Sheet molding compound and preparation method thereof, vehicle ornament and vehicle

Abstract

In order to reduce the material cost and improve the strength of the sheet molding compound, the invention provides the sheet molding compound and the preparation method thereof, the vehicle ornament and the vehicle, the sheet molding compound comprises large-tow carbon fibers, glass fibers and thermosetting resin, and the large-tow carbon fibers are carbon fibers with the tow specification not less than 48K; the mass ratio of the large-tow carbon fibers to the glass fibers is (75-25): (25-75), and the mass content of the thermosetting resin in the sheet molding compound is 45%-65%.

Description

Technical Field

[0001] The present invention belongs to the technical field of sheet molding compounds, and in particular relates to a sheet molding compound and a preparation method thereof, a vehicle trim, and a vehicle. Background Art

[0002] Carbon fiber reinforced plastics (CFRP) have been widely used in aerospace, bridge construction, and flying cars due to their numerous advantages, including light weight, high strength, corrosion resistance, and design flexibility. As a key material for lightweighting vehicles, CFRP's high performance comes at a high cost, and large-scale application places higher demands on controlling material costs. Furthermore, compared to continuous fiber fabric prepreg solutions, discontinuous fiber-reinforced composites, such as sheet molding compounds (SMCs), are more suitable for automotive parts with complex structural features. Furthermore, SMC compression molding eliminates the need for precise layer layup, which helps reduce labor costs in actual production.

[0003] However, existing technologies for carbon fiber reinforced sheet molding compounds primarily use small-tow carbon fibers such as 3K, 6K, and 12K. The raw material cost of small-tow carbon fibers is relatively high, limiting their large-scale application in the automotive sector.

[0004] Therefore, in order to balance performance and cost, it is necessary to develop a sheet molding compound solution with low material cost and high molding efficiency. Summary of the Invention

[0005] The present invention provides a sheet molding compound and a preparation method thereof, a vehicle trim, and a vehicle. The sheet molding compound has the characteristics of high strength, light weight, and low cost.

[0006] The technical solutions adopted by the present invention to solve the above technical problems are as follows: In a first aspect, the present invention provides a sheet molding compound comprising large-tow carbon fiber, glass fiber, and a thermosetting resin, wherein the large-tow carbon fiber is a carbon fiber having a tow specification of not less than 48K; the mass ratio of the large-tow carbon fiber to the glass fiber is (75-25): (25-75), and the mass content of the thermosetting resin in the sheet molding compound is 45%-65%.

[0007] Optionally, the mass ratio of the large-tow carbon fiber to the glass fiber is 3:1, 1:1 or 1:3.

[0008] Optionally, the tow specification of the large tow carbon fiber is 50K; And / or, the mass content of the thermosetting resin in the sheet molding compound is 50%, 55% or 60%.

[0009] Optionally, the length of the large-tow carbon fiber is 6 to 30 mm, and the length of the glass fiber is 6 to 30 mm.

[0010] Optionally, the large-tow carbon fiber has a tensile strength of ≥4390 MPa and a tensile modulus of ≥252 GPa.

[0011] Optionally, the glass fiber includes one or more of E-type untwisted yarn, C glass fiber, and S glass fiber.

[0012] Optionally, the thermosetting resin includes one or more of epoxy resin, vinyl ester resin, polyester resin, polyurethane resin, phenolic resin, alkyd resin, amino resin, and silicone resin; And / or, the viscosity of the thermosetting resin is 8500-10500 mPa·s.

[0013] In a second aspect, the present invention further provides a method for preparing the sheet molding compound as described in any one of the above, comprising the following steps: Obtaining a thermosetting resin film, and uniformly dispersing large-tow carbon fibers and glass fibers on the surface of the thermosetting resin film; Covering the large-tow carbon fiber and glass fiber with the thermosetting resin film to obtain a resin film sandwiching the carbon fiber and glass fiber; The resin film is rolled and degased to obtain a sheet molding compound preform.

