A method for preparing a mirror boss structure special-shaped pipe by using carbon fiber composite material

Abstract

The application discloses a method for preparing a mirror image boss structure special-shaped pipe by adopting carbon fiber composite materials, and comprises the following steps: 1, light film coating core mold; 2, pre-impregnated material coating the core mold with light film; 3, pre-impregnated material and glue film laying foam block; 4, boss block placement; 5, composite structure laying pre-impregnated material; 6, removing the core mold and placing into the air bag; 7, cleaning and preheating of the combined mold; 8, placing the prefabricated product into the lower mold; 9, combining the middle mold; 10, installing the upper mold, and carrying out inflation heating and curing; 11, adjusting the combined mold and repeating the above steps to obtain a left boss carbon fiber composite special-shaped pipe and a right boss carbon fiber composite special-shaped pipe. The application adopts mold pressing and air pressure forming, realizes single mold production of the boss structure mirror image symmetric carbon fiber composite special-shaped pipe, reduces the production cost, and solves the difficulty problem of mold entering and demolding of the carbon fiber composite special-shaped pipe with single or multiple boss structures.

Description

Technical Field

[0001] This invention belongs to the field of carbon fiber composite material product molding technology, specifically relating to a method for preparing a mirror boss structure irregular tube using carbon fiber composite material. Background Technology

[0002] Carbon fiber composite tubing is widely used in the aerospace field, especially straight circular tubing, whose manufacturing methods and applications are relatively mature. However, the application of irregularly shaped carbon fiber composite tubing is less common, and its manufacturing is one of the important challenges in its use. Most existing irregularly shaped carbon fiber composite tubing has a curved body or notched ends. These tubing can be manufactured using methods such as winding, heat shrink molding, and vacuum forming. However, for irregularly shaped tubing with single or multiple boss structures, these methods require secondary processing or secondary connection. When using compression molding, its integrated molding is limited by difficulties in placing and demolding the boss structure, difficulties in applying pressure during curing, and the connection strength between the boss structure and the tubing body. This has slowed the widespread application of such irregularly shaped tubing.

[0003] Patent CN111016015A, filed by Zhang Yujie et al. of Shanghai Composite Materials Technology Co., Ltd., discloses a mold for a composite material back rib with a recessed boss and its demolding method. This invention uses a casting method to form a composite material shell with a boss. It utilizes a high temperature, greater than or equal to the gel temperature of the composite resin, to separate the split mold from the main mold, preventing the composite material from curing. After cooling, the mold shrinks and tightens, making demolding of the composite material back rib with the recessed boss difficult. This invention can effectively improve the demolding of composite material back ribs; however, the demolding process is carried out in a high-temperature environment, requires manual operation due to the large number of split molds, and is prone to burns. Furthermore, the casting method is suitable for shell structures but not for large, irregularly shaped tubular structures.

[0004] Therefore, a method is needed to prepare irregularly shaped tubes with mirrored boss structures using carbon fiber composite materials. Summary of the Invention

[0005] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a method for preparing a carbon fiber composite material for a mirror-symmetric shaped tube with a boss structure. This method employs molding and pneumatic forming, designs a modular mold, and manufactures a mirror-symmetric carbon fiber composite shaped tube with a boss structure by replacing inlay components. The cross-section of the boss structure can be circular, rectangular, polygonal, etc. Different sizes of boss structures can be arranged on the same carbon fiber composite shaped tube, enabling the production of multiple mirror-symmetric carbon fiber composite shaped tubes with a single mold, reducing production costs, and solving the problem of difficulty in mold insertion and demolding of carbon fiber composite shaped tubes with single or multiple boss structures.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing a mirror-shaped tube with a boss structure using carbon fiber composite material, characterized in that the method includes the following steps:

[0007] Step 1: Cover the surface of the core mold with the light film and fix it to obtain the core mold covered with the light film;

[0008] Step 2: Flatly wrap the inner layer carbon fiber prepreg according to the layup design around the core mold with light film obtained in Step 1 to obtain the wrapped structure.

[0009] Step 3: Lay the thermal expansion film on the surface of the foam block, and then lay the protruding carbon fiber prepreg on the outside of the thermal expansion film according to the layup design to obtain the protruding block.

[0010] Step 4: Place the boss block obtained in Step 3 onto the covering structure obtained in Step 2 according to the design position to obtain the composite structure;

[0011] Step 5: Lay the outer layer of prepreg material with the reserved boss holes on the composite structure obtained in Step 4 according to the layup design, and lay the reinforcing layer of carbon fiber prepreg material on the boss block to obtain the preform.

[0012] Step 6: Remove the core mold from the preform obtained in Step 5, and then place the air bag into the preform to obtain a carbon fiber shaped tube preform with a boss structure.

[0013] Step 7: Assemble the combined mold, then clean and preheat it, and apply a release agent to obtain the preparation mold; the combined mold includes an upper mold, a middle mold, and a lower mold. Both the upper and lower molds have cavities for accommodating pre-products. Each pre-product cavity has a groove for placing inlay components. The inlay components are planar inlay components and boss cavity inlay components. The boss cavity and boss block have the same shape. The middle mold includes a first middle mold and a second middle mold assembled to form the outer contour of the pre-product; the assembly involves installing the planar inlay components and the boss cavity inlay components into the grooves of the upper and lower molds, respectively.

