A method for preparing an integrated composite nozzle load-bearing shell

Abstract

The invention discloses an integrated preparation method of a composite material nozzle bearing shell, which belongs to the technical field of solid rocket engines; the method comprises: step 1, pre-embedding a throat liner on a winding mold, winding preparation of an ablation layer on the outside of the throat liner and the winding mold, and winding preparation of a heat insulation layer on the outside of the ablation layer; autoclaving the prepared ablation layer and heat insulation layer to form a nozzle body; step 2, machining the outer surface of the heat insulation layer, and providing a plurality of annular grooves on the heat insulation layer along the axial direction of the heat insulation layer; step 3, using carbon fiber to perform in-situ weaving preparation of a three-dimensional preform of a nozzle bearing shell on the outer surface of the machined heat insulation layer to obtain a preliminarily formed nozzle bearing shell; step 4, assembling an RTM mold, and heating and curing, removing the RTM mold after curing to obtain an integrated nozzle bearing shell. The production cycle can be effectively shortened and the specific strength and specific modulus of the nozzle bearing shell can be improved.

Description

Technical Field

[0001] The invention relates to a method for integrated preparation of a composite material nozzle load-bearing shell, and belongs to the technical field of solid rocket engines. Background Art

[0002] The composite nozzle is an important energy conversion component of the solid rocket engine. It ejects the high-temperature and high-pressure airflow generated by the combustion of fuel in the engine at a certain expansion ratio. The generated reverse thrust is transmitted to the rocket engine shell through the nozzle load-bearing shell, thereby providing sufficient power for the rocket as a whole to fly into space. As a key structure in the energy transfer link of the solid rocket engine, the composite nozzle load-bearing shell must have high rigidity and strength to ensure stability and reliability at ultra-high pressure and ultra-high moving speed.

[0003] At present, composite nozzle bearing shells are mainly made of metal materials, including high-strength manganese steel, titanium alloy, high-strength aluminum alloy and other materials. The above materials need to go through forging blanks, repeated aging treatment and high-precision machining in the process of making nozzle bearing shells, and the production cycle takes 1 to 2 months or even longer; at the same time, the specific strength and specific modulus of metal materials are several times lower than those of fiber-reinforced composite materials. The higher the proportion of metal materials used in aerospace structural parts, the higher the overall weight of the spacecraft will be; in addition, after the preparation of the metal nozzle bearing shell, it needs to be bonded and assembled with the composite nozzle body through adhesives, and the process is complicated and difficult to implement. Therefore, the long production cycle, low specific strength, specific modulus and complex process of the metal nozzle bearing shell can no longer adapt to the current faster and lighter aerospace development concept. Summary of the invention

[0004] The present invention designs and develops an integrated preparation method for a composite material nozzle load-bearing shell, which can effectively shorten the production cycle and improve production efficiency, while also improving the specific strength and specific modulus of the nozzle load-bearing shell, achieving lightweight products, and can simplify the process, reduce operational difficulty, and more easily ensure quality requirements.

[0005] The technical solution provided by the present invention is:

[0006] A composite material nozzle load-bearing shell integrated preparation method, comprising:

[0007] Step 1: pre-embed the throat liner in the winding mold, prepare the ablation layer by winding outside the throat liner and the winding mold, and prepare the heat insulation layer by winding outside the ablation layer; autoclave-cure the prepared ablation layer and the heat insulation layer to form the nozzle body;

[0008] Step 2: machining the outer surface of the heat insulation layer, and providing a plurality of annular grooves on the heat insulation layer at intervals along the axial direction of the heat insulation layer;

[0009] Step 3: Using carbon fiber to in-situ weave a three-dimensional preform of a nozzle bearing shell on the outer surface of the machined heat insulation layer to obtain a preliminarily formed nozzle bearing shell;

[0010] Step 4: Assemble the RTM mold. Assemble the RTM mold on the initially formed nozzle load-bearing shell and connect the glue injection mechanism. After the connection is completed, inject RTM epoxy resin through the glue injection mechanism and heat and cure it. After the curing is completed, remove the RTM mold and the glue injection mechanism to obtain an integrated nozzle load-bearing shell.

[0011] Preferably,

[0012] The winding mold in step 1 comprises: a core mold head section and a core mold tail section which are fixedly connected;

[0013] The ablation layer is prepared by a flat-fold winding process using a carbon cloth / phenolic prepreg tape;

[0014] The heat insulation layer is made of high-silica cloth / phenolic pre-impregnated cloth tape by a flat-fold winding process;

[0015] During the winding process of the thermal insulation layer, a processing allowance of 3 to 5 mm needs to be reserved for the outer surface.

