SiC fiber reinforced metal matrix composite pipe structure and method of making

Abstract

This invention relates to the field of composite material structure design and manufacturing, specifically to a SiC fiber-reinforced metal matrix composite tube structure and its preparation method. The tube structure is a cylindrical shape with a constant outer diameter, and a SiC fiber-reinforced metal matrix composite layer is provided inside the tube wall. Within the composite layer, SiC fibers with a metal coating deposited on their surface are arranged as reinforcements within the metal matrix tube wall. The composite layer is arranged in a stepped manner at both ends and at the joints of the tube structure, with the wall thickness of the joint section being greater than that of the central section. The manufacturing process of this tube structure includes: processing the composite tube structure mold, preparing the composite precursor fiber, preparing the composite prefabricated tape, laying the composite prefabricated tape, heat treating the composite tube structure mold, sealing the composite tube structure mold, forming the composite tube structure, and processing the composite tube structure. This structure is suitable for lightweight alloy metal matrices, can improve the axial load-bearing capacity of the tube structure, and reduce the weight of the tube structure.

Description

Technical Field

[0001] This invention relates to the field of composite material structure design and manufacturing, specifically to a SiC fiber-reinforced metal matrix composite tube structure and its preparation method. Background Technology

[0002] In recent years, with the continuous development of the aerospace field, the demand for lightweight aircraft structural components has been increasing in order to further improve aircraft performance. The relevant theories and manufacturing processes of traditional metallic materials such as high-strength steel, aluminum alloys, and titanium alloys have matured, but while ensuring the mechanical properties of structural components such as stiffness and strength, it is difficult to further meet the weight reduction requirements. Therefore, replacing traditional metallic materials with lightweight, high-strength materials has gradually become the most important and effective way to achieve lightweighting of advanced aircraft.

[0003] SiC fiber-reinforced metal matrix composites are typically composite materials with SiC fibers as reinforcement and a metallic material as the matrix. SiC fibers possess high strength, high modulus, and low density, and as reinforcements, they can effectively improve the specific strength, specific stiffness, creep resistance, and high-temperature durability of metallic materials. Using SiC fiber-reinforced metal matrix composites to replace traditional metallic materials in the fabrication of aircraft structural components can ensure the performance requirements of the components while achieving a weight reduction of 20% to 60%.

[0004] Tubular structures are an important type of load-bearing structure in advanced aircraft, typically subjected to large tensile and compressive loads. Due to their thin walls and large aspect ratio, using SiC fiber-reinforced metal matrix composites to replace traditional metal materials in the fabrication of tubular structures easily leads to problems such as fiber breakage, making the fabrication of these structures difficult. Therefore, proposing a reasonable and effective SiC fiber-reinforced metal matrix composite tubular structure and its fabrication method has significant implications and promising applications in the aerospace field. Summary of the Invention

[0005] To address the weight reduction requirements of tubular structural components in advanced aircraft, this invention proposes a SiC fiber-reinforced metal matrix composite tubular structure and its preparation method. The SiC fiber-reinforced metal matrix composite tubular structural component prepared based on this invention can improve axial load-bearing capacity and significantly reduce the weight of tubular structural components compared to tubular structural components prepared from matrix metal materials.

[0006] This invention is achieved through the following technical solution:

[0007] A SiC fiber-reinforced metal matrix composite tube structure is disclosed. The SiC fiber-reinforced metal matrix composite tube structure is a tubular structure formed by the coaxial composite of an inner metal matrix, a composite material layer, and an outer metal matrix. The tube structure is a cylindrical tube with a uniform outer diameter. The SiC fiber-reinforced metal matrix composite material layer is arranged within the tube wall of the metal matrix composed of the inner and outer metal matrices. In the composite material layer, SiC fibers with a metal coating deposited on their surface are arranged as reinforcements within the tube wall of the metal matrix. The ends of the composite material layer are arranged in a stepped manner at the joints with the tube structure. The tube structure is divided into a central section and a joint section. The joint section is the part where the ends of the composite material layer connect to the tube structure. The central section is the non-joint section where SiC fibers are uniformly arranged. The wall thickness of the joint section is greater than that of the central section.

