A design method for forming a mold for a multi-curved sandwich structure external heat protection material

Abstract

The present invention relates to a multi-curved sandwich structure external heat protection material forming mold and method, the multi-curved sandwich structure external heat protection material forming mold design method includes selecting forming mold material; designing forming mold structure; selecting reference surface and setting forming mold processing accuracy; assembling mold and testing mold air tightness, wherein the forming mold is composed of an upper mold, a lower mold and a plurality of side strips, the upper mold, the lower mold and the side strips have a profile contacting with the external heat protection material, a matching surface contacting with other mold parts and positioning holes for plugging and fixing each other, and the upper mold, the lower mold and the side strips are plugged and positioned through the positioning holes, and the position side strips are positioned by limit blocks. The method of the present invention is simple, easy to operate, and has little environmental pollution. It can form product profiles with net dimensions, greatly improve the qualified rate of components, and has good market application prospects in the fields of aerospace industry, civil industry, etc.

Description

Technical Field

[0001] The invention relates to the technical field of aerospace thermal protection, and in particular to a method for designing a molding die for an external heat protection material with a multi-curved sandwich structure. Background Art

[0002] With the development of aerospace technology, the flight speed of aerospace vehicles is constantly increasing, and the service environment is becoming increasingly harsh. An effective thermal protection system can provide sufficient protection for the aircraft structure when it faces severe aerodynamic heating, so that the aircraft is free from the damage of the harsh aerodynamic thermal environment and can maintain safe flight for a longer time. A reliable thermal protection system is one of the key systems for the safe flight of high-performance aircraft, and the design of its thermal protection structure and the selection of thermal protection materials are the key to the design and development of the thermal protection system.

[0003] According to the flight mission requirements and thermal environment analysis results of the aircraft, and taking into account the heating environment, mechanical environment, number of uses, cost and other factors, different types of thermal protection systems are used in different parts of the aircraft. The main thermal protection systems can be divided into three categories: passive thermal protection systems, active thermal protection systems and semi-passive thermal protection systems, and each type of thermal protection system includes several types of thermal protection structures.

[0004] Heat protection structures generally include endothermic structures, radiant structures, ablative structures, and sweating structures. Endothermic structures, also known as heat sink structures, are a way of achieving heat protection by absorbing heat through the material's own heat capacity. Structural materials with large specific heat capacity, high melting point, and high thermal conductivity are usually used. Ablative heat protection structures achieve heat protection by absorbing heat through phase change and mass exchange of materials. Materials with low thermal conductivity and high phase change temperature are usually used. Radiant heat protection structures consist of a heat-resistant outer skin, an insulation layer, and an internal structure. The outer skin is made of a heat-resistant material with high emissivity or a material coated with a high emissivity coating on the surface. When heated, it dissipates heat outward in the form of radiation. Sweating structures utilize gaseous or liquid sweating agents to squeeze out from a porous surface and decompose and vaporize, and utilize the vaporization of solid heating agents under pneumatic heating to absorb heat.

[0005] Heat protection materials are functional materials used to ensure the normal operation of aircraft in special aerodynamic thermal environments. They not only protect aircraft from damage in aerodynamic thermal environments, but also keep the protected structure within the specified operating temperature range, while also ensuring the aerodynamic characteristics of the structure. Passive thermal protection systems mainly use antioxidant carbon / carbon, ceramics or their corresponding metal-based composite materials; in active thermal protection systems, various structures mostly use metal materials; in semi-passive thermal protection systems, high-temperature metal heat pipes, carbon / carbon or ceramic-based composite panels are used in heat pipe structures, and ablative structures mostly use ablative materials.

[0006] In the field of thermal protection structures for aerospace vehicles, in order to solve the problem of brittleness of ceramic fiber rigid insulation tiles, domestic experts have innovatively proposed sandwich structure thermal protection materials. This type of material has the advantages of high panel strength, high strain coordination ability, erosion resistance and excellent thermal insulation effect.

[0007] For example, CN203628151U discloses a high-temperature resistant integrated rigid insulation component, which includes a rigid fiber insulation layer; an aerogel penetration layer penetrated into the rigid fiber insulation layer; and a fiber fabric panel reinforcement layer on at least one side of the rigid fiber insulation layer, wherein the rigid fiber insulation layer and the fiber fabric panel reinforcement layer are sewn together by sewing fiber threads.