[0014] Step 8: Place the pre-made product obtained in Step 6 onto the lower mold obtained in Step 7, and press the boss block on the pre-made product into the boss cavity of the boss cavity inlay assembly to obtain the initial assembly mold.

[0015] Step 9: Close the middle layer mold from both sides of the pre-product using the initial assembly mold obtained in Step 8 to obtain the semi-assembled mold;

[0016] Step 10: Install the semi-assembled mold obtained in Step 9 onto the upper mold, and then perform gas inflation and heating curing to obtain the left boss carbon fiber composite special-shaped pipe in the combined mold.

[0017] Step 11: Adjust the combined mold of the left boss carbon fiber composite special-shaped pipe obtained in Step 10, and then repeat Step 1 to Step 10 to obtain the right boss carbon fiber composite special-shaped pipe, thus obtaining mirror-symmetrical left boss carbon fiber composite special-shaped pipe and right boss carbon fiber composite special-shaped pipe.

[0018] This invention uses a core mold to form an internal support. After flattening and covering the inner layer of carbon fiber prepreg according to the layup design, a tubular shape is initially formed. A smooth film is applied to the core mold to facilitate demolding. Foam blocks are used as internal shaping components for the boss blocks, allowing for easy processing into various shapes. A thermally expandable adhesive film is laid on the surface of the foam block, and the boss carbon fiber prepreg is then laid on the outside of the thermally expandable adhesive film according to the layup design. The thermally expandable adhesive film can expand to tens of times its original volume at high temperatures, supporting the boss carbon fiber prepreg and forming a boss structure. The prefabricated boss structure is smaller than the boss cavity of the inlaid component, facilitating individual... One or more boss structures are placed in the mold, with one or more boss blocks placed on the covering structure. The boss blocks are placed on the covering structure and the outer prepreg with the reserved boss holes is laid according to the layup design. The reinforcing carbon fiber prepreg is then laid on the boss blocks. After the outer carbon fiber prepreg and the reinforcing carbon fiber prepreg are laid in multiple layers, the boss structure is firmly connected to the main body of the shaped tube, ensuring that a strong boss structure is obtained on the final carbon fiber composite shaped tube. By removing the core mold and placing an air bag, the tubular structure is maintained by inflating the air bag in subsequent processing, ensuring the uniformity of the structure of the prepared carbon fiber composite shaped tube.

[0019] The modular mold in this invention includes an upper mold, a middle mold, a lower mold, and inlay components. The upper and lower mold cavities have relatively small depths, facilitating the overall placement and demolding of the carbon fiber composite shaped pipe. The cavities contain one or more inlay component grooves arranged according to the number of boss structures, with the groove positions of the upper and lower molds corresponding to each other. The middle mold is divided into left and right sections, with the main cavities forming the body of the carbon fiber composite shaped pipe placed from the side of the mold. This modular placement of the middle mold solves the problem of difficult overall placement of the carbon fiber composite shaped pipe and reduces the occurrence of sand inclusion defects.

[0020] In this invention, when the boss blocks are placed on the covering structure, they are evenly spaced on the same side of the pipe as required. The boss blocks and the covering structure are placed at any angle, which ensures the angle of the boss blocks on the carbon fiber composite irregular pipe, meets different application requirements, and the boss cavity of the boss cavity inlay assembly is processed to fit the boss block.

[0021] This invention involves placing a pre-formed product in a combined mold with a pre-installed planar inlay component and a boss cavity inlay component. The boss structure of the pre-formed product is pressed until it partially enters the boss cavity of the boss cavity inlay component. A middle mold is placed from both sides, the pre-formed product in the mold cavity is adjusted, and an upper mold is placed. The product is then placed in an oven for heating and pressure curing. During the gas-filled heating and curing process, pressure is uniformly applied to the inner wall of the carbon fiber composite shaped tube body through an air bag. The boss structure can be pressure-cured through the thermal expansion of the adhesive film and the boss cavity, ensuring the smooth appearance of the boss structure and the density of the prepreg. This results in an integrated molded carbon fiber composite shaped tube with a boss structure.

[0022] This invention adjusts the combined mold, changes the mold direction and flips it, the original upper mold becomes the lower mold, the original lower mold becomes the upper mold, installs the inlay component in another direction, and places the prefabricated boss structure at the corresponding position on the other side of the carbon fiber composite shaped tube, thus producing an integrated molded carbon fiber composite shaped tube with a mirror-symmetric boss structure. This solves the problems of pressure application during the curing and molding of the boss structure of the carbon fiber composite shaped tube and the connection strength between the boss structure and the tube body.

[0023] The method described above for preparing a mirror-shaped tube with a boss structure using carbon fiber composite material is characterized in that the foam block in step three is a cylinder or prism, and the size of the boss block is smaller than the boss cavity of the boss cavity inlay assembly. This invention ensures the shape of the bosses on the surface of the final carbon fiber composite tube by controlling the shape of the foam block.

