CN113635646A

CN113635646A - Composite material cover body with wave-absorbing stealth and sealing waterproof functions and preparation method thereof

Info

Publication number: CN113635646A
Application number: CN202110859386.1A
Authority: CN
Inventors: 尹亮; 黄玉东; 崔超; 钟正祥; 刘丽
Original assignee: Harbin Institute of Technology
Current assignee: Harbin Institute of Technology
Priority date: 2021-07-28
Filing date: 2021-07-28
Publication date: 2021-11-12
Anticipated expiration: 2041-07-28
Also published as: CN113635646B

Abstract

The invention discloses a composite material cover body with wave-absorbing stealth and sealing waterproof functions and a preparation method thereof, wherein the composite material cover body is in a semi-circular ring shape and comprises an outer cover with the wave-absorbing stealth function, a foam core layer and a glass fiber reinforced plastic inner cover, wherein: the wave-absorbing stealthy functional outer skin comprises a surface layer, a wave-absorbing layer, a spacing layer, a shielding layer and a base layer; the foam core layer is composed of polyurethane foam; the glass fiber reinforced plastic inner skin is formed by curing glass fiber prepreg. The composite material cover body realizes the stealth function by adopting a method of shape reflection, multi-level wave absorption and signal shielding, adopts a resin vacuum introduction process to form an outer skin with a complex profile and accurate interlayer spacing, and uses a low-temperature cured epoxy glass fiber prepreg combined with an OOA process to form an inner skin, so that the composite material cover body is manufactured with high precision, high quality and low cost.

Description

Composite material cover body with wave-absorbing stealth and sealing waterproof functions and preparation method thereof

Technical Field

The invention belongs to the technical field of composite material structure function integrated forming processes, and relates to a composite material cover body with wave-absorbing stealth and sealing waterproof functions and a preparation method thereof.

Background

Nowadays, military radar technology is continuously developed, and radar wave-absorbing materials for anti-radar detection are also unprecedented in development. The foam sandwich type wave-absorbing material not only has high absorption rate to electromagnetic waves in a wider frequency band, but also has the characteristics of light weight, high temperature resistance, humidity and heat resistance, corrosion resistance and the like.

In the aerospace field, aiming at a composite material secondary structural part, a prepreg technology (OOA technology) that a hot furnace is used for curing and a vacuum bag is used for pressing prepreg, namely, the prepreg is separated from an autoclave is adopted, and the application prospect is excellent due to the advantages that the traditional autoclave prepreg technology is more flexible, faster in forming, more economical and the like. However, in consideration of the performance and the internal quality of the part, higher requirements are also put forward on the prepreg, and meanwhile, the curing temperature of the traditional prepreg is mostly concentrated at 95-130 ℃ or even higher, so that the part is deformed and the dimensional accuracy is influenced during secondary curing molding. Therefore, the development of the low-temperature curing prepreg not only meets the actual application requirements in the aerospace field, but also has important significance for the molding of high-quality parts.

Interest in OOA processes has also facilitated the use of Resin Transfer Molding (RTM), Vacuum Assisted Resin Transfer Molding (VARTM), and other resin forming processes.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a composite material cover body with wave-absorbing stealth and sealing and waterproof functions and a preparation method thereof. The composite material cover body realizes the stealth function by adopting a method of shape reflection, multi-level wave absorption and signal shielding, adopts a resin vacuum introduction process to form an outer skin with a complex profile and accurate interlayer spacing, and uses a low-temperature cured epoxy glass fiber prepreg combined with an OOA process to form an inner skin, so that the composite material cover body is manufactured with high precision, high quality and low cost.

