Carbon fiber plate and compression molding method thereof

Abstract

The invention relates to a carbon fiber plate and a compression molding method thereof, and the compression molding method comprises the following steps: firstly, laying two carbon fiber blank plates in a compression mold in a laminating manner to obtain a carbon fiber compression molding assembly; the carbon fiber mold pressing assembly is sequentially subjected to first pressurization heating, second pressurization heating, pressure maintaining cooling and cooling demolding, and a formed carbon fiber plate is obtained; the problem of warping of the ultrathin carbon fiber plate in the compression molding process is solved, the flatness is preferably as low as 0.4 mm or below, meanwhile, the high strength performance of the ultrathin carbon fiber plate is ensured, and the tensile strength is preferably as high as 3800 MPa; and the forming period is shortened, the production efficiency is improved, and large-scale mass production is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material forming, in particular to a carbon fiber plate and a compression molding method thereof, in particular to an ultra-thin carbon fiber plate and a compression molding method thereof. Background Art

[0002] Carbon fiber reinforced polymers (CFRP) is a high-performance composite material composed of carbon fiber and matrix materials such as resin, metal or ceramic. It has excellent properties such as high strength, light weight, high modulus, low density, high temperature resistance and fatigue resistance. Carbon fiber sheets are rapidly developing in many fields such as aerospace, automobiles, wind turbine blades, sports and leisure products, building decoration and pressure vessels.

[0003] At present, the mainstream process for preparing carbon fiber sheets is compression molding. However, during the heating and cooling process, due to the large difference in thermal expansion coefficients between carbon fiber and matrix material, the shrinkage rates of the two are different, which causes internal stress to cause warping; in addition, the content and distribution of carbon fiber and the compression molding process parameters also have a significant impact on warping deformation and product quality. That is, the carbon fiber sheets produced by the existing compression molding method, especially ultra-thin carbon fiber sheets (≤0.5mm), have low flatness (warping greater than 2cm) pass rate, high production energy consumption and low efficiency, and are not suitable for large-scale mass production under the same conditions.

[0004] For example, CN111469454A discloses a method for preparing a green recycled carbon fiber thermoplastic material sheet and a building formwork, which places recycled carbon fiber and thermoplastic fiber non-woven felt in a hot pressing roller, and hot presses them at 100-300°C and 15-45MPa to prepare a recycled carbon fiber thermoplastic material sheet. It only considers the tensile strength and modulus properties, does not involve research on flatness, and does not solve the warping problem of ultra-thin carbon fiber sheets.

[0005] For example, CN105690907A discloses a carbon fiber sheet and a product molded using the carbon fiber sheet. The carbon fiber cloth layer and the plastic layer are first compounded by hot pressing to obtain a carbon fiber sheet, and then the carbon fiber sheet is molded to obtain a carbon fiber product, and then the surface of the carbon fiber cloth is impregnated with resin. This method only considers the simplification of the process, and still does not consider the warping problem, and the product qualification rate is low.

[0006] Therefore, how to solve the warping problem of carbon fiber sheets, especially ultra-thin carbon fiber sheets after compression molding is a technical problem that urgently needs to be solved in the current field. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a carbon fiber sheet and a molding method thereof, and in particular provides an ultra-thin carbon fiber sheet and a molding method thereof, which solves the warping problem of the carbon fiber sheet after molding in the prior art, improves the molding efficiency, reduces the production cost, and is suitable for large-scale mass production.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a compression molding method for a carbon fiber plate, the compression molding method comprising the following steps:

[0010] (1) stacking two carbon fiber blank sheets in a molding die to obtain a carbon fiber molded component;

[0011] (2) The carbon fiber molded component of step (1) is subjected to a first pressurization and heating, a second pressurization and heating, a pressure-maintaining and temperature-lowering, and a cooling and demolding step in sequence to obtain a molded carbon fiber sheet.

