Forming method of composite shell of fixed submersible all-composite engine nozzle

Abstract

The present invention provides a molding method for a fixed submersible all-composite engine nozzle composite shell, comprising: S1, nozzle winding assembly molding; S2, cleaning the molding tool surface and pasting a release cloth on the surface; S3, with the throat liner facing downward, the nozzle winding assembly is fixedly assembled on the molding tool upside down; S4, prepreg layering and pre-pressing of the lower section of the composite shell; S5, precuring molding: curing the lower section of the composite shell at the design temperature and pressure, and simultaneously vacuuming; S6, demoulding and surface treatment; S7, prepreg layering and pre-pressing of the upper section of the composite shell; S8, curing molding: curing the upper section of the composite shell at the design temperature and pressure, and simultaneously vacuuming to obtain the composite shell; S9, machining: machining the composite shell to meet the design requirements. A fixed submersible all-composite engine nozzle composite shell with light weight, stable performance, strong load-bearing capacity and meeting the design requirements is prepared by this molding method.

Description

Technical Field

[0001] The present invention belongs to the technical field of all-composite nozzles, and in particular relates to a method for forming a composite shell of a fixed submersible all-composite engine nozzle. Background Art

[0002] With the continuous improvement of the technological requirements for weapons and equipment, higher requirements are placed on various advanced weapons and equipment components, such as lightweight and multifunctionality.

[0003] The engine nozzle is the most challenging part of a solid rocket engine's operating environment. It must withstand the erosion and ablation of high-temperature, high-pressure, and high-velocity combustion gases during operation, resulting in a complex stress environment. Due to the uneven deformation of the metal nozzle shell and diffuser during operation, this contact area can lead to an unbalanced stress distribution at the bonding area between the nozzle shell and diffuser, exacerbating stress concentration in the bonding area and potentially causing damage in severe cases. Improving the overall structural performance of the engine nozzle depends on improving the performance of the nozzle shell. Existing engine nozzles mostly use metal shells, which have a high passive mass and are not conducive to improving the mass ratio of solid rocket engines.

[0004] High-strength, lightweight composite nozzle shells can gradually replace metal ones, effectively reducing engine costs and enabling rapid prototyping. However, the key steps in nozzle composite shell molding are manual prepreg layup and autoclave curing. The prepreg layup angle, cutting method, composite shell interface, curing method, and curing schedule all affect composite shell performance. Therefore, addressing the thermal expansion stress and unreliable curing interface caused by multiple curing cycles in composite shells, as well as addressing the low structural strength and weak load-bearing capacity, are urgent issues that need to be addressed. Summary of the Invention

[0005] In response to the shortcomings of the prior art, the present invention aims to provide a method for forming a composite nozzle shell for a fixed submersible all-composite engine. This method produces a composite nozzle shell for a fixed submersible all-composite engine that has a novel structure, stable performance, and strong load-bearing capacity, meeting design requirements.

[0006] The present invention provides a method for forming a composite shell of a fixed submersible all-composite engine nozzle, comprising:

[0007] S1. Forming of nozzle winding assembly;

[0008] S2. Clean the surface of the molding tooling and stick a release cloth on the surface;

[0009] S3. With the throat lining facing downward, turn the nozzle winding assembly upside down and fix it on the forming tooling;

[0010] S4. Prepreg Laying and Prepressing of the Composite Shell Lower Section: The prepreg layers are cut and completely covered on the surface of the forming tooling and the diffuser section of the nozzle winding assembly according to the designed angle to form the composite shell lower section with a "7" cross-section. The composite shell is then vacuumed using a vacuum device.

[0011] S5. Pre-curing molding: The lower section of the composite shell equipped with a vacuum device is transferred into the autoclave together with the molding tool, and the lower section of the composite shell is cured at the designed temperature and pressure, and vacuumed at the same time;

[0012] S6, demoulding and surface treatment: cleaning the edges of the lower section of the composite shell and the molding tool that affect demoulding, separating the molding tool from the lower section of the composite shell, and cleaning the surface of the lower section of the composite shell after separation;

[0013] S7. Prepreg Laying and Prepressing of the Composite Shell Upper Section: The cut multi-layer prepreg is completely covered at the designed angle on the end face of the cured composite shell lower section and the position of the composite shell upper section corresponding to the diffuser section of the nozzle winding assembly to form an L-shaped composite shell upper section, and vacuumed using a vacuum device;

[0014] S8, curing and molding: transferring the upper section of the composite shell equipped with a vacuum pumping device into an autoclave, curing the upper section of the composite shell at a designed temperature and pressure, and simultaneously performing vacuum pumping to obtain a composite shell;

[0015] S9, machining: Machining the composite shell to make the size of the composite shell meet the design requirements.