[0008] For another example, CN206885331U discloses a composite thermal protection layer for a spacecraft, comprising a load-bearing metal shell, a lightweight foam ceramic block, a metal-coated film, a polypropylene resin layer and an air duct. The upper end surface of the load-bearing metal shell is covered with an inorganic fiber felt insulation layer, and columns are arranged around the outer periphery of the load-bearing metal shell. The lightweight foam ceramic block is evenly engaged in the thermal protection layer. A cavity is arranged at the bottom end of the thermal protection layer, and the cavity is filled with pure inert gas. The metal-coated film covers the outer surface of the thermal protection layer, and reinforcing ribs are arranged on the metal-coated film. The polypropylene resin layer is connected between the lightweight foam ceramic block and the honeycomb buffer interlayer, a heat-proof mesh pad is fixedly connected to the honeycomb buffer interlayer, air holes are arranged on the contact surface between the heat-proof mesh pad and the metal-coated film, and the air duct is installed on one side of the cavity.

[0009] Sandwich structure thermal protection materials are usually prepared by integrated stitching of core insulation materials and upper and lower ceramic panels. The core insulation material is generally prepared from flexible cotton felt composite aerogel insulation filler, and the upper and lower panels are prepared from continuous fiber reinforcement composite ceramic matrix. The upper panel, aerogel insulation core layer, and lower panel are connected by ceramic stitching lines.

[0010] CN108032580A discloses a method for preparing a sandwich structure thermal protection material, wherein the sandwich structure comprises an upper panel, a lower panel and an aerogel insulation core panel located between the upper panel and the lower panel, wherein the preparation method comprises providing a resin coating, a fiber braid and a sandwich preform, wherein the sandwich preform comprises an upper panel, a lower panel and an aerogel insulation core panel located between the upper panel and the lower panel; pre-impregnating the fiber braid in the resin coating, then taking it out and drying it naturally at room temperature to obtain a pre-impregnated fiber braid; laying the pre-impregnated fiber braid on the upper panel and compacting it; and wrapping the sandwich preform with the pre-impregnated fiber braid with a release cloth and curing it to obtain a thermal protection material having a resin composite fiber braid protective layer formed on the upper panel.

[0011] At present, for the external heat protection materials of the sandwich structure at the complex curved surface position, the block method is still adopted at the flange position, and then the block-molded materials are bonded to the corresponding positions on the surface of the metal cabin to composite the heat protection material on the surface of the metal cabin. For example, CN110948905A discloses a net size molding method for a honeycomb sandwich structure grid, including preparing a grid honeycomb core to be processed to the net size, using upper and lower combined molds and limiting tooling to limit the honeycomb sandwich structure grid, flanging the grid using the peripheral surfaces of the upper and lower combined molds as the forming working surfaces of the grid flanging, compensating the surrounding of the honeycomb sandwich structure with foam glue, and then using a hot autoclave to solidify the grid for net size molding.

[0012] However, the discontinuity caused by the block division will bring about problems such as long processing time and complicated processing procedures. After the parts are bonded, there will be joint gaps on the surface of the product, which will cause certain risks during use. In addition, there is a relative lack of integrated molding of heat-resistant materials for complex curved sandwich structures, especially for the surface with small rounded corners that meet the precision requirements of the net size molding. Therefore, the existing technology needs to be further improved in the design and molding of molds for heat-resistant materials for complex curved sandwich structures.

[0013] In addition, on the one hand, there are differences in understanding among those skilled in the art; on the other hand, the applicant studied a large number of documents and patents when making the present invention, but due to space limitations, not all details and contents are listed in detail. However, this does not mean that the present invention does not have the characteristics of these prior arts. On the contrary, the present invention already has all the characteristics of the prior art, and the applicant reserves the right to add relevant prior art to the background technology. Summary of the invention

[0014] The present invention provides a method for designing a molding mold for an external heat-resistant material with a multi-curved sandwich structure. By setting a reference plane, changing the mold structure and the mold closing sequence, controlling the pin fit and position accuracy, a multi-curved sandwich structure external heat-resistant material that meets the surface accuracy requirements is prepared to solve at least one or more technical problems existing in the prior art.

