1. A preparation method of a multilayer wave-absorbing composite material is characterized by comprising the following steps:

(1) compounding the wave-absorbing film with prepreg, and then carrying out airing treatment to obtain a wave-absorbing composite adhesive film; wherein, the absorbing film contains: wave absorbing agents, adhesives and diluents;

(2) performing vacuum-pumping pretreatment on the wave-absorbing composite adhesive film to obtain a pretreated wave-absorbing composite adhesive film;

(3) paving the pretreated wave-absorbing composite adhesive film on the skin until the target thickness is reached to obtain a target splicing piece; after each layer of the pretreated wave-absorbing composite adhesive film is laid, hot pressing treatment and vacuum preloading treatment are sequentially carried out;

(4) and curing the target splicing piece to obtain the multilayer wave-absorbing composite material.

2. The method of claim 1, wherein:

the wave absorbing agent is ferrite powder or magnetic alloy powder;

the adhesive is epoxy resin or cyanate resin;

the diluent is at least one of n-butanol, toluene, xylene and dioxane.

3. The method of claim 1, wherein:

the thickness of the wave absorbing film is 0.1-0.3 mm; and/or

The mass fraction of the wave absorbing agent in the wave absorbing film is 85-90%.

4. The method of claim 1, wherein:

in the step (1), before the wave-absorbing film is combined with the prepreg, the method further comprises:

and (3) placing the wave-absorbing film in an environment with the humidity less than or equal to 50% and the temperature of 20-30 ℃ and airing for 36-72 h.

5. The method of claim 1, wherein:

the prepreg is formed by compounding fiber cloth and prepreg resin;

the thickness of the prepreg is 0.1-0.28 mm; and/or

The fiber cloth is quartz fiber cloth, glass fiber cloth or carbon fiber cloth;

the prepreg resin is at least one of cyanate ester resin, epoxy resin and phenolic resin.

6. The method of claim 1, wherein:

in the step (1), the wave-absorbing film is compounded with the prepreg to obtain a prepreg composite adhesive film, and the airing treatment comprises the following steps:

and placing the prepreg composite adhesive film in an environment with the humidity less than or equal to 50% and the temperature of 20-30 ℃, standing for 4-5h, removing bubbles on the surface of the wave-absorbing composite adhesive film, and airing for 8-32h until no bubbles exist, thus obtaining the wave-absorbing composite adhesive film.

7. The method of claim 1, wherein:

in the step (2), the vacuum-pumping pretreatment comprises: placing the wave-absorbing composite adhesive film in a vacuum oven at the temperature of 60-80 ℃ and vacuumizing for 20-40 min; and/or

In the step (3), the laying direction of each layer of the pretreated wave-absorbing composite adhesive film is the same.

8. The method of claim 1, wherein:

in the step (3), the hot-pressing temperature of the hot-pressing treatment is 50-60 ℃, and the hot-pressing time is 5-15 s; and/or

In the step (3), the vacuum preloading treatment is to utilize a vacuum bag method to preload in a vacuum oven at 40-60 ℃ for 10-15 min.

9. The production method according to any one of claims 1 to 8, characterized in that:

in the step (4), the curing temperature of the curing treatment is 80-180 ℃, and the curing time is 6-8 h; and/or

The target thickness of the target splice is 1-3 mm.

10. A multilayer wave-absorbing composite material, characterized by being prepared by the preparation method of any one of claims 1 to 9.

Background

The wave-absorbing material is a functional material which can be used for attenuating incident radar waves so as to reduce the radar scattering cross section, and is widely applied to the fields of airplane stealth, ship stealth, flying missile stealth, tank stealth and the like.

At present, the conventional wave-absorbing adhesive film has brittleness, is easy to crack into small pieces, has poor mechanical bearing property and has larger paving difficulty when being stored at low temperature. Therefore, the multi-layer wave-absorbing adhesive film and the skin material are often required to be cured together to meet the performance index of the wave-absorbing composite material, however, because the fluidity of the adhesive in the wave-absorbing adhesive film is poor during curing, a diluent is usually required to be added to improve the fluidity so as to ensure the film formation of the wave-absorbing adhesive film, but the diluent is not easy to remove in the curing process, bubbles between layers are not easy to discharge, the adhesion is poor, the interlayer strength of the wave-absorbing composite material is further influenced, and even the wave-absorbing composite material has the defects of layering, debonding and the like, and the mechanical property of the wave-absorbing composite material is influenced.

