Sample preparation mold and sample preparation method for testing heat conductivity coefficient of variable-size material

Abstract

The invention discloses a sample preparation mold and a sample preparation method for testing the heat conductivity coefficient of a variable-size material. The sample preparation mold is characterized in that the sample preparation mold comprises a bottom plate, a combined female mold pressing plate, a thickness positioning plate suite and a male mold pressing plate, the bottom plate and the combined female mold pressing plate arranged above the bottom plate define cubic mold cavities of different sizes, and the thickness positioning plate suite is provided with a plurality of positioning plates of different thicknesses; the male mold pressing plate is arranged in a mold cavity and used for adjusting the thickness of the mold cavity, the male mold pressing plate is matched above the combined female mold pressing plate provided with a positioning plate with the corresponding thickness, the lower surface of the male mold pressing plate is flush with the upper end of the combined female mold pressing plate, and a plurality of flow guide grooves are formed in the upper edge of the combined female mold pressing plate. According to the invention, efficient and standardized sample preparation can be carried out on a thermal protection layer or a heat insulation layer of a solid engine, the surface flatness of a sample piece is good, the thickness is uniform, the sample piece cannot be adhered to a mold, and a basis is provided for the accuracy of a heat conductivity coefficient test.

Description

Technical Field

[0001] The invention relates to a solid engine thermal protection material performance testing technology, and in particular to a sample making mold and a sample making method for testing thermal conductivity of materials with variable sizes. Background Art

[0002] The shell, structural parts, valves, etc. of the solid engine are subject to high temperature, high pressure, airflow erosion, etc. when the engine is working. The high temperature of the combustion chamber increases the shell temperature through heat conduction, thereby reducing the shell's pressure resistance and directly affecting the reliability of the engine. In addition, in order to ensure the environmental adaptability and quality reliability of the solid engine, the solid engine needs to simulate the thermal flow field inside the combustion chamber, thermal insulation components, and nozzle during the optimization design. The thermophysical properties of its charge, heat protection materials, etc. are one of the prerequisites for the reliability of structural simulation.

[0003] Thermal conductivity is one of the thermophysical properties of materials. It is a physical quantity that characterizes the thermal conductivity of materials and is of great significance in engineering and scientific research. Since solid engines use special materials, most of them are materials that are difficult to obtain thermophysical parameters of, and some materials are synthetic or customized. There is no thermal conductivity data available for reference, and systematic and comprehensive measurements have not been obtained for a long time. Therefore, determining the thermal conductivity of the inner insulation layer and outer protective coating of solid engines can provide indispensable parameters for combustion calculations and structural integrity analysis in actual engine design work.

[0004] At present, there are many methods for measuring the thermal conductivity of solid materials at home and abroad, mainly including the heat plate method, heat flow meter method, transient plane heat source method, flash method, hot wire method, etc. Different measurement methods have different measurement ranges, applicable scopes, precision and accuracy, specimen size, etc. Among them, the heat flow meter method has the advantages of simple equipment, high precision and accuracy compared with other methods. It is more suitable for the determination of thermal conductivity of general solid thermal protection materials, polymer-based composite materials, and polymer materials. It is also the test method recommended by ISO and ASTM of the United States.

[0005] The heat flux meter type thermal conductivity instrument uses a water bath cycle to dissipate heat, and uses a heat flux meter and a thermocouple to measure the temperature and heat of the solid sample, thereby obtaining the thermal conductivity of the material. In order to obtain higher accuracy and repeatability requirements, the size and surface flatness of the sample must meet certain requirements. Due to the large size of the sample, it is impossible to obtain a suitable sample using ordinary sample preparation methods. Therefore, it is urgent to establish a sample preparation mold for testing the thermal conductivity of solid engine thermal protection materials. The mold has a simple structure and is easy to operate. It can prepare samples that meet the test requirements and provide data reference for the production, design and use of various solid engines. Summary of the invention

[0006] In order to overcome the above-mentioned defects, the present invention provides a sample making mold for testing the thermal conductivity coefficient of materials with variable sizes, characterized in that it includes a base plate, a combined female mold pressing plate, a thickness positioning plate kit, and a male mold pressing plate. The base plate and the combined female mold pressing plate arranged above the base plate form a mold cavity in the shape of a cube of different sizes. The thickness positioning plate kit has a plurality of positioning plates of different thicknesses, which are placed in the mold cavity to adjust the thickness of the mold cavity. The male mold pressing plate is matched with the combined female mold pressing plate with positioning plates of corresponding thicknesses. The lower surface of the male mold pressing plate is flush with the upper end of the combined female mold pressing plate, and a plurality of guide grooves are opened on the upper edge of the combined female mold pressing plate.