[0016] Preferably, the outer profile surface of the thermal insulation layer is the interface where the thermal insulation layer cooperates with the nozzle load-bearing shell.

[0017] Preferably, the dimensions of the annular groove are: 2 mm deep, 4 mm wide; and the interval between adjacent annular grooves is 50 mm.

[0018] Preferably, in step three, the carbon fiber is of T700 grade.

[0019] Preferably, the RTM mold is a two-petal annular splicing, and is provided with multiple resin injection ports and resin outlets;

[0020] The glue injection mechanism comprises:

[0021] A resin injection port valve, which is connected and arranged on the resin injection port;

[0022] A resin outlet valve, which is connected and arranged on the resin outlet;

[0023] Glue cleaning tank, which is used to hold RTM epoxy resin;

[0024] A glue injection pump, which is connected and arranged between the glue cleaning tank and the resin injection port valve through a first connecting pipeline;

[0025] A vacuum pump, one end of which is connected to the resin outlet valve via a second connecting pipeline;

[0026] The resin collecting tank is used to collect the RTM epoxy resin flowing out through the vacuum pump and the second connecting pipeline.

[0027] Preferably, in the step 4, after the glue injection mechanism is connected, the entire preparation system is formed, and the airtightness test of the entire preparation system is performed, including:

[0028] The preparation system was evacuated. When the vacuum degree reached -100 KPa, the system was evacuated for 10 min. The vacuum pump was turned off and the change of vacuum degree was observed. If the vacuum degree decreased by ≤1 KPa within 5 min, the system was considered to be airtight.

[0029] Preferably,

[0030] After the air tightness test is qualified, turn on the vacuum pump, and continue to evacuate for 20 minutes when the vacuum degree reaches -100KPa, open the resin injection port valve, and inject the resin. After the resin flows out of the resin outlet, continue to inject the resin for 30 seconds, close the resin outlet valve, and continue to maintain the pressure for 20 minutes, then close the resin injection port valve to complete the resin injection;

[0031] Remove the pipeline, put the RTM mold and nozzle body into the curing furnace, and cure the nozzle load-bearing shell after glue injection at 80°C for 4 hours. After the curing is completed, wait for the RTM mold to cool to room temperature before taking out the mold to complete the preparation of the nozzle load-bearing shell.

[0032] Preferably, the assembly gap between the throat liner and the winding core mold is required to be ≤0.1mm and evenly distributed around the circumference, with a coaxiality of ≤φ0.2mm.

[0033] Preferably, the RTM epoxy resin is a low temperature curing epoxy resin.

[0034] The beneficial effects of the present invention are:

[0035] 1. Compared with the traditional throat liner bonding and press-fitting process, the throat liner pre-embedded method proposed in the present invention does not need to use additional adhesive to bond the throat liner to the nozzle body. The throat liner is co-cured with the ablation layer and the heat insulation layer to directly form the nozzle body, which improves the reliability and ablation resistance of the throat liner. At the same time, the bonding process is eliminated and the process flow is simplified.

[0036] 2. The ablative layer and thermal insulation layer autoclave co-curing process proposed in the present invention reduces the number of curing times, avoids multiple high-temperature damages to the component structures, improves production efficiency, and saves energy and equipment costs.

[0037] 3. The in-situ weaving method of the three-dimensional preform of the nozzle load-bearing shell proposed in the present invention can achieve the minimum inner diameter of the nozzle load-bearing shell being smaller than the maximum outer diameter of the throat liner, thereby improving the supporting effect of the nozzle load-bearing shell on the throat liner and ensuring the overall reliability of the composite nozzle.

[0038] 4. The present invention adopts carbon fiber as the reinforcing material of the nozzle bearing shell, and utilizes the advantages that the specific strength and specific modulus of resin-based carbon fiber reinforced composite materials are several times higher than those of metal materials. While improving the mechanical properties of the nozzle bearing shell, it can also achieve lightweight composite nozzle products, greatly reducing the overall cost of solid rocket launches.

[0039] 5. The in-situ integrated RTM process proposed in the present invention for preparing the nozzle load-bearing shell greatly simplifies the process flow, reduces the difficulty of operation, and makes it easier to meet the overall quality requirements of the nozzle compared to the traditional metal material nozzle load-bearing shell bonding process.