[0015] Preferably, the method for designing a molding mold for an external heat protection material with a multi-curved sandwich structure provided by the present invention can be applied to the formation process of fiber-reinforced aerogel materials and their sandwich structure composite materials. An external heat protection material with complex multi-curved surfaces can be obtained through the processes of preform laying, sequential mold closing, vacuum-pressure impregnation, and curing molding.

[0016] To achieve the above object, the present invention provides a method for designing a molding die for a multi-curved sandwich structure external heat-resistant material, comprising:

[0017] Selection of molding die materials.

[0018] Molding die structure design.

[0019] Reference surface selection and molding mold processing accuracy.

[0020] Assembly and airtightness test.

[0021] Preferably, in the present invention, the surface accuracy of the product is ensured by the mold, and the edges are cut.

[0022] Preferably, the material of the forming mold is generally selected from one or more of 45# steel, aluminum alloy, stainless steel and P20.

[0023] Preferably, the present invention provides a molding die, the molding die comprising:

[0024] A first mold having a first molding surface in contact with the outer heat-proof material, a positioning hole for plugging and fixing, and a first matching surface in contact with at least one mold component;

[0025] A second mold having a second molding surface in contact with the outer heat-proof material, a positioning hole for plugging and fixing, and a second matching surface in contact with at least one mold component; and

[0026] A plurality of edge strips extend between the first mold and the second mold, and have a third profile in contact with the external heat-proof material, a positioning hole for plugging and fixing, and a third mating surface in contact with at least one mold component. In particular, the present invention adopts a method of nearly net-forming of the molding mold to achieve integrated molding of the flanging area. By changing the mold design method, the molding accuracy of the flanging can be effectively guaranteed. The molding method of the flanging area in the present invention does not need to use foam glue for compensation, and the molding problem of the flanging area can be solved by mold design, and the molding accuracy is high.

[0027] Preferably, in the present invention, the first mold, the second mold and a plurality of side strips are positioned by latch members, and the local side strips are positioned by limit blocks.

[0028] Preferably, the positioning pin position accuracy is less than ±0.1 mm.

[0029] Preferably, an interference fit is adopted between the positioning pin and the first mold and the second mold.

[0030] Preferably, a small clearance fit is adopted between the positioning pin and the positioning hole.

[0031] Preferably, in the molding die processing link, the YZ reference plane, the XZ reference plane and the matching surface should be selected as the reference planes for processing.

[0032] Preferably, the flatness and verticality of the processing reference surface of the molding die should be ≤0.07mm, and the profile accuracy should be less than ±0.2mm. Furthermore, the profile accuracy should be less than ±0.1mm.

[0033] Preferably, in the assembly process of the molding die, the fitting clearance between the first die, the second die and the edge strip should be less than 0.05 mm.

[0034] Preferably, in the air tightness test of the molding die, at a pressure of 0.6 MPa to 0.9 MPa, it should be ensured that there is no pressure change in the molding die within 20 to 60 minutes.

[0035] Preferably, the present invention also provides a method for forming a multi-curved sandwich structure outer heat protection material, comprising:

[0036] placing a second mold;

[0037] Install at least one edge strip on the second mold in a preset marking sequence and pre-tighten it by means of a latch member;

[0038] Placing each panel layer of the multi-curved sandwich structure outer heat protection material in a forming mold according to a preset laying order, and fitting and clamping the forming mold at least through the edge strip profile of the forming mold;

[0039] Installing the first mold and locking the molding mold;

[0040] The multi-curved sandwich structure precursor placed in the molding mold is subjected to vacuum pressure impregnation, curing, drying and sintering to form the multi-curved sandwich structure external heat protection material through the molding mold.