[0007] Furthermore, the combined female mold pressing plate is composed of a plurality of L-shaped female film pressing blocks and a plurality of rectangular female film pressing blocks, which are connected to the base plate by bolt connection, and a plurality of cavity frames of different sizes can be formed by selecting different female mold pressing blocks.

[0008] Furthermore, the combined female mold plate is composed of 4 L-shaped female film blocks of 75mm×25mm×30mm and 8 female film blocks of 50mm×25mm×30mm, and the combined cavity includes three cavity cubes of 200mm×200mm, 150mm×150mm, and 100mm×100mm; the thickness positioning plate kit is composed of 200mm×200mm×(5, 10, 15, 20mm), 150mm×150m m×(5, 10, 15, 20mm), 100mm×100mm×(5, 10, 15, 20mm), a total of 12 different positioning plates, which are combined with the combined female mold pressing plate to form 12 different sizes of cube cavities, including 200mm200mm×(25, 20, 15, 10mm), 150mm×150mm×(25, 20, 15, 10mm), and 100mm×100mm×(25, 20, 15, 10mm).

[0009] Furthermore, the screw holes on the combined female mold pressing plate correspond to the screw holes provided on the base plate, and are screwed to the base plate using hexagon socket bolts. According to the arrangement of the screw holes, they are combined into three cubic specimen specification cavities of 200mm×200mm×30mm, 150mm×150mm×30mm, and 100mm×100mm×30mm.

[0010] Furthermore, the guide grooves are symmetrically distributed along the center line on the upper end surface of the combined female mold platen and have a rectangular cross-section.

[0011] Furthermore, the bottom plate and the combined female mold pressing plate are both made of steel.

[0012] The present invention also provides a sample preparation method for testing the thermal conductivity of materials with variable sizes, which is characterized in that it uses the above-mentioned sample preparation mold for testing the thermal conductivity of materials with variable sizes, and includes the following steps: forming a mold cavity by a bottom plate, a combined female mold pressing plate, and a positioning plate, placing a preform of the material to be sampled into the mold cavity, covering it with a male mold pressing plate, removing bubbles in the preform, and then forming the preform of the material to be sampled. After the forming is completed, the combined female mold pressing plate and the male mold pressing plate are removed to obtain a sample.

[0013] Furthermore, the method comprises the following steps:

[0014] S1 puts the assembled sample preparation mold into an oven for preheating;

[0015] S2 spraying anti-adhesion material on the inner wall of the sample making mold cavity, placing an appropriate amount of the sample material preform into the sample making mold cavity, and covering it with a male mold pressing plate;

[0016] S3 uses a flat vulcanizing machine to apply a certain pressure to remove bubbles in the preform of the sample material to be prepared, and squeezes out excess material from the guide groove to ensure that the prepared sample is dense;

[0017] S4 shapes the preform of the material to be sampled inside the sample making mold;

[0018] When the preform of the material to be sampled is a solid engine thermal protection coating mixture, room temperature curing molding is adopted; when the preform of the material to be sampled is a green sheet of insulation layer material, heated vulcanization molding is adopted;

[0019] S5 After the sample mold is cooled to room temperature, the male mold pressing plate and the combined female mold pressing plate are removed in turn, and the sample is taken out and trimmed of the flash and set aside for use;

[0020] S6 Clean the sample preparation mold.

[0021] Furthermore, in step S3, a flat plate vulcanizing machine is used to remove bubbles in the preform of the sample material by inching pressurization. The specific method is to inching pressurize 5 to 8 times, each pressurization lasting about 1 to 2 minutes, and stop pressurization for about 1 minute for exhaust treatment.

