A composite material pipe with a complex interface structure and a preparation method thereof

Abstract

The present invention provides a composite material tube with a complex interface structure and a preparation method thereof. The preparation method includes: surface treating a metal tube; designing the laying angles and sequences of prepregs based on a bionic structure, and calculating and determining the orientations, sizes and quantities of carbon fiber / epoxy resin prepregs for each layer, and obtaining prepreg tapes by numerical control cutting; manually pre-laying prepreg tapes on the surface of the metal tube; using an automatic tube rolling machine for roller rolling. Each time a symmetric cycle of prepreg layers is rolled, the number of roller passes needs to be increased once; heating and curing the rolled core tube blank to obtain a primary composite core tube; laying a film adhesive on the surface of the primary composite core tube, positioning multiple core tubes with the film adhesive laid thereon and then assembling them, filling ridge-shaped prepreg twisted wire strips into the ridge-shaped gaps of the positioned core tube assembly, and then covering prepreg tapes on the outer layer of the core tube assembly, compacting them with rollers, and heating and curing to obtain a secondary composite material tube with a complex interface structure.

Description

Technical Field

[0001] The present invention relates to the technical field of material preparation processes, and in particular to a bionic structure design of a bionic structure tube made of carbon fiber / epoxy resin composite and a preparation method thereof. Background Art

[0002] With the continuous development of technology, the industry has put forward increasing requirements for the performance of materials, and single materials have been difficult to meet the required special or comprehensive performance. On the one hand, structural materials are required to have characteristics such as high stiffness, high strength, light weight, and good high-temperature stability. On the other hand, functional materials are required to integrate multiple characteristics such as heat, chemistry, electricity, and magnetism. Carbon fiber / resin-based composites have excellent properties such as high specific strength, specific stiffness, and specific modulus, and can be widely used in fields such as automobiles and aerospace. Among them, composite box girders with thin-walled structures are widely used in aerospace structural components. However, the traditional thin-walled structures have limited stiffness and strength, and are prone to local buckling, resulting in structural instability and accidents.

[0003] In aerospace structures, thin-walled structures (tubes, beams, rods) are a typical aircraft load-bearing and energy-absorbing structure. Improving their mechanical properties while reducing weight is of great importance and has scientific research and strategic significance. In recent years, the commonly used thin-walled structure is the aluminum space frame (ASF). However, the ASF has the disadvantages of low stiffness and strength, and is not sufficient to maintain the strain concentration applied to it. In order to improve the weaknesses of this metal space frame, aluminum composite hybrid tube beams have attracted people's attention. For this kind of composite material-reinforced metal structure, researchers first proposed winding composite materials on thin-walled metal tubes, that is, making composite material-reinforced metal tubes, to further improve the energy absorption capacity and energy absorption characteristics of thin-walled pipe fittings.

[0004] However, there are still many problems in the existing composite material tubes, beams and rod structures, such as the inability to balance the coordinated cooperation of strength, stiffness and toughness. The greater the stiffness, the more obvious the load-bearing capacity of the structure and the blocking effect on transient loads, but the corresponding deformation amount before its failure will decrease, affecting the toughness and collision compatibility of the overall structure. At the same time, in the face of complex multi-form loads, due to the strong anisotropy of simple composite material-metal structures, they often only have strong mechanical properties in one direction and cannot perfectly cope with tensile, bending, compression and torsional loads at the same time. Therefore, these elements must be optimized synergistically. And bionics provides researchers with a new and reliable way to solve the above problems.

[0005] Among a variety of materials, biomaterials possess versatility, most commonly mechanical properties, enhancing the stiffness, strength, and toughness of materials. The macro- and micro-structures of biomaterials are of great guiding significance for the structural design optimization of human engineering materials. Through cross-scale analysis of the structures of lightweight / high-strength / high-stiffness biomaterials, the coupling elements of the structural characteristics of biomaterials are condensed to achieve optimal coordination of mechanical properties and structural quality. This patent uses aluminum alloys, reinforced fiber / polymer composites, resins, and aluminum alloy porous foam materials, etc. as basic constituent units, and adopts the composite concept of multi-unit multi-level nested structures to design and manufacture several lightweight, high-strength, bionic structural composite box girders with designable shapes and mechanical properties. Summary of the Invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a tubular composite material with a complex cross-sectional structure and its preparation method. Taking the structures of natural organisms and engineering optimized structures as references, fiber composite materials are nested and compounded with metal tubes to obtain an aviation-grade composite material-reinforced metal structure, which simultaneously has excellent properties such as low density, high strength, and high stiffness. The special complex cross-sectional structure enables the material to have higher specific strength, specific stiffness, and fatigue resistance.