[0008] The aforementioned SiC fiber-reinforced metal matrix composite tube structure uses continuous monofilament SiC fibers, prepared by chemical vapor deposition using tungsten wire or carbon fiber as the deposition substrate. The SiC fiber diameter ranges from 50 to 160 μm, the tensile strength ranges from 3000 to 4000 MPa, and the density ranges from 2.80 to 3.50 g / cm³. 3 .

[0009] The SiC fiber-reinforced metal matrix composite tube structure has a metal matrix tube wall thickness ranging from 4 to 8 mm, and the metal matrix tube wall material is a lightweight alloy such as aluminum alloy, titanium alloy, or titanium-aluminum alloy.

[0010] The SiC fiber reinforced metal matrix composite tube structure has a composite material layer thickness ranging from 2 to 4 mm. The composite material layer is equidistant from the inner and outer walls of the tube structure. No SiC fibers are exposed at the top or bottom of the tube structure. The axial direction of the SiC fibers is consistent with the axial direction of the tube structure. The SiC fibers are arranged in layers along the radial direction of the tube structure. The number of SiC fiber layers ranges from 4 to 8. The SiC fibers between the layers are arranged in an interlaced and dense manner, that is, the SiC fibers in the cross-section of the tube structure are approximately hexagonally close-packed.

[0011] In the SiC fiber reinforced metal matrix composite tube structure, the length of SiC fibers in each layer decreases from the inside to the outside, with a single-sided decrease range of 0.5 to 2.5 mm for each layer, so that the angle α between the bottom edge line or the top edge line of the composite material layer and the axial edge ranges from 5 to 20°.

[0012] The SiC fiber reinforced metal matrix composite pipe structure has an inner metal matrix thickness greater than that of the inner metal matrix in the central section, with the greater thickness ranging from 50% to 100% of the inner metal matrix thickness of the central section. The end of the thickened portion of the inner metal matrix is ​​flush with the end of the outermost SiC fiber of the composite material layer, and chamfered connections are used between areas with different thicknesses of the inner metal matrix.

[0013] The method for preparing the SiC fiber-reinforced metal matrix composite tube structure includes the following steps:

[0014] (1) Design and fabrication of composite material tube structure mold: The composite material tube structure mold consists of one tube structure mold liner, one tube structure mold outer sleeve, and two tube structure mold caps. The tube structure mold liner is a uniform diameter cylinder made of metal matrix material, and the tube structure mold outer sleeve is a cylinder made of metal matrix material with a circular cross-section. The tube structure mold liner and the tube structure mold outer sleeve are coaxially and oppositely arranged. The tube structure mold caps are the left cap and the right cap, which are coaxially and symmetrically arranged at both ends of the tube structure mold liner and the tube structure mold outer sleeve. The four tube structure mold components are assembled in close contact and matched in size, forming a cavity for arranging composite materials.

[0015] (2) Preparation of composite precursor fiber: A metal coating is deposited on the surface of SiC fiber by physical vapor deposition to obtain composite precursor fiber, wherein the volume fraction of SiC fiber is 40-80%;

[0016] (3) Preparation of composite material prefabricated tape: The composite material pilot wires are arranged and bonded with organic adhesive to form a single-layer composite material prefabricated tape. The prefabricated tape is cut according to the inner lining size of the pipe structure mold and the stepped size of the composite material layer of the pipe structure joint section.

[0017] (4) Laying composite material prefabricated strips: Then stack and paste the composite material prefabricated strips from long to short onto the outer wall of the inner lining of the pipe structure mold, and assemble and fix the left end cap of the pipe structure mold, the outer sleeve of the pipe structure mold, and the right end cap of the pipe structure mold in sequence.

