Preparation method of chopped carbon fiber honeycomb

Abstract

The invention discloses a preparation method of a chopped carbon fiber honeycomb, which comprises the following steps: selecting a metal hexagonal rod and a metal plate with semi-hexagonal grooves arranged in parallel as a honeycomb preparation mold, paving a chopped carbon fiber felt fully infiltrated with an epoxy resin glue solution in a mold adhered with a polytetrafluoroethylene adhesive tape, and carrying out hot pressing; and after cutting, soaking in a diluted epoxy resin glue solution, and curing to prepare the chopped carbon fiber honeycomb. According to the method, the carbon fiber honeycomb can be prepared through one-step hot press molding, the preparation process is simple and controllable, the efficiency is high, before the carbon fiber felt is soaked in the epoxy resin glue solution, the carbon fiber felt is subjected to desizing treatment through an ultrasonic method, then the chopped carbon fiber felt coated with the glue solution is clamped in a polytetrafluoroethylene film, and pressure is applied; the out-of-plane compression strength and the shear strength of the prepared carbon fiber honeycomb are favorably improved. The carbon fiber honeycomb block prepared by the method disclosed by the invention is relatively low in density and relatively high in strength, and is expected to meet higher requirements of novel aircrafts on material system bearing efficiency and environmental adaptability.

Description

Technical Field

[0001] The present invention relates to a preparation method of fiber-reinforced resin-based honeycomb, belonging to the technical field of carbon fiber honeycomb, and specifically to a preparation method of chopped carbon fiber honeycomb. Background Art

[0002] Honeycomb structure materials are materials with a honeycomb shape made of balsa wood, metal, polymer, composite materials, etc., inspired by the natural honeycomb. The honeycomb combines with thin and strong panels to form a honeycomb sandwich structure, which is widely used in the fields of aerospace, rail transit, etc. due to its light weight, high strength and rigidity, good impact resistance, good sound insulation and heat insulation performance, and designability. Common honeycomb structure materials include metal honeycomb, fiber-reinforced polymer honeycomb, paper honeycomb, etc. Among them, the chopped carbon fiber honeycomb core has the advantages of low cost, low density, corrosion resistance, high strength, easy preparation of small apertures, etc., and can form a full-carbon honeycomb sandwich structure with a carbon fiber panel, with consistent thermal expansion coefficients and higher dimensional stability, and is expected to meet the higher requirements of the new generation of aerospace aircraft for the material system structure bearing rate and environmental adaptability. Therefore, the demand for chopped carbon fiber honeycomb in related fields is becoming increasingly urgent.

[0003] Chopped carbon fiber-reinforced resin-based honeycomb currently faces problems such as high honeycomb density (≥80 kg / m 3 ), low specific strength, and high preparation cost. The main reasons include: the chopped carbon fiber fabric has a relatively high porosity and is difficult to be fully infiltrated by the resin; the bonding strength between the chopped carbon fiber and the resin is relatively low, and interface failure is likely to occur; the preparation methods of chopped carbon fiber honeycomb, such as 3D printing method, have defects such as high equipment cost, insufficient bonding strength between honeycomb layers, and uneven material distribution.

[0004] In view of the above problems, it is necessary to develop a simple and feasible preparation method with low equipment cost, high honeycomb yield, and capable of fully improving the mechanical strength of chopped carbon fiber honeycomb. Summary of the Invention

[0005] In view of the above problems, the purpose of the present invention is to provide a preparation method of chopped carbon fiber honeycomb to solve the problems of high preparation cost, complex preparation process, low strength and high density of the obtained honeycomb in the existing preparation methods.

[0006] For the above purpose, the present invention first provides a preparation method of chopped carbon fiber honeycomb, including the following steps:

[0007] (1) Select a regular hexagonal metal hexagonal bar and a metal plate with parallel arranged semi-hexagonal grooves as the honeycomb preparation mold, and paste polytetrafluoroethylene tape on the mold surface;

[0008] (2) Cut multiple pieces of chopped carbon fiber felts, soak the chopped carbon fiber felts in an organic solvent and perform ultrasonic treatment to remove the resin coating on the surface of the chopped carbon fibers;

[0009] (3) Coat the surface of the chopped carbon fiber felts after removing the resin coating obtained in step (2) with an epoxy resin glue solution. Subsequently, place each chopped carbon fiber felt into a polytetrafluoroethylene film and apply pressure to ensure that the epoxy resin flows sufficiently to ensure that the chopped carbon fibers are evenly wetted;

[0010] (4) Lay the chopped carbon fiber felts coated with epoxy resin obtained in step (3) in a mold composed of metal hexagonal bars and metal plates for hot pressing. After the epoxy resin cures, remove the mold to obtain a honeycomb block with the inner size of the cell being the same as the outer size l of the metal hexagonal bar;

[0011] (5) Use a cutting machine to cut the honeycomb block to a specific height to obtain a honeycomb with the required height;

[0012] (6) Immerse the cut honeycomb in a diluted epoxy resin glue solution, then take it out and place it in an oven for drying to remove the diluent and cure the resin at the same time, finally obtaining a chopped carbon fiber honeycomb.

