Ceramic 3D printing A sandwich structure with broadband wave transmission characteristic

Abstract

The invention relates to the technical field of aerospace, in particular to a ceramic 3D printing A sandwich structure with a broadband wave-transparent characteristic. According to the ceramic 3D printing A sandwich structure with the broadband wave transmission characteristic, good compatibility of broadband wave transmission, strength-structure accuracy and reliability is achieved, an obvious effect on broadband wave transmission of 1 GHz to 18 GHz is achieved, the dielectric constant and the tangent loss are in a reduction trend under the same frequency band, excellent stability is shown, and the dielectric constant and the tangent loss are reduced under 10 GHz. The dielectric constant of the ceramic 3D printing A sandwich structure with the broadband wave transmission characteristic is reduced by 40% or above compared with that of a full solid structure, the wave transmission rate is increased by 50% or above, the ceramic 3D printing A sandwich structure has excellent electromagnetic performance and mechanical performance, and support is provided for implementation of reliable service application targets such as diversion, heat protection, wave transmission, bearing and rain erosion resistance of hypersonic aircrafts.

Description

Technical Field

[0001] The present invention relates to the field of aerospace technology, and in particular to a ceramic 3D printed A sandwich structure with broadband wave transmission characteristics. Background Art

[0002] The radome is a key core component of an aerospace vehicle. It is located at the head of the vehicle and has multiple functions such as air diversion, heat protection, wave transmission, and load-bearing. It is mainly used to protect the normal operation of the aircraft's communication, telemetry, guidance, detonation and other systems under harsh environmental conditions.

[0003] In the aerospace industry, high requirements are placed on the structural accuracy and stability of radomes. For decades, the mainstream structure was a single-walled cone with a thickness of 4.00 mm to 6.00 mm. However, this structure suffered from insufficient comprehensive performance in electromagnetic, strength, and thermal shock resistance, failing to meet the requirements for high anti-electronic interference capabilities, broadband wave transmission, and upgraded three-proof performance indicators required for hypersonic operation.

[0004] To meet the demands of advanced technology, those skilled in the art have begun incorporating multi-scale structures into radomes. For example, composite structures such as porous, foam, and honeycomb structures are incorporated into the radome walls to broaden the wave transmission band. Among these, the A-sandwich structure, featuring a honeycomb core, offers excellent structural properties, including lightweight, high strength, and high wave transmission. In recent years, it has been widely used in aerospace, radar antennas, and other fields.

[0005] However, the A sandwich structure still faces many challenges in its actual production. First, its unique honeycomb core structure is complex to manufacture, requiring extremely high processing precision to ensure structural uniformity and consistency. Second, the A sandwich structure's faceplates and core layer must be firmly and evenly connected, but traditional bonding methods often struggle to achieve the desired results when faced with complex structural shapes and high precision requirements. Furthermore, the performance of adhesives can be affected by changes in ambient temperature and humidity, which can impact production quality and structural stability during service. Furthermore, A sandwich structures often involve the composite use of multiple materials, and issues such as differences in thermal expansion coefficients and mechanical property matching between these materials require thorough consideration and design.

[0006] Therefore, developing an A sandwich structure that is easy to produce, lightweight, high-strength, and has broadband wave transmission properties has important practical and strategic significance. Summary of the Invention

[0007] To address the technical problem of developing an A-sandwich structure that is easy to manufacture, lightweight, high-strength, and has broadband wave-transmitting properties, the present invention provides a ceramic 3D-printed A-sandwich structure with broadband wave-transmitting properties. The structure is integrally formed from ceramic material via 3D printing, overcoming the production bottleneck of A-sandwich structures in the prior art. From bottom to top, it includes outer skin, core layer and inner skin; The outer skin is a solid structure; The core layer is composed of a plurality of honeycomb units arranged in an array, and the honeycomb units penetrate the upper and lower surfaces of the core layer; The inner skin is a grid structure and is provided with a plurality of through holes penetrating the upper and lower surfaces of the inner skin, and the through holes are connected to the honeycomb units.

[0008] Furthermore, the thickness of the outer skin and the core layer is 0.20 mm to 1.50 mm; the thickness of the inner skin is 0.25 mm to 2.00 mm.

[0009] Furthermore, the physical volume of the inner skin is 94% to 102% of the top-secret volume of the outer skin.

[0010] Furthermore, the inscribed equivalent diameter of the honeycomb unit is 3 mm to 7 mm.

[0011] Furthermore, the thickness of the honeycomb unit side wall is 0.2 mm to 0.8 mm.

[0012] Furthermore, through slots are provided on the side walls of the honeycomb units to connect two adjacent honeycomb units. It should be noted that the total number of through slots on the six side walls of any honeycomb unit is 2 to 6.

