CN118683079A - Hollow structural part mold and preparation method of composite material special-shaped hollow structural part - Google Patents

Abstract

The present invention relates to the field of composite material structure forming technology, and in particular to a hollow structural part mold and a method for preparing composite material special-shaped hollow structural parts. The mold is customized according to the hollow structural part, and reinforcing rib grooves are left on the inner cavity surfaces of the upper mold body and the lower mold body. The upper mold body and the lower mold body are limitedly connected by guide pillars; the end baffle and the front baffle respectively fix the two ends of the airbag core mold and connect them to the two ends of the mold body; the upper cover plate and the lower cover plate are installed on the outside of the upper mold body and the lower mold body. The method for preparing composite material special-shaped hollow structural parts is: cleaning the mold, laying silicone mold tape on the surface of the airbag core mold; cutting carbon fiber prepreg; laying prepreg layers; laying reinforcing ribs in the reinforcing rib grooves of the mold body; closing the mold body; coating the mold, heating and curing; removing the coating material and the mold; heating the airbag core mold; and removing the airbag core mold. The present invention realizes the molding and manufacturing of composite material special-shaped hollow structural parts, and the internal quality and dimensional accuracy meet the index requirements.

Description

Hollow structural part mold and preparation method of composite material special-shaped hollow structural part

Technical Field

The invention relates to the field of composite material structure forming technology, in particular to a hollow structural part mold and a method for preparing a composite material special-shaped hollow structural part.

Background Art

The application of advanced resin-based composite materials in the main load-bearing structures in my country's aerospace field has developed very rapidly and has been widely used in rocket body structural systems, effectively supporting the efficient load-bearing and structural weight reduction of key models in my country's aerospace field. At present, the basic characteristics of the structural design of advanced resin-based composite materials in my country's aerospace field are large size, complex shape, and emphasis on integrity, which puts forward higher requirements on manufacturing technology, especially for complex multi-cavity/multi-surface structures. It is difficult to effectively solve the manufacturing accuracy and overall molding problems by relying on traditional combined mold preparation processes. At the same time, there are technical bottlenecks such as low molding efficiency and limited component size. It is urgent to carry out high-precision and overall manufacturing process research on composite materials for key structures of launch vehicles and spacecraft.

Complex hollow structures have many matching surfaces and complex structures. In the preparation process of traditional metal modular molds, due to the problem of pressurization, the internal corners, variable cross-sections and other complex parts of the product are prone to delamination defects (sags, bulges, wrinkles), uneven density, poor surface quality and other problems. The internal quality and dimensional accuracy are not easy to guarantee, which seriously affects the manufacturability and performance of complex multi-cavity composite hollow structures. In addition, hollow composite structural parts often use negative mold manual laying, which is cumbersome to operate, small space, difficult to position, difficult to guarantee the quality of laying, and a long laying cycle.

Summary of the invention

The technical problem to be solved by the present invention is to provide a hollow structural part mold and a method for preparing a composite material special-shaped hollow structural part, thereby realizing the molding and manufacturing of composite material special-shaped hollow structural parts, and the internal quality and dimensional accuracy of the product meet the index requirements.

The present invention provides a hollow structural part mold, which is customized according to the hollow structural part, and includes an upper cover plate, an upper mold body, an airbag core mold, an end baffle plate, a front baffle plate, a guide column, a lower mold body, and a lower cover plate;

Reinforcement grooves are left on the inner surface of the upper mold body and the lower mold body, and the upper mold body and the lower mold body are limitedly connected by guide pillars;

The end baffle and the front baffle respectively fix the two ends of the airbag core mold and are connected to the two ends of the mold body composed of the upper mold body and the lower mold body;

The upper cover plate and the lower cover plate are installed on the outer sides of the upper mold body and the lower mold body.

Preferably, the airbag core mold is formed by uncured polymer memory material and is designed according to the inner cavity size of the hollow structural part. The front end of the airbag core mold is a circular cavity and the end is an oblong cavity. The airbag core mold skin is 5 to 10 mm thick, and a 30 to 50 mm layup margin is left at both ends.

Preferably, the airbag core mold is prepared by an airbag forming mold.

The inner cavity size of the airbag molding mold = the net inner cavity size of the hollow structural part - (actual thickness of the layer - theoretical thickness of the layer) - (0.2mm~0.4mm).