[0024] The above-mentioned method for preparing a mirror-shaped tube with a boss structure using carbon fiber composite material is characterized in that, in step five, the reinforcing carbon fiber prepreg is laid in a cross-shaped manner, and the reinforcing carbon fiber prepreg overlaps with the outer prepreg of the reserved boss hole, with the overlap length gradually increasing by 15mm to 30mm. In this invention, the outer carbon fiber prepreg of the reserved boss structure hole is laid according to the layup design, and the reinforcing carbon fiber prepreg is laid in a cross-shaped manner at the boss block position, overlapping with the outer prepreg of the main body of the shaped tube, with the overlap length gradually increasing by 15mm to 30mm. After multiple layers of the outer carbon fiber prepreg and the reinforcing carbon fiber prepreg are laid in an alternating manner, the boss structure is firmly connected to the main body of the shaped tube.

[0025] The method described above for preparing a mirror-shaped tube with a boss structure using carbon fiber composite material is characterized in that the air bag described in step six is ​​soaked in a release agent before use. This invention facilitates the subsequent removal of the air bag by soaking it in the release agent.

[0026] The above-mentioned method for preparing a mirror boss structure irregular tube using carbon fiber composite material is characterized in that the preheating temperature in step seven is 70℃~80℃.

[0027] The above-described method for preparing a mirror-shaped tube with a boss structure using carbon fiber composite material is characterized in that, in step seven, the upper mold, middle mold, and lower mold are provided with mold-closing holes, and mold-closing bolts are installed in the mold-closing holes. This invention ensures a tight connection between the upper mold, middle mold, and lower mold by providing mold-closing holes and mold-closing bolts, thereby guaranteeing the structural performance of the carbon fiber composite shaped tube.

[0028] The above-mentioned method for preparing a mirrored boss structure irregular tube using carbon fiber composite material is characterized in that, in step seven, the preform cavity is a bent rectangle, the boss cavity inlay assembly is placed in the groove of the lower mold, the planar inlay assembly is placed in the groove of the upper mold, the groove is provided with a through hole, the inlay assembly is fixedly connected to the upper mold and the lower mold by fastening bolts and positioning pins, and a pad is placed at the bottom of the boss cavity in the boss cavity inlay assembly. This invention prepares carbon fiber composite shaped pipe fittings by setting the pre-form cavity as a bent rectangle. The pre-form cavity can be of various required shapes, and the shape of the mandrel corresponds to the shape of the pre-form cavity, thus producing carbon fiber composite shaped pipe fittings of different shapes. The inlay components are divided into two groups. One group is a left-side inlay component, i.e., the boss structure is on the left side of the carbon fiber composite shaped pipe fitting, including a planar inlay component and a left boss cavity inlay component. The other group is a right-side inlay component, i.e., the boss structure is on the right side of the carbon fiber composite shaped pipe fitting, including a planar inlay component and a right boss cavity inlay component. The surface of the planar inlay component is a smooth plane. The cross-section of the cavity of the left / right boss cavity inlay component is rectangular, circular, polygonal, etc. During production, a pad of a certain thickness is placed at the bottom of the boss cavity of the inlay component to ensure the appearance quality of the boss structure of the product during pressure curing and to avoid surface damage to the boss structure of the pipe fitting due to external force during demolding. By replacing the left and right inlay components, a single set of molds can produce a variety of carbon fiber shaped pipe fittings with mirror-symmetrical boss structures.

[0029] This invention involves fastening a boss-shaped cavity inlay assembly to the lower mold cavity groove with bolts, and a flat inlay assembly to the upper mold cavity groove with bolts. The boss structure of the pre-produced product faces downwards, and it is pressed until it partially enters the boss cavity of the boss-shaped cavity inlay assembly. Middle molds are placed from both sides, and the two ends of the air bag are connected to air nozzles. The pre-produced product in the mold cavity is adjusted, the upper mold is placed, and the mold closing bolts are tightened to ensure the smooth appearance of the boss structure and the density of the prepreg, thus producing an integrated molded carbon fiber composite special-shaped tube with a boss structure. During demolding, the upper mold is detached, and the two middle molds are detached in sequence. At this time, most of the main body of the carbon fiber composite special-shaped tube has been demolded. On the bottom surface of the lower mold, a flexible rod is used to apply force from the through hole to make the boss structure detach from the boss cavity of the inlay assembly, thereby achieving overall demolding of the carbon fiber composite special-shaped tube.

[0030] The above-mentioned method for preparing a mirror boss structure irregular tube using carbon fiber composite material is characterized in that, in step nine, one end of the air bag is closed, and the other end is fitted with an air nozzle and connected to an air compressor.

[0031] The above-mentioned method for preparing a mirror-shaped tube with a boss structure using carbon fiber composite material is characterized in that the parameters for gas inflation and curing in step ten are as follows: first, the air compressor is set to a pressure of 0.1 MPa to 0.3 MPa for inflation, and the temperature is raised to 80°C to 100°C; then, the air compressor is set to a pressure of 0.7 MPa to 1.0 MPa for inflation, and the temperature is maintained for 0.4 h to 0.7 h; finally, the temperature is raised to 120°C to 130°C and maintained for 1.5 h to 3 h. This invention ensures the preparation effect by controlling the parameters of gas inflation and curing.

