U-shaped antenna housing 2.5 D braided preform

Abstract

The invention belongs to the field of new materials, relates to the field of fiber preforms, and particularly provides a 2.5 D woven preform of a U-shaped radome, which adopts the 2.5 D woven preform with excellent interlayer strength as a composite radome reinforcement. The reinforcement body is prepared by integrally sewing the 2.5 D laminated woven main prefabricated body and the 2.5 D laminated sewn secondary prefabricated body through a three-dimensional sewing process, and has the characteristics of high fiber volume content, high surface precision and low manufacturing cost; the antenna housing 2.5 D braided preform / aryne composite material prepared from the material has the advantages of high interlayer strength, good dielectric property, outstanding high temperature resistance and the like, and is particularly suitable for the requirements of high-temperature, high-overload and near-net-size formed composite material wave-transparent antenna housing.

Description

Technical Field

[0001] The present invention belongs to the field of new materials and more particularly to the field of fiber preforms, and specifically provides a U-shaped antenna cover 2.5D braided preform. Background Art

[0002] Traditional composite radomes are generally manufactured using a layup / molding process or a layup / autoclave process. When using the layup / molding process to manufacture composite radomes, material accumulation is prone to occur, resulting in the formation of diaphragms, resulting in loose pressurization of the radome, high porosity, and poor interlayer forces. When using a high-temperature autoclave molding process to manufacture radomes, mold and tooling investment is large, the molding cycle is long, high-temperature auxiliary materials are severely wasted, and wrinkles are prone to appear on the outer surface of the radome. After processing, the moisture absorption rate of the composite material increases due to the exposure of quartz fibers, seriously affecting the dielectric properties of the radome. For larger U-shaped composite radomes manufactured using the layup / molding process or the layup / autoclave process, the molding difficulty is further increased due to the irregular changes in their external dimensions. Common defects such as loose molding, cracking between layers due to lack of glue, and large-scale wrinkles are more likely to occur in parts of the radome.

[0003] 2.5D braided preform technology is a key branch of 3D braided preform technology. 2.5D braided preforms feature interlocking fibers along the thickness of the preform, resulting in excellent interlaminar strength and near-net-size molding. Using a 2.5D braided / RTM process instead of a layup / molding or layup / autoclave process to produce a U-shaped composite radome significantly improves the radome's uniformity and overall structural strength, resulting in a smooth, wrinkle-free surface and no defects such as adhesive defects or cracks.

[0004] Gao Longfei et al. ("Preparation and Properties of Quartz Fiber-Reinforced Boron Nitride Ceramic Matrix Composites," Composite Materials Science and Engineering, Issue 10, October 2020) fabricated a 2.5D quartz fiber preform-reinforced boron nitride ceramic composite using borazine as a boron nitride ceramic precursor and a 2.5D quartz fiber preform as reinforcement. Their research demonstrated that this composite possesses excellent mechanical and dielectric properties, making it suitable for use in wave-transparent radomes. However, this approach remains at the material research stage, and the production of ceramic-based radomes is complex and costly, making engineering applications a significant step forward.

[0005] CN113045300A discloses a method for preparing a laminated fiber fabric reinforced composite material antenna cover. The main body of the antenna cover preform adopts a 2.5D fiber weaving method. The fabric is a pre-oriented structural product formed in one step. It combines the two fiber weaving methods of 2.5D and needle punching to form an inner, middle and outer layer flat laminated structure, and then fixes the entire multi-layer fiber braided preform by needle punching with small strands of fiber. Since the antenna cover preform prepared by this scheme is a flat laminated structure as a whole, the interlayer bonding force is poor. At the same time, due to the addition of the needle punching process, the fiber volume content of the antenna cover preform is low, and the overall structural strength of the cover after molding is not high.

[0006] CN107244082A discloses a method for forming a thin-walled, variable-thickness composite radome. The preform is prepared using a combination of a woven 2D fabric, a woven 2.5D fabric, and an integrally woven capping fabric. The inner and outer uniform thickness areas utilize a woven twill 2D unit sleeve fabric, the top thickening area utilizes an integrally woven fabric, and the root thickening area utilizes a laminated 2.5D woven fabric. Because this solution uses three different fabric structures, the fiber volume content varies between regions. Furthermore, the fabrics in each region are connected solely by stitching, resulting in low overall structural strength.

[0007] CN107866925A discloses a RTM molding method for a resin-based variable-thickness radome. The product is divided into three regions: an inner uniform thickness layer, a thickness transition layer, and an outer uniform thickness layer. The inner and outer uniform thickness layers are layered with contoured woven fabric, while the thickness transition layer is formed by stitching fiber cloth. Due to the large number of contoured woven fabric layers, each layer has inherent defects such as yarn sparseness. This results in low fiber volume content in the inner and outer uniform thickness layers, resulting in poor quality consistency.

