High-precision carbon fiber honeycomb interlayer reflecting surface forming method

Abstract

The invention discloses a high-precision carbon fiber honeycomb interlayer reflecting surface forming method, and belongs to the technical field of reflecting surface forming. According to the invention, the carbon nanotube film is introduced in the preparation stage of the carbon fiber prepreg for modification, and the excellent mechanical properties of the carbon nanotubes endow the modified prepreg with stronger fatigue stress resistance, thereby greatly delaying the generation and expansion of microcracks, powerfully improving the structural reliability of the reflecting surface and prolonging the service life of the reflecting surface. The excellent heat conductivity enables heat to be uniformly transmitted in the prepreg and the whole reflecting surface structure, so that the problem of thermal stress caused by non-uniform heat in traditional curing is effectively relieved, the shape precision and the size stability of the cured reflecting surface are ensured, and the high-precision requirement is met. The electric heating characteristic of the carbon nano tube film is used for direct heating, the temperature of each part of the reflecting surface is accurately controlled by combining accurate setting of parameters and a high-precision temperature monitoring and control system, deformation caused by curing thermal stress is reduced, the forming precision and the internal quality uniformity are remarkably improved, and the requirement of a high-precision application scene is met.

Description

Technical Field

[0001] The invention belongs to the technical field of reflective surface molding, and in particular relates to a high-precision carbon fiber honeycomb sandwich reflective surface molding method. Background Art

[0002] In the fields of aerospace, aviation, communications and radio astronomy, the antenna reflector is a key component, and its performance is crucial to the entire system. Traditional metal reflectors, such as aluminum alloys, are gradually unable to meet the needs of modern technological development. The high density of metal materials makes the reflector structure bulky, which significantly increases the launch cost, reduces the payload and increases fuel consumption in aerospace applications. At the same time, metals are susceptible to corrosion, which affects the service life and reliability of the reflector, and has poor electrical performance in high-frequency bands.

[0003] The rise of carbon fiber composites has brought hope for solving these problems. Carbon fiber has the advantages of high strength, low density, high modulus and good corrosion resistance, and the composite materials made of it have better performance than traditional metal materials. Carbon fiber honeycomb sandwich structure relies on the combination of honeycomb core material and upper and lower carbon fiber panels to effectively reduce weight while ensuring structural strength and stability, which is conducive to achieving high-precision requirements for reflective surfaces. However, the molding of carbon fiber honeycomb sandwich reflective surfaces faces many challenges. The laying process of carbon fiber prepreg is extremely demanding. Slight deviations in the laying angle, sequence and number of layers can easily lead to errors in the precision of the reflective surface shape; the bonding process of honeycomb core material and panel is complicated, and the uniformity of glue layer thickness, bonding strength and bubble removal are directly related to the overall performance of the sandwich structure; improper control of parameters such as temperature, pressure and time in the curing process will cause residual stress inside the composite material, affecting the dimensional accuracy and mechanical properties of the reflective surface. Therefore, the development of high-precision carbon fiber honeycomb sandwich reflective surface molding methods has become a key demand for technological progress in related fields. Summary of the invention

[0004] In view of the above situation, in order to overcome the defects of the prior art, the present invention introduces carbon nanotube film modification in the preparation stage of carbon fiber prepreg, selects molds of specific materials, accurately controls various parameters in the process of laying, bonding and curing, and adopts CNC machining equipment for trimming and non-destructive testing and other innovative measures. The high-precision molding of the carbon fiber honeycomb sandwich reflective surface is achieved, and the problems of traditional metal reflective surfaces such as heavy weight, easy corrosion, poor electrical properties and difficulty in ensuring the molding accuracy of carbon fiber sandwich reflective surfaces are effectively solved. The performance and quality of the reflective surface are significantly improved, so that it can better meet the requirements of aerospace, aviation, communications and radio astronomy for high-precision and high-performance antenna reflective surfaces.

