A kind of longitudinal and transverse ribbed carbon fiber antenna frame modular forming die and preparation method

Abstract

This invention relates to a molding die and manufacturing method for a longitudinally and transversely reinforced carbon fiber antenna frame. The molding die consists of a base mold and nine separate split molding dies. The molding process includes the following steps: mold cleaning; laying the web skin; mold assembly; laying the frame skin to form the component; demolding and post-processing. This invention achieves a continuous overall layup design for the grid structure carbon fiber antenna frame through a modular production method that involves laying individual layers using separate molding dies and then assembling them. This avoids problems such as reduced layup strength caused by fiber shearing in existing layup methods. By combining multiple molding dies with the base mold, the longitudinally and transversely reinforced carbon fiber antenna frame is co-cured in one step, achieving near-net-shape molding. This avoids the potential risks of insufficient joint strength and fiber damage caused by the need for secondary mechanical connections in existing antenna frames.

Description

Technical Field

[0001] This invention belongs to the field of radar antenna system processing and manufacturing, and relates to a modular and integrated molding die and molding method for a longitudinally and transversely reinforced carbon fiber frame. It is mainly used in airborne radar load-bearing structural components that require lightweight and high strength. Background Technology

[0002] The antenna frame is a major component of the radar antenna feeder system. It is a structural component that provides mounting support for the antenna system or the entire microwave unit and has functions such as load-bearing, impact resistance, and weather resistance.

[0003] Currently, depending on the materials used in the antenna frame manufacturing process, there are two main methods. One method involves assembling aluminum alloy profile parts into a frame assembly using riveting or screwing. The other method involves first molding frame components from advanced composite materials such as carbon fiber, and then fabricating the antenna frame through secondary adhesive bonding or mechanical connection. However, the above antenna frame manufacturing methods have the following main shortcomings:

[0004] (1) The frame processing method of riveting or screwing aluminum alloy materials has disadvantages such as the large weight of the antenna frame due to the aluminum alloy material, which cannot meet the requirements of lightweight airborne radar antenna frames.

[0005] (2) The frame processing method of first molding the carbon fiber parts separately and then connecting and assembling them has disadvantages such as stress concentration at the connection joints, easy cracking due to impact and vibration, and long frame processing cycle. It is not suitable for use in radar antenna frames with high load-bearing requirements.

[0006] The radar antenna frame for a certain product has external dimensions of 1500mm×750mm×120mm. The design requires the weight to be controlled within 10kg, and the component must meet the requirements of 80g overload impact, high frequency vibration and 150kg load-bearing capacity. The existing frame molding materials and manufacturing methods can no longer meet the product's requirements for lightweighting and high strength load-bearing capacity. Summary of the Invention

[0007] Technical problems to be solved

[0008] To overcome the shortcomings of existing radar antenna frame manufacturing methods, this invention proposes a new one-time co-curing molding technique for longitudinally and transversely reinforced carbon fiber radar antenna frames. This technique utilizes a modular, separate, and then assembled molding method using a single molding mold, combined with the use of multiple metal molds and high-precision guiding and limiting functions. This avoids the disadvantages of existing radar antenna frame structures, such as large weight or insufficient load-bearing strength, and meets the requirements for lightweight and high overload performance of airborne radar antenna frames.

[0009] Technical solution

[0010] A molding die for a longitudinally and transversely reinforced carbon fiber antenna frame, wherein the antenna frame is a frame structure with two stringers and two ribs; characterized in that it consists of nine molding dies and a base mold; the geometry of the nine molding dies is taken from the geometry of the stringers, ribs and frame in the antenna frame and thermally compensated; the bottom surface of each molding die is designed with positioning pins for assembling and positioning the molding die and the base mold and for guiding and limiting displacement during pressure curing; the positioning pins are cylindrical pins with a 60° taper, a diameter of d and a height of h; the base mold is an integral flat plate structure, longer than the antenna frame. The dimensions are 300mm larger than the antenna frame width, 160mm larger than the antenna frame width, and 30mm thick. Nine positioning holes are provided on the upper surface of the base plate mold, corresponding one-to-one with the positioning pins of the nine forming molds. The positioning holes include one circular hole, four oblique strip holes, and four straight strip holes. The oblique strip holes all point towards the center of the base plate mold. The length of each oblique strip hole is p, the width is q, and the angle between the oblique strip hole and the antenna frame length direction is α. The straight strip holes all point towards the center of the base plate mold, and the length of each straight strip hole is u and the width is v.