[0018] (5) Heat treatment of composite material tube structure mold: Vacuum heat treatment is performed on the composite material tube structure mold to remove the organic glue used in the preparation of composite material preform strip. The temperature range is 200-400℃ and the heating time range is 60-120min.

[0019] (6) Sealing composite material tube structure mold: The gap between the four tube structure mold components and the composite material prefabrication strip is sealed using electron beam vacuum welding process;

[0020] (7) Composite material tube structure molding: The vacuum-sealed composite material tube structure mold is processed by hot isostatic pressing to completely close the gaps between the composite material precursor wires and the composite material preforms, forming a dense SiC reinforced metal matrix composite preform.

[0021] (8) Composite material tube structure processing: The excess metal matrix of the SiC reinforced metal matrix composite preform is removed by mechanical processing to obtain the SiC fiber reinforced metal matrix composite tube structure.

[0022] The method for preparing the SiC fiber reinforced metal matrix composite pipe structure includes a pipe structure mold outer sleeve comprising an outer sleeve equal-diameter inner bore surface and an outer sleeve positioning groove. The outer sleeve positioning grooves are a left positioning groove and a right positioning groove, which are coaxially oppositely opened at both ends of the outer sleeve equal-diameter inner bore surface.

[0023] The method for preparing the SiC fiber-reinforced metal matrix composite pipe structure describes a pipe structure mold cap that is a stepped rotating body with a diameter matching the diameter of the outer sleeve positioning groove and the diameter of the inner bore surface of the outer sleeve, respectively.

[0024] The left end cap of the tubular mold is provided with a left end cap positioning step, a contact surface between the left end cap and the inner bore surface of the outer sleeve, and a contact surface between the left end cap and the pilot wire. The outer diameter of the left end cap positioning step matches the diameter of the left positioning groove of the outer sleeve. The outer diameter of the contact surface between the left end cap and the inner bore surface of the outer sleeve matches the diameter of the inner bore surface of the outer sleeve. The contact surface between the left end cap and the pilot wire is a frustum-shaped surface corresponding to the inner side of the contact surface between the left end cap and the inner bore surface of the outer sleeve. The edge dimension of the contact surface between the left end cap and the pilot wire is consistent with the stepped arrangement dimension of the composite material layer at the joint of the tubular structure.

[0025] The right end cap of the tubular mold is provided with a right end cap positioning step, a contact surface between the right end cap and the inner bore surface of the outer sleeve, and a contact surface between the right end cap and the pilot wire. The outer diameter of the right end cap positioning step matches the diameter of the right positioning groove of the outer sleeve. The outer diameter of the contact surface between the right end cap and the inner bore surface of the outer sleeve matches the diameter of the inner bore surface of the outer sleeve. The contact surface between the right end cap and the pilot wire is a frustum-shaped surface corresponding to the inner side of the contact surface between the right end cap and the inner bore surface of the outer sleeve. The edge dimension of the contact surface between the right end cap and the pilot wire is consistent with the stepped arrangement dimension of the composite material layer at the joint of the tubular structure.

[0026] In the preparation method of the SiC fiber reinforced metal matrix composite tube structure, in step (7), the hot isostatic pressing temperature range is 400-1200℃, the hot isostatic pressing pressure range is 25-300MPa, and the hot isostatic pressing time range is 60-120min.

[0027] The design concept of this invention is:

[0028] Based on common service conditions of pipe structures, continuous monofilament SiC fibers are used to unidirectionally reinforce the pipe structure along its axis, thereby specifically improving its service performance. Based on the interfacial shear strength calculation formula and the stepped overlap theory, the arrangement of the SiC fiber composite layer in the metal matrix is ​​designed to improve the connection performance at the joint between the composite layer and the metal matrix, preventing failure at weak points in the SiC fiber reinforced metal matrix composite pipe structure under service conditions. For this composite pipe structure, a three-step method of fiber filament-precursor filament-prefabricated tape is used to prepare the composite layer, simplifying the fiber laying process, precisely controlling the volume fraction of the reinforcement, ensuring uniform fiber distribution in the composite layer, and avoiding local defects such as fiber breakage and fiber cross-linking during fiber laying. The composite preform is manufactured using an integrated molding process involving a metal matrix mold, electron beam vacuum welding, and hot isostatic pressing, ensuring the density of the material within the pipe structure.