[0007] To achieve the above object, the following solutions are now proposed:

[0008] On the one hand, a preparation method of a composite material tube with a complex interface structure is provided, including:

[0009] Step S110, performing surface treatment on the metal tube;

[0010] Step S120, designing the laying angles and sequences of prepregs based on the bionic structure, and calculating and determining the orientations, sizes, and quantities of carbon fiber / epoxy resin prepregs for each layer, and numerically controlled cutting to obtain prepreg tapes;

[0011] Step S130, manually pre-laying the prepreg tapes on the surface of the treated metal tube to position the laying positions;

[0012] Step S140, using an automatic tube winding machine to perform roller winding on the metal tube after pre-laying is completed. For each symmetric cycle of prepreg laying, the number of roller passes needs to be increased once;

[0013] Step S150, heating and curing the core tube blank of the wound composite material metal tube to obtain a hollow primary composite material core tube;

[0014] Step S160: Lay a glue film on the surface of the primary composite material core tube. Then, use a right-angle reference platform to position and assemble multiple core tubes with the glue film laid on them, and fill the ridge-shaped voids of the assembled core tube assembly with ridge-shaped prepreg twisted yarn strips. After that, wrap a prepreg tape around the outer layer of the assembled core tube assembly and compact it using a pressure roller. After heating and curing, a secondary composite material tube with a complex interface structure is obtained.

[0015] Preferably, after step S160, it further includes: Position and assemble a certain number of secondary composite material tubes in a square array and fix their positions. Then, wrap a prepreg tape around the outer layer of the assembled structure and compact it using a pressure roller. After heating and curing, a tertiary composite material tube with a complex interface structure is obtained. And so on, to prepare an N-level composite material tube, where N > 3.

[0016] Preferably, the metal tube is a hollow aluminum tube or a steel tube.

[0017] Preferably, the method of step S110 includes: Wipe the metal tube with an acid-base solution to remove grease, protective layer, scale, severe rust and other attachments on the surface of the metal tube. Then, clean it with an alcohol solution, and use sandpaper to polish the surface of the metal tube to make it smooth. After that, clean and dry the surface with alcohol.

[0018] Preferably, the method of step S150 includes:

[0019] Put the rolled core tube blank into a vacuum bag, perform a vacuum pumping operation on it to ensure tight layer bonding, remove air bubbles in the pipe fitting, and then wrap the core tube blank with a peel ply, a release film, and a breather felt respectively. After that, place it in an aerospace-grade autoclave for heating and curing. After the curing process is completed, take it out after it cools down with the autoclave.

[0020] Preferably, after taking it out of the autoclave, clamp its end on a hydraulic device and use a small axial thrust to remove the peel ply, release film, and breather felt outside the core tube blank to obtain a hollow primary composite material core tube.

[0021] Preferably, in step S160, the preparation method of the ridge-shaped prepreg twisted yarn strip for filling includes:

[0022] Use two hollow metal tubes with the same outer diameter as the core tube to roll the prepreg tape from both sides in opposite directions. When the two metal tubes come into contact, a ridge-shaped prepreg twisted yarn strip for filling is formed between the metal tubes.

[0023] Preferably, in step S160, n 2 primary composite material core tubes are used to lay the glue film on their surfaces, where n ≥ 2. Then, use a right-angle reference platform to position and assemble the core tubes with the glue film laid on them to prepare a secondary composite material tube.