[0013] In an embodiment of the present invention, the side length of the regular hexagon of the metal hexagonal bar described in step (1) is 1.6 mm to 20 mm. After pasting a polytetrafluoroethylene tape on the surface of the metal hexagonal bar, the outer size l of the regular hexagon of the metal hexagonal bar is the inner size of the honeycomb cell; the side length of the semi-hexagonal groove in the metal plate is slightly larger than the side length of the regular hexagon of the metal hexagonal bar, so that the thickness t of the honeycomb cell wall is 0.05 mm to 1 mm.

[0014] In an embodiment of the present invention, the length of the fibers in the chopped carbon fiber felts described in step (2) is 3 mm - 6 mm, and the fibers are evenly distributed in the chopped carbon fiber felts.

[0015] In an embodiment of the present invention, the areal density of the chopped carbon fiber felts described in step (2) is 8 g / m 2 ~50 g / m 2 , preferably 10 - 50 g / m 2 , more preferably 20 - 50 g / m 2 , even more preferably 30 - 50 g / m 2 .

[0016] In an embodiment of the present invention, the organic solvent described in step (2) includes at least one of acetone, methanol, ethanol, dimethyl sulfoxide (DMSO), and dimethylformamide (DMF).

[0017] In one embodiment of the present invention, in step (2), the temperature of the ultrasonic treatment is 20 to 60 °C, the ultrasonic power is 50 W to 500 W, and the treatment time is 12 h to 48 h.

[0018] In one embodiment of the present invention, in step (3), the mass of the epoxy resin adhesive solution coated on each chopped carbon fiber felt is 40% to 250% of the mass of the chopped carbon fiber felt, preferably 70 to 250%, and more preferably 80 to 230%.

[0019] In one embodiment of the present invention, in step (3), the epoxy resin adhesive solution includes an epoxy resin and a curing agent. The epoxy resin includes at least one of glycidyl ether type, glycidyl ester type, glycidyl amine type, and alicyclic epoxy resin. The curing agent includes at least one of amine type, synthetic resin type, addition type, and catalytic type curing agents. The mass ratio of the epoxy resin to the curing agent is 1:1 to 3:1.

[0020] In one embodiment of the present invention, in step (3), the pressing is carried out at room temperature (20 to 30 °C), the applied pressure is 5 MPa to 15 MPa, and the pressing time is 5 to 60 s.

[0021] In one embodiment of the present invention, in step (4), during the hot pressing process, the hot pressing temperature is 50 to 100 °C, the hot pressing time is 2 to 5 h, and the pressure is 5 to 15 MPa.

[0022] In one embodiment of the present invention, in step (6), the diluted epoxy resin adhesive solution includes an epoxy resin, a curing agent, and a diluent. The sum of the mass fractions of the epoxy resin and the curing agent is 5% to 50%, preferably 5 to 30%, more preferably 6 to 20%, and even more preferably 8 to 18%.

[0023] In one embodiment of the present invention, in step (6), the epoxy resin includes at least one of glycidyl ether type, glycidyl ester type, glycidyl amine type, and alicyclic epoxy resin. The curing agent includes at least one of amine type, synthetic resin type, addition type, and catalytic type curing agents. The mass ratio of the epoxy resin to the curing agent is 1:1 to 3:1.

[0024] In one embodiment of the present invention, in step (6), the diluent is ethanol or ethyl acetate.

[0025] In one embodiment of the present invention, in step (6), ensure that the honeycomb is completely immersed in the diluted epoxy resin adhesive solution during soaking, and the soaking time is 1 min to 5 min.

[0026] In an embodiment of the present invention, in step (6), the drying temperature is 40°C to 70°C, and the drying time is 10 to 60 minutes.

[0027] The present invention also discloses a chopped carbon fiber honeycomb prepared by the above method.

[0028] Beneficial effects:

[0029] (1) In the present invention, a metal hexagonal bar and a metal plate with parallel semi-hexagonal grooves are selected as the honeycomb preparation mold. The chopped carbon fiber felt fully infiltrated with epoxy resin adhesive is placed in the mold pasted with polytetrafluoroethylene tape and hot-pressed. After cutting, it is soaked in diluted epoxy resin adhesive, and a chopped carbon fiber honeycomb is prepared after curing. The carbon fiber honeycomb can be formed by one-step hot pressing using the method of the present invention. The preparation process is simple and controllable, and the efficiency is high.