[0040] 6. The present invention proposes to process an annular groove at the interface between the nozzle insulation layer and the nozzle load-bearing shell, and to weave the reinforcing material carbon fiber into the annular groove during the weaving process of the three-dimensional preform of the nozzle load-bearing shell, so as to tightly connect the nozzle load-bearing shell and the insulation layer together and improve the reliability of the nozzle structure.

[0041] 7. The two-petal annular splicing RTM mold proposed in the present invention includes multiple resin injection ports and resin outlets, which can ensure that the mold cavity is fully filled after the resin is injected, improve the degree of integration between the resin and the three-dimensional woven preform, avoid defects inside the product, and ensure the reliability of the nozzle load-bearing shell.

[0042] 8. The present invention adds an airtightness detection step before RTM epoxy resin injection. The airtightness detection can effectively avoid leakage during the resin injection process and improve the stability and safety of the entire system.

[0043] 9. The present invention adopts low-temperature curing RTM epoxy resin, and the curing process is more energy-saving and environmentally friendly. The low-temperature curing of the load-bearing shell avoids the nozzle body from experiencing high-temperature damage multiple times, thereby ensuring the reliability of other components of the composite nozzle. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a schematic diagram of the structure of the nozzle load-bearing shell after preparation described in the present invention.

[0045] Figure 2 It is a schematic diagram of the structure of the three-dimensional braided preform of the nozzle load-bearing shell after preparation according to the present invention.

[0046] Figure 3 This is a schematic diagram of the assembly structure of the RTM mold for the integrated nozzle bearing shell of the present invention. DETAILED DESCRIPTION

[0047] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0048] like Figure 1-3 As shown, the present invention provides an integrated preparation method for a composite nozzle bearing shell, wherein the throat liner is co-cured with the ablation layer and the heat insulation layer to directly form a nozzle body, and the nozzle bearing shell is prepared based on the RTM process, which can effectively shorten the production cycle and improve the production efficiency, while improving the specific strength and specific modulus of the nozzle bearing shell, and realizing lightweight products. In addition, the three-dimensional preform in-situ weaving process is adopted to simplify the process, reduce the difficulty of operation, and more easily ensure the quality requirements, including:

[0049] Step 1: pre-embed the throat liner 110 in the winding mold, prepare the ablation layer 140 by winding outside the throat liner 110 and the winding mold, and prepare the heat insulation layer 150 by winding outside the ablation layer 140; autoclave the prepared ablation layer 140 and the heat insulation layer 150 to form a nozzle body;

[0050] Step 2: machining the outer surface of the heat insulation layer 150, and providing a plurality of annular grooves on the heat insulation layer along the axial direction of the heat insulation layer 150;

[0051] Step 3: Using carbon fiber to in-situ weave a three-dimensional preform of the nozzle bearing shell on the outer surface of the machined heat insulation layer 150 to obtain a preliminarily formed nozzle bearing shell;

[0052] Step 4: Assemble the RTM mold. Assemble the RTM mold on the initially formed nozzle load-bearing shell and connect the glue injection mechanism. After the connection is completed, inject RTM epoxy resin through the glue injection mechanism and heat and cure it. After the curing is completed, remove the RTM mold to obtain an integrated nozzle load-bearing shell.

[0053] In the present invention, as a preference, the winding mold includes: a core mold head section 120 and a core mold tail section 130 that are fixedly connected. The core mold head section 120 and the core mold tail section 130 are positioned by pins and fastened by screws to completely fix the throat liner 110.

[0054] During the process of pre-embedding the throat liner 110 into the winding mold, it is necessary to monitor the assembly gap and coaxiality between the throat liner 110 and the winding mold in real time. In the present invention, as a preferred embodiment, the assembly gap is required to be ≤0.1mm and evenly distributed around the circumference, and the coaxiality is ≤φ0.2mm.

[0055] In the present invention, as a preference, the ablation layer 140 is prepared by a flat-fold winding process using carbon cloth / phenolic prepreg tape, and the thermal insulation layer 150 is prepared by a flat-fold winding process using high-silica cloth / phenolic tape, and the curing method used for the ablation layer 140 and the thermal insulation layer 150 is autoclave co-curing.