Therefore, it is urgently needed to prepare a wave-absorbing/bearing composite material with dual functions.

Disclosure of Invention

The embodiment of the invention provides a multilayer wave-absorbing composite material and a preparation method thereof, and can provide a wave-absorbing/bearing multilayer wave-absorbing composite material.

In a first aspect, the invention provides a preparation method of a multilayer wave-absorbing composite material, which comprises the following steps:

(1) compounding the wave-absorbing film with prepreg, and then carrying out airing treatment to obtain a wave-absorbing composite adhesive film; wherein, the absorbing film contains: wave absorbing agents, adhesives and diluents;

(2) performing vacuum-pumping pretreatment on the wave-absorbing composite adhesive film to obtain a pretreated wave-absorbing composite adhesive film;

(3) paving the pretreated wave-absorbing composite adhesive film on the skin until the target thickness is reached to obtain a target splicing piece; after each layer of the pretreated wave-absorbing composite adhesive film is laid, hot pressing treatment and vacuum preloading treatment are sequentially carried out;

(4) and curing the target splicing piece to obtain the multilayer wave-absorbing composite material.

In a second aspect, the invention provides a multilayer wave-absorbing composite material prepared by the preparation method in the first aspect of the invention.

Compared with the prior art, the invention at least has the following beneficial effects:

(1) the wave-absorbing composite adhesive film prepared by the invention has strong bearing property, a layer of carrier (prepreg) is laid on the surface of the wave-absorbing film, and the wave-absorbing composite adhesive film is obtained after compounding, so that the strength of the adhesive film is enhanced, the construction of operators is more convenient, and the wave-absorbing composite adhesive film can be produced in batches and stored for a long time. In addition, the wave-absorbing composite adhesive film is adhered to the surface of the formed skin, so that the construction time is more convenient and flexible.

(2) According to the invention, the thinner in the wave-absorbing film and the wave-absorbing adhesive film is removed through airing, the target splicing piece with the preset thickness is obtained through preforming, the target splicing piece is subjected to step curing treatment to obtain the multilayer wave-absorbing composite material, the multilayer wave-absorbing composite material realizes effective adhesion of the wave-absorbing composite adhesive film in the multilayer wave-absorbing composite material, the strength and the adhesive force of the cured wave-absorbing composite adhesive film have the same service life as those of the composite material, the debonding and layering problems are solved, the reliability of a component prepared from the multilayer wave-absorbing composite material is improved, and the multilayer wave-absorbing composite material has double functions of wave absorption and bearing.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a schematic structural diagram of a multilayer wave-absorbing composite material prepared in example 1 of the present invention;

FIG. 2 is a schematic structural diagram of another multi-layer wave-absorbing composite material prepared by the invention;

FIG. 3 is a schematic structural diagram of another multilayer wave-absorbing composite material prepared by the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer and more complete, the technical solutions in the embodiments of the present invention will be described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention, and based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without creative efforts belong to the scope of the present invention.

The embodiment of the invention provides a preparation method of a multilayer wave-absorbing composite material, which comprises the following steps:

step (1), compounding a wave-absorbing film and a prepreg, and then carrying out air-drying treatment to obtain a wave-absorbing composite adhesive film; wherein, the absorbing film contains: wave absorbing agents, adhesives and diluents;

step (2), carrying out vacuum-pumping pretreatment on the wave-absorbing composite adhesive film to obtain a pretreated wave-absorbing composite adhesive film;

step (3), paving the pretreated wave-absorbing composite adhesive film on a skin until the thickness of the skin reaches a target thickness, and obtaining a target splicing piece; after each layer of the pretreated wave-absorbing composite adhesive film is laid, hot pressing treatment and vacuum preloading treatment are sequentially carried out;

and (4) curing the target splicing piece to obtain the multilayer wave-absorbing composite material.

According to some preferred embodiments, the wave absorbing agent is ferrite powder or magnetic alloy powder;

the adhesive is epoxy resin or cyanate resin;

the diluent is at least one of n-butanol, toluene, xylene and dioxane.