[0012] The compression molding method of the present invention optimizes the molding method and molding process parameters of the carbon fiber blank plate, adopts a double-layer stacking method combined with segmented pressurization and heating curing, reduces the warping stress generated in the molding process, improves the dimensional accuracy and surface quality of the product, and solves the technical problem of low pass rate of carbon fiber plate products, especially ultra-thin carbon fiber plates, in the compression molding process. At the same time, it reduces production energy consumption and shortens the molding cycle, thereby improving production efficiency and realizing large-scale mass production.

[0013] Compared with the traditional single-layer laying and one-time pressurized heating molding method, the molding time per furnace is shortened from about 200 minutes to about 140 minutes, the number of moldings per furnace is increased from about 6 to about 16, the energy consumption is also greatly reduced, and the time required for steam heating is short.

[0014] Preferably, the carbon fiber blank sheet material in step (1) comprises carbon fiber and a matrix material.

[0015] Preferably, the carbon fiber blank sheet has a thickness of 0.2-0.4 mm, for example, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm or 0.4 mm.

[0016] It is worth noting that the present invention is mainly aimed at the warping problem of ultra-thin carbon fiber sheets during the compression molding process.

[0017] Preferably, based on the mass of the carbon fiber blank plate being 100%, the content of carbon fiber in the carbon fiber blank plate is 60-70wt%, for example, it may be 60wt%, 62wt%, 64wt%, 66wt%, 68wt% or 70wt%.

[0018] The present invention further preferably has a carbon fiber content of 60 to 70 wt % in the carbon fiber blank sheet, which ensures high strength of the formed carbon fiber sheet while reducing the difficulty of forming, reducing flatness, and improving the qualified rate of the product; if the carbon fiber content in the carbon fiber blank sheet is low, it may be difficult to maintain a consistent orientation during the forming process, resulting in a large product flatness, a reduced qualified rate, and inability to mass produce; if the carbon fiber content in the carbon fiber blank sheet is high, it will be difficult to evenly distribute the fibers during the forming process, and fiber accumulation or wrinkles are likely to occur, resulting in defects such as uneven local thickness, bubbles or voids.

[0019] Preferably, step (1) further comprises laying a release film on the surface of the carbon fiber blank sheet material close to the molding die.

[0020] Preferably, in step (1), a release film is laid between the two carbon fiber blank sheets.

[0021] The present invention further preferably comprises step (1) of laying a release film on the surface of the carbon fiber blank sheet close to the molding die, wherein the release film forms an isolation layer between the carbon fiber blank sheet and the mold to prevent the matrix material (such as resin) from adhering to the mold surface during the curing process, thereby helping to reduce damage to the product during demolding and ensuring the integrity and surface quality of the product.

[0022] Preferably, the pressurizing pressure of the first pressurizing and heating in step (2) is 110-130t, for example, it can be 110t, 112t, 115t, 118t, 120t, 123t, 125t, 128t or 130t, etc.

[0023] Preferably, the temperature of the carbon fiber molded component after the first pressurizing and heating is 60-70°C, for example, it can be 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C or 70°C, etc.

[0024] The present invention further preferably has a temperature of the carbon fiber molded component of 60-70°C after the first pressurizing and heating, which is conducive to the full melting and flow of the matrix material (such as resin), thereby filling the mold cavity and preventing defects in the product due to insufficient fluidity, large internal stress, and warping. If the temperature of the carbon fiber molded component after the first pressurizing and heating is too low, the fluidity of the matrix material will be poor, resulting in voids and cracks in the product. If the temperature of the carbon fiber molded component after the first pressurizing and heating is too high, the curing reaction will start prematurely, resulting in inconsistent curing degrees of the inner and outer layers of the carbon fiber blank sheet, thereby causing the product to crack or warp.

[0025] Preferably, the heating rate of the first pressurized heating is 3-4°C / min, for example, 3°C / min, 3.2°C / min, 3.4°C / min, 3.6°C / min, 3.8°C / min or 4°C / min.