[0011] A further technical solution of the present invention: the geometry of the nine molding dies is taken from the geometry of the corresponding stringers, ribs, and frames in the antenna frame, and thermal compensation is performed, with a compensation coefficient of 1 / [1+(α m -α c )ΔT], where α m Coefficient of thermal expansion of mold material, unit: ×10 -6 / ℃;α c Coefficient of thermal expansion of molding material, unit: ×10 -6 / ℃; ΔT: Temperature difference between the curing temperature of the molding material and the ambient temperature, unit: ℃.

[0012] A further technical solution of the present invention: the length p of the oblique strip hole satisfies the following... Where d: the diameter of the corresponding positioning pin, in mm; t: the thickness of the corresponding antenna frame stringer or rib, in mm; w: the percentage of material compression during carbon fiber autoclave curing, in %; α: the angle between the oblique strip hole and the length direction of the antenna frame, in °.

[0013] A further technical solution of the present invention: the included angle α of the oblique strip hole satisfies the following... Where P: molding pressure of carbon fiber frame, unit: MPa; l: length of the four corner molds along the length of the antenna frame, unit: mm; s: length of the four corner molds along the width of the antenna frame, unit: mm.

[0014] A further technical solution of the present invention: the length u of the straight strip hole satisfies u≥(d+tw), where d: the diameter of the corresponding positioning pin, unit: mm; t: the thickness of the corresponding antenna frame stringer or rib, unit: mm; w: the percentage of material compression during carbon fiber autoclave curing, unit: mm.

[0015] A further technical solution of the present invention: the diameter of the circular hole, the width q of the oblique strip hole, and the width v of the straight strip hole are all clearance-fitted with the corresponding positioning pins, and the fit grade is H6; the depth of the circular hole, the oblique strip hole, and the straight strip hole are all 2mm greater than the height h of the corresponding forming mold positioning pin.

[0016] A further technical solution of the present invention: the nine forming molds and the base plate mold are all made of 45 steel.

[0017] A modular fabrication method for a longitudinally and transversely stiffened carbon fiber antenna frame, characterized by the following steps:

[0018] Step 1: Clean the molding mold and base plate mold 10 with alcohol, let them air dry at room temperature, and then apply release agent to the surface at least twice, with an interval of at least 10 minutes between each application.

[0019] Step 2: Individually lay the web skin of the stringers, ribs, and circumference frames onto the 9 forming molds, in the following layup sequence: [±45°] (织物) / 90° / 0° / ±45° (织物) / 0°]s, after the layup is completed, pre-compaction treatment is carried out;

[0020] Step 3: Assemble the 9 forming molds and the base plate mold after layering by using positioning pins and pin holes;

[0021] Step 4: Lay the outer skin of the frame onto the nine molded molds after mold closing, in the following layering sequence: 0°4 / 90° / 0°4 / ±45° (织物) / 0°4 / 90° / 0°4 / [±45° (织物) / 90° / 0° / ±45° (织物) / 0°]s, after the layup is completed, pre-compaction treatment is carried out;

[0022] Step 5: Lay out the insulating film and breathable felt in sequence, seal in a vacuum bag, put it in an autoclave for heating and curing, demold after curing, and perform post-processing to finally prepare the antenna frame component.

[0023] A further technical solution of the present invention: the prepreg of the fabric in the layup is T300 carbon fiber epoxy material with a layer thickness of 0.25mm.