[0016] Preferably, in step S1, the diffuser section of the nozzle winding assembly and the mating surface of the lower section of the composite shell are provided with a plurality of grooves; a smooth transition of the heat insulation layer is performed at the junction of the upper and lower end surfaces of the composite shell and the diffuser section of the nozzle winding assembly to avoid the existence of a triangular area; the large end face of the diffuser section of the nozzle winding assembly is flattened to ensure that the large end face is parallel to the end face of the throat liner and perpendicular to the axial direction of the nozzle winding assembly.

[0017] Preferably, in step S2, the surface of the forming tooling needs to be cleaned with lint-free paper and ethyl acetate, and then release cloth is affixed to the forming tooling and the diffusion section of the nozzle winding assembly and the laying working surface.

[0018] Preferably, in step S3, the forming tooling includes a sleeve and a top plate arranged at the upper end of the sleeve and a bottom plate arranged at the lower end of the sleeve, a through hole is opened in the middle of the top plate for the throat liner to extend into the interior of the sleeve, and there is a gap between the throat liner and the bottom plate; a support rod passing through the through hole is provided in the middle of the bottom plate, a positioning plate is provided at the upper end of the support rod, and a clamping space for clamping the diffusion section of the nozzle winding assembly is provided between the positioning plate and the top plate.

[0019] Preferably, in step S5, the prepreg layering and pre-pressing steps of the lower section of the composite shell specifically include:

[0020] S401, prepreg cutting, according to the cutting design requirements, cutting into 0° prepreg, +45° prepreg, -45° prepreg, and 90° prepreg;

[0021] S402, placing the assembled nozzle winding assembly and the forming tooling into an oven and preheating at 50°C for 1 hour;

[0022] S403, applying adhesive to the mating surfaces of the diffuser section of the nozzle winding assembly and the lower section of the composite shell;

[0023] S404, 0° prepreg layer 1, move the lower section of the composite shell corresponding to the diffuser section of the nozzle winding assembly 10mm toward the large end and mark it. Mark the diameter of the flange position of the molding tool end face + 10mm. Use the composite shell flange position and the corner position of the diffuser section of the nozzle winding assembly as the starting point. After the starting point is aligned, push it towards the large end of the diffuser section and the flange end face position until it is fully aligned. After the first line is completed, repeat this step to lay the next prepreg layer until the 0° prepreg is completely laid;

[0024] S405, +45° prepreg layup, using the nozzle wrap assembly diffuser section mark as a reference for pasting, pasting +45° prepreg from the large end to the small end, to the composite shell flange position and the diffuser section corner position, cutting a triangular notch at the corner position to ensure that there is no gap or overlap at the corner position;

[0025] S406, Flange Position Laying 1: Starting from the flange position marked on the tooling, lay the prepreg at the flange position, pushing and compacting from the outside to the inside. Cut triangular notches at the corners to ensure that there are no gaps or overlaps at the corners.

[0026] S407, 0° prepreg layer 2, the laying method is the same as S404 0° prepreg layer 1;

[0027] S408, -45° prepreg layup, the layup method is the same as S405 +45° prepreg layup;

[0028] S409, lay layer 2 at the flange position, in the same manner as S406, with the starting position offset by 45°;

[0029] S410, 90° prepreg layup, unidirectional fabric spirally wound to fix the diffuser section position of the nozzle winding assembly;

[0030] S411, lay layer 3 at the flange position, in the same manner as S406, with the starting position offset by 90°;

[0031] S412, vacuum pre-pressing, using a vacuum device to perform vacuum treatment, placing the entire body in an oven at 50°C while heating and vacuuming for 2 to 3 hours;

[0032] S413, Laying: 1) -45° prepreg laying, same as S408; 2) Flange position laying, same as S409, with the starting point offset 45° from S411; 3) 0° prepreg laying, same as S407; 5) +45° prepreg laying, same as S405; 6) Flange position laying, same as S406, with the starting point offset 90° from S411; 7) 0° prepreg laying, same as S404;

[0033] S414, vacuum pre-pressing, using a vacuum device to perform vacuum treatment, placing the entire body in an oven at 50°C while heating and vacuuming for 2 to 3 hours;

[0034] S415. Repeat the two sets of ply pre-pressing processes until the shell thickness meets the design requirements and has a margin of more than 2 mm.

