A high-strength, high-modulus carbon fiber ultrathin prepreg, its preparation method and application

Abstract

This invention discloses a method for preparing a high-strength, high-modulus carbon fiber ultrathin prepreg, comprising: spreading high-strength, high-modulus carbon fibers to obtain flat fiber bundles, then stacking and pressing them with a resin film placed above and below them; under the action of temperature and pressure, allowing the resin to fully impregnate the fiber bundles; and then cooling, coating, and winding. The high-strength, high-modulus carbon fiber is one of M40X, M55J, M60J, or higher grade carbon fibers, with a tensile modulus >377 GPa. This invention also discloses the high-strength, high-modulus carbon fiber ultrathin prepreg prepared by the above method and its applications. The spreading roller surface used in this invention is made of polytetrafluoroethylene, and the limiting roller surface is made of ceramic, solving the problems of easy fuzzing and fiber breakage of high-strength, high-modulus carbon fibers, and avoiding corrosion between carbon fibers and metals. The prepreg prepared by this invention has advantages such as high specific strength, high specific modulus, corrosion resistance, and stable structural dimensions, and has broad application prospects in aerospace and other fields.

Description

Technical Field

[0001] This invention relates to the field of high-performance fiber composite materials technology, specifically to a high-strength, high-modulus carbon fiber ultrathin prepreg, its preparation method, and its application. Background Technology

[0002] Carbon fiber reinforced resin matrix composites are widely used in the aerospace industry due to their lightweight, high specific strength, high specific modulus, and excellent comprehensive performance. Carbon fiber prepreg is a composition of resin matrix and reinforcement made by impregnating continuous fibers or fabrics with a resin matrix under strictly controlled conditions; it is an intermediate material in the manufacture of composite materials. The quality of the prepreg directly affects the quality of the composite material, therefore, prepreg is of great significance to the application and development of composite materials. High-modulus carbon fiber, due to its high specific modulus, low coefficient of thermal expansion, dimensional stability, good resistance to high and low temperatures, and good electrical conductivity, is an irreplaceable and important material for satellite structural components, precision optical instruments, and antennas.

[0003] Standard carbon fiber prepregs have a single-layer thickness of approximately 0.125 mm, while ultra-thin prepregs refer to prepregs with a single-layer thickness of 0.08 mm or less. Compared to conventional prepregs, ultra-thin prepregs have a reduced thickness, making it easier to expel interlayer air bubbles, resulting in more uniform fiber and resin impregnation. The thinner prepregs also help to delay and inhibit the initiation and propagation of matrix cracks.

[0004] Due to dispersibility and the lag in processing methods, the overall mechanical properties of composite materials prepared from ultrathin prepregs are generally slightly lower than those prepared from conventional prepregs. However, ultrathin prepregs exhibit superior overall mechanical properties when applied to parts with fewer ply numbers, increasing the design flexibility of ply directions and showing broad application prospects in the thinner regions of aircraft.

[0005] T300 (tensile strength 4900MPa, tensile modulus 230GPa), T700 (tensile strength 4900MPa, tensile modulus 230GPa), T800 (tensile strength 5880MPa, tensile modulus 294GPa), M40J (tensile strength 4400MPa, tensile modulus 377GPa), the T series represents the high-strength series, and MJ represents the high-strength and high-modulus series. As the modulus grade of carbon fiber increases, the elongation at break of carbon fiber decreases, which can alleviate the problem of low tensile force during processing. However, high modulus carbon fiber is brittle, prone to fuzzing, and prone to fiber breakage.

[0006] The elongation at break of carbon fiber is one of the important indicators of material strength and toughness. Higher elongation generally indicates better toughness and stronger tensile properties. High-modulus carbon fibers have a high degree of graphitization, high tensile modulus, and low elongation. Through the preparation of prepregs from high-modulus, high-performance carbon fibers such as M40X, M55J, M60J, and M65J, both domestically and internationally, it was found that high-modulus carbon fibers are brittle, making it difficult to avoid fraying and breakage. This significantly impacts the mechanical properties, appearance quality, molding efficiency, and yield of the prepreg.

[0007] To prepare ultrathin prepregs, carbon fibers need to be spread to thin the individual filaments and minimize fiber damage during the molding process. Spreading refers to widening and thinning the fiber bundle using certain methods, while ensuring that the mechanical properties of the fibers are not damaged and that there is no fiber breakage or fuzzing.

[0008] Patent document CN106903909B discloses a method for preparing ultrathin prepreg, including steps such as fiber layer preparation, resin layer preparation, and ultrathin prepreg preparation. The method uses a yarn spreading method to prepare the fiber layer, resulting in high-quality ultrathin prepreg with larger dimensions.

