Composite sandwich pipe pultrusion tooling and pultrusion method

Abstract

The application provides a composite sandwich pipe pultrusion tool and a pultrusion method, and relates to the technical field of pipe forming processes. The tool comprises a tool frame, a mandrel, an inner felt guide, an inner felt transition sleeve, a yarn mixing assembly, an outer felt guide and a forming die. The yarn mixing assembly comprises a yarn plate, an adjusting plate and a yarn transition sleeve. An inner felt layer is formed by wrapping an inner fiber felt layer around the outer circumferential surface of the mandrel through the inner felt guide, and the mandrel wrapped with the inner felt layer passes through the inner felt transition sleeve. Yarn is passed through the yarn plate and the yarn transition sleeve, and the yarn is wrapped around the outer side of the inner felt layer to form a yarn layer. An outer fiber felt layer is wrapped around the outer side of the yarn layer through the outer felt guide to form an outer felt layer. Thus, a preformed pipe is formed, which comprises the mandrel, the inner felt layer, the yarn layer and the outer felt layer from inside to outside. The application simplifies the process of pultrusion of the composite sandwich pipe, and improves the production efficiency and product yield.

Description

Technical Field

[0001] This invention relates to the technical field of pipe forming processes, and in particular to a pultrusion fixture and pultrusion method for composite sandwich pipes. Background Technology

[0002] Pipes, as a commonly used material, have a wide range of applications across various industries. When pipe performance requirements are not high, extrusion is often used to produce plastic pipes. However, in scenarios with specific mechanical requirements, composite material pipes are typically used. Composite material pipes are usually produced using pultrusion, which allows for continuous production of composite pipes at the lowest cost. However, due to the inherent limitations of the pultrusion process, it is primarily suitable for producing solid rods and hollow pipes, indirectly preventing conventional pultrusion from directly producing pipes with other structures. Conventional pultrusion uses a one-piece pipe mold. When producing hollow pipes, a fixed-size mandrel is used to ensure the pipe's hollowness; the mandrel and the inner wall of the mold together form the required pipe cross-section. Through a specific felt arrangement design, hollow pipes are produced. For solid rods, the felt is directly passed through the mold and cured through pultrusion. When the required material is a composite material pipe with a sandwich structure, this process requires secondary molding. That is, the composite material pipe is first molded, and then the sandwich structure is added to obtain the required sandwich structure composite material pipe.

[0003] Unlike plastic sandwich pipes which are produced by extrusion, composite pultruded sandwich pipes are more complex to produce in practice. They require a step-by-step production process. First, composite pipes are produced by pultrusion. Then, the inner walls of the pipes are cleaned and coated with adhesive to fill the sandwich structure. The inner diameter of the mating pipes and the outer diameter of the sandwich structure must be carefully controlled to avoid large gaps that could affect the mechanical properties of the final product. This method has high dimensional requirements, low production efficiency, and low product yield. Summary of the Invention

[0004] The purpose of this invention is to provide a pultrusion tooling and pultrusion method for composite sandwich tubes, so as to simplify the pultrusion process of composite sandwich tubes and improve production efficiency and product yield.