[0026] It is worth noting that the present invention adjusts the rate of heating or cooling by controlling the opening of the drain valve of the hot press, wherein the opening of the drain valve during the first pressurization and heating is 1 / 4 to 2 / 5 of the full opening, for example, it can be 1 / 4, 1 / 3 or 2 / 5.

[0027] Preferably, the first pressurized heating time is 6 to 12 minutes, for example, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, 11 minutes or 12 minutes.

[0028] Preferably, the pressurizing pressure of the second pressurizing and heating in step (2) is 200-220t, for example, it can be 200t, 205t, 210t, 215t or 220t.

[0029] Preferably, the temperature of the carbon fiber molded component after the second pressurizing and heating is 130-135°C, for example, 130°C, 131°C, 132°C, 133°C, 134°C or 135°C.

[0030] The present invention further preferably has a temperature of the carbon fiber molded component after the second pressurizing and heating of 130 to 135°C, which is conducive to the smooth molding of the carbon fiber sheet. If the temperature of the carbon fiber molded component after the second pressurizing and heating is too low, it will lead to insufficient curing reaction, prolonged molding time, reduced production efficiency, and reduced product quality. If the temperature of the carbon fiber molded component after the second pressurizing and heating is too high, it will lead to a too fast curing reaction, resulting in internal stress in the carbon fiber blank sheet, which is prone to warping or cracking.

[0031] Preferably, the heating rate of the second pressurized heating is 4-6°C / min, for example, 4°C / min, 4.5°C / min, 5°C / min, 5.5°C / min or 6°C / min.

[0032] Preferably, during the second pressurizing and heating, the opening degree of the drain valve of the hot press is 1 / 4 to 2 / 5 of the full opening, for example, it can be 1 / 4, 1 / 3 or 2 / 5.

[0033] Preferably, the second pressurized heating time is 24 to 28 minutes, for example, 24 minutes, 25 minutes, 26 minutes, 27 minutes or 28 minutes.

[0034] Preferably, the pressure-maintaining and cooling in step (2) includes maintaining the pressurization pressure of the second pressurization and heating to cool the carbon fiber molded component.

[0035] Preferably, the temperature of the carbon fiber molded component after the pressure-maintaining and temperature-lowering is 100-105° C., for example, it may be 100° C., 101° C., 102° C., 103° C., 104° C. or 105° C.

[0036] The present invention further preferably sets the temperature of the carbon fiber molded component after the pressure-maintaining and cooling to 100-105°C, which is beneficial to improving the toughness of the product; if the temperature of the carbon fiber molded component after the pressure-maintaining and cooling is too low, the flatness of the product will increase; if the temperature of the carbon fiber molded component after the pressure-maintaining and cooling is too high, the toughness of the product will decrease.

[0037] Preferably, the cooling rate of the pressure-maintaining cooling is 0.5-0.8°C / min, for example, 0.5°C / min, 0.6°C / min, 0.7°C / min or 0.8°C / min.

[0038] It is worth noting that the present invention adjusts the cooling rate by controlling the opening of the hot press drain valve, and the drain valve is fully open during the pressure-maintaining and temperature-reducing process.

[0039] Preferably, the pressure-maintaining and temperature-lowering time is 40 to 50 minutes, for example, 40 minutes, 42 minutes, 45 minutes, 48 ​​minutes or 50 minutes.

[0040] Preferably, the carbon fiber molded component is first depressurized before the cooling and demoulding in step (2).

[0041] Preferably, the cooling and demolding in step (2) includes cooling the carbon fiber molded component to ≤35°C and then demolding, for example, it can be 35°C, 33°C, 30°C, 28°C, 25°C, 22°C or 20°C.