[0029] The advantages and beneficial effects of this invention include:

[0030] This invention proposes a SiC fiber-metal matrix composite tube structure and its preparation method. The composite tube structure uses continuous monofilament SiC fibers as reinforcement and employs a stepped arrangement to enhance the connection strength between the reinforcement and the metal matrix. It is applicable to various lightweight alloy metal matrices such as aluminum alloy, titanium alloy, and titanium-aluminum alloy. Compared with tube structures of the same specifications prepared using only a metal matrix, it can improve the axial load-bearing capacity of the tube structure and reduce its weight, which is of great significance in the lightweight technology of high-performance aircraft. Attached Figure Description

[0031] Figure 1 This invention presents a SiC fiber-reinforced metal matrix composite tube structure. (a) is a perspective view, (b) is a cross-sectional view of the central section perpendicular to the axial direction, and (c) is a cross-sectional view of the joint section parallel to the axial direction.

[0032] Figure 2 The mold and assembly drawing of the SiC fiber-reinforced metal matrix composite tube structure proposed in this invention have been reduced in length along the axial direction.

[0033] Figure 3 This is a schematic diagram of the outer casing of the SiC fiber-reinforced metal matrix composite tube structure mold proposed in this invention, with the length reduced in the axial direction.

[0034] Figure 4 This is a schematic diagram of the left cap (a) and right cap (b) of the SiC fiber-reinforced metal matrix composite tube structure mold proposed in this invention.

[0035] Figure 5 This is a schematic diagram of the mold assembly process for the SiC fiber-reinforced metal matrix composite tube structure proposed in this invention.

[0036] In the figure, 1 is the inner metal matrix, 2 is the composite material layer, 3 is the outer metal matrix, 4 is SiC fiber, 5 is the inner liner of the tubular mold, 6 is the outer sleeve of the tubular mold, 6.1 is the equal-diameter inner bore surface of the outer sleeve, 6.2 is the left positioning groove of the outer sleeve, 6.3 is the right positioning groove of the outer sleeve, 7 is the left end cap of the tubular mold, 7.1 is the positioning step of the left end cap, 7.2 is the contact surface between the left end cap and the inner bore surface of the outer sleeve, 7.3 is the contact surface between the left end cap and the pilot wire, 8 is the right end cap of the tubular mold, 8.1 is the positioning step of the right end cap, 8.2 is the contact surface between the right end cap and the inner bore surface of the outer sleeve, 8.3 is the contact surface between the right end cap and the pilot wire, 9 is the center section, 10 is the joint section, and 11 is the composite material prefabrication strip. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0038] like Figure 1 As shown, the SiC fiber-reinforced metal matrix composite tube structure is a tubular structure composed of an inner metal matrix 1, a composite material layer 2, and an outer metal matrix 3, which are coaxially composited in sequence. The three-dimensional structure is as follows: Figure 1 As shown in (a), the pipe structure is a cylindrical shape with a uniform outer diameter, and the inner wall of the pipe is provided with a SiC fiber-reinforced metal matrix composite material layer. The metal matrix pipe structure is a cylindrical shape with a uniform outer diameter and a wall thickness ranging from 4 to 8 mm. The material includes, but is not limited to, aluminum alloy, titanium alloy, or titanium-aluminum alloy. In the composite material layer 2, SiC fibers 4 with a surface-deposited metal coating are arranged as reinforcements within the metal matrix pipe wall. The pipe structure is divided into a central section 9 and a joint section 10. The joint section 10 is the part where the two ends of the composite material layer 2 connect to the pipe structure. The central section 9 is the part of the SiC fiber-reinforced metal matrix composite pipe structure where SiC fibers 4 are uniformly arranged, and is not part of the joint section 10. A cross-sectional view of the central section 9 perpendicular to the axial direction is shown below. Figure 1 As shown in (b), the SiC fiber-reinforced metal matrix composite layer 2 is arranged within the metal matrix tube wall composed of the inner metal matrix 1 and the outer metal matrix 3. The thickness of the composite layer 2 ranges from 2 to 4 mm. The composite layer 2 is equidistant from the inner and outer walls of the tube structure. No SiC fibers 4 are exposed at the top or bottom of the tube structure. The axial direction of the SiC fibers 4 is consistent with the axial direction of the tube structure. The SiC fibers 4 are arranged in layers along the radial direction of the tube structure, with the number of SiC fiber layers ranging from 4 to 8. The SiC fibers between the layers are arranged in an interlaced and dense manner, that is, the SiC fibers in the cross-section of the tube structure are approximately hexagonally close-packed. The cross-section of the joint section 10 parallel to the axial direction is as follows. Figure 1As shown in (c), the composite material layer 2 is arranged in a stepped manner at both ends and at the pipe structure joint. The length of each SiC fiber 4 layer decreases from the inside to the outside, with a single-sided decrease range of 0.5 to 2.5 mm for each layer. This results in an angle α between the bottom edge line or the top edge line of the composite material layer 2 and the axial edge, ranging from 5 to 20°. The wall thickness of the pipe structure joint section 10 is greater than that of the central section 9. The thickness of the inner metal matrix 1 of the pipe structure joint section 10 is greater than that of the inner metal matrix 1 of the central section 9, by a range of 50% to 100%. The end of the thickened portion of the inner metal matrix 1 is flush with the end of the outermost SiC fiber 4 of the composite material layer 2. Chamfered connections are used between areas of different thicknesses of the inner metal matrix 1.

