A coaxial 3D printing method for improving the burning rate of solid propellant and the propellant

Abstract

The application relates to the technical field of solid propellant 3D printing, and particularly discloses a coaxial 3D printing method for improving the burning rate of a solid propellant and the propellant, which comprises the following steps: forming linear materials with an inner core of a heat-conducting composite material and an outer shell of a solid propellant material based on a coaxial 3D printer, and printing the linear materials layer by layer to obtain the propellant; the method can realize accurate regulation and control of the burning rate and energy performance of the finally formed propellant; meanwhile, the method of embedding the heat-conducting composite material can greatly improve the axial burning rate of the solid propellant in the form of increasing physical heat conduction.

Description

Technical Field

[0001] This invention relates to the field of solid propellant 3D printing technology, specifically to a coaxial 3D printing method and propellant for improving the burning rate of solid propellants. Background Technology

[0002] High-burning-rate solid propellants can generate large thrust in a short time, which is one of the main development directions of solid propellants and is of great significance to the development of tactical weapons, strategic missiles and aerospace technology.

[0003] Currently used mature propellant systems have limited ranges for adjusting burning rate. Adding functional additives or altering the chemical composition often affects the overall performance of the propellant, requiring re-optimization of the formulation. To increase burning rate without affecting propellant composition, physical methods such as embedding thermally conductive materials like metal wires or graphite fibers can be used. These materials rapidly transfer the high temperature from the burning surface of the propellant to the unburned components, accelerating the combustion process. However, the traditional method of embedding metal wires or graphite fibers in the final stage of the casting process is not only complex but also difficult to achieve with complex propellant configurations. Summary of the Invention

[0004] To address the aforementioned problems, the first objective of this invention is to provide a coaxial 3D printing method for improving the burning rate of solid propellants, enabling precise control over the burning rate and energy performance of the final propellant. Simultaneously, the method of embedding thermally conductive composite materials can significantly increase the axial burning rate of solid propellants by increasing physical thermal conductivity.

[0005] A second objective of this invention is to provide a propellant produced using a coaxial 3D printing method.

[0006] The first technical solution adopted in this invention is: a coaxial 3D printing method for improving the burning rate of solid propellants, comprising forming a linear material with a thermally conductive composite material core and a solid propellant material on a coaxial 3D printer, and printing the linear material layer by layer to obtain propellant.

[0007] Preferably, the coaxial 3D printing method for improving the burning rate of solid propellants includes the following steps:

[0008] S1. Prepare thermally conductive composite materials and solid propellant materials respectively;

[0009] S2. The thermally conductive composite material is loaded into the printing cylinder of the inner core layer of the coaxial 3D printer, and the solid propellant material is loaded into the printing cylinder of the outer shell layer of the coaxial 3D printer.

[0010] S3. Use slicing software to slice the propellant model to be printed to obtain a slice file; import the slice file into the coaxial 3D printer;

[0011] S4. Based on the sliced ​​file, the coaxial 3D printer simultaneously extrudes the thermally conductive composite material and the solid propellant material from the inner and outer needles of the coaxial printer to form a linear material.

[0012] S5. Repeat step S4 to accumulate the linear material layer by layer to form the propellant.

[0013] Preferably, the process further includes step S6, which involves curing the propellant obtained after printing to obtain the final propellant product.

[0014] Preferably, the thermally conductive composite material in step S1 includes a composite material with one or more of metal wires, metal fibers, graphite fibers, carbon nanotubes, and graphene as the thermally conductive main body and a polymer as the matrix.

[0015] Preferably, the polymer comprises one or more of the following: polyurethane, polyolefin, ethylene-vinyl acetate copolymer, and polymer elements and copolymers.

[0016] Preferably, the solid propellant material in step S1 includes double-base propellant, hydroxyl-butadiene propellant, and nitrate-plasticized polyether propellant.

[0017] Preferably, the printing cylinder in step S2 has a heating module to control the temperature within the range of 30°C to 80°C.

[0018] Preferably, the slicing software in step S3 includes Simplify3D and Cura.

[0019] Preferably, in step S4, the inner diameter of the inner and outer needles is between 0.1 mm and 3 mm; the inner needle is one of a triangular, square, pentagonal, or polygonal irregular structure, and the outer needle is one of a triangular, square, pentagonal, or polygonal irregular structure.

[0020] The second technical solution adopted in this invention is: a propellant produced by the coaxial 3D printing method described in the first technical solution, comprising linear materials stacked layer by layer, wherein the linear material is a core-shell structured linear material with a thermally conductive composite material core and a solid propellant material outer shell.