[0022] Furthermore, in step S4, when the preform of the material to be sampled is a solid engine thermal protection coating mixture, it is cured at room temperature for 120±4 hours to form; when the preform of the material to be sampled is an insulation layer material raw sheet, the temperature of the heated vulcanization molding is 150±5°C, and the vulcanization molding time is 105min±15min.

[0023] The present invention can perform efficient and standardized sample preparation for the thermal protection layer or the thermal insulation layer of the solid engine, and the sample piece has good surface flatness and uniform thickness, and the sample piece will not adhere to the mold, providing a basis for the accuracy of the thermal conductivity test.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) In a sample preparation mold for testing thermal conductivity of a material of variable size according to the present invention, a cavity for preparing a cubic sample piece is formed by a detachable combined female mold pressing plate, a thickness positioning plate and a bottom plate. The installation and disassembly of the mold are simple, and the sample pieces formed have a variety of shapes, good consistency and high surface flatness, which provides a basis for the accuracy of thermal conductivity testing;

[0026] (2) In a sample preparation mold for testing thermal conductivity of a material with a variable size of the present invention, a plurality of guide grooves are provided, which further improves the accuracy of the size of the sample formed during extrusion;

[0027] (3) In a sample preparation method for testing the thermal conductivity of a material of the present invention, an anti-adhesion material is sprayed on the surface of the sample preparation mold in contact with the sample piece, which can prevent the sample piece from being damaged after adhesion between the sample piece and the mold body, thereby solving the problem of sample piece waste caused by uneven sample preparation thickness and sample piece damage during sampling, and greatly improving the qualified rate of thermal conductivity sample piece production;

[0028] (4) In the sample preparation method for testing the thermal conductivity of a material of the present invention, the processes of preparing the sample material preform, removing bubbles and forming are designed to ensure the quality of the sample;

[0029] (5) The present invention can obtain standardized samples of the inner insulation layer and outer protective coating of a solid engine suitable for testing by the heat flow meter method. The preparation method is simple and efficient. The surface of the sample is flat, the thickness is uniform, the qualified rate is high, the sample will not stick to the mold, and has a good use effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a sample preparation mold diagram for testing thermal conductivity of a material with variable size according to the present invention. DETAILED DESCRIPTION

[0031] The specific embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. By describing the present invention in detail, the features and advantages of the present invention will become clearer and more distinct with these descriptions.

[0032] The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise noted.

[0033] The sample preparation mold and sample preparation method for testing the thermal conductivity of materials with variable sizes of the present invention can be used for preparing thermal conductivity sample pieces of thermal protection materials for the inner thermal insulation layer and the outer protective coating of solid engines. The present invention can efficiently and standardizedly prepare samples for the thermal protection layer or the thermal insulation layer of solid engines, and the sample pieces have good surface flatness and uniform thickness, and the sample pieces will not adhere to the mold, which provides a basis for the accuracy of thermal conductivity testing.

[0034] Figure 1 This is a sample preparation mold diagram for testing the thermal conductivity of a variable-size material according to the present invention. Figure 1 The present invention discloses a sample preparation mold for testing thermal conductivity coefficient of variable-size materials for thermal protection of solid motors, comprising a bottom plate, a combined female mold pressing plate, a thickness positioning plate set, a male mold pressing plate and bolts. The bottom plate and the combined female mold pressing plate placed above the bottom plate form a mold cavity in the shape of a cube of different sizes. The thickness positioning plate set has a plurality of positioning plates of different thicknesses, which are placed in the mold cavity to adjust the thickness of the mold cavity. The male mold pressing plate is matched with the combined female mold pressing plate with positioning plates of corresponding thicknesses.

[0035] The combined female mold pressing plate is composed of a plurality of female mold pressing blocks, which are connected to the base plate by bolt connection. The plurality of female mold pressing blocks can be combined into cavity frames of various sizes, for example, three square cavity frames of different sizes. A plurality of guide grooves are opened on the upper edge of the combined female mold pressing plate. The combined female mold pressing plate is located above the base plate, and the combined female mold pressing plate is connected to the base plate by bolts. Together with the thickness positioning plate of the corresponding size, the cubic cavity is formed for the production of sample pieces. When each female mold pressing block is placed above the base plate, the projection on the base plate is a rectangle, which is connected by bolts.