Preferably, the structure of the airbag forming mold is:

It includes an upper cover plate of an airbag forming mold, an upper mold body of an airbag forming mold, a guide column of an airbag forming mold, a lower mold body of an airbag forming mold, and a lower cover plate of an airbag forming mold;

The mold is an external female mold. The upper mold body and the lower mold body of the airbag molding mold are cylinders welded with steel plates, with an external ring rib structure. There are lifting points on both sides of the mold body. The upper mold body and the lower mold body of the airbag molding mold are limitedly connected through the airbag molding mold guide column.

An upper cover plate of the airbag forming mold is installed on the outer side of the upper mold body of the airbag forming mold, and a lower cover plate of the airbag forming mold is installed on the outer side of the lower mold body of the airbag forming mold;

The thickness of the upper cover plate of the airbag forming mold and the lower cover plate of the airbag forming mold are both 2 to 5 mm.

Preferably, the preparation method of the airbag core mold is:

Step 1: Customize the airbag forming mold according to the size of the hollow structural part, including the upper cover plate of the airbag forming mold, the upper mold body of the airbag forming mold, the guide pillar of the airbag forming mold, the lower mold body of the airbag forming mold, and the lower cover plate of the airbag forming mold. The mold is a female mold. The upper mold body of the airbag forming mold and the lower mold body of the airbag forming mold are limitedly connected through the guide pillar of the airbag forming mold and fixed with bolts;

Step 2: Separate the upper cover plate of the airbag forming mold, the upper mold body of the airbag forming mold, the guide pillar of the airbag forming mold, the lower mold body of the airbag forming mold, and the lower cover plate of the airbag forming mold in step 1, clean the working surface of the mold, and apply a release agent on the surface for at least 3 times, with an interval of more than 20 minutes between each time;

Step 3, cutting the airbag sheet according to the size of the airbag core mold structure, and placing it in an oven to heat and soften;

Step 4: Lay the heated airbag sheet in step 3 on the upper mold body of the airbag forming mold and the cavity of the lower mold body of the airbag forming mold;

Step 5, the upper mold body of the airbag forming mold and the lower mold body of the airbag forming mold are butted together through the guide pillars of the airbag forming mold, and the airbag sheets of the mold bodies are overlapped;

Step 6: The airbag sheet in step 5 is entirely coated, the coating material passes through the inner cavity of the airbag forming mold, is evacuated, and is placed in an autoclave for heating and curing;

Step 7: After the airbag forming mold cools to room temperature, demould it, remove the coating material, gradually dismantle the airbag forming mold, obtain the airbag core mold, and clean up the excess on the surface.

The present invention provides a method for preparing a composite material special-shaped hollow structural member, comprising the following steps:

Step 1: clean the hollow structural part mold according to any one of claims 1 to 5, and apply a release agent on its working surface at least 3 times, with an interval of more than 20 minutes between each time;

Step 2: Wipe the surface of the airbag core mold clean, lay a layer of silicone mold tape on the surface and apply epoxy resin primer, and let it dry;

Step 3: Cut the carbon fiber prepreg according to the size characteristics of the hollow structural parts;

Step 4: Laying the prepreg material of the structural component skin on the surface of the airbag core mold according to a preset laying order;

Step 5: laying circumferential reinforcing ribs (4) in the reinforcing rib grooves on the inner cavity surfaces of the upper mold body and the lower mold body, and compacting and ironing the prepreg;

Step 6: Place the airbag core mold on the inner cavity of the lower mold body, and then position the upper mold body through the guide column to achieve mold closing, tighten the upper mold body and the lower mold body with bolts, fix the two ends of the airbag core mold with the end baffle and the front baffle respectively, connect them to the mold body with bolts, and install the upper cover plate and the lower cover plate in place;

Step 7: Wrap the product, pass through the inner cavity of the airbag core mold, package the product, evacuate, and place the hollow structural part mold in an autoclave for heating and curing;

Step 8: After the temperature of the hollow structural part mold drops to room temperature, the coating material is cleaned, the upper cover plate, the lower cover plate, the end baffle plate, the front baffle plate, the upper mold body, and the lower mold body are removed to obtain the airbag core mold (10) and the hollow structural part, and heat them;

Step 9: While hot, pull out the softened airbag core mold from the front end of the product to obtain the hollow structural part and clean it.

Preferably, in step 2, the silicone mold tapes overlap by 5 to 10 mm, and no bulges or protrusions are allowed.