[0039] SiC fibers are continuous monofilament SiC fibers, prepared by chemical vapor deposition using tungsten wire or carbon fiber as the deposition substrate. The SiC fiber diameter ranges from 50 to 160 μm, the tensile strength ranges from 3000 to 4000 MPa, and the density ranges from 2.80 to 3.50 g / cm³. 3 .

[0040] The above-mentioned method for preparing SiC fiber-reinforced metal matrix composite tube structures includes the following steps:

[0041] (1) Design and fabricate molds for composite material tube structures: such as Figure 2 As shown, the composite material tubular structure mold consists of one inner mold liner 5, one outer mold sleeve 6, and two mold caps (left mold cap 7 and right mold cap 8). The inner mold liner 5 is a uniform-diameter cylinder made of metal matrix material, and the outer mold sleeve 6 is a cylinder made of metal matrix material with a circular cross-section. The inner mold liner 5 and the outer mold sleeve 6 are coaxially aligned and opposite each other. The left mold cap 7 and the right mold cap 8 are coaxially symmetrically positioned at both ends of the inner mold liner 5 and the outer mold sleeve 6. The four tubular structure mold components can be assembled to ensure tight contact and dimensional matching, forming cavities for arranging the composite material.

[0042] like Figure 3 As shown, the outer sleeve 6 of the pipe structure mold includes an outer sleeve equal-diameter inner bore surface 6.1 and an outer sleeve positioning groove (outer sleeve left positioning groove 6.2 and outer sleeve right positioning groove 6.3). The outer sleeve left positioning groove 6.2 and outer sleeve right positioning groove 6.3 are respectively coaxially and oppositely opened at both ends of the outer sleeve equal-diameter inner bore surface 6.1.