[0005] To achieve the above objectives, the embodiments of the present invention adopt the following technical solutions: In a first aspect, embodiments of the present invention provide a pultrusion fixture for composite sandwich tubes, including a fixture frame, a mandrel, an inner felt guide, an inner felt transition sleeve, a yarn mixing assembly, an outer felt guide, and a molding die; The mandrel is mounted on the tooling frame, and the mandrel has an axially penetrating inner cavity inside; The inner felt guide, the inner felt transition sleeve, the yarn mixing assembly, and the outer felt guide are arranged sequentially along the axial direction of the mandrel. The inner felt guide is installed on the tooling frame and located on one side of the mandrel, and is used to guide the inner fiber felt layer to cover the outer peripheral surface of the mandrel to form an inner felt layer; The inner felt transition sleeve is installed on the tooling frame and fitted onto the outside of the mandrel to stabilize the covering shape of the inner felt layer on the outer circumferential surface of the mandrel. The yarn mixing assembly includes a yarn plate, an adjusting plate, and a yarn transition sleeve. The yarn plate is located on the side of the inner felt transition sleeve and has multiple yarn guide holes for guiding the yarn along the axial direction of the mandrel on the outer side of the inner felt layer. The adjusting plate is mounted on the tooling frame and located behind the yarn plate. The yarn transition sleeve is fixed to the adjusting plate and fitted onto the outside of the mandrel. The yarn transition sleeve is used to guide the yarn to cover the outer side of the inner felt layer to form a yarn layer. The adjusting plate is used to adjust the eccentricity angle between the axis of the yarn transition sleeve and the axis of the mandrel. The outer felt guide is installed on the tooling frame and located on one side of the mandrel. It is used to guide the outer fiber felt layer to cover the outer side of the yarn layer to form an outer felt layer, forming a pre-formed tube consisting of a mandrel, an inner felt layer, a yarn layer, and an outer felt layer from the inside out. The forming mold has an axially penetrating inner cavity inside. The forming mold is located on one side of the mandrel, and the axis of the inner cavity of the mold is coaxial with the axis of the inner cavity of the mandrel. The inner cavity of the mold is used to insert the preformed tube.

[0006] In an optional embodiment, the cavity openings of both the inner and outer felt guides are flared, with the inlet inner diameter being larger than the outlet inner diameter.

[0007] In an optional embodiment, the mandrel is fitted with a plurality of mandrel sleeves, which are fixedly mounted on the tooling frame.

[0008] In an optional embodiment, the inner felt guide is provided on the fiber felt layer inlet side of the inner felt guide for guiding the inner fiber felt layer into the inner felt guide.

[0009] In an optional embodiment, the outer felt guide is provided on the fiber felt layer inlet side of the outer felt guide for guiding the outer fiber felt layer into the outer felt guide.

[0010] In an optional embodiment, the inner felt guide and the outer felt guide are respectively located on opposite sides of the mandrel in the radial direction.

[0011] In an optional embodiment, the yarn board is fitted outside the inner felt transition sleeve, and the portion located on the radially opposite sides of the inner felt transition sleeve has a plurality of yarn guide holes.

[0012] In an optional embodiment, the mandrel is a hollow steel tube structure.

[0013] In an optional embodiment, the axial length of the mandrel is L1, the length of the tooling fixture along the axial direction of the mandrel is L2, and the length of the molding die is L3, satisfying: L1 = L2 + 1 / 4·L3.

[0014] In a second aspect, the present invention provides a pultrusion method for composite sandwich tubes, using the composite sandwich tube pultrusion tooling described in any optional embodiment of the first aspect above, the pultrusion method comprising the following steps: The inner fiber felt layer is wrapped around the outer circumference of the mandrel by an inner felt guide to form an inner felt layer, and the mandrel covered with the inner felt layer passes through an inner felt transition sleeve; the yarn is passed through the yarn board and the yarn transition sleeve, so that the yarn wraps around the outside of the inner felt layer to form a yarn layer; the outer fiber felt layer is wrapped around the outside of the yarn layer by an outer felt guide to form an outer felt layer; thus forming a pre-formed tube consisting of a mandrel, an inner felt layer, a yarn layer, and an outer felt layer from the inside out; The preformed pipe is inserted into the mold cavity of the forming mold; The molding die is divided into molding zone 1, molding zone 2 and molding zone 3 along the pultrusion direction. The temperature of molding zone 1 is set to make the resin system in a viscous flow state. The temperature of molding zone 2 is higher than that of molding zone 1 to accelerate the resin crosslinking reaction. The temperature of molding zone 3 is lower than that of molding zone 2 to facilitate stress relaxation and final shaping. The pultrusion equipment is started to continuously pull and place the resin material in the molding zone 1 of the molding die. The core material is injected into the inner cavity of the mandrel from one end, and the core material overflows along the inner cavity of the mandrel. Then, the resin material, the preformed tube and the core material are passed through the molding zones 1, 2 and 3 of the molding die. Under the action of the temperature gradient, the impregnation, cross-linking and final curing are completed to obtain an integrated composite sandwich tube.