Preferably, in step 4, the generatrix direction of the airbag core mold is 0° direction, ensuring that the mold is 0°

The direction is consistent with the 0° direction of the prepreg. The unidirectional prepreg adopts the butt joint direction. The fabric prepreg adopts the overlap form with an overlap width of 15 to 20 mm. The prepreg should be compacted when paving to drive away the bubbles between the layers. Vacuum pre-compact every 3 to 4 layers.

Preferably, in step seven, the parameters for heating and curing are: vacuuming at room temperature, pressurizing to 0.6±0.02MPa, maintaining pressure for 10 minutes, if the vacuum gauge value is ≥-0.095MPa, resealing is required, if the vacuum gauge value is ≤-0.095MPa, pressurizing is stopped; heating at a heating rate of 20-30℃/h, keeping warm at 130±5℃ for 1h, pressurizing to 0.6±0.02MPa at 130℃, stopping vacuum and keeping warm for 4h at 180±5℃; cooling to 60℃ at a cooling rate of ≤20℃/h, stopping the machine and unloading the can.

Preferably, in step eight, the heating parameters are: heating at a heating rate of 20-30°C/h and keeping at 90±5°C for 2h.

Compared with the prior art, the hollow structural part mold and composite material special-shaped hollow structural part preparation method of the present invention realize the high-precision preparation of composite material structural parts with complex structures and multiple inner cavity profiles. It solves the engineering problems such as the difficulty in molding special-shaped hollow structural parts, poor internal quality and dimensional accuracy. Through the laying of the airbag core mold and the positive mold, it solves the problems of cumbersome operation of traditional manual laying of negative film, difficulty in operation due to narrow space, difficulty in ensuring the laying quality, and long laying cycle. Through the research of airbag-assisted molding, it realizes the laying of complex hollow structural parts by airbag positive mold at room temperature, high-temperature airbag expansion and pressurization curing, and medium-temperature airbag softening and demolding, solving the problems of complex mold assembly and difficult demolding.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram showing the structure of a hollow structural member;

FIG2 is a schematic diagram showing the split structure of a hollow structural component mold;

FIG3 is a schematic diagram showing the structure of a hollow structural member mold;

Fig. 4 shows a schematic diagram of an airbag core mold;

FIG5 is a schematic diagram showing the disassembly structure of the airbag forming mold;

FIG6 is a schematic diagram showing the structure of an airbag forming mold;

In the figure,

1-front end of hollow structural part, 2-end, 3-skin of hollow structural part, 4-reinforcement ribs, 5-front end of airbag core mold, 6-end of airbag core mold, 7-skin of airbag core mold, 8-upper cover of airbag forming mold, 9-upper mold body of airbag forming mold, 10-airbag core mold, 11-guide column of airbag forming mold, 12-lower mold body of airbag forming mold, 13-lower cover of airbag forming mold, 14-upper cover, 15-upper mold body, 16-hollow structural part, 17-end baffle, 18-front end baffle, 19-guide column, 20-lower mold body, 21-lower cover.

DETAILED DESCRIPTION

In order to further understand the present invention, the embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the present invention.

The hollow structural member described in the present invention is a composite material air inlet duct structural member, and its structure is shown in Figure 1. The front end 1 of the composite material air inlet duct structural member is a circular cavity with an inner diameter of 102.48 mm, which gradually transitions to an oblong cavity with an outer radius of 30.00 mm and a side length of 120.00 mm at the end 2. The skin 3 of the hollow structural member is 1.00 mm thick, and there are three reinforcing ribs 4 with a width of 10.00 mm and a thickness of 4.00 mm on the outside, and the reinforcing ribs are spaced 130.00 mm apart.

Since the hollow structural member has a complex structure, a mold and a preparation method suitable for generating the hollow structural member are designed in this invention.

The embodiment of the present invention discloses a hollow structural part mold, as shown in FIG2 and FIG3, which is customized according to the shape of the hollow structural part, and includes an upper cover plate 14, an upper mold body 15, an airbag core mold 10, an end baffle plate 17, a front baffle plate 18, a guide column 19, a lower mold body 20, and a lower cover plate 21;

Reinforcement grooves are left on the inner cavity surfaces of the upper mold body 15 and the lower mold body 20, and the upper mold body 15 and the lower mold body 20 are limitedly connected by the guide column 19;

The end baffle 17 and the front baffle 18 respectively fix the two ends of the airbag core mold 10 and are connected to the two ends of the mold body composed of the upper mold body 15 and the lower mold body 20;

The upper cover plate 14 and the lower cover plate 21 are installed on the outer sides of the upper mold body 15 and the lower mold body 20 .