[0024] A further technical solution of the present invention: the unidirectional tape in the layup is T800 carbon fiber epoxy material with a layer thickness of 0.12mm.

[0025] Beneficial effects

[0026] This invention provides a modular molding die and manufacturing method for a longitudinally and transversely reinforced carbon fiber antenna frame. By employing a modular production method of first laying individual layers in separate molding dies and then assembling them, a continuous overall layering design for the grid-structured carbon fiber antenna frame is achieved. This avoids problems such as reduced layer strength due to fiber shearing required in existing layering methods. Through the combined use of multiple molding dies and a base plate mold, a one-time co-curing molding of the longitudinally and transversely reinforced carbon fiber antenna frame is achieved, avoiding the potential for insufficient joint strength caused by the secondary mechanical connection required in existing antenna frames. The assembly positioning and displacement guiding and limiting functions of the pin holes on the molding dies and base plate molds achieve near-net-shape, high-precision molding of the longitudinally and transversely reinforced carbon fiber antenna frame, avoiding fiber damage and breakage risks caused by secondary machining of the antenna frame. Results from multiple prototype antenna frames for a certain military product demonstrate that the carbon fiber antenna frames prepared using this method exhibit high dimensional accuracy, strong overload resistance, and stable and reliable quality. Attached Figure Description

[0027] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0028] Figure 1 Carbon fiber antenna frame structure diagram: (a) 3D view of the antenna frame; (b) cross-sectional view of the frame plying;

[0029] Figure 2 Molding mold structure diagram;

[0030] Figure 3 Schematic diagram of the base plate mold structure: (c) Base plate mold location drawing; (d) Cross-sectional view of the base plate mold;

[0031] Figure 4 The present invention relates to a molding schematic diagram.

[0032] In the figure, 1-9 - forming mold; 10 - base plate mold; 11 - carbon fiber antenna frame; 12 - antenna frame stringer; 13 - antenna frame rib; 14 - antenna frame enclosure; 15 - positioning pin; 16 - circular hole; 17 - oblique strip hole; 18 - straight strip hole; 19 - web skin of stringer, rib and enclosure; 20 - outer skin of enclosure. P - length of oblique strip hole 17; q - width of oblique strip hole 17; α - angle between oblique strip hole 17 and antenna frame 11 along its length; u - length of straight strip hole 18; v - width of straight strip hole 18. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0034] This invention provides a molding die for a longitudinally and transversely reinforced carbon fiber antenna frame. The antenna frame is a frame with two long stringers and two ribs. The die consists of molding dies 1-9 and a base die 10. The geometry of molding dies 1-9 is taken from the geometry of the corresponding long stringers 12, ribs 13, and frame 14 in the antenna frame 11 and thermally compensated. After the nine molding dies are assembled with the base die, a "nine-square grid" structure is formed. The bottom surface of molding dies 1-9 is designed with positioning pins 15 for positioning the molding dies 1-9 with the base die 10 and for guiding and limiting displacement during pressure curing. The base plate mold 10 is an integral flat plate structure with nine positioning holes on its upper surface, corresponding one-to-one with the positioning pins 15 of the forming molds 1 to 9. The positioning holes include one circular hole 16, four oblique strip holes 17, and four straight strip holes 18. The oblique strip holes 17 are all angled towards the center forming mold 5 (i.e., the center of the base plate mold 10), with a length of p, a width of q, and an angle α between their angle and the length of the antenna frame 11. The straight strip holes 18 are all angled towards the center forming mold 5 (i.e., the center of the base plate mold 10), with a length of u and a width of v. The diameter of the circular hole 16, the width q of the oblique strip hole 17, and the width v of the straight strip hole 18 are all clearance-fitted with the corresponding positioning pin 15, with a fit grade of H6; the depth of the oblique strip hole, the straight strip hole, and the circular hole is 2mm greater than the height h of the corresponding forming mold positioning pin; the forming molds 1 to 9 and the base plate forming mold 10 are all made of 45 steel.