[0030] (2) The present invention selects a low-density chopped carbon fiber felt as the raw material for preparing the chopped carbon fiber honeycomb. Compared with chopped carbon fiber filaments, the chopped carbon fibers in the carbon fiber felt are more evenly distributed, the honeycomb performance is more stable, and the use of chopped carbon fiber felt to prepare the honeycomb does not require prior dispersion of the carbon fibers, reducing the preparation time.

[0031] (3) Before infiltrating the carbon fiber felt with epoxy resin adhesive, it is first desized by ultrasonic method to remove the epoxy resin on the surface of the chopped carbon fiber felt, which helps to improve the wettability of the chopped carbon fiber, and then improve the bonding strength between the chopped carbon fiber and the epoxy resin, thereby improving the mechanical properties of the prepared chopped carbon fiber.

[0032] (4) After applying the epoxy resin adhesive, the chopped carbon fiber felt coated with the adhesive is clamped in a polytetrafluoroethylene film and pressurized, so that the epoxy resin can be extruded from the resin-rich area in the chopped carbon fiber felt to the resin-deficient area, reducing the amount of epoxy resin used while making the resin more evenly distributed in the chopped carbon fiber felt, thereby improving the out-of-plane compressive strength and shear strength of the prepared carbon fiber honeycomb.

[0033] (5) Before hot-pressing the carbon fiber felt, an ultra-thin polytetrafluoroethylene tape is pasted on the surface of the hexagonal metal bar and the upper and lower metal plates, and then the carbon fiber felt is placed in it for hot-pressing. This treatment method helps to improve the demolding efficiency and reduce the honeycomb pore wall breakage rate. Compared with using a demolding agent for demolding, the demolding efficiency is higher, and the polytetrafluoroethylene tape has high-temperature resistance and can be reused, saving costs.

[0034] (6) The density of the carbon fiber honeycomb block prepared by the method of the present invention is 32 to 48 kg / m 3 , the out-of-plane compressive strength can be as high as 2.9 MPa, the shear strength in the L direction is as high as 1.9 MPa, and the shear strength in the W direction is as high as 1.3 MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a flowchart for preparing short-cut carbon fiber honeycombs according to an embodiment of the present invention.

[0036] Figure 2 This is a schematic structural view of the short-cut carbon fiber honeycombs prepared according to an embodiment of the present invention. In the figure, L represents the longitudinal direction of the honeycomb, W represents the transverse direction of the honeycomb, T represents the height of the honeycomb, l represents the side length of the honeycomb core hole grid, and t represents the thickness of the honeycomb single-layer hole wall. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The present invention will be further explained in combination with the embodiments of honeycomb sample preparation and testing. The following embodiments are only for illustration and do not limit the protection scope of the present invention in any way. The materials used in the examples can be purchased on the market. The following examples achieve the purpose of the present invention.

[0038] The epoxy resin adhesive used in the embodiments and comparative examples of the present invention includes epoxy resin and curing agent, both of which are purchased from Degu Carbon Fiber Composite CFRP. The epoxy resin model is D99A, and the curing agent model is D99B. The mass ratio of epoxy resin to curing agent in the epoxy resin adhesive is 3:1.

[0039] Performance Test:

[0040] According to the test standards "Test Method for Flat Compression Performance of Sandwich Structures or Cores (GB / T 1453-2005)" and "Test Method for Shear Performance of Sandwich Structures or Cores (GB / T 1455-2005)", the out-of-plane compression and in-plane shear performance tests of the short-cut carbon fiber honeycombs prepared in the embodiments and comparative examples are carried out, and the fixture moving speed is set to 1 mm / min.