[0008] Domestic 2.5D woven preforms are mainly completed with the help of simple modified weaving machines and manual assistance. The degree of automation is low. All the circumferential weft insertion and warp fiber addition and subtraction of the fabric are completed manually. The production efficiency is low and the weaving cost is high, which seriously restricts the widespread use and development of 2.5D woven preform technology.

[0009] Therefore, how to better utilize 2.5D woven preform technology to prepare U-shaped antenna covers has become a problem that the inventors have worked hard to solve. Summary of the Invention

[0010] In response to the problems existing in the above-mentioned technology, the present invention provides a U-shaped antenna cover 2.5D woven preform, which adopts a 2.5D woven preform with excellent interlaminar strength as a composite antenna cover reinforcement. The reinforcement is prepared by sewing a 2.5D laminated woven main preform and a 2.5D ply-stitched secondary preform into one body through a three-dimensional stitching process. The reinforcement has high fiber volume content (50%±2%), high surface accuracy (±0.5mm), and low manufacturing cost (50% lower than the market price). The prepared antenna cover 2.5D woven preform / aromatic acetylene or polyimide composite material has the advantages of high interlaminar strength (≥35MPa), good dielectric properties (dielectric constant 3.2±0.1), high antenna cover surface accuracy (±0.1mm), excellent wave transmittance (≥90%), and high temperature resistance (≥450℃), and is particularly suitable for the needs of high-temperature, high-overload, and near-net-size composite material wave-transmitting antenna covers.

[0011] The main inventive concepts of the present invention are as follows: Due to the U-shaped and locally variable wall thickness structural characteristics of the radome preform, it is difficult to achieve this by using only a multi-layer and equal-thickness 2.5D laminated woven preform. The inventors finally decided to design the radome preform to consist of an equal-thickness 2.5D laminated woven main preform and a variable-thickness 2.5D ply-stitched secondary preform. By combining the two and sewing them into one using three-dimensional sewing technology, a radome 2.5D woven preform with an integral structure was obtained.

[0012] The specific technical solutions of the present invention are as follows: A U-shaped radome 2.5D braided preform is composed of a uniform-thickness 2.5D laminated braided main preform and a variable-thickness 2.5D ply stitched secondary preform, wherein: The main preform of the uniform thickness 2.5D laminated braid is a U-shaped uniform thickness structure with a height of 490-500mm, an outer diameter of 422mm at the open end, and a wall thickness of 6mm; The thickened 2.5D ply stitched secondary preform is a wedge-shaped ring with a variable thickness structure, with a height of 140-150mm and an outer diameter of 470mm at the open end. The thickness of the oblique section of the wedge-shaped ring gradually increases from 1mm to 24mm, and the height is 100mm. The bottom width of the straight section of the wedge-shaped ring is 24mm, and the height is 40mm-50mm. When the two are sutured, the suture density is 5mm / needle-10mm / needle, and the suture thread is quartz fiber thread with a wire diameter of 0.1mm-0.5mm.

[0013] After stitching, the U-shaped antenna cover 2.5D woven preform is finally obtained with a height of 490mm-500mm and an outer diameter of 470mm at the open end. The open end has a gradient thickness structure, the wall thickness of the main body uniform thickness area is 6mm, and the wall thickness of the main body variable thickness area is 7mm-30mm.

[0014] Furthermore, during the specific preparation, the uniform thickness 2.5D laminated braided main preform is prepared using a horizontal six-layer angle interlocking braiding machine (DHB576 model), with a braiding angle of 55°-85°, a braiding speed of 0.05rad / s-0.1rad / s, 2-5 laminated braiding layers, and quartz fiber with a braiding fiber density of 1900tex-3800tex and a twist of 10t / m-50t / m. The thickened 2.5D ply-stitched secondary preform is fabricated by ply-stitching 2.5D woven fabric. The 2.5D woven fabric uses domestically produced quartz fiber (190-380 tex), with a warp density of 5-10 strands / cm, a weft density of 2-5 strands / cm, a thickness of 1-4 mm, and 6-24 plies. The sutures are domestically produced quartz suture thread with a diameter of 0.1-0.5 mm and a stitch density of 5-10 mm / needle.

[0015] The thickened 2.5D laminated stitching secondary preform is fitted onto the open end of the equal-thickness 2.5D laminated woven main preform with a fitting depth of 140mm-150mm so that the end faces of the 2.5D laminated woven main preform and the 2.5D laminated stitching secondary preform are flush. A three-dimensional stitching machine is used for stitching in the full-thickness direction, which is consistent with the 2.5D woven fabric laminate stitching process parameters. The stitching density is 5mm / needle-10mm / needle, and the stitching thread uses domestic quartz stitching thread with a wire diameter of 0.1mm-0.5mm. Finally, a U-shaped antenna cover 2.5D woven preform is obtained.