[0005] In order to achieve the above object, the following technical scheme is adopted: The present invention provides a method for forming a high-precision carbon fiber honeycomb sandwich reflective surface, comprising the following steps:

[0006] S1. Select high-strength and high-modulus carbon fiber prepregs, and introduce carbon nanotube film modification during the prepreg preparation stage. First, place the prepreg in a vacuum environment at room temperature to remove air and volatile impurities, then tightly attach the carbon nanotube film to the surface of the prepreg, and use a hot pressing process to initially combine the carbon nanotube film and the prepreg to form a modified prepreg; at the same time, prepare Nomex honeycomb core materials and suitable high-performance structural adhesives;

[0007] S2. Design and manufacture high-precision molds according to the shape and precision requirements of the reflective surface. The mold material is Invar or high-precision aluminum alloy, and the mold release agent is evenly applied on the mold surface;

[0008] S3. Lay the modified carbon fiber prepreg on the mold according to the designed laying angle and sequence, use vacuum bags to assist the laying and control the environmental parameters during the laying process;

[0009] S4. Place the honeycomb core material on the laid carbon fiber panel, evenly apply adhesive on the surface of the honeycomb core material, and then lay another layer of carbon fiber prepreg to form a sandwich structure;

[0010] S5. Carbon nanotube films are laid on the upper and lower surfaces of the sandwich structure as heating elements, and connected to a power supply and a temperature control system to perform heating, heat preservation and cooling operations to achieve curing.

[0011] S6. Take out the solidified reflective surface, remove excess material from the edge, use CNC machining equipment to trim the edge of the reflective surface and refine the surface, and perform non-destructive testing.

[0012] Furthermore, the carbon fiber in the carbon fiber prepreg is T700 / T800 grade, and the prepreg fiber surface density is 150-250g / m 2 The thickness of the carbon nanotube film is 10-50 μm, the diameter of the carbon nanotube is 10-50 nm, the vacuum degree of the prepreg in the vacuum environment is 0.05-0.08 MPa, the processing time is 10-20 min, the temperature of the hot pressing process is 80-100° C., the pressure is 0.1-0.2 MPa, and the time is 5-10 min.

[0013] Furthermore, the honeycomb core size of the Nomex honeycomb core material is 3-6 mm, the core material thickness is 10-30 mm, and the density is 40-80 kg / m 3 .

[0014] Furthermore, the adhesive is an epoxy adhesive, and the tensile shear strength of the adhesive is not less than 20 MPa.

[0015] Furthermore, the mold surface roughness Ra is less than 0.8-1.6 μm, the molding surface accuracy is controlled within ±0.05-0.1 mm, and the release agent coating thickness is about 5-10 μm.

[0016] Furthermore, the plying angles of the carbon fiber panel ply include 0°, ±45°, and 90°, the plying order is [0° / 90° / +45° / -45°]n, n is 8-16 layers, the vacuum degree applied by the vacuum bag during plying is 0.02-0.05MPa, the temperature during the plying process is controlled at 18-25°C, and the relative humidity is controlled at 30%-50%.

[0017] Furthermore, the thickness of the adhesive is controlled at 0.1-0.3 mm.

[0018] Furthermore, the deviation of the carbon nanotube film and the surface adhesion of the sandwich structure does not exceed ±0.5-1mm, and the initial heating power is 50-100W / m 2 The heating rates in different stages are: heating to 80-100℃ at 1-2℃ / min and keeping warm for 30-60min, then heating to 120-150℃ at 2-3℃ / min and keeping warm for 60-120min, and finally cooling to below 60℃ at 1-2℃ / min. The temperature uniformity deviation during the curing process is controlled at ±2-3℃, and the temperature monitoring accuracy is ±0.5-1℃.

[0019] Furthermore, the CNC machining equipment controls the machining accuracy of the reflective surface edge trimming and profile finishing to ±0.05-0.1mm, and the non-destructive testing adopts ultrasonic testing with a testing frequency of 2-5MHz.

[0020] The beneficial effects of the present invention are:

[0021] (1) The present invention introduces carbon nanotube film modification during the preparation stage of carbon fiber prepreg. Carbon nanotubes themselves have excellent mechanical properties, such as high strength and high modulus. After combining them with carbon fiber prepreg in the form of a film, they can significantly enhance the overall mechanical properties of the prepreg. The modified prepreg can effectively resist the effect of fatigue stress and greatly delay the generation and expansion of microcracks, thereby extending the service life of the reflective surface and improving its structural reliability. At the same time, carbon nanotubes have excellent thermal conductivity. In the subsequent curing and molding process, heat can be more evenly transferred inside the prepreg and the entire reflective surface structure. The presence of the carbon nanotube film effectively alleviates the problem of uneven heat distribution in the traditional curing process that easily leads to thermal stress inside the material, so that the reflective surface can maintain higher shape accuracy and dimensional stability after curing and molding, effectively ensuring the high precision requirements of the reflective surface;

