Manufacturing method of composite material circular pipe end internal thread and force bearing shell

Abstract

A method for manufacturing internal threads at the end of a composite circular tube and a bearing shell, and the method comprises the following steps: after a layer of axis yarn is laid on a core mold with external threads at two ends by a fiber laying head of a laying and winding machine, the fiber laying head is stopped at one end of the core mold; a winding head is used for winding the laid axial yarn according to the set screw pitch, after the winding yarn reaches the inner end of the thread, the winding yarn is wound at the thread for several circles with the screw pitch the same as that of the thread, and then a section of yarn is drawn out of the winding yarn from the winding head to be cut off and penetrates through the axial yarn cluster; then, the fiber placement head is started to perform fiber placement in the opposite direction, the fiber placement head is stopped at the other end of the core mold after one layer of fiber is laid, then the cut surrounding yarn is connected, the surrounding head is started to move in the opposite direction, surrounding is implemented, and the actions are repeated until all winding work is completed. When the composite material high-strength pipe fitting manufactured through the method is used for a large-opening solid rocket engine, the weight of a shell can be obviously reduced, and the reliability of connection between the shell and other related parts can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of composite materials, and particularly relates to a method for manufacturing internal threads at the end of a composite material round tube and a load-bearing shell. Background Art

[0002] The combustion chamber of a straight-cylinder solid rocket is very much like a tube. The inner side of the tube is an insulating layer made of consumable temperature-limiting insulation materials to prevent the high temperature in the combustion chamber from being transmitted to the outside during operation. The outer side of the tube is a load-bearing layer, which is mainly made of high-strength metal materials or composite materials to withstand the high pressure generated when the engine is working. In the past, the load-bearing layers of straight-cylinder solid rocket combustion chambers were all made of metal materials by spinning. With the increasing maturity of high-strength fiber materials such as carbon fiber materials, composite material load-bearing layers are becoming more and more popular. However, due to the limitations of composite material manufacturing technology, the connection between the two ends of the load-bearing layer of the composite straight-cylinder solid rocket combustion chamber still needs to rely on metal inserts, that is, there is no straight section of the solid rocket combustion chamber that is truly made entirely of composite materials. This is mainly because the current composite manufacturing technology cannot directly make continuous fiber-reinforced high-strength internal threads. Even where threads are required, they are all made by mechanical processing, because part of the fibers at the thread must be cut off during mechanical processing, resulting in a very low connection strength of such threads and cannot be used in high-stress occasions. Helplessly, people can only embed metal connectors at both ends of the tube by special winding methods. The straight section of a composite straight-tube solid rocket combustion chamber with metal inserts has a complex manufacturing process, a long manufacturing cycle, poor reliability and high production cost. Summary of the invention

[0003] The object of the present invention is to provide a method for manufacturing the internal thread of the end of a composite material round tube and a load-bearing shell to solve the above-mentioned problem.

[0004] To achieve the above object, the present invention adopts the following technical solutions: A method for manufacturing an internal thread at the end of a composite material round tube, comprising: After a layer of axial yarn is laid on a core mold with external threads at both ends by using a laying head of a laying winding machine, the laying head stops at one end of the core mold; Use a wrapping head to wrap around the laid axial yarn at a set pitch. After the wrapping yarn reaches the inner end of the thread, wrap around the thread several times at the same pitch as the thread. Then, pull out a section of the wrapping yarn from the wrapping head, cut it off, and pass it through the axial yarn bundle. Then start the wire laying head to lay the wire in the opposite direction. After laying one layer, the wire laying head stops at the other end of the core mold, and then connect the cut winding yarn, start the winding head to move in the opposite direction and implement winding, and repeat the above actions until all the winding work is completed.

[0005] Furthermore, the laid axial yarn at the end of each round advances only a few turns on the thread.

[0006] Furthermore, the wrapping head pulls the axial yarn outside the innermost several turns of the thread into the thread groove of the core mold according to the pitch of the thread, and then a section of the wrapping yarn is pulled out from the wrapping head, cut off and passed through the axial yarn bundle for tensioning.

[0007] Furthermore, the surface of the internal thread tooth shape is composed of the folded-back ends of each layer of axial yarn and the resin.

[0008] Furthermore, every two layers of axial yarns independently occupy the inner surface of one to several turns of the thread.

[0009] Furthermore, the internal thread is a tapered thread.

[0010] Furthermore, the thread diameter of the internal thread is smaller than the inner diameter of the middle section of the circular tube.

[0011] Furthermore, the core mold is made of a relatively active metal tube, and after the wrapping is completed and solidified, the core mold is removed by electrochemical corrosion.

[0012] Furthermore, the core mold is made by wrapping T800-12K carbon fiber and low-viscosity high-strength thermosetting epoxy resin.

[0013] A load-bearing shell is manufactured by the method for manufacturing the internal thread at the end of a composite material round tube.