[0014] Optionally, in the step of dispersing the large-tow carbon fibers and the glass fibers on the surface of the thermosetting resin film, the total weight of the large-tow carbon fibers and the glass fibers on each square meter of the thermosetting resin film is 900-1100 g.

[0015] In a third aspect, the present invention provides a vehicle trim part, which is molded from any one of the sheet molding compounds described above, or molded from a sheet molding compound prepared by any one of the preparation methods described above.

[0016] Optionally, the compression molding conditions are: the mold is preheated at 130-140° C. for 30-45 seconds, the molding pressure is 10-12 MPa, and the holding time is 15-20 minutes.

[0017] In a fourth aspect, the present invention provides a vehicle comprising the vehicle trim as described in any one of the above.

[0018] In the present invention, the sheet molding compound obtained by physically combining large-tow carbon fibers, glass fibers, and thermosetting resin has excellent mechanical properties. Compared with using small-tow carbon fibers, the sheet molding compound prepared using large-tow carbon fibers in this application is more cost-effective. Doping the large-tow carbon fibers with glass fibers further reduces the material cost of the sheet molding compound.

[0019] In particular, compared to the prior art of manufacturing automotive parts using continuous fiber fabric prepregs, the preparation of sheet molding compounds does not require precise layup, which helps reduce labor costs. Furthermore, compared to the woven texture of vehicle trim surfaces produced using continuous carbon fiber fabric prepregs, the sheet molding compounds produced through compression molding in this application exhibit a unique forged texture on the surface, meeting user demands for personalized styling of interior and exterior vehicle trims. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a surface texture diagram of a sheet molding compound provided in Example 3 of the present invention. DETAILED DESCRIPTION

[0021] In order to make the technical solutions and beneficial effects of the present invention more clear, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0022] One embodiment of the present invention provides a sheet molding compound, comprising large-tow carbon fiber, glass fiber, and a thermosetting resin, wherein the large-tow carbon fiber is a carbon fiber with a tow specification of not less than 48K; the mass ratio of the large-tow carbon fiber to the glass fiber is (75~25):(25~75), and the mass content of the thermosetting resin in the sheet molding compound is 45%~65%.

[0023] In this embodiment, the sheet molding compound obtained by physically combining large-tow carbon fibers, glass fibers, and a thermosetting resin has good strength. Compared to using small-tow carbon fibers, the use of large-tow carbon fibers in preparing the sheet molding compound in this application reduces material costs. Doping the large-tow carbon fibers with glass fibers further reduces the material cost of the sheet molding compound.

[0024] Specifically, the mass ratio of large-tow carbon fiber to glass fiber includes, but is not limited to, 3:1, 3:2, 1:1, 2:3, or 1:3. The mass content of thermosetting resin in the sheet molding compound includes, but is not limited to, 45%, 48%, 50%, 53%, 56%, 59%, 62%, or 65%.

[0025] In some embodiments, the large-tow carbon fiber has a tow specification of 50K. By selecting carbon fiber of this tow specification and compounding it with glass fiber and thermosetting resin, a sheet molding compound with good mechanical properties and low cost is obtained.

[0026] In some embodiments, the mass content of the thermosetting resin in the sheet molding compound is 50%, 55%, or 60%. By selecting the above mass content of the thermosetting resin, it is easy to support and fix the carbon fiber and glass fiber.

[0027] In some embodiments, the length of the large-tow carbon fiber is 6-30 mm, and the length of the glass fiber is 6-30 mm.

[0028] Specifically, the lengths of the large-tow carbon fibers and glass fibers include, but are not limited to, 6 mm, 10 mm, 14 mm, 18 mm, 22 mm, 25 mm, or 30 mm. By limiting the lengths of the large-tow carbon fibers and glass fibers, their uniform distribution on the thermosetting resin film is facilitated, ensuring good load transfer between the carbon fibers, glass fibers, and the thermosetting resin. Furthermore, limiting the lengths of the large-tow carbon fibers and glass fibers helps improve the sheet molding compound's resistance to fatigue failure. When subjected to cyclic loads, stress concentration is reduced, delaying the initiation and propagation of fatigue cracks and thereby extending the service life of the sheet molding compound.