[0032] The above-described method for preparing a mirror-symmetric boss structure shaped tube using carbon fiber composite material is characterized in that, in step eleven, the adjustment involves swapping the boss cavity inlay assembly and the planar inlay assembly in the upper and lower molds, and then swapping the upper and lower molds. This invention adjusts the combined mold, changes the mold direction and flips it, making the original upper mold the lower mold and the original lower mold the upper mold. An inlay assembly in another direction is installed, and a prefabricated boss structure is placed at a corresponding position on the other side of the carbon fiber composite shaped tube, resulting in an integrated molded carbon fiber composite shaped tube with a mirror-symmetric boss structure. This solves the problems of pressure application during the curing and molding of the boss structure in carbon fiber composite shaped tubes and the connection strength between the boss structure and the tube body.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] 1. This invention employs molding and pneumatic forming methods, designs a modular mold, and manufactures carbon fiber composite shaped tubes with mirror-symmetrical boss structures by replacing inlaid components. The cross-section of the boss structure can be circular, rectangular, polygonal, etc. Different sizes of boss structures can be arranged on the same carbon fiber composite shaped tube, realizing the production of multiple carbon fiber composite shaped tubes with mirror-symmetrical boss structures using a single set of molds, reducing production costs, and solving the problem of difficult mold insertion and demolding of carbon fiber composite shaped tubes with single or multiple boss structures.

[0035] 2. The modular mold of the present invention adopts a multi-layer combination method, which solves the problems of difficult mold insertion of the boss structure of carbon fiber composite special-shaped pipe fittings and difficult demolding of the pipe fitting body. The upper and lower mold cavities are relatively shallow, and the main cavity of the pipe fitting body is formed by two middle molds. When the pre-product is inserted into the mold, the state of the pre-product in the mold can be adjusted in time to avoid sand inclusion defects. When demolding, external force is applied through the round through holes of the upper and lower molds, which facilitates the demolding of the carbon fiber composite boss structure and facilitates the replacement of the inlay components, improves the appearance quality of the carbon fiber composite special-shaped pipe fittings, and ensures the dimensional stability of the pipe fittings.

[0036] 3. This invention utilizes the property of thermal expansion film to expand at high temperatures to prepare boss structures. At room temperature, the size of the pre-made product is smaller than the size of the cavity, which solves the problem of difficult mold insertion of boss structures. During the gas-filling and heating curing process, the thermal expansion film expands itself and forms a closed cavity with the boss cavity, which pressurizes the prepreg material covering it, thus solving the molding pressure problem of the boss structure molding process.

[0037] 4. This invention utilizes a cross-laying method to lay a reinforcing layer of carbon fiber prepreg on the boss structure and overlap it with the outer layer of prepreg of the main body of the irregular tube. The overlap length gradually increases by 15mm to 30mm. After the outer layer of carbon fiber prepreg and the reinforcing layer of carbon fiber prepreg are laid in multiple layers, the boss structure and the carbon fiber irregular tube are firmly connected and integrally formed without secondary processing steps.

[0038] 5. The boss structure of the carbon fiber composite irregular tube obtained by the present invention is connected with other mechanisms with good connection strength. Through test verification, a single boss structure can bear a load of 750N and has good mechanical properties.

[0039] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0040] Figure 1 This is an exploded view of the combined mold of the present invention.

[0041] Figure 2 This is a schematic diagram of the planar inlay component of the present invention.

[0042] Figure 3 This is a schematic diagram of the structure of the boss cavity inlay assembly of the present invention.

[0043] Figure 4 This is an exploded view of the preform obtained in Embodiment 1 of the present invention.

[0044] Figure 5 This is a schematic diagram of the mirror-symmetric left-protruding carbon fiber composite irregular tube and right-protruding carbon fiber composite irregular tube prepared in Embodiment 1 of the present invention.

[0045] Figure 6 This is a schematic diagram of the mirror-symmetrical left-protruding carbon fiber composite irregular tube and right-protruding carbon fiber composite irregular tube prepared in Embodiment 2 of the present invention.

[0046] Explanation of reference numerals in the attached figures:

[0047] 1—Upper mold; 2-1—First middle mold; 2-2—Second middle mold;

[0048] 3—Lower mold; 4—Pre-form cavity; 5—Groove;

[0049] 6—Through hole; 7—Mold closing hole; 8—Mold closing bolt;

[0050] 9—Planar inlay assembly; 10—Boss cavity inlay assembly; 10-1—Boss cavity;

[0051] 11—Locking pin; 12—Fasting bolt;

[0052] 13—Outer layer prepreg with reserved boss holes; 14—Reinforcing layer carbon fiber prepreg;

[0053] 15—Boss block; 16—Composite structure. Detailed Implementation

[0054] Example 1

[0055] This embodiment includes the following steps:

[0056] Step 1: Cover the surface of the core mold with the light film and fix it to obtain a core mold covered with the light film; the core mold is a rectangular parallelepiped with bends;

[0057] Step 2: Flatly wrap the inner layer carbon fiber prepreg according to the layup design around the core mold with the light film obtained in Step 1 to obtain the coating structure; the prepreg is T700 carbon fiber / epoxy resin prepreg.

[0058] Step 3: Lay the thermal expansion film on the surface of the foam block, and then lay the protruding carbon fiber prepreg on the outside of the thermal expansion film according to the layup design to obtain protruding block 15; the protruding block 15 consists of 4 large foam blocks with a length × width × height of 42mm × 25mm × 20mm and 2 small foam blocks with a length × width × height of 25mm × 25mm × 20mm; the foam is polymethacrylimide foam;

[0059] Step 4: Place the boss block 15 obtained in Step 3 on the covering structure obtained in Step 2 according to the design position to obtain the composite structure 16; among which, 4 large foam blocks are placed on the straight section of the covering structure, and 2 small foam blocks are placed on the bent straight section of the covering structure.