[0041] Example 1

[0042] Cut the areal density of 30 g / m 228 pieces of chopped carbon fiber felts, sized 25 cm × 10 cm. Immerse the chopped carbon fiber felts into acetone solution, place them in an ultrasonic machine and heat to 40 °C, and ultrasonically vibrate for 24 h to remove the resin coating on the surface of the chopped carbon fibers. Use deionized water to rinse the acetone and impurities on the surface of the chopped carbon fiber felts. After drying, manually coat 1.5 g of epoxy resin glue on the surface of each chopped carbon fiber felt. Put the chopped carbon fiber felts coated with epoxy resin glue into a polytetrafluoroethylene film for pressing, with a pressure of 10 MPa and a pressing time of 10 s, so that the epoxy resin further flows to fully infiltrate the carbon fibers. Subsequently, lay the chopped carbon fiber felts into a mold composed of a metal hexagonal bar pasted with polytetrafluoroethylene tape and a metal plate with a semi-hexagonal groove. Among them, the side length of the regular hexagonal groove of the metal hexagonal bar is 2.62 mm, the thickness of the polytetrafluoroethylene tape is 0.13 mm, and the side length of the semi-hexagonal groove in the metal plate is 2.90 mm. Then transfer the mold to a hot press, heat to 60 °C, apply a pressure of 10 MPa, keep warm for 4 h, and after cooling to room temperature, remove the metal hexagonal bar and the upper and lower metal plates to obtain a honeycomb block with a length of 18 cm, a width of 10 cm, and a height of 7 cm. Slice the honeycomb block, and after slicing, the size of the honeycomb block is 18 cm in length, 1 cm in width, and 7 cm in height, and the measured density is 43 kg / m 3 . Mix 20 g of epoxy resin D99A and curing agent D99B by mass ratio of 3:1, and then pour them into 180 g of ethyl acetate to prepare a diluted epoxy resin glue. Immerse the honeycomb block into the diluted epoxy resin glue for 1 min to ensure that the honeycomb block is completely immersed. Then take out the honeycomb block and put it into an oven and heat at 60 °C for 30 min to obtain a honeycomb block with a density of 48 kg / m 3 , with an inner size of 2.75 mm for the cell and a single-layer cell wall thickness of 0.08 mm for the regular hexagonal cell honeycomb block.

[0043] Example 2

[0044] Cut the surface density of 50 g / m 228 pieces of chopped carbon fiber felts, sized 25 cm × 10 cm. Immerse the chopped carbon fiber felts into acetone solution, place them in an ultrasonic machine and heat to 40 °C, and ultrasonically vibrate for 24 h to remove the resin coating on the surface of the chopped carbon fiber. Use deionized water to rinse the acetone and impurities on the surface of the chopped carbon fiber felts. After drying, manually coat 1.0 g of epoxy resin adhesive solution on the surface of each chopped carbon fiber felt. Put the chopped carbon fiber felts coated with epoxy resin adhesive solution into a polytetrafluoroethylene film for pressing, with a pressure of 10 MPa and a pressing time of 10 s, so that the epoxy resin further flows to fully infiltrate the carbon fiber. Subsequently, lay the chopped carbon fiber felts into a mold composed of a metal hexagonal bar pasted with polytetrafluoroethylene tape and a metal plate with a semi-hexagonal groove. The side length of the regular hexagonal groove of the metal hexagonal bar is 2.62 mm, the thickness of the polytetrafluoroethylene tape is 0.13 mm, and the side length of the semi-hexagonal groove is 2.90 mm. Then transfer the mold to a hot press, heat to 60 °C, apply a pressure of 10 MPa, keep warm for 4 h, and after cooling to room temperature, remove the metal hexagonal bar and the upper and lower metal plates to obtain a honeycomb block with a length of 18 cm, a width of 10 cm, and a height of 7 cm. Slice the honeycomb block, and the size of the sliced honeycomb block is 18 cm in length, 1 cm in width, and 7 cm in height, and the measured density is 44 kg / m 3 . Mix 16 g of epoxy resin D99A and curing agent D99B in a mass ratio of 3:1, and then pour them into 184 g of ethyl acetate to prepare a diluted epoxy resin. Immerse the honeycomb block into the diluted epoxy resin for 1 min to ensure that the honeycomb block is completely immersed. Subsequently, take out the honeycomb block and put it into an oven and heat at 60 °C for 30 min to obtain a honeycomb block with a density of 48 kg / m 3 , with an inner size of 2.75 mm for the cell and a single-layer cell wall thickness of 0.14 mm for the regular hexagonal cell honeycomb block.