The mold for hollow structural parts is a metal female mold, the mold material is steel, the working surface roughness is 1.6, and the working surface air tightness requirements are: the vacuum degree is ≥0.097MPa under the specified temperature (r.t and 180℃), and the vacuum is stopped after 10min. The vacuum leakage rate is required to be ≤5KPa/min, and the scale lines are marked at both ends of the mold.

In the hollow structural part 16, as shown in Figure 4, the airbag core mold 10 is prepared by molding uncured polymer memory material and is designed according to the inner cavity size of the hollow structural part. The front end 5 of the airbag core mold is a circular cavity, and the end 6 is an oblong cavity. The airbag core mold skin 7 is 5 to 10 mm thick, and a layup margin of 30 to 50 mm is left at both ends.

The airbag core mold 10 is prepared by an airbag forming mold, and the inner cavity size of the airbag forming mold = the net inner cavity size of the hollow structural component - (actual thickness of the layer - theoretical thickness of the layer) - (0.2mm~0.4mm).

The structure of the airbag forming mold is shown in Figures 5 and 6:

It includes an upper cover plate 8 of an airbag forming mold, an upper mold body 9 of an airbag forming mold, a guide column 11 of an airbag forming mold, a lower mold body 12 of an airbag forming mold, and a lower cover plate 13 of an airbag forming mold;

The mold is an external female mold. The upper mold body 9 of the airbag molding mold and the lower mold body 12 of the airbag molding mold are cylinders welded with steel plates, with an external ring rib structure. Lifting points are arranged on both sides of the mold body. The upper mold body 9 of the airbag molding mold and the lower mold body 12 of the airbag molding mold are limitedly connected through the airbag molding mold guide column 11.

An upper cover plate 8 of the airbag forming mold is installed on the outer side of the upper mold body 9 of the airbag forming mold, and an lower cover plate 13 of the airbag forming mold is installed on the outer side of the lower mold body 12 of the airbag forming mold;

The thickness of the upper cover plate 8 of the airbag forming mold and the lower cover plate 13 of the airbag forming mold are both 2 to 5 mm.

The airbag core mold is a metal female mold, the mold material is Q235, and the mold surface roughness is 1.6. Working surface air tightness requirements: vacuum degree ≥ 0.097MPa under the specified temperature (r.t and 180℃), vacuum is stopped after 10min, and the vacuum leakage rate is required to be ≤5KPa/min.

The preparation method of the airbag core mold is:

Step 1: Customize the airbag forming mold according to the size of the hollow structural part, including the upper cover plate 8 of the airbag forming mold, the upper mold body 9 of the airbag forming mold, the guide pillar 11 of the airbag forming mold, the lower mold body 12 of the airbag forming mold, and the lower cover plate 13 of the airbag forming mold. The mold is a female mold. The upper mold body 9 of the airbag forming mold and the lower mold body 12 of the airbag forming mold are limitedly connected through the guide pillar 11 of the airbag forming mold and fixed with bolts;

Step 2: Separate the upper cover plate 8, the upper mold body 9, the guide pin 11, the lower mold body 12, and the lower cover plate 13 of the airbag forming mold in step 1, clean them with acetone or other cleaning agents, clean the working surface of the mold, and apply a release agent on the surface at least 3 times, with an interval of more than 20 minutes between each time;

Step 3: Cut the airbag sheet according to the structural dimensions of the airbag core mold 10 and heat and soften it in an oven; process parameters: heating rate 1°C/min, heating to 80-90°C, and keeping warm for 0.5-1h.

Step 4, lay the airbag sheet heated in step 3 in the cavity of the upper mold body 9 and the lower mold body 12 of the airbag forming mold; heat and shape it by hot air blowing so that the airbag sheet follows the shape of the mold, connect the upper mold body 9 and the lower mold body 12 of the airbag forming mold through the airbag forming mold guide column 11, and overlap the airbag sheet at the seam.