[0014] Compared with the prior art, the present invention has the following technical effects: The composite load-bearing shell of the straight-cylindrical solid rocket engine combustion chamber manufactured according to the technical solution of the present invention is completely made of carbon fiber composite materials. The connecting internal threads at both ends are formed by a one-time laying and winding process rather than mechanical processing, and have high mechanical strength and safety. In particular, the longitudinal fibers on the surface of the internal threads are all the folded ends of a certain layer of longitudinal fibers. Therefore, when the internal threads are subjected to outward pulling force, the threads will directly apply the force to the longitudinal fibers of each layer. The straight tube made by this method can be used as the load-bearing shell of a straight-cylindrical solid rocket combustion chamber with a large opening, and can also be used as other tubular composite parts that require high-strength connections at both ends.

[0015] The longitudinal fibers on the surface of the internal thread of the present invention are all the folded-back ends of the longitudinal fibers of a certain layer. Therefore, when the internal thread is subjected to an outward pulling force, the thread will directly apply the force to the longitudinal fibers of each layer. The present invention puts an end to the history that continuous fiber reinforced composite materials cannot be directly made into threads. It provides a simple and reliable solution for the connection of composite pipe fittings. In particular, the high-strength composite pipe fittings made by this method can not only significantly reduce the weight of the shell when used in large-opening solid rocket engines, but also improve the reliability of the connection between the shell and other related parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of a common cylindrical thread of the present invention; Figure 2 It is a schematic diagram of the tapered thread of the present invention; Description of the code of the parts in the attached figure: 1——axial yarn, 2——circumferential yarn DETAILED DESCRIPTION The present invention is further described below in conjunction with the accompanying drawings: See also Figure 1 , a load-bearing shell of a large-opening solid rocket combustion chamber made of carbon fiber composite material, with an outer diameter of 70mm, a wall thickness of 2mm, and an internal thread with a tooth height of 0.7mm and a pitch of 2mm at each end. It is made by using a tubular laying and winding machine and a block-type core mold described in CN 113386329 B or CN 114148835 A, and is laid and wound with T800-12K carbon fiber and low-viscosity, high-strength thermosetting epoxy resin. The effective section of the core mold is generally cylindrical with a diameter of ￠66mm, with an internal thread at each end, and a precise multi-petal splicing structure. When axially laying and wrapping the non-threaded section with the surrounding head, each axial yarn 1 is subjected to a tension of 5N, and the surrounding yarn is subjected to a tension of 60N; when axially laying and wrapping the head around the threaded section, each axial yarn 1 is subjected to a tension of 1N, and the surrounding yarn is subjected to a tension of 100N; First, each axial yarn 1 is subjected to 1N tension for axial laying from one end. After the laying head reaches the other end, the winding head will use the winding yarn with 100N tension to pull the axial yarn 1 outside the innermost three turns of thread into the thread groove of the core mold according to the pitch of the thread. Then the tension of the single axial yarn 1 is increased to 5N, and the hoop yarn 2 is hoop wound with a tension of 60N and the pitch designed for equal strength. When the winding head winds to the opposite thread end, the program control reduces the axial yarn tension to 1N and increases the winding yarn tension to 100N. The winding head pulls the axial yarn outside the innermost three turns of thread into the thread groove of the core mold according to the pitch of the thread. Then a section of the winding yarn is pulled out from the winding head, cut, and passed through the axial yarn bundle for tensioning; Then the tension of the single axial yarn is increased to 5N for reverse winding, and the hoop yarn 2 is also wound hoopwise at a tension of 60N and according to the pitch designed for equal strength. When the winding head winds to the opposite end of the thread, the program control reduces the tension of the axial yarn to 1N and increases the tension of the hoop yarn to 100N. The winding head winds to the sixth turn of the thread according to the pitch of the thread, and then a section of the hoop yarn is pulled out from the winding head, cut off, and passed through the axial yarn bundle for tensioning; Then the tension of the single axial yarn is increased to 5N for reverse winding, and the hoop yarn is also wound hoopwise at a tension of 60N and according to the pitch designed for equal strength. Each layer advances three turns after reaching the turning point at the end of the previous layer, and the above actions are repeated until all winding work is completed.

[0017] Then the wrapping yarn is cut and knotted, the axial yarn is cut, and the laying and wrapping piece together with the core mold are removed from the laying and wrapping machine and placed in an oven for heating and curing. After 24 hours of curing, the locking piece of the spliced ​​core mold is unscrewed and the core mold is removed from the composite tube.

[0018] In general, the thread profile is flush with the tube wall; for rocket shells, the thread profile can protrude from the inner wall of the tube, that is, the thread diameter can be smaller than the inner diameter of the straight section of the tube; in special cases, similar attachments can be used. Figure 2 Tapered threads shown.

[0019] For the requirement of rapid manufacturing, the tubular laying machine described in CN118700588A can be used and a continuous fiber thermoplastic resin impregnation line can be used for laying.

[0020] For small batch processing, the core mold can be made of a more active metal tube. After the wrapping is completed and solidified, the core mold is removed by electrochemical corrosion.

[0021] The method of the present invention ends the history that continuous fiber reinforced composite materials cannot be directly made into internal threads. It provides a simple and reliable solution for the connection of composite pipe fittings. In particular, when the composite high-strength pipe fittings made by this method are used in large-opening solid rocket engines, they can not only significantly reduce the weight of the shell, but also improve the reliability of the connection between the shell and other related parts.