[0009] Patent document CN116373163A discloses a high-precision carbon fiber prepreg production process, including: preparing unidirectional reinforcing carbon fibers and matrix resin; arranging the unidirectional reinforcing carbon fibers in the prepreg after a spreading treatment; using release paper as a carrier, coating the matrix resin to form a resin film of a certain mass; adhering the resin film on the release paper to both sides of the uniformly spread unidirectional reinforcing carbon fibers; and applying pressure at room temperature to 120°C to completely impregnate the resin with the sheet-like reinforcing carbon fibers. This invention can ensure the accuracy and stability of the fiber areal density of the prepreg.

[0010] Although existing technologies have been used to study the preparation of ultrathin prepregs, with the increasing demand for high-modulus fibers in the market, high-modulus and high-performance carbon fiber raw materials such as M40X, M55J, M60J, and M65J have emerged. However, there are no reports on how to prepare ultrathin prepregs using these carbon fiber raw materials. There is an urgent need to develop technologies to apply high-modulus and high-performance prepregs to various fields such as aerospace.

[0011] In addition, carbon fiber is prone to galvanic corrosion when it comes into contact with metal materials, which can cause corrosion failure of the metal materials and affect the service life of the metal rollers. As the metal rollers are gradually corroded, the damage to the carbon fiber will increase, which will increase the difficulty of finishing and affect the quality of the prepreg.

[0012] Currently, there are some applications of ultra-thin prepregs made from T700, T800, and M40 grade carbon fibers in China. However, there are no technologies or products in the domestic market for making ultra-thin prepregs from high-strength, high-modulus carbon fibers such as M40X, M55J, and above.

[0013] In summary, the preparation of high-strength, high-modulus M40X, M55J and above ultrathin prepregs can reduce weight and increase rigidity for products such as spacecraft in the aerospace and aviation fields, increase the designability of ultrathin thickness areas for lightweight thin-layer products in the aerospace field under application environments, and enhance the mechanical properties and interlayer properties of carbon fiber ultrathin prepregs. Summary of the Invention

[0014] To address the aforementioned technical problems, this invention provides a method for preparing high-strength, high-modulus carbon fiber ultrathin prepreg. This method is simple, easy to operate, and highly designable, and is suitable for preparing high-strength, high-modulus carbon fiber ultrathin prepregs of M40X, M55J, M60J, and higher grades.

[0015] A method for preparing a high-strength, high-modulus carbon fiber ultrathin prepreg includes the following steps:

[0016] High-strength, high-modulus carbon fibers are unfurled to obtain flat fiber bundles. The fiber bundles are then stacked and pressed together with resin films placed above and below them. Under the action of temperature and pressure, the resin fully impregnates the fiber bundles. After cooling, coating, and winding, the high-strength, high-modulus carbon fiber ultrathin prepreg is obtained. The high-strength, high-modulus carbon fiber is one of the following grades: M40X, M55J, M60J, and above, with a tensile modulus > 377 GPa.

[0017] Preferably, the specific steps for spreading high-strength, high-modulus carbon fibers to obtain flat fiber bundles are as follows: multiple bundles of the high-strength, high-modulus carbon fibers are hung on a yarn rack and processed sequentially through a yarn collecting plate, a yarn spreading comb, a yarn spreading roller area, and a limiting roller.

[0018] Preferably, the surface of the yarn spreading roller is made of polytetrafluoroethylene, and the surface of the limiting roller is made of ceramic.

[0019] The yarn spreading rollers of this invention all use polytetrafluoroethylene (PTFE) on the surface of the metal roller. The PTFE layer is tightly fitted onto the outside of the metal yarn spreading roller, which can reduce the friction between the fiber and the roller, and reduce damage such as fuzz and broken fibers. Because PTFE has high stability, is difficult to dissolve, and does not flow above its melting point, it can be used for a long time at temperatures ranging from -180 to 260°C.

[0020] The limiting roller of this invention is made of ceramic material. Ceramic has advantages such as high temperature resistance, high temperature oxidation resistance, wear resistance, and corrosion resistance. Adding a ceramic layer to the surface of the metal core allows the ceramic coating to withstand temperatures up to 600°C and maintain good stability at temperatures below 200°C. It can also effectively block the corrosion of the metal matrix material by carbon fiber, extend the service life of the metal core pressure roller, and effectively solve the problem of carbon fiber corrosion of the metal roller.

[0021] Preferably, the thickness of the polytetrafluoroethylene layer is 10-20 mm. This thickness of polytetrafluoroethylene layer facilitates processing and provides excellent heat transfer performance.