The purpose of the invention is realized by the following technical scheme:

the utility model provides a combined material cover body with inhale ripples stealthy and waterproof seal function, is half ring shape, comprises inhale ripples stealthy function outer covering, foam core layer and glass steel inner skin, wherein: the wave-absorbing stealthy functional outer skin comprises a surface layer, a wave-absorbing layer, a spacing layer, a shielding layer and a base layer, wherein the surface layer, the first wave-absorbing layer, the first spacing layer, the second wave-absorbing layer, the second interlayer, the third wave-absorbing layer, the third spacing layer, the shielding layer and the base layer are respectively arranged from outside to inside; the foam core layer is composed of polyurethane foam; the glass fiber reinforced plastic inner skin is formed by curing glass fiber prepreg.

In the invention, the planeness of the reference surface A of the composite material cover body is less than or equal to 0.3mm, the planeness of the lower working surface is less than or equal to 0.3mm, the parallelism of the lower working surface and the reference surface A is less than or equal to 0.4mm, and the planeness of the lower working surface is less than or equal to 0.5 mm.

In the invention, the wave-absorbing stealth functional outer skin is designed into a polyhedral shape through computer assistance, so that strong reflection points are prevented from being generated in the radar detection direction, and the appearance stealth effect is achieved.

In the invention, the wave-absorbing felt is laid in the wave-absorbing layer, the glass fiber cloth is laid in the spacing layer and the base layer, and the carbon fiber cloth is laid in the shielding layer.

In the invention, the thickness of the surface layer is 1.3mm, and the thickness of the first interlayer, the second interlayer and the third interlayer is 0.8 mm.

In the invention, the reflection rate of the wave-absorbing stealth functional outer skin on the radar detection wave with the frequency of 8-18 GHz is less than or equal to-9 dB.

In the invention, the compressive strength of the polyurethane foam used for the foam core layer is not lower than 0.2 MPa.

In the invention, the glass fiber prepreg is low-temperature cured epoxy glass fiber prepreg.

In the invention, 2 layers of low-temperature curing adhesive films are paved between the glass fiber reinforced plastic inner skin and the foam core layer for bonding, and the paving area is a polyurethane foam surface.

According to the invention, the glass fiber reinforced plastic inner skin and the wave-absorbing stealth functional outer skin are in lap joint, 2 layers of low-temperature curing adhesive films are laid in the middle for bonding, and the laying area is the lap joint area of the glass fiber reinforced plastic inner skin and the wave-absorbing stealth functional outer skin.

In the invention, the surface of the lower working surface of the composite material cover body is provided with a wear-resistant layer.

In the invention, white carbon black with the resin mass ratio of 3% is added into the wear-resistant layer.

A preparation method of the composite material cover body with the wave-absorbing stealth and sealing waterproof functions comprises the following steps:

step 1, manufacturing an outer skin forming die, and forming the complex polyhedron wave-absorbing stealth functional outer skin through the die, wherein:

the outer skin forming die comprises an upper template, a lower template, two end baffles, a window stop block and a side female die, and the shape of the forming surface of the side female die is consistent with the shape of the outer surface of the cover body; the upper template and the lower template allow for the overlapping of the inner skins, and the template protrudes by 1mm in the overlapping edge area of the outer skins; the baffles at the two ends allow for the overlapping of the inner skins, and the same forming surface protrudes by 1mm to form a step and also have an assembly limiting structure;

step 2, lay glass fiber cloth, carbon fiber cloth and inhale the ripples felt at outer covering forming die inner chamber according to the design order, through resin vacuum infusion technology solidification shaping, inhale and keep in the mould behind the stealthy function outer covering solidification of ripples to polishing treatment is carried out deckle edge and internal surface, wherein:

when the wave-absorbing stealth functional outer skin is spread, the glass fiber cloth and the wave-absorbing felt are in butt joint and spread; the resin vacuum infusion process adopts a low-speed flow guide net, the flow guide net is lapped by 5-15 mm, and the width of the glue blocking belt is 70-100 mm;

the resin vacuum infusion process glue injection pipeline is arranged to be laid along the 50mm circumference from the outer edge of the lower working surface, the window stop block is laid at the transverse center line position, and the air extraction pipeline is arranged to be laid along the shape 30mm from the outer edge of the reference surface A;