[0022] This method successfully forms internal threads directly inside the carbon fiber composite shell through a specific laying process, which solves the technical problem that continuous fiber reinforced composite materials cannot directly make internal threads. This breakthrough provides a new, simple and reliable solution for the connection of composite pipes.

[0023] Improved housing strength and reliability: Using T800-12K carbon fiber and low-viscosity high-strength thermosetting epoxy resin as materials, combined with a precise laying and winding process, the shell has high strength and excellent durability. Especially in the application of large-opening solid rocket engines, this high-strength pipe can significantly withstand high pressure and high temperature environments, improving the reliability and service life of the engine.

[0024] Carbon fiber composite materials have the characteristics of low density and high strength, so shells made of this material can significantly reduce weight compared to traditional metal shells. This is undoubtedly a huge advantage for spacecraft that need to strictly control weight.

[0025] The design of internal thread makes the connection between the housing and other related parts simpler and more reliable. Through threaded connection, the strength and sealing of the connection can be ensured, avoiding leakage or failure caused by improper connection.

[0026] This method can adjust the thread profile, pitch and other parameters according to actual needs to meet the needs of different application scenarios. At the same time, different laying and winding machines and materials can be selected according to production needs to achieve rapid manufacturing or small batch processing.

[0027] For small batch processing, the solution proposes to use a more active metal tube to make the core mold, and remove the core mold by electrochemical corrosion after the wrapping is completed and solidified. This innovative core mold removal method not only simplifies the production process, but also reduces production costs.

[0028] Promoted the development of composite materials technology: This method not only provides new ideas for the production of high-strength pipes such as rocket engine casings, but also promotes the widespread application and development of composite materials technology in aerospace, aviation and other fields.

[0029] In summary, the method for manufacturing the large-opening solid rocket combustion chamber load-bearing shell made of carbon fiber composite materials described in this technical scheme has significant technical effects and innovations, provides a simple and reliable solution for the manufacture and connection of composite pipe fittings, and is expected to be widely used in aerospace, aviation and other fields.

[0030] The above is only the most typical specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. The listed data are only for describing the working principle of the present invention and do not represent necessary values. Any technician in the field of composite materials who is familiar with fiber winding and fiber placement technologies can easily think of equivalent changes or replacements within the technical scope disclosed by the present invention, which should be covered within the scope of the claims of the present invention.

Claims

1. A method for manufacturing an internal thread at the end of a composite material round tube, characterized in that: include: After a layer of axial yarn is laid on a core mold with external threads at both ends by using a laying head of a laying winding machine, the laying head stops at one end of the core mold; Use a wrapping head to wrap around the laid axial yarn at a set pitch. After the wrapping yarn reaches the inner end of the thread, wrap around the thread several times at the same pitch as the thread. Then, pull out a section of the wrapping yarn from the wrapping head, cut it off, and pass it through the axial yarn bundle. Then start the wire laying head to lay the wire in the opposite direction. After laying one layer, the wire laying head stops at the other end of the core mold, and then connect the cut winding yarn, start the winding head to move in the opposite direction and implement winding, and repeat the above actions until all the winding work is completed.

2. The method for manufacturing the internal thread of the end of a composite material round tube according to claim 1, characterized in that: The laid axial yarn at the end of each round advances only a few turns on the thread.

3. The method for manufacturing the internal thread of the end of a composite material round tube according to claim 1, characterized in that: The wrapping head pulls the axial yarn outside the innermost several turns of thread into the thread groove of the core mold according to the pitch of the thread, and then pulls out a section of the wrapping yarn from the wrapping head, cuts it, and passes it through the axial yarn bundle for tensioning.

4. The method for manufacturing the internal thread of the end of a composite material round tube according to claim 1, characterized in that: The surface of the internal thread tooth shape is composed of the folded ends of each layer of axial yarn and resin.

5. The method for manufacturing the internal thread of the end of a composite material round tube according to claim 1, characterized in that: Every two layers of axial yarns independently occupy one to several turns of the inner surface of the thread.

6. The method for manufacturing the internal thread of the end of a composite material round tube according to claim 1, characterized in that: The internal thread is a tapered thread.

7. The method for manufacturing the internal thread at the end of a composite material round tube according to claim 1, characterized in that: The thread diameter of the internal thread is smaller than the inner diameter of the middle section of the round tube.

8. The method for manufacturing the internal thread at the end of a composite material round tube according to claim 1, characterized in that: The core mold is made of a relatively active metal tube. After the wrapping is completed and solidified, the core mold is removed by electrochemical corrosion.

9. The method for manufacturing the internal thread of the end of a composite material round tube according to claim 1, characterized in that: The core mold is made of T800-12K carbon fiber and low-viscosity and high-strength thermosetting epoxy resin.

10. A load-bearing shell, characterized in that: The composite material is manufactured by the method for manufacturing the internal thread at the end of a round tube of composite material as described in any one of claims 1 to 9.

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