[0042] As a further preferred technical solution of the present invention, the compression molding method comprises the following steps:

[0043] (1) stacking two carbon fiber blank sheets and laying them in a molding die, and laying a release film on the surface of the carbon fiber blank sheets close to the molding die to obtain a carbon fiber molding assembly;

[0044] The thickness of the carbon fiber blank plate is 0.2-0.4 mm; the content of carbon fiber in the carbon fiber blank plate is 60-70 wt %;

[0045] (2) The carbon fiber molded component of step (1) is sequentially treated as follows: first, under a pressurizing pressure of 110 to 130 tons, the carbon fiber molded component is first pressurized and heated at a heating rate of 3 to 4 ° C / min for 6 to 12 minutes until the temperature of the carbon fiber molded component is 60 to 70 ° C; then, under a pressurizing pressure of 200 to 220 tons, the carbon fiber molded component is secondly pressurized and heated at a heating rate of 4 to 6 ° C / min for 24 to 28 minutes until the temperature of the carbon fiber molded component is 130 to 135 ° C; then, the pressurizing pressure of 200 to 220 tons is maintained, and the temperature is reduced at a cooling rate of 0.5 to 0.8 ° C / min for 40 to 50 minutes until the temperature of the carbon fiber molded component is 100 to 105 ° C; finally, the pressure is released and the carbon fiber molded component is cooled to ≤35 ° C and then demolded to obtain a molded carbon fiber sheet.

[0046] In a second aspect, the present invention provides a carbon fiber plate, which is made by the compression molding method as described in the first aspect.

[0047] The carbon fiber sheet of the present invention has an ultra-thin thickness of 0.2 to 0.4 mm, but its flatness is still less than 1 mm, and can even be less than 0.4 mm, meeting the production qualification standards, and has excellent properties such as light weight, high strength, high stiffness and corrosion resistance. It is widely used in aerospace, medical equipment, electronic information and industrial equipment and other fields.

[0048] Preferably, the thickness of the carbon fiber sheet is 0.2-0.4 mm, for example, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm or 0.4 mm.

[0049] Preferably, the flatness of the carbon fiber sheet is less than 1 mm, for example, it may be 0 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm or 0.9 mm, etc., preferably ≤0.4 mm.

[0050] Compared with the prior art, the present invention has at least the following beneficial effects:

[0051] (1) The compression molding method of the carbon fiber sheet provided by the present invention regulates and controls the process parameters such as the pressurization pressure, mold temperature, heating rate and cooling rate in the mold installation method and the compression molding process. The double-layer stacking of the carbon fiber blank sheet offsets each other in the molding process, thereby solving the problem of basic warping and increasing the product qualification rate. At the same time, the control of the pressurization and heating process of the compression molding process also improves the quality and performance of the product, shortens the molding cycle, improves the production efficiency, and realizes large-scale mass production.

[0052] (2) The carbon fiber sheet provided by the present invention has an ultra-thin thickness of 0.2 to 0.4 mm, a flatness preferably as low as 0.4 mm or less, and a tensile strength preferably as high as 3800 MPa; it has excellent properties such as light weight, high strength, high stiffness and corrosion resistance, and is widely used in aerospace, medical equipment, electronic information and industrial equipment and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 is a schematic cross-sectional structure diagram of the carbon fiber molded component in the mold forming method provided in Example 1 of the present invention;

[0054] In the figure: 1. upper mold of the molding die; 2. first release film; 3. first carbon fiber blank sheet; 4. second carbon fiber blank sheet; 5. second release film; 6. lower mold of the molding die. DETAILED DESCRIPTION

[0055] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0056] The compression molding described in the following embodiments and comparative examples is carried out in a hot press having a maximum working pressure of 500t; the hot press is heated by a steam generator, wherein the low steam pressure is set to 0.5MPa, the high steam pressure is set to 0.7MPa, and the power is 144kw.

[0057] The release paper used in the following examples and comparative examples is double-sided CCK release paper (Anhui Xinyu New Material Technology Co., Ltd.).