At least one of them is a mixture of any one or any several of them mixed in any ratio. Diluents include, but are not limited to, n-butanol, toluene, xylene, and dioxane.

According to some preferred embodiments, the thickness of the wave-absorbing film is 0.1-0.3mm (e.g. may be 0.1mm, 0.15mm, 0.2mm, 0.25mm or 0.3 mm). It should be noted that the thickness of the wave-absorbing film is the thickness of a single-layer wave-absorbing film.

According to some preferred embodiments, the mass fraction of the wave absorbing agent in the wave absorbing film is 85-90% (e.g. 85%, 86%, 87%, 88%, 89% or 90%).

The wave-absorbing film comprises, by mass, 5-10% of an adhesive and 2-8% of a diluent. For example, the wave-absorbing film comprises: 85% of wave absorbing agent, 10% of adhesive and 5% of diluent; for example, the wave-absorbing film comprises: 90% of wave absorbing agent, 8% of adhesive and 2% of diluent; for example, the wave-absorbing film comprises: 87% of wave absorbing agent, 5% of adhesive and 8% of diluent.

According to some preferred embodiments, in the step (1), before the step of compounding the wave-absorbing film with the prepreg, the method further comprises:

and (3) placing the wave-absorbing film in an environment with the humidity less than or equal to 50% and the temperature of 20-30 ℃ and airing for 36-72 h.

In a preferred embodiment, the wave-absorbing film is placed in an environment with humidity less than or equal to 50% (e.g., 50%, 40%, 30%, 20%, 10%, etc.) and temperature of 20-30 ℃ (e.g., 20 ℃, 22 ℃, 25 ℃, 28 ℃ or 30 ℃) and is dried for 36-72h (e.g., 36h, 42h, 48h, 54h, 60h, 66h or 72 h).

In the invention, the diluent mainly plays a role in reducing the viscosity of the adhesive so as to facilitate operation and improve the wettability and the fluidity of the adhesive, so that the finally obtained wave-absorbing film has better film-forming consistency. However, the existence of the diluent can influence the application of the wave-absorbing film, and because the diluent is not easy to remove and bubbles between layers are not easy to remove, the defects of poor adhesion, even layering, debonding and the like can be caused, and the mechanical property of the composite material prepared by using the wave-absorbing film is further influenced. By the airing treatment in the step (1), part of the diluent in the wave-absorbing film can be removed, so that the composite material prepared by using the wave-absorbing film has good mechanical properties.

According to some preferred embodiments, the prepreg is compounded from a fibrous cloth and a prepreg resin;

the thickness of the prepreg is 0.1 to 0.28mm (e.g. may be 0.1mm, 0.14mm, 0.2mm, 0.22mm or 0.28 mm).

According to some preferred embodiments, the fiber cloth is quartz fiber cloth, glass fiber cloth, or carbon fiber cloth;

the prepreg resin is at least one of cyanate ester resin, epoxy resin and phenolic resin.

According to some preferred embodiments, in the step (1), the wave-absorbing film is combined with the prepreg to obtain a prepreg composite adhesive film, and the drying treatment includes:

and placing the prepreg composite adhesive film in an environment with the humidity less than or equal to 50% and the temperature of 20-30 ℃, standing for 4-5h, removing bubbles on the surface of the wave-absorbing composite adhesive film, and airing for 8-32h until no bubbles exist, thus obtaining the wave-absorbing composite adhesive film.

In a preferred embodiment, the wave-absorbing film and the prepreg after being compounded are placed in an environment with humidity less than or equal to 50% (for example, 50%, 40%, 30%, 20%, 10% and the like) and temperature of 20-30 ℃ (for example, 20 ℃, 22 ℃, 25 ℃, 28 ℃ or 30 ℃) for 4-5h (for example, 4h, 4.2h, 4.5h, 4.7h or 5h), detecting whether the surface of the wave-absorbing composite adhesive film has bubbles or scratches and the like, if the surface has bubbles, the puncture is flattened to remove the air bubbles, the air is left for 8 to 32h (for example, 8h, 12h, 16h, 20h, 24h, 28h or 32h) until no air bubbles exist, that is, in the air-drying process, it is necessary to detect whether there are bubbles at certain time intervals (for example, it may be 2h, 3h or 4 h), and if so, remove them until there are no bubbles.