in the vacuum introduction process of the resin, firstly, opening a glue injection pipeline at the lower working face position, and opening the glue injection pipeline at the position until the fiber is completely soaked when the resin near the window stop block is soaked to the central line of the stop block;

maintaining the pressure before vacuum introduction of the resin, wherein the vacuum pressure is less than or equal to-95 KPa, and the pressure rise is not more than 0.5KPa after 5min of pressure maintaining;

the resin vacuum introduction process is to keep a vacuumizing state for curing for more than 24 hours;

the resin vacuum infusion process controls the ambient temperature in the curing process to be 25 +/-5 ℃;

step 3, carrying out polyurethane foam foaming in the inner cavity of the wave-absorbing stealth functional outer skin by means of a foam pressing plate tool, wherein:

the polyurethane foam is foamed by adopting a spraying and pouring process, and the corner area of the inner cavity of the stealth functional outer skin is foamed by adopting a spraying process, so that the foam is completely filled; after the corner area is completely filled, the pouring process is adopted to complete the integral foaming of the inner cavity;

the foaming mode of the polyurethane foam is net-size foaming;

step 4, glue film and prepreg paving are carried out on the surfaces of the lap edges of the polyurethane foam and the wave-absorbing stealth functional outer skin, then the inner skin is integrally cured and formed, and the curing is completed and then demoulding is carried out to obtain a composite material cover body, wherein:

the inner skin is formed by adopting an OOA process;

the OOA process is an oven vacuum curing process;

in the process of laying the inner skin prepreg, vacuumizing and sucking the glue once every 5 layers are laid, wherein the glue sucking time is half an hour;

the vacuum pressure of the prepreg suction of the inner skin is kept to be less than or equal to-95 KPa;

the temperature of the prepreg of the inner skin for absorbing the glue is 25 +/-5 ℃;

the OOA process curing process comprises the steps of initially vacuumizing and pressurizing, controlling the curing temperature to be 80 +/-5 ℃, and preserving heat for 6 hours;

maintaining the pressure before the OOA process is cured, wherein the vacuum pressure is less than or equal to-95 KPa, and the air leakage rate is less than or equal to 1 KPa/min;

the temperature rising rate of the OOA process curing process is controlled to be 20 +/-5 ℃.

Compared with the prior art, the invention has the following advantages:

(1) the invention adopts the wave-absorbing felt and fiber cloth laying, the resin vacuum introduction process is adopted to form the structure and function integrated outer skin, the thickness size of each functional layer is accurately controlled by designing the laying sequence, the radar detection wave reflectivity of 8-18 GHz frequency is ensured to be less than or equal to-9 dB, the stealth purpose is achieved, the resin is introduced through negative pressure, the fiber is fully infiltrated and then cured, the porosity of the integral outer skin is low, and the performance is close to that of the autoclave process.

(2) According to the invention, the prepreg is spread by low-temperature curing, the inner skin is molded by an OOA process, and the curing is carried out by an oven, so that an autoclave is avoided, the curing temperature is low, the production cost is greatly reduced, the thermal deformation of a component is small due to the low curing temperature, and the dimensional precision of the composite material cover body is improved.

(3) This has designed simple vulva mode structure mould, and the mould is simple, and the design degree of difficulty is low, and no material selection difficulty, the outer covering adopts room temperature (25 +/-5 ℃) solidification, and the inner covering adopts oven 80 +/-5 ℃ solidification, and mould heat altered shape is little, has guaranteed that the combined material cover body size precision is high, and later stage fit-up gap is little, is favorable to waterproofly.

(4) The invention realizes the forming and defect control of the composite material cover body with integrated structure and function, solves the technical problem that the dimensional precision of the composite material cover body is difficult to control, and greatly reduces the operation difficulty and the cost. Compared with the traditional prepreg autoclave molding process, the method improves the quality stability and consistency of the component, and has important application value.

