Satellite oversize composite grid structure forming method

Abstract

The application discloses a satellite super-large-size composite material grid structure forming method, which comprises the following steps: preparing a combined layering mold; connecting the combined layering mold with a support tool; preparing a unidirectional fiber cloth roll; cutting the unidirectional fiber cloth roll into pre-impregnated narrow strips with a preset width; using the combined layering mold and a special support to lay up the pre-impregnated narrow strips with the preset width into a shaped product blank; performing normal-temperature pre-pressing treatment on the product blank; and adopting hot-press tank curing forming on the product blank after the normal-temperature pre-pressing treatment, so that the satellite super-large-size composite material grid structure is obtained after demolding. The application solves the problem of overall forming of a cylindrical grid structure with super-large size, fixed grid geometric parameters and multiple types of rib strips.

Description

Technical Field

[0001] This invention belongs to the field of carbon fiber reinforced resin matrix composite material structure manufacturing technology, and particularly relates to a method for forming ultra-large-size composite material grid structure for satellites. Background Technology

[0002] To meet the dimensional requirements of the large optical remote sensing camera's light shield, a corresponding support structure is needed, with an outer envelope of Φ4280 (inner diameter) × 5371 (height) × 12 (wall thickness) mm, satisfying the requirements for lightweighting and stability. Traditional metal support structures have long development cycles and low yield rates, failing to meet the lightweighting requirements under ultra-large size conditions. Meanwhile, commonly used composite material structures such as skin-reinforced structures, honeycomb sandwich structures, and truss structures cannot simultaneously meet the needs for lightweighting and high stability. Summary of the Invention

[0003] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a method for forming ultra-large-sized composite material mesh structures for satellites, which solves the problem of integral forming of ultra-large-sized cylindrical mesh structures with fixed mesh geometric parameters and multiple types of ribs.

[0004] The objective of this invention is achieved through the following technical solution: a method for molding a satellite ultra-large composite material mesh structure, comprising: preparing a combined layup mold; preparing a support fixture and connecting the combined layup mold to the support fixture; preparing a unidirectional fiber roll and cutting the unidirectional fiber roll into prepreg narrow strips of a preset width; using the combined layup mold and a special support, laying the prepreg narrow strips of the preset width to form a product blank; performing room temperature pre-pressing treatment on the product blank; and curing the prepreg blank after room temperature pre-pressing treatment in an autoclave, and obtaining a satellite ultra-large composite material mesh structure after demolding.

[0005] In the above-mentioned method for forming ultra-large-size composite material grid structures for satellites, the combined layup mold includes a main mold, a forming soft mold, and a spacer block; wherein, the forming soft mold is disposed on the outer surface of the main mold through the spacer block; the main mold includes a core mold and a mandrel; wherein, the mandrel is disposed at the central axis position of the core mold, one end of the mandrel is connected to a support fixture, and the other end of the mandrel is connected to the support fixture.

[0006] In the above-mentioned method for forming ultra-large-sized composite material grid structures for satellites, the core mold is a cylinder, and the inner wall of the core mold is provided with reinforcing ring plates and longitudinal ribs.

[0007] In the above-mentioned method for forming ultra-large-size composite material grid structures for satellites, the mandrel includes a hollow shaft, a first connecting shaft, and a second connecting shaft; wherein, the first connecting shaft, the hollow shaft, and the second connecting shaft are connected in sequence; one end of the first connecting shaft is connected to the middle of one side wall of the mandrel, and the other end of the first connecting shaft is connected to a support fixture; one end of the second connecting shaft is connected to the middle of another side wall of the mandrel, and the other end of the second connecting shaft is connected to the support fixture.

[0008] In the above-mentioned method for forming ultra-large composite material grid structures for satellites, the forming soft mold is obtained by pouring silicone rubber into a flat mold and curing it at room temperature; the outer surface of the forming soft mold is provided with slits.

[0009] In the above-mentioned method for forming ultra-large-size composite material grid structure of satellite, the support fixture includes a special support, a first rotating device assembly, and a second rotating device assembly; wherein, the first rotating device assembly and the second rotating device assembly are disposed at both ends of the special support; the other end of the first connecting shaft is connected to the first rotating device assembly; and the other end of the second connecting shaft is connected to the second rotating device assembly.