[0022] Preferably, the yarn spreading roller area is divided into Zone I and Zone II. Zone I includes two yarn spreading combs S1 and S2, and multiple yarn spreading rollers located between the two yarn spreading combs. The yarn spreading combs comb the fiber path, and the yarn spreading rollers apply a small amount of tension to spread the yarn. Zone II includes multiple yarn spreading rollers. By adjusting the position between the multiple yarn spreading rollers, the yarn spreading effect is increased.

[0023] The spreading roller and limiting roller areas, in addition to spreading the yarn, also control the width of the carbon fiber prepreg. The width of the carbon fiber prepreg is variable throughout the entire area from spreading roller I and II to the limiting roller. The spreading roller and limiting roller expand the fiber bundle and then limit it to a fixed width by adjusting the yarn feeding method and gradually reducing the width.

[0024] Preferably, the yarn spreading comb S1, yarn spreading comb S2, and limiting roller are used in combination to gradually reduce the width of the high-strength, high-modulus carbon fiber ultrathin prepreg prepared subsequently. Specifically, the yarn spreading comb S1 and yarn spreading comb S2 work together to reduce the width of the high-strength, high-modulus carbon fiber ultrathin prepreg by 5-10 mm, and the yarn spreading comb S2 works with the limiting roller to reduce the width of the high-strength, high-modulus carbon fiber ultrathin prepreg by 0-5 mm.

[0025] Preferably, the resin includes epoxy resin or cyanate ester.

[0026] Preferably, the temperature is 55–100°C and the pressure is 0.1–0.4 MPa.

[0027] Preferably, during the pressing and impregnation process, five or more sets of pressure rollers are used to establish a temperature gradient, so that the resin can fully penetrate into the carbon fiber.

[0028] This invention also provides a high-strength, high-modulus carbon fiber ultrathin prepreg prepared by the above-described method. The high-strength, high-modulus carbon fiber ultrathin prepreg of this invention has advantages such as high specific strength, high specific modulus, good designability, water and moisture resistance, corrosion resistance, dimensional stability, fatigue resistance, and creep resistance.

[0029] Preferably, the theoretical thickness of a single layer of the high-strength, high-modulus carbon fiber ultrathin prepreg is 0.03 to 0.08 mm.

[0030] Preferably, the resin content in the high-strength, high-modulus carbon fiber ultrathin prepreg is 25-55% by mass.

[0031] This invention also provides applications of the aforementioned high-strength, high-modulus carbon fiber ultrathin prepreg in the aerospace, aviation, or electronics fields. The high-strength, high-modulus carbon fiber ultrathin prepreg of this invention possesses advantages such as high specific strength, high specific modulus, good designability, water and moisture resistance, corrosion resistance, dimensional stability, fatigue resistance, and creep resistance. It has broad application prospects in structures such as satellite bodies, trusses, cameras, antenna supports, parabolic antenna reflectors, or solar cell substrates.

[0032] A carbon fiber composite material is prepared from the aforementioned high-strength, high-modulus carbon fiber ultrathin prepreg. The composite material prepared from the carbon fiber ultrathin prepreg of this invention has a tensile modulus higher than 348 GPa, which is the highest tensile modulus among domestically produced high-strength, high-modulus carbon fiber ultrathin prepregs currently available.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) This invention provides a method for preparing high-strength, high-modulus carbon fiber ultrathin prepreg, which can solve the problem that there are no technologies and products for preparing ultrathin prepregs of high-strength, high-modulus carbon fibers of M40X, M55J and above in the current domestic market. In the field of composite material structural components, it can highlight the designability of the ultrathin thickness area and enhance the mechanical properties and interlaminar properties of the carbon fiber ultrathin prepreg.

[0035] (2) The present invention uses the film method to make the resin in the prepreg uniformly distributed, and the resin content can be made lower. The prepared composite material has small void defects, good mechanical properties, and saves solvent.

[0036] (3) The high-strength, high-modulus carbon fiber ultrathin prepreg prepared by the method of the present invention has the advantages of high specific strength, high specific modulus, good designability, water and moisture resistance, corrosion resistance, stable structural dimensions, fatigue resistance and creep resistance, and has broad application prospects in the fields of aviation, aerospace and electronics.

