A method for forming a pin-jointed large-opening solid rocket engine composite case

Abstract

The application discloses a pin-connection large-opening solid rocket engine composite shell forming method, and comprises the following steps: preparing front and rear joints with sealing inserts; preparing a cylinder segment winding tool; assembling a winding core and performing surface treatment; preparing a shell fiber winding layer; curing the shell; and machining the shell, so as to obtain a pin-connection large-opening solid rocket engine composite shell. The forming method has good process performance, and the reliability of the connection between the large-opening composite shell and other cabin segments or end covers is improved by adopting a double-row radial pin connection method. Meanwhile, the sealing performance of the shell is further ensured by arranging the sealing inserts, and the winding process is simple and efficient without the complex operation of circumferential winding and laying-up of the prepreg leveling on the surface of the winding core.

Description

Technical Field

[0001] This invention relates to the field of solid rocket motor composite material casing manufacturing, and specifically to a method for forming a solid rocket motor composite material casing with a large pin-joint opening. Background Technology

[0002] The use of composite material housings can improve the engine's mass-to-weight ratio. Existing composite material housings are widely used in large-diameter engines, but their application in small and medium-diameter engines with large length-to-diameter ratios is somewhat limited. The requirement for large openings or even full openings in the housing of such engines is one of the reasons for the limited application of composite materials.

[0003] Solid rocket motor composite shells are typically formed by longitudinal and circumferential fiber winding. However, in the head, only a longitudinal fiber winding layer exists. Enlarging the opening reduces the head's strength, necessitating additional reinforcement to prevent low-stress failure. Furthermore, for large-opening shells with relatively large polar holes at both ends, variations in the winding angle exceeding a certain value can lead to problems such as yarn slippage and unstable yarn shape during winding. Currently, wet winding processes are mainly used, employing a small-angle (9°–12°) longitudinal winding method, as seen in patent CN11070734A. For headless winding methods, metal hanging rings are generally used, as in patent CN110978558A. However, these winding methods often require leveling the winding mandrel using fiber prepreg or circumferential winding to make its surface smoother for easier winding layer preparation, making the process relatively complex. In addition, for large-opening composite material shells with end caps, the end caps and shells are often bonded together, as in patent CN110744832A. This effectively reduces structural mass and increases the loading space, but defects are prone to occur in the bonding area, leading to a reduction in structural strength and failing to fully utilize the high load-bearing capacity of the composite material. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention aims to provide a method for forming a composite material shell for a large-aperture solid rocket motor with pins. This method eliminates the need for ramp winding or prepreg laying and leveling operations, and enhances the reliability of the connection between the large-aperture composite material shell and other sections or heads by adopting a double-row radial pin connection method. At the same time, the sealing performance of the shell is further ensured by setting sealing inserts.

[0005] The specific technical solution of the present invention is as follows:

[0006] A method for molding a composite material shell for a solid rocket motor with a large pin-joint opening, the molding method comprising the following steps:

[0007] S1. Preparation of front and rear connectors with sealing inserts

[0008] The "L"-shaped metal sealing rings are embedded into the front and rear joints by laying carbon fiber prepreg and finally molding them to obtain front and rear joints with sealing inserts.

[0009] S2. Prepare the cylindrical section winding fixture.

[0010] The insulation layer green sheet is rolled to a suitable thickness, cut and wrapped on the surface of the cylindrical core mold; the inner surface of the conical section of the front and rear joints prepared in step S1 and the outer surface of the conical section of the insulation layer are roughened and then bonded to form a cylindrical winding tooling.

[0011] S3. Winding mandrel assembly and surface treatment

[0012] The cylindrical section winding fixture obtained in step S2 is assembled with the front and rear end cap fixtures to form a winding mandrel, and a layer of adhesive is evenly applied to the entire winding area on the surface of the winding mandrel.

[0013] S4. Preparation of the shell fiber winding layer

[0014] The designed layup is wound onto the winding mandrel after surface treatment in step S3 to obtain a fiber winding layer;

[0015] S5, Shell Curing

[0016] The shell that has been wound in step S4 is placed in a curing oven for curing. After curing, it is demolded to form a composite material shell with a cap.

[0017] S6, Shell Machining

[0018] Cut the end caps of the composite material shell with end caps obtained in step S5, remove the front and rear end cap fixtures, drill radial pin holes in the front and rear joints, and then process the sealing inserts in place according to the sealing performance requirements, finally obtaining the pin-connected large-opening solid rocket motor composite material shell.

[0019] In this case, the winding mandrel obtained in step S3 does not require surface leveling during the winding process.