[0022] (2) The present invention utilizes the electrothermal properties of the carbon nanotube film to achieve direct heating of the reflective surface. By accurately setting parameters such as the initial heating power, heating rate, insulation time and cooling rate, and combining a high-precision temperature monitoring and control system, the temperature of each part of the reflective surface can be accurately controlled during the entire curing process, effectively reducing the deformation of the reflective surface caused by curing thermal stress, significantly improving the molding accuracy and internal quality uniformity of the reflective surface, and enabling the reflective surface to better meet the needs of high-precision application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a flow chart of a method for forming a high-precision carbon fiber honeycomb sandwich reflective surface.

[0024] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0026] Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to those described herein may be applied to the present invention. The preferred implementation methods and materials described herein are for demonstration purposes only and are not intended to limit the content of this application.

[0027] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are purchased from commercial channels unless otherwise specified.

[0028] Example

[0029] According to the attached Figure 1 A method for forming a high-precision carbon fiber honeycomb sandwich reflective surface comprises the following steps:

[0030] S1. Use high-strength and high-modulus carbon fiber prepreg (such as T700 / T800 grade carbon fiber and suitable epoxy resin system prepreg) to provide good basic mechanical performance support for the reflective surface and ensure that it can withstand complex environmental stress. The prepreg fiber surface density is set at 150-250g / m 2, is the appropriate range obtained through a large number of experiments and theoretical calculations. It can ensure strength while taking into account the weight and cost of the material. The introduction of carbon nanotube film modification is because carbon nanotubes have a unique one-dimensional nanostructure and excellent physical and chemical properties. The prepreg is first placed in a vacuum environment (vacuum degree 0.05-0.08MPa, treatment 10-20min) at room temperature to remove air and volatile impurities in the prepreg and prevent the formation of defects such as bubbles or pores in the subsequent processing process, which affects the quality of the reflective surface. Then the carbon nanotube film (thickness 10-50μm, tube The carbon fiber and carbon nanotube membranes are closely attached to the surface of the prepreg (diameter 10-50nm), and the two are initially combined through hot pressing process (temperature 80-100℃, pressure 0.1-0.2MPa, time 5-10min). The setting of hot pressing process parameters is to achieve good interface bonding without damaging the carbon fiber and carbon nanotube structure, so that the carbon nanotube membrane can effectively play its reinforcing and thermal conductive role, form a modified prepreg, and improve the overall material performance. At the same time, Nomex honeycomb core material (honeycomb core cell size 3-6mm, core material thickness 10-30mm, density 40-80kg / m 3 ), whose light weight and high strength characteristics help to reduce the weight of the reflective surface and maintain structural stability; suitable high-performance structural adhesives (epoxy type, tensile shear strength not less than 20MPa) are used to ensure reliable connection between components;

[0031] S2. Design and manufacture high-precision molds according to the shape and precision requirements of the reflective surface. The mold material is selected from Invar or high-precision aluminum alloy. Invar has an extremely low thermal expansion coefficient, and high-precision aluminum alloy has good processing performance and stability. Both can effectively reduce the deformation of the mold during processing and use. The mold surface roughness Ra is less than 0.8-1.6μm, and the surface accuracy is controlled at ±0.05-0.1mm. Such high-precision requirements are to ensure that the carbon fiber prepreg can accurately fit the mold surface during the laying process, thereby ensuring the final shape accuracy of the reflective surface. The mold release agent (thickness of about 5-10μm) is evenly applied to the mold surface to facilitate smooth demoulding of the reflective surface after molding, avoid damage or deformation to the reflective surface during demoulding, and ensure that the mold release agent will not have adverse effects on the surface quality and subsequent processing of the reflective surface;

[0032] S3. Lay the modified carbon fiber prepreg on the mold according to the designed laying angle (including 0°, ±45°, 90°) and sequence (such as [0° / 90° / +45° / -45°]n, n is 8-16 layers). Different laying angles and sequences are optimized and designed according to the force characteristics of the reflective surface in different directions, which can make the reflective surface have balanced mechanical properties in all directions. When laying, vacuum bags are used to assist the laying and a vacuum degree of 0.02-0.05MPa is applied to further exclude the air between the layers, so that the prepreg fits more closely with the mold surface and each layer of prepreg, reduce porosity, and improve the density and integrity of the reflective surface. During the laying process, the temperature is controlled at 18-25℃ and the relative humidity is controlled at 30%-50%. This is because carbon fiber prepreg is sensitive to environmental temperature and humidity. A suitable temperature and humidity environment helps to maintain the viscosity and operability of the prepreg, ensure the smooth laying process, and reduce the laying error caused by environmental factors.