[0058] 1. Implementation

[0059] Example 1

[0060] This embodiment provides a compression molding method for a carbon fiber plate, the compression molding method comprising the following steps:

[0061] (1) stacking two carbon fiber blank sheets and laying them in a molding die, and laying release paper on the surface of the carbon fiber blank sheets close to the molding die to obtain a carbon fiber molding assembly;

[0062] The carbon fiber blank plate is a carbon fiber prepreg cloth; the thickness of the carbon fiber blank plate is 0.4 mm; the content of carbon fiber in the carbon fiber blank plate is 70wt%;

[0063] (2) The carbon fiber molded component of step (1) is sequentially treated as follows: first, under a pressurizing pressure of 120 t, pressurized and heated at a heating rate of 3.5°C / min for 8 min until the temperature of the carbon fiber molded component is 65°C; then, under a pressurizing pressure of 200 t, pressurized and heated at a heating rate of 6°C / min for 24 min until the temperature of the carbon fiber molded component is 132°C; then, the pressurizing pressure of 200 t is maintained, and the temperature is cooled at a cooling rate of 0.8°C / min for 40 min until the temperature of the carbon fiber molded component is 102°C; finally, the pressure is released, and the carbon fiber molded component is cooled to 25°C and then demolded to obtain a molded carbon fiber sheet.

[0064] like Figure 1 As shown, the cross-sectional structure diagram of the carbon fiber molded assembly in this embodiment shows that from top to bottom, there are the upper mold 1 of the mold, the first release film 2, the first carbon fiber blank sheet 3, the second carbon fiber blank sheet 4, the second release film 5, and the lower mold 6 of the mold. Compared with the traditional mold installation method, in this embodiment, two carbon fiber blank sheets are stacked and laid in the mold, and a release film is laid on the surface of the carbon fiber blank sheet close to the mold; this laying method makes the internal stresses generated by the carbon fiber blank sheet in the subsequent molding process offset each other, thereby reducing the flatness and avoiding warping.

[0065] This embodiment also provides a carbon fiber plate, which is made by the compression molding method provided by this embodiment, and has a thickness of 0.4 mm and a flatness of 0.2 to 0.4 mm.

[0066] Example 2

[0067] This embodiment provides a compression molding method for a carbon fiber plate, the compression molding method comprising the following steps:

[0068] (1) stacking two carbon fiber blank sheets and laying them in a molding die, and laying release paper on the surface of the carbon fiber blank sheets close to the molding die to obtain a carbon fiber molding assembly;

[0069] The carbon fiber blank sheet is a carbon fiber prepreg cloth; the thickness of the carbon fiber blank sheet is 0.3 mm; the content of carbon fiber in the carbon fiber blank sheet is 65 wt%; (2) the carbon fiber molded component of step (1) is subjected to the following treatments in sequence: first, under a pressurizing pressure of 110 t, the carbon fiber molded component is first pressurized and heated at a heating rate of 4°C / min for 6 min until the temperature of the carbon fiber molded component is 60°C; then, under a pressurizing pressure of 200 t, the carbon fiber molded component is second pressurized and heated at a heating rate of 4°C / min for 26 min until the temperature of the carbon fiber molded component is 130°C; then, the pressurizing pressure is maintained at 180 t, and the temperature is maintained and cooled at a cooling rate of 0.6°C / min for 45 min until the temperature of the carbon fiber molded component is 105°C; finally, the pressure is released and the carbon fiber molded component is cooled to 35°C and then demolded to obtain a molded carbon fiber sheet.

[0070] This embodiment also provides a carbon fiber plate, which is made by the compression molding method provided by this embodiment, and has a thickness of 0.3 mm and a flatness of 0.2 to 0.4 mm.