In the invention, after the wave-absorbing film and the prepreg are compounded, the diluent is gradually volatilized to generate bubbles through the standing and airing processes, and the generated bubbles are punctured and smoothed to remove the bubbles, so that not only is part of the diluent removed, but also the probability of interlayer bubbles in the subsequent multilayer bonding process is reduced, and the composite material prepared by using the wave-absorbing composite adhesive film is ensured to have good mechanical property.

It should be noted that the wave-absorbing composite adhesive film obtained by the method has good toughness (see the mechanical property data of comparative example 2 in table 1), and can be produced in batches and stored for a long time.

According to some more preferable embodiments, specifically, in the step (1), a layer of carrier (prepreg) is attached to the front surface of the wave-absorbing film, and a scraper is used to push the wave-absorbing film from the middle of the wave-absorbing composite film to both sides at a constant speed, so as to reduce the generation of bubbles during compounding for compounding, and finally obtain the wave-absorbing composite film.

According to some preferred embodiments, in the step (2), the vacuum pretreatment comprises: and placing the wave-absorbing composite adhesive film in a vacuum oven at the temperature of 60-80 ℃ and vacuumizing for 20-40 min.

According to some more preferred embodiments, the wave-absorbing composite glue film is placed in a vacuum oven at 60-80 ℃ (for example, 60 ℃, 65 ℃, 70 ℃, 75 ℃ or 80 ℃) for 20-40min (for example, 20min, 25min, 30min, 35min or 40min), and specifically, the pretreatment is performed by means of a vacuum kit, and the sequence is as follows: the device comprises a cotton breathable layer, a porous film, a demoulding layer, a wave-absorbing composite adhesive film, a demoulding layer, a porous film, a cotton breathable layer and a vacuum bag.

In the invention, the diluent in the wave-absorbing composite adhesive film is further removed through pretreatment in the step (2).

According to some preferred embodiments, in the step (3), the laying direction of each layer of the pretreated wave-absorbing composite adhesive film is the same. For example, as shown in fig. 1, a is used for skin, b is used for wave-absorbing film, and c is used for prepreg; the prepreg layer of each wave-absorbing composite adhesive film layer is only compounded with the wave-absorbing film layer of the adjacent wave-absorbing composite adhesive film layer. Therefore, the good cohesiveness and the uniformity of mechanical properties of the multi-layer wave-absorbing composite material can be ensured.

According to some more preferred embodiments, the structure of the multi-layer wave-absorbing composite material can also be as shown in fig. 2, namely, a layer of skin is laid on the structure as shown in fig. 1.

It should be noted that the structure of the multi-layer wave-absorbing composite material can also be as shown in fig. 3, that is, the laying direction is opposite to that in fig. 1.

According to some preferred embodiments, in the step (3), the hot pressing temperature of the hot pressing process is 50 to 60 ℃ (for example, 50 ℃, 52 ℃, 54 ℃, 56 ℃, 58 ℃ or 60 ℃), and the hot pressing time is 5 to 15s (for example, 5s, 8s, 10s, 12s or 15 s).

Specifically, the iron can be heated to 50-60 ℃ to carry out treatment for 5-15s on the skin paved with the pretreated wave-absorbing composite adhesive film so as to bond the skin and the wave-absorbing composite adhesive film.

According to some preferred embodiments, in the step (3), the vacuum preloading treatment is preloading for 10-15min in a vacuum oven at 40-60 ℃ by using a vacuum bag method.

Experiments prove that the skin on which the pretreated wave-absorbing composite adhesive film is laid is placed in a vacuum oven at 40-60 ℃ (for example, 40 ℃, 45 ℃, 50 ℃, 55 ℃ or 60 ℃) and is pre-pressed for 10-15min (for example, 10min, 11min, 12min, 13min, 14min or 15min) by a vacuum bag method.

In the invention, the coating of the laid and pretreated wave-absorbing composite adhesive film obtained by prepressing by using a vacuum bag method has an interlayer gap smaller than 1mm and is free from debonding.

According to some preferred embodiments, in the step (4), the curing temperature of the curing treatment is 80-180 ℃ and the curing time is 6-8 h.