[0024] In a second aspect, a composite material tube with a complex interface structure is provided, which is obtained according to the preparation method of the first aspect. The composite material tube at least includes: a primary composite material core tube obtained by laying prepreg tapes on the surface of a metal tube and curing with a pressure roller, then combining multiple primary composite material core tubes with laid adhesive films into a box girder structure, filling ridge-shaped prepreg twisted wire strips into the ridge-shaped voids of the positioned and combined core tube assembly, then covering prepreg tapes on the outer layer of the combined core tube assembly, compacting with a pressure roller, and heating and curing to obtain a secondary composite material tube with a complex interface structure.

[0025] The embodiments of the present invention have the following beneficial effects:

[0026] Conventional pipe beams, box girders, and I-beams are usually compounded with one-dimensional "point" or "line" units such as powders or fibers and two-dimensional "surface" units such as laminates, while in the present invention, three-dimensional "body" units such as "tubes" are used for compounding. And a large number of fibers and circular interfaces are included in this body unit, realizing the multi-interface compounding of materials. Compared with the prior art, the maximum deflection during the bending failure process of the composite material tube with a complex interface structure designed based on the bionic structure in this article is increased by 15%, and the maximum load-bearing capacity can be increased by more than one time. At the same time, based on the bionic configuration design of the complex interface structure, a large number of interaction interfaces between materials are introduced, including the interfaces compounded between units, the interfaces between fibers and matrices inside the unit, and the interfaces between resin matrix composite materials and metal pipe fittings. The existence of these interfaces increases the length of crack propagation to failure, enhances the ability to hinder crack propagation, and improves the toughness of the material. In addition, this structure uses materials with lower density as the main units and combines a hollow structure at the same time, and the overall density of the material is 1.1 g / cm 3 The following maintains a relatively low density while ensuring high strength and high toughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is the preparation process of the composite material tube with a complex interface structure according to the embodiment of the present application;

[0028] Figure 2 (a) is a schematic structural diagram of a secondary composite material tube prepared with 4 primary composite material core tubes;

[0029] Figure 2 (b) is a schematic structural diagram of a secondary composite material tube prepared with 9 primary composite material core tubes;

[0030] Figure 3 For 4 Figure 2 (a) is a schematic structural diagram of a tertiary composite material tube prepared with the secondary composite material tube;

[0031] Figure 4 For Figure 3 Schematic diagram of the box girder cross-section of a three-stage composite pipe structure Detailed implementation manners

[0032] In order to make the technical problems, technical solutions and advantages to be solved by the embodiments of the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments

[0033] Through continuous evolution in nature, many natural biological material structures with excellent mechanical properties have been formed, and at the same time, the lightweight of the overall structure has been realized, providing a reference direction for modern bionic structure design. Among various biological materials, the feathers and leg bones of birds are very potential research objects, with the performance advantages of light weight, high strength and impact resistance. Studying such materials has high reference value for optimizing certain specific aviation structural parts. Bird feathers have a light and low-stiffness epidermal structure. Although its mass is very light, its structure is complex. It is a multifunctional skin appendage composed of β-keratin, and its main functions include flight, camouflage, heat insulation and waterproofing, etc. In daily working conditions, feathers mainly bear the action of alternating wind loads. The basic structure of bird feathers consists of a main shaft bone and side branch bones, with a closed-cell foam structure in the spine and barb parts. The three-stage structure extending from the barb part is called barbules, and these barbules are connected to each other through small hooks at the ends, and finally form an integral feather. The spine consists of a hollow cylindrical structure composed of a cortical layer and a core of a supporting foam body called "medulla". The spine is completely filled with medulla foam at the end, while it is a hollow structure at the calamus part

[0034] The leg bones of eagles have variable cross-section characteristics. The cross-section at the joint shows a polygonal shape with square ends and an ellipse-biased middle part. When extending towards the front claw end, the cross-section shape gradually becomes round and evolves into a more regular ellipse. The closer to the claw end, the more flattened the cross-section becomes. This variable cross-section characteristic of the leg bones is related to its load-bearing characteristics. During the predation process of eagles, the joint part bears the greatest torsional action and bending moment. Due to the combined action of bending and torsional loads, the risk of local buckling at these positions is higher. The flattened cross-section shape at both ends can help the bones better resist the action of torsional and bending loads and inhibit the local buckling of the leg bones near the joint part. At a more microscopic scale, it can be observed that there are also multi-level nested support structures inside the leg bones