[0013] Furthermore, the depth of the through groove is 50% to 100% of the thickness of the core layer.

[0014] Furthermore, the width of the through groove is 25% to 50% of the inscribed equivalent diameter of the honeycomb unit.

[0015] Furthermore, the through hole is a circular through hole or a round-end through hole.

[0016] Furthermore, when the through hole is a circular through hole, the diameter of the through hole is 1 mm to 3 mm; when the through hole is a round-end through hole, the longest length of the through hole is 2 mm to 5 mm, and the widest width is 0.8 mm to 2 mm.

[0017] In summary, compared with the prior art, the present invention has the following beneficial effects: The ceramic 3D-printed A sandwich structure with broadband wave transmission characteristics provided by the present invention can achieve good compatibility of broadband wave transmission, strength-structural precision and reliability, providing support for the realization of reliable service application goals such as guidance, heat protection, wave transmission, load-bearing, and rain erosion resistance in hypersonic aircraft; in addition, it overcomes the production and manufacturing difficulties of the A sandwich structure in the existing technology, and provides new ideas for the manufacture and design of complex sandwich structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 Schematic diagram of the structure of a ceramic 3D printed A sandwich structure resonant cavity unit with broadband wave transmission characteristics provided in Example 1 of the present invention; Figure 2 A half-section schematic diagram of a ceramic 3D printed A sandwich structure resonant cavity unit with broadband wave transmission characteristics provided in Example 1 of the present invention; Figure 3 A schematic cross-sectional view of a ceramic 3D printed A sandwich structure resonant cavity unit with broadband wave transmission characteristics provided in Example 1 of the present invention; Figure 4 Schematic diagram of the core structure of a resonant cavity unit with a 3D-printed ceramic sandwich structure A having broadband wave transmission characteristics provided in Example 1 of the present invention; Figure 5 A half-section schematic diagram of a ceramic 3D printed A sandwich structure resonant cavity unit with broadband wave transmission characteristics provided in Example 2 of the present invention; Figure 6 This is a schematic diagram of the double-layer structure resonant cavity unit structure provided in Comparative Example 1 of the present invention.

[0020] Reference numerals: 10-outer skin; 20-core layer; 21-honeycomb unit; 22-through groove; 30-inner skin; 31-through hole. DETAILED DESCRIPTION

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0022] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limiting the present invention.

[0023] Example 1 This embodiment provides a ceramic 3D printed A sandwich structure with broadband wave transmission characteristics, which is formed in one piece by 3D printing of ceramic material; Figure 1 The figure shows a resonant cavity unit of a ceramic 3D printed A sandwich structure with broadband wave transmission characteristics provided by this embodiment. Figure 2 is a half-section schematic diagram of the resonant cavity unit, Figure 3 1 is a schematic cross-sectional view of the resonant cavity unit, which includes, from bottom to top, an outer skin 10, a core layer 20 and an inner skin 30; The outer skin 10 is a solid structure; like Figure 4 As shown, the core layer 20 is composed of a plurality of honeycomb units 21 arranged in an array, and the honeycomb units 21 penetrate the upper and lower surfaces of the core layer 20; The inner skin 30 is a grid structure, and is provided with a plurality of through holes 31 penetrating the upper and lower surfaces of the inner skin 30 . The through holes 31 are connected to the honeycomb units 21 .

[0024] Specifically, when used to manufacture an aerospace aircraft radome, the outer skin 10 serves as the outermost structure of the radome, followed inward by the core layer 20 and the inner skin 30 .

[0025] During specific manufacturing, the through hole 31 can be used for discharge and cleaning; More specifically, during the 3D printing of ceramic materials, fine waste will be generated. In particular, during the printing process of the core layer 20 of the honeycomb structure, the nozzle moves frequently and the consistency is low, which makes it easier to generate powder debris. These debris will be lifted up with the movement of the nozzle or the change of airflow, affecting the subsequent printing effect. The through hole 31 connected to the honeycomb unit 21 can directly provide a short-range channel for the honeycomb unit 21, which is conducive to the timely discharge of these debris. At the same time, since the ceramic material itself is highly brittle, it is also easy to generate debris due to thermal stress or shrinkage during post-processing. The through hole 31 can provide an operating space when cleaning the sandwich structure A, allowing cleaning media such as ultrasonic bubbles or pulsed airflow to effectively penetrate into the core layer 20 for comprehensive cleaning. In addition, the through hole 31 also provides a stress buffer space. During the post-processing sintering, there are differences in the shrinkage amplitude between the various layers of structure. If the difference in shrinkage amplitude between the inner layer structure and the outer layer structure is too large, bulging, cracking or overall deformation is likely to occur. The design of the through hole 31 can effectively disperse the thermal stress of the inner layer structure to adapt to the changes in the shrinkage amplitude of the outer layer outer skin 10 due to heat, thereby reducing the bulging and cracking rate and ensuring the production quality.