[0045] Example 3

[0046] Cut the chopped carbon fiber felts with a surface density of 40 g / m 212 pieces of chopped carbon fiber felt with a size of 24 cm × 10 cm were soaked in an acetone solution, placed in an ultrasonic machine and heated to 40 °C, and ultrasonically vibrated for 24 h to remove the resin coating on the surface of the chopped carbon fiber. The surface of the chopped carbon fiber felt was rinsed with deionized water to remove acetone and impurities. After drying, 2.2 g of epoxy resin sizing was manually coated on the surface of each piece of chopped carbon fiber felt. The chopped carbon fiber felt coated with epoxy resin sizing was placed in a polytetrafluoroethylene film for pressing, with a pressure of 10 MPa and a pressing time of 10 s, so that the epoxy resin further flowed to fully infiltrate the carbon fiber. Subsequently, the chopped carbon fiber felt was laid in a mold composed of a metal hexagonal bar and a metal plate with a semi-hexagonal groove after pasting polytetrafluoroethylene tape. The side length of the regular hexagonal groove of the metal hexagonal bar was 5.77 mm, the thickness of the polytetrafluoroethylene tape was 0.13 mm, and the side length of the semi-hexagonal groove was 6.05 mm. Subsequently, the mold was transferred to a hot press, heated to 60 °C, pressed at 10 MPa, and kept warm for 4 h. After cooling to room temperature, the metal hexagonal bar and the upper and lower metal plates were removed to obtain a honeycomb block with a length of 18 cm, a width of 10 cm, and a height of 6 cm. The honeycomb block was sliced, and the size of the sliced honeycomb block was 18 cm in length, 1 cm in width, and 6 cm in height, and the measured density was 28 kg / m 3 . Epoxy resin D99A with a total mass of 32 g and curing agent D99B were mixed at a mass ratio of 3:1 and then poured into 168 g of ethyl acetate to prepare a diluted epoxy resin. The honeycomb block was immersed in the diluted epoxy resin for 1 min to ensure that the honeycomb block was completely immersed. Subsequently, the honeycomb block was taken out and placed in an oven and heated at 60 °C for 30 min to obtain a density of 32 kg / m 3 , a regular hexagonal cell honeycomb block with an inner cell size of 5.9 mm and a single-layer cell wall thickness of 0.14 mm.

[0047] Example 4

[0048] Cut the surface density of 50 g / m 212 pieces of chopped carbon fiber felt with dimensions of 24 cm × 10 cm were immersed in acetone solution, placed in an ultrasonic machine and heated to 40 °C, and ultrasonically oscillated for 24 h to remove the resin coating on the surface of the chopped carbon fiber. The surface of the chopped carbon fiber felt was rinsed with deionized water to remove acetone and impurities. After drying, 1.9 g of epoxy resin adhesive was manually coated on the surface of each piece of chopped carbon fiber felt. The chopped carbon fiber felt coated with epoxy resin adhesive was placed in a polytetrafluoroethylene film and pressurized at a pressure of 10 MPa for 10 s to allow the epoxy resin to flow further to fully infiltrate the carbon fiber. Subsequently, the chopped carbon fiber felt was laid in a mold composed of a metal hexagonal bar and a metal plate with a semi-hexagonal groove after pasting polytetrafluoroethylene tape. The side length of the regular hexagon of the metal hexagonal bar was 5.77 mm, the thickness of the polytetrafluoroethylene tape was 0.13 mm, and the side length of the semi-hexagonal groove was 6.05 mm. Subsequently, the mold was transferred to a hot press, heated to 60 °C, pressurized at 10 MPa, and kept warm for 4 h. After cooling to room temperature, the metal hexagonal bar and the upper and lower metal plates were removed to obtain a honeycomb block with a length of 18 cm, a width of 10 cm, and a height of 6 cm. The honeycomb block was sliced, and the size of the sliced honeycomb block was 18 cm in length, 10 cm in width, and 6 cm in height, and the measured density was 29 kg / m 3 . Epoxy resin D99A with a total mass of 24 g and curing agent D99B were mixed at a mass ratio of 3:1 and then poured into 176 g of ethyl acetate to prepare a diluted epoxy resin. The honeycomb block was immersed in the diluted epoxy resin for 1 min to ensure that the honeycomb block was completely immersed. Subsequently, the honeycomb block was taken out and placed in an oven and heated at 60 °C for 30 min to obtain a honeycomb block with a density of 32 kg / m 3 and a regular hexagonal cell honeycomb block with an inner cell size of 5.9 mm and a single-layer cell wall thickness of 0.18 mm.

[0049] Comparative Example 1

[0050] Cut the surface density of 30 g / m 228 pieces of chopped carbon fiber felts, sized 25 cm × 10 cm. Immerse the chopped carbon fiber felts into acetone solution, place them in an ultrasonic machine and heat to 40 °C, and ultrasonically vibrate for 24 h to remove the resin coating on the surface of the chopped carbon fiber. Use deionized water to rinse the acetone and impurities on the surface of the chopped carbon fiber felts. After drying, manually coat 1.5 g of epoxy resin adhesive on the surface of each chopped carbon fiber felt. Then immediately place the chopped carbon fiber felts coated with epoxy resin adhesive into a mold composed of a metal hexagonal bar pasted with polytetrafluoroethylene tape and a metal plate with a semi-hexagonal groove. The side length of the regular hexagonal groove of the metal hexagonal bar is 2.62 mm, the thickness of the polytetrafluoroethylene tape is 0.13 mm, and the side length of the semi-hexagonal groove in the metal plate is 2.90 mm. Transfer the mold to a hot press, heat to 60 °C, apply a pressure of 10 MPa, keep warm for 4 h, and after cooling to room temperature, remove the metal hexagonal bar and the upper and lower metal plates to obtain a honeycomb block with a length of 18 cm, a width of 10 cm, and a height of 7 cm. Slice the honeycomb block. After slicing, the size of the honeycomb block is 18 cm in length, 1 cm in width, and 7 cm in height, and the measured density is 43 kg / m 3 . Mix 20 g of epoxy resin D99A and curing agent D99B in a mass ratio of 3:1, and then pour them into 180 g of ethyl acetate to prepare a diluted epoxy resin. Immerse the honeycomb block into the diluted epoxy resin for 1 min to ensure that the honeycomb block is completely immersed. Then take out the honeycomb block and place it in an oven and heat at 60 °C for 30 min to obtain a honeycomb block with a density of 48 kg / m 3 , with a regular hexagonal cell size of 2.75 mm inside the cell and a single-layer cell wall thickness of 0.08 mm.