[0035] The special characteristics of these biological structures provide important inspiration for the design of structural materials. By applying the principles of bionic design, extracting and refining the structural coupling elements of biological materials, the design of lightweight and high-strength bionic materials with coupled multiple strengthening factors can be achieved. Through the research on the feathers and leg bones of birds, the inventor designed a bionic structural composite box girder with the characteristics of lightweight, high strength and high stiffness based on the coupled bionic structure, which can give full play to the advantages of the structural units of biological materials, and at the same time has excellent properties such as low density, high strength and high stiffness. The special hierarchical structure enables the material to have strong resistance to external force impact. This patent designs a composite box girder based on the coupled bionic structure and uses the vacuum autoclave molding technology to prepare a bionic composite multi-level nested box girder with the characteristics of lightweight, high stiffness and high strength.

[0036] The preparation process of the composite material pipe with a complex interface structure of this application is as Figure 1 shown, which is a schematic diagram of the structure of the complex cross-section pipe fitting provided by the embodiment of the present invention.

[0037] See Figures 1 to 4 shown, a method for preparing a composite material pipe with a complex interface structure of the present invention includes at least the following steps S110 to step S160:

[0038] Step S110, perform surface treatment on the metal pipe;

[0039] Step S120, based on the bionic structure, design the laying angle and sequence of the prepreg, and calculate and determine the orientation, size and quantity of the carbon fiber / epoxy resin prepreg for each layer, and obtain the prepreg tape by numerical control cutting;

[0040] Step S130, manually pre-lay the prepreg tape on the surface of the treated metal pipe to position the laying layer;

[0041] Step S140, use an automatic pipe rolling machine to roll the treated metal pipe with a roller. For each symmetric cycle of the prepreg layer laid, the number of roller passes needs to be increased;

[0042] Step S150, heat and cure the core pipe blank of the rolled composite material metal pipe to obtain a hollow primary composite core pipe;

[0043] Step S160, lay a glue film on the surface of the primary composite core pipe, then use a right-angle reference platform to position and assemble multiple core pipes with the glue film laid, and fill the ridge-shaped voids of the positioned core pipe assembly with ridge-shaped prepreg twist filaments. Then, wrap a prepreg tape on the outer layer of the assembled core pipe assembly and compact it with a roller, and heat and cure it to obtain a secondary composite material pipe with a complex interface structure.

[0044] As other embodiments, it may further include preparing a three - level composite material tube: after positioning and combining a certain number of two - level composite material tubes in a square array and fixing their positions, prepreg tapes are wrapped around the outer layer of the combined structure and compacted using a pressure roller, and a three - level composite material tube with a complex interface structure is obtained after heating and curing. By analogy, an N - level composite material tube is prepared, where N>3.

[0045] The preparation process of the bionic - structure composite material tube in this embodiment adopts the step - by - step curing + co - bonding process method. An aluminum tube is wrapped with a composite material prepreg and then cured, or a steel tube is pasted with a prepreg and then cured and demolded to manufacture the first - level composite material core tube inside the bionic structure. Then, the first - level composite material core tube assembly is used as a template to wrap the prepreg to prepare the second - level composite material tube. Compared with the traditional beam - structure preparation method, this novel bionic structure prepared by a bottom - up strategy is not limited by length, and samples with a designable ply angle and a very large length dimension can be prepared.

[0046] The following will be described with specific Examples 1 to 5:

[0047] Example 1:

[0048] The specific implementation steps of the bionic composite nested box - type beam are as follows:

[0049] Step 1. Surface treatment of the steel tube: The steel core mold is scrubbed with an acid - alkaline solution to remove the oil stain, protective layer, oxide scale, severe rust and other attachments on the surface of the steel tube, and then cleaned with an alcohol solution. The surface of the steel tube is polished with 2000 - mesh sandpaper to make it smooth, and then the surface is cleaned with alcohol and dried. A release agent is applied to the surface of the steel tube, with a total of three passes, and the interval between each pass is 15 minutes, so that the release agent dries and adheres to the surface of the core mold.