[0037] (4) The tensile modulus of the composite material prepared by the carbon fiber ultrathin prepreg of the present invention is higher than 348 GPa, which is the highest tensile modulus among the ultrathin prepregs prepared by domestic high-strength and high-modulus carbon fibers. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the mixing process in the embodiment;

[0039] Figure 2 This is a schematic diagram of the adhesive application in the embodiment;

[0040] Figure 3These are photographs of the adhesive application process in the embodiments;

[0041] Figure 4 This is a schematic diagram of the yarn spreading area I in the embodiment;

[0042] Figure 5 This is a schematic diagram of the yarn spreading area II in the embodiment;

[0043] Figure 6 The yarn spreading roller in the embodiment ( Figure 6 a) and the limiting roller ( Figure 6 b) Schematic diagram of the structural form;

[0044] Figure 7 This is a schematic diagram of the yarn path in the embodiment;

[0045] Figure 8 These are photographs of the apparent quality of the prepreg in the embodiments. Detailed Implementation

[0046] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0047] The embodiment provides a method for preparing ultrathin prepreg of high-strength and high-modulus carbon fiber, which is applicable to the preparation of ultrathin prepreg of high-strength and high-modulus carbon fibers of M40X, M55J, M60J and above.

[0048] Example 1

[0049] The preparation method of high-strength, high-modulus carbon fiber ultrathin prepreg in this embodiment includes two parts. First, a uniform and flat resin film of a certain width is prepared. Then, the resin film is composite prepreged with a certain number of fiber bundles under certain temperature and pressure, finally producing a high-strength, high-modulus carbon fiber ultrathin prepreg that meets the requirements. The specific preparation method is as follows:

[0050] Resin film preparation: Place the resin in an oven and bake it evenly. Set the oven temperature to 40℃ (1h) - 50℃ (1h) - 55℃ (0.5h), with a baking temperature accuracy of ±3℃. During the baking process, check the state of the resin in the oven every 10-20 minutes. The resin will gradually change from surface melting to resin leveling, and finally to a molten state with good fluidity and smooth pouring. Turn on the coating machine and turn on the mold temperature controller to heat the resin tank to (55±2)℃ to prepare for threading the release paper and attaching auxiliary tooling. After the resin tank temperature stabilizes at (55±2)℃, pour the molten resin into the tank and lower the comma roller. Separate the bonding roller from the coating roller and turn on the coating roller separately to rotate for 10-20 minutes to make the mixing process more uniform. Figure 1 );

[0051] Bring the laminating roller and the adhesive coating roller close together. Figure 2The gap between the comma roller and the glue-applying roller is set to 0.02mm. The resin is evenly coated onto the release paper surface via glue transfer from the glue-applying roller. The release paper force is set to 10N, the glue-applying speed to 10m / min, the cooling plate temperature to 10℃, and the glue content error to 1%. The glue-applying process is stable. Figure 3 ).

[0052] The thickness or basis weight of a product is calculated by analyzing the energy absorption of X-rays on the product under test using an X-ray thickness gauge. For a specific emission source emitting specific rays that penetrate continuously produced composite materials, and when the composite material has a fixed density, the signal strength received by the receiver depends only on the material thickness. The thickness gauge has a scanning accuracy of 0.1% or 0.1 gsm. The gauge displays the total basis weight of the release paper and the adhesive film. During production, a sample of the release paper needs to be weighed to obtain the basis weight (film thickness) of the adhesive film, enabling real-time monitoring of the film thickness (or film basis weight).

[0053] The basis weight is measured using an X-ray thickness gauge, which displays the total basis weight of the release paper and the adhesive film. During production, a sample of the release paper needs to be weighed to determine the basis weight of the adhesive film, which is 25 g / m². 2 .

[0054] The film will be coated with PE film, rolled up, sealed and packaged, and then placed in a -18℃ cold storage for later use.

[0055] After the film preparation is completed, the preparation of the ultrathin prepreg begins.

[0056] The fiber used is CNIQ M55 high-strength, high-modulus carbon fiber (M55J grade), with a tensile strength ≥4000MPa, tensile modulus ≥530GPa, elongation at break ≥0.7%, and density ≥1.8g / cm3. The resin used is cyanate ester as the raw material for preparing the film, which can withstand temperatures up to 190℃ and can be guaranteed to serve in temperatures from -150℃ to 150℃ without a decrease in mechanical properties of more than 10%.

[0057] First, 114 spindles of fiber are pre-hanging on a yarn rack. Multiple fiber bundles then sequentially pass through a yarn collecting plate, a yarn spreading comb, a yarn spreading roller area, and a limiting roller into the impregnation and pressing area. The fiber bundles are then laminated in three layers—upper and lower adhesive films—to form an ultra-thin prepreg under pressure and temperature.