[0041] The beneficial technical effects of the present invention include: the present method can be used to realize the molding of complex curved surface sandwich structure external heat protection materials, and the prepared sandwich structure composite material is near net molding, and the overall surface accuracy is high without processing. In particular, the present invention uses positioning pins and limit positioning features to ensure the surface accuracy of the product; secondly, the present method is simple, easy to operate, and has little environmental pollution; in addition, the present method can be used to mold components of various shapes and specifications, such as multi-curved special-shaped components, and is particularly suitable for various special-shaped components with complex surfaces, and has a wide market application prospect in the aerospace industry environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is one of the isometric structural schematic diagrams of a molding die of a method for designing a molding die for an external heat-resistant material with a multi-curved sandwich structure in a preferred embodiment provided by the present invention;

[0043] Figure 2 It is one of the isometric structural cross-sectional views of a molding die of a method for designing a molding die for an external heat-resistant material with a multi-curved sandwich structure in a preferred embodiment of the present invention;

[0044] Figure 3This is the second isometric structural schematic diagram of a molding die of a method for designing a molding die for an external heat-resistant material with a multi-curved sandwich structure in a preferred embodiment of the present invention;

[0045] Figure 4 This is the second isometric structural sectional view of a molding die of a method for designing a molding die for an external heat protection material with a multi-curved sandwich structure according to a preferred embodiment of the present invention.

[0046] Reference numerals list

[0047] 1: first mold; 2: second mold; 3: side strip; 4: latch; 5: limit block; 61: YZ reference plane; 62: XZ reference plane; 63: XY reference plane; 7: sealing groove. DETAILED DESCRIPTION

[0048] The following is a detailed description with reference to the accompanying drawings.

[0049] The present invention provides a method for designing a molding die for an external heat-resistant material having a multi-curved sandwich structure. The method for designing a molding die for an external heat-resistant material having a multi-curved sandwich structure may specifically include the following steps:

[0050] Step 1: Select the molding mold material;

[0051] Step 2: Design the molding die structure;

[0052] Step 3: Select the reference surface and set the processing accuracy of the molding die;

[0053] Step 4: Assemble the mold and test the mold air tightness.

[0054] Molding mold material

[0055] According to a preferred embodiment, the material selection of the forming mold includes but is not limited to 45# steel, aluminum alloy, magnesium alloy, titanium alloy, stainless steel and P20.

[0056] In particular, the choice of mold material usually depends on the material properties and functional requirements of the composite sandwich structure, and specifically involves many factors such as mold machining, thermal expansion rate, thermal conductivity, density, stiffness, strength, precision, weight, cost, dimensional stability and life.

[0057] In the mold forming method, the multi-curved sandwich structure composite material is molded and will experience temperature rise, and the strength and thermal deformation of the mold material must be taken into consideration. In some embodiments, the mold material is 45# steel or stainless steel.

[0058] Preferably, 45# steel is selected for forming molds that only have thermal insulation requirements. This material has higher cutting performance and is more economical. To ensure the use of the mold, an organic coating needs to be sprayed in advance for rust prevention.

[0059] Molding mold structure

[0060] According to a preferred embodiment, Figure 1 As shown, the molding mold of the present invention is composed of a first mold 1 (upper mold), a second mold 2 (lower mold) and a plurality of side strips 3.

[0061] According to a preferred embodiment, Figure 1 As shown, the side strip 3 is positioned with the first mold 1 (upper mold) and the second mold 2 (lower mold) by means of a latch member 4. Specifically, the latch member 4 may be a pin.

[0062] According to a preferred embodiment, the first mold 1 has a first molding surface in contact with the outer heat-proof material and a first mating surface in contact with other mold components (such as the top surface of the edge strip 3). Furthermore, a plurality of positioning holes for receiving the latch member 4 are arranged in the surface gap of the first mold 1.

[0063] According to a preferred embodiment, the second mold 2 has a second molding surface in contact with the outer heat-proof material and a second mating surface in contact with other mold components (such as the bottom surface of the edge strip 3). Furthermore, a plurality of positioning holes for receiving the latch member 4 are arranged in the surface gap of the second mold 2.

[0064] According to a preferred embodiment, the edge strip 3 extends between the first mold 1 and the second mold 2. A plurality of edge strips 3 are connected to each other to connect and enclose the first mold 1 and the second mold 2. Further, the edge strip 3 has a third molding surface in contact with the external heat-proof material and a third mating surface in contact with other mold components (such as the first mold 1, the second mold 2 and / or at least another edge strip 3).