[0036] In one embodiment, each combined female mold platen assembly is provided with a guide groove connecting the inside and outside of the mold cavity, and the number of the guide grooves is 1 to 2. The cross section of the guide groove is rectangular, and the guide grooves are evenly and symmetrically distributed, with a distance of 5 cm between each other. The guide grooves are symmetrically distributed along the center line on the upper end surface of the combined female mold platen, and the width of the guide groove is 5 mm.

[0037] Preferably, the combined female mold plate and the base plate are connected by hexagon socket bolts.

[0038] In one embodiment, the sample preparation mold further includes hexagon socket bolts. In addition to the four top corner positions, the combined female mold plate has a first bolt hole at every 25mm position. The edge of the bottom plate is provided with a second bolt hole corresponding to the first bolt hole. The hexagon socket bolts pass through the second bolt hole and the first bolt hole to achieve the connection between the combined female mold plate and the bottom plate. According to the arrangement of the bolt holes, the combination can be formed into three cubic sample specification cavities of 200mm×200mm×30mm, 150mm×150mm×30mm, and 100mm×100mm×30mm. The hexagon socket bolts are positioned and connected from bottom to top by the lower bottom plate and the combined female mold plate.

[0039] Preferably, the combined female mold pressing plate is made of No. 8 channel steel, the screw holes on the combined female mold pressing plate correspond to the screw holes provided on the base plate, the combined female mold pressing plate is composed of 4 L-shaped female film pressing blocks of 75mm×25mm×30mm and 8 female film pressing blocks of 50mm×25mm×30mm, and is screwed to the base plate with hexagonal bolts. According to the arrangement of the bolt holes, the combination can be formed into three cubic specimen specification cavities of 200mm×200mm×30mm, 150mm×150mm×30mm, and 100mm×100mm×30mm.

[0040] Preferably, a 25mm×5mm×2mm guide groove is opened on the upper end surface of the combined female mold pressing plate, and the guide groove is symmetrically distributed along the center line of the upper end surface of the combined female mold pressing plate to facilitate the extrusion and overflow of excess material when pressing the sample.

[0041] In one embodiment, the combined female mold plate is composed of 4 L-shaped female film blocks of 75mm×25mm×30mm and 8 female film blocks of 50mm×25mm×30mm to form different cubic cavities. Each female mold block is placed above the bottom plate and fixed to the bottom plate by limit screws. Multiple female mold blocks can be limited and connected by bolts to form three types of cavity cubes, such as 200mm×200mm, 150mm×150mm, and 100mm×100mm. A 25mm×5mm×2mm guide groove can be opened on the upper end of each female film block.

[0042] The bottom plate is located at the bottom, and the corresponding position of the bottom plate has screw holes connected with the combined female mold pressing plate. The bottom plate and the combined female mold pressing plate placed above the bottom plate form a cubic mold cavity, and cooperate with the corresponding thickness positioning plate to form a mold cavity frame.

[0043] In one embodiment, the bottom plate is square. Preferably, the bottom plate is square, made of No. 20 steel, with a thickness of 20 mm, and a plurality of screw holes are drilled on the bottom plate corresponding to the combined female mold plate thereon.

[0044] In one embodiment, the base plate and the combined female mold plate are both made of steel.

[0045] The thickness positioning plate is placed on the bottom plate and forms a cubic mold cavity with the combined female mold plate. The thickness positioning plate kit consists of various positioning plates such as 100mm×100mm×thickness, 150mm×150mm×thickness, and 200mm×200mm×thickness.

[0046] In one embodiment, the thickness positioning plate kit consists of 12 different positioning plates, namely 200mm×200mm×(5, 10, 15, 20mm), 150mm×150mm×(5, 10, 15, 20mm), and 100mm×100mm×(5, 10, 15, 20mm), which are combined with the combined female mold plate to form 12 cube cavities of different sizes, namely 200mm×200mm×(25, 20, 15, 10mm), 150mm×150mm×(25, 20, 15, 10mm), and 100mm×100mm×(25, 20, 15, 10mm).