[0058] The surface layer of the yarn spreading roller is made of polytetrafluoroethylene, and the surface layer of the limiting roller is made of ceramic. Figure 6 );

[0059] The width of the ultra-thin carbon fiber prepreg is variable, gradually decreasing from the opening combs S1 and S2 to the limiting rollers: 1010mm → 1005mm → 1000mm. The width of the high-strength, high-modulus ultra-thin prepreg is 1000mm. Figure 7 );

[0060] In this process, after the high-strength, high-modulus carbon fiber is unrolled, it enters the impregnation and pressing zone. The upper and lower adhesive films are stacked and pressed together with the flat fiber bundle in three layers. Five sets of pressure rollers are used to establish a temperature gradient of 50℃-55℃-55℃-55℃-50℃, which allows the resin to penetrate into the interior of the carbon fiber. After passing through a cooling unit, a coating unit, and a winding unit, a high-strength, high-modulus carbon fiber ultra-thin prepreg is obtained.

[0061] The high-strength, high-modulus carbon fiber ultrathin prepreg prepared in this embodiment has a theoretical single-layer thickness of 0.07-0.08 mm, which can meet the service requirements of high and low temperature alternating environment and has a high mechanical property retention rate.

[0062] Carbon fiber composite products prepared using the above-mentioned prepreg have a porosity of up to 1%, a dense internal structure, and extremely low void ratio.

[0063] The composite material products prepared from the above prepregs have the following properties: tensile strength of 2361 MPa, tensile modulus of 348 GPa, 0° compressive strength of 734 MPa, flexural strength of 1135 MPa, and interlaminar shear strength of 68 MPa. The tensile modulus is much higher than the index level of T-series carbon fiber composites.

[0064] In addition to the embodiments described above, the patented product of this invention may have other implementation methods. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by this invention.

Claims

1. A method for preparing a high-strength, high-modulus carbon fiber ultrathin prepreg, characterized in that, Includes the following steps: High-strength, high-modulus carbon fibers are unfurled to obtain flat fiber bundles. The fiber bundles are then stacked and pressed together with resin films placed above and below the fiber bundles. Under the action of temperature and pressure, the resin fully impregnates the fiber bundles. After cooling, coating, and winding, the high-strength, high-modulus carbon fiber ultrathin prepreg is obtained. The high-strength, high-modulus carbon fiber is one of M40X, M55J, M60J and higher grade carbon fibers, with a tensile modulus >377Gpa. The specific steps for spreading high-strength, high-modulus carbon fibers to obtain flat fiber bundles are as follows: multiple bundles of the high-strength, high-modulus carbon fibers are hung on a yarn rack and processed sequentially through a yarn collecting plate, a yarn spreading comb, a yarn spreading roller area, and a limiting roller. The yarn spreading roller area is divided into Zone I and Zone II. Zone I includes two yarn spreading combs S1 and S2, and multiple yarn spreading rollers located between the two yarn spreading combs. The yarn spreading combs comb the fiber path, and the yarn spreading rollers apply a small amount of tension to spread the yarn. Zone II includes multiple yarn spreading rollers. By adjusting the position between the multiple yarn spreading rollers, the yarn spreading effect is increased.

2. The preparation method according to claim 1, characterized in that, The surface of the spreading roller is made of polytetrafluoroethylene, and the surface of the limiting roller is made of ceramic.

3. The preparation method according to claim 1, characterized in that, The yarn spreading combs S1 and S2, along with the limiting roller, work together to gradually reduce the width of the high-strength, high-modulus carbon fiber ultrathin prepreg prepared subsequently. Specifically, the yarn spreading combs S1 and S2 work together to reduce the width of the high-strength, high-modulus carbon fiber ultrathin prepreg by 5-10 mm, while the yarn spreading comb S2 works with the limiting roller to reduce the width of the high-strength, high-modulus carbon fiber ultrathin prepreg by 0-5 mm.

4. The preparation method according to claim 1, characterized in that, During the pressing and impregnation process, five or more sets of pressure rollers are used to establish a temperature gradient, allowing the resin to fully penetrate the interior of the carbon fiber.

5. The high-strength, high-modulus carbon fiber ultrathin prepreg prepared by the preparation method according to any one of claims 1-4.

6. The high-strength, high-modulus carbon fiber ultrathin prepreg according to claim 5, characterized in that, The theoretical thickness of a single layer of the high-strength, high-modulus carbon fiber ultrathin prepreg is 0.03~0.08mm; the resin content in the high-strength, high-modulus carbon fiber ultrathin prepreg is 25~55% by mass.

7. The application of the high-strength, high-modulus carbon fiber ultrathin prepreg according to claim 5 or 6 in the aerospace or electronics fields.

8. A carbon fiber composite material, prepared from the high-strength, high-modulus carbon fiber ultrathin prepreg as described in claim 5 or 6.

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