[0050] Step 2. Cutting the prepreg strips: According to the ply angle and sequence of the prepreg designed for the bionic structure, calculate and determine the orientation, size and quantity of the carbon fiber / epoxy resin prepreg for each ply, and set the cutter travel path program on the numerical control cutting machine to cut the prepreg. For example, according to the fiber orientation characteristics of the outer sheath cortex of the feather shaft, the inner tube is designed as [+45, - 45, - 45, +45] s periodic ply to better cope with shear stress and generate a tensile - torsion coupling effect to deal with the internal structure torsional deformation and damage; the outer wall is designed as [+45, - 45, 0, 90, 90, 0, - 45, +45] s periodic ply to better cope with the tensile / compressive stress distributed in the wall plate and inhibit the buckling and bursting of the structure. A series of prepreg tapes with specific fiber orientations are obtained using numerical control cutting equipment.

[0051] Step 3. Manually pre-lay prepreg on the steel pipe surface: Manually pre-lay prepreg on the steel pipe surface to position the laying layer, prevent it from deviating from the steel pipe axis, and facilitate further rolling by the pressure roller on the pipe rolling machine.

[0052] Step 4. Roll with the pipe rolling machine: To ensure close contact between prepreg layers and the forming quality of the steel pipe surface, use an automatic pipe rolling machine to roll the steel pipe after the pre-laying is completed. The pressure is set to 0.8 Mpa, the speed is 1500 mm / min, and the traveling distance of the pressure roller is set to 300 mm. For each symmetric cycle (1 s) of prepreg laying, an additional pass of the pressure roller is required to avoid detachment and warping at the joint, which may affect fiber continuity and the next rolling process.

[0053] Step 5. Cure the composite core pipe: Place the core pipe blank of the rolled composite steel pipe into a vacuum bag and perform a vacuum pumping operation to ensure close bonding between its single layers, remove air bubbles in the pipe fittings, and prevent the prepreg layer from wrinkling during the curing process. Wrap the core pipe blank with peel ply, release film, and breather felt respectively. Then place it into an aerospace-grade autoclave for heating and curing. After the curing process is completed, wait for it to cool down with the autoclave and then take it out.

[0054] In Step 5, it also includes core pipe demolding: Since the core pipe is relatively long, there are protruding core molds at both ends of the cured core pipe. Clamp it on the hydraulic equipment, and the core mold (peel ply, release film, breather felt) can be removed with a relatively small axial thrust. After demolding, a hollow primary composite core pipe is obtained.

[0055] Step 6. Prepare the composite box girder blank. Lay the adhesive film on the surface of the primary composite core pipe obtained in Step 5. Then use a right-angle reference platform to position 4 core pipes and assemble them. On the right-angle base, use a clamping plate and multi-turn wound wire to fix the positions of the core pipes. Lay the ridged prepreg filament strip in the ridged gap of the positioned core pipe assembly and press it flat with a tooling to make them closely combined. Then wrap the prepreg on the outer layer of the assembled core pipe assembly and compact it with a pressure roller.

[0056] In this step, the ridged prepreg filament strip for filling is prepared as follows: Use two hollow metal pipes with the same outer diameter as the core pipe to roll the prepreg from both sides in opposite directions to form the ridged filling filament strip.

[0057] In Step 6, it also includes vacuum packaging of the blank: Wrap the core pipe blank with peel ply, release film, and breather felt respectively. Place the rolled core pipe assembly blank in Step 6 into a vacuum bag and perform a vacuum pumping operation on it.

[0058] In Step 6, it also includes blank curing: The vacuum-packaged blank is placed in an aerospace-grade autoclave for heating and curing. The curing process system adopts a medium-temperature curing process (curing temperature 120 °C, curing time 8 h). After the curing program is completed, wait for it to cool with the autoclave and then take it out of the mold to obtain a bionic nested box girder of a secondary composite material pipe with a complex interface structure.