[0060] Step 5: Lay out the outer prepreg 13 with the reserved boss holes on the composite structure 16 obtained in Step 4 according to the layup design, and lay out the reinforcing carbon fiber prepreg 14 on the boss block 15, then lay out the outer prepreg 13 with the reserved boss holes again, and then lay out the reinforcing carbon fiber prepreg 14 on the boss block 15 to obtain the preform. See Figure 4 The reinforcing carbon fiber prepreg 14 is laid in a cross-shaped manner, and the reinforcing carbon fiber prepreg 14 overlaps with the outer prepreg 13 with the reserved boss hole, and the overlap length gradually increases by 20mm.

[0061] Step 6: Remove the core mold from the preform obtained in Step 5, and then place the air bag soaked in the release agent into the preform to obtain a carbon fiber shaped tube preform with a boss structure.

[0062] Step 7: Assemble the combined mold, then clean and preheat it, and apply a release agent to obtain the preparation mold; the combined mold includes an upper mold 1, a middle mold, and a lower mold 3. Both the upper mold 1 and the lower mold 3 have pre-product cavities 4 for accommodating the pre-product. The pre-product cavities 4 have grooves 5 for placing inlay components. The inlay components are a planar inlay component 9 and a boss cavity inlay component 10. The boss cavity 10-1 has the same shape as the boss block 15. The middle mold includes a first middle mold 2-1 and a second middle mold 2-2 assembled to form the outer contour of the pre-product; the assembly involves placing the planar inlay component 9 and the boss cavity inlay component... The insert components 10 are respectively installed into the grooves 5 of the upper mold 1 and the lower mold 3; the upper mold 1, the middle mold, and the lower mold 3 are provided with mold closing holes 7, and mold closing bolts 8 are installed in the mold closing holes 7; the pre-product cavity 4 is a bent rectangle, the boss cavity insert component 10 is placed in the groove 5 of the lower mold 3, the flat insert component 9 is placed in the groove 5 of the upper mold 1, the groove 5 is provided with a through hole 6, the insert components are fixedly connected to the upper mold 1 and the lower mold 3 by fastening bolts 12 and positioning pins 11, and a pad is placed at the bottom of the boss cavity 10-1 in the boss cavity insert component 10; the preheating temperature is 80℃;

[0063] Step 8: Place the pre-made product obtained in Step 6 onto the lower mold 3 obtained in Step 7, and press the boss block 15 on the pre-made product into the boss cavity 10-1 of the boss cavity inlay assembly 10 to obtain the initial assembly mold.

[0064] Step 9: Close the middle layer mold from both sides of the pre-product using the initial assembly mold obtained in Step 8 to obtain the semi-assembled mold; place both ends of the air bag at the interface of the semi-assembled mold and protect them with raw silicone, seal one end of the air bag, install an air nozzle on the other end and connect it to an air compressor.

[0065] Step 10: Install the semi-assembled mold obtained in Step 9 onto the upper mold 1, and then perform gas inflation and heating curing to obtain the left boss carbon fiber composite special-shaped pipe in the combined mold; the gas inflation and heating curing process is as follows: first, set the air compressor to a pressure value of 0.2MPa for inflation and heat up to 90℃, then set the air compressor to a pressure value of 0.8MPa for inflation and keep it at that temperature for 0.5h, then heat up to 125℃ and keep it at that temperature for 2h, turn off the heating, let it cool naturally to below 60℃, depressurize, take the mold out of the oven, then loosen the mold clamping bolts 8, remove the upper mold 1 in sequence, and separate the two middle molds from both ends, rotate the lower mold 3 180° and place it on the suspended support, use a flexible rod to apply external force to the pad placed in the boss cavity 10-1 through the round hole 6 on the lower mold 3 to demold, and finally remove the air bag;

[0066] Step 11: Adjust the combined mold of the left-protruding carbon fiber composite shaped tube obtained in Step 10, and then repeat Steps 1 to 10 to obtain the right-protruding carbon fiber composite shaped tube, thus obtaining mirror-symmetrical left-protruding and right-protruding carbon fiber composite shaped tubes. See... Figure 5 The adjustment involves swapping the inlay components of the boss cavity 10-1 and the planar inlay components 9 in the upper mold 1 and the lower mold 3, and then swapping the upper mold 1 and the lower mold 3.

[0067] Upon inspection, the carbon fiber composite shaped tube obtained in this embodiment has a cross-sectional height of 30mm, a width of 80mm, a wall thickness of 2mm, and a length of 500mm. It has a straight section with a bend, and the included angle of the bend is 123.5°. There are 6 boss structures on the right side of the tube. The cross-section of the boss structure is rectangular, of which 4 have a length, width, and height of 47mm × 30mm × 25mm, and 2 have a length, width, and height of 30mm × 30mm × 25mm.

[0068] Example 2

[0069] This embodiment includes the following steps:

[0070] Step 1: Cover the surface of the core mold with the light film and fix it to obtain a core mold covered with the light film; the core mold is rectangular.