[0065] According to a preferred embodiment, in the present invention, the molding die may include, for example, five side strips 3. Specifically, two side strips 3 are positioned with the first die 1 (upper die) and the second die 2 (lower die) by pins. Furthermore, the remaining three side strips 3 are positioned by locking with the second die 2 (lower die) by the stopper 5 to avoid interference from too many pins.

[0066] According to a preferred embodiment, there is an interference fit between the pin and the mold (the first mold 1, the second mold 2).

[0067] According to a preferred embodiment, the pin is clearance-fitted. Specifically, the clearance of the pin is 0.03-0.3 mm. Preferably, the clearance of the pin is 0.07-0.2 mm.

[0068] According to a preferred embodiment, the effective working section of the pin should be maintained within 3 to 15 mm. Preferably, the effective working section of the pin should be 10 mm. More preferably, the effective working section of the pin should be 5 mm.

[0069] According to a preferred embodiment, the pin position accuracy should be less than ±0.1 mm.

[0070] According to a preferred embodiment, the specific operating steps of the molding mold provided by the present invention include: cleaning the mold - placing the lower mold - installing each side strip according to the marked order - installing the flange position side strips horizontally - pre-tightening the screws between the side strips - installing the upper mold - locking the entire mold.

[0071] According to a preferred embodiment, the specific use method of the molding mold of the present invention is explained by taking the preparation of a composite rigid thermal insulation component as an example.

[0072] Specifically, the composite rigid thermal insulation component usually includes a rigid fiber thermal insulation layer and a fiber fabric panel reinforcement layer. Furthermore, the composite rigid thermal insulation component is usually prepared by placing various prepared panel substrates in a molding tool, and then impregnating, drying and sintering. However, such composite thermal protection components formed by conventional molds usually do not have good curved surface forming accuracy, especially for some thermal protection components with complex surfaces.

[0073] According to a preferred embodiment, in the present invention, at least one layer of fiber fabric reinforced panel is first placed in the molding mold provided by the present invention, and the molding mold is bonded to the fiber fabric reinforced panel mold and each edge strip 3 and the lower mold (second mold 2) through the molding surface. Further, a rigid fiber insulation layer is placed on the fiber fabric reinforced panel and clamped with the fiber fabric reinforced panel through the molding surface. Thereafter, the upper mold (first mold 1) is installed and the entire mold is locked. The precursor of the primary thermal insulation component in the mold is impregnated by vacuum pressing, and after curing, it is subjected to low-temperature drying and high-temperature sintering. Specifically, the curing temperature for the precursor of the primary thermal insulation component is about 85°C. The low-temperature drying temperature is about 30°C to 70°C. The high-temperature sintering temperature is about 900°C to 1400°C.

[0074] According to a preferred embodiment, the preparation of the rigid fiber insulation layer can be to compound the fiber reinforcement with the aerogel precursor solution through sol-gel, aging, solvent replacement and supercritical drying processes to obtain a composite aerogel material. The surface of the composite aerogel material is treated with a treatment agent for anti-seepage and then dried to obtain the rigid fiber insulation layer. In particular, the concentration of the anti-seepage treatment agent is, for example, 15% to 50%.

[0075] According to a preferred embodiment, the upper mold (first mold 1) is opened, at least another layer of fiber fabric reinforced panel is placed on the thermal insulation component precursor, and the fiber fabric reinforced panel is clamped to the primary thermal insulation component precursor by fitting the molding mold with the molding surface. Thereafter, the upper mold (first mold 1) is installed, and the entire mold is locked. The secondary thermal insulation component precursor in the mold is impregnated with vacuum pressure, and after curing, it is low-temperature dried and high-temperature sintered. Specifically, compared with the primary thermal insulation component precursor, the curing temperature for the secondary thermal insulation component precursor is about 90°C. The low-temperature drying temperature for the secondary thermal insulation component precursor is about 40°C to 80°C. The high-temperature sintering temperature for the secondary thermal insulation component precursor is about 1000°C to 1500°C. In particular, compared with the primary treatment process, the secondary treatment further increases the processing temperature of the corresponding process, which is conducive to the solidification and forming of the composite thermal protection structure. In addition, under this treatment process, with the help of the tooling surface of the molding mold, especially the flanging position strips installed in the horizontal direction, the formed thermal protection structure can effectively form continuous flanging corners. Compared with the existing block flanging method, the flanging forming accuracy can be effectively guaranteed.

