A method of improving the transverse strength of continuous fiber / resin matrix composites

Abstract

The application discloses a preparation method for improving the transverse strength of continuous fiber / resin matrix composite material and belongs to the field of composite material preparation. The application utilizes tension control and yarn spreading device to adjust yarn tension and spread yarn, ensures yarn flatness and easy resin infiltration; the pre-impregnation mixing cavity contains an ultrasonic probe, which is beneficial to uniform dispersion of CNTs and increases the filament gap by ultrasonic vibration, facilitates deep mixing with CNTs and deep infiltration with resin glue solution; a heating device is arranged at the printing outlet, the resin curing system in the pre-impregnated filament is heated to a gel state, which is used for maintaining the orientation state of CNTs and facilitating the preparation of pre-impregnated material; a pressure applying device is provided with a heating device, which is used for ensuring the flatness of continuous fibers, enhancing resin infiltration and promoting resin pre-curing; the spraying device moves transversely along the printed pre-impregnated material, and CNTs are laid on the surface of the pre-impregnated material in a transverse orientation state after being straightened by a small nozzle, so that the transverse strength of the continuous fiber / resin matrix composite material is enhanced.

Description

Technical Field

[0001] This invention belongs to the field of composite material preparation, and more specifically, relates to a method for improving the transverse strength of continuous fiber / resin-based composite materials. Background Technology

[0002] Continuous fiber / resin matrix composites possess characteristics such as high specific strength, high specific modulus, and designability of performance and function, significantly reducing the weight of engineering components and representing a high-tech material for the informatization and intelligentization of engineering components. However, the high performance of composite materials is mainly reflected in the fiber direction. In unidirectional composites, the transverse tensile strength is extremely low and the impact damage resistance is weak compared to the fiber direction due to the limitations of the resin matrix and fiber-resin interface properties. This greatly limits the design flexibility of composite materials and restricts their application in multifunctional engineering components. Therefore, modifying continuous fiber / resin matrix prepregs is key to optimizing and improving the overall performance of composite materials.

[0003] To further improve the performance of continuous fiber / resin-based composites, the transformation of composite systems from two-phase to three-phase or even multi-phase systems has become an important research direction in this field. Among them, carbon nanotubes (CNTs) theoretically possess an ultra-high strength of 180 GPa and an ultra-high modulus of over 1 TPa. Their theoretical tensile strength is 100 times that of steel, while their density is only 1 / 7 to 1 / 6 that of steel. They are considered one of the most promising reinforcing phase materials for advanced resin-based composites, and their application in improving the mechanical properties of resin-based composites has been a research hotspot both domestically and internationally in recent years. CNTs can achieve ordered arrangement from disordered arrangement in composites and orientation perpendicular to the fiber direction in the plane, thus significantly improving the mechanical properties between transverse fibers in composites.

[0004] Currently, the most commonly used methods for orienting CNTs in continuous fiber composites include electric field, magnetic field, and flow field orientation. Electric field orientation requires a high-voltage power supply, posing certain operational risks, and for conductive fibers, electric field orientation of CNTs between transverse fibers is impossible. Magnetic field orientation requires CNTs to be loaded with magnetic nanoparticles, which is detrimental to the mechanical properties of the composite material. Furthermore, magnetic field orientation equipment is heavy, and the orientation process is complex, resulting in extremely low efficiency. Flow field orientation of CNTs between continuous fibers can be achieved through RTM (Reverse Molecular Transformation), but due to the obstruction effect of the fibers, a concentration gradient of CNTs forms between the transverse fibers, leading to unsatisfactory orientation results. Therefore, there is an urgent need to find a convenient and easily operable method for orienting CNTs between transverse fibers.

[0005] 3D printing is a primary form of additive manufacturing (AM) technology. In recent years, the rapid development of 3D printing technology has enabled the efficient fabrication of continuous fiber / resin-based composite material structures. The combination of 3D printing and fiber-reinforced composites fully leverages the manufacturing advantages of 3D printing and the performance advantages of composite materials, achieving the efficient fabrication of high-performance, high-value-added, and customized composite material structures. This further expands the application scope of fiber-reinforced composites, effectively simplifies product manufacturing processes, improves production efficiency, and is an important component of advanced manufacturing technology.

[0006] Chinese patents CN201710852259, CN201910554138, and CN201910641807 all disclose 3D printing preparation devices for continuous fiber / resin-based prepregs. However, these three devices are only used to prepare continuous fiber / resin-based prepregs and improve the wetting effect between fibers and resin. Currently, there is no method for preparing continuous fiber / resin-based prepregs reinforced with transversely oriented CNTs. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a method for preparing continuous fiber / resin-based composite materials with improved transverse strength.