Step 5: The upper mold body 9 and the lower mold body 12 of the airbag forming mold are butted together through the guide pillars 11 of the airbag forming mold, and the airbag sheets of the mold bodies are overlapped;

Step 6: The airbag sheet in step 5 is entirely coated, the coating material passes through the inner cavity of the airbag forming mold, is evacuated, and is placed in an autoclave for heating and curing;

Curing parameters: heating rate 1℃/min, heating to 60℃ and keeping warm for 1h, pressurizing to 0.7Mpa and then heating to 80℃ and keeping warm for 1h, heating to 120℃ and keeping warm for 0.5h, heating to 180℃ and keeping warm for 2h, cooling to 40℃ at a cooling rate of 1℃/min, releasing the pressure and removing from the can.

Step 7: After the airbag forming mold cools down to room temperature, demould it, remove the coating material, gradually dismantle the airbag forming mold, obtain the airbag core mold 10, and clean up the excess on the surface.

The embodiment of the present invention also discloses a method for preparing a composite material special-shaped hollow structural member, comprising the following steps:

Step 1: Clean the hollow structural part mold described in the above technical solution, and apply a release agent on its working surface at least 3 times, with an interval of more than 20 minutes between each time;

The release agent is a PMR release agent.

Step 2: Wipe the surface of the airbag core mold 10 clean, lay a layer of silicone mold tape on the surface and apply epoxy resin primer, and let it dry;

The overlap between the silicone mold tapes is 5 to 10 mm, and no bulges or protrusions are allowed.

Let it stand for 20 to 40 minutes, preferably 30 minutes.

Step 3: Cut the carbon fiber prepreg according to the size characteristics of the hollow structural parts;

Specifically, the carbon fiber prepreg is cut according to the size characteristics of the hollow structural member, and an automatic blanking machine or manual cutting can be used; the composite air intake duct structural member skin (3) has a thickness of 1.00 mm, and has three circumferential reinforcing ribs (4) on the outside, with a width of 10.00 mm and a thickness of 4.00 mm. MT300-3K/603B (single layer thickness 0.15 mm) unidirectional prepreg and MT300-1K-5DW/603B (single layer thickness 0.15 mm) fabric prepreg are used. The technical indicators of the prepreg are shown in Table 1.

Table 1 Quality indicators of composite hot melt prepreg

Step 4: Laying the prepreg of the structural component skin 3 on the surface of the airbag core mold 10 according to a preset laying order;

The generatrix direction of the airbag core mold 10 is 0°, ensuring that the 0° direction of the mold is consistent with the 0° direction of the prepreg. The MT300-3K/603B unidirectional prepreg adopts the butt joint direction, and the MT300-1K-5DW/603B fabric prepreg adopts the overlap form with an overlap width of 15 to 20 mm. The prepreg should be compacted when paving to drive away the bubbles between the layers, and vacuum pre-compacted every 3 to 4 layers.

Step 5: Lay the annular reinforcing ribs 4 in the reinforcing rib grooves of the inner cavity surfaces of the upper mold body 15 and the lower mold body 20 to compact and iron the prepreg;

Use MT300-1K-5DW/603B fabric prepreg for layering, and use a pressure roller or electric iron to compact and flatten the prepreg.

Step 6: Place the airbag core mold 10 on the inner cavity of the lower mold body 20, and then position the upper mold body 15 through the guide column 19 to achieve mold clamping, tighten the upper mold body 15 and the lower mold body 20 with bolts, fix the two ends of the airbag core mold 10 with the end baffle 17 and the front baffle 18 respectively, connect them to the mold body with bolts, and install the upper cover plate 14 and the lower cover plate 21 in place;

Step 7: Wrap the product, pass through the inner cavity of the airbag core mold 10, package the product, evacuate, and place the hollow structural part mold in an autoclave for heating and curing;

The parameters for heating and curing are: vacuumize at room temperature, pressurize to 0.6±0.02MPa, maintain pressure for 10 minutes, if the vacuum gauge value is ≥-0.095MPa, reseal, if the vacuum gauge value is ≤-0.095MPa, stop pressurizing; heat up at a heating rate of 20-30℃/h, keep warm at 130±5℃ for 1h, pressurize to 0.6±0.02MPa at 130℃, stop vacuum and keep warm for 4h at 180±5℃; cool to 60℃ at a cooling rate of ≤20℃/h, stop the machine and remove from the can.

Step 8: After the temperature of the hollow structural part mold drops to room temperature, clean the coating material, remove the upper cover plate 14, the lower cover plate 21, the end baffle plate 17, the front baffle plate 18, the upper mold body 15, and the lower mold body 20, obtain the airbag core mold 10 and the hollow structural part 16, and heat them;

The heating parameters are: heating at a rate of 20 to 30°C/h and keeping at 90±5°C for 2h.