[0059] Example 2:

[0060] Except for the following different steps, the rest are the same as those in Example 1:

[0061] Step 1. Surface treatment of the hollow aluminum tube: Soak the aluminum tube in an alkaline solution to remove the oil dirt, oxide scale and other attachments on the inner and outer walls of the aluminum tube, and then clean it with an alcohol solution. Use 100-mesh sandpaper to polish the outer wall of the aluminum tube to make its surface rough, so as to ensure the bonding between the adhesive film and the surface of the aluminum tube when laying the glue on the surface. After polishing, clean the aluminum tube with acetone and set it aside after drying.

[0062] Step 3. Manually pre-lay the epoxy resin adhesive film and prepreg on the surface of the aluminum tube: Manually pre-lay the epoxy resin adhesive film and prepreg on the surface of the aluminum tube to facilitate further rolling by the pressure roller on the tube rolling machine.

[0063] Example 3:

[0064] Except for the following different steps, the rest are the same as those in Example 1 or Example 2:

[0065] Step 6. Preparation of the composite material box girder blank. Lay the adhesive film on the surface of the primary composite material core tube obtained in Step 5, and then use a right-angle reference platform to position 9 core tubes and then assemble them to form a 3×3 square array. On the right-angle basic platform, use a clamping plate and multi-turn wound iron wire to fix the positions of the core tubes. Lay the ridged prepreg twisted wire strips in the ridged gaps of the positioned and combined core tube assemblies, and flatten them with a tooling to make them closely combined. Then cover the outer layer of the combined core tube assemblies with prepreg and compact it with a pressure roller.

[0066] Example 4:

[0067] Except for the following different steps, the rest are the same as those in Example 1, Example 2 or Example 3:

[0068] Step 6. Preparation of the composite material box girder blank. After combining and assembling the primary composite material core tubes obtained in Step 5, lay the ridged prepreg twisted wire strips in the ridged gaps of the positioned and combined core tube assemblies, and flatten them with a tooling to make them closely combined. Process cylindrical aluminum foam matching the inner diameter of the metal tube, or cut an appropriate number of foamed resin adhesives (foaming temperature 120 °C, the same as the curing temperature of the prepreg), and fill them into the core tubes.

[0069] Example 5:

[0070] Except for the following different steps, the rest are the same as those in Embodiment 1, Embodiment 2, Embodiment 3 or Embodiment 4.

[0071] It further includes Step Seven: Preparation of the three - level structure nested box - girder blank. After positioning and combining the bionic nested box - girders of the secondary composite tubes obtained in Step Six in a square array, use clamping plates and multi - loop wound iron wires for position fixation. Then, prepreg is coated on the outer layer of the combined structure and compacted using a pressure roller.

[0072] It further includes Step Eight: Curing of the blank. Place the vacuum - encapsulated blank into an aviation - grade autoclave for heating and curing. The curing process system adopts a medium - temperature curing process (curing temperature 120 °C, curing time 8 h). After the curing program is completed, wait for it to cool with the autoclave and then take it out for demolding to obtain the three - level structure nested box - girder.

[0073] Currently, common lightweight and high - strength materials mainly include three - dimensional lattice truss structures, three - dimensional grid structures such as sponge - like structures, sandwich - type sandwich structures, brittle - ductile composite layered structures, and fiber - or particle - reinforced bulk composites. Such structures usually use one - dimensional "point" or "line" units such as powders or fibers, and two - dimensional "plane" units such as laminae for compounding. In the present invention, three - dimensional volume units such as "tubes" are used for compounding. And a large number of fibers and circular interfaces are also included in this volume unit, realizing the compounding of multiple interfaces of the material.

[0074] Compared with conventional pipe beams, box girders, and I - beams, it has been verified that for the composite material tube with a complex interface structure designed based on the bionic structure in the present invention, the maximum deflection during the bending failure process is increased by 15%, and the maximum load - bearing capacity can be increased by more than one time. At the same time, based on the complex interface structure designed by bionic configuration, a large number of interaction interfaces between materials are introduced, including the interfaces between units during compounding, the interfaces between fibers and matrices inside the unit, and the interfaces between resin - based composites and metal pipe fittings. The existence of these interfaces increases the length of crack propagation to failure, enhances the ability to hinder crack propagation, and improves the toughness of the material. In addition, this structure uses materials with lower density as the main units and combines a hollow structure. The overall density of the material is 1.1 g / cm 3 The following maintains a relatively low density while ensuring high strength and high toughness.