Drawings

FIG. 1 is a typical structural diagram of a composite material cover body with wave-absorbing stealth and sealing waterproof functions, wherein (a) a top view, (b) a bottom view and (c) a cross-sectional view are shown;

FIG. 2 is a flow chart of the preparation of a composite cover with wave-absorbing stealth and waterproof sealing functions;

FIG. 3 is a schematic view of the mold assembly, (a) the upper and lower mold plates in an assembled state, and (b) the baffle in an assembled state;

FIG. 4 is a schematic view of an exemplary construction of an outer skin;

FIG. 5 is a schematic diagram showing the lapping of the inner and outer skins, (a) the lapping mode of the inner and outer skins at the position of the datum plane, and (b) the lapping mode of the inner and outer skins and the molding position of the wear-resistant layer at the position of the lower working surface;

in the figure, 1-a reference plane A, 2-a lower working plane, 3-a lower plane, 4-a wave-absorbing stealth functional outer covering, 5-a foam core layer, 6-a glass fiber reinforced plastic inner covering, 7-a mould upper template, 8-a mould lower template, 9-a side female mould, 10-a baffle, 11-a surface layer, 12-a first wave-absorbing layer, 13-a first spacing layer, 14-a second wave-absorbing layer, 15-a second spacing layer, 16-a third wave-absorbing layer, 17-a third spacing layer, 18-a shielding layer, 19-a base layer and 20-a wear-resistant layer.

Detailed Description

The technical solution of the present invention is further described below with reference to the accompanying drawings, but not limited thereto, and any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be covered by the protection scope of the present invention.

The invention provides a composite material cover body with wave-absorbing stealth and sealing waterproof functions, which comprises an outer cover with the wave-absorbing stealth function, a foam core layer and a glass fiber reinforced plastic inner cover, wherein: the wave-absorbing stealthy functional outer skin comprises a surface layer 11, wave-absorbing layers, spacing layers, a shielding layer 18 and a base layer 19, wherein the surface layer 11, the first wave-absorbing layer 12, the first spacing layer 13, the second wave-absorbing layer 14, the second spacing layer 15, the third wave-absorbing layer 16, the third spacing layer 17, the shielding layer 18 and the base layer 19 are arranged from outside to inside respectively; the foam core layer is composed of polyurethane foam; the glass fiber reinforced plastic inner skin is formed by curing glass fiber prepreg. The typical structure of the composite material cover body is shown in fig. 1, and the corresponding outer skin forming die and the foam pressing plate tool are designed and manufactured according to the structural characteristics of the composite material cover body. The planeness of the reference surface A1 is less than or equal to 0.3mm, the planeness of the lower working surface 2 is less than or equal to 0.3mm, the parallelism of the lower working surface 2 and the reference surface A1 is less than or equal to 0.4mm, and the planeness of the lower working surface 3 is less than or equal to 0.5 mm.

The technological process of the composite material cover body with the wave-absorbing stealth and sealing waterproof functions is shown in figure 2 and is divided into a mold design process and a composite material cover body manufacturing process, and the method is realized through the following steps:

1. design of outer skin forming die

Based on the appearance structure characteristics of the composite material cover body and the connection form of the inner skin and the outer skin, an outer female die structure is designed, the material is steel, the overlapping of the inner skin is required to be considered for the upper die plate, the lower die plate and the baffles at two ends of the die, the overlapped forming surface is designed to protrude for 1mm, the upper die plate and the lower die plate are limited by using pins, the baffles at two ends are limited by using protruding steps, the cross section is as shown in figure 3, and sealing strips are embedded in the splicing seams of the die and used for keeping the air tightness of the resin vacuum leading-in process.

2. Prepreg preparation

(1) Prepreg material selection

The prepreg with medium and high viscosity meeting the requirement of the initial pressurization process is selected, and the technical indexes are shown in table 1.

TABLE 1 prepreg quality index of composite material by hot-melting method

(2) Prepreg cutting

The prepreg is cut according to the size of the die, and an automatic blanking machine or manual cutting can be adopted.