[0020] Preferably, the inner surface of the conical section of the front and rear connectors with sealing inserts prepared in step S1 is a small-tapered conical surface with a taper range of 1° to 3°, so as to match and form the cylindrical section winding tooling described in step S2.

[0021] Preferably, the sealing inserts in the front connector and the rear connector with sealing inserts are made of metal, the sealing inserts are provided with a step that overlaps with the insulation layer, the axial width of the sealing inserts is 15-35mm, and the width of the step is 5-10mm.

[0022] The sealing insert is used for sealing the structure, and its inner surface is machined after the composite material shell is integrally formed to meet the sealing performance requirements.

[0023] Preferably, the insulation layer material is EPDM rubber and is bonded to the sealing insert.

[0024] Furthermore, the composite material shell is provided with radial pin holes, which are double-row pins used to connect with other sections or heads. The number of radial pin holes is selected according to the specific load conditions.

[0025] Preferably, the spacing between the radial pin hole axes is greater than twice the hole diameter;

[0026] Preferably, the composite material housing uses Φ12mm double-row pins, the distance between the radial pin hole axes is 30mm, and the distance between the pins and the end face of the front connector with sealing insert or the rear connector with sealing insert is 25mm.

[0027] Furthermore, the winding angle of the composite material shell in step S3 can be designed by adjusting the front and rear end cap holes;

[0028] Preferably, the front and rear end cap fixtures adopt a front and rear equal-pole hole scheme.

[0029] Furthermore, the ratio of the front and rear pole holes can be adjusted according to the axial stiffness requirements of the composite material shell.

[0030] Preferably, when the composite material shell has large openings at both ends, it is wound with equal-polarity holes at a winding angle of 12°.

[0031] Furthermore, when a single-sided end cap is retained, the retained end cap is reinforced during the winding process to form a single-sided large-opening composite material shell.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The molding method disclosed in this invention not only has good processability, but also the double-row radial pin connection method effectively improves the connection reliability of the composite shell with other compartments or heads. The designed sealing insert ensures that the composite shell has good sealing performance. At the same time, there is no need for complex operations such as circumferential winding and laying prepreg for leveling during the winding process, making the process simple and efficient. Attached Figure Description

[0034] To more clearly illustrate the technical solutions disclosed in this invention, the accompanying drawings used in some embodiments of this invention will be briefly described below. Obviously, the drawings described below are merely drawings of some embodiments of this invention, and those skilled in the art can obtain other drawings based on these drawings. Furthermore, the drawings described below can be considered schematic diagrams and are not intended to limit the actual dimensions of the products or the actual flow of the methods involved in the embodiments of this invention.

[0035] Figure 1 This is a schematic diagram of a composite material shell structure for a large-opening solid rocket motor with pin joint, provided as an embodiment of the present invention.

[0036] Figure 2 This is a schematic diagram of the assembled winding mandrel provided in an embodiment of the present invention.

[0037] Figure 3 The connector type with sealing insert provided in the embodiment of the present invention.

[0038] The attached figures are labeled as follows:

[0039] 1. Front connector with sealing insert; 2. Rear connector with sealing insert; 3. Fiber wound layer; 4. Insulation layer; 5. Front end tooling; 6. Rear end tooling; 7. Front end positioning nut; 8. Rear end positioning nut; 9. Winding spindle; 10. Sealing insert. Detailed Implementation

[0040] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0041] This invention provides a method for molding a composite material shell for a solid rocket motor with a large pin-joint opening. The molding method includes the following steps:

[0042] S1. Preparation of front and rear connectors with sealing inserts

[0043] The "L"-shaped metal sealing rings are embedded into the front and rear joints by laying carbon fiber prepreg and finally molding them to obtain front and rear joints with sealing inserts.

[0044] The inner surface of the tapered section of the front and rear connectors with sealing inserts is a small-tapered conical surface with a taper range of 1° to 3°, in order to match and form the cylindrical section winding tooling described in step S2;

[0045] S2. Prepare the cylindrical section winding fixture.

[0046] The insulation layer green sheet is rolled to a suitable thickness, cut and wrapped on the surface of the cylindrical core mold; the inner surface of the conical section of the front and rear joints prepared in step S1 and the outer surface of the conical section of the insulation layer are roughened and then bonded to form a cylindrical winding tooling.

[0047] The sealing inserts in the front connector and the rear connector with sealing inserts are made of metal. The sealing inserts have a step that overlaps with the insulation layer. The axial width of the sealing inserts is 15-35 mm, and the width of the step is 5-10 mm.

[0048] The insulation layer material is EPDM rubber, and it is bonded to the sealing insert.