[0029] In a preferred embodiment, the length of the large-tow carbon fiber is 25 mm, and the length of the glass fiber is 25 mm.

[0030] In some embodiments, the large-tow carbon fiber has a tensile strength of ≥4390 MPa and a tensile modulus of ≥252 GPa.

[0031] Specifically, the large-tow carbon fiber has a tow specification of 50K, a bulk density of 1.78 g / cm3, a tensile strength of 4390 MPa, and a tensile modulus of 252 GPa, so as to improve the strength of the sheet molding compound and its ability to bear external loads.

[0032] In some embodiments, the glass fiber includes one or more of E-type untwisted yarn, C-glass fiber, and S-glass fiber.

[0033] Specifically, the glass fiber is an E-type untwisted yarn with a linear density of 2400 tex, a tensile strength of 2741 MPa, and a tensile modulus of 81.2 GPa, so as to cooperate with the carbon fiber to improve the strength of the sheet molding compound and its ability to bear external loads.

[0034] In some embodiments, the thermosetting resin includes one or more of epoxy resin, vinyl ester resin, polyester resin, polyurethane resin, phenolic resin, alkyd resin, amino resin, and silicone resin.

[0035] Specifically, the thermosetting resin is epoxy resin, which has a density of 1.16 g / cm3, a viscosity of 8500-10500 mPa•s at 25°C, an elastic modulus of 3476 MPa, and a curing temperature of 150°C. The thermosetting resin is applied into a film to support and fix the carbon fibers and glass fibers.

[0036] An embodiment of the present invention further provides a method for preparing the sheet molding compound as described above, comprising the following steps: A thermosetting resin film is obtained, and large-tow carbon fibers and glass fibers are evenly dispersed on the surface of the thermosetting resin film; specifically, a thermosetting resin is placed in a resin tank and evenly scraped onto a carrier film below the resin tank to form a thermosetting resin film.

[0037] The thermosetting resin film is covered on the large-tow carbon fiber and glass fiber to obtain a resin adhesive film sandwiching the carbon fiber and glass fiber; that is, the carbon fiber and glass fiber are dispersed between two thermosetting resin films.

[0038] The resin film is rolled to remove air from the interlayer formed between the thermosetting resin films, thereby pre-impregnating the carbon fiber and glass fiber into the thermosetting resin to form a carbon-glass hybrid sheet molding compound preform.

[0039] In some embodiments, during the step of distributing the large-tow carbon fibers and glass fibers on the surface of the thermosetting resin film, the total weight of the large-tow carbon fibers and glass fibers per square meter of the thermosetting resin film is 900-1100 g. By limiting the weight of the large-tow carbon fibers and glass fibers per unit area of the thermosetting resin film, the large-tow carbon fibers and glass fibers are uniformly distributed on the thermosetting resin film, thereby ensuring the strength and load-bearing capacity of the sheet molding compound.

[0040] Specifically, the total weight of the large-tow carbon fiber and glass fiber per square meter of the thermosetting resin film includes, but is not limited to, 900 g, 940 g, 980 g, 1000 g, 1020 g, 1060 g, or 1100 g.

[0041] In some embodiments, in the step of distributing large-tow carbon fibers and glass fibers on the surface of the thermosetting resin film, the thermosetting resin film moves at a speed of 2 to 8 m / min.

[0042] Specifically, a thermosetting resin film is placed below the discharge end of the rotary cutter and moves at a speed of 2 to 8 m / min so that the thermosetting resin film can bear a specific weight of carbon fibers and glass fibers per unit area.