[0035] This invention also provides a modular fabrication method for a longitudinally and transversely stiffened carbon fiber antenna frame, comprising the following steps:

[0036] Step 1: After cleaning the molding molds 1-9 and the base plate mold 10, apply the release agent at least twice;

[0037] Step 2: Lay the web skin 19 of the stringer 12, rib 13, and frame 14 onto the forming molds 1-9 respectively, in the following layering sequence: [±45°] (织物) / 90° / 0° / ±45° (织物) / 0°]s;

[0038] Step 3: Assemble the molds 1-9 after layering and the base plate mold 10 by positioning pins 15 and pin holes 16-18;

[0039] Step 4: Lay the outer skin 20 of the frame 14 onto the molded molds 1-9 after mold closing, in the following layering sequence: 0°4 / 90° / 0°4 / ±45° (织物) / 0°4 / 90° / 0°4 / [±45° (织物) / 90° / 0° / ±45° (织物) / 0°]s;

[0040] Step 5: The antenna frame 15 is finally prepared by autoclaving, demolding, and post-processing.

[0041] The prepreg of the fabric is T300 carbon fiber epoxy material with a layer thickness of 0.25mm.

[0042] The unidirectional tape is made of T800 carbon fiber epoxy material with a layer thickness of 0.12mm.

[0043] Example:

[0044] See appendix Figure 1 As shown, the antenna frame 11 is a longitudinally and transversely reinforced carbon fiber laminate structure, consisting of two stringers 12, two ribs 13, and a frame 14. The stringers 12 and ribs 13 are 2.8 mm thick, and the frame 14 is 4.8 mm thick. The antenna frame is required to weigh less than 10 kg and meet the requirements of 80 g overload impact, high frequency vibration, and 150 kg load-bearing capacity.

[0045] See appendix Figure 2 As shown, the forming molds 1-9 are punch structures. Their geometry is based on the geometry formed by the corresponding stringers 12, ribs 13, and frames 14 in the antenna frame 11, and is thermally compensated with a compensation coefficient of C. The bottom surface of the forming molds 1-9 is designed with positioning pins 15, which are used for the assembly and positioning of the forming molds 1-9 with the base plate mold 10 and for guiding and limiting displacement during pressure curing. The positioning pins 15 are cylindrical pins with a 60° taper, a diameter of d, and a height of h.

[0046] See appendix Figure 3As shown, the base plate mold 10 is an integral flat plate structure. Its length is 300mm larger than the length of the antenna frame 11, its width is 160mm larger than the width of the antenna frame 11, and its thickness is 30mm. The upper surface of the base plate mold 10 has one circular hole 16, four oblique strip holes 17, and four straight strip holes 18, which correspond one-to-one with the positions of the positioning pins 15 in the forming molds 1 to 9. The circular hole 16 corresponds to the position of the positioning pin 15 on the central forming mold 5, and the four oblique strip holes 17 correspond to the positions of the positioning pins 15 on forming molds 1, 3, 7, and 9. The oblique direction of the oblique strip holes 17 all points towards the central forming mold 5 (i.e., the center of the base plate mold 10), with a length of p, a width of q, and an angle α between their oblique direction and the length direction of the antenna frame 11. The four straight holes 18 correspond to the positions of the positioning pins 15 on the forming molds 2, 4, 6 and 8. The straight direction of the straight holes 18 all points to the center forming mold 5 (i.e. the center position of the base plate mold 10), and their length is u and their width is v.

[0047] In this embodiment, the compensation coefficient C of molding dies 1 to 9 is determined by the following formula:

[0048] C = 1 / (1+(α) m -α c )ΔT) ①

[0049] In the formula: α m The coefficient of thermal expansion of the mold material (unit: ×10) -6 / ℃); α c The coefficient of thermal expansion of the molding material (unit: ×10) -6 / ℃); ΔT is the temperature difference between the curing temperature of the molding material and the ambient temperature (unit: ℃).