[0071] Step 2: Flatly wrap the inner carbon fiber prepreg according to the layup design around the core mold with the light film obtained in Step 1 to obtain the coating structure; the inner carbon fiber prepreg is T700 carbon fiber / epoxy resin prepreg.

[0072] Step 3: Lay the thermal expansion film on the surface of the foam block, and then lay the protruding carbon fiber prepreg on the outside of the thermal expansion film according to the layup design to obtain the protruding block; the protruding block is 4 large foam blocks with a length × width × height of 42mm × 25mm × 20mm; the foam is polymethacrylimide foam;

[0073] Step 4: Place the four bosses obtained in Step 3 onto the covering structure obtained in Step 2 according to the design position to obtain the composite structure;

[0074] Step 5: Lay the outer layer of prepreg with the reserved boss holes on the composite structure obtained in Step 4 according to the layup design, and lay the reinforcing layer of carbon fiber prepreg on the boss block, then lay the outer layer of prepreg with the reserved boss holes again, and then lay the reinforcing layer of carbon fiber prepreg on the boss block again to obtain the preform; the reinforcing layer of carbon fiber prepreg is laid in a cross-shaped manner, and the reinforcing layer of carbon fiber prepreg overlaps with the outer layer of prepreg with the reserved boss holes, and the overlap length gradually increases by 15mm;

[0075] Step 6: Remove the core mold from the preform obtained in Step 5, and then place the air bag soaked in the release agent into the preform to obtain a carbon fiber shaped tube preform with a boss structure.

[0076] Step 7: Assemble the combined mold, then clean and preheat it, and apply a release agent to obtain the preparation mold. The combined mold includes an upper mold 1, a middle mold, and a lower mold 3. Both the upper mold 1 and the lower mold 3 have pre-product cavities 4 for accommodating the pre-product. The pre-product cavities 4 have grooves 5 for placing inlay components. The inlay components are a planar inlay component 9 and a boss cavity inlay component 10. The boss cavity 10-1 has the same shape as the boss block. The middle mold includes a first middle mold 2-1 and a second middle mold 2-2 assembled to form the outer contour of the pre-product. The assembly involves inlaying the planar inlay component 9 and the boss cavity. Component 10 is installed into the grooves 5 of the upper mold 1 and the lower mold 3 respectively; the upper mold 1, the middle mold, and the lower mold 3 are provided with mold closing holes 7, and mold closing bolts 8 are installed in the mold closing holes 7; the pre-product cavity 4 is a bent rectangle, the boss cavity inlay component 10 is placed in the groove 5 of the lower mold 3, the flat inlay component 9 is placed in the groove 5 of the upper mold 1, the groove 5 is provided with a through hole 6, the inlay component is fixedly connected to the upper mold 1 and the lower mold 3 by fastening bolts 12 and positioning pins 11, and a pad is placed at the bottom of the boss cavity 10-1 in the boss cavity inlay component 10; the preheating temperature is 70℃;

[0077] Step 8: Place the pre-made product obtained in Step 6 onto the lower mold 3 obtained in Step 7, and press the boss block on the pre-made product into the boss cavity 10-1 of the boss cavity inlay assembly 10 to obtain the initial assembly mold.

[0078] Step 9: Close the middle layer mold from both sides of the pre-product using the initial assembly mold obtained in Step 8 to obtain the semi-assembled mold; place both ends of the air bag at the interface of the semi-assembled mold and protect them with raw silicone, seal one end of the air bag, install an air nozzle on the other end and connect it to an air compressor.

[0079] Step 10: Install the semi-assembled mold obtained in Step 9 onto the upper mold 1, and then perform gas inflation and heating curing to obtain the left boss carbon fiber composite special-shaped pipe in the combined mold; the gas inflation and heating curing process is as follows: first, set the air compressor to a pressure value of 0.1MPa for inflation and heat up to 100℃, then set the air compressor to a pressure value of 1.0MPa for inflation and keep it at the temperature for 0.4h, then heat up to 130℃ and keep it at the temperature for 1.5h, turn off the heating, let it cool naturally to below 60℃, depressurize, take the mold out of the oven, then loosen the mold clamping bolts 8, remove the upper mold 1 in sequence, and separate the two middle molds from both ends, rotate the lower mold 3 180° and place it on the suspended support, use the flexible rod to apply external force to the pad placed in the boss cavity 10-1 through the round hole 6 on the lower mold 3 to demold, and finally pull out the air bag;

[0080] Step 11: Adjust the combined mold of the left-protruding carbon fiber composite shaped tube obtained in Step 10, and then repeat Steps 1 to 10 to obtain the right-protruding carbon fiber composite shaped tube, thus obtaining mirror-symmetrical left-protruding and right-protruding carbon fiber composite shaped tubes. See... Figure 6 The adjustment involves swapping the boss cavity inlay assembly 10 and the plane inlay assembly 9 in the upper mold 1 and the lower mold 3, and then swapping the upper mold 1 and the lower mold 3.

[0081] Example 3

[0082] This embodiment includes the following steps:

[0083] Step 1: Cover the surface of the core mold with the light film and fix it to obtain a core mold covered with the light film; the core mold is a rectangular parallelepiped with bends;

[0084] Step 2: Flatly wrap the inner carbon fiber prepreg according to the layup design around the core mold with the light film obtained in Step 1 to obtain the coating structure; the inner carbon fiber prepreg is T700 carbon fiber / epoxy resin prepreg.