[0015] The embodiments of the present invention can achieve at least the following beneficial effects: This embodiment utilizes the synergistic effect of the inner felt guide and the inner felt transition sleeve to form a low-disturbance, high-fitting inner felt layer on the outer circumference of the mandrel, suppressing fiber felt slippage and arching. The yarn layer is covered by a yarn layer on the outside of the inner felt layer through the coordinated action of the yarn plate, adjusting plate, and yarn transition sleeve in the yarn mixing assembly. The adjusting plate enables millimeter-level eccentric adjustment of the yarn wrapping angle, thereby precisely controlling the yarn helix angle, interlayer winding density, and mechanical load transmission path. An outer felt layer is covered by the outer felt guide, forming a pre-formed tube consisting of a mandrel, inner felt layer, yarn layer, and outer felt layer from the inside out. Furthermore, the three-zone gradient temperature control design of the molding die, coupled with the injection timing of the resin material and the core material, overcomes the shortcomings of existing composite sandwich tube manufacturing processes, such as low efficiency, weak interfaces, and difficulty in dimensional control due to multiple steps including segmented bonding, secondary injection, and offline foaming. This simplifies the pultrusion process of composite sandwich tubes and improves production efficiency and product yield. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a top view of the overall structure of the composite material sandwich tube pultrusion tooling provided in an embodiment of the present invention; Figure 2 This is a side view of the overall structure of the composite material sandwich tube pultrusion tooling provided in an embodiment of the present invention; Figure 3 This is a side view of the tooling frame in an embodiment of the present invention; Figure 4 This is a front view of the inner felt guide in an embodiment of the present invention; Figure 5 This is a side view of the inner felt transition sleeve in an embodiment of the present invention; Figure 6 This is a front view of the yarn board in an embodiment of the present invention; Figure 7 This is a front view of the adjustment plate in an embodiment of the present invention; Figure 8 This is a side view of the yarn transition sleeve in an embodiment of the present invention; Figure 9 This is a front view of the outer felt guide in an embodiment of the present invention; Figure 10 This is a side view of the mandrel sleeve in an embodiment of the present invention.

[0018] Icons: 100 - Inner fiber felt layer; 200 - Outer fiber felt layer; 300 - Yarn; 1-Tooling frame; 2-Mandrel; 21-Mandrel sleeve; 3-Inner felt guide; 4-Inner felt transition sleeve; 5-Yarn mixing assembly; 51-Yarn board; 511-Yarn guide hole; 52-Adjusting plate; 53-Yarn transition sleeve; 6-Outer felt guide; 7-Forming mold; 8-Inner felt guide wheel; 9-Outer felt guide wheel. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0021] It should be noted that similar labels and letters in the accompanying drawings indicate similar items. Therefore, once an item is defined in one accompanying drawing, it does not need to be further defined and explained in subsequent accompanying drawings.

[0022] In the description of this invention, it should be noted that: Unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0023] The terms "upper," "lower," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use. They are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "horizontal" and "vertical" do not mean that the component is required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0024] The terms “first,” “second,” “third,” etc., are used only for distinguishing descriptions and do not indicate totality or relative position in time and / or space, nor should they be construed as indicating or implying relative importance.

[0025] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the features of the following embodiments and optional embodiments can be combined with each other.

[0026] Reference Figures 1 to 10 The first aspect of this embodiment provides a pultrusion fixture for composite sandwich tubes. The pultrusion fixture for composite sandwich tubes specifically includes a fixture frame 1, a mandrel 2, an inner felt guide 3, an inner felt transition sleeve 4, a yarn mixing assembly 5, an outer felt guide 6, and a molding die 7.