[0050] In this embodiment, the length p of the oblique strip hole 17 is determined by the following formula:

[0051]

[0052] In the formula: d is the diameter of the positioning pin 15, in mm; t is the thickness of the stringer 12 or rib 13 in the corresponding antenna frame 11, in mm; w is the percentage of material compression during carbon fiber autoclave curing, in %; α is the angle between the oblique strip hole 17 and the length direction of the antenna frame 11, in °.

[0053] In this embodiment, the included angle α of the oblique strip hole 17 is determined by the following formula:

[0054]

[0055] In the formula: P is the molding pressure of the carbon fiber frame, in MPa; l is the length dimension of molding mold 1, molding mold 3, molding mold 7 and molding mold 9 along the length direction of antenna frame 11, in mm; s is the length dimension of molding mold 1, molding mold 3, molding mold 7 and molding mold 9 along the width direction of antenna frame 11, in mm.

[0056] In this embodiment, the length u of the straight strip hole 18 is determined by the following formula:

[0057] u≥(d+tw)④

[0058] In the formula: d is the diameter of the positioning pin 15, in mm; t is the thickness of the stringer 12 or rib 13 in the corresponding antenna frame 11, in mm; w is the percentage of material compression during carbon fiber autoclave curing, in %.

[0059] The diameter of the circular hole 16, the width q of the oblique strip hole 17, and the width v of the straight strip hole 18 are all clearance-fitted with the corresponding positioning pin 15, with a fit grade of H6.

[0060] The depth of the circular hole 16, the oblique strip hole 17, and the straight strip hole 18 is 2mm greater than the height h of the positioning pin 15 of the forming mold 1 to 9.

[0061] The forming molds 1 to 9 and the base plate forming mold 10 are all made of 45 steel.

[0062] The preparation process used to achieve the purpose of this invention includes the following steps:

[0063] (1) Clean the molding molds 1 to 9 and the base plate mold 10 with alcohol, let them air dry at room temperature, and then apply release agent to the surface at least twice, with an interval of at least 10 minutes.

[0064] (2) The web skin 19 of the stringer 12, rib 13 and frame 14 are individually laid on the molding molds 1 to 9, and the layering sequence is [±45°]. (织物) / 90° / 0° / ±45° (织物) / 0°]s, after the layup is completed, pre-compaction treatment is carried out;

[0065] (3) The molds 1 to 9 after the layup are assembled with the base plate mold 10 by means of positioning pins 15 and pin holes 16 to 18;

[0066] (4) After the molds are closed, the outer skin 20 of the frame 14 is laid on the molding molds 1 to 9, and the layering sequence is 0°4 / 90° / 0°4 / ±45°. (织物) / 0°4 / 90° / 0°4 / [±45° (织物) / 90° / 0° / ±45° (织物) / 0°]s, after the layup is completed, pre-compaction treatment is carried out;

[0067] (5) Lay out the isolation film and breathable felt in sequence, seal the vacuum bag, put it in the autoclave for heating and curing, demold after curing, and perform post-processing (machining, polishing) to finally prepare the antenna frame component.

[0068] The prepreg of the fabric is T300 carbon fiber epoxy material with a layer thickness of 0.25mm.

[0069] The unidirectional tape is made of T800 carbon fiber epoxy material with a layer thickness of 0.12mm.