[0043] like Figure 4 As shown, the tube structure mold cap is a stepped rotating body with a diameter that is consistent with the diameter of the outer sleeve positioning groove and the diameter of the inner bore surface 6.1 of the outer sleeve, wherein:

[0044] The left end cap 7 of the tubular mold is provided with a left end cap positioning step 7.1, a contact surface 7.2 between the left end cap and the inner bore surface of the outer sleeve, and a contact surface 7.3 between the left end cap and the pilot wire. The outer diameter of the left end cap positioning step 7.1 matches the diameter of the left positioning groove 6.2 of the outer sleeve. The outer diameter of the contact surface 7.2 between the left end cap and the inner bore surface of the outer sleeve matches the diameter of the inner bore surface 6.1 of the outer sleeve. The contact surface 7.3 between the left end cap and the pilot wire is a frustum-shaped surface corresponding to the inner side of the contact surface 7.2 between the left end cap and the inner bore surface of the outer sleeve. The edge dimension of the contact surface 7.3 between the left end cap and the pilot wire is consistent with the stepped arrangement dimension of the composite material layer 2 at the joint of the tubular structure.

[0045] The right end cap 8 of the pipe structure mold is provided with a right end cap positioning step 8.1, a contact surface 8.2 between the right end cap and the inner bore surface of the outer sleeve, and a contact surface 8.3 between the right end cap and the pilot wire. The outer diameter of the right end cap positioning step 8.1 matches the diameter of the right positioning groove 6.3 of the outer sleeve. The outer diameter of the contact surface 8.2 between the right end cap and the inner bore surface of the outer sleeve matches the diameter of the equal-diameter inner bore surface 6.1 of the outer sleeve. The contact surface 8.3 between the right end cap and the pilot wire is a frustum-shaped surface corresponding to the inner side of the contact surface 8.2 between the right end cap and the inner bore surface of the outer sleeve. The edge dimension of the contact surface 8.3 between the right end cap and the pilot wire is consistent with the stepped arrangement dimension of the composite material layer 2 at the pipe structure joint.

[0046] (2) Preparation of composite precursor fiber: A metal coating is deposited on the surface of SiC fiber by physical vapor deposition to obtain composite precursor fiber, wherein the volume fraction of SiC fiber is 40-80%;

[0047] (3) Preparation of composite material prefabricated tape: The composite material precursor filaments are arranged and bonded with organic adhesives (such as polyvinyl alcohol PVA or polymethyl methacrylate PMMA, etc.) to form a single-layer composite material prefabricated tape. The prefabricated tape is cut according to the inner lining size of the pipe structure mold and the stepped size of the composite material layer of the pipe structure joint section.

[0048] (4) Laying precast composite material strips: Stack and paste the precast composite material strips 11 from longest to shortest onto the outer wall of the inner lining 5 of the pipe structure mold. Then assemble and fix the left end cap 7, the outer sleeve 6, and the right end cap 8 of the pipe structure mold in sequence. See the assembly sequence below. Figure 2 and Figure 5 ;

[0049] (5) Heat treatment of composite material tube structure mold: Vacuum heat treatment is performed on the composite material tube structure mold to remove the organic glue used in the preparation of composite material preform strip. The temperature range is 200-400℃ and the heating time range is 60-120min.

[0050] (6) Sealing composite material tube structure mold: The gap between the four tube structure mold components and the composite material prefabrication strip is sealed using electron beam vacuum welding process;

[0051] (7) Composite material tube structure molding: The vacuum-sealed composite material tube structure mold is processed by hot isostatic pressing and other processes to completely close the gaps between the composite material precursor wires and the composite material preforms, forming a dense SiC reinforced metal matrix composite preform. The hot isostatic pressing temperature range is 400~1200℃, the hot isostatic pressing pressure range is 25~300MPa, and the hot isostatic pressing time range is 60~120min.

[0052] (8) Composite material tube structure processing: Excess metal matrix of the SiC reinforced metal matrix composite preform is removed by machining methods such as turning to obtain the SiC fiber reinforced metal matrix composite tube structure. For example... Figures 1-2 As shown, the outer casing 6 of the pipe structure mold corresponds to the outer metal substrate 3 after processing, the inner lining 5 of the pipe structure mold corresponds to the inner metal substrate 1 after processing, and the composite material preform 11 corresponds to the composite material layer 2 after hot isostatic pressing.