[0071] Example 3

[0072] This embodiment provides a compression molding method for a carbon fiber plate, the compression molding method comprising the following steps:

[0073] (1) stacking two carbon fiber blank sheets and laying them in a molding die, and laying release paper on the surface of the carbon fiber blank sheets close to the molding die to obtain a carbon fiber molding assembly;

[0074] The carbon fiber blank plate is a carbon fiber prepreg cloth; the thickness of the carbon fiber blank plate is 0.2 mm; the content of carbon fiber in the carbon fiber blank plate is 60wt%;

[0075] (2) The carbon fiber molded component of step (1) is sequentially treated as follows: first, under a pressurizing pressure of 130t, pressurize and heat for 12min at a heating rate of 3°C / min until the temperature of the carbon fiber molded component is 70°C; then, under a pressurizing pressure of 220t, pressurize and heat for 28min at a heating rate of 5°C / min until the temperature of the carbon fiber molded component is 135°C; then, the pressurizing pressure of 220t is maintained, and the temperature is cooled at a cooling rate of 0.5°C / min for 50min until the temperature of the carbon fiber molded component is 100°C; finally, the pressure is released, and the carbon fiber molded component is cooled to 30°C and then demolded to obtain a molded carbon fiber sheet.

[0076] This embodiment also provides a carbon fiber plate, which is made by the compression molding method provided by this embodiment, and has a thickness of 0.2 mm and a flatness of 0.2 to 0.4 mm.

[0077] Example 4

[0078] This embodiment provides a compression molding method for a carbon fiber plate, and the compression molding method is the same as that of Embodiment 1 except that the temperature of the carbon fiber molded component after the first pressurizing and heating is 55° C.

[0079] This embodiment also provides a carbon fiber plate, which is made by the compression molding method provided by this embodiment.

[0080] Example 5

[0081] This embodiment provides a compression molding method for a carbon fiber plate, and the compression molding method is the same as that of Embodiment 1 except that the temperature of the carbon fiber molded component after the first pressurizing and heating is 75°C.

[0082] This embodiment also provides a carbon fiber plate, which is made by the compression molding method provided by this embodiment.

[0083] Example 6

[0084] This embodiment provides a compression molding method for a carbon fiber plate material. The compression molding method is the same as that of Embodiment 1 except that the heating rate of the second pressurizing and heating is 3° C. / min.

[0085] This embodiment also provides a carbon fiber plate, which is made by the compression molding method provided by this embodiment.

[0086] Example 7

[0087] This embodiment provides a compression molding method for a carbon fiber plate material. The compression molding method is the same as that of Embodiment 1 except that the heating rate of the second pressurizing and heating is 7° C. / min.

[0088] This embodiment also provides a carbon fiber plate, which is made by the compression molding method provided by this embodiment.

[0089] Example 8

[0090] The present embodiment provides a compression molding method for a carbon fiber sheet material, and the compression molding method is the same as that of Embodiment 1 except that in step (2), the temperature of the carbon fiber molded component is reduced to 90° C. after the pressure is maintained and cooled, and then the pressure is released.

[0091] This embodiment also provides a carbon fiber plate, which is made by the compression molding method provided by this embodiment.

[0092] Example 9

[0093] The present embodiment provides a compression molding method for a carbon fiber sheet material, and the compression molding method is the same as that of Embodiment 1 except that the temperature of the carbon fiber molded component is 110° C. for pressure release treatment after the pressure maintenance and cooling in step (2).

[0094] This embodiment also provides a carbon fiber plate, which is made by the compression molding method provided by this embodiment.

[0095] 2. Comparison

[0096] Comparative Example 1

[0097] This comparative example provides a compression molding method for a carbon fiber sheet material. The compression molding method is the same as that of Example 1 except that step (1) is to lay a carbon fiber blank sheet material into a compression mold.

[0098] This comparative example also provides a carbon fiber plate, which is made by the compression molding method provided in this comparative example.

[0099] Comparative Example 2

[0100] This comparative example provides a compression molding method for a carbon fiber plate material, which is the same as Example 1 except that the first pressurization and heating is not performed but the second pressurization and heating is performed directly.

[0101] This comparative example also provides a carbon fiber plate, which is made by the compression molding method provided in this comparative example.