[0047] Preferably, the thickness positioning plate kit is combined with the combined female mold pressing plate to form a cube cavity of 12 different sizes, namely 200mm×200mm×(25, 20, 15, 10mm), 150mm×150mm×(25, 20, 15, 10mm), and 100mm×100mm×(25, 20, 15, 10mm).

[0048] The male mold platen is matched with the upper part of the combined female mold platen, and the lower surface of the male mold platen is flush with the upper end of the combined female mold platen. The male mold platen is located above the combined female mold platen, and after the sample material preform is placed in the cavity formed by the combined female mold platen and the bottom plate, the sample piece between the male mold platen and the bottom plate is pressurized and vulcanized or cured at room temperature.

[0049] Preferably, the inner surfaces of the bottom plate, the combined female mold platen, and the male mold platen are sprayed with anti-adhesion materials, and the non-parallelism of the surfaces should be within ±2% of the material thickness. Preferably, the anti-adhesion material is polytetrafluoroethylene. In one embodiment, in order to facilitate demoulding, the inner surfaces of the bottom plate, the combined female mold platen, the thickness positioning plate, and the male mold platen are sprayed with polytetrafluoroethylene, which can effectively prevent the adhesion between the sample and the mold body and cause damage to the sample surface, solve the problem of sample scrapping caused by uneven sample thickness and sample damage during sampling, and greatly improve the qualified rate of the prepared samples.

[0050] The present invention also provides a sample preparation method for testing the thermal conductivity of materials with variable sizes, which can be used for testing the thermal conductivity of thermal protection materials for solid engines. The method adopts the sample preparation mold for testing the thermal conductivity of materials with variable sizes to ensure its implementation, and includes the following steps: placing a preform of the material to be sampled into the cavity of the above-mentioned sample preparation mold, covering it with a positive mold pressing plate, removing bubbles in the preform, and then forming the preform of the material to be sampled. After the forming is completed, the combined negative mold pressing plate and the positive mold pressing plate are removed to obtain the sample.

[0051] This sample making mold can be used to make fluid materials, rubber matrix materials and coating materials, etc. The production method and steps are as follows:

[0052] S1, placing the assembled sample preparation mold into an oven for preheating;

[0053] S2, placing an appropriate amount of the preform of the material to be sampled into the sample making mold cavity and covering it with a male mold pressing plate.

[0054] Preferably, the anti-adhesion material is first sprayed on the inner wall of the sample mold cavity, and then the preform of the sample material to be prepared is placed in the sample mold cavity. The anti-adhesion material is polytetrafluoroethylene; the non-parallelism between the inner wall of the sample mold cavity and the lower surface of the male mold plate after the anti-adhesion material is sprayed is within 2% of the thickness of the sample piece; the thickness of the sample piece is equal to the thickness of the combined cube cavity.

[0055] When the material to be prepared is a solid engine thermal protection coating, the method for preparing the solid engine thermal protection coating mixture is to first weigh and mix the components of the solid engine thermal protection coating mixture, and then use a coating mixer to mix them evenly.

[0056] When the coating mixer is mixing, the speed is controlled to gradually increase from 50 to 60 rpm to 500 to 600 rpm, and the mixing time is about 10 to 15 minutes to fully mix the components.

[0057] S3, using a flat vulcanizing machine to apply a certain pressure to remove bubbles in the preform of the sample material to be prepared, and squeeze out the excess material from the guide groove to ensure that the prepared sample is dense;

[0058] Preferably, a flat plate vulcanizer is used to remove bubbles in the preform of the sample material by inching pressurization. The specific method is to inching pressurize 5 to 8 times, each pressurization lasting about 1 to 2 minutes, and stop pressurization for about 1 minute to exhaust gas.

[0059] S4, forming a preform of the material to be sampled inside the sample making mold;

[0060] When the preform of the material to be prepared is a solid engine thermal protection coating mixture, room temperature curing is used for molding, and when the preform of the material to be prepared is a heat insulation layer material green sheet, heated vulcanization is used for molding. Preferably, when the preform of the material to be prepared is a solid engine thermal protection coating mixture, room temperature curing for 120±4 hours is used for molding.