[0016] The existing RTM molding process is adopted to compound a U-shaped antenna cover 2.5D braided preform with an arylacetylene resin or a polyimide resin to prepare a 2.5D braided preform / arylacetylene or polyimide composite antenna cover.

[0017] In addition, other medium and low temperature resins can also be used for compounding, and the inventor will not elaborate on them.

[0018] Compared with the prior art, the present invention has the following advantages: The preform has a high fiber volume content (50%±2%), high surface accuracy (±0.5mm), and low manufacturing cost (50% lower than the market price). The prepared antenna cover 2.5D woven preform / aromatic or polyimide composite material and its advantages have high interlayer strength (≥35MPa), good dielectric properties (dielectric constant 3.2±0.1), high antenna cover surface accuracy (±0.1mm), excellent wave transmittance (≥90%), high temperature resistance (≥450℃), etc., and are particularly suitable for the needs of high-temperature, high-overload, and near-net-size formed composite material wave-transparent antenna covers. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1This is a front view of the U-shaped radome 2.5D braided preform of the present invention; Figure 2 This is a front view of the uniform thickness 2.5D laminated braided main preform of the present invention; Figure 3 This is a front view of the thickened 2.5D ply stitched secondary preform according to the present invention. DETAILED DESCRIPTION

[0020] The present invention will be further described below in conjunction with specific embodiments, which may enable those skilled in the art to more fully understand the present invention, but does not limit the present invention in any way. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0021] The U-shaped antenna cover 2.5D braided preform provided by the present invention is as follows Figure 1 As shown, it consists of a uniform thickness 2.5D laminated woven main preform and a variable thickness 2.5D ply stitched secondary preform, with a height of 490mm-500mm, an outer diameter of 470mm at the open end, and a gradually variable thickness structure at the open end. The wall thickness of the uniform thickness area of ​​the main body is 6mm, and the wall thickness of the variable thickness area of ​​the main body is 7mm-30mm. The main preform of the uniform thickness 2.5D laminated braided body is a U-shaped uniform thickness structure. Figure 2 As shown, the height is 490-500mm, the outer diameter of the open end is 422mm, and the wall thickness is 6mm; The thickened 2.5D laminated stitched secondary preform is a wedge-shaped ring structure. Figure 3 As shown, the height is 140-150mm, the outer diameter of the open end is 470mm, the thickness of the oblique section of the wedge-shaped ring gradually increases from 1mm to 24mm, the height is 100mm, the bottom width of the straight section of the wedge-shaped ring is 24mm, and the height is 40mm-50mm; When the two are stitched together, the stitching density is 5mm / needle-10mm / needle, and the stitching thread is quartz fiber thread with a wire diameter of 0.1mm-0.5mm. After stitching, the U-shaped antenna cover 2.5D woven preform is finally obtained.

[0022] Example 1 A U-shaped radome 2.5D braided preform is prepared by combining a uniform-thickness 2.5D laminated braided main preform and a variable-thickness 2.5D laminated stitched secondary preform, and then sewing them through the full-thickness direction.

[0023] The uniform thickness 2.5D laminated braided main preform is a U-shaped uniform thickness layer with a height of 495mm, an outer diameter of 422mm at the open end, and a wall thickness of 6mm; the variable thickness 2.5D laminated stitched secondary preform is a wedge-shaped circular ring variable thickness layer with a height of 140mm, an outer diameter of 470mm at the open end, and a wall thickness of 1mm-24mm.

[0024] The final U-shaped antenna cover 2.5D woven preform is 495mm high and 470mm in outer diameter at the open end. The open end has a gradient thickness structure, with a wall thickness of 6mm in the main body uniform thickness area and a wall thickness of 7mm-30mm in the main body variable thickness area.

[0025] The preparation method is as follows: Several quartz fibers (type B / 1900tex, twist 50t / m, Hubei Feilihua Quartz Glass Co., Ltd.) were wound on a braiding yarn bobbin. According to the designed braiding process parameters (braiding angle 75°, braiding speed 0.07rad / s, and number of laminated braiding layers 3), a U-shaped equal-thickness 2.5D laminated braided main preform was prepared using a horizontal six-layer angle interlocking braiding machine.

[0026] According to the designed laying process parameters (number of layers: 12), several 2.5D woven fabrics (type B / 190tex, warp density 9 strands / cm, weft density 4 strands / cm, cloth thickness 2 mm, Hubei Feilihua Quartz Glass Co., Ltd.) were wedge-laid to prepare wedge-shaped laying units; according to the designed stitching process parameters (stitching density 5 mm / needle), domestic quartz stitching thread (SJ106, wire diameter 0.5 mm, Henan Shenjiu Tianhang New Materials Co., Ltd.) was used to stitch the wedge-shaped laying units to prepare a wedge-shaped circular variable thickness 2.5D lay-up stitched secondary preform.