[0035] Furthermore, in step S401, the prepreg is cut into pieces in the following manner:

[0036] Cut the 0° prepreg into 24 equal parts around the lower section of the composite shell, each with a 15° angle. Surface development is performed using 3D graphics software. After the dimensions are determined, the pieces are cut using an automatic cutting machine.

[0037] Cut the +45° prepreg material and divide the contact area between the lower section of the composite shell and the diffuser section of the nozzle winding assembly into three equal parts, each 120°. Surface unfolding is performed using 3D drawing software, and the lower end is extended by 10mm. After the size is determined, the automatic cutting machine is used to cut the pieces.

[0038] -45° prepreg blanking size determination method is the same as 45° prepreg blanking, the fiber direction of the cutting machine is opposite to 45°;

[0039] +45° prepreg / -45° prepreg is cut at the corresponding position of the composite shell flange. The root diameter and end face diameter of the composite shell flange are measured on the CAD drawing to determine the position and size of the composite shell flange before cutting on the automatic cutting machine;

[0040] 90° prepreg is cut into fiber strips with a width of 5mm and a length of 2000mm along the length direction of the unidirectional cloth fiber, with the length of 2000mm being the fiber length direction.

[0041] Preferably, in step S5, the pre-curing conditions are: room temperature → 50±5°C / 2h → 95±5°C / 6h → 50±5°C, the pressure in the autoclave is 0.1±0.02MPa → 2.8±0.2MPa / 11.5h → 0.1±0.02MPa, the pressure during heating and insulation is 2.8±0.2MPa, the heating rate is 0.2°C / min, the pressure rising rate is 0.05MPa / min, the cooling rate is 0.1°C / min, and the pressure reducing rate is 0.025MPa / min.

[0042] Preferably, in step S7, the prepreg layering and pre-pressing steps of the upper section of the composite shell specifically include:

[0043] S71, prepreg blanking, blanking method is the same as S401;

[0044] S72. Apply adhesive to the surfaces of the diffuser section of the nozzle wrap assembly and the upper section of the composite shell;

[0045] S73, laying, the laying method is the same as S404-S411;

[0046] S74, vacuum pre-pressing, using a vacuum device to perform vacuum treatment, placing the entire unit in an oven at 50°C while heating and vacuuming for 2 to 3 hours;

[0047] S75, laying, the laying method is the same as S413;

[0048] S76, vacuum pre-pressing, using a vacuum device to perform vacuum treatment, placing the whole in an oven at 50°C while heating and vacuuming for 2 to 3 hours;

[0049] S77. Repeat the two-group pre-pressing process until the shell thickness meets the design requirements and has a margin of more than 2 mm.

[0050] Furthermore, the prepreg is a carbon fiber reinforced epoxy resin prepreg.

[0051] Preferably, in step S8, the curing molding conditions are: room temperature → 80±5℃ / 2h → 120±5℃ / 2h → 135±5℃ / 2h → 160±5℃ / 4h → 60±5℃, when the temperature starts to rise, an initial pressure of 1MPa is added; the full pressure is 2.8MPa starting at 50℃, and the pressure is naturally reduced after the insulation at 160℃ is completed; the heating rate is 0.2℃ / min, the pressure rising rate is 0.05MPa / min, the cooling rate is 0.1℃ / min, and the pressure reduction rate is 0.025MPa / min.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] The present invention cuts unidirectional prepreg into required angles and sizes, then lays the prepregs of different angles and sizes on a composite shell forming tool in a corresponding laying sequence, performs pre-pressing and pre-curing, lays the upper end, and then transfers the rectified nozzle composite shell into an autoclave for final curing, pre-cures the lower section of the composite shell to form a composite shell upper section laying reference surface, and finally cures the upper section of the composite shell again after laying, heats to make the resin in the prepreg fluid, fills the spaces between the prepreg layers and slowly cures them, applies pressure to make the resin in the prepreg flow, and during the curing process, the layers are compacted so as not to generate delamination or pores, and no interface is generated between the lower section of the composite shell and the upper section of the composite shell. The produced composite nozzle shell has high structural strength.

[0054] The present invention addresses the problem of multi-step curing and multi-step processing of a nozzle composite shell with a complex structure. It adopts a pre-curing and final curing technology to avoid the thermal expansion stress and unreliable curing interface caused by multiple curing of the composite shell. At the same time, it reduces the production cycle of the all-composite nozzle and greatly improves the production capacity and working reliability of the all-composite nozzle. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 Schematic diagram of the all-composite engine nozzle composite shell produced by the present invention;

[0056] Figure 2 It is a schematic diagram of the assembly of the nozzle winding assembly and the forming tooling of the present invention;

[0057] Figure 3 yes Figure 2 A partial enlarged schematic diagram;

[0058] Figure 4 This is a schematic diagram of the location of the pre-curing vacuum bag for the lower section of the composite shell;

[0059] Figure 5 is a schematic diagram of the lower section of the composite shell after the forming tooling is removed;

[0060] Figure 6 It is a schematic diagram of the assembly of the support tooling and the lower section of the composite shell;

[0061] Figure 7 This is a schematic diagram of the location of the pre-curing vacuum bag in the upper section of the composite shell;

[0062] Figure 8 This is a schematic diagram of 0° prepreg cutting.