[0061] S5, after the sample making mold is cooled to room temperature, the male mold pressing plate and the combined female mold pressing plate are removed in sequence, and the sample is taken out and the flash is trimmed and set aside for use;

[0062] S6, clean the sample preparation mold.

[0063] When the preform of the material to be sampled is a green sheet of the thermal insulation layer material, the temperature of the heated vulcanization molding is 150±5°C, and the vulcanization molding time is 105min±15min.

[0064] The present invention provides a method for preparing a sample preparation mold for testing thermal conductivity of a solid engine thermal protection material, comprising the following steps:

[0065] 1) Place the sample preparation mold to be tested in an oven for preheating;

[0066] 2) preparing a sample material preform;

[0067] 3) After taking out the sample preparation mold, the sample material preform is placed in the combined mold cavity and covered with a male mold plate; when the sample material to be prepared is a solid engine thermal protection coating, the sample material preform is a solid engine thermal protection coating mixture; when the sample material to be prepared is an insulation layer, the sample material preform is an insulation layer sample material green sheet;

[0068] 4) Using a flat vulcanizing machine, the mold containing the sample material preform is repeatedly pressurized to remove bubbles; a pressurization interval is left between each pressurization to ensure that the bubbles in the sample material preform in the mold overflow;

[0069] 5) After the insulation layer sample material is molded in place, the insulation layer sample material green sheet is heated, pressurized and vulcanized;

[0070] 6) After the mold cools to room temperature, first remove the positive film pressing plate on top, then remove the combined negative mold pressing plate, take out the thermal conductive sample, trim off the flash and set aside;

[0071] 7) Mold cleaning: The residual insulation layer and coating solidified materials in the mold should be removed by lightly dragging with a knife to avoid damaging the polytetrafluoroethylene material coated on the surface. Then wipe and clean the mold surface with a microfilament dipped in ethyl acetate.

[0072] Preferably, in the step 2), the various components used to prepare the thermal protection coating for solid motors are first weighed and mixed, and then stirred and mixed using a coating mixer, with the mixing speed gradually increasing from 50 to 60 rpm to 500 to 600 rpm, and the mixing time is about 10 to 15 minutes to make it uniform.

[0073] Preferably, the pressurization is performed 5 times in step 4), and the pressurization is stopped after 1 minute, and the air is exhausted after standing for 1 minute.

[0074] Preferably, in the step 5), after the green sheet of the heat insulating layer material is molded into place, the pressure is 12-15 MPa, heated to 150±5° C., and vulcanized for 105 min±15 min.

[0075] Preferably, in step 5), the solid engine thermal protection coating mixture is cured at room temperature for 120±4 hours.

[0076] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

[0077] It should be noted that the above is only an illustrative description and explanation of the present invention, and those skilled in the art should understand that any modification and replacement of the present invention belongs to the protection scope of the present invention.

Claims

1. A sample preparation mold for testing thermal conductivity of materials with variable size, characterized in that: It includes a base plate, a combined female mold pressing plate, a thickness positioning plate kit, and a male mold pressing plate. The base plate and the combined female mold pressing plate placed above the base plate form a mold cavity in the shape of a cube of different sizes. The thickness positioning plate kit has a plurality of positioning plates of different thicknesses, which are placed in the mold cavity to adjust the thickness of the mold cavity. The male mold pressing plate is matched with the combined female mold pressing plate with positioning plates of corresponding thickness. The lower surface of the male mold pressing plate is flush with the upper end of the combined female mold pressing plate, and a plurality of guide grooves are opened on the upper edge of the combined female mold pressing plate.

2. The sample preparation mold for testing thermal conductivity of materials with variable sizes according to claim 1, characterized in that: The combined female mold pressing plate is composed of a plurality of L-shaped female film pressing blocks and a plurality of rectangular female film pressing blocks, which are connected to the bottom plate by bolt connection, and a plurality of cavity frames of different sizes are formed by selecting different female mold pressing blocks.