3. Outer skin forming

(1) Mold assembly

And assembling the upper template, the lower template, the two end baffles, the window stop blocks and the side female dies.

(2) Wave-absorbing felt and fiber cloth laying layer

Laying layers on the inner surface of the mold according to a preset laying sequence, wherein the cross section is as shown in figure 4, and after laying layers, sequentially coating demolding cloth, an isolation material, a flow guide net and a vacuum bag film, and arranging a glue injection pipeline and an air suction pipeline.

(3) Air-tight seal

And (4) plugging the glue injection port, vacuumizing until the pressure in the vacuum bag is less than or equal to-95 KPa, and keeping the pressure for 5min until the pressure rises to be less than or equal to 0.5 KPa.

(4) Vacuum infusion

And after the pressure maintaining is qualified, preparing the resin according to a specified proportion, uniformly mixing, performing resin vacuum infusion, closing an injection pipeline after the infusion is completed, and curing for more than or equal to 24 hours at the temperature of 25 +/-5 ℃.

(5) Trimming and polishing

And (4) cutting burrs according to the appearance and the size of the outer skin, and polishing the inner surface of the outer skin roughly.

4. Foam core layer formation

(1) And (3) taking the surface of the outer skin forming die as a foam forming reference, protecting a non-spraying area, and then forming the foam in the corner area by adopting a spraying process.

(2) And cutting off the foam interference area, performing foam limiting by using the contour of the molding cover plate and the outer skin, and molding the foam of the rest inner cavity area by adopting a pouring process mode.

5. Inner skin forming

(1) And (3) polishing the surface of the foam to be rough, and laying 2 layers of low-temperature curing adhesive films, wherein the laying area is the overlapping area of the surface of the foam and the inner and outer skins, and the overlapping mode is shown in figure 5.

(2) And (3) performing low-temperature curing prepreg laying according to the preset laying sequence and quantity, wherein the laying area and the glue film laying area are subjected to vacuum pumping and glue sucking once every 5 layers are laid, the temperature required in the glue sucking process is 25 +/-5 ℃, and the vacuum pressure is kept for half an hour less than or equal to-95 KPa.

(3) And (3) vacuumizing and maintaining the pressure after coating the composite material, wherein the vacuum pressure is required to be less than or equal to-95 KPa, and the air leakage rate is required to be less than or equal to 1 KPa/min.

(4) And curing and molding the whole cover body, controlling the heating rate to be 20 +/-5 ℃, controlling the highest temperature to be 80 +/-5 ℃, and keeping the temperature for 6 hours for full curing.

6. Demolding of cover body

And (4) sequentially removing the lower template and the side female die and cleaning the residual glue.

7. Formation of wear resistant layer

And (3) performing hand pasting and layering according to the preset layering sequence and quantity, wherein the resin system is formed by adding 3% of white carbon black by mass of resin, and curing for more than 24 hours at the temperature of 25 +/-5 ℃.

8. Appearance modification and perforation

The outer surface is modified and holes are punched after positioning in the designated area.

The invention uses the wave-absorbing felt to form a multi-stage wave-absorbing functional layer, and adopts the resin vacuum introduction process to carry out structural solidification, thereby realizing the integral molding manufacture of a multi-profile complex structure. The process mold is simple in design, the forming process can be completed only by using the single-piece outer female mold, a complex appearance structure can be formed through reasonable layering and runner arrangement, and compared with other liquid forming processes, the process mold has the advantages of being low in cost, simple to operate, high in efficiency and the like.

Example (b):

the product name is as follows: watertight protective cover

Structural description: as shown in figure 1, the watertight protective cover is in a semicircular ring shape, the inner circle radius is 885mm, the outer circle radius is 930mm, the overall height is 260mm, the height of a working surface is 232mm, and the watertight protective cover is of an A sandwich structure of skin and foam.

The implementation steps are as follows:

(1) and assembling the upper template, the lower template, the two end baffles, the window stop blocks and the side female dies.