[0053] The results show that, compared with metal matrix tube structures of the same shape, the SiC fiber reinforced metal matrix composite tube structure of the present invention improves the load-bearing capacity of the structural components and reduces their weight, and has great application prospects in the lightweighting of high-performance aircraft.

[0054] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. A SiC fiber-reinforced metal matrix composite tube structure, characterized in that, The SiC fiber-reinforced metal matrix composite tube structure is a tubular structure composed of an inner metal matrix, a composite material layer, and an outer metal matrix, which are coaxially composited in sequence. The tube structure is a cylindrical tube with a uniform outer diameter. The composite material layer is arranged inside the tube wall of the metal matrix composed of the inner and outer metal matrices. In the composite material layer, SiC fibers with a metal coating deposited on the surface are arranged as reinforcements inside the tube wall of the metal matrix. The two ends of the composite material layer are arranged in a stepped manner at the joints of the tube structure. The tube structure is divided into a central section and a joint section. The joint section is the part where the two ends of the composite material layer are connected to the tube structure. The central section is the part of the SiC fiber-reinforced metal matrix composite tube structure where SiC fibers are evenly arranged and are not jointed. The wall thickness of the joint section is greater than that of the central section. The thickness of the metal substrate tube wall ranges from 4 to 8 mm, and the metal substrate tube wall material is aluminum alloy, titanium alloy, or titanium-aluminum alloy. The thickness of the composite material layer ranges from 2 to 4 mm. The distance between the composite material layer and the inner and outer walls of the tube structure is equal. There are no exposed SiC fibers on the top and bottom of the tube structure. The axial direction of the SiC fibers is consistent with the axial direction of the tube structure. The SiC fibers are arranged in layers along the radial direction of the tube structure. The number of SiC fiber layers ranges from 4 to 8. The SiC fibers between the layers are arranged in an interlaced and dense manner, that is, the SiC fibers in the cross section of the tube structure are approximately hexagonally close-packed. The length of SiC fibers in each layer decreases from the inside out, with a single-sided decrease range of 0.5~2.5mm for each layer, so that the angle α between the bottom edge or top edge of the composite material layer and the axial edge ranges from 5~20°. The thickness of the inner metal matrix in the pipe structure joint section is greater than that in the central section, and the greater range is 50-100% of the thickness of the inner metal matrix in the central section. The end of the thickened part of the inner metal matrix is ​​flush with the end of the outermost SiC fiber of the composite material layer. Chamfered connections are used between areas with different thicknesses of the inner metal matrix.

2. The SiC fiber-reinforced metal matrix composite tube structure according to claim 1, characterized in that, SiC fibers are continuous monofilament SiC fibers, prepared by chemical vapor deposition using tungsten wire or carbon fiber as the deposition substrate. The diameter of the SiC fibers ranges from 50 to 160 μm, the tensile strength ranges from 3000 to 4000 MPa, and the density ranges from 2.80 to 3.50 g / cm³. 3 .