[0010] In the above-mentioned method for forming ultra-large-size composite material grid structures for satellites, the first rotating device assembly and the second rotating device assembly have the same structure, both including a motor, a reducer, a gear, and a bearing; wherein, the motor is mounted on the dedicated bracket, and the output shaft of the motor is connected to the gear through the reducer; the gear is connected to the first connecting shaft or the second connecting shaft; the bearing is mounted on the dedicated bracket, and the bearing is connected to the other end of the first connecting shaft or the other end of the second connecting shaft.

[0011] In the above-mentioned method for forming ultra-large-sized composite material grid structures for satellites, during the layup process, a pre-impregnated narrow strip of preset width is placed on the upper part of the rib blank within the slit of the forming soft mold.

[0012] In the above-mentioned method for forming ultra-large composite material grid structures for satellites, the product blank is vacuumed during the room temperature pre-compression process.

[0013] In the above-mentioned method for forming ultra-large composite material grid structures for satellites, during curing, the highest temperature is 160℃ and the holding time is 3 hours under vacuum, and the highest external pressure is 0.4MPa.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] This invention solves the problem of integral molding of cylindrical mesh structures with ultra-large size, fixed mesh geometric parameters, and multiple types of ribs, ensuring both the overall shape accuracy and the accuracy of individual meshes. Attached Figure Description

[0016] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0017] Figure 1 This is a schematic diagram of the ultra-large composite material mesh structure provided in an embodiment of the present invention;

[0018] Figure 2 This is a schematic diagram of the main mold provided in an embodiment of the present invention;

[0019] Figure 3 This is a schematic diagram of the flat casting mold (excluding the cover plate) for rib forming mold provided in an embodiment of the present invention;

[0020] Figure 4 This is a schematic diagram showing the connection relationship between the molding soft mold, the occupant block, and the core mold provided in an embodiment of the present invention;

[0021] Figure 5 This is a schematic diagram of a placeholder block provided in an embodiment of the present invention;

[0022] Figure 6 This is a schematic diagram of the working state of the bracket tooling provided in an embodiment of the present invention;

[0023] Figure 7 This is a schematic diagram of the product's pre-compression and pre-curing packaging state provided in an embodiment of the present invention;

[0024] Figure 8 This is a schematic diagram of the curing process provided in an embodiment of the present invention. Detailed Implementation

[0025] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] The composite material grid structure is a hollow structure based on unidirectional composite material ribs. It features lightweight, strong damage resistance, high directional load-bearing capacity, and easy expansion of repeatable grid patterns, which fully meets the requirements of the camera lens hood support structure.

[0027] like Figure 1 As shown, the ultra-large composite material mesh structure is integrally cured from carbon fiber / epoxy resin prepreg narrow strips, with an inner diameter of [missing information]. The height is 5371 mm, and the rib thickness is 12 mm. This grid structure has 36 pairs of diagonal ribs, 12 rings of circumferential ribs, and 2 rings of end frames. The angle between the diagonal ribs and the generatrix is ​​24.4°. The width of the diagonal and circumferential ribs is 6 mm, and the width of the ribs at the end frames is 24 mm. This grid structure is an ultra-large-sized thin-walled configuration with specified grid geometry parameters and includes multiple types of ribs, making it difficult to guarantee the quality of co-curing.

[0028] This embodiment provides a method for forming ultra-large-size composite material mesh structures for satellites, which includes the following steps:

[0029] Preparation of combined layup molds;

[0030] Prepare the scaffold tooling and connect the combined layup mold to the scaffold tooling;

[0031] Prepare unidirectional fiber rolls and cut the unidirectional fiber rolls into prepreg narrow strips of a predetermined width;

[0032] Using a combination layup mold and a special support, prepreg narrow strips of a preset width are laid up to form product blanks;

[0033] The product blanks are pre-pressed at room temperature;

[0034] The preforms after room temperature pre-compression are cured and molded in an autoclave, and after demolding, a satellite-sized composite material mesh structure is obtained.

[0035] During the room temperature pre-compression treatment of the product blank, the product blank is vacuum-sealed. Specifically, when laying several layers, two room temperature vacuum compaction treatments are performed. The treatment steps are as follows: Figure 7 As shown, vacuum bags, sealing strips, and other auxiliary materials are wrapped in sequence to seal the blank into a vacuum system. After evacuating to 0.01 MPa, the blank is left to stand at room temperature and pressurized for 12 hours. Then, the vacuum is stopped and the auxiliary materials are removed.

[0036] This embodiment combines prepreg narrow strip layup, room temperature pre-pressing, and adaptive adjustment of curing parameters. Finally, the formed grid structure is removed from the mold as an independent unit, which not only ensures the overall shape accuracy but also achieves the accuracy of individual grids.