[0085] Step 3: Lay the thermal expansion film on the surface of the foam block, and then lay the protruding carbon fiber prepreg on the outside of the thermal expansion film according to the layup design to obtain the protruding block; the protruding block consists of 4 large foam blocks with a diameter × height of 30mm × 25mm and 2 small foam blocks with a diameter × height of 25mm × 20mm; the foam is polymethacrylimide foam;

[0086] Step 4: Place the 6 protrusions obtained in Step 3 onto the covering structure obtained in Step 2 according to the design position to obtain the composite structure; among them, 4 large foam blocks are placed on the straight section of the covering structure, and 2 small foam blocks are placed on the bent straight section of the covering structure.

[0087] Step 5: Lay the outer layer of prepreg with the reserved boss holes on the composite structure obtained in Step 4 according to the layup design, and lay the reinforcing layer of carbon fiber prepreg on the boss block, then lay the outer layer of prepreg with the reserved boss holes again, and then lay the reinforcing layer of carbon fiber prepreg on the boss block again to obtain the preform; the reinforcing layer of carbon fiber prepreg is laid in a cross-shaped method, and the reinforcing layer of carbon fiber prepreg overlaps with the outer layer of prepreg with the reserved boss holes, and the overlap length gradually increases by 30mm;

[0088] Step 6: Remove the core mold from the preform obtained in Step 5, and then place the air bag soaked in the release agent into the preform to obtain a carbon fiber shaped tube preform with a boss structure.

[0089] Step 7: Assemble the combined mold, then clean and preheat it, and apply a release agent to obtain the preparation mold. The combined mold includes an upper mold 1, a middle mold, and a lower mold 3. Both the upper mold 1 and the lower mold 3 have pre-product cavities 4 for accommodating the pre-product. The pre-product cavities 4 have grooves 5 for placing inlay components. The inlay components are a planar inlay component 9 and a boss cavity inlay component 10. The boss cavity 10-1 has the same shape as the boss block. The middle mold includes a first middle mold 2-1 and a second middle mold 2-2 assembled to form the outer contour of the pre-product. The assembly involves inlaying the planar inlay component 9 and the boss cavity. Component 10 is installed into the grooves 5 of the upper mold 1 and the lower mold 3 respectively; the upper mold 1, the middle mold, and the lower mold 3 are provided with mold closing holes 7, and mold closing bolts 8 are installed in the mold closing holes 7; the pre-product cavity 4 is a bent rectangle, the boss cavity inlay component 10 is placed in the groove 5 of the lower mold 3, the flat inlay component 9 is placed in the groove 5 of the upper mold 1, the groove 5 is provided with a through hole 6, the inlay component is fixedly connected to the upper mold 1 and the lower mold 3 by fastening bolts 12 and positioning pins 11, and a pad is placed at the bottom of the boss cavity 10-1 in the boss cavity inlay component 10; the preheating temperature is 75℃;

[0090] Step 8: Place the pre-made product obtained in Step 6 onto the lower mold 3 obtained in Step 7, and press the boss block on the pre-made product into the boss cavity 10-1 of the boss cavity inlay assembly 10 to obtain the initial assembly mold.

[0091] Step 9: Close the middle layer mold from both sides of the pre-product using the initial assembly mold obtained in Step 8 to obtain the semi-assembled mold; place both ends of the air bag at the interface of the semi-assembled mold and protect them with raw silicone, seal one end of the air bag, install an air nozzle on the other end and connect it to an air compressor.

[0092] Step 10: Install the semi-assembled mold obtained in Step 9 onto the upper mold 1, and then perform gas inflation and heating curing to obtain the left boss carbon fiber composite special-shaped pipe in the combined mold; the gas inflation and heating curing process is as follows: first, set the air compressor to a pressure value of 0.3MPa for inflation and heat up to 80℃, then set the air compressor to a pressure value of 0.7MPa for inflation and keep it at that temperature for 0.7h, then heat up to 120℃ and keep it at that temperature for 3h, turn off the heating, let it cool naturally to below 60℃, depressurize, take the mold out of the oven, then loosen the mold clamping bolts 8, remove the upper mold 1 in sequence, and separate the two middle molds from both ends, rotate the lower mold 3 180° and place it on the suspended support, use a flexible rod to apply external force to the pad placed in the boss cavity 10-1 through the round hole 6 on the lower mold 3 to demold, and finally pull out the air bag;

[0093] Step 11: Adjust the combined mold of the left boss carbon fiber composite special-shaped tube obtained in Step 10, and then repeat Step 1 to Step 10 to obtain the right boss carbon fiber composite special-shaped tube, thereby obtaining mirror-symmetrical left boss carbon fiber composite special-shaped tube and right boss carbon fiber composite special-shaped tube; the adjustment is to swap the boss cavity inlay component 10 and the plane inlay component 9 in the upper mold 1 and the lower mold 3, and then swap the upper mold 1 and the lower mold 3.