[0027] The prepared equal-thickness 2.5D laminated woven main preform and the wedge-shaped circular variable-thickness 2.5D ply-stitched secondary preform were fitted together so that the open end faces of the 2.5D laminated woven main preform and the 2.5D ply-stitched secondary preform were flush to obtain a fitted assembly; according to the designed stitching process parameters (stitching density 5mm / needle), domestic quartz stitching wire (SJ106, wire diameter 0.5mm, Henan Shenjiu Aerospace New Materials Co., Ltd.) was used to stitch the fitted assembly to prepare a U-shaped antenna cover 2.5D woven preform.

[0028] A 2.5D braided preform for the U-shaped radome is placed into the RTM mold cavity. The mold is then vacuumed to check the mold's sealing properties and ensure a vacuum condition. The RTM mold and liquid arylacetylene resin (AS-ER, 95% solids, East China University of Science and Technology) are placed in an oven and heated to 80-85°C. The injection line is connected. The liquid arylacetylene resin is injected into the RTM mold cavity for 7-8 hours at a pressure of 0.1 MPa-1.6 MPa. After injection is complete, the valve is closed and the mold temperature is raised to 250°C at a rate of 2-3°C / min. This temperature is maintained for 10-12 hours. After complete curing, the mold cavity is opened and the 2.5D braided preform / arylacetylene composite radome is removed.

[0029] The fiber volume content of the 2.5D woven preform of the U-shaped antenna cover prepared above is 49.7%, and the surface accuracy is 0.386mm; the interlayer strength of the 2.5D woven preform / aromatic acetylene composite antenna cover is 38.6MPa, and the dielectric constant is 3.15; the surface accuracy of the 2.5D woven preform / aromatic acetylene composite antenna cover is 0.089mm, the wave transmittance is 95.8%, and the temperature resistance level is 500℃.

[0030] Example 2 A U-shaped radome 2.5D braided preform is prepared by combining a uniform-thickness 2.5D laminated braided main preform and a variable-thickness 2.5D ply-stitched secondary preform, which are then sewn together through the full-thickness direction.

[0031] The uniform thickness 2.5D laminated braided main preform is a U-shaped uniform thickness layer with a height of 497mm, an outer diameter of 422mm at the open end, and a wall thickness of 6mm; the variable thickness 2.5D laminated stitched secondary preform is a wedge-shaped circular ring variable thickness layer with a height of 142mm, an outer diameter of 470mm at the open end, and a wall thickness of 1mm-24mm.

[0032] The final U-shaped antenna cover 2.5D woven preform is 497mm high and 470mm in outer diameter at the open end. The open end has a gradient thickness structure, with a wall thickness of 6mm in the main body uniform thickness area and a wall thickness of 7mm-30mm in the main body variable thickness area.

[0033] The preparation method is as follows: Several quartz fibers (type B / 3800tex, twist 10t / m, Hubei Feilihua Quartz Glass Co., Ltd.) were wound on the braiding yarn shaft and braided according to the designed braiding process parameters (braiding angle 85 o , weaving speed 0.08 rad / s, number of laminated braiding layers 2), a U-shaped equal-thickness 2.5D laminated braided main preform was prepared using a horizontal six-layer angle interlocking braiding machine.

[0034] According to the designed laying process parameters (number of laying layers: 24), several 2.5D woven fabrics (type B / 380tex, warp density 5 strands / cm, weft density 2 strands / cm, cloth thickness 1 mm, Hubei Feilihua Quartz Glass Co., Ltd.) were wedge-laid to prepare wedge-shaped laying units; according to the designed stitching process parameters (stitching density 10 mm / needle), domestic quartz stitching thread (ZQST24, wire diameter 0.2 mm, Tianjin Zhongtian Junda) was used to stitch the wedge-shaped laying units to prepare wedge-shaped circular variable thickness 2.5D lay-up stitched secondary preforms.

[0035] The prepared U-shaped equal-thickness 2.5D laminated woven main preform and the wedge-shaped circular variable-thickness 2.5D ply-stitched secondary preform were suited so that the open end faces of the 2.5D laminated woven main preform and the 2.5D ply-stitched secondary preform were flush to obtain a suited assembly; according to the designed stitching process parameters (stitching density 10mm / needle), domestic quartz stitching wire (ZQST24, wire diameter 0.2mm, Tianjin Zhongtian Junda) was used to stitch the suited assembly to prepare a U-shaped antenna cover 2.5D woven preform.

[0036] A 2.5D woven preform / aromatic acetylene composite material antenna cover is obtained according to the RTM molding process in Example 1; the fiber volume content of the U-shaped antenna cover 2.5D woven preform prepared above is 50.1%, and the surface accuracy is 0.391mm; the interlayer strength of the 2.5D woven preform / aromatic acetylene composite material antenna cover is as high as 35.9MPa, and the dielectric constant is 3.13; the surface accuracy of the 2.5D woven preform / aromatic acetylene composite material antenna cover is 0.067mm, the wave transmittance is 93.4%, and the temperature resistance level is 500℃.