[0008] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: When preparing continuous fiber / resin-based prepreg using 3D printing technology, CNTs oriented along the fiber direction are mixed into the interior and surface of the continuous fiber through motion orientation, and transversely oriented CNTs are laid on the surface of the continuous fiber / resin-based prepreg, thereby significantly improving the mechanical strength of the composite material, especially the transverse strength, and achieving the purpose of the present invention.

[0009] This invention relates to a method for preparing continuous fiber / resin-based composite materials with improved transverse strength, characterized by the following steps:

[0010] 1) Assemble the 3D printing device

[0011] The 3D printing apparatus includes a fiber placement device, a CNTs dispersion device, a heating device, a prepreg printing device, an ejection device, and a prepreg placement device. The fiber placement device is used to spread continuous fibers before they enter the prepreg printing device. The CNTs dispersion device is used to uniformly disperse CNTs in the resin curing system. The prepreg printing device includes a prepreg mixing chamber and a driving device, used to fully impregnate the continuous fibers with the CNTs-containing resin solution, and under the action of the driving device, print the fully impregnated continuous fibers on the prepreg placement device. The ejection device includes a resin tank and a driving device; under the action of the driving device, the resin tank moves along a predetermined direction and speed, and ejects the CNTs-containing resin solution. The heating device is used to heat the CNTs-containing resin solution in the prepreg mixing chamber and the resin tank. The prepreg placement device is used to place the printed continuous fiber / resin-based prepreg. The cooling device is used to cool the continuous fiber / resin-based prepreg printed above the prepreg placement device.

[0012] 2) Preparations before printing

[0013] The release paper is fixed onto the prepreg laying device; the continuous fibers are placed onto the fiber laying device; CNTs and the resin curing system are weighed, wherein the mass content of CNTs is 0.3% to 0.75%; the CNTs dispersion device is started to disperse and mix the CNTs and the resin curing system to prepare a CNTs-containing resin solution; the CNTs-containing resin solution is added to the prepreg mixing chamber and the resin tank; the heating device is started to heat the prepreg mixing chamber and the resin tank to 20 to 30°C below the gel temperature of the resin curing system.

[0014] 3) Utilizing 3D printing equipment to prepare continuous fiber / resin-based prepregs

[0015] The servo motor of the prepreg printing device is activated, driving the print outlet to move in a predetermined direction at a speed of 5–15 cm / min. This propels the continuous fiber / resin-based prepreg bundle onto the release paper. When the continuous fiber / resin-based prepreg bundle reaches the other end of the release paper, the prepreg printing device automatically rotates 180 degrees under the action of the servo motor to continue printing. This printing step is repeated to obtain CNT-reinforced continuous fiber / resin-based prepreg.

[0016] Start the servo motor of the jetting device to control the resin tank and nozzle, and print the CNTs-containing resin liquid at a speed of 10-20 cm / min along the transverse direction of the continuous fiber on the surface of the CNTs-reinforced continuous fiber / resin-based prepreg. After printing to the required size, a transversely oriented CNTs-reinforced continuous fiber / resin-based prepreg is obtained.

[0017] 4) Continuous fiber / resin-based prepreg prepared by cooling

[0018] The prepared transversely oriented CNTs reinforced continuous fiber / resin-based prepreg was cooled to room temperature;

[0019] 5) Preparation of continuous fiber / resin-based composite materials

[0020] Continuous fiber / resin-based composite materials are prepared by using a compression molding process to prepare continuous fiber / resin-based prepreg cooled to room temperature.

[0021] Preferably, the 3D printing apparatus further includes a cooling device; in step 4), the cooling device is used to cool the prepared transversely oriented CNTs reinforced continuous fiber / resin-based prepreg to room temperature.

[0022] Preferably, the prepreg printing apparatus further includes an instant heating device and a pressure application device, and the prepreg mixing chamber includes a printing outlet; there are two instant heating devices, one located at the printing outlet and the other at the pressure application device; in step 2), the instant heating device is used to heat the temperature at the printing outlet to the gel temperature of the resin curing system; in step 3), the servo motor of the prepreg printing apparatus drives the pressure application device to apply a pressure of 20-30N to the continuous fibers printed on the release paper and heats them to 2-5°C above the gel temperature of the resin curing system.

[0023] Preferably, the CNTs dispersion device includes an ultrasonic probe disposed on the wall of the pre-impregnation mixing chamber and the resin tank, with an ultrasonic frequency of 25–45 kHz.