[0076] In some optional embodiments, the prepared fiber fabric reinforced panel-rigid fiber insulation layer-fiber fabric reinforced panel can be sequentially bonded and clamped in the mold through the tooling surface. After the upper mold (first mold 1) is installed and the entire mold is locked, the thermal insulation component precursor in the mold is impregnated by vacuum pressure, and after curing, it is dried at low temperature and sintered at high temperature.

[0077] According to a preferred embodiment, the curing temperature for the thermal insulation component precursor is about 70°C to 90°C. The low-temperature drying temperature for the thermal insulation component precursor is about 30°C to 80°C. The high-temperature sintering temperature for the thermal insulation component precursor is about 900°C to 1500°C. In some optional embodiments, the rigid fiber insulation layer and the fiber fabric reinforced panel can be combined by sewing fiber lines.

[0078] According to a preferred embodiment, the present invention adopts a method of near-net molding of an integrated molding mold to achieve integrated molding of the flanging area. By changing the mold design method, the molding accuracy of the flanging can be effectively guaranteed. The molding method of the flanging area in the present invention does not need to use foam glue or the like for compensation, and the molding problem of the flanging area can be solved by mold design, and the molding accuracy is high. Specifically, in the technical solution of the present invention, the flanging position is positioned by a stopper, and the upper and lower molds are positioned by pins. The flanging mold closing direction is perpendicular to the fiber laying direction, which can effectively solve the influence of the preform surface during the vertical mold closing process. At the same time, the mold closing directions on both sides of the flanging are at an angle of 90°, which can effectively form the flanging corner, ensuring that the position is consistent with the theoretical shape or there is a small amount of processing allowance, and there will be no problem of obvious negative difference in the position of the flanging corner due to the same direction mold closing.

[0079] According to a preferred embodiment, when designing a molding die, the following requirements generally need to be met:

[0080] (1) The mold surface should be smooth, flat, and free of cracks, and the thermal expansion coefficient of the mold material should be as small as possible to avoid deformation of the parts after molding;

[0081] (2) The rigidity and strength of the mold can withstand its own weight, the composite sandwich structure, and the total weight of the tooling to avoid deformation of the mold;

[0082] (3) The thermal conductivity and thermal uniformity of the mold are stable and good, meeting the heating and cooling requirements of the curing process to avoid thermal deformation of the mold;

[0083] (4) For combined assembled molds, demoulding must be easy.

[0084] Reference surface selection and forming mold processing accuracy

[0085] According to a preferred embodiment, in the mold forming process, the YZ reference plane 61, the XZ reference plane 62 and the matching surface need to be selected as the processing reference planes. Figure 2 Specifically, the YZ reference plane 61 is, for example, Figure 1 The XZ reference plane 62 is, for example, Figure 1 The front side of the molding die shown. The XY reference plane 63 is, for example, Figure 1 The bottom surface of the molding die is shown.

[0086] In some optional embodiments, the selected reference plane should preferably be conducive to the preparation, use and re-measurement of the mold.

[0087] According to a preferred embodiment, the flatness and verticality of the reference surface should be ≤0.07mm. Preferably, the flatness and verticality of the reference surface should be ≤0.05mm. On the other hand, the profile accuracy of the mold (first mold 1, second mold 2) should be less than ±0.2mm. Preferably, the profile accuracy of the mold (first mold 1, second mold 2) should be less than ±0.1mm.

[0088] Mould assembly and air tightness test

[0089] According to a preferred embodiment, the molding of the multi-curved sandwich structure outer heat protection material has high requirements on the air tightness of the mold, and it is necessary to ensure that no pores are generated inside the multi-curved sandwich structure outer heat protection material.