Step nine: While still hot, pull out the softened airbag core mold 10 from the front end of the product to obtain the hollow structural part 16, and clean it.

Ultrasonic testing was used to perform non-destructive testing on the product, and no defects such as delamination, looseness, and inclusions were found. The product size met the requirements, and rapid prototyping of the product's net size was achieved.

The above embodiments are only used to help understand the method and core idea of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. The hollow structural member mould is characterized by comprising an upper cover plate (14), an upper mould body (15), an air bag core mould (10), a tail end baffle (17), a front end baffle (18), a guide post (19), a lower mould body (20) and a lower cover plate (21), wherein the hollow structural member mould is customized according to a hollow structural member;

reinforcing rib grooves are reserved on the inner cavity molded surfaces of the upper die body (15) and the lower die body (20), and the upper die body (15) and the lower die body (20) are in limit butt joint through guide posts (19);

The end baffle (17) and the front end baffle (18) respectively fix the two ends of the airbag core mould (10) and are connected with the two ends of the mould body formed by the upper mould body (15) and the lower mould body (20);

the upper cover plate (14) and the lower cover plate (21) are arranged on the outer sides of the upper die body (15) and the lower die body (20).

2. The hollow structural member mould according to claim 1, wherein the airbag core mould (10) is formed by uncured polymer memory material, and is designed according to the size of the inner cavity of the hollow structural member, the front end (5) of the airbag core mould is a circular cavity, the tail end (6) of the airbag core mould is an oblong cavity, the thickness of the airbag core mould skin (7) is 5-10 mm, and the two ends of the airbag core mould skin are provided with a layering allowance of 30-50 mm.

3. The hollow structural member mold according to claim 1, wherein the balloon core mold (10) is prepared from a balloon molding mold,

Air bag forming die cavity size = hollow structural member cavity net size- (actual thickness of layer-theoretical thickness of layer) - (0.2 mm-0.4 mm).

4. A hollow structural member mould according to claim 3 wherein the balloon forming mould is of the structure:

The device comprises an air bag forming die upper cover plate (8), an air bag forming die upper die body (9), an air bag forming die guide post (11), an air bag forming die lower die body (12) and an air bag forming die lower cover plate (13);

The mould is a vulva mould, the upper mould body (9) of the air sac forming mould and the lower mould body (12) of the air sac forming mould are cylinders welded by steel plates, the outer part is provided with a ring rib structure, the two sides of the mould body are provided with hanging points, the upper mould body (9) of the air sac forming mould and the lower mould body (12) of the air sac forming mould are in limit butt joint through guide posts (11) of the air sac forming mould,

An air bag forming die upper cover plate (8) is arranged at the outer side of the air bag forming die upper die body (9), and an air bag forming die lower cover plate (13) is arranged at the outer side of the air bag forming die lower die body (12);

the thickness of the upper cover plate (8) of the air bag forming die and the lower cover plate (13) of the air bag forming die is 2-5 mm.

5. The hollow structural member mold of claim 4 wherein the method of making the balloon mandrel is:

The method comprises the steps that firstly, air bag forming die customization is carried out according to the size of a hollow structural member, wherein the air bag forming die customization comprises an air bag forming die upper cover plate (8), an air bag forming die upper die body (9), an air bag forming die guide post (11), an air bag forming die lower die body (12) and an air bag forming die lower cover plate (13), the die is an outer female die, the air bag forming die upper die body (9) and the air bag forming die lower die body (12) are in limiting butt joint through the air bag forming die guide post (11), and the air bag forming die upper die body and the air bag forming die lower die body are fixed through bolts;

Step two: the air bag forming die upper cover plate (8), the air bag forming die upper die body (9), the air bag forming die guide post (11), the air bag forming die lower die body (12) and the air bag forming die lower cover plate (13) in the first step are disassembled, the working face of the die is cleaned, the surface is coated with a release agent for at least 3 times, and the time interval between each time is more than 20 minutes;

cutting the air bag sheet according to the structural size of the air bag core mould (10), and putting the air bag sheet into an oven for heating and softening;

fourthly, paving the airbag sheet heated in the third step in the cavity of an upper die body (9) of an airbag forming die and a lower die body (12) of the airbag forming die;

Step five, butt-jointing an upper die body (9) of the air bag forming die and a lower die body (12) of the air bag forming die through guide posts (11) of the air bag forming die, and performing lap joint treatment on the air bag sheets in the joints by the die bodies;

Step six, the airbag sheet material in the step five is integrally coated, the coating material passes through the inner cavity of the airbag forming die, the vacuum is pumped, and the airbag sheet material is placed into an autoclave for heating and curing;

And seventhly, demolding after the air bag forming die is cooled to room temperature, removing the coating material, gradually removing the air bag forming die to obtain an air bag core die (10), and cleaning off superfluous surface.