In a preferred embodiment, the curing temperature of the curing treatment is 80 to 180 ℃ (for example, 80 ℃, 90 ℃, 100 ℃, 120 ℃, 140 ℃, 160 ℃ or 180 ℃), and the curing time is 6 to 8 hours (for example, 6 hours, 6.5 hours, 7 hours, 7.5 hours or 8 hours).

In the invention, when the target splicing member is cured, the wave absorbing agent is partially transferred into the fiber cloth of the prepreg, so that the content of the wave absorbing agent in the prepreg is increased, and the wave absorbing agent can be uniformly dispersed in the target splicing member.

According to some preferred embodiments, the target splice has a target thickness of 1-3 mm.

Specifically, the thickness of the prepared multilayer wave-absorbing composite material is 1-3mm (for example, 1mm, 1.2mm, 1.5mm, 1.8mm, 2mm, 2.2mm, 2.5mm, 2.8mm or 3 mm).

It should be noted that after the target splicing member is cured, the thickness of the target splicing member is reduced by 5-7%, that is, the thickness of the target splicing member is about 1.86-2.85 mm.

The invention also provides a multilayer wave-absorbing composite material which is prepared by the preparation method of the multilayer wave-absorbing composite material.

In order to more clearly illustrate the technical scheme and the advantages of the invention, the following describes in detail a preparation method of a multilayer wave-absorbing composite material by using several embodiments.

In the following embodiments, the preparation method of the wave-absorbing film comprises the following steps: and uniformly mixing the wave absorbing agent, the adhesive and the diluent to obtain a blending glue solution, and coating the blending glue solution on release paper to obtain the wave absorbing film.

Example 1

(1) Placing a wave absorbing film consisting of wave absorbing agent ferrite powder, adhesive cyanate ester resin and diluent n-butyl alcohol (wherein the wave absorbing film comprises 85% of wave absorbing agent, 10% of adhesive and 5% of diluent, and the thickness of the wave absorbing film is 0.2mm) in an environment with the humidity of 30% and the temperature of 25 ℃, airing for 36h, taking the aired wave absorbing film, cutting the wave absorbing film according to the same size with a prepreg (formed by compounding quartz fiber cloth and cyanate ester resin, and the thickness of the prepreg is 0.14mm), attaching a layer of cyanate ester quartz cloth (prepreg) on the front side of the cut wave absorbing film (wherein release paper is attached to the back side of the film, and the release paper is removed when the wave absorbing film is attached with the prepreg), and horizontally pushing from the middle of the wave absorbing composite adhesive film to two sides at a constant speed by using a scraper blade to obtain the wave absorbing composite adhesive film primarily. In order to further remove the diluent in the wave-absorbing composite adhesive film, the wave-absorbing composite adhesive film is required to be placed in an environment with the humidity of 30% and the temperature of 25 ℃, after standing for 5 hours, whether bubbles or scratches and other phenomena exist on the surface of the primarily obtained wave-absorbing composite adhesive film is detected, if bubbles exist, the bubbles are punctured and smoothed to remove the bubbles, and then the wave-absorbing composite adhesive film is dried for 12 hours until no bubbles exist, so that the wave-absorbing composite adhesive film is finally obtained;

(2) will inhale compound glued membrane of ripples and cut into many compound glued membranes of ripples, will inhale compound glued membrane of ripples and place many in 60 ℃ oven stoving 20min, adopt the mode of vacuum external member to carry out evacuation pretreatment, the order is: the microwave absorbing composite film comprises a cotton breathable layer, a porous film, a demoulding layer, a microwave absorbing composite film, a demoulding layer, a porous film, a cotton breathable layer and a vacuum bag (the sequence can not be changed at will), so that part of diluent is volatilized by vacuumizing to obtain a microwave absorbing composite film after pretreatment;

(3) paving a layer of the wave-absorbing composite adhesive film pretreated in the step (2) on a skin (with the thickness of 1mm), then carrying out hot pressing treatment for 10s by using an iron heated to 50 ℃, prepressing for 10min in a vacuum oven at 60 ℃ by using a vacuum bag method, and taking out; repeating the paving, the hot pressing and the vacuum prepressing for 5 times (namely, superposing 5 layers of pretreated wave-absorbing composite adhesive films on the skin in total) until the target thickness (2.5-3mm) is reached, and obtaining a target splicing piece; wherein the laying direction of each layer of the pretreated wave-absorbing composite adhesive film is the same;