[0090] According to a preferred embodiment, the fit clearance should be less than 0.05 mm to meet the airtightness requirement, and the preferred fit clearance should be less than 0.03 mm. In some embodiments, under a pressure of 0.6 MPa to 0.9 MPa, it should be ensured that there is no pressure change within 20 to 60 minutes.

[0091] The present invention is further described below by way of examples, but these examples are only for illustrative purposes, and the protection scope of the present invention is not limited to these examples.

[0092] Example 1

[0093] According to a preferred embodiment, a multi-curved sandwich structure composite material is formed by a mold. In particular, in this embodiment, the mold material is selected as 45# steel. Further, the mold is composed of a first mold 1 (upper mold), a second mold 2 (lower mold) and four side strips 3.

[0094] Specifically, the YZ reference plane 61, the XZ reference plane 62 and the matching surface are selected as the reference planes for processing. The two side strips 3 are positioned between the first mold 1 (upper mold) and the second mold 2 (lower mold) by pins, one is to ensure the curved surface forming, and the other is to ensure the correct matching of the profiles between the first mold 1 (upper mold) and the second mold 2 (lower mold).

[0095] On the other hand, the remaining two side strips 3 are assembled by limiting the position through the limiting blocks 5 without using pins to avoid interference caused by too many pins.

[0096] Preferably, in this embodiment, the verticality of the reference plane is ≤0.03 mm. The surface processing accuracy of the mold (first mold 1, second mold 2) is ±0.05 mm. The position accuracy of the positioning pin is ≤0.07 mm.

[0097] According to a preferred embodiment, sealing grooves 7 are processed between the mating surfaces of the edge strips 3 and between the mating surfaces of the edge strips 3 and the mold (the first mold 1 and the second mold 2), and the sealing grooves 7 are used to ensure the airtightness of the mold.

[0098] According to a preferred embodiment, for the air tightness test of the mold, in this embodiment, the mold is under a pressure of 0.7 MPa and there is no pressure change within 30 minutes.

[0099] Example 2

[0100] According to a preferred embodiment, a multi-curved sandwich structure composite material is formed by a mold. In particular, in this embodiment, the material selected is 316L stainless steel. Further, the mold is composed of a first mold 1 (upper mold), a second mold 2 (lower mold) and 5 side strips.

[0101] Specifically, the YZ reference plane 61, the XZ reference plane 62 and the matching surface are selected as the reference planes for processing. The two side strips 3 are positioned between the first mold 1 (upper mold) and the second mold 2 (lower mold) by pins, one is to ensure the curved surface forming, and the other is to ensure the correct matching of the profiles between the first mold 1 (upper mold) and the second mold 2 (lower mold).

[0102] On the other hand, the remaining three side strips 3 are assembled by limiting the position of the limiting block 5 without using pins, so as to avoid interference caused by too many pins. Figure 2 As shown, a side strip 3 is positioned as a horizontal limit block to form a profile perpendicular to the large surface.

[0103] Preferably, in this embodiment, the flatness and verticality of the reference surface is ≤0.05 mm. The surface processing accuracy of the mold (the first mold 1 and the second mold 2) is ±0.10 mm. The position accuracy of the positioning pin is ≤0.10 mm.

[0104] According to a preferred embodiment, sealing grooves 7 are processed between the mating surfaces of the edge strips 3 and between the mating surfaces of the edge strips 3 and the mold (the first mold 1 and the second mold 2), and the sealing grooves 7 are used to ensure the airtightness of the mold.

[0105] According to a preferred embodiment, for the air tightness test of the mold, in this embodiment, the mold is under a pressure of 0.7 MPa and there is no pressure change within 30 minutes.

[0106] It should be noted that the above-mentioned specific embodiments are exemplary, and those skilled in the art can come up with various solutions inspired by the disclosure of the present invention, and these solutions also belong to the disclosure scope of the present invention and fall within the protection scope of the present invention. Those skilled in the art should understand that the present invention specification and its drawings are illustrative and do not constitute a limitation on the claims. The scope of protection of the present invention is defined by the claims and their equivalents. The present invention specification contains multiple inventive concepts, such as "preferably", "according to a preferred embodiment" or "optionally", all of which indicate that the corresponding paragraph discloses an independent concept, and the applicant reserves the right to file a divisional application based on each inventive concept.