[0024] Preferably, in step 3), the moving speed of the printing outlet is 5-15 cm / min, and the moving speed of the nozzle is 10-20 cm / min.

[0025] Preferably, the 3D printing apparatus further includes a film placement device; after the continuous fiber / resin-based prepreg prepared in step 4) is cooled to room temperature, a film is placed on its surface using the film placement device for cold storage.

[0026] More preferably, the prepreg laying device includes an infrared automatic sensor tension control device.

[0027] This invention places a continuous fiber yarn roll on an unwinding device, which then conveys the yarn via guide rollers. Tension control and a yarn-spreading device adjust the yarn tension and spread it to ensure good straightness and easy resin impregnation. Ultrasonic probes are installed in the prepreg mixing chamber and resin tank, primarily for further uniform dispersion of CNTs in the resin solution. The ultrasonic waves vibrate the continuous fiber bundle, increasing the gaps between the fibers and facilitating resin impregnation. Several traction guide rollers are installed on the inner wall of the prepreg mixing chamber to constrain the continuous fiber bundle and guide it through the chamber in an S-curve. The yarn feed speed is consistent with the printing exit speed, controlled at 5–15 cm / min, increasing the contact time with the resin and ensuring thorough impregnation with the CNT-containing resin solution. An instant heating device at the printing exit heats the resin curing system in the printed continuous fiber / resin-based prepreg bundle to a gel state, maintaining the orientation of the CNTs along the fiber direction and facilitating prepreg molding. The pressure application device of the instant heating unit further ensures the straightness of the continuous fibers and enhances the wettability with the resin. Under its heating action, the resin curing system is pre-cured, which can better maintain the orientation state of CNTs and facilitate the preparation of prepreg molding. The nozzle of the spraying device moves the CNT-containing resin adhesive along the transverse direction of the printed continuous fiber / resin-based prepreg. The CNTs have a certain straightening effect as they pass through the fine nozzle, and under the traction of the nozzle, they are oriented along the transverse direction of the continuous fiber / resin-based prepreg, thereby enhancing the transverse strength of the continuous fiber / resin-based composite material. In addition, this invention also has the advantages of simple operation and convenient use. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the 3D printing device of the present invention;

[0029] Figure 2 This is a top view of the printing platform.

[0030] In the diagram: 1 is the continuous fiber unwinding roller, 2 is the continuous fiber, 3 is the conveying guide roller, 4 is the tension control and yarn spreading device, 5 is the conveying pressure roller group, 6 is the continuous fiber dry yarn bundle inlet, 7 is the pre-impregnation mixing chamber, 8 is the ultrasonic probe, 9 is the traction guide roller, 10 is the heating rod, 11 is the three-roll grinding device, 12 is the CNTs-containing resin solution, 13 is the printing outlet, 14 is the nozzle, 15 is the pressure heat guide roller, 16 is the tension control device, 17 is the resin tank, 18 is the printing platform, 19 is the transversely oriented CNTs, 20 is the cooling device, and 21 is the unwinding device. Detailed Implementation

[0031] The present invention will be further described below with reference to embodiments; however, the technical solution of the present invention is not limited to the specific embodiments listed below. Any non-essential changes and adjustments made by those skilled in the art based on the above description of the invention are within the scope of protection of the present invention.

[0032] In this invention, the prepreg bundle is a continuous fiber bundle 2 after being impregnated with resin; the prepreg is a bundle of prepreg bundles arranged closely on a prepreg laying device.

[0033] Example 1

[0034] The continuous fiber / resin-based composite material in this embodiment is a continuous carbon fiber / epoxy resin-based composite material, which is made of continuous carbon fiber T700S-12K, epoxy resin curing system and transversely oriented CNTs19. The gel temperature of the epoxy resin curing system is 120°C.

[0035] The 3D printing apparatus for preparing the continuous carbon fiber / epoxy resin matrix composite material in this embodiment includes a fiber placement device, a CNTs dispersion device, a heating device, a prepreg printing device, a jetting device, a prepreg placement device, a cooling device, and a film unwinding device 21, as shown below. Figure 1 As shown.

[0036] The fiber laying device, along the continuous fiber 2 conveying route, includes, from front to back, a continuous fiber unwinding roller 1, a conveying guide roller 3, a tension control and yarn spreading device 4, a conveying pressure roller group 5, the conveying guide roller 3, and a traction guide roller 9. The conveying pressure roller group 5 consists of upper and lower pressure rollers. There are eight traction guide rollers 9 in total, including two traction guide roller groups, each consisting of two traction guide rollers 9.

[0037] The CNTs dispersion device includes two three-roll mills 11 and twelve ultrasonic probes 8. The three-roll mills 11 have an outlet at the bottom.