(4) and curing the target splicing piece, wherein the curing process comprises 80 ℃/3h,110 ℃/1h,150 ℃/1h and 180 ℃/2h, continuous vacuum pumping is required in the curing process, and finally the multi-layer wave-absorbing composite material is obtained after curing. The structural schematic diagram of the multilayer wave-absorbing composite material is shown in fig. 1, wherein a is used for representing a skin, b is used for representing a wave-absorbing film, c is used for representing a prepreg, a wave-absorbing composite adhesive film is formed by b and c, and 5 layers of wave-absorbing composite adhesive films are formed in total.

Example 2

(1) Placing a wave absorbing film consisting of wave absorbing agent ferrite powder, adhesive epoxy resin and diluent dioxane (wherein the wave absorbing film comprises 90% of wave absorbing agent, 8% of adhesive and 2% of diluent, and the thickness of the wave absorbing film is 0.3mm) in an environment with the humidity of 35% and the temperature of 30 ℃, airing for 40 hours, taking the aired wave absorbing film, cutting the wave absorbing film according to the same size with prepreg (formed by compounding quartz fiber cloth and cyanate resin, and the thickness of the prepreg is 0.2mm), attaching a layer of cyanate quartz cloth (prepreg) on the front surface of the cut wave absorbing film, and horizontally pushing the wave absorbing film from the middle to two sides of the wave absorbing composite adhesive film at a constant speed by using a scraper blade to obtain the wave absorbing composite adhesive film preliminarily. In order to further remove the diluent in the wave-absorbing composite adhesive film, the wave-absorbing composite adhesive film is required to be placed in an environment with the humidity of 35% and the temperature of 30 ℃, after standing for 5 hours, whether bubbles or scratches and other phenomena exist on the surface of the primarily obtained wave-absorbing composite adhesive film is detected, if bubbles exist, the bubbles are punctured and smoothed to remove the bubbles, and then the wave-absorbing composite adhesive film is dried for 24 hours until no bubbles exist, so that the wave-absorbing composite adhesive film is finally obtained;

(2) the wave-absorbing composite adhesive film is cut into a plurality of wave-absorbing composite adhesive films, the wave-absorbing composite adhesive films are placed in a 40 ℃ oven for drying for 30min, and vacuumizing pretreatment is performed by adopting a vacuum external member mode, wherein the sequence is as follows: the microwave absorbing composite film comprises a cotton breathable layer, a porous film, a demoulding layer, a microwave absorbing composite film, a demoulding layer, a porous film, a cotton breathable layer and a vacuum bag (the sequence can not be changed at will), so that part of diluent is volatilized by vacuumizing to obtain a microwave absorbing composite film after pretreatment;

(3) paving and covering a layer of the wave-absorbing composite adhesive film pretreated in the step (2) on a skin (with the thickness of 1mm), fusing and using an iron heated to 60 ℃ for hot pressing for 5s, prepressing in a vacuum oven at 60 ℃ for 10min by using a vacuum bag method, and taking out; repeating the paving, the hot pressing and the vacuum prepressing for 4 times (namely, superposing 4 layers of pretreated wave-absorbing composite adhesive films on the skin in total) until the target thickness (2-3mm) is reached, and obtaining a target splicing piece; wherein the laying direction of each layer of the pretreated wave-absorbing composite adhesive film is the same;

(4) and curing the target splicing piece, wherein the curing process is 80 ℃/3h,110 ℃/1h and 150 ℃/2h, continuous vacuum pumping is required in the curing process, and finally the multilayer wave-absorbing composite material is obtained after curing.