[0094] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a mirror-shaped tube with a boss structure using carbon fiber composite material, characterized in that, The method includes the following steps: Step 1: Cover the surface of the core mold with the light film and fix it to obtain the core mold covered with the light film; Step 2: Flatly wrap the inner layer carbon fiber prepreg according to the layup design around the core mold with light film obtained in Step 1 to obtain the wrapped structure. Step 3: Lay the thermal expansion film on the surface of the foam block, and then lay the protruding carbon fiber prepreg on the outside of the thermal expansion film according to the layup design to obtain the protruding block. Step 4: Place the boss block obtained in Step 3 onto the covering structure obtained in Step 2 according to the design position to obtain the composite structure; Step 5: Lay the outer layer of prepreg material with the reserved boss holes on the composite structure obtained in Step 4 according to the layup design, and lay the reinforcing layer of carbon fiber prepreg material on the boss block to obtain the preform. Step 6: Remove the core mold from the preform obtained in Step 5, and then place the air bag into the preform to obtain a carbon fiber shaped tube preform with a boss structure. Step 7: Assemble the combined mold, then clean and preheat it, and apply a release agent to obtain the preparation mold; the combined mold includes an upper mold (1), a middle mold and a lower mold (3), both the upper mold (1) and the lower mold (3) are provided with pre-product cavities (4) for accommodating pre-products, the pre-product cavities (4) are provided with grooves (5) for placing inlay components, the inlay components are a planar inlay component (9) and a boss cavity inlay component (10), the boss cavity (10-1) is the same shape as the boss block, the middle mold includes a first middle mold (2-1) and a second middle mold (2-2) assembled into the outer contour of the pre-product; the assembly is to install the planar inlay component (9) and the boss cavity inlay component (10) into the grooves (5) of the upper mold (1) and the lower mold (3) respectively; Step 8: Place the pre-made product obtained in step 6 onto the lower mold (3) obtained in step 7, and press the boss block on the pre-made product into the boss cavity (10-1) of the boss cavity inlay assembly (10) to obtain the initial assembly mold; Step 9: Close the middle layer mold from both sides of the pre-product using the initial assembly mold obtained in Step 8 to obtain the semi-assembled mold; Step 10: Install the semi-assembled mold obtained in step 9 into the upper mold (1), and then perform gas inflation and heating curing to obtain the left boss carbon fiber composite special-shaped pipe in the combined mold. Step 11: Adjust the combined mold of the left boss carbon fiber composite special-shaped pipe obtained in Step 10, and then repeat Step 1 to Step 10 to obtain the right boss carbon fiber composite special-shaped pipe, thus obtaining mirror-symmetrical left boss carbon fiber composite special-shaped pipe and right boss carbon fiber composite special-shaped pipe.

2. The method for preparing a mirror-shaped tube with a boss structure using carbon fiber composite material according to claim 1, characterized in that, The foam block mentioned in step three is a cylinder or prism, and the size of the boss block is smaller than the boss cavity (10-1) of the boss cavity inlay assembly (10).

3. The method for preparing a mirror-shaped tube with a boss structure using carbon fiber composite material according to claim 1, characterized in that, In step five, the reinforcing carbon fiber prepreg is laid in a cross-shaped manner, and the reinforcing carbon fiber prepreg overlaps with the outer prepreg with the reserved boss hole, and the overlap length gradually increases from 15mm to 30mm.

4. The method for preparing a mirrored boss structure irregular tube using carbon fiber composite material according to claim 1, characterized in that, The air bag described in step six is ​​soaked in a release agent before use.

5. The method for preparing a mirror-shaped tube with a boss structure using carbon fiber composite material according to claim 1, characterized in that, The preheating temperature mentioned in step seven is 70℃~80℃.

6. The method for preparing a mirrored boss structure irregular tube using carbon fiber composite material according to claim 1, characterized in that, In step seven, the upper mold (1), middle mold and lower mold (3) are provided with mold closing holes (7), and mold closing bolts (8) are installed in the mold closing holes (7).

7. The method for preparing a mirror-shaped tube with a boss structure using carbon fiber composite material according to claim 1, characterized in that, In step seven, the preform cavity (4) is a bent rectangle. The boss cavity inlay assembly (10) is placed in the groove (5) of the lower mold (3). The planar inlay assembly (9) is placed in the groove (5) of the upper mold (1). A through hole (6) is provided on the groove (5). The inlay assembly is fixedly connected to the upper mold (1) and the lower mold (3) by fastening bolts (12) and positioning pins (11). A pad is placed at the bottom of the boss cavity (10-1) in the boss cavity inlay assembly (10).

8. The method for preparing a mirror-shaped tube with a boss structure using carbon fiber composite material according to claim 1, characterized in that, In step nine, one end of the air bag is sealed, and the other end is fitted with an air nozzle and connected to an air compressor.

9. A method for preparing a mirror-shaped tube with a boss structure using carbon fiber composite material according to claim 8, characterized in that, The parameters for inflation, heating and curing described in step ten are as follows: First, inflate the air compressor to a pressure of 0.1MPa to 0.3MPa and heat it to 80℃ to 100℃. Then, inflate the air compressor to a pressure of 0.7MPa to 1.0MPa and keep it at that temperature for 0.4h to 0.7h. Next, heat it to 120℃ to 130℃ and keep it at that temperature for 1.5h to 3h.

10. A method for preparing a mirror-shaped tube with a boss structure using carbon fiber composite material according to claim 7, characterized in that, The adjustment described in step eleven involves swapping the boss cavity inlay assembly (10) and the plane inlay assembly (9) in the upper mold (1) and the lower mold (3), and then swapping the upper mold (1) and the lower mold (3).

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