[0027] The mandrel 2 is mounted on the fixture 1, and its interior has an axially penetrating cavity. The inner felt guide 3, inner felt transition sleeve 4, yarn mixing assembly 5, and outer felt guide 6 are arranged sequentially along the axial direction of the mandrel 2. The inner felt guide 3 is mounted on the fixture 1 and located on one side of the mandrel 2, guiding the inner fiber felt layer 100 to cover the outer circumferential surface of the mandrel 2 to form the inner felt layer. The inner felt transition sleeve 4 is mounted on the fixture 1 and fitted onto the outside of the mandrel 2, stabilizing the covering shape of the inner felt layer on the outer circumferential surface of the mandrel 2. The yarn mixing assembly 5 includes a yarn plate 51, an adjusting plate 52, and a yarn transition sleeve 53. The yarn plate 51 is located on the side of the inner felt transition sleeve 4, and has multiple yarn guide holes 511 for guiding the yarn 300 along the axial direction of the mandrel 2 on the outer side of the inner felt layer. The adjusting plate 52 is installed on the tooling frame 1 and located behind the yarn plate 51. The yarn transition sleeve 53 is fixed to the adjusting plate 52 and fitted onto the outside of the mandrel 2. The yarn transition sleeve 53 is used to guide the yarn 300 to cover the outer side of the inner felt layer to form a yarn layer. The adjusting plate 52 is used to adjust the eccentricity angle between the axis of the yarn transition sleeve 53 and the axis of the mandrel 2. The outer felt guide 6 is installed on the tooling frame 1 and located on one side of the mandrel 2. It is used to guide the outer fiber felt layer 200 to cover the outer side of the yarn layer to form an outer felt layer, forming a pre-formed tube consisting of the mandrel 2, inner felt layer, yarn layer, and outer felt layer from the inside out. The forming mold 7 has an axially penetrating inner cavity. The forming mold 7 is located on one side of the mandrel 2, and the axis of the mold cavity is coaxial with the axis of the mandrel cavity. The mold cavity is used to insert the pre-formed tube.

[0028] Correspondingly, in a second aspect of this embodiment, a pultrusion method for composite sandwich tubes is also provided, wherein the pultrusion method for composite sandwich tubes utilizes the composite sandwich tube pultrusion tooling provided in the first aspect above.

[0029] Based on the specific structure of the pultrusion tooling for the composite sandwich tube, the pultrusion method for the composite sandwich tube provided in this embodiment includes the following steps: The inner fiber felt layer 100 is wrapped around the outer circumference of the mandrel 2 by the inner felt guide 3 to form an inner felt layer, and the mandrel 2 covered with the inner felt layer passes through the inner felt transition sleeve 4; the yarn 300 is passed through the yarn plate 51 and the yarn transition sleeve 53, so that the yarn 300 is wrapped around the outside of the inner felt layer to form a yarn layer; the outer fiber felt layer 200 is wrapped around the outside of the yarn layer by the outer felt guide 6 to form an outer felt layer; thus a preformed tube is formed from the inside to the outside, consisting of mandrel 2, inner felt layer, yarn layer and outer felt layer. Insert the preformed pipe into the mold cavity of the forming mold 7; The molding die 7 is divided into molding zone 1, molding zone 2 and molding zone 3 along the pultrusion direction. The temperature of molding zone 1 is set to make the resin system in a viscous flow state. The temperature of molding zone 2 is higher than that of molding zone 1 to accelerate the resin crosslinking reaction. The temperature of molding zone 3 is lower than that of molding zone 2 to relax stress and final shape. The pultrusion equipment is started to continuously pull and the resin material is placed in the molding zone 1 of the molding die 7. The core material is injected into the inner cavity of the mandrel from one end of the mandrel 2, and the core material overflows along the inner cavity of the mandrel. Then, the resin material, the preformed tube and the core material pass through the molding zone 1, molding zone 2 and molding zone 3 of the molding die 7. Under the action of temperature gradient, the impregnation, cross-linking and final curing are completed to obtain an integrated composite sandwich tube.