[0026] In this embodiment, preferably, the thickness of the outer skin 10 and the core layer 20 is 1.00 mm; the thickness of the inner skin 30 is 1.32 mm; the solid volume of the inner skin 30 is (99±0.02)% of the top-secret volume of the outer skin 10; During specific manufacturing, the physical volume of the inner skin 30 is equivalent to the top-secret volume of the outer skin 10, and the ceramic content of the inner skin 30 and the outer skin 10 can be controlled to be equivalent. During the post-processing sintering process, the difference in thermal shrinkage between the inner layer structure and the outer layer structure can be reduced, and a finished product structure with a more uniform and flat surface structure and smaller dimensional deviation can be obtained.

[0027] In this embodiment, preferably, the inscribed equivalent diameter of the honeycomb unit 21 is 5 mm, and the side wall thickness is 0.5 mm.

[0028] In this embodiment, a through groove 22 is provided on the side wall of the honeycomb unit 21 to connect two adjacent honeycomb units 21. Preferably, the depth of the through groove 22 is 50% of the thickness of the core layer 20, and the width is 50% of the inscribed equivalent diameter of the honeycomb unit 21. The total number of through grooves 22 on the six side walls of any honeycomb unit 21 is 2, and they are respectively located on two opposite side walls. During specific manufacturing, the design of the through groove 22 is conducive to the communication and discharge of printing debris. During the cleaning stage, it can also serve as a guide groove for the cleaning liquid, promoting the rapid discharge of residual liquid after cleaning.

[0029] In this embodiment, preferably, the through hole 31 is a round-end through hole with a longest length of 4.5 mm and a widest width of 1.5 mm. Any of the through holes 31 is connected to one honeycomb unit 21 .

[0030] Example 2 This embodiment provides a ceramic 3D printed A sandwich structure with broadband wave transmission characteristics, which is integrally formed from ceramic materials through 3D printing. The difference from the embodiment 1 of the present invention is that: In this embodiment, if Figure 5As shown, the depth of the through groove 22 is 100% of the thickness of the core layer 20, and the groove width is 25% of the inscribed equivalent diameter of the honeycomb unit 21. The total number of through grooves 22 on the six side walls of any honeycomb unit 21 is 6, which are evenly distributed on the six side walls. In this implementation, if Figure 5 As shown, the through hole 31 is a circular through hole with a diameter of 1.64 mm. Any of the through holes 31 is connected to one or three honeycomb units 21; The rest of the structural design, dimensional parameters, material selection and manufacturing process are consistent with those of Example 1 of the present invention.

[0031] Example 3 This embodiment provides a ceramic 3D printed A sandwich structure with broadband wave transmission characteristics, which is integrally formed from ceramic materials through 3D printing. The difference from the embodiment 1 of the present invention is that: In this embodiment, the thickness of the outer skin 10 and the core layer 20 is 0.80 mm; the thickness of the inner skin 30 is 1.06 mm, and the solid volume of the inner skin 30 is (99±0.02)% of the top-secret volume of the outer skin 10; In this embodiment, the side wall thickness of the honeycomb unit 21 is 0.4 mm; The rest of the structural design, dimensional parameters, material selection and manufacturing process are consistent with those of Example 1 of the present invention.

[0032] The present invention also provides the following comparative examples 1 and 2.

[0033] Comparative Example 1 This comparative example provides a double-layer structure, such as Figure 6 As shown, it includes an outer skin 10 and a core layer 20. The difference from Example 1 of the present invention is that it does not include an inner skin 30; the rest of the structural design, dimensional parameters, material selection and manufacturing process are consistent with Example 1 of the present invention.

[0034] Comparative Example 2 This comparative example provides a sandwich structure A in the form of injection-bonding, comprising an outer skin and an inner skin made of a quartz / epoxy resin composite material, and a foam core layer composed of PMI foam; During the specific manufacturing process, the inner and outer skins are formed by the hand lay-up process to obtain the inner and outer skin structural layers with rectangular wave-transparent windows after relative assembly. The core layer is formed by adding and foaming PMI foam, and the various structural layers are connected and fixed by epoxy adhesive; the thickness of the inner and outer skins is 3 mm, and the thickness of the core layer is 1 mm.

[0035] The resonant cavity units obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were tested for electromagnetic and mechanical properties, and the test results are summarized in Table 1.