[0049] S3. Winding mandrel assembly and surface treatment

[0050] The cylindrical section winding fixture obtained in step S2 is assembled with the front and rear end cap fixtures to form a winding mandrel, and a layer of adhesive is evenly applied to the entire winding area on the surface of the winding mandrel.

[0051] No surface leveling is required for the winding mandrel during the winding process;

[0052] The front and rear end cap fixtures adopt a front and rear equal polar hole scheme. The front and rear equal polar hole ratio of the front and rear end cap fixtures is designed according to the axial stiffness requirements of the composite material shell.

[0053] S4. Preparation of the shell fiber winding layer

[0054] The designed layup is wound onto the winding mandrel after surface treatment in step S3 to obtain a fiber winding layer;

[0055] The winding angle of the fiber winding layer is matched with the polar holes of the front and rear end cap tooling;

[0056] Preferably, when the composite material shell has large openings at both ends, it is wound with equal polarity holes at a winding angle of 12°.

[0057] S5, Shell Curing

[0058] The shell that has been wound in step S4 is placed in a curing oven for curing. After curing, it is demolded to form a composite material shell with a cap.

[0059] S6, Shell Machining

[0060] Cut the end caps of the composite material shell with end caps obtained in step S5, remove the front and rear end cap fixtures, drill radial pin holes in the front and rear joints, and then process the sealing inserts in place according to the sealing performance requirements, finally obtaining the pin-connected large-opening solid rocket motor composite material shell.

[0061] The sealing insert is used for sealing the structure, and its inner surface is machined after the composite material shell is integrally formed to meet the sealing performance requirements.

[0062] The composite material shell is provided with radial pin holes, which are double-row pins used for connection with other sections or heads. The number of radial pin holes is selected according to the specific load conditions. The spacing between the axes of the radial pin holes is greater than twice the hole diameter. Preferably, the composite material shell uses Φ12mm double-row pins, the spacing between the axes of the radial pin holes is 30mm, and the distance between the pin holes and the end face of the front or rear joint with sealing insert is 25mm.

[0063] When a single-sided end cap is retained, the retained end cap is reinforced during the winding process to form a single-sided large-opening composite material shell.

[0064] Example 1

[0065] This embodiment provides a method for molding a composite material shell for a large-aperture solid rocket motor with pin joints. The molding method includes: preparing front and rear joints with sealing inserts; preparing a cylindrical section winding tooling; assembling a winding mandrel and performing mandrel surface treatment; preparing a shell fiber winding layer; curing the shell fiber winding layer in a furnace; and machining the shell.

[0066] The pressure-bearing structure of the large-opening composite material shell is designed based on the design pressure of the solid rocket engine combustion chamber shell. The specific process is as follows:

[0067] First, the winding mandrel of the shell has a dummy end cap, and the radii of its front and rear polar holes are adjusted by the mandrel design to control the winding angle. For composite shells with a large aspect ratio, axial stiffness is also an important performance indicator. Therefore, a small-angle helical winding is used to enhance the axial stiffness of the shell, while a geodesic winding scheme with equal front and rear polar holes is adopted to ensure stable winding profile. Thus, the diameters of both front and rear polar holes are 20mm, the outer diameter of the cylinder section is 230mm, and the helical winding angle is calculated using the following formula:

[0068]

[0069] The calculation shows that the helical winding angle is 5°. Equations (2) and (3) are used to calculate the helical fiber winding thickness hα and the circumferential fiber winding thickness hθ. The calculation formulas are as follows, where the safety factor K... safe Take 1.5:

[0070]

[0071] After substituting data such as fiber strength, the calculation results show that there are 10 spiral layers, 7 circumferential layers, and a shell thickness of 2.6 mm.

[0072] After the shell is formed, the cylindrical section bears pressure. The blast pressure of the cylindrical section is calculated using formula (4), and the blast pressure of the spiral layer is 33.75 MPa, and the blast pressure of the circumferential layer is 37.14 MPa. Therefore, the comprehensive blast pressure of the shell under this ply design scheme reaches 33.75 MPa.

[0073]

[0074] The molding method provided in this embodiment ultimately yields a pin-jointed, large-opening solid rocket motor composite material shell structure, as shown in the example. Figure 1 As shown, the composite material shell includes: a front connector 1 with a sealing insert, a rear connector 2 with a sealing insert, a fiber winding layer 3, and an insulation layer 4.