[0037] This embodiment designs a combined hard-inner and soft-outer layup mold, comprising two types: a main mold and a forming soft mold. The main mold is a cylindrical core mold with mandrels at both ends for easy load-bearing. The cylindrical core mold is made of aluminum to reduce its weight, while the mandrels are made of steel to enhance support rigidity. Considering the thermal expansion and deformation of the mold material, the core mold's shape is proportionally reduced to the product's outer diameter. The forming soft mold uses a thermally expandable material, selecting a suitable grade of silicone rubber, which is cast into a flat sheet at room temperature and then wound around the outer surface of the core mold. The rib forming mold has slits on its outer surface, serving as channels for the ribs to form. To balance the weight and tear resistance of the silicone rubber, it is segmented. To maintain the grid geometry parameters and reduce the amount of silicone rubber used and its weight, several aluminum spacer blocks are placed between the slits of the rib forming mold, using these spacer blocks to fix the forming soft mold to the outer surface of the core mold.

[0038] During layer layup, the mold lies horizontally on a dedicated support along its axis. A power unit is installed to drive the main mold to rotate. This power unit is detachable for easy inspection and maintenance, and also provides convenient individual protection during transport.

[0039] Prepare carbon fiber / epoxy resin prepreg narrow strips in advance. Use a two-step method to prepare unidirectional fiber rolls, requiring a single-layer thickness of 0.2 mm and a resin content of no less than 38%. Use a slitting machine to process the prepreg into unidirectional narrow strips with corresponding rib width specifications, ensuring that the length of a single roll is no less than 25 m.

[0040] After the layup mold is assembled, prepreg narrow tape is used to lay up the product, a total of 60 layers. First, the spiral reinforcement strips are laid, then the ring reinforcement strips are laid, and then the end frames are laid, overlapping at the joints. This process is repeated until the thickness requirement is met.

[0041] When laying the 30th and 60th layers, two vacuum compaction processes are performed at room temperature. The process is as follows: Vacuum bags, sealing strips, and other auxiliary materials are wrapped in sequence to seal the blank into a vacuum system. After vacuuming to 0.01 MPa, the blank is left to stand at room temperature and pressurized for 12 hours. Then, the vacuum is stopped and the auxiliary materials are removed.

[0042] The product blank is cured using an autoclave. A perforated release film, felt, vacuum bag film, and sealing strips are sequentially wrapped to encapsulate the blank and molding die assembly. The assembly is then placed in the autoclave, where it is vacuumed, heated, and pressurized for curing.

[0043] After the product has cured, remove the vacuum bag film and other packaging materials, remove one end of the mandrel, rotate the mandrel 90° from horizontal to vertical, place it on the ground, remove all the screws connecting the mandrel to the spacer blocks, take out the spacer blocks, cut off the rib forming mold, use slings to hold the product, and move the product out of the mandrel along the axial direction.

[0044] After the resin has been removed, the outer surface of the product is sanded to remove excess resin.

[0045] Research and development such as Figure 1 The large-scale composite material mesh structure shown was first designed with a modular molding die based on the product's shape. This die consists of a main mold on the inner side, a flexible molding die on the outer side, and an aluminum spacer block in the middle, achieving overall molding and demolding of the mesh structure. The ribs are thermo-pressed using a combination of molds. The flexible molding die is mounted on the outer surface of the main mold via the spacer block. The main mold includes a core mold 1 and a mandrel 2. The mandrel 2 is located at the central axis of the core mold 1, with one end connected to a support fixture and the other end also connected to the support fixture.

[0046] The main mold structure is as follows Figure 2 As shown, it mainly consists of a core mold 1 and a mandrel 2, which are fastened together with screws. The core mold 1 is made of aluminum alloy and is thin-walled. Reinforcing ring plates and longitudinal ribs are welded to the inner wall, which can ensure a certain rigidity while reducing its own weight, reducing its own deformation when lying horizontally, and helping to ensure the shape of the grid structure.

[0047] like Figure 2 As shown, the mandrel 2 includes a hollow shaft, a first connecting shaft, and a second connecting shaft; wherein, the first connecting shaft, the hollow shaft, and the second connecting shaft are connected in sequence; one end of the first connecting shaft is connected to the middle of one side wall of the mandrel 1, and the other end of the first connecting shaft is connected to the bracket fixture; one end of the second connecting shaft is connected to the middle of the other side wall of the mandrel 1, and the other end of the second connecting shaft is connected to the bracket fixture.