[0063] Numbers in the figure: 1-nozzle winding assembly; 11-throat liner; 12-diffuser section of the nozzle winding assembly; 2-lower section of the composite shell; 3-upper section of the composite shell; 4-molding tooling; 41-sleeve; 42-top plate; 43-bottom plate; 44-support rod; 45-positioning plate; 5-triangular area; 6-molding tooling layup surface and assembly surface with the nozzle winding assembly; 7-support tooling. DETAILED DESCRIPTION

[0064] The present invention is further described in detail below with reference to the examples. Of course, the scope of protection of the present invention is not limited to the following examples. Professionals and technicians in this field will understand that various changes and modifications can be made to the present invention without departing from the spirit of the present invention. The present invention provides a general and / or specific description of the materials and test methods used in the experiments. Although many materials and operating methods used to achieve the purpose of the present invention are well known in the art, the present invention is still described as detailed as possible here. The following examples further illustrate the present invention, rather than limit the present invention. Any equivalent transformation made in accordance with the concept of the present invention that is merely formal and not substantial should be regarded as the scope of the technical solution of the present invention.

[0065] Unless otherwise specified, the experimental methods or test methods described in the following examples are all conventional methods; the reagents and materials described are all obtained from conventional commercial channels or prepared by conventional methods unless otherwise specified.

[0066] like Figure 1-8 As shown, this embodiment provides a method for forming a fixed submersible all-composite engine nozzle composite shell, comprising the following steps:

[0067] S1. Forming of the nozzle winding assembly 1: assembling the throat liner 11 with the winding core mold, winding the inner ablation layer and the inner thermal insulation layer, curing, and machining the nozzle winding assembly 1 to the design required dimensions, and demoulding the nozzle winding assembly from the winding core mold.

[0068] Specifically, in step S1, the diffuser section 12 of the nozzle winding assembly has a plurality of grooves on the mating surface with the lower section of the composite shell, which can increase the contact area between the lower section of the composite shell and the diffuser section of the nozzle winding assembly; the upper and lower end faces of the composite shell and the junction of the diffuser section of the nozzle winding assembly are smoothly transitioned with the insulation layer to avoid the existence of a triangular area; the large end face of the diffuser section of the nozzle winding assembly is flattened to ensure that the large end face is parallel to the end face of the throat liner and perpendicular to the axial direction of the nozzle winding assembly, so as to facilitate accurate positioning of the composite shell molding tooling.

[0069] S2. Clean the surface of the molding tooling and stick the release cloth on the surface.

[0070] Specifically, in step S2, the surface of the forming tooling needs to be cleaned with lint-free paper and ethyl acetate, and then release cloth is applied to the diffuser section of the tooling and the nozzle winding assembly and the layup working surface.

[0071] S3, with the throat lining facing downwards, turn the nozzle winding assembly upside down and fix it on the forming tooling. Figure 2 and 3 shown.

[0072] Specifically, in step S3, the forming tool 4 includes a sleeve 41 and a top plate 42 arranged at the upper end of the sleeve 41 and a bottom plate 43 arranged at the lower end of the sleeve 41, a through hole is opened in the middle of the top plate 42 for the throat liner 11 to extend into the interior of the sleeve 41, and there is a gap between the throat liner 11 and the bottom plate 43; a support rod 44 is provided in the middle of the bottom plate 43 to pass through the through hole, and a positioning plate 45 is provided at the upper end of the support rod 44, and a clamping space for clamping the nozzle winding assembly diffusion section 12 is provided between the positioning plate 45 and the top plate 42; a triangular area 5 is formed between the nozzle winding assembly diffusion section 12 and the top plate 42, and the triangular area is machined and retained after the inner insulation layer is wound, so that the insulation layer is smoothly transitioned at the junction of the upper and lower end faces of the composite shell and the nozzle winding assembly diffusion section to avoid the existence of a triangular overhead area during the composite shell lamination process.