3. A method for preparing a SiC fiber-reinforced metal matrix composite tube structure according to any one of claims 1 to 2, characterized in that, Includes the following steps: (1) Design and fabrication of composite material tube structure mold: The composite material tube structure mold consists of one tube structure mold liner, one tube structure mold outer sleeve, and two tube structure mold caps. The tube structure mold liner is a uniform diameter cylinder made of metal matrix material, and the tube structure mold outer sleeve is a cylinder made of metal matrix material with a circular cross-section. The tube structure mold liner and the tube structure mold outer sleeve are coaxially and oppositely arranged. The tube structure mold caps are the left cap and the right cap, which are coaxially and symmetrically arranged at both ends of the tube structure mold liner and the tube structure mold outer sleeve. The four tube structure mold components are assembled in close contact and matched in size, forming a cavity for arranging composite materials. (2) Preparation of composite precursor fiber: A metal coating is deposited on the surface of SiC fiber by physical vapor deposition to obtain composite precursor fiber, wherein the volume fraction of SiC fiber is 40-80%; (3) Preparation of composite material prefabricated tape: The composite material pilot wires are arranged and bonded with organic adhesive to form a single-layer composite material prefabricated tape. The prefabricated tape is cut according to the inner lining size of the pipe structure mold and the stepped size of the composite material layer of the pipe structure joint section. (4) Laying composite material prefabricated strips: Then stack and paste the composite material prefabricated strips from long to short onto the outer wall of the inner lining of the pipe structure mold in sequence, and assemble and fix the left end cap of the pipe structure mold, the outer sleeve of the pipe structure mold, and the right end cap of the pipe structure mold in sequence. (5) Heat treatment of composite material tube structure mold: Vacuum heat treatment is performed on the composite material tube structure mold to remove the organic glue used in the preparation of composite material preform strip. The temperature range is 200~400℃ and the heating time range is 60~120min. (6) Sealing composite material tube structure mold: The gap between the four tube structure mold components and the composite material prefabrication strip is sealed using electron beam vacuum welding process; (7) Composite material tube structure molding: The vacuum-sealed composite material tube structure mold is processed by hot isostatic pressing to completely close the gaps between the composite material precursor wires and the composite material preforms, forming a dense SiC reinforced metal matrix composite preform. (8) Composite material tube structure processing: The excess metal matrix of the SiC reinforced metal matrix composite preform is removed by mechanical processing to obtain the SiC fiber reinforced metal matrix composite tube structure.

4. The method for preparing the SiC fiber-reinforced metal matrix composite tube structure according to claim 3, characterized in that, The outer sleeve of the pipe structure mold includes an outer sleeve equal-diameter inner bore surface and an outer sleeve positioning groove. The outer sleeve positioning grooves are a left positioning groove and a right positioning groove, which are coaxially opposite to each other at both ends of the outer sleeve equal-diameter inner bore surface.

5. The method for preparing the SiC fiber-reinforced metal matrix composite tube structure according to claim 4, characterized in that, The tube structure mold cap is a stepped rotating body with a diameter that matches both the diameter of the outer sleeve positioning groove and the diameter of the inner bore surface of the outer sleeve. The left end cap of the tubular mold is provided with a left end cap positioning step, a contact surface between the left end cap and the inner bore surface of the outer sleeve, and a contact surface between the left end cap and the pilot wire. The outer diameter of the left end cap positioning step matches the diameter of the left positioning groove of the outer sleeve. The outer diameter of the contact surface between the left end cap and the inner bore surface of the outer sleeve matches the diameter of the inner bore surface of the outer sleeve. The contact surface between the left end cap and the pilot wire is a frustum-shaped surface corresponding to the inner side of the contact surface between the left end cap and the inner bore surface of the outer sleeve. The edge dimension of the contact surface between the left end cap and the pilot wire is consistent with the stepped arrangement dimension of the composite material layer at the joint of the tubular structure. The right end cap of the tubular mold is provided with a right end cap positioning step, a contact surface between the right end cap and the inner bore surface of the outer sleeve, and a contact surface between the right end cap and the pilot wire. The outer diameter of the right end cap positioning step matches the diameter of the right positioning groove of the outer sleeve. The outer diameter of the contact surface between the right end cap and the inner bore surface of the outer sleeve matches the diameter of the inner bore surface of the outer sleeve. The contact surface between the right end cap and the pilot wire is a frustum-shaped surface corresponding to the inner side of the contact surface between the right end cap and the inner bore surface of the outer sleeve. The edge dimension of the contact surface between the right end cap and the pilot wire is consistent with the stepped arrangement dimension of the composite material layer at the joint of the tubular structure.

6. The method for preparing the SiC fiber-reinforced metal matrix composite tube structure according to claim 3, characterized in that, In step (7), the hot isostatic pressing temperature range is 400~1200℃, the hot isostatic pressing pressure range is 25~300MPa, and the hot isostatic pressing time range is 60~120min.

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