[0021] The beneficial effects of the above technical solution are as follows:

[0022] (1) The coaxial 3D printing method for improving the burning rate of solid propellant disclosed in this invention can control the thickness of the thermally conductive inner core and the propellant shell in the printed line, thereby achieving precise control over the burning rate and energy performance of the final propellant.

[0023] (2) This invention embeds thermally conductive composite material into solid propellant using coaxial 3D printing, thereby achieving rapid preparation of solid propellant and improved burning rate; the inner core layer of the printed linear shape is thermally conductive composite material, and the outer shell layer is solid propellant material, realizing the integrated rapid molding of two high-viscosity functional composite materials.

[0024] (3) This invention combines coaxial 3D printing and embedded thermally conductive composite material. Thermally conductive composite material and solid propellant material that can be 3D printed are extruded from the inner and outer needles of the coaxial 3D printer to form a linear material with a thermally conductive composite material core and a solid propellant material shell. The propellant column is printed by stacking layers one by one. This method realizes propellant molding and controllable finished product performance. At the same time, the method of embedding thermally conductive composite material can greatly improve the axial burning rate of solid propellant by increasing physical thermal conductivity, and can complete the preparation of complex propellant propellant shapes. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the coaxial 3D printing principle provided in one embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of a coaxial 3D printed linear structure provided in one embodiment of the present invention;

[0027] Figure 3 A schematic diagram of a coaxial 3D printed cross-section of a propellant grain provided in one embodiment of the present invention;

[0028] Among them, 1-thermally conductive composite material, 2-solid propellant material, 3-printing cylinder for inner core layer, 4-printing cylinder for outer shell layer, 5-inner needle for coaxial printing, 6-outer needle for coaxial printing, and 7-linear material. Detailed Implementation

[0029] The present invention will be further illustrated below with specific embodiments. It should be noted that those skilled in the art can make several modifications and improvements without departing from the principle of the present invention, and these should also be considered to fall within the protection scope of the present invention.

[0030] The terms “first,” “second,” etc. (if applicable) in the specification and claims are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data used in this way can be interchanged where appropriate so that the embodiments described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion, such as a process, method, system, product, or apparatus that comprises a series of steps or units, not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0031] The contents not described in detail in this specification are common knowledge to those skilled in the art.

[0032] This invention discloses a coaxial 3D printing method for improving the burning rate of solid propellants. The method includes forming a linear material with a thermally conductive composite core and a solid propellant shell using a coaxial 3D printer, and then printing the linear material layer by layer to obtain the propellant. Specifically, the method includes the following steps:

[0033] S1. Prepare thermally conductive composite materials and solid propellant materials for printing, respectively;

[0034] S2, such as Figure 1 As shown, the thermally conductive composite material is loaded into the printing barrel of the inner core layer of the coaxial 3D printer, and the solid propellant material is loaded into the printing barrel of the outer shell layer of the coaxial 3D printer; the printing barrel has a heating module, which makes the temperature adjustable in the range of 30℃ to 80℃.

[0035] S3. Slice the propellant model to be printed into slices using slicing software to obtain slice files; import the slice files into the coaxial 3D printer; the slicing software may be, for example, Simplify3D, Cura, etc.

[0036] S4. Based on the sliced ​​file, the coaxial 3D printer simultaneously extrudes the thermally conductive composite material and the solid propellant material from the inner and outer nozzles of the coaxial printer, respectively, to form a shape as shown in the image. Figure 2 The illustrated linear material has a core-shell structure;

[0037] S5. Repeat step S4, adding the linear material layer by layer to form a shape as shown in the image. Figure 3 The propellant shown is a propellant grain or other complex propellant structure; the shape of the propellant can be controlled by the propellant model to be printed, realizing the printing of complex propellant shapes;

[0038] S6. After printing, the propellant is cured at room temperature for 3 days, and then placed in a vacuum oven and cured at 50°C for 4 days to obtain the final propellant product.

[0039] The thermally conductive composite material includes, but is not limited to, composite materials with one or more of the following as the thermally conductive host: metal wire, metal fiber, graphite fiber, carbon nanotube, and graphene, and a polymer as the matrix. The polymer includes, but is not limited to, one or more of the following: polyurethane, polyolefin, ethylene-vinyl acetate copolymer, and other polymer elements and copolymers with a softening temperature below 80°C. The thermally conductive host and the matrix are directly mixed to obtain the thermally conductive composite material, and the mass of the thermally conductive host accounts for 1%-90% of the total mass of the thermally conductive composite material.