[0073] The nozzle winding assembly 1 is assembled with the forming tool 4, the positioning plate 45 is assembled, and the bolts above the positioning plate 45 are tightened. After assembly, the distance from the positioning plate to the forming tool 4 is measured evenly at 8 positions, and the height difference of each position is required to be less than 0.2mm.

[0074] S4. Prepreg laying and pre-pressing of the lower section 2 of the composite shell: The cut multi-layer prepreg is completely covered on the surface of the forming tooling and the diffusion section of the nozzle winding assembly according to the designed angle to form the lower section of the composite shell with a "7" shape in cross section, and vacuumed by a vacuum device, such as Figure 4 shown.

[0075] Specifically, S401, prepreg cutting, the prepreg used is carbon fiber reinforced epoxy resin prepreg; 1) 0° prepreg cutting, the lower section of the composite shell (flange position + contact position with the diffuser section of the nozzle winding assembly) is divided into 24 parts, each 15°, and the surface is unfolded in the 3D drawing software (10mm length is added at the upper and lower ends for machining allowance), and after the size is determined, it is cut by an automatic cutting machine; 2) +45° prepreg cutting, the contact position of the lower section of the composite shell and the diffuser section of the nozzle winding assembly is divided into 3 parts, each 120°, and the surface is unfolded in the 3D drawing software, and the lower end is extended by 10mm, and after the size is determined, it is cut by an automatic cutting machine; 3) -45° prepreg cutting size determination method is the same as 45° prepreg cutting, and the fiber direction of the cutting machine is opposite to 45°. 4) Cut +45° prepreg / -45° prepreg corresponding to the composite shell flange position. Plain carbon cloth prepreg is used for flange position cutting, and the corresponding epoxy resin is the same. Measure the root diameter of the composite shell flange and the end diameter of the composite shell on the CAD drawing to determine the dimensions of the composite shell flange position. Cut the pieces using an automatic cutting machine (inner diameter size -10mm, composite shell end diameter size +10mm, and add allowance after laying). 5) Cut 90° prepreg. Cut fiber strips with a width of 5mm and a length of 2000mm along the length direction of the unidirectional fabric fiber, with the length of 2000mm being the fiber length direction.

[0076] S402, placing the assembled winding assembly and forming tooling into an oven and preheating at 50°C for 1 hour;

[0077] S403, applying adhesive to the surfaces of the diffuser section of the nozzle winding assembly and the lower section of the composite shell;

[0078] S404, 0° prepreg layer 1, move the lower section of the composite shell corresponding to the nozzle winding assembly diffusion section position toward the large end by 10mm to mark the line, and mark the diameter of the flange position of the molding tool end face + 10mm) with the composite shell flange position and the diffusion section corner position as the starting point. After the starting point is fitted, push it toward the diffusion section large end and the flange end face position until it is completely fitted. After the first strip is completed, lay the second prepreg layer. The method is the same as the first strip. Repeat this step until the first layer of 24 0° prepreg strips are completely laid. Check whether there is overlap or gap between the strips, remove the overlapping position, and cut the corresponding shape to fill the gap position, such as Figure 8 shown.

[0079] S405, +45° prepreg layup, using the nozzle wrap assembly diffuser section mark as a reference for pasting, pasting +45° prepreg from the large end to the small end, to the composite shell flange position and the diffuser section corner position, cutting a triangular notch at the corner position to ensure that there is no gap or overlap at the corner position;

[0080] S406, Flange Position Laying 1: Starting from the flange position marked on the tooling, lay the prepreg layer at the flange position, pushing and compacting from the outside to the inside. Cut triangular notches at the corners to ensure that there are no gaps or overlaps at the corners.

[0081] S407, 0° prepreg layer 2, the laying method is the same as 0° prepreg layer 1;

[0082] S408, -45° prepreg layup, the layup method is the same as +45° prepreg layup;

[0083] S409, lay layer 2 at the flange position, in the same manner as S406, with the starting position offset by 45°;

[0084] S410, 90° prepreg layup, 2000mm long unidirectional fabric spirally wound to fix the diffuser section position;

[0085] S411, lay layer 3 at the flange position, in the same manner as S406, with the starting position offset by 90;

[0086] S412, vacuum pre-pressing, using a vacuum device to perform vacuum treatment, placing the entire body in an oven at 50°C while heating and vacuuming for 2 to 3 hours;

[0087] S413, Laying: 1) -45° prepreg laying, same as S408; 2) Flange position laying, same as S409, with the starting point offset 45° from S411; 3) 0° prepreg laying, same as S407; 5) +45° prepreg laying, same as S405; 6) Flange position laying, same as S406, with the starting point offset 90° from S411; 7) 0° prepreg laying, same as S404;

[0088] S414, vacuum pre-pressing, using a vacuum device to perform vacuum treatment, placing the entire body in an oven at 50°C while heating and vacuuming for 2 to 3 hours;

[0089] S415. Repeat the two sets of ply pre-pressing processes until the shell thickness meets the design requirements and has a margin of more than 2 mm.