[0037] Example 3 A U-shaped radome 2.5D braided preform is prepared by combining a uniform-thickness 2.5D laminated braided main preform and a variable-thickness 2.5D ply-stitched secondary preform, which are then sewn together through the full-thickness direction.

[0038] The uniform thickness 2.5D laminated braided main preform is a U-shaped uniform thickness layer with a height of 493mm, an outer diameter of 422mm at the open end, and a wall thickness of 6mm; the variable thickness 2.5D laminated stitched secondary preform is a wedge-shaped circular ring variable thickness layer with a height of 145mm, an outer diameter of 470mm at the open end, and a wall thickness of 1mm-24mm.

[0039] The final U-shaped antenna cover 2.5D woven preform is 493mm high and 470mm in outer diameter at the open end. The open end has a gradient thickness structure, with a wall thickness of 6mm in the main body uniform thickness area and a wall thickness of 7mm-30mm in the main body variable thickness area.

[0040] The preparation method is as follows: Several quartz fibers (type B / 2850tex, twist 30t / m, Hubei Feilihua Quartz Glass Co., Ltd.) were wound on the braiding yarn shaft and braided according to the designed braiding process parameters (braiding angle 65 o , weaving speed 0.06rad / s, number of laminated braiding layers 4), a U-shaped equal-thickness 2.5D laminated braided main preform was prepared using a horizontal six-layer angle interlocking braiding machine.

[0041] According to the designed laying process parameters (number of laying layers 6), several 2.5D woven fabrics (type B / 380tex, warp density 6 strands / cm, weft density 3 strands / cm, cloth thickness 4 mm, Yixing Xinli Weaving) were wedge-laid to prepare wedge-shaped laying units; according to the designed stitching process parameters (stitching density 9 mm / needle), domestic quartz stitching thread (SJ106, wire diameter 0.45 mm, Henan Shenjiu Tianhang New Materials Co., Ltd.) was used to stitch the wedge-shaped laying units to prepare wedge-shaped circular variable thickness 2.5D lay-up stitching sub-preforms.

[0042] The prepared U-shaped equal-thickness 2.5D laminated woven main preform and the wedge-shaped circular variable-thickness 2.5D ply-stitched secondary preform were suited so that the open end faces of the 2.5D laminated woven main preform and the 2.5D ply-stitched secondary preform were flush to obtain a suited assembly; according to the designed stitching process parameters (stitching density 9mm / needle), domestic quartz stitching wire (SJ106, wire diameter 0.45mm, Henan Shenjiu Aerospace New Materials Co., Ltd.) was used to stitch the suited assembly to prepare a U-shaped antenna cover 2.5D woven preform.

[0043] A 2.5D woven preform / aromatic acetylene composite material antenna cover is obtained according to the RTM molding process in Example 1; the fiber volume content of the U-shaped antenna cover 2.5D woven preform prepared above is 48.5%, and the surface accuracy is 0.388mm; the interlayer strength of the 2.5D woven preform / aromatic acetylene composite material antenna cover is as high as 35.6MPa, and the dielectric constant is 3.11; the surface accuracy of the 2.5D woven preform / aromatic acetylene composite material antenna cover is 0.065mm, the wave transmittance is 100.1%, and the temperature resistance level is 500℃.

[0044] Example 4 A U-shaped radome 2.5D braided preform is prepared by combining a uniform-thickness 2.5D laminated braided main preform and a variable-thickness 2.5D ply-stitched secondary preform, which are then sewn together through the full-thickness direction.

[0045] The uniform thickness 2.5D laminated braided main preform is a U-shaped uniform thickness layer with a height of 500mm, an outer diameter of 422mm at the open end, and a wall thickness of 6mm; the variable thickness 2.5D laminated stitched secondary preform is a wedge-shaped circular variable thickness layer with a height of 140mm, an outer diameter of 470mm at the open end, and a wall thickness of 1mm-24mm.

[0046] The final U-shaped antenna cover 2.5D woven preform is 500mm high and 470mm in outer diameter at the open end. The open end has a gradient thickness structure, with a wall thickness of 6mm in the main body uniform thickness area and a wall thickness of 7mm-30mm in the main body variable thickness area.

[0047] The preparation method is as follows: Several quartz fibers (type B / 2850tex, twist 20t / m, Henan Shenjiu Tianhang New Materials Co., Ltd.) were wound on the braiding yarn shaft and braided according to the designed braiding process parameters (braiding angle 55 o , weaving speed 0.05rad / s, number of laminated braiding layers 5), a U-shaped equal-thickness 2.5D laminated braided main preform was prepared using a horizontal six-layer angle interlocking braiding machine.