[0043] One embodiment of the present invention provides a vehicle trim part, molded from any of the sheet molding compounds described above, or from a sheet molding compound prepared by any of the methods described above. The vehicle trim part produced in this embodiment exhibits a unique forged texture on its surface, meeting user demands for personalized styling of interior and exterior vehicle trim. Specifically, the vehicle trim part includes, but is not limited to, exterior body panels and interior and exterior trim products.

[0044] In some embodiments, the compression molding conditions are: the mold is preheated at 130-140° C. for 30-45 seconds, the molding pressure is 10-12 MPa, and the holding time is 15-20 minutes.

[0045] It should be noted here that different types of thermosetting resins have different curing temperatures, and thus the temperature of the mold during the molding process is also different. The difference between the mold temperature and the curing temperature is 10~15°C.

[0046] An embodiment of the present invention further provides a vehicle, comprising the vehicle trim as described above.

[0047] The present invention is further described below with reference to the following examples.

[0048] Example 1 This embodiment is used to illustrate the sheet molding compound, vehicle trim, and preparation method thereof disclosed in the present invention.

[0049] The preparation of sheet molding compound includes the following steps: carbon fiber (GX400, Jilin Guoxing) and glass fiber (E6, China Jushi) with a tow specification of 50K are cut to a length of 25.0 mm and physically compounded with epoxy resin (EP04695-1, Zhidang Technology) to prepare the sheet molding compound, in which the resin content is 50%, the carbon fiber to glass fiber ratio is 3:1, and the total weight of large-tow carbon fiber and glass fiber per square meter of epoxy resin film is 1000 g.

[0050] Vehicle trim: After cutting the sheet molding compound to the mold cavity size, place it in the mold and preheat it for 35 seconds. The parts are then manufactured through a compression molding process with a mold temperature of 135°C, a molding pressure of 10 MPa, and a holding time of 13 minutes.

[0051] Example 2 This example is used to illustrate the sheet molding compound, vehicle trim, and preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 1, except that the ratio of carbon fiber to glass fiber is 1:1.

[0052] Example 3 This example is used to illustrate the sheet molding compound, vehicle trim, and preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 1, except that the ratio of carbon fiber to glass fiber is 1:3.

[0053] Example 4 This example is used to illustrate the sheet molding compound, vehicle trim, and preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 1, except that the resin content in the sheet molding compound is 55%.

[0054] Example 5 This example is used to illustrate the sheet molding compound, vehicle trim, and preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 1, except that the resin content in the sheet molding compound is 60%.

[0055] Comparative Example 1 Comparative Example 1 is used to compare and illustrate the sheet molding compound, vehicle trim, and preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 1, except that it does not contain glass fiber.

[0056] Comparative Example 2 Comparative Example 2 is used to compare and illustrate the sheet molding compound, vehicle trim, and preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 1, except that it does not contain carbon fiber.

[0057] The following performance tests were performed on the sheet molding compounds and vehicle body panels prepared in the above examples and comparative examples: 1. Conduct density test on sheet molding compound according to GB / T 1033.1-2008.

[0058] 2. Test the tensile strength and tensile modulus of the body panels according to GB / T 1447-2005.

[0059] 3. Test the bending strength and bending modulus of the vehicle body panels according to GB / T 1449-2005.

[0060] 4. Evaluate the cost of sheet molding compound materials based on the cost and content of large-tow carbon fiber, glass fiber and epoxy resin materials.

[0061] 5. Evaluate the cost change of body panel components compared to Comparative Example 1 based on the material properties and equivalent stiffness model of large-tow carbon fiber, glass fiber, and epoxy resin. Component costs are calculated using the equivalent stiffness model. For example, based on the thickness and Young's modulus of Comparative Example 1 and the Young's modulus of Example 1, the required component thickness of Example 1 to achieve the same performance as Comparative Example 1 is calculated. Based on the component thicknesses of Comparative Example 1 and Example 1, the component weights of Comparative Example 1 and Example 1 are calculated. These weights are then multiplied by the material cost to determine the component cost.