[0090] S5. Pre-curing molding: The lower section of the composite shell equipped with a vacuum device is transferred into the autoclave together with the molding tool, and the lower section of the composite shell is cured at the designed temperature and pressure, and vacuumed at the same time.

[0091] Specifically, in step S5, the pre-curing conditions are: room temperature → 50±5°C / 2h → 95±5°C / 6h → 50±5°C, the pressure in the autoclave is 0.1±0.02MPa → 2.8±0.2MPa / 11.5h → 0.1±0.02MPa, the pressure during the heating and insulation process is 2.8±0.2MPa, the heating rate is 0.2°C / min, the pressure rising rate is 0.05MPa / min, the cooling rate is 0.1°C / min, and the pressure reducing rate is 0.025MPa / min.

[0092] S6. Demolding and surface treatment: Clean the edges of the lower section of the composite shell and the molding tooling that affect demolding, separate the molding tooling from the lower section of the composite shell, and after separation, roughen the surface of the lower section of the composite shell and clean the dust generated during the roughening process.

[0093] Specifically, in step S6, demoulding is performed, the positioning plate is removed, the lower section 2 of the composite shell and the forming tooling 4 are dismantled, and the anti-deformation supporting tooling 7 is installed. Figure 5-7 The support tooling 7 is wrapped with breathable felt on all sides to prevent the tip of the support tooling from piercing the vacuum bag due to excessive pressure during the support curing process, causing vacuum failure.

[0094] S7. Prepreg Laying and Prepressing of the Composite Shell Upper Section 3: The cut multi-layer prepreg is completely covered at the designed angle on the end face of the cured composite shell lower section and the position of the composite shell upper section corresponding to the diffuser section of the nozzle winding assembly to form an L-shaped composite shell upper section, and vacuumed using a vacuum device;

[0095] Specifically, in step S7, the prepreg layering and pre-pressing of the upper section of the composite shell are specifically as follows:

[0096] S71, prepreg blanking, blanking method is the same as S401;

[0097] S72. Apply adhesive to the surfaces of the diffuser section of the nozzle wrap assembly and the upper section of the composite shell;

[0098] S73, laying, the laying method is the same as S404-S411;

[0099] S74, vacuum pre-pressing, using a vacuum device to perform vacuum treatment, placing the entire unit in an oven at 50°C while heating and vacuuming for 2 to 3 hours;

[0100] S75, laying, the laying method is the same as S413;

[0101] S76, vacuum pre-pressing, using a vacuum device to perform vacuum treatment, placing the whole in an oven at 50°C while heating and vacuuming for 2 to 3 hours;

[0102] S77. Repeat the two-group pre-pressing process until the shell thickness meets the design requirements and has a margin of more than 2 mm.

[0103] S8. Curing and molding: The upper section of the composite shell equipped with a vacuum pumping device is transferred into an autoclave, and the upper section of the composite shell is cured at a designed temperature and pressure, and vacuumed at the same time to obtain a composite shell.

[0104] Specifically, in step S8, the curing molding conditions are: room temperature → 80±5℃ / 2h → 120±5℃ / 2h →

[0105] 135±5℃ / 2h→160±5℃ / 4h→60±5℃, when heating starts, add initial pressure of 1MPa; from 50℃, the full pressure is 2.8MPa, and the pressure is naturally reduced after the 160℃ insulation is completed; the heating rate is 0.2℃ / min, the pressure rising rate is 0.05MPa / min, the cooling rate is 0.1℃ / min, and the pressure reducing rate is 0.025MPa / min.

[0106] S9, machining: Machining the composite shell to make the size of the composite shell meet the design requirements.

[0107] In addition, it should be noted that the vacuum pumping device used in the present invention can be any commonly used device in the field, and the present invention will not elaborate on it.