[0030] The composite material sandwich tube pultrusion fixture and pultrusion method provided in this embodiment can achieve at least the following beneficial effects: In this embodiment, the inner felt guide 3 and the inner felt transition sleeve 4 work together to form a low-disturbance, high-fitting inner felt layer on the outer circumference of the mandrel 2, suppressing fiber felt slippage and arching. The yarn layer is covered on the outside of the inner felt layer by the coordinated action of the yarn plate 51, adjusting plate 52, and yarn transition sleeve 53 in the yarn mixing assembly 5. Furthermore, the adjusting plate 52 enables millimeter-level eccentric adjustment of the yarn wrapping angle, thereby precisely controlling the yarn helix angle, interlayer winding density, and mechanical load transmission path. The outer felt guide 6 covers the outside of the yarn layer... The felt layer forms a pre-formed tube consisting of a mandrel 2, an inner felt layer, a yarn layer, and an outer felt layer, arranged from the inside out. Furthermore, by coordinating the three-zone gradient temperature control design of the molding die 7 with the injection sequence of the resin material and the core sandwich material, the defects of low efficiency, weak interface, and difficult size control caused by multiple processes such as segmented bonding, secondary injection, and offline foaming in the existing composite sandwich tube manufacturing process are overcome. This simplifies the pultrusion process of composite sandwich tubes and improves the production efficiency and product yield of composite sandwich tubes.

[0031] Furthermore, the composite material sandwich tube pultrusion tooling provided in this embodiment can be configured in more specific ways as follows: In an optional embodiment of this invention, the cavity openings of both the inner felt guide 3 and the outer felt guide 6 are flared openings with an inlet inner diameter larger than the outlet inner diameter. This flared cavity opening design makes it easier to guide the felt material as it enters the guide, and as the channel gradually narrows, it can more effectively concentrate the felt material at the center, thereby improving the positioning accuracy and stability during the guiding process. Furthermore, this cavity opening structure with a gradually changing inner diameter has good compatibility with felt materials of different thicknesses or softness.

[0032] In an optional embodiment of this example, the mandrel 2 is fitted with a plurality of mandrel sleeves 21, which are fixedly mounted on the tooling frame 1. By fitting a plurality of mandrel sleeves 21 on the outside of the mandrel 2 and fixing these mandrel sleeves 21 on the tooling frame 1, the structural stability of the mandrel 2 fixed on the tooling frame 1 can be enhanced.

[0033] In an optional embodiment of this example, the inner felt guide wheel 8 is provided on the fiber felt layer inlet side of the inner felt guide 3 to guide the inner fiber felt layer into the inner felt guide 3. The inner felt guide wheel 8 can accurately guide the inner fiber felt layer into the inner felt guide 3, prevent the inner fiber felt layer from shifting or twisting during the inlet process, and ensure that the inner fiber felt layer maintains the correct direction and position during the inlet process, thereby improving the inlet accuracy and consistency of the effect of inletting the inner fiber felt layer into the inner felt guide 3.

[0034] In an optional embodiment of this example, the outer felt guide wheel 9 is provided on the fiber felt layer inlet side of the outer felt guide 6 to guide the outer fiber felt layer into the outer felt guide 6. The outer felt guide wheel 9 can accurately guide the outer fiber felt layer into the outer felt guide 6, prevent the outer fiber felt layer from shifting or twisting during the inlet process, and ensure that the outer fiber felt layer maintains the correct direction and position during the inlet process, thereby improving the inlet accuracy and consistency of the effect of inletting the outer fiber felt layer into the outer felt guide 6.

[0035] In an optional embodiment of this example, the inner felt guide 3 and the outer felt guide 6 are respectively located on opposite sides of the mandrel 2 in the radial direction. The symmetrical arrangement of the inner felt guide 3 and the outer felt guide 6 can make more effective use of the limited space around the mandrel, making the entire tooling structure more compact. Furthermore, it is easier to align and calibrate the inner felt guide 3 and the outer felt guide 6 when assembling and adjusting them, reducing assembly difficulty and time, and improving the assembly efficiency of the tooling.