Claims

1. A method for designing a molding die for a multi-curved sandwich structure external heat protection material, characterized in that: include: Select the molding mold material; Design molding die structure; Select the reference surface and set the processing accuracy of the forming mold; Assemble molds and test mold air tightness; Wherein, the molding die comprises: A first mold (1) having a first molding surface in contact with an external heat-resistant material, a positioning hole for plugging and fixing, and a first mating surface in contact with at least one mold component; A second mold (2) having a second molding surface in contact with the external heat-proof material, a positioning hole for plugging and fixing, and a second matching surface in contact with at least one mold component; and A plurality of side strips (3) extending between the first mold (1) and the second mold (2), and having a third molding surface in contact with the external heat-proof material, a positioning hole for plugging and fixing, and a third mating surface in contact with at least one mold component; Wherein, a plurality of the side strips (3) are connected to each other to connect and enclose the first mold (1) and the second mold (2); Wherein, the first mould (1), the second mould (2) and the plurality of side strips (3) are inserted and positioned via the positioning holes.

2. The method for designing a forming mold for a multi-curved sandwich structure outer heat protection material according to claim 1, characterized in that: The first mould (1), the second mould (2) and a plurality of the side strips (3) are connected and positioned by means of latch members (4) arranged in the positioning holes, and some of the side strips (3) are positioned by means of limit blocks (5).

3. The method for designing a forming mold for a multi-curved sandwich structure external heat protection material according to claim 2, characterized in that: The position accuracy of the latch member (4) is less than ±0.1 mm.

4. The method for designing a forming mold for a multi-curved sandwich structure external heat-resistant material according to claim 2 or 3, characterized in that: The latch member (4) and the first mould (1) and / or the second mould (2) are in an interference fit, and the latch member (4) and the positioning hole are in a small clearance fit.

5. The method for designing a forming mold for a multi-curved sandwich structure external heat protection material according to any one of claims 1 to 3, characterized in that: The steps for selecting the reference surface of the molding die include: Select the YZ reference plane (61), the XZ reference plane (62) and the mating surface as the reference planes for machining.

6. The method for designing a forming mold for a multi-curved sandwich structure outer heat protection material according to any one of claims 1 to 3, characterized in that: The flatness and verticality of the selected reference surface are ≤0.07mm, and the surface accuracy is less than ±0.2mm.

7. The method for designing a forming mold for a multi-curved sandwich structure external heat protection material according to any one of claims 1 to 3, characterized in that: The airtightness test for the molding die includes: Under the pressure condition of 0.6MPa to 0.9MPa, the molding die has no pressure change within 20 to 60 minutes.

8. A molding die used in the method for designing a molding die for a multi-curved sandwich structure external heat protection material according to any one of claims 1 to 7, characterized in that: include: A first mold (1) having a first molding surface in contact with an external heat-resistant material, a positioning hole for plugging and fixing, and a first mating surface in contact with at least one mold component; A second mold (2) having a second molding surface in contact with the external heat-proof material, a positioning hole for plugging and fixing, and a second matching surface in contact with at least one mold component; and A plurality of side strips (3) extending between the first mold (1) and the second mold (2), and having a third molding surface in contact with the external heat-proof material, a positioning hole for plugging and fixing, and a third mating surface in contact with at least one mold component, Wherein, the first mould (1), the second mould (2) and the plurality of side strips (3) are inserted and positioned via the positioning holes.

9. A method for forming a multi-curved sandwich structure outer heat-resistant material using the forming mold according to claim 8, characterized in that: include: placing a second mold (2); Installing at least one side strip (3) on the second mold (2) in a preset marking sequence, and pre-tightening it by means of a latch member (4); Placing each panel layer of the multi-curved sandwich structure outer heat-proof material in a forming mold according to a preset paving order, and fitting and clamping the panel layer with the forming mold at least through the edge strip profile of the forming mold; Installing the first mold (1) and locking the molding mold; The multi-curved sandwich structure precursor placed in the molding die is subjected to vacuum pressure impregnation, curing, drying and sintering to mold the multi-curved sandwich structure outer heat protection material through the molding die.

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