[0040] The solid propellant materials include, but are not limited to, common 3D-printable double-base propellants, hydroxyl-butadiene propellants, and nitrate-plasticized polyether propellants.

[0041] The inner diameter of the inner and outer needles of the coaxial printer is between 0.1mm and 3mm, and the specific needle parameters can be adjusted according to the printing situation and burning rate control requirements. By controlling the inner diameter of the inner and outer needles, the thickness of the heat-conducting inner core and the propellant shell can be controlled. The inner needle of the coaxial printer can be a triangular, square, pentagonal, polygonal, or other irregular shape to achieve different contact conditions between the heat-conducting inner core and the propellant shell. The outer needle of the coaxial printer can be a triangular, square, pentagonal, polygonal, or other irregular shape to achieve the required printing conditions.

[0042] Coaxial 3D printing technology, as a method for rapid prototyping of composite materials, has been extensively studied in fields such as biomaterials, ceramic materials, and metallic materials. This technology enables the rapid composite preparation of different materials by controlling the printing materials of the inner core layer and the outer shell layer, and can improve the performance of the overall printed sample by changing the composition of the printed composite material. Therefore, this invention combines coaxial 3D printing with embedded thermally conductive composite materials to achieve improved burning rate and rapid preparation of solid propellants.

[0043] The present invention also discloses a propellant prepared by the above-mentioned coaxial 3D printing method. The propellant comprises linear materials stacked layer by layer. The linear materials are linear materials with a core-shell structure, wherein the inner core is a thermally conductive composite material and the outer shell is a solid propellant material.

[0044] Example 1

[0045] A coaxial 3D printing method for carbon fiber / HTPB propellant (i.e., a coaxial 3D printing method for improving the burning rate of solid propellant) includes the following steps:

[0046] S1. Prepare a printable carbon fiber thermally conductive composite material 1 according to the formulation in Table 1, and prepare a hydroxyl-terminated polybutadiene (HTPB) solid propellant material 2 that can be used for 3D printing according to the formulation in Table 2.

[0047] Table 1 Examples of carbon fiber thermally conductive composite material formulations

[0048]

[0049]

[0050] Table 2 Examples of HTPB Solid Propellant Formulations

[0051] Formulation composition (HTPB solid propellant) mass content % Adhesive (hydroxyl-terminated polybutadiene) 8.5 Plasticizer (diisooctyl sebacate) 4 Various additives (bonding agent 3%, process aids 1%) 4 Oxidizing agent (ammonium perchlorate) 65 Metal fuel (aluminum powder) 18 Curing agent (toluene diisocyanate) 0.5

[0052] S2. Load the carbon fiber thermally conductive composite material 1 into the printing cylinder 3 of the inner core layer of the coaxial 3D printer, and load the HTPB solid propellant material 2 into the printing cylinder 4 of the outer shell layer of the coaxial 3D printer; the temperature of the printing cylinder is controlled at 40℃.

[0053] S3. Use the slicing software Simplify3D to slice the propellant grain model to be printed to obtain a slice file; import the slice file into the coaxial 3D printer;

[0054] S4. Based on the sliced ​​file, the coaxial 3D printer simultaneously extrudes the carbon fiber thermally conductive composite material 1 and the HTPB solid propellant material 2 from the inner needle 5 and the outer needle 6 of the coaxial printer, respectively, to form a linear material 7 with a core-shell structure; the inner needle 5 of the coaxial printer is a circle with a diameter of 0.5 mm, and the outer needle 6 is a circle with a diameter of 2 mm.

[0055] S5. Repeat step S4, and add the linear material 7 layer by layer to form a propellant grain;

[0056] S6. After printing, the propellant grains are cured at room temperature for 3 days, and then placed in a vacuum oven and cured at 50°C for 4 days to obtain the final propellant product (i.e., carbon fiber / HTPB propellant).

[0057] Referring to Method 706.1 "Burning Rate Target Line Method" of GJB770B-2005, the static burning rate of HTPB propellant and the carbon fiber / HTPB propellant prepared in Example 1 was tested at 6.86 MPa. No fewer than 5 test samples were tested under the same conditions. The test results are shown in Table 3.