3. The sample preparation mold for testing thermal conductivity of materials with variable size according to claim 1, characterized in that: The combined female mold plate is composed of 4 L-shaped female film blocks of 75mm×25mm×30mm and 8 female film blocks of 50mm×25mm×30mm. The combined cavity includes three cavity cubes of 200mm×200mm, 150mm×150mm and 100mm×100mm. The thickness positioning plate kit is composed of 200mm×200mm×(5, 10, 15, 20mm), 150mm×150mm×(5 , 10, 15, 20mm), 100mm×100mm×(5, 10, 15, 20mm), a total of 12 different positioning plates, which are combined with the combined female mold pressing plate to form 200mm×200mm×(25, 20, 15, 10mm), 150mm×150mm×(25, 20, 15, 10mm), 100mm×100mm×(25, 20, 15, 10mm), a total of 12 cube cavities of different sizes.

4. A sample preparation mold for testing thermal conductivity of materials with variable size according to claim 3, characterized in that: The screw holes on the combined female mold pressing plate correspond to the screw holes on the base plate, and are screwed to the base plate using hexagonal bolts. According to the arrangement of the screw holes, they are combined into three cubic sample specification cavities of 200mm×200mm×30mm, 150mm×150mm×30mm, and 100mm×100mm×30mm.

5. The sample preparation mold for testing thermal conductivity of materials with variable sizes according to claim 1, characterized in that: The guide grooves are symmetrically distributed along the center line on the upper end surface of the combined female mold pressing plate, and have a rectangular cross section.

6. The sample preparation mold for testing thermal conductivity of materials with variable sizes according to claim 1, characterized in that: The bottom plate and the combined female mold pressing plate are both made of steel material.

7. A method for preparing samples for testing thermal conductivity of materials with variable sizes, characterized in that: The sample-making mold for testing the thermal conductivity of materials with variable sizes according to any one of claims 1 to 6 comprises the following steps: forming a mold cavity by means of a bottom plate, a combined female mold pressing plate, and a positioning plate, placing a preform of the material to be sampled into the mold cavity, covering it with a male mold pressing plate, and forming the preform of the material to be sampled after removing bubbles in the preform. After the forming is completed, the combined female mold pressing plate and the male mold pressing plate are removed to obtain a sample.

8. The sample preparation method for testing thermal conductivity of materials with variable sizes according to claim 7, characterized in that: The steps include: S1 puts the assembled sample preparation mold into an oven for preheating; S2 spraying anti-adhesion material on the inner wall of the sample making mold cavity, placing an appropriate amount of the sample material preform into the sample making mold cavity, and covering it with a male mold pressing plate; S3 uses a flat vulcanizing machine to apply a certain pressure to remove bubbles in the preform of the sample material to be prepared, and squeezes out excess material from the guide groove to ensure that the prepared sample is dense; S4 shapes the preform of the material to be sampled inside the sample making mold; When the preform of the material to be sampled is a solid engine thermal protection coating mixture, room temperature curing molding is adopted; when the preform of the material to be sampled is a green sheet of insulation layer material, heated vulcanization molding is adopted; S5 After the sample making mold is cooled to room temperature, the male mold pressing plate and the combined female mold pressing plate are removed in turn, and the sample is taken out and the flash is trimmed and set aside for use; S6 Clean the sample preparation mold.

9. The sample preparation method for testing thermal conductivity of materials with variable sizes according to claim 8, characterized in that: In step S3, a flat plate vulcanizing machine is used to remove bubbles in the preform of the sample material by inching pressurization. The specific method is to inching pressurize 5 to 8 times, each pressurization lasting about 1 to 2 minutes, and stop pressurization for about 1 minute to perform exhaust treatment.

10. A sample preparation method for testing thermal conductivity of a material according to claim 8, characterized in that: In the step S4, when the preform of the material to be sampled is a solid engine thermal protection coating mixture, it is cured at room temperature for 120±4 hours to form; when the preform of the material to be sampled is an insulation layer material green sheet, the temperature of the heated vulcanization molding is 150±5°C, and the vulcanization molding time is 105min±15min.

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