[0048] The mandrel 2 has a three-section structure. The section that passes through the center of the entire mandrel is a hollow aluminum shaft with a lightening hole to further reduce the deformation of the mandrel. The two sides are two solid steel connecting shafts used to support the main body mold.

[0049] The molding soft mold is made by pouring silicone rubber into a flat mold, curing it at room temperature, and then winding it around the outer surface of the core mold. The base plate of the molding soft mold is 15mm thick and has narrow slits on its surface, which are channels for forming the ribs, with a depth of 20mm. The intersections of the slits have R5 rounded corners, which effectively increases the area at the rib joints and helps to reduce step differences. To balance the weight of the silicone rubber and its tear resistance, the molding soft mold is divided into 18 pieces according to the product shape.

[0050] Figure 3 This is one of the flat mold structures, mainly composed of a body 41, a stop block 42, and a cover plate. The body is made of aluminum alloy, and the internal cavities are complementary to the forming soft mold when inverted, ensuring that the bottom surface of the forming soft mold and the forming surface of the ribs are flat.

[0051] The spacer blocks are located between the slits of the molding soft mold, and these spacer blocks fix the molding soft mold to the outer surface of the core mold 2, such as... Figure 4As shown, the placeholder block 51 is fastened to the outer surface of the core mold 1 via the base plate of the forming soft mold 52 and mounting screws 53. The appearance of the placeholder block is as follows. Figure 5 As shown, the inner side is designed with a lightening groove, and the connection hole between the core mold and the core mold is designed as a combination of round holes and oblong holes. During the layup, the placeholder block is placed in place and fixed with two screws to ensure the grid geometry. Before curing, the screws at the round holes are removed and the screws at the oblong holes are loosened to accommodate the axial deformation of the core mold.

[0052] The total weight of the molding die is controlled below 13t, which reduces its own weight and facilitates hoisting, transportation and flipping.

[0053] A dedicated support frame is designed according to the dimensions of the molding die. It can accommodate the flat-lying molding die and has a rotation function to facilitate the stacking process. The support fixture operates as follows: Figure 6 As shown, the bracket fixture includes a special bracket 22, a first rotating device assembly, and a second rotating device assembly; wherein, the first rotating device assembly and the second rotating device assembly are disposed at both ends of the special bracket 22; the other end of the first connecting shaft is connected to the first rotating device assembly; and the other end of the second connecting shaft is connected to the second rotating device assembly.

[0054] The first and second rotating device assemblies have the same structure, both including a motor, a reducer, a gear, and a bearing 26. The motor is mounted on a dedicated bracket 22, and its output shaft is connected to the gear via the reducer. The gear is connected to the other end of either the first or second connecting shaft. The bearing 26 is also mounted on the dedicated bracket 22 and is connected to the other end of either the first or second connecting shaft. It should be understood that... Figure 7 The motor, reducer, and gears are not shown in the drawing.

[0055] The modular lay-up mold 21 is placed flat on a dedicated support 22, and the mold rotates using a motor, reducer, gear bearings 26, etc. The motor has excellent load-bearing capacity, and the mold's rotation speed can be stably controlled at 0.2 r / min.

[0056] Pre-prepared carbon fiber / epoxy resin narrow strips are prepared in advance and then laid in the narrow slots of the above-mentioned layup mold.

[0057] To ensure the blank adheres to the mold and reduce air ingress into the layers, two room-temperature vacuum compaction processes are performed when laying the 30th and 60th layers.

[0058] Before pre-pressing and curing, a narrow silicone strip is prepared using the same silicone rubber material as the molded soft mold. This strip is 0.5mm wider than the slits in the soft mold to fully seal the product area, preventing adhesive overflow during curing and ensuring the product is not fully sealed. The strip remains at least 2mm higher than the surrounding molded soft mold after pressurization, effectively transferring pressure to the product. The encapsulation state is as follows: Figure 7 As shown, the molding soft mold 52 surrounds the main mold 71. The rib blank 73 to be molded is located in the slit of the molding soft mold 52. The silicone pre-impregnated narrow strip 74 is inserted above the rib blank 73, and then the perforated isolation film 75, the breathable felt 76, the vacuum bag film 77 and other auxiliary materials are placed in sequence.

[0059] The product and mold assembly is cured in an autoclave. A vacuum is applied before heating, and the maximum temperature is 160℃ for 3 hours, with a maximum external pressure of 0.4 MPa. After the heat treatment, the vacuum is immediately stopped, the external pressure is released, and then the temperature is lowered. The curing regime curve is as follows: Figure 8 As shown.