[0062] 6. Visually observe the surface texture of the body panels.

[0063] The test results are shown in Table 1.

[0064] Table 1 From the test results of Examples 1 to 3 and Comparative Examples 1 to 2 in Table 1, it can be seen that as the content of large-tow carbon fiber in the sheet molding compound increases, the vehicle accessories prepared from the sheet molding compound have better mechanical properties, but the cost increases relatively. When the glass fiber content in the reinforcing phase of the sheet molding compound is 25%, its component cost is 88.0% of that of the large-tow carbon fiber reinforced sheet molding compound. When the glass fiber content in the reinforcing phase of the sheet molding compound is 50%, its component cost is 94.6% of that of the large-tow carbon fiber reinforced sheet molding compound. However, when the glass fiber content in the reinforcing phase exceeds 50%, the performance of the sheet molding compound material decreases, and the amount of material required for the same component performance increases, so the component cost is higher. In addition, when the glass fiber content in the reinforcing phase exceeds 50%, the cost of the component is increased. Figure 1 It can be seen that flocculent glass fibers are clearly visible on the surface of the SMC body panel. The test results of Examples 1, 4 and 5 show that the content of thermosetting resin in the SMC affects the material properties of the SMC.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A sheet molding compound, characterized in that The sheet molding compound comprises large-tow carbon fiber, glass fiber and thermosetting resin, wherein the large-tow carbon fiber is a carbon fiber with a tow specification of not less than 48K; the mass ratio of the large-tow carbon fiber to the glass fiber is (75~25):(25~75), and the mass content of the thermosetting resin in the sheet molding compound is 45%~65%.

2. The sheet molding compound according to claim 1, wherein The mass ratio of the large-tow carbon fiber to the glass fiber is 3:1, 1:1 or 1:

3.

3. The sheet molding compound according to claim 1, wherein The tow specification of the large tow carbon fiber is 50K; And / or, the mass content of the thermosetting resin in the sheet molding compound is 50%, 55% or 60%.

4. The sheet molding compound according to claim 1, wherein The length of the large-tow carbon fiber is 6-30 mm, and the length of the glass fiber is 6-30 mm.

5. The sheet molding compound according to claim 1, wherein The large-tow carbon fiber has a tensile strength of ≥4390 MPa and a tensile modulus of ≥252 GPa.

6. The sheet molding compound according to claim 1, wherein The glass fiber includes one or more of E-type untwisted yarn, C glass fiber, and S glass fiber; and / or, the thermosetting resin comprises one or more of epoxy resin, vinyl ester resin, polyester resin, polyurethane resin, phenolic resin, alkyd resin, amino resin, and silicone resin; And / or, the viscosity of the thermosetting resin is 8500-10500 mPa·s.

7. The method for preparing a sheet molding compound according to any one of claims 1 to 6, wherein: The following steps are involved: Obtaining a thermosetting resin film, and uniformly dispersing large-tow carbon fibers and glass fibers on the surface of the thermosetting resin film; Covering the large-tow carbon fiber and glass fiber with the thermosetting resin film to obtain a resin film sandwiching the carbon fiber and glass fiber; The resin film is rolled and degased to obtain a sheet molding compound preform.

8. The method for preparing a sheet molding compound according to claim 7, wherein: In the step of dispersing large-tow carbon fibers and glass fibers on the surface of the thermosetting resin film, the total weight of the large-tow carbon fibers and the glass fibers on each square meter of the thermosetting resin film is 900-1100 g.

9. A vehicle trim, characterized in that: Compression molding of the sheet molding compound according to any one of claims 1 to 6, or compression molding of the sheet molding compound prepared by the preparation method according to claim 7 or 8.

10. A vehicle, characterized in that: The vehicle trim according to claim 9 is included.

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