[0033] S4. Place the honeycomb core material on the laid carbon fiber panel, and ensure that the core material is aligned with the edge of the panel (the error does not exceed ±1-2mm). This is to ensure the symmetry and uniformity of the reflective surface structure and avoid local uneven force due to the offset of the core material. Apply adhesive evenly on the surface of the honeycomb core material (the thickness is controlled at 0.1-0.3mm). The uniform thickness of the adhesive layer can ensure the consistency of the bonding strength and avoid bonding defects caused by too thick or too thin adhesive layer. Use tools such as scrapers to ensure that the thickness of the adhesive layer is uniform, without bubbles and lack of glue, because bubbles and lack of glue will seriously weaken the strength of the bonding structure and affect the overall performance of the reflective surface. The uniform adhesive layer can form a good bond between the honeycomb core material and the carbon fiber panel, effectively transfer stress, and jointly bear the external force on the reflective surface. Then lay another layer of carbon fiber prepreg to form a sandwich structure, so that the reflective surface has better bending and torsion resistance.

[0034] S5. CNT films are laid on the upper and lower surfaces of the sandwich structure as heating elements. The deviation of the carbon nanotube film and the sandwich structure surface fit does not exceed ±0.5-1mm. Tight fit can ensure heating uniformity. Connect the power supply and temperature control system to heat up, keep warm and cool down to achieve curing. The initial heating power is set to 50-100W / m 2, heat up to 80-100℃ at 1-2℃ / min and keep warm for 30-60min. This stage is to make the resin system soften initially and start partial curing reaction. Slow heating can avoid the resin flowing or internal stress concentration due to rapid heating. Then heat up to 120-150℃ at 2-3℃ / min and keep warm for 60-120min. This is the main curing stage of the resin. Higher temperature and longer time can ensure that the resin is fully cured, forming a stable cross-linked structure and giving the reflective surface sufficient strength. Finally, cool down to below 60℃ at 1-2℃ / min. Slow cooling can reduce thermal stress caused by sudden temperature change. The temperature uniformity deviation during curing is controlled at ±2-3℃, and the temperature monitoring accuracy is ±0.5-1℃. Through precise temperature control, the curing process of the entire reflective surface can be carried out synchronously to avoid uneven curing caused by local temperature differences, thereby reducing internal residual stress and improving the molding accuracy and internal quality uniformity of the reflective surface.

[0035] S6. Take out the reflective surface after solidification and remove excess material from the edge. Use CNC machining equipment to trim and refine the edge of the reflective surface. CNC machining equipment has the characteristics of high precision and high degree of automation. The machining accuracy is controlled at ±0.05-0.1mm. It can accurately remove edge burrs, unevenness and other defects caused by the molding process, further improve the dimensional accuracy and surface finish of the reflective surface, make it meet the design requirements, and perform non-destructive testing (using ultrasonic testing with a detection frequency of 2-5MHz). Ultrasonic testing can detect whether there are defects such as stratification and porosity inside without destroying the structure of the reflective surface, and promptly discover hidden quality problems, ensure the high precision and high reliability of the reflective surface, and meet its strict use requirements in aerospace, aviation, communications and other fields.