[0075] In the molding method, the inner conical surfaces of the front connector 1 and the rear connector 2 with sealing inserts, and the outer conical surfaces of the insulation layer 4 are roughened and then bonded together with 730 adhesive to form a cylindrical winding fixture. The front connector 1 and the rear connector 2 with sealing inserts are cylindrical with tapered inner surfaces, with a tapered range of 1° to 3°, to match and form the aforementioned cylindrical winding fixture. The cylindrical winding fixture, together with the front end fixture 5, the rear end fixture 6, the front end positioning nut 7, the rear end positioning nut 8, and the winding spindle 9, assembles the winding mandrel. Figure 2 As shown, a layer of H2 adhesive is evenly applied to the entire winding area; the winding mandrel does not require surface leveling during the winding process.

[0076] In addition, the sealing insert 10 is pre-placed in the joint, and its form is as follows: Figure 3 As shown, carbon fiber prepreg is laid according to the design parameters of the front and rear joint structures. The layup is generally symmetrical and then molded to obtain the front joint 1 with sealing insert and the rear joint 2 with sealing insert. The sealing insert 10 is made of metal and has a step that overlaps with the insulation layer 4. The sealing insert 10 is used for sealing structure, and its inner surface is machined after the composite material shell is integrally formed to meet the sealing performance requirements.

[0077] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make possible variations and modifications to the technical solutions of the present invention based on the disclosed content without departing from the spirit and scope of the invention. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the present invention. The protection scope of the present invention is defined by the appended claims.

Claims

1. A method for molding a composite material shell for a solid rocket motor with a large opening and pin joint, characterized in that, The molding method includes the following steps: S1. Preparation of front and rear connectors with sealing inserts The "L"-shaped metal sealing ring is embedded into the front and rear joints by laying carbon fiber prepreg and finally molding to obtain the front and rear joints with sealing inserts. S2. Prepare the cylindrical section winding fixture. The insulation layer green sheet is rolled to a suitable thickness, cut and wrapped on the surface of the cylindrical core mold; the inner surface of the conical section of the front and rear joints prepared in step S1 and the outer surface of the conical section of the insulation layer are roughened and then bonded to form a cylindrical winding tooling. S3. Winding mandrel assembly and surface treatment The cylindrical section winding fixture obtained in step S2 is assembled with the front and rear end cap fixtures to form a winding mandrel, and a layer of adhesive is evenly applied to the entire winding area on the surface of the winding mandrel. S4. Preparation of the shell fiber winding layer The designed layup is wound onto the winding mandrel after surface treatment in step S3 to obtain a fiber winding layer; S5, Shell Curing The shell that has been wound in step S4 is placed in a curing oven for curing. After curing, it is demolded to form a composite material shell with a cap. S6, Shell Machining Cut the end caps of the composite material shell with end caps obtained in step S5, remove the front and rear end cap fixtures, drill radial pin holes in the front and rear joints, and then process the sealing inserts in place according to the sealing performance requirements, finally obtaining the pin-connected large-opening solid rocket motor composite material shell.

2. The composite material shell molding method according to claim 1, characterized in that, The inner surface of the conical section of the front and rear connectors with sealing inserts prepared in step S1 is a small-tapered conical surface with a taper range of 1° to 3°, in order to match and form the cylindrical section winding tooling described in step S2.

3. The composite material shell molding method according to claim 1, characterized in that, The winding mandrel obtained in step S3 does not require surface leveling during the winding process.

4. The composite material shell molding method according to claim 1, characterized in that, The sealing inserts in the front and rear connectors with sealing inserts are made of metal. The sealing inserts have a step that overlaps with the insulation layer. The axial width of the sealing insert is 15-35 mm, and the width of the step is 5-10 mm.

5. The composite material shell molding method according to claim 1 or 4, characterized in that, The sealing insert is used for sealing the structure, and its inner surface is machined after the composite material shell is integrally formed to meet the sealing performance requirements.

6. The composite material shell molding method according to claim 1, characterized in that, The composite material shell is provided with radial pin holes, which are double-row pins used to connect with other sections or heads. The number of radial pin holes is selected according to the specific load conditions.

7. The composite material shell molding method according to claim 6, characterized in that, The spacing between the radial pin hole axes is greater than twice the hole diameter.

8. The composite material shell molding method according to claim 1, characterized in that, In step S3, the front and rear end cap fixtures adopt a front and rear equal polar hole scheme, and the front and rear polar hole ratio is adjusted according to the axial stiffness requirements of the composite material shell.

9. The composite material shell molding method according to claim 1 or 4, characterized in that, The winding angle of the composite material shell in step S3 is designed by adjusting the front and rear end cap holes.

10. The composite material shell molding method according to claim 1, characterized in that, When a single-sided end cap is retained, the retained end cap is reinforced during the winding process to form a single-sided large-opening composite material shell.

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