[0038] The heating device is a heating rod 10.

[0039] The prepreg printing device includes a prepreg mixing chamber 7, a pressure-heated guide roller 15, an instant heating device, a servo motor, and a transmission device. The instant heating device includes an infrared heating device and a temperature sensor. The prepreg mixing chamber 7 has a continuous fiber dry yarn tow inlet 6 and a resin liquid inlet at its top, and a printing outlet 13 at its bottom center. An infrared heating device is installed outside the printing outlet 13 to heat the continuous fiber / resin-based prepreg tow containing CNTs resin liquid 12 flowing out of the printing outlet 13, causing the resin to be in a gel state to fix the orientation of the CNTs, facilitating the molding and preparation of the continuous fiber / resin-based prepreg. The pressure-heated guide roller 15 is equipped with a temperature sensor. The servo motor includes three motors for the X, Y, and Z directions. With the help of the servo motor and the corresponding transmission device, the movement path of the printing outlet 13 in the X, Y, and Z directions can be driven and controlled. The pressure-heated guide roller 15 is fixedly connected to the printing outlet 13.

[0040] The spraying device includes a resin tank 17, a servo motor, and a transmission device. A resin inlet is located at the top of the resin tank 17, and a nozzle 14 is located at the center of the bottom. The servo motor includes three motors for the X, Y, and Z directions. With the help of the servo motor and the corresponding transmission device, the movement path of the nozzle 14 in the X, Y, and Z directions can be driven and controlled.

[0041] The prepreg laying device includes a printing platform 18 and prepreg tension control devices 16 with pulleys arranged on both sides of the printing platform 18. The tension control devices 16 are equipped with infrared automatic sensors.

[0042] The cooling device 20 is a fan.

[0043] Eight traction guide rollers 9 are located inside the prepreg mixing chamber 7. One traction guide roller group is located below the continuous fiber dry yarn bundle inlet 6, and another traction guide roller group is located above the printing outlet 13. The four traction guide rollers 9 are arranged on the left and right sides and staggered vertically to ensure that the continuous fiber bundle has a continuous S-shaped orientation. Heating rods 10 and six ultrasonic probes 8 are installed inside both the prepreg mixing chamber 7 and the resin tank 17. The six ultrasonic probes 8 are arranged on the left and right sides of the inner chamber and staggered vertically to facilitate the uniform dispersion of CNTs and promote the full wetting of the continuous fiber 2 with the CNT-containing resin slurry 12 and deep mixing with the CNTs. Two three-roll milling devices 11 are located above the prepreg mixing chamber 7 and the resin tank 17, respectively connected to the bottom outlet of the three-roll milling devices 11 and the resin slurry inlet at the top of both chambers via hoses. The prepreg placement device is placed below the prepreg printing device and the jetting device. A cooling device 20 is located above the printing platform 18 and is used to cool the prepared continuous fiber / resin-based prepreg. The film laying device 21 is located above the right of the printing platform 18 and is used to protect the prepared continuous fiber / resin-based prepreg by laying a film, which facilitates cold storage.

[0044] When preparing the continuous fiber-reinforced composite material of this embodiment using a 3D printing device, the steps are as follows:

[0045] The release paper is fixed to the surface of the printing platform 18.

[0046] The continuous carbon fiber T700S-12K yarn is placed on the continuous fiber unwinding roller 1, and the continuous fiber 2 is conveyed by the conveying guide roller 3. Under the action of the tension control and yarn spreading device 4, the continuous fiber 2 yarn is spread and has a suitable tension along the axial direction, and then enters the prepreg mixing chamber 7 through the conveying pressure roller group 5, the conveying guide roller 3 and the continuous fiber dry yarn bundle inlet 6.

[0047] Using heating rod 10, the temperature of the prepreg mixing chamber 7 and resin tank 17 is heated to 90°C. The infrared heating device of the printing outlet 13 is activated, raising its internal temperature to 120°C. This temperature converts the CNT-containing resin liquid 12 into a gel state, facilitating the maintenance of CNT orientation and ensuring the molding of the prepreg. The temperature sensor of the pressure heat guide roller 15 is activated, raising the temperature to 125°C, allowing the epoxy resin curing system to pre-cure.

[0048] Weigh 3g of CNTs and 997g of epoxy resin curing system composition, stir them initially with a glass rod, and then add them to two three-roll mills 11. Start the three-roll mills 11 and grind and disperse them 6 times. Then turn on the switch and the resin liquid 12 containing CNTs enters the pre-impregnation mixing chamber 7 and the resin tank 17 through the hose.