[0075] In the method embodiments of the present invention, the sequence numbers of the steps cannot be used to limit the order of the steps. For those of ordinary skill in the art, without creative efforts, the changes in the order of the steps are also within the protection scope of the present invention.

[0076] The above are the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a composite material tube with a complex interface structure, characterized in that, it includes: Step S110, performing surface treatment on the metal tube; Step S120, designing the laying angle and sequence of the prepreg based on the bionic structure, and calculating and determining the orientation, size and quantity of the carbon fiber / epoxy prepreg for each layer, and numerically controlled cutting to obtain a series of prepreg tapes with specific fiber orientations; Step S130, manually pre-laying the prepreg tapes on the surface of the treated metal tube to position the laying positions; Step S140, using an automatic tube rolling machine to roll the metal tube after pre-laying with a pressure roller. For each symmetric cycle of prepreg laying completed, the number of pressure roller passes needs to be increased once; Step S150, heating and curing the core tube blank of the rolled composite material metal tube to obtain a hollow primary composite material core tube; Step S160, laying a film on the surface of the primary composite material core tube, then using a right-angle reference platform to position and assemble multiple core tubes with the film laid, and filling the ridge-shaped voids of the positioned core tube assembly with ridge-shaped prepreg twist strips. Then, wrap the outer layer of the assembled core tube assembly with prepreg tapes and compact them with a pressure roller, and obtain a secondary composite material tube with a complex interface structure after heating and curing; After positioning and combining a certain number of secondary composite material tubes in a square array and fixing their positions, then wrap the outer layer of the combined structure with prepreg tapes and compact them with a pressure roller, and obtain a tertiary composite material tube with a complex interface structure after heating and curing. And so on, prepare an N-level composite material tube, where N > 3.

2. The preparation method according to claim 1, characterized in that, the metal tube is a hollow aluminum tube or a steel tube.

3. The preparation method according to claim 1, characterized in that, the method of step S110 includes: wiping the metal tube with an acid-base solution to remove the oil dirt, protective layer, oxide scale, severe rust and other attachments on the surface of the metal tube, then cleaning with an alcohol solution, and then using sandpaper to polish the surface of the metal tube to make it smooth, and then cleaning and drying the surface with alcohol.

4. The preparation method according to claim 1, characterized in that, the method of step S150 includes: Put the rolled core tube blank into a vacuum bag, perform a vacuum pumping operation on it to ensure tight interlayer bonding, remove the air bubbles in the pipe fittings, then wrap the core tube blank with a peel ply, a release film and a breather felt respectively, and then place it in an aerospace-grade autoclave for heating and curing. After the curing program is completed, wait for it to cool with the autoclave and then take it out.

5. The preparation method according to claim 4, characterized in that, After taking it out of the autoclave, clamp its end on a hydraulic device and use a small axial thrust to remove the peel ply, release film and breather felt outside the core tube blank to obtain a hollow primary composite material core tube.

6. The preparation method according to claim 1, characterized in that, in step S160, the preparation method of the ridge-shaped prepreg twist strip for filling includes: Using two hollow metal tubes with the same outer diameter as the core tube, the prepreg tape is roll-pressed from both sides towards each other. When the two metal tubes come into contact, a ridge-shaped prepreg twist wire strip for filling is formed between the metal tubes.

7. According to the preparation method described in claim 1, characterized in that In the step S160, n 2 layers of adhesive films are laid on the surface of the first-level composite material core pipes, where n≥2. After that, a right-angle reference platform is used to position the core pipes with the adhesive films laid thereon, and then the second-level composite material pipes are assembled and prepared.

8. A composite material tube with a complex interface structure, characterized in that it is obtained according to the preparation method described in any one of claims 1 to 7.

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