[0056] During the winding process of the heat insulation layer 150, a processing allowance of 3 to 5 mm is required for the outer surface to ensure that the interface with the nozzle bearing shell 180 can be processed later. Among them, the outer surface of the heat insulation layer 150 is the interface between the heat insulation layer 150 and the nozzle bearing shell 180.

[0057] In the present invention, as a preference, the size of the annular groove in step 2 is: 2~5mm deep, 4~10mm wide, and the annular grooves are distributed every 50~80mm along the generatrix direction of the conical surface of the outer surface of the insulation layer 150, that is, the interval between adjacent annular grooves is 50~80mm.

[0058] In the present invention, as a preferred embodiment, the carbon fiber in step three is T700 grade carbon fiber, and the three-dimensional preform 160 is prepared by in-situ weaving.

[0059] The in-situ weaving method refers to weaving the three-dimensional preform 160 directly based on the outer surface of the insulation layer 150. During the weaving process, the carbon fiber is woven into the annular groove, and the nozzle load-bearing shell three-dimensional preform 160 and the insulation layer 150 are tightly connected together.

[0060] The RTM mold 170 in step 4 is in the form of two-petal annular splicing, including multiple resin injection ports 190 and resin outlets 200 .

[0061] The glue injection mechanism includes: a glue cleaning tank, a glue injection pump, a resin injection port valve, a resin outlet valve, a vacuum pump, a glue collection tank, and connecting pipelines.

[0062] The resin injection port valve and the resin outlet valve correspond to the resin injection port 190 and the resin outlet 200 respectively. The clear glue tank is used to hold the RTM epoxy resin to be injected. The glue injection pump is connected and arranged between the clear glue tank and the resin injection port valve through a first connecting pipeline; one end of the vacuum pump is connected to the resin outlet valve through a second connecting pipeline, and the glue collecting tank is used to collect the RTM epoxy resin flowing out through the vacuum pump and the second connecting pipeline.

[0063] During operation, the RTM epoxy resin in the clear glue tank is extracted and pressurized by the glue injection pump, and flows into the mold cavity of the nozzle load-bearing shell RTM mold through the resin injection port through the first connecting pipeline and the resin injection port valve. When the RTM epoxy resin fills the mold cavity of the nozzle load-bearing shell RTM mold, the RTM epoxy resin flows out through the resin outlet, passes through the resin outlet valve through the second connecting pipeline, and is finally extracted by the vacuum pump into the glue collection tank.

[0064] In the present invention, preferably, the RTM resin is a low temperature curing epoxy resin.

[0065] After the RTM mold is assembled, an airtightness test is required. Turn on the vacuum pump to evacuate the mold. After the vacuum degree reaches -100KPa, continue to evacuate the mold for 10 minutes. Then turn off the vacuum pump and observe the change in vacuum degree. If the vacuum degree decreases by ≤1KPa within 5 minutes, the system is considered to be airtight.

[0066] When the air tightness is qualified, the system starts to prepare to inject RTM epoxy resin. Before injection, vacuuming is required. After the vacuum degree reaches -100KPa, continue to maintain vacuuming for 20 minutes, then open the resin injection port 190 valve, and start resin injection. After resin flows out of all the resin outlets 200, continue to inject resin for 30 seconds and then close the resin outlet 200 valve. Continue to maintain pressure for 20 minutes and then close the resin injection port 190 valve to complete the resin injection.

[0067] Keep the valves of the resin injection port 190 and the resin outlet 200 in the closed state, remove the pipeline, put the assembly of the RTM mold and the nozzle body into the curing furnace, and cure the nozzle load-bearing shell 180 after injection. The curing temperature system is 80°C and kept warm for 4 hours. After the curing is completed, wait for the RTM mold to cool to room temperature and then take out the mold to complete the preparation, and obtain the finished product of the integrated composite nozzle load-bearing shell.

[0068] In the present invention, as a preferred embodiment, when the RTM mold is removed, the connecting screws on both sides of the mold are first removed, and then the two halves of the mold are respectively removed from the nozzle body in the horizontal direction. After the mold is removed, the preparation of the nozzle load-bearing shell 180 is completed.