[0108] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for forming a fixed submersible all-composite engine nozzle composite shell, characterized in that: include: S1. Forming of nozzle winding assembly; S2. Clean the surface of the molding tooling and stick a release cloth on the surface; S3. With the throat lining facing downward, turn the nozzle winding assembly upside down and fix it on the forming tooling; S4. Prepreg Laying and Prepressing of the Composite Shell Lower Section: The prepreg layers are cut and completely covered on the surface of the forming tooling and the diffuser section of the nozzle winding assembly according to the designed angle to form the composite shell lower section with a "7" cross-section. A vacuum device is then used to evacuate the prepreg. S5. Pre-curing molding: The lower section of the composite shell equipped with a vacuum device is transferred into the autoclave together with the molding tool, and the lower section of the composite shell is cured at the designed temperature and pressure, and vacuumed at the same time; S6, demoulding and surface treatment: cleaning the edges of the lower section of the composite shell and the molding tool that affect demoulding, separating the molding tool from the lower section of the composite shell, and cleaning the surface of the lower section of the composite shell after separation; S7. Prepreg Laying and Prepressing of the Composite Shell Upper Section: The cut multi-layer prepreg is completely covered at the designed angle on the end face of the cured composite shell lower section and the position of the composite shell upper section corresponding to the diffuser section of the nozzle winding assembly to form an L-shaped composite shell upper section, and vacuumed using a vacuum device; S8, curing and molding: transferring the upper section of the composite shell equipped with a vacuum pumping device into an autoclave, curing the upper section of the composite shell at a designed temperature and pressure, and simultaneously performing vacuum pumping to obtain a composite shell; S9, machining: machining the composite shell to make the size of the composite shell meet the design requirements; In step S3, the forming tooling includes a sleeve and a top plate arranged at the upper end of the sleeve and a bottom plate arranged at the lower end of the sleeve, a through hole is opened in the middle of the top plate for the throat liner to extend into the interior of the sleeve, and there is a gap between the throat liner and the bottom plate; a support rod passing through the through hole is provided in the middle of the bottom plate, a positioning plate is provided at the upper end of the support rod, and a clamping space for clamping the diffusion section of the nozzle winding assembly is provided between the positioning plate and the top plate.

2. The method for forming a fixed submersible all-composite engine nozzle composite shell according to claim 1, characterized in that: In step S1, a plurality of grooves are provided on the mating surface between the diffusion section of the nozzle winding assembly and the lower section of the composite shell; a smooth transition of the heat insulation layer is performed at the junction of the upper and lower end surfaces of the composite shell and the diffusion section of the nozzle winding assembly to avoid the existence of a triangular area; and the large end face of the diffusion section of the nozzle winding assembly is flattened to ensure that the large end face is parallel to the end face of the throat liner and perpendicular to the axial direction of the nozzle winding assembly.

3. The method for forming a fixed submersible all-composite engine nozzle composite shell according to claim 1, characterized in that: In step S2, the surface of the forming tooling is cleaned with lint-free paper and ethyl acetate, and then release cloth is applied to the forming tooling, the diffuser section of the nozzle winding assembly, and the lamination working surface.

4. The method for forming a fixed submersible all-composite engine nozzle composite shell according to claim 1, characterized in that: In step S5, the prepreg layering and pre-pressing steps of the lower section of the composite shell specifically include: S401, prepreg cutting, according to the cutting design requirements, cutting into 0° prepreg, +45° prepreg, -45° prepreg, and 90° prepreg; S402, placing the assembled nozzle winding assembly and the forming tooling into an oven and preheating at 50°C for 1 hour; S403, applying adhesive to the mating surfaces of the diffuser section of the nozzle winding assembly and the lower section of the composite shell; S404, 0° prepreg layer 1, move the lower section of the composite shell corresponding to the diffuser section of the nozzle winding assembly 10mm toward the large end and mark it. Mark the diameter of the flange position of the molding tool end face + 10mm. Use the composite shell flange position and the corner position of the diffuser section of the nozzle winding assembly as the starting point. After the starting point is aligned, push it towards the large end of the diffuser section and the flange end face position until it is fully aligned. After the first line is completed, repeat this step to lay the next prepreg layer until the 0° prepreg is completely laid; S405, +45° prepreg layup, using the nozzle wrap assembly diffuser section mark as a reference for pasting, pasting +45° prepreg from the large end to the small end, to the composite shell flange position and the diffuser section corner position, cutting a triangular notch at the corner position to ensure that there is no gap or overlap at the corner position; S406, Flange Position Laying 1: Starting from the flange position marked on the tooling, lay the prepreg at the flange position, pushing and compacting from the outside to the inside. Cut triangular notches at the corners to ensure that there are no gaps or overlaps at the corners. S407, 0° prepreg layer 2, the laying method is the same as S404 0° prepreg layer 1; S408, -45° prepreg layup, the layup method is the same as S405 +45° prepreg layup; S409, lay layer 2 at the flange position, in the same manner as S406, with the starting position offset by 45°; S410, 90° prepreg layup, unidirectional fabric spirally wound to fix the diffuser section position of the nozzle winding assembly; S411, lay layer 3 at the flange position, in the same manner as S406, with the starting position offset by 90°; S412, vacuum pre-pressing, using a vacuum device to perform vacuum treatment, placing the entire body in an oven at 50°C while heating and vacuuming for 2 to 3 hours; S413, Laying: 1) -45° prepreg laying, same as S408; 2) Flange position laying, same as S409, with the starting point offset 45° from S411; 3) 0° prepreg laying, same as S407; 5) +45° prepreg laying, same as S405; 6) Flange position laying, same as S406, with the starting point offset 90° from S411; 7) 0° prepreg laying, same as S404; S414, vacuum pre-pressing, using a vacuum device to perform vacuum treatment, placing the entire body in an oven at 50°C while heating and vacuuming for 2 to 3 hours; S415. Repeat the two sets of ply pre-pressing processes until the shell thickness meets the design requirements and has a margin of more than 2 mm.