[0070] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the scope of the technology disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A molding die for a longitudinally and transversely reinforced carbon fiber antenna frame, wherein the antenna frame is a surrounding frame plus two long stringers and then... Two rib-shaped structures; characterized in that, The mold consists of 9 forming molds and a base plate mold (10); the bottom surface of the forming mold is designed with positioning pins for assembling and positioning the forming mold and the base plate mold (10) and for guiding and limiting displacement during pressure curing. The positioning pins are cylindrical pins with a 60° taper, with a diameter of d and a height of h; the base plate mold (10) is an integral flat plate structure, with a length 300mm longer than the antenna frame, a width 160mm wider than the antenna frame, and a thickness of 30mm; 9 positioning pins are provided on the upper surface of the base plate mold (10). The positioning holes correspond one-to-one with the positions of the positioning pins of the nine forming molds. The positioning holes include one circular hole (16), four oblique strip holes (17) and four straight strip holes (18). The oblique strip holes (17) all point to the center of the base plate mold (10). The length of the oblique strip hole (17) is p, the width is q, and the angle between the oblique strip hole (17) and the length direction of the antenna frame (11) is α. The straight strip holes (18) all point to the center of the base plate mold (10). The length of the straight strip hole (18) is u and the width is v. The geometry of the nine molding dies is taken from the geometry of the corresponding stringer (12), rib (13), and frame (14) in the antenna frame (11) and thermal compensation is performed. The compensation coefficient is 1 / [1+(α m -α c )ΔT], where α m Coefficient of thermal expansion of mold material, unit: ×10 -6 / ℃;α c Coefficient of thermal expansion of molding material, unit: ×10 -6 / ℃; ΔT: Temperature difference between the curing temperature of the molding material and the ambient temperature, unit: ℃; The length p of the oblique strip hole (17) satisfies Where d: the diameter of the corresponding positioning pin, in mm; t: the thickness of the corresponding antenna frame stringer or rib, in mm; w: Percentage of material compression during carbon fiber autoclave curing, unit: % α: Angle between the oblique strip aperture and the length direction of the antenna frame, in °; The included angle α of the oblique strip hole (17) satisfies tanα= ,in l : These are the length dimensions of the molding dies at the four corners along the length of the antenna frame, in mm; : These are the length dimensions of the molding dies at the four corners along the width of the antenna frame, in mm; The length u of the straight strip hole (18) satisfies Where d: the diameter of the corresponding positioning pin, in mm; t: the thickness of the corresponding antenna frame stringer or rib, in mm; w: Percentage of material compression during carbon fiber autoclave curing, in units; The diameter of the circular hole (16), the width q of the oblique strip hole (17), and the width v of the straight strip hole (18) are all clearance-fitted with the corresponding positioning pins, with a fit grade of H6; the depths of the circular hole (16), the oblique strip hole (17), and the straight strip hole (18) are all 2mm greater than the height h of the corresponding forming mold positioning pins; The nine forming molds and the base plate mold (10) are all made of 45 steel.

2. A modular fabrication method for a longitudinally and transversely stiffened carbon fiber antenna frame based on the mold described in claim 1, characterized in that... The steps are as follows: Step 1: Clean the molding mold and base plate mold (10) with alcohol, let them air dry at room temperature, and then apply release agent to the surface at least twice, with an interval of at least 10 minutes; Step 2: The web skin (19) of the stringer (12), rib (13), and frame (14) is individually laid on the 9 forming molds, with the layup sequence being [±45°]. （织物） / 90° / 0° / ±45° （织物） / 0°]s, after the layup is completed, pre-compaction treatment is carried out; Step 3: Assemble the 9 molds after layering with the base plate mold (10) by using positioning pins and pin holes; Step 4: Lay the outer skin (20) of the frame (14) onto the 9 molding molds after mold closing, with the layering sequence being 0°4 / 90° / 0°4 / ±45°. （织物） / 0°4 / 90° / 0°4 / [±45° （织物） / 90° / 0° / ±45° （织物） / 0°]s, after the layup is completed, pre-compaction treatment is carried out; Step 5: Lay out the insulating film and breathable felt in sequence, seal in a vacuum bag, put it in an autoclave for heating and curing, demold after curing, and perform post-processing to finally prepare the antenna frame component.

3. The modular fabrication method for a longitudinally and transversely stiffened carbon fiber antenna frame according to claim 2, characterized in that... The prepreg in the layup is T300 carbon fiber epoxy material with a layer thickness of 0.25mm.

4. The modular fabrication method for a longitudinally and transversely stiffened carbon fiber antenna frame according to claim 2, characterized in that... The unidirectional tape in the layup is made of T800 carbon fiber epoxy material with a layer thickness of 0.12 mm.

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