[0051] Comparative Example 2

[0052] Cut the surface density of 30 g / m 228 pieces of chopped carbon fiber felts, with dimensions of 25 cm × 10 cm. Immerse the chopped carbon fiber felts into acetone solution, place them in an ultrasonic machine and heat to 40 °C, and perform ultrasonic oscillation for 30 min to remove the resin coating on the surface of the chopped carbon fiber. Use deionized water to rinse the acetone and impurities on the surface of the chopped carbon fiber felts. After drying, manually coat 1.5 g of epoxy resin glue on the surface of each chopped carbon fiber felt. Put the chopped carbon fiber felts coated with epoxy resin glue into a polytetrafluoroethylene film and apply pressure at room temperature, with a pressure of 10 MPa and a pressure application time of 10 s, so that the epoxy resin further flows to fully infiltrate the carbon fiber. Subsequently, lay the chopped carbon fiber felts coated with epoxy resin and curing agent into a mold composed of a metal hexagonal bar pasted with polytetrafluoroethylene tape and a metal plate with a semi-hexagonal groove. The side length of the regular hexagonal groove of the metal hexagonal bar is 2.62 mm, the thickness of the polytetrafluoroethylene tape is 0.13 mm, and the side length of the semi-hexagonal groove in the metal plate is 2.90 mm. Subsequently, transfer the mold to a hot press, heat to 60 °C, apply a pressure of 10 MPa, keep warm for 4 h, and after cooling to room temperature, remove the metal hexagonal bar and the upper and lower metal plates to obtain a honeycomb block with a length of 18 cm, a width of 10 cm, and a height of 7 cm. Slice the honeycomb block. After slicing, the size of the honeycomb block is 18 cm in length, 1 cm in width, and 7 cm in height, and the measured density is 43 kg / m 3 . Mix 20 g of epoxy resin D99A and curing agent D99B in a mass ratio of 3:1, and then pour them into 180 g of ethyl acetate to prepare diluted epoxy resin. Immerse the honeycomb block into the diluted epoxy resin for 1 min to ensure that the honeycomb block is completely immersed. Subsequently, take out the honeycomb block and put it into an oven and heat at 60 °C for 30 min to obtain a honeycomb block with a density of 48 kg / m 3 , with an inner size of the cell of 2.75 mm and a single-layer cell wall thickness of 0.08 mm of a regular hexagonal cell honeycomb block.

[0053] Comparative Example 3

[0054] Cut the surface density of 30 g / m 228 pieces of chopped carbon fiber felts, sized 25 cm × 10 cm. Immerse the chopped carbon fiber felts into acetone solution, place them in an ultrasonic machine and heat to 40 °C, and ultrasonically vibrate for 24 h to remove the resin coating on the surface of the chopped carbon fiber. Use deionized water to rinse the acetone and impurities on the surface of the chopped carbon fiber felts. After drying, manually coat 1.5 g of epoxy resin adhesive solution on the surface of each chopped carbon fiber felt. Put the chopped carbon fiber felts coated with epoxy resin adhesive solution into a polytetrafluoroethylene film and apply pressure at room temperature, with a pressure of 10 MPa and a pressing time of 10 s, so that the epoxy resin further flows to fully infiltrate the carbon fiber. Subsequently, lay the chopped carbon fiber felts coated with epoxy resin and curing agent into a mold composed of a metal hexagonal bar pasted with polytetrafluoroethylene tape and a metal plate with a semi-hexagonal groove. The side length of the regular hexagonal groove of the metal hexagonal bar is 2.62 mm, the thickness of the polytetrafluoroethylene tape is 0.13 mm, and the side length of the semi-hexagonal groove in the metal plate is 2.90 mm. Then transfer the mold to a hot press, heat to 60 °C, apply a pressure of 2 MPa, keep warm for 4 h, cool to room temperature, and remove the metal hexagonal bar and the upper and lower metal plates to obtain a honeycomb block with a length of 18 cm, a width of 10 cm, and a height of 7 cm. Slice the honeycomb block. After slicing, the size of the honeycomb block is 18 cm in length, 1 cm in width, and 7 cm in height, and the measured density is 43 kg / m 3 . Mix 20 g of epoxy resin D99A and curing agent D99B in a mass ratio of 3:1, and then pour them into 180 g of ethyl acetate to prepare a diluted epoxy resin. Immerse the honeycomb block into the diluted epoxy resin for 1 min to ensure that the honeycomb block is completely immersed. Then take out the honeycomb block and put it into an oven and heat at 60 °C for 30 min to obtain a honeycomb block with a density of 48 kg / m 3 , with an inner size of 2.75 mm for the cell and a single-layer cell wall thickness of 0.08 mm for the regular hexagonal cell honeycomb block.