[0048] According to the designed laying process parameters (number of laying layers: 8), several 2.5D woven fabrics (type B / 190tex, warp density 8 strands / cm, weft density 4 strands / cm, cloth thickness 3mm, Henan Shenjiu Tianhang New Materials Co., Ltd.) were wedge-laid to prepare wedge-shaped laying units; according to the designed stitching process parameters (stitching density 8mm / needle), domestic quartz stitching thread (SJ106, wire diameter 0.35mm, Henan Shenjiu Aerospace New Materials Co., Ltd.) was used to stitch the wedge-shaped laying units to prepare a wedge-shaped circular variable thickness 2.5D lay-up stitched sub-preform.

[0049] The prepared U-shaped equal-thickness 2.5D laminated woven main preform and the wedge-shaped circular variable-thickness 2.5D ply-stitched secondary preform were set together so that the open end faces of the 2.5D laminated woven main preform and the 2.5D ply-stitched secondary preform were flush to obtain a set assembly; according to the designed stitching process parameters (stitching density 8mm / needle), domestic quartz stitching wire (SJ106, wire diameter 0.35mm, Henan Shenjiu Tianhang New Materials Co., Ltd.) was used to stitch the set assembly to prepare a U-shaped antenna cover 2.5D woven preform.

[0050] According to the same RTM molding process in Example 1, the U-shaped antenna cover 2.5D woven preform is compounded with liquid polyimide resin to obtain a 2.5D woven preform / polyimide composite antenna cover; the fiber volume content of the U-shaped antenna cover 2.5D woven preform prepared above is 50.7%, and the surface accuracy is 0.396mm; the interlayer strength of the 2.5D woven preform / polyimide composite antenna cover is as high as 47.9MPa, and the dielectric constant is 3.24; the surface accuracy of the 2.5D woven preform / polyimide composite antenna cover is 0.087mm, the wave transmittance is 99.1%, and the temperature resistance level is 450℃.

[0051] Example 5 A U-shaped radome 2.5D braided preform is prepared by combining a uniform-thickness 2.5D laminated braided main preform and a variable-thickness 2.5D ply-stitched secondary preform, and then sewing them through the full-thickness direction.

[0052] The uniform thickness 2.5D laminated braided main preform is a U-shaped uniform thickness layer with a height of 498mm, an outer diameter of 422mm at the open end, and a wall thickness of 6mm; the variable thickness 2.5D laminated stitched secondary preform is a wedge-shaped circular ring variable thickness layer with a height of 140mm, an outer diameter of 470mm at the open end, and a wall thickness of 1mm-24mm.

[0053] The final U-shaped antenna cover 2.5D woven preform is 498mm high and 470mm in outer diameter at the open end. The open end has a gradient thickness structure, with a wall thickness of 6mm in the main body uniform thickness area and a wall thickness of 7mm-30mm in the main body variable thickness area.

[0054] The preparation method is as follows: Several quartz fibers (type B / 3800tex, twist 10t / m, Hubei Feilihua Quartz Glass Co., Ltd.) were wound on the braiding yarn shaft and braided according to the designed braiding process parameters (braiding angle 85 o , weaving speed 0.09 rad / s, number of laminated braiding layers 2), a U-shaped equal-thickness 2.5D laminated braided main preform was prepared using a horizontal six-layer angle interlocking braiding machine.

[0055] According to the designed laying process parameters (number of laying layers: 24), several 2.5D woven fabrics (type B / 190tex, warp density 9 strands / cm, weft density 5 strands / cm, cloth thickness 1mm, Hubei Feilihua Quartz Glass Co., Ltd.) were wedge-laid to prepare wedge-shaped laying units; according to the designed stitching process parameters (stitching density 7mm / needle), domestic quartz stitching thread (SJ106, wire diameter 0.25mm, Henan Shenjiu Aerospace New Materials Co., Ltd.) was used to stitch the wedge-shaped laying units to prepare a wedge-shaped circular variable thickness 2.5D lay-up stitched sub-preform.

[0056] The prepared U-shaped equal-thickness 2.5D laminated woven main preform and the wedge-shaped circular variable-thickness 2.5D ply-stitched secondary preform were set together so that the open end faces of the 2.5D laminated woven main preform and the 2.5D ply-stitched secondary preform were flush to obtain a set assembly; according to the designed stitching process parameters (stitching density 7mm / needle), domestic quartz stitching wire (SJ106, wire diameter 0.25mm, Henan Shenjiu Tianhang New Materials Co., Ltd.) was used to stitch the set assembly to prepare a U-shaped antenna cover 2.5D woven preform.

[0057] A 2.5D woven preform / aromatic acetylene composite material antenna cover was obtained according to the RTM molding process in Example 1; the fiber volume content of the U-shaped antenna cover 2.5D woven preform prepared above was 47.9%, and the surface accuracy was 0.416 mm; the interlayer strength of the 2.5D woven preform / aromatic acetylene composite material antenna cover was as high as 35.6 MPa, and the dielectric constant was 3.21; the surface accuracy of the 2.5D woven preform / aromatic acetylene composite material antenna cover was 0.077 mm, the wave transmittance was 103.5%, and the temperature resistance grade was 500°C.