[0058] Table 3 Static Burn Rate

[0059] Test sample <![CDATA[Static burning rate (mm·s -1 )]]> HTPB propellant 9.89 carbon fiber / HTPB propellant 12..09

[0060] As shown in Table 3, carbon fiber thermally conductive composite materials have good thermal conductivity and combustibility. When the propellant grain is ignited axially, the carbon fiber thermally conductive composite material can quickly transfer the high temperature at the burning surface of the propellant to the unburned propellant components, accelerate the combustion transfer process, and thus increase the burning rate of the propellant. Therefore, using coaxial 3D printing to prepare solid propellants is beneficial to improving the burning rate of solid propellants in the axial direction.

[0061] Example 2

[0062] A coaxial 3D printing method for graphene / PET propellant (i.e., a coaxial 3D printing method for improving the burning rate of solid propellant) includes the following steps:

[0063] S1. Prepare a printable graphene thermally conductive composite material 1 according to the formulation in Table 4, and prepare an ethylene oxide / tetrahydrofuran copolyether (PET) based solid propellant material 2 according to the formulation in Table 5.

[0064] Table 4 Examples of Graphene Thermally Conductive Composite Material Formulations

[0065] Formulation composition (graphene thermally conductive composite material) mass content % Thermally conductive substrate (graphene) 3 Polymer matrix (polycaprolactone) 97

[0066] Table 5 Examples of ethylene oxide / tetrahydrofuran copolyether (PET) based solid propellant formulations

[0067] Formulation composition (PET solid propellant) mass content % Adhesive (ethylene oxide / tetrahydrofuran coether) 6 Plasticizer (nitroglycerin / 1,2,4-butanetriol trinitrate) 6 Various additives (bonding agent 3%, process aids 2%) 5 Oxidizing agent (ammonium perchlorate) 65 Metal fuel (aluminum powder) 17 Curing agent (polyfunctional aliphatic isocyanate) 1

[0068] S2. The graphene thermally conductive composite material 1 is loaded into the printing cylinder 3 of the inner core layer of the coaxial 3D printer, and the PET-based solid propellant material 2 is loaded into the printing cylinder 4 of the outer shell layer of the coaxial 3D printer; the temperature of the printing cylinder is controlled at 50℃.

[0069] S3. Use the slicing software Simplify3D to slice the propellant cuboid block model to be printed to obtain a slice file; import the slice file into the coaxial 3D printer;

[0070] S4. Based on the sliced ​​file, the coaxial 3D printer simultaneously extrudes the graphene thermally conductive composite material 1 and the PET-based solid propellant material 2 from the inner needle 5 and the outer needle 6 of the coaxial printer, respectively, to form a linear material 7 with a core-shell structure; the inner needle 5 of the coaxial printer is a square with a side length of 0.5 mm, and the outer needle 6 is a circle with a diameter of 2 mm.

[0071] S5. Repeat step S4, and add the linear material 7 layer by layer to form a rectangular propellant block;

[0072] S6. After printing, the propellant cuboid block is cured at room temperature for 3 days, and then placed in a vacuum oven and cured at 50°C for 4 days to obtain the final propellant product (i.e., graphene / PET propellant).

[0073] The static burning rate of PET propellant and graphene / PET propellant prepared in Example 2 was tested at 6.86 MPa. At least five test samples were tested under the same conditions. The test results are shown in Table 6.

[0074] Table 6 Static Burn Rate

[0075]

[0076] As shown in Table 6, graphene thermally conductive composite materials have good thermal conductivity and combustibility. When the propellant grain is ignited axially, the graphene thermally conductive composite material can quickly transfer the high temperature at the burning surface of the propellant to the unburned propellant components, accelerate the combustion transfer process, and thus increase the burning rate of the propellant. Therefore, using coaxial 3D printing to prepare solid propellants is beneficial to improving the axial burning rate of solid propellants.

[0077] Example 3

[0078] A method for coaxial 3D printing of carbon fiber / HTPB propellant includes the following steps:

[0079] S1. Prepare a printable carbon fiber thermally conductive composite material 1 according to the formulation in Table 7, and prepare a hydroxyl-terminated polybutadiene (HTPB) solid propellant material 2 for 3D printing according to the formulation in Table 8.