[0102] 3. Test and its results

[0103] The flatness and tensile strength of the carbon fiber sheet obtained by the compression molding method of the carbon fiber sheet provided in the above embodiments and comparative examples were tested, and the results are shown in Table 1;

[0104] Table 1

[0105]

[0106]

[0107] From the test results in Table 1, we can see that:

[0108] (1) It can be seen from Examples 1 to 3 that the present invention, by regulating the molding method and the process parameters of each curing stage in the compression molding process, can obtain a carbon fiber sheet with a flatness as low as less than 0.4 mm and a tensile strength as high as more than 3800 MPa, thereby solving the problem of warping of ultra-thin carbon fiber sheets during the compression molding process and ensuring high strength performance.

[0109] (2) Combining Example 1 with Example 4 and Example 5, it can be seen that: in Example 4, the temperature of the carbon fiber molded component after the first pressurizing and heating is relatively low, resulting in the flatness of the product increasing to 0.4-0.6 mm and the tensile strength decreasing to 3600 MPa; in Example 5, the temperature of the carbon fiber molded component after the first pressurizing and heating is relatively high, resulting in the flatness of the product increasing to 0.5-0.7 mm and the tensile strength decreasing by 3500 MPa; this shows that the present invention further preferably sets the temperature of the carbon fiber molded component after the first pressurizing and heating to 60-70°C, which further reduces the flatness of the obtained product, reduces warping, and improves the strength performance.

[0110] (3) Combining Example 1 with Example 6 and Example 7, it can be seen that: in Example 6, the heating rate of the second pressurized heating is relatively low, resulting in the flatness of the product increasing to 0.5-0.7 mm and the tensile strength decreasing to 3500 MPa; the heating rate of the second pressurized heating in Example 7 is relatively high, resulting in the flatness of the product increasing to 0.7-0.9 mm and the tensile strength decreasing to 3300 MPa; this shows that the present invention further prefers that the heating rate of the second pressurized heating is 4-6°C / min, which further reduces the product warping phenomenon and improves the product quality.

[0111] (4) Combining Example 1 with Example 8 and Example 9, it can be seen that: the temperature of the carbon fiber molded component during the pressure release treatment in Example 8 is too low, that is, the pressure release treatment is too late, resulting in the flatness of the product increasing to 0.7-0.9 mm and the tensile strength decreasing to 3300 MPa; the temperature of the carbon fiber molded component during the pressure release treatment in Example 9 is too high, that is, the pressure release treatment is too early, resulting in the flatness of the product increasing to 0.6-0.9 mm and the tensile strength decreasing to 3300 MPa; this shows that the present invention further preferably performs the pressure release treatment after the pressure maintenance and cooling, wherein the temperature of the carbon fiber molded component is 100-105°C, that is, the timing of the pressure release treatment is further selected, thereby further improving the quality and performance of the product and reducing the warping phenomenon.

[0112] (5) Combining Example 1 with Comparative Examples 1 and 2, in Comparative Example 2, since the traditional mold loading method is still adopted in step (1), that is, only one carbon fiber blank sheet is laid into the molding die, the internal stress generated in the molding process cannot be offset, thereby affecting the flatness and strength performance of the product; in Comparative Example 2, since the second pressurization and heating is directly performed in step (2), the inner and outer layers of the carbon fiber blank sheet are unevenly cured, thereby affecting the flatness and strength performance of the product; this shows that the present invention solves the warping problem existing in the molding process of ultra-thin carbon fiber sheets by adopting a stacked laying mold loading method and a segmented curing molding method, while ensuring the high strength performance of the product.

[0113] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A compression molding method for a carbon fiber sheet, characterized in that: The compression molding method comprises the following steps: (1) stacking two carbon fiber blank sheets in a molding die to obtain a carbon fiber molded component; (2) The carbon fiber molded component of step (1) is subjected to a first pressurization and heating, a second pressurization and heating, a pressure-maintaining and temperature-lowering, and a cooling and demolding step in sequence to obtain a molded carbon fiber sheet.