[0055] Comparative Example 4

[0056] Cut the surface density of 30 g / m 228 pieces of chopped carbon fiber felts, sized 25 cm × 10 cm. Immerse the chopped carbon fiber felts into acetone solution, place them in an ultrasonic machine and heat to 40 °C, and ultrasonically vibrate for 24 h to remove the resin coating on the surface of the chopped carbon fiber. Use deionized water to rinse the acetone and impurities on the surface of the chopped carbon fiber felts. After drying, manually coat 1.5 g of epoxy resin glue solution on the surface of each chopped carbon fiber felt. Put the chopped carbon fiber felts coated with epoxy resin glue solution into a polytetrafluoroethylene film and apply pressure at room temperature, with a pressure of 10 MPa and a pressing time of 10 s, so that the epoxy resin further flows to fully infiltrate the carbon fiber. Subsequently, lay the chopped carbon fiber felts coated with epoxy resin and curing agent into a mold composed of a metal hexagonal bar pasted with polytetrafluoroethylene tape and a metal plate with a semi-hexagonal groove. The side length of the regular hexagonal groove of the metal hexagonal bar is 2.62 mm, the thickness of the polytetrafluoroethylene tape is 0.13 mm, and the side length of the semi-hexagonal groove in the metal plate is 2.90 mm. Then transfer the mold to a hot press, heat to 150 °C, apply a pressure of 10 MPa, keep warm for 1 h, and after cooling to room temperature, remove the metal hexagonal bar and the upper and lower metal plates to obtain a honeycomb block with a length of 18 cm, a width of 10 cm, and a height of 7 cm. Slice the honeycomb block, and the size of the sliced honeycomb block is 18 cm in length, 1 cm in width, and 7 cm in height. Measure the density to be 43 kg / m 3 . Mix 20 g of epoxy resin D99A and curing agent D99B in a mass ratio of 3:1, and then pour them into 180 g of ethyl acetate to prepare a diluted epoxy resin. Immerse the honeycomb block into the diluted epoxy resin for 1 min to ensure that the honeycomb block is completely immersed. Then take out the honeycomb block and put it into an oven and heat at 60 °C for 30 min to obtain a honeycomb block with a density of 48 kg / m 3 , with a regular hexagonal cell honeycomb block having an inner cell size of 2.75 mm and a single-layer cell wall thickness of 0.08 mm.

[0057] Perform out-of-plane compression and in-plane shear performance tests on the chopped carbon fiber honeycombs prepared in Examples 1 to 4 and Comparative Examples 1 to 4. The results are shown in Table 1.

[0058] Table 1 Test results of out-of-plane compression and in-plane shear performance of chopped carbon fiber honeycombs prepared in Examples 1 to 4 and Comparative Examples 1 to 4

[0059]

[0060] Note: The L direction represents the longitudinal direction of the honeycomb block, and the W direction represents the transverse direction of the honeycomb block, as Figure 2 shown.

[0061] As can be seen from Table 1, during the preparation of the chopped carbon fiber honeycomb, ultrasonic pretreatment, the pressing process, and the hot pressing process will all have a great impact on the performance of the finally prepared carbon fiber honeycomb, and the specific manifestations are as follows: By comparing Example 1 with Comparative Example 1, it can be seen that after manually coating the chopped carbon fiber felt with epoxy resin glue, if the pressing link is missing, it will cause the uneven distribution of epoxy resin on the surface of the chopped carbon fiber felt, resulting in a decrease in the mechanical strength of the honeycomb; By comparing Example 1 with Comparative Example 2, it can be seen that the purpose of the ultrasonic treatment in the present invention is to remove the resin coating on the surface of the chopped carbon fiber. If the ultrasonic time is too short, the resin coating on the surface of the chopped carbon fiber cannot be effectively removed, which will reduce the bonding strength between the epoxy resin and the chopped carbon fiber, and then result in a lower mechanical strength of the chopped carbon fiber honeycomb; By comparing Example 1 with Comparative Example 3, it can be seen that if the pressure applied during the hot pressing process of the honeycomb is too small, the structure of the chopped carbon fiber honeycomb will not be dense, and it is difficult to fully exert the strengthening effect of the chopped carbon fiber, resulting in a lower mechanical strength of the chopped carbon fiber honeycomb; By comparing Example 1 with Comparative Example 4, it can be seen that too high a hot pressing temperature will cause thermal stress to be generated inside the composite material, resulting in internal damage to the material and affecting the mechanical properties of the chopped carbon fiber honeycomb.