[0060] Once the mold temperature has dropped to 40°C, remove the assembly from the curing platform and dismantle most of the spacer blocks, soft mold, and one end of the mandrel. Rotate the assembly 90° and stand it upright in a suitable position. Remove the remaining spacer blocks and soft mold, and use an overhead crane and slings to remove the product from the core mold. Finally, remove any excess adhesive from the product surface.

[0061] The resulting product's external dimensions meet the design requirements, and its inner diameter roundness is [value missing]. The step difference at the joint of the reinforcing bar shall not exceed 0.6 mm.

[0062] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for forming a satellite ultra-large composite material grid structure, characterized in that... include: Preparation of combined layup molds; Prepare the scaffold tooling and connect the combined layup mold to the scaffold tooling; Prepare unidirectional fiber rolls and cut the unidirectional fiber rolls into prepreg narrow strips of a predetermined width; Using a combination layup mold and a special support, prepreg narrow strips of a preset width are laid up to form product blanks; The product blanks are pre-pressed at room temperature; The preforms after room temperature pre-compression are cured and molded in an autoclave, and after demolding, a satellite-sized composite material mesh structure is obtained; The combined layup mold includes a main mold, a forming soft mold, and a placeholder block; wherein... The molding soft mold is disposed on the outer surface of the main mold via the occupant block; The main mold includes a core mold (1) and a mandrel (2); wherein, the mandrel (2) is located at the central axis of the core mold (1), one end of the mandrel (2) is connected to the support fixture, and the other end of the mandrel (2) is connected to the support fixture; The spacer block is set in the slit on the outer surface of the rib forming mold of the forming soft mold, and the spacer block itself has a structure with a lightening groove and a round hole on its inner side.

2. The method for forming a satellite ultra-large-size composite material grid structure according to claim 1, characterized in that: The core mold (1) is a cylinder, and the inner wall of the core mold (1) is provided with a reinforcing ring plate and longitudinal ribs.

3. The method for forming a satellite ultra-large-size composite material grid structure according to claim 1, characterized in that: The mandrel (2) includes a hollow shaft, a first connecting shaft, and a second connecting shaft; wherein, The first connecting shaft, the hollow shaft, and the second connecting shaft are connected in sequence; One end of the first connecting shaft is connected to the middle of one side wall of the core mold (1), and the other end of the first connecting shaft is connected to the bracket tooling; One end of the second connecting shaft is connected to the middle of the other side wall of the core mold (1), and the other end of the second connecting shaft is connected to the bracket tooling.

4. The method for forming a satellite ultra-large-size composite material grid structure according to claim 1, characterized in that: The molding soft mold is obtained by pouring silicone rubber into a flat mold and curing it at room temperature; the outer surface of the molding soft mold is provided with slits.

5. The method for forming a satellite ultra-large-size composite material grid structure according to claim 3, characterized in that: The bracket fixture includes a dedicated bracket (22), a first rotating device assembly, and a second rotating device assembly; wherein... The first rotating device assembly and the second rotating device assembly are disposed at both ends of the special bracket (22); The other end of the first connecting shaft is connected to the first rotating device assembly; The other end of the second connecting shaft is connected to the second rotating device assembly.

6. The method for forming a satellite ultra-large-size composite material grid structure according to claim 5, characterized in that: The first rotating device assembly and the second rotating device assembly have the same structure, both including a motor, a reducer, gears, and bearings (26); wherein, The motor is mounted on the dedicated bracket (22), and the output shaft of the motor is connected to the gear through the reducer; the gear is connected to the first connecting shaft or the second connecting shaft; The bearing (26) is mounted on the special bracket (22) and is connected to the other end of the first connecting shaft or the other end of the second connecting shaft.

7. The method for forming a satellite ultra-large-size composite material grid structure according to claim 4, characterized in that: During the layup process, a prepreg narrow strip of preset width is placed on the upper part of the rib blank (73) within the slit of the forming soft mold.

8. The method for forming a satellite ultra-large-size composite material grid structure according to claim 4, characterized in that: During the room temperature pre-pressing process, the product blank is vacuumed.

9. The method for forming a satellite ultra-large-size composite material grid structure according to claim 1, characterized in that: During curing and molding, the maximum temperature is 160℃ and the holding time is 3 hours under vacuum, and the maximum external pressure is 0.4MPa.

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