2. The compression molding method according to claim 1, characterized in that: The thickness of the carbon fiber blank sheet in step (1) is 0.2 to 0.4 mm; Preferably, based on the mass of the carbon fiber blank plate being 100%, the content of carbon fiber in the carbon fiber blank plate is 60-70wt%.

3. The compression molding method according to claim 1 or 2, characterized in that: Step (1) also includes laying a release film on the surface of the carbon fiber blank sheet material close to the molding die; Preferably, in step (1), a release film is laid between the two carbon fiber blank sheets.

4. The compression molding method according to any one of claims 1 to 3, characterized in that: Step (2) The first pressurized heating pressure is 110-130t; Preferably, the temperature of the carbon fiber molded component after the first pressurization and heating is 60-70° C.; Preferably, the heating rate of the first pressurized heating is 3-4°C / min; Preferably, the first pressurizing and heating time is 6 to 12 minutes.

5. The compression molding method according to any one of claims 1 to 4, characterized in that: Step (2) The second pressurized heating pressure is 200-220t; Preferably, the temperature of the carbon fiber molded component after the second pressurization and heating is 130-135° C.; Preferably, the heating rate of the second pressurized heating is 4-6°C / min; Preferably, the second pressurized heating time is 24 to 28 minutes.

6. The compression molding method according to any one of claims 1 to 5, characterized in that: The pressure-maintaining and cooling step (2) includes maintaining the pressure of the second pressurized and heated process to cool the carbon fiber molded component; Preferably, the temperature of the carbon fiber molded component after the pressure-maintaining and temperature-lowering is 100-105° C.; Preferably, the cooling rate of the pressure-maintaining and cooling process is 0.5-0.8°C / min; Preferably, the pressure-maintaining and temperature-lowering time is 40 to 50 minutes.

7. The compression molding method according to any one of claims 1 to 6, characterized in that: Before the cooling and demoulding in step (2), the carbon fiber molded component is first subjected to a decompression treatment; Preferably, the cooling and demoulding in step (2) includes cooling the carbon fiber molded component to ≤35°C before demoulding.

8. The compression molding method according to any one of claims 1 to 7, characterized in that: The compression molding method comprises the following steps: (1) stacking two carbon fiber blank sheets and laying them in a molding die, and laying a release film on the surface of the carbon fiber blank sheets close to the molding die to obtain a carbon fiber molding assembly; The thickness of the carbon fiber blank plate is 0.2-0.4 mm; the content of carbon fiber in the carbon fiber blank plate is 60-70 wt %; (2) The carbon fiber molded component of step (1) is sequentially treated as follows: first, under a pressurizing pressure of 110 to 130 tons, the carbon fiber molded component is first pressurized and heated at a heating rate of 3 to 4 ° C / min for 6 to 12 minutes until the temperature of the carbon fiber molded component is 60 to 70 ° C; then, under a pressurizing pressure of 200 to 220 tons, the carbon fiber molded component is secondly pressurized and heated at a heating rate of 4 to 6 ° C / min for 24 to 28 minutes until the temperature of the carbon fiber molded component is 130 to 135 ° C; then, the pressurizing pressure of 200 to 220 tons is maintained, and the temperature is reduced at a cooling rate of 0.5 to 0.8 ° C / min for 40 to 50 minutes until the temperature of the carbon fiber molded component is 100 to 105 ° C; finally, the pressure is released and the carbon fiber molded component is cooled to ≤35 ° C and then demolded to obtain a molded carbon fiber sheet.

9. A carbon fiber sheet, characterized in that: The carbon fiber sheet is made by the compression molding method as described in any one of claims 1 to 8.

10. The carbon fiber sheet according to claim 9, characterized in that: The thickness of the carbon fiber sheet is 0.2-0.4 mm; Preferably, the flatness of the carbon fiber sheet is less than 1 mm, preferably ≤ 0.4 mm.

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