6. The preparation method of the composite special-shaped hollow structural member is characterized by comprising the following steps of:

Step one: cleaning the hollow structural member mould according to any one of claims 1 to 5, and coating a release agent on the working surface of the hollow structural member mould for at least 3 times, wherein the time interval between each time is more than 20 minutes;

step two: wiping the surface of an air bag core mold (10), paving a layer of silica gel mold adhesive tape on the surface, brushing epoxy resin primer, and airing;

Step three: cutting the carbon fiber prepreg according to the size characteristics of the hollow structural member;

step four: performing prepreg layering on the structural member skin (3) on the surface of the airbag core mold (10) according to a preset layering sequence;

step five: annular reinforcing ribs (4) are paved in reinforcing rib grooves of inner cavity profiles of the upper die body (15) and the lower die body (20), and prepregs are compacted and ironed;

Step six: placing an airbag core mould (10) on an inner cavity of a lower mould body (20), positioning an upper mould body (15) through a guide pillar (19) to realize mould closing, screwing the upper mould body (15) and the lower mould body (20) by bolts, respectively fixing two ends of the airbag core mould (10) by a tail end baffle (17) and a front end baffle (18), connecting the two ends on the mould body by bolts, and installing an upper cover plate (14) and a lower cover plate (21) in place;

Step seven: coating a product, penetrating through the inner cavity of an air bag core mold (10), packaging the product, vacuumizing, and placing a hollow structural member mold in an autoclave for heating and curing;

Step eight: after the temperature of the hollow structural member mould is reduced to room temperature, cleaning up a coating material, removing an upper cover plate (14), a lower cover plate (21), a tail end baffle plate (17), a front end baffle plate (18), an upper die body (15) and a lower die body (20), and obtaining an air bag core die (10) and a hollow structural member (16), and heating the air bag core die and the hollow structural member;

step nine: and (5) extracting the softened air bag core mould (10) from the front end of the product while the air bag core mould is hot to obtain a hollow structural member (16), and cleaning the hollow structural member.

7. The method for preparing a profiled hollow structural member made of composite material according to claim 6, wherein in the second step, the silicone rubber strips are overlapped by 5-10 mm, and no bulge or bulge is allowed.

8. The method for manufacturing the special-shaped hollow structural member made of the composite material according to claim 6, wherein in the fourth step, the direction of a bus of the air bag core mold (10) is 0 DEG, the 0 DEG direction of the mold is guaranteed to be consistent with the 0 DEG direction of the prepreg, the unidirectional prepreg is in a butt joint direction, the fabric prepreg is in a lap joint mode, the lap joint width is 15-20 mm, compaction is guaranteed when the prepreg is paved, interlayer bubbles are removed, and vacuumizing and pre-compaction are carried out every 3-4 layers.

9. The method for preparing a profiled hollow structural member made of composite material according to claim 6, wherein in the seventh step, parameters of heat curing are as follows: vacuumizing at room temperature, pressurizing to 0.6+/-0.02 MPa, maintaining the pressure for 10min, sealing again if the vacuum gauge value is more than or equal to-0.095 MPa, and stopping pressurizing if the vacuum gauge value is less than or equal to-0.095 MPa; heating at a heating rate of 20-30 ℃/h, preserving heat for 1h at 130+/-5 ℃, pressurizing to 0.6+/-0.02 MPa at 130 ℃, stopping vacuum at 180+/-5 ℃ and preserving heat for 4h; cooling to 60 ℃ at a cooling rate of less than or equal to 20 ℃/h, and stopping the machine to discharge the tank.

10. The method for preparing a profiled hollow structural member made of composite material according to claim 6, wherein in the eighth step, the heating parameters are: the temperature rising speed is 20-30 ℃/h, the temperature is raised, and the temperature is kept for 2h at 90+/-5 ℃.