5. The method for forming a fixed submersible all-composite engine nozzle composite shell according to claim 4, characterized in that: In step S401, the prepreg is cut into pieces in the following manner: Cut the 0° prepreg into 24 equal parts around the lower section of the composite shell, each with a 15° angle. Surface development is performed using 3D graphics software. After the dimensions are determined, the pieces are cut using an automatic cutting machine. Cut the +45° prepreg material and divide the contact area between the lower section of the composite shell and the diffuser section of the nozzle winding assembly into three equal parts, each with an angle of 120°. Surface unfolding is performed using 3D drawing software, and the lower end is extended by 10mm. After the size is determined, the pieces are cut using an automatic cutting machine. -45° prepreg blanking size determination method is the same as 45° prepreg blanking, the fiber direction of the cutting machine is opposite to 45°; Cut the +45° prepreg / -45° prepreg at the corresponding position of the composite shell flange. Measure the root diameter and end face diameter of the composite shell flange in the CAD drawing to determine the position and size of the composite shell flange, and then cut the composite shell flange on the automatic cutting machine. 90° prepreg is cut into fiber strips with a width of 5mm and a length of 2000mm along the length direction of the unidirectional fabric fiber, with the length of 2000mm being the fiber length direction.

6. The method for forming a fixed submersible all-composite engine nozzle composite shell according to claim 1, characterized in that: In step S5, the pre-curing conditions are: room temperature → 50±5°C / 2h → 95±5°C / 6h → 50±5°C, the pressure in the autoclave is 0.1±0.02MPa → 2.8±0.2MPa / 11.5h→0.1±0.02MPa, the pressure during heating and keeping is 2.8±0.2MPa, the heating rate is 0.2℃ / min, the pressure rising rate is 0.05MPa / min, the cooling rate is 0.1℃ / min, and the pressure reducing rate is 0.025MPa / min.

7. The method for forming a fixed submersible all-composite engine nozzle composite shell according to claim 1, characterized in that: In step S7, the prepreg layering and pre-pressing steps of the upper section of the composite shell specifically include: S71, prepreg blanking, blanking method is the same as S401; S72. Apply adhesive to the surfaces of the diffuser section of the nozzle wrap assembly and the upper section of the composite shell; S73, laying, the laying method is the same as S404-S411; S74, vacuum pre-pressing, using a vacuum device to perform vacuum treatment, placing the entire unit in an oven at 50°C while heating and vacuuming for 2 to 3 hours; S75, laying, the laying method is the same as S413; S76, vacuum pre-pressing, using a vacuum device to perform vacuum treatment, placing the whole in an oven at 50°C while heating and vacuuming for 2 to 3 hours; S77. Repeat the two sets of ply pre-pressing process until the shell thickness meets the design requirements and has a margin of more than 2mm.

8. The method for forming a fixed submersible all-composite engine nozzle composite shell according to claim 4 or 7, characterized in that: The prepreg is a carbon fiber reinforced epoxy resin prepreg.

9. The method for forming a fixed submersible all-composite engine nozzle composite shell according to claim 1, characterized in that: In step S8, the curing molding conditions are: room temperature → 80±5℃ / 2h → 120±5℃ / 2h → 135±5℃ / 2h → 160±5℃ / 4h → 60±5℃, when the temperature starts to rise, an initial pressure of 1MPa is added; the full pressure is 2.8MPa starting at 50℃, and the pressure is naturally reduced after the insulation at 160℃ is completed; the heating rate is 0.2℃ / min, the pressure rising rate is 0.05MPa / min, the cooling rate is 0.1℃ / min, and the pressure reducing rate is 0.025MPa / min.

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