[0036] In an optional embodiment of this example, the yarn plate 51 is fitted onto the outside of the inner felt transition sleeve 4. The portion of the yarn plate 51 located on the radially opposite sides of the inner felt transition sleeve 4 has a plurality of yarn guide holes 511. In this example, the provision of a plurality of yarn guide holes 511 on the radially opposite sides of the inner felt transition sleeve 4 can ensure that the yarn is evenly distributed during the introduction and export process, avoid uneven tension or tangling caused by the yarn concentrating on one side, and ensure that the yarn maintains a consistent tension during introduction and export, thereby improving the quality and consistency of the final product and reducing defects caused by uneven tension.

[0037] In this embodiment, optional but not limited to: the mandrel 2 is a hollow steel tube structure, and its outer wall roughness must be the same as the roughness of the inner cavity wall of the molding mold 7. In addition, optional but not limited to: the fiber felt layer can be glass fiber, glass fiber felt, etc., and the resin material can be selected and proportioned according to actual needs.

[0038] In an optional embodiment of this example, the axial length of the mandrel 2 is L1, the length of the tooling 1 along the axial direction of the mandrel 2 is L2, and the length of the molding die 7 is L3, satisfying: L1 = L2 + 1 / 4·L3, ensuring that the mandrel 2 can be inserted into the middle position of the molding zone of the molding die 7, so that the material is evenly distributed during the molding process, avoiding local over-thickness or under-thinness. Through precise positioning and uniform material distribution, the overall uniformity and consistency of the product can be improved, the scrap rate caused by molding defects can be reduced, and production efficiency and output can be improved.

[0039] Finally, it should be noted that the above embodiments and optional implementations in this specification are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing optional implementations, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. Furthermore, it is emphasized again that, in the absence of conflict, the features of the embodiments and optional implementations in the embodiments in this specification can be combined with each other.

Claims

1. A pultrusion tooling for a composite sandwich pipe, characterized in that It includes a tooling frame (1), a mandrel (2), an inner felt guide (3), an inner felt transition sleeve (4), a yarn mixing assembly (5), an outer felt guide (6), and a forming mold (7); The mandrel (2) is mounted on the tooling frame (1), and the mandrel (2) has an axially penetrating inner cavity inside; The inner felt guide (3), the inner felt transition sleeve (4), the yarn mixing assembly (5), and the outer felt guide (6) are arranged sequentially along the axial direction of the mandrel (2); The inner felt guide (3) is installed on the tooling frame (1) and located on one side of the mandrel (2) to guide the inner fiber felt layer (100) to cover the outer peripheral surface of the mandrel (2) to form an inner felt layer; The inner felt transition sleeve (4) is installed on the tooling frame (1) and fitted onto the outside of the mandrel (2) to stabilize the covering shape of the inner felt layer on the outer circumferential surface of the mandrel (2); The yarn mixing assembly (5) includes a yarn plate (51), an adjusting plate (52), and a yarn transition sleeve (53). The yarn plate (51) is located on the side of the inner felt transition sleeve (4). The yarn plate (51) has multiple yarn guide holes (511) for guiding the yarn (300) to run along the axial direction of the mandrel (2) on the outside of the inner felt layer. The adjusting plate (52) is installed on the tooling frame (1) and located on the rear side of the yarn plate (51). The yarn transition sleeve (53) is fixed to the adjusting plate (52) and fitted onto the outside of the mandrel (2). The yarn transition sleeve (53) is used to guide the yarn (300) to cover the outside of the inner felt layer to form a yarn layer. The adjusting plate (52) is used to adjust the eccentric angle between the axis of the yarn transition sleeve (53) and the axis of the mandrel (2). The outer felt guide (6) is installed on the tooling frame (1) and located on one side of the mandrel (2) to guide the outer fiber felt layer (200) to cover the outer side of the yarn layer to form an outer felt layer, forming a preformed tube consisting of mandrel (2), inner felt layer, yarn layer and outer felt layer from the inside to the outside. The forming mold (7) has an axially penetrating inner cavity inside. The forming mold (7) is located on one side of the mandrel (2), and the axis of the inner cavity of the mold is coaxial with the axis of the inner cavity of the mandrel. The inner cavity of the mold is used to insert the preformed tube.