[0058] Example 6 A U-shaped radome 2.5D braided preform is prepared by combining a uniform-thickness 2.5D laminated braided main preform and a variable-thickness 2.5D ply-stitched secondary preform, which are then sewn together through the full-thickness direction.

[0059] The uniform thickness 2.5D laminated braided main preform is a U-shaped uniform thickness layer with a height of 490mm, an outer diameter of 422mm at the open end, and a wall thickness of 6mm; the variable thickness 2.5D laminated stitched secondary preform is a wedge-shaped circular ring variable thickness layer with a height of 140mm, an outer diameter of 470mm at the open end, and a wall thickness of 1mm-24mm.

[0060] The final U-shaped antenna cover 2.5D woven preform is 490mm high and 470mm in outer diameter at the open end. The open end has a gradient thickness structure, with a wall thickness of 6mm in the main body uniform thickness area and a wall thickness of 7mm-30mm in the main body variable thickness area.

[0061] The preparation method is as follows: Several quartz fibers (type B / 1900tex, twist 40t / m, Hubei Feilihua Quartz Glass Co., Ltd.) were wound on the braiding yarn shaft and braided according to the designed braiding process parameters (braiding angle 75 o , weaving speed 0.1 rad / s, number of laminated braiding layers 3), a U-shaped equal-thickness 2.5D laminated braided main preform was prepared using a horizontal six-layer angle interlocking braiding machine.

[0062] According to the designed laying process parameters (number of laying layers: 12), several 2.5D woven fabrics (type B / 380tex, warp density 7 strands / cm, weft density 4 strands / cm, cloth thickness 2mm, Hubei Feilihua Quartz Glass Co., Ltd.) were wedge-laid to prepare wedge-shaped laying units; according to the designed stitching process parameters (stitching density 6mm / needle), domestic quartz stitching thread (SJ106, wire diameter 0.1mm, Henan Shenjiu Tianhang New Materials Co., Ltd.) was used to stitch the wedge-shaped laying units to prepare wedge-shaped circular variable thickness 2.5D lay-up stitching sub-preforms.

[0063] The prepared U-shaped equal-thickness 2.5D laminated woven main preform and the wedge-shaped circular variable-thickness 2.5D ply-stitched secondary preform were suited so that the open end faces of the 2.5D laminated woven main preform and the 2.5D ply-stitched secondary preform were flush to obtain a suited assembly; according to the designed stitching process parameters (stitching density 6mm / needle), domestic quartz stitching wire (SJ106, wire diameter 0.1mm, Henan Shenjiu Aerospace New Materials Co., Ltd.) was used to stitch the suited assembly to prepare a U-shaped antenna cover 2.5D woven preform.

[0064] A 2.5D woven preform / aromatic acetylene composite material antenna cover was obtained according to the RTM molding process in Example 1; the fiber volume content of the U-shaped antenna cover 2.5D woven preform prepared above was 51.8%, and the surface accuracy was 0.356mm; the interlayer strength of the 2.5D woven preform / aromatic acetylene composite material antenna cover was as high as 39.7MPa, and the dielectric constant was 3.23; the surface accuracy of the 2.5D woven preform / aromatic acetylene composite material antenna cover was 0.045mm, the wave transmittance was 93.5%, and the temperature resistance grade was 500°C.

[0065] Comparative Example: A U-shaped composite radome is prepared by laminating quartz fiber / silicon-containing aromatic acetylene prepreg and then molding. The U-shaped composite radome has a height of 490 mm to 500 mm, an outer diameter of 470 mm at the open end, and a wall thickness of 6 mm to 30 mm.

[0066] The preparation method is as follows: Based on the dimensions of a U-shaped composite radome, a composite material digital layup design was implemented. Through solid-fill-based digital layup design, 2D graphical data for each layer was generated, and prepreg (developed by East China University of Science and Technology, with a resin content of 30%) was cut for each layer. Using layup simulation analysis technology, the prepreg layers were stacked and laid, and then vacuumed and precured to create the radome precured body.

[0067] The pre-cured radome is placed in the female mold cavity and pressed at a mold temperature of (170±5)°C and a clamping pressure of 2.5MPa to 3MPa. After clamping, the mold temperature is raised to 250°C at a rate of 2°C / min to 3°C / min and maintained at this temperature for 7-8 hours. After complete curing, the mold cavity is opened and the composite radome blank is ejected. After machining, a U-shaped composite radome is obtained.

[0068] The U-shaped composite material antenna cover prepared above has an interlayer strength of 23.1 MPa, a dielectric constant of 3.37, a surface accuracy of 0.267 mm, a wave transmittance of 92.8%, and a temperature resistance level of 500°C.

