Comparative Example 1

[0057] 1) Apply demoulding material on the surface of the molding tooling, wait for it to dry, and then lay 2mm carbon fiber prepreg, symmetrically and evenly laying the layers;

[0058] 2) Lay a 2 mm absorbing film (without adding low modulus particles), a 1.5 mm glass fiber prepreg (without adding low modulus particles), an isolation film and a breathable felt on the surface of the laid carbon fiber prepreg in sequence;

[0059] 3) After all materials are laid, a vacuum bag is prepared. After passing the air tightness test, it is heated and pressurized for curing. After the molding tool is cooled to room temperature, it is demoulded to obtain a co-cured absorbing layer board.

[0060] By comparing the products of the examples with the comparative examples, the absorbing layer plates prepared in examples 1-3 are basically consistent with the theoretical profile and have no obvious deformation. However, the absorbing layer plate prepared in comparative example 1 will be significantly deformed, and the profile after curing will deviate from the theoretical profile by 20 to 50 mm.

[0061] Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the present invention. Appropriate modifications or equivalent substitutions of the technical solutions of the present invention made by ordinary technicians in the field should all be included in the protection scope of the present invention. The protection scope of the present invention shall be based on what is defined in the claims.

Claims

1. A method for preparing a wave-absorbing layer with low curing deformation, characterized in that: The following steps are involved: 1) Weighing a resin matrix, an absorbent, an additive and low modulus small particles according to a mass ratio of (10-25):(35-65):(1-2):(4-8), wherein the low modulus small particles are micron-sized silicone rubber particles, and compounding them to prepare a low modulus absorbing adhesive film; 2) Weighing glass fiber, resin matrix and low modulus small particles according to the mass ratio of (19-21):(28-30):1, wherein the low modulus small particles are micron-sized silicone rubber particles, and compounding to prepare a low modulus glass fiber prepreg; 3) Symmetrical and balanced plying of carbon fiber prepreg is performed on the surface of the molding tool, and then individual curing and molding is performed; 4) Laying a low modulus absorbing adhesive film on the surface of the cured carbon fiber prepreg; 5) Laying low modulus glass fiber prepreg on the surface of low modulus absorbing film, and performing co-bonding and curing molding; 6) Continue to lay an isolation film and a breathable felt on the surface of the low modulus glass fiber prepreg, and then make a vacuum bag, perform co-curing molding in the vacuum bag, and then cool and demold to obtain an absorbing layer plate with low curing deformation.

2. The method according to claim 1, characterized in that The resin matrix in steps 1) to 2) is selected from at least one of cyanate resin, epoxy resin, polyurethane resin, phenolic resin, polyimide resin and bismaleimide resin.

3. The method according to claim 1, characterized in that The wave absorbing agent is selected from at least one of ferrite powder, carbonyl iron powder, conductive carbon black, carbon fiber, silicon carbide fiber, carbon nanotube and graphene.

4. The method according to claim 1, characterized in that The auxiliary agent is one of polyamine, aromatic polyamine, organic acid and acid anhydride.

5. The method according to claim 1, characterized in that The particle size of the silicone rubber particles is 10 to 200 μm.

6. The method according to claim 1, characterized in that In step 2), the low modulus small particles are firstly mixed with the resin matrix, and then the glass fibers are added and rolled to prepare a low modulus glass fiber prepreg.

7. The method according to claim 1, characterized in that The thickness of the carbon fiber prepreg is 0.5-5 mm, the thickness of the low modulus wave-absorbing adhesive film is 0.1-4.5 mm, and the thickness of the low modulus glass fiber prepreg is 0.5-2 mm.

8. The method according to claim 1, characterized in that The co-curing conditions are: pressure 0.4-0.5 MPa, heating to 130° C. and keeping warm for 2 hours.

9. The method according to claim 1, characterized in that The demoulding material is applied on the surface of the molding tool in advance and dried.

10. A wave absorbing layer with low curing deformation, characterized in that: The method is prepared by any one of claims 1 to 9.

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