2. The composite material sandwich tube pultrusion tooling according to claim 1, characterized in that, The cavity openings of both the inner felt guide (3) and the outer felt guide (6) are flared mouths with an inlet inner diameter larger than the outlet inner diameter.

3. The composite material sandwich tube pultrusion tooling according to claim 1, characterized in that, The mandrel (2) is fitted with a plurality of mandrel sleeves (21), which are fixedly installed on the tooling frame (1).

4. The composite material sandwich tube pultrusion tooling according to claim 1, characterized in that, The inner felt guide (3) has an inner felt guide wheel (8) on the fiber felt layer inlet side, which is used to guide the inner fiber felt layer into the inner felt guide (3).

5. The composite material sandwich tube pultrusion fixture according to claim 1, characterized in that, The outer felt guide (6) is provided with an outer felt guide wheel (9) on the fiber felt layer inlet side, which is used to guide the outer fiber felt layer into the outer felt guide (6).

6. The composite material sandwich tube pultrusion tooling according to claim 1, characterized in that, The inner felt guide (3) and the outer felt guide (6) are respectively located on opposite sides of the mandrel (2) in the radial direction.

7. The composite material sandwich tube pultrusion tooling according to claim 1, characterized in that, The yarn board (51) is fitted onto the outside of the inner felt transition sleeve (4), and the portion located on the radially opposite sides of the inner felt transition sleeve (4) has a plurality of yarn guide holes (511).

8. The pultrusion fixture for composite sandwich tubes according to claim 1, characterized in that, The mandrel (2) is a hollow steel pipe structure.

9. The composite material sandwich tube pultrusion tooling according to claim 1, characterized in that, The axial length of the mandrel (2) is L1, the length of the tooling frame (1) along the axial direction of the mandrel (2) is L2, and the length of the molding die (7) is L3, satisfying: L1=L2+1 / 4·L3.

10. A pultrusion method for composite sandwich tubes, using the composite sandwich tube pultrusion fixture according to any one of claims 1-9, characterized in that, The pultrusion method includes the following steps: The inner fiber felt layer (100) is wrapped around the outer periphery of the mandrel (2) by the inner felt guide (3) to form an inner felt layer, and the mandrel (2) covered with the inner felt layer passes through the inner felt transition sleeve (4); the yarn (300) is passed through the yarn plate (51) and the yarn transition sleeve (53) so that the yarn (300) is wrapped around the outside of the inner felt layer to form a yarn layer; the outer fiber felt layer (200) is wrapped around the outside of the yarn layer by the outer felt guide (6) to form an outer felt layer; thus a preformed tube is formed from the inside to the outside, consisting of mandrel (2), inner felt layer, yarn layer and outer felt layer; Insert the preformed pipe into the mold cavity of the forming mold (7); The molding die (7) is divided into molding zone 1, molding zone 2 and molding zone 3 along the pultrusion direction. The temperature of molding zone 1 is set to make the resin system in a viscous flow state. The temperature of molding zone 2 is higher than that of molding zone 1 to accelerate the resin crosslinking reaction. The temperature of molding zone 3 is lower than that of molding zone 2 to relax stress and final shape. Start the pultrusion equipment to continuously pull and place the resin material in the molding zone 1 of the molding die (7). Inject the core material into the inner cavity of the mandrel (2) from one end, and let the core material overflow along the inner cavity of the mandrel. Then, let the resin material, the preformed tube and the core material pass through the molding zone 1, molding zone 2 and molding zone 3 of the molding die (7) together, and complete the impregnation, cross-linking and final curing under the action of temperature gradient to obtain an integrated composite sandwich tube.

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