[0069] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A composite material nozzle load-bearing shell integrated preparation method, characterized in that: include: Step 1: pre-embed the throat liner in the winding mold, prepare the ablation layer by winding outside the throat liner and the winding mold, and prepare the heat insulation layer by winding outside the ablation layer; autoclave-cure the prepared ablation layer and the heat insulation layer to form the nozzle body; Step 2: machining the outer surface of the heat insulation layer, and providing a plurality of annular grooves on the heat insulation layer at intervals along the axial direction of the heat insulation layer; Step 3: Using carbon fiber to in-situ weave a three-dimensional preform of a nozzle bearing shell on the outer surface of the machined heat insulation layer to obtain a preliminarily formed nozzle bearing shell; Among them, the in-situ weaving method refers to weaving a three-dimensional preform directly based on the outer surface of the thermal insulation layer, and the carbon fibers are woven into the annular groove during the weaving process; Step 4: assemble the RTM mold. Assemble the RTM mold on the initially formed nozzle load-bearing shell and connect the glue injection mechanism. After the connection is completed, inject RTM epoxy resin through the glue injection mechanism and heat and cure it. After the curing is completed, remove the RTM mold and the glue injection mechanism to obtain an integrated nozzle load-bearing shell. The RTM mold is a two-petal annular splicing, and is provided with multiple resin injection ports and resin outlets.

2. The method for integrated preparation of a composite nozzle bearing shell according to claim 1, characterized in that: The winding mold in step 1 comprises: a core mold head section and a core mold tail section which are fixedly connected; The ablation layer is prepared by a flat-fold winding process using a carbon cloth / phenolic prepreg tape; The heat insulation layer is made of high-silica cloth / phenolic pre-impregnated cloth tape by a flat-fold winding process; During the winding process of the thermal insulation layer, a processing allowance of 3 to 5 mm needs to be reserved for the outer surface.

3. The method for integrated preparation of a composite nozzle bearing shell according to claim 2, characterized in that: The outer profile surface of the heat insulation layer is the interface where the heat insulation layer cooperates with the nozzle load-bearing shell.

4. The method for integrated preparation of a composite nozzle bearing shell according to claim 3, characterized in that: The dimensions of the annular groove are: 2 mm deep, 4 mm wide; the interval between adjacent annular grooves is 50 mm.

5. The method for integrated preparation of a composite nozzle bearing shell according to claim 4, characterized in that: In the step three, the carbon fiber is of T700 grade.

6. The method for integrated preparation of a composite nozzle bearing shell according to claim 4, characterized in that: The glue injection mechanism comprises: A resin injection port valve, which is connected and arranged on the resin injection port; A resin outlet valve, which is connected and arranged on the resin outlet; Glue cleaning tank, which is used to hold RTM epoxy resin; A glue injection pump, which is connected and arranged between the glue cleaning tank and the resin injection port valve through a first connecting pipeline; A vacuum pump, one end of which is connected to the resin outlet valve via a second connecting pipeline; The resin collecting tank is used to collect the RTM epoxy resin flowing out through the vacuum pump and the second connecting pipeline.

7. The method for integrated preparation of a composite nozzle bearing shell according to claim 1 or 6, characterized in that: In the step 4, after the glue injection mechanism is connected, the entire preparation system is formed, and the airtightness test of the entire preparation system is performed, including: The preparation system was evacuated. When the vacuum degree reached -100 KPa, the system was evacuated for 10 min. The vacuum pump was turned off and the change of vacuum degree was observed. If the vacuum degree decreased by ≤1 KPa within 5 min, the system was considered to be airtight.

8. The method for integrated preparation of a composite nozzle bearing shell according to claim 7, characterized in that: After the air tightness test is qualified, turn on the vacuum pump, and continue to evacuate for 20 minutes when the vacuum degree reaches -100KPa, open the resin injection port valve, and inject the resin. After the resin flows out of the resin outlet, continue to inject the resin for 30 seconds, close the resin outlet valve, and continue to maintain the pressure for 20 minutes, then close the resin injection port valve to complete the resin injection; Remove the pipeline, put the RTM mold and nozzle body into the curing furnace, and cure the nozzle load-bearing shell after glue injection at 80°C for 4 hours. After the curing is completed, wait for the RTM mold to cool to room temperature before taking out the mold to complete the preparation of the nozzle load-bearing shell.

9. The method for integrated preparation of a composite nozzle bearing shell according to claim 8, characterized in that: The assembly gap between the throat liner and the winding core mold is required to be ≤0.1mm and evenly distributed around the circumference, with a coaxiality of ≤φ0.2mm.

10. The method for integrated preparation of a composite nozzle bearing shell according to claim 9, characterized in that: The RTM epoxy resin is a low temperature curing epoxy resin.

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