[0036] Table 1 Summary of test results of electromagnetic and mechanical properties of sandwich structure resonant cavity unit A

[0037] According to the data in Table 1, the ceramic 3D-printed A sandwich structure provided by Examples 1-3 of the present invention meets and exceeds the technical indicators in terms of electromagnetic and mechanical properties, and has a significant effect on broadband wave transmission from 1 GHz to 18 GHz. In the same frequency band, the dielectric constant and tangent loss of Examples 1-3 show a decreasing trend, and the dielectric constant phase change rate is small, demonstrating excellent dielectric constant stability. In particular, at 10 GHz, the dielectric constant of the ceramic 3D-printed A sandwich structure is reduced by more than 40% compared to the fully solid structure, and the wave transmittance is increased by more than 50%.

[0038] Comparative Example 1 is a double-layer structure that does not include an inner skin layer with a grid structure. It is slightly insufficient in broadband wave transmission and mechanical properties. In addition, more significantly, its dielectric constant is not as stable as that of Examples 1 to 3 with a grid structure. It can be seen that the double-layer structure produced in Comparative Example 1, even though it has a honeycomb structure, improves key indicators such as wave transmission performance to a certain extent, but its electromagnetic performance stability and mechanical performance are not as good as the ceramic 3D printed A sandwich structure with a grid inner skin.

[0039] Comparative Example 2 was manufactured using the mainstream manufacturing process of sandwich structure A in the prior art. However, it can be seen that its electromagnetic and mechanical properties are relatively poor. In addition, due to the inherent defects of the process, this method is difficult to manufacture and process, and it is also more difficult to achieve further improved design and implementation of thin-walled structures.

[0040] Although terms such as A sandwich structure, outer skin, core layer, inner skin, solid structure, grid structure, honeycomb unit, sidewall, through hole, through slot, circular through hole, round-end through hole, radome, short-range channel, ultrasonic bubble, pulsed airflow, cleaning medium, contraction amplitude, guide groove, inner layer structure, outer layer structure, resonant cavity, broadband wave transmission characteristics, wave transmission frequency, wave transmittance, dielectric constant, tangent loss, bending strength, tensile strength, compressive strength, bending modulus of elasticity, electromagnetic properties, and mechanical properties are frequently used herein, the use of other terms is not excluded. These terms are used merely to more conveniently describe and explain the essence of the present invention; interpreting them as any additional limitations is contrary to the spirit of the present invention.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A ceramic 3D printed A sandwich structure with broadband wave transmission characteristics, characterized by: Made of ceramic material through 3D printing; From bottom to top, it includes an outer skin (10), a core layer (20) and an inner skin (30); The outer skin (10) is a solid structure; The core layer (20) is composed of a plurality of honeycomb units (21) arranged in an array, and the honeycomb units (21) penetrate the upper and lower surfaces of the core layer (20); The inner skin (30) is a grid structure and is provided with a plurality of through holes (31) penetrating the upper and lower surfaces of the inner skin (30), and the through holes (31) are connected to the honeycomb units (21).

2. The ceramic 3D printed A sandwich structure with broadband wave transmission characteristics according to claim 1, characterized in that: The thickness of the outer skin (10) and the core layer (20) is 0.20 mm to 1.50 mm; The thickness of the inner skin (30) is 0.25 mm to 2.00 mm.

3. The ceramic 3D printed A sandwich structure with broadband wave transmission characteristics according to claim 2, characterized in that: The solid volume of the inner skin (30) is 94% to 102% of the top-secret volume of the outer skin (10).

4. The ceramic 3D printed A sandwich structure with broadband wave transmission characteristics according to claim 3, characterized in that: The inscribed equivalent diameter of the honeycomb unit (21) is 3 mm to 7 mm.

5. The ceramic 3D printed A sandwich structure with broadband wave transmission characteristics according to claim 4, characterized in that: The side wall thickness of the honeycomb unit (21) is 0.2 mm to 0.8 mm.

6. The ceramic 3D printed A sandwich structure with broadband wave transmission characteristics according to claim 5, characterized in that: A through groove (22) is provided on the side wall of the honeycomb unit (21) so that two adjacent honeycomb units (21) are connected.

7. The ceramic 3D printed A sandwich structure with broadband wave transmission characteristics according to claim 6, characterized in that: The depth of the through groove (22) is 50% to 100% of the thickness of the core layer (20).

8. The ceramic 3D printed A sandwich structure with broadband wave transmission characteristics according to claim 7, characterized in that: The width of the through groove (22) is 25% to 50% of the inscribed equivalent diameter of the honeycomb unit (21).

9. The ceramic 3D printed A sandwich structure with broadband wave transmission characteristics according to claim 8, characterized in that: The through hole (31) is a circular through hole or a round-end through hole.

10. The ceramic 3D printed A sandwich structure with broadband wave transmission characteristics according to claim 9, characterized in that: When the through hole (31) is a circular through hole, the diameter of the through hole (31) is 1 mm to 3 mm; When the through hole (31) is a round-end through hole, the longest length of the through hole (31) is 2 mm to 5 mm, and the widest width is 0.8 mm to 2 mm.

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