[0036] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

[0037] The present invention and its implementation methods are described above, which is not restrictive. The drawings are only one of the implementation methods of the present invention, and the actual application is not limited thereto. In short, if ordinary technicians in the field are inspired by it and design methods and embodiments similar to the technical solution without creativity without departing from the purpose of the invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for forming a high-precision carbon fiber honeycomb sandwich reflective surface, characterized in that: The steps include: S1. Select high-strength and high-modulus carbon fiber prepregs, and introduce carbon nanotube film modification during the prepreg preparation stage. First, place the prepreg in a vacuum environment at room temperature to remove air and volatile impurities, then tightly attach the carbon nanotube film to the surface of the prepreg, and use a hot pressing process to initially combine the carbon nanotube film and the prepreg to form a modified prepreg; at the same time, prepare Nomex honeycomb core materials and suitable high-performance structural adhesives; S2. Design and manufacture high-precision molds according to the shape and precision requirements of the reflective surface. The mold material is Invar or high-precision aluminum alloy, and the mold release agent is evenly applied on the mold surface; S3. Lay the modified carbon fiber prepreg on the mold according to the designed laying angle and sequence, use vacuum bags to assist the laying and control the environmental parameters during the laying process; S4. Place the honeycomb core material on the laid carbon fiber panel, evenly apply adhesive on the surface of the honeycomb core material, and then lay another layer of carbon fiber prepreg to form a sandwich structure; S5. Carbon nanotube films are laid on the upper and lower surfaces of the sandwich structure as heating elements, and connected to a power supply and a temperature control system to perform heating, heat preservation and cooling operations to achieve curing. S6. Take out the solidified reflective surface, remove excess material from the edge, use CNC machining equipment to trim the edge of the reflective surface and refine the surface, and perform non-destructive testing.

2. The method for forming a high-precision carbon fiber honeycomb sandwich reflective surface according to claim 1, characterized in that: The carbon fiber in the carbon fiber prepreg is of T700 / T800 grade, and the prepreg fiber surface density is 150-250g / m 2 The thickness of the carbon nanotube film is 10-50 μm, the diameter of the carbon nanotube is 10-50 nm, the vacuum degree of the prepreg in the vacuum environment is 0.05-0.08 MPa, the processing time is 10-20 min, the temperature of the hot pressing process is 80-100° C., the pressure is 0.1-0.2 MPa, and the time is 5-10 min.

3. The method for forming a high-precision carbon fiber honeycomb sandwich reflective surface according to claim 2, characterized in that: The Nomex honeycomb core material has a honeycomb core cell size of 3-6 mm, a core material thickness of 10-30 mm, and a density of 40-80 kg / m 3 .

4. The method for forming a high-precision carbon fiber honeycomb sandwich reflective surface according to claim 3, characterized in that: The adhesive is an epoxy adhesive, and the tensile shear strength of the adhesive is not less than 20 MPa.

5. The method for forming a high-precision carbon fiber honeycomb sandwich reflective surface according to claim 4, characterized in that: The mold surface roughness Ra is less than 0.8-1.6 μm, the molding surface accuracy is controlled within ±0.05-0.1 mm, and the release agent coating thickness is about 5-10 μm.

6. The method for forming a high-precision carbon fiber honeycomb sandwich reflective surface according to claim 5, characterized in that: The plying angles of the carbon fiber panel ply include 0°, ±45°, and 90°, and the plying sequence is [0° / 90° / +45° / -45°]n, where n is 8-16 layers. The vacuum degree applied by the vacuum bag during plying is 0.02-0.05MPa, and the temperature during the plying process is controlled at 18-25°C, and the relative humidity is controlled at 30%-50%.

7. The method for forming a high-precision carbon fiber honeycomb sandwich reflective surface according to claim 6, characterized in that: The thickness of the adhesive is controlled at 0.1-0.3 mm.

8. The method for forming a high-precision carbon fiber honeycomb sandwich reflective surface according to claim 7, characterized in that: The deviation of the carbon nanotube film and the surface adhesion of the sandwich structure does not exceed ±0.5-1mm, and the initial heating power is 50-100W / m 2 The heating rates in different stages are: heating to 80-100℃ at 1-2℃ / min and keeping warm for 30-60min, then heating to 120-150℃ at 2-3℃ / min and keeping warm for 60-120min, and finally cooling to below 60℃ at 1-2℃ / min. The temperature uniformity deviation during the curing process is controlled at ±2-3℃, and the temperature monitoring accuracy is ±0.5-1℃.

9. The method for forming a high-precision carbon fiber honeycomb sandwich reflective surface according to claim 8, characterized in that: The processing accuracy of the CNC processing equipment for edge trimming and profile finishing of the reflective surface is controlled within ±0.05-0.1mm, and the non-destructive testing adopts ultrasonic testing with a testing frequency of 2-5MHz.

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