[0080] Table 7 Examples of Carbon Fiber Thermally Conductive Composite Material Formulations

[0081] Formulation composition (carbon fiber thermally conductive composite material) mass content % Thermally conductive substrate (carbon fiber) 90 Polymer matrix (ethylene-vinyl acetate copolymer) 10

[0082] Table 8 Examples of HTPB Solid Propellant Formulations

[0083] Formulation composition (HTPB solid propellant) mass content % Adhesive (hydroxyl-terminated polybutadiene) 8.5 Plasticizer (diisooctyl sebacate) 4 Various additives (bonding agent 3%, process aids 1%) 4 Oxidizing agent (ammonium perchlorate) 65 Metal fuel (aluminum powder) 18 Curing agent (toluene diisocyanate) 0.5

[0084] S2. Load the carbon fiber thermally conductive composite material 1 into the printing cylinder 3 of the inner core layer of the coaxial 3D printer, and load the HTPB solid propellant material 2 into the printing cylinder 4 of the outer shell layer of the coaxial 3D printer; the temperature of the printing cylinder is controlled at 40℃.

[0085] S3. Use the slicing software Simplify3D to slice the propellant grain model to be printed to obtain a slice file; import the slice file into the coaxial 3D printer;

[0086] S4. Based on the sliced ​​file, the coaxial 3D printer simultaneously extrudes the carbon fiber thermally conductive composite material 1 and the HTPB solid propellant material 2 from the inner needle 5 and the outer needle 6 of the coaxial printer, respectively, to form a linear material 7 with a core-shell structure; the inner needle 5 of the coaxial printer is a circle with a diameter of 0.5 mm, and the outer needle 6 is a circle with a diameter of 2 mm.

[0087] S5. Repeat step S4, and add the linear material 7 layer by layer to form a propellant grain;

[0088] S6. After printing, the propellant grains are cured at room temperature for 3 days, and then placed in a vacuum oven and cured at 50°C for 4 days to obtain the final propellant product (i.e., carbon fiber / HTPB propellant).

[0089] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. These descriptions are exemplary and not exhaustive, and are not limited to the disclosed embodiments; the above descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and implementation methods of the present invention without departing from the spirit and scope of the present invention, and all such modifications and improvements fall within the scope of the present invention; the scope of protection of the present invention is determined by the appended claims.

Claims

1. A coaxial 3D printing method for improving the burning rate of solid propellants, characterized in that, The method includes forming a linear material with a thermally conductive composite material core and a solid propellant material shell using a coaxial 3D printer, and printing the linear material layer by layer to obtain the propellant; wherein, the thermally conductive composite material includes a composite material with one or more of metal wires, metal fibers, graphite fibers, carbon nanotubes, and graphene as the thermally conductive host and a polymer as the matrix; the mass of the thermally conductive host accounts for 1%-90% of the total mass of the thermally conductive composite material; the polymer includes one or more of polyurethane, polyolefin, ethylene-vinyl acetate copolymer, and polymer elements and copolymers.

2. The coaxial 3D printing method according to claim 1, characterized in that, Includes the following steps: S1. Prepare thermally conductive composite materials and solid propellant materials respectively; S2. The thermally conductive composite material is loaded into the printing cylinder of the inner core layer of the coaxial 3D printer, and the solid propellant material is loaded into the printing cylinder of the outer shell layer of the coaxial 3D printer. S3. Use slicing software to slice the propellant model to be printed to obtain slice files; Import the sliced ​​file into the coaxial 3D printer; S4. Based on the sliced ​​file, the coaxial 3D printer simultaneously extrudes the thermally conductive composite material and the solid propellant material from the inner and outer needles of the coaxial printer to form a linear material. S5. Repeat step S4 to accumulate the linear material layer by layer to form the propellant.

3. The coaxial 3D printing method according to claim 2, characterized in that, It also includes step S6, which involves curing the propellant obtained after printing to obtain the final propellant product.

4. The coaxial 3D printing method according to claim 2, characterized in that, The solid propellant materials in step S1 include double-base propellants, hydroxyl-butadiene propellants, and nitrate-plasticized polyether propellants.

5. The coaxial 3D printing method according to claim 2, characterized in that, The printing cylinder in step S2 has a heating module to control the temperature within the range of 30℃ to 80℃.

6. The coaxial 3D printing method according to claim 2, characterized in that, The slicing software used in step S3 includes Simplify3D and Cura.

7. The coaxial 3D printing method according to claim 2, characterized in that, In step S4, the inner diameter of the inner and outer needles is between 0.1mm and 3mm; the inner needle is one of a triangular, square, pentagonal, or polygonal irregular structure, and the outer needle is one of a triangular, square, pentagonal, or polygonal irregular structure.

8. A propellant prepared by the coaxial 3D printing method according to any one of claims 1-7, characterized in that, It includes a linear material (7) stacked layer by layer, wherein the linear material (7) is a core-shell structured linear material with a thermally conductive composite material (1) as the inner core and a solid propellant material (2) as the outer shell.

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