[0062] The embodiments provided above are not intended to limit the scope covered by the present invention, nor are the described steps intended to limit their execution order. Obvious improvements made by those skilled in the art to the present invention in combination with the existing common general knowledge also fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a chopped carbon fiber honeycomb, characterized in that: The following steps are involved: (1) Selecting a regular hexagonal metal hexagonal rod and a metal plate with parallel semi-hexagonal grooves as a honeycomb preparation mold, and pasting polytetrafluoroethylene tape on the mold surface; (2) cutting a plurality of chopped carbon fiber felts, immersing the chopped carbon fiber felts in an organic solvent and performing ultrasonic treatment to remove the resin coating on the surface of the chopped carbon fiber; (3) coating the surface of the chopped carbon fiber felt obtained in step (2) with epoxy resin glue after removing the resin coating, and then placing each chopped carbon fiber felt in a polytetrafluoroethylene film and applying pressure to allow the epoxy resin to flow fully to ensure that the chopped carbon fibers are evenly infiltrated; (4) placing the chopped carbon fiber felt coated with epoxy resin obtained in step (3) in a mold consisting of a metal hexagonal rod and a metal plate for hot pressing, and removing the mold after the epoxy resin is cured to obtain a honeycomb block with a cell inner size consistent with an outer size l of the metal hexagonal rod; (5) Using a cutting machine to cut the honeycomb block to a specific height to obtain a honeycomb of the required height; (6) The cut honeycomb is immersed in a diluted epoxy resin adhesive solution, then taken out and placed in an oven for drying to remove the diluent and solidify the resin, thereby finally obtaining a chopped carbon fiber honeycomb.

2. The preparation method according to claim 1, characterized in that: The side length of the regular hexagon of the metal hexagonal rod described in step (1) is 1.6 mm to 20 mm. After the polytetrafluoroethylene tape is attached to the surface of the metal hexagonal rod, the outer dimension l of the regular hexagon of the metal hexagonal rod is the inner dimension of the honeycomb cell.

3. The preparation method according to claim 1, characterized in that: The length of the fibers in the chopped carbon fiber felt in step (2) is 3 mm to 6 mm, and the surface density of the chopped carbon fiber felt is 8 g / m 2 ~50g / m 2 .

4. The preparation method according to claim 1, characterized in that: The organic solvent described in step (2) includes at least one of acetone, methanol, ethanol, dimethyl sulfoxide, and dimethylformamide. The temperature of the ultrasonic treatment is 20 to 60° C., the ultrasonic power is 50 W to 500 W, and the treatment time is 12 h to 48 h.

5. The preparation method according to claim 1, characterized in that: The mass of the epoxy resin adhesive coated on each chopped carbon fiber felt described in step (3) is 40% to 250% of the mass of the chopped carbon fiber felt, and the epoxy resin adhesive comprises an epoxy resin and a curing agent, wherein the epoxy resin comprises at least one of glycidyl ethers, glycidyl esters, glycidyl amines and alicyclic epoxy resins, and the curing agent comprises at least one of amines, synthetic resins, addition-type and catalytic-type curing agents, and the mass ratio of epoxy resin to curing agent is 1:1 to 3:

1.

6. The preparation method according to claim 1, characterized in that: The pressure during pressurization is 5MPa to 15MPa, and the pressurization time is 5 to 60s.

7. The preparation method according to claim 1, characterized in that: In step (4), the hot pressing temperature is 50-100° C., the hot pressing time is 2-5 hours, and the pressure is 5-15 MPa.

8. The preparation method according to claim 1, characterized in that: In step (6), the diluted epoxy resin glue comprises epoxy resin, curing agent and diluent, the sum of the mass fractions of the epoxy resin and the curing agent is 5% to 50%, and the diluent is ethanol or ethyl acetate.

9. The preparation method according to claim 1, characterized in that: During the soaking process, ensure that the honeycomb is completely immersed in the diluted epoxy resin glue solution, the soaking time is 1 min to 5 min, the drying temperature is 40° C. to 70° C., and the drying time is 10 to 60 min. 10 . The chopped carbon fiber honeycomb prepared by the preparation method according to claim 1 .

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