[0069] The inventors compared the relevant properties of the composite radome materials obtained in the examples and comparative examples, and the results are shown in the following table: Table 1 Comparison of composite radome performance As shown in Table 1, the present invention provides two types of U-shaped composite radomes, one with a temperature resistance rating of 450°C and the other with a temperature resistance rating of 500°C, for different operating conditions. Example 4 is a composite radome with a temperature resistance rating of 450°C, while the other examples and comparative examples are all composite radomes with a temperature resistance rating of 500°C. The radome in Example 4 has the highest interlaminar shear strength, but a low temperature resistance rating. Among the other examples, the U-shaped radome 2.5D woven preform and its radome prepared in Example 6 are the most optimal, with a high fiber volume content (51.8%), high surface accuracy (0.045 mm), high interlaminar shear strength (39.7 MPa), high temperature resistance, and excellent overall performance. The comparative example, on the other hand, has a low interlaminar shear strength (23.1 MPa) and poor surface accuracy (0.267 mm).

[0070] In summary, the U-shaped antenna cover preform and the antenna cover preparation method thereof provided by the present invention, which combine 2.5D laminated weaving and 2.5D ply stitching, make up for the defects of the traditional layup / molding process or layup / autoclave process, such as the inadequate pressurization of the cover, poor interlayer force, low surface accuracy, and high dielectric constant. While maintaining good temperature resistance and wave transmission performance, it greatly improves the molding accuracy and overall structural performance of the U-shaped complex surface composite material antenna cover.

[0071] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary engineering technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A U-shaped radome 2.5D braided preform, characterized in that: It consists of a main preform with 2.5D laminated braids of equal thickness and a secondary preform with 2.5D laminates of varying thickness, where: The main preform of the uniform thickness 2.5D laminated braid is a U-shaped uniform thickness structure with a height of 490-500mm, an outer diameter of 422mm at the open end, and a wall thickness of 6mm; The thickened 2.5D ply stitched secondary preform is a wedge-shaped ring with a variable thickness structure, with a height of 140-150mm and an outer diameter of 470mm at the open end. The thickness of the oblique section of the wedge-shaped ring gradually increases from 1mm to 24mm, and the height is 100mm. The bottom width of the straight section of the wedge-shaped ring is 24mm, and the height is 40mm-50mm. When the two are sutured, the suture density is 5mm / needle-10mm / needle, and the suture thread is quartz fiber thread with a wire diameter of 0.1mm-0.5mm.

2. The U-shaped radome 2.5D braided preform according to claim 1, characterized in that: The final U-shaped antenna cover 2.5D woven preform has a height of 490mm-500mm, an outer diameter of 470mm at the open end, a gradient thickness structure at the open end, a wall thickness of 6mm in the main body uniform thickness area, and a wall thickness of 7mm-30mm in the main body variable thickness area.

3. The U-shaped radome 2.5D braided preform according to claim 1, characterized in that: The equal-thickness 2.5D laminated braided main preform is prepared by a horizontal six-layer angle interlocking braiding machine with a braiding angle of 55°-85°, a braiding speed of 0.05rad / s-0.1rad / s, 2-5 laminated braiding layers, and quartz fiber with a braiding fiber density of 1900tex-3800tex and a twist of 10t / m-50t / m.

4. The U-shaped radome 2.5D braided preform according to claim 1, characterized in that: The thickened 2.5D ply stitched secondary preform is prepared by ply stitching 2.5D woven fabric, wherein the 2.5D woven fabric adopts domestic quartz fiber, 190tex-380tex, warp density 5 threads / cm-10 threads / cm, weft density 2 threads / cm-5 threads / cm, cloth thickness 1mm-4mm, and number of layers 6-24; the suture thread adopts domestic quartz suture thread, wire diameter 0.1mm-0.5mm, and suture density 5mm / needle-10mm / needle.

5. The U-shaped radome 2.5D braided preform according to claim 1, characterized in that: The thickened 2.5D laminated stitched secondary preform is fitted onto the open end of the equal-thickness 2.5D laminated woven main preform with a fitting depth of 140mm-150mm so that the end faces of the open ends of the 2.5D laminated woven main preform and the 2.5D laminated stitched secondary preform are flush. A three-dimensional stitching machine is used for stitching in the full-thickness direction with a stitching density of 5mm / needle-10mm / needle. The stitching thread is made of domestic quartz fiber thread with a wire diameter of 0.1mm-0.5mm, and a U-shaped antenna cover 2.5D woven preform is obtained.

6. The U-shaped radome 2.5D braided preform according to claim 1, characterized in that: The RTM molding process is adopted to compound a U-shaped radome 2.5D braided preform with arylacetylene resin or polyimide resin to prepare a 2.5D braided preform / arylacetylene or polyimide composite radome.

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