(2) Laying layers on the inner surface of the mold according to a preset laying sequence, sequentially coating demolding cloth, an isolation material, a flow guide net and a vacuum bag film after laying layers, and arranging an injection pipeline and an air suction pipeline.

(3) Vacuumizing and maintaining pressure, wherein the vacuum pressure is required to be less than or equal to-95 KPa, and the pressure rise is not more than 0.5KPa after 5min of pressure maintaining. And after the pressure is maintained to be qualified, performing vacuum infusion on the mixed resin, closing the glue injection pipeline after the infusion is finished, and curing for more than or equal to 24 hours at the temperature of 25 +/-5 ℃.

(4) And (4) cutting burrs according to the appearance and the size of the outer skin, and polishing the inner surface of the outer skin roughly.

(5) And (3) performing spray molding on the foams in the corner regions by using the surface of the outer skin molding die as a foam molding reference, and performing casting molding on the foams in the other inner cavity regions.

(6) The prepreg selects the initial pressurized prepreg with the single-layer thickness of 0.17mm and the breadth of 1000mm, and has the main technical indexes that: 44 +/-3% of resin, less than or equal to 1% of volatile matter, 200 +/-20 g.m of fiber surface density^-2The longitudinal bending strength is more than or equal to 400MPa, and the longitudinal interlaminar shear strength is more than or equal to 40 MPa. And cutting the prepreg according to the required size.

(7) Polishing the surface of the foam to be rough, and performing low-temperature curing prepreg laying of low-temperature curing adhesive films according to the preset laying sequence and quantity, wherein the laying area is the foam surface and the lapping area of the inner skin and the outer skin, the prepreg is required to be vacuumized and glue-absorbed once every 5 layers, the temperature required in the glue-absorbing process is 25 +/-5 ℃, and the vacuum pressure is kept for half an hour less than or equal to-95 KPa.

(8) And (3) vacuumizing and maintaining the pressure after coating the composite material, wherein the vacuum pressure is required to be less than or equal to-95 KPa, and the air leakage rate is required to be less than or equal to 1 KPa/min. Curing and forming after the pressure maintaining is qualified, wherein the temperature rising rate is required to be controlled to be 20 +/-5 ℃, the highest temperature is required to be controlled to be 80 +/-5 ℃, and the temperature is kept for 6 hours.

(9) And (4) sequentially removing the lower template and the side female die and cleaning the residual glue.

(10) And (3) performing hand pasting and layering according to the preset layering sequence and quantity, wherein the resin system is formed by adding 3% of white carbon black by mass of resin, and curing for more than 24 hours at 25 +/-5 ℃.

(11) The outer surface is modified and holes are punched after positioning in the designated area.

The invention is not described in detail and is within the knowledge of a person skilled in the art.

Claims

1. The utility model provides a combined material cover body with inhale ripples stealthy and sealed waterproof function which characterized in that the combined material cover body is half annular shape, comprises inhale ripples stealthy function outer covering, foam core layer and glass steel inner skin, wherein: the wave-absorbing stealthy functional outer skin comprises a surface layer, a wave-absorbing layer, a spacing layer, a shielding layer and a base layer, wherein the surface layer, the first wave-absorbing layer, the first spacing layer, the second wave-absorbing layer, the second interlayer, the third wave-absorbing layer, the third spacing layer, the shielding layer and the base layer are respectively arranged from outside to inside; the foam core layer is composed of polyurethane foam; the glass fiber reinforced plastic inner skin is formed by curing glass fiber prepreg.

2. The composite material cover body with the wave-absorbing stealth and sealing waterproof functions as claimed in claim 1, wherein the wave-absorbing stealth functional outer skin is in a polyhedral shape; the glass fiber prepreg is low-temperature cured epoxy glass fiber prepreg.