Example 3

Example 3 is essentially the same as example 1, except that:

the wave-absorbing film consists of wave-absorbing agent magnetic alloy powder, adhesive epoxy resin and diluent toluene, wherein the wave-absorbing film comprises: 87% of wave absorbing agent, 5% of adhesive and 8% of diluent; the prepreg is formed by compounding glass fiber cloth and phenolic resin;

in the step (1), the wave-absorbing film is placed in an environment with the humidity of 40% and the temperature of 20 ℃ and is aired for 60 hours; in order to further remove the diluent in the wave-absorbing composite adhesive film, the wave-absorbing film and the prepreg which are compounded are placed in an environment with the humidity of 40% and the temperature of 20 ℃, standing for 4.5 hours, detecting whether bubbles or scratches and other phenomena exist on the surface of the primarily obtained wave-absorbing composite adhesive film, if bubbles exist, the bubbles are punctured and smoothed to remove the bubbles, and then airing for 32 hours until no bubbles exist, so that the wave-absorbing composite adhesive film is finally obtained;

in the step (2), the wave-absorbing composite adhesive film is placed in a vacuum oven at 80 ℃ for 20 min;

and (3) prepressing in a vacuum oven at 40 ℃ for 15min by utilizing a vacuum bag method.

Example 4

Example 4 is essentially the same as example 2, except that: the wave-absorbing film consists of wave-absorbing agent magnetic alloy powder, adhesive epoxy resin and diluent dimethylbenzene, wherein the wave-absorbing film comprises: 88% of wave absorbing agent, 8% of adhesive and 4% of diluent; the thickness of the wave-absorbing film is 0.1 mm; the prepreg (formed by compounding carbon fiber cloth and epoxy resin) is 0.1mm thick;

in the step (1), the wave-absorbing film is placed in an environment with the humidity of 50% and the temperature of 30 ℃ and is aired for 72 hours; in order to further remove the diluent in the wave-absorbing composite adhesive film, the wave-absorbing film and the prepreg which are compounded are placed in an environment with the humidity of 50% and the temperature of 30 ℃, standing for 4 hours, detecting whether bubbles or scratches and other phenomena exist on the surface of the primarily obtained wave-absorbing composite adhesive film, if bubbles exist, tearing and flattening the film to remove the bubbles, and then airing the film for 8 hours until no bubbles exist, so that the wave-absorbing composite adhesive film is finally obtained;

in the step (2), the wave-absorbing composite adhesive film is placed in a vacuum oven at 70 ℃ for 30 min;

in the step (3), the spreading, the hot pressing treatment and the vacuum preloading treatment are repeated for 10 times.

Comparative example 1

Comparative example 1 is substantially the same as example 1 except that: the drying treatment is not carried out on the preliminarily obtained wave-absorbing composite adhesive film in the step (1), and the step (2) only cuts the wave-absorbing composite adhesive film to obtain a plurality of wave-absorbing composite adhesive films and does not carry out vacuumizing pretreatment.

Comparative example 2

Comparative example 2 is substantially the same as example 1 except that:

in the step (2), the wave-absorbing composite adhesive films are only cut to obtain a plurality of wave-absorbing composite adhesive films, and vacuumizing pretreatment is not performed.

Comparative example 3

Comparative example 3 is substantially the same as example 1 except that: and (2) air-drying the primarily obtained wave-absorbing composite adhesive film in the step (1).

The multilayer wave-absorbing composite materials obtained in examples 1 to 4 and comparative examples 1 to 3 were subjected to mechanical property tests such as tensile, compressive and flexural properties, and the mechanical property data shown in table 1 were obtained. As can be seen from Table 1, the multi-layer wave-absorbing composite materials obtained in examples 1 to 4 have mechanical properties superior to those of the multi-layer wave-absorbing composite materials obtained in comparative examples 1 to 3. In comparative examples 1 to 3, because no vacuum-pumping pretreatment or air-drying treatment is performed, the wave-absorbing composite adhesive film still contains a diluent which is not easy to remove, so that bubbles between layers are not easy to remove in the curing process, the interlayer strength of the multi-layer wave-absorbing composite material is affected, and the multi-layer wave-absorbing composite material has poor mechanical property and poor toughness. However, the wave-absorbing composite adhesive films adopted in the embodiments 1 to 4 have more excellent interlayer shear strength after air-drying treatment and vacuum-pumping pretreatment, so that the prepared multilayer wave-absorbing composite material has better internal cohesiveness and excellent adhesive force, and can improve the reliability of the member prepared from the multilayer wave-absorbing composite material.

TABLE 1

Note that in fig. 1 to 3, the widths of the layers a, b, and c do not represent the actual thicknesses of the respective layers.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.