3. The composite material cover body with the wave-absorbing stealth and sealing waterproof functions as claimed in claim 1, wherein a wave-absorbing felt is laid in the wave-absorbing layer, glass fiber cloth is laid in the spacing layer and the base layer, and carbon fiber cloth is laid in the shielding layer.

4. The composite material cover body with the wave-absorbing stealth and sealing waterproof functions as claimed in claim 1, wherein 2 layers of low-temperature curing adhesive films are laid between the glass fiber reinforced plastic inner skin and the foam core layer for bonding, and the laying area is a polyurethane foam surface; the glass fiber reinforced plastic inner skin is in lap joint with the wave-absorbing stealth functional outer skin, 2 layers of low-temperature curing adhesive films are laid in the middle of the glass fiber reinforced plastic inner skin and bonded, and the laying area is a lap joint area of the glass fiber reinforced plastic inner skin and the wave-absorbing stealth functional outer skin.

5. The composite material cover body with the wave-absorbing stealth and sealing waterproof functions as claimed in claim 1, wherein a wear-resistant layer is arranged on the surface of the lower working surface of the composite material cover body, and white carbon black with the resin mass ratio of 3% is added in the wear-resistant layer.

6. A preparation method of the composite material cover body with the wave-absorbing stealth and sealing waterproof functions, which is characterized by comprising the following steps:

step 1, manufacturing an outer skin forming die, and forming the wave-absorbing stealth outer skin through the die;

step 2, laying glass fiber cloth, carbon fiber cloth and a wave-absorbing felt in an inner cavity of an outer skin forming die according to a design sequence, curing and forming through a resin vacuum introduction process, maintaining the outer skin with the wave-absorbing stealth function in the die after curing, and polishing burrs and the inner surface;

step 3, foaming polyurethane foam in the inner cavity of the wave-absorbing stealth functional outer skin by means of a foam pressing plate tool;

and 4, performing adhesive film and prepreg laying on the surface of the lap joint edge of the polyurethane foam and the wave-absorbing stealth functional outer skin, then integrally curing and molding the inner skin, and demolding after curing to obtain the composite material cover body.

7. The method for preparing the composite material cover body with the wave-absorbing stealth and sealing waterproof functions according to claim 6, wherein in the step 2, a slow flow guide net is adopted in a resin vacuum introduction process, the flow guide net is lapped for 5-15 mm, and the width of the glue blocking belt is 70-100 mm; the glue injection pipeline is arranged to be laid along the 50mm circumference from the outer edge of the lower working surface, the transverse center line position of the window stop block is laid, and the air suction pipeline is arranged to be laid along the shape of 30mm from the outer edge of the reference surface A.

8. The method for preparing a composite material cover with the functions of wave-absorbing stealth and sealing waterproof according to claim 6, characterized in that in the step 2, pressure maintaining is carried out before resin vacuum introduction, wherein the vacuum pressure is less than or equal to-95 KPa, and the pressure rise is not more than 0.5KPa after 5min of pressure maintaining; the resin vacuum introduction process is to keep the vacuumizing state for curing for more than 24 hours, and the ambient temperature in the curing process is 25 +/-5 ℃.

9. The method for preparing the composite material cover body with the wave-absorbing stealth and sealing waterproof functions of claim 6, wherein in the step 3, polyurethane foam is foamed by adopting a spraying and pouring process, the corner region of the inner cavity of the outer skin with the stealth function is foamed by adopting the spraying process, and after the corner region is completely filled, the inner cavity is integrally foamed by adopting the pouring process.

10. The method for preparing a composite material cover body with the wave-absorbing stealth and sealing waterproof functions according to claim 6, characterized in that in the step 4, an OOA process is adopted for forming the inner skin, pressure maintaining is carried out before curing, the vacuum pressure is less than or equal to-95 KPa, and the air leakage rate is less than or equal to 1 KPa/min; the curing process is to initially vacuumize and pressurize, control the curing temperature to be 80 plus or minus 5 ℃, preserve heat for 6 hours, and increase the temperature rate to be 20 plus or minus 5 ℃.