[0049] With the ultrasonic probe 8 set to a starting frequency of 45 kHz, under the action of ultrasound, CNTs are dispersed more evenly on the one hand, and the continuous carbon fiber yarns near the ultrasonic probe 8 in the pre-impregnation mixing chamber 7 will jump, thereby increasing the resin wettability.

[0050] The servo motor of the prepreg printing device is activated, first driving the traction guide roller group below the continuous fiber dry yarn tow inlet 6, then passing through four traction guide rollers 9 and the lower traction guide roller group in a continuous S-shape, entering the printing outlet 13; exiting from the printing outlet 13, it is fixedly connected to the tension control device 16. The pressure heat guide roller 15 is linked to the printing outlet 13 and located behind it. As the continuous fiber / resin-based prepreg tow is printed, the pressure heat guide roller 15 contacts the continuous fiber / resin-based prepreg tow and applies a pressure of 20N to it. The pressure heat guide roller 15 applies rolling pressure to the continuous fiber / resin-based prepreg tow along the printing direction, further ensuring the straightness of the continuous fiber / resin-based prepreg tow and enhancing its wettability with the resin; under its heating action, the epoxy resin curing system is pre-cured, which can better maintain the orientation state of CNTs and facilitate the molding and preparation of prepreg. Then, the printing outlet 13 is driven to move in a predetermined direction at a speed of 5 cm / min, causing the continuous fiber 2 to move in the prepreg mixing chamber 7 at a speed of 5 cm / min. Subsequently, the continuous fiber / resin-based prepreg bundle is printed on the printing platform 18 at a speed of 5 cm / min. As the continuous fiber 2 moves, the CNTs in the prepreg mixing chamber 7 are oriented along the fiber direction and are eventually mixed into the interior and surface of the continuous fiber 2 in an oriented state, thereby further enhancing its axial strength. When the continuous fiber / resin-based prepreg bundle reaches the other end of the release paper, the prepreg printing device automatically rotates 180 degrees under the action of the servo motor to continue printing. This printing step is repeated to obtain CNT-reinforced continuous carbon fiber / epoxy resin-based prepreg.

[0051] The servo motor of the jetting device is restarted to control the resin tank 17 and nozzle 14. The nozzle moves rapidly at a speed of 20 cm / min while spraying the CNTs-reinforced continuous carbon fiber / epoxy resin prepreg. As the nozzle 14 moves, the CNTs are oriented along the direction of the nozzle 14. That is, the CNTs are attached to the surface of the CNTs-reinforced continuous carbon fiber / epoxy resin prepreg in a transverse orientation. When the nozzle 14 reaches the other side of the prepreg, the jetting printing device automatically turns 180 degrees under the action of the servo motor to continue printing. This printing step is repeated to form a transversely oriented CNTs layer on the surface of the continuous carbon fiber / epoxy resin prepreg, resulting in a transversely oriented CNTs-reinforced continuous carbon fiber / epoxy resin prepreg.

[0052] During the printing process, under the action of the automatic sensor, the tension control device 16 will automatically lift when it is 1cm away from the printing outlet 13, and will automatically fall when the printing outlet 13 is 1cm away from it, thus compacting the continuous carbon fiber / epoxy resin-based prepreg tow and controlling the tension. This ensures the straightness of the 3D printing of the continuous carbon fiber / epoxy resin-based prepreg tow, thereby ensuring the reliability of the overall performance of the continuous carbon fiber / epoxy resin-based prepreg.

[0053] The cooling device is activated to cool the transversely oriented CNTs19 reinforced continuous carbon fiber / epoxy resin-based prepreg prepared above. After cooling to room temperature, the unwinding device 21 is activated to lay the polyester film placed on it onto the surface of the prepreg. After being moved and compacted by the tension control device 16, the transversely oriented CNTs19 reinforced continuous carbon fiber / epoxy resin-based prepreg is brought to a state suitable for cold storage.

[0054] Take out the 3D-printed transversely oriented CNTs19 reinforced continuous carbon fiber / epoxy resin-based prepreg, cut it to a suitable size and lay it in the mold. Place the mold under a flat vulcanizing machine and mold it according to the epoxy resin curing regime to produce a continuous carbon fiber / epoxy resin-based composite material.

[0055] The continuous carbon fiber / epoxy resin matrix composite material of this embodiment was subjected to a transverse tensile test according to GB / T 3354-2014, and the transverse tensile strength was measured to be 96 MPa, which is 140% higher than that of the continuous carbon fiber / epoxy resin matrix composite material without transverse orientation CNTs reinforcement.

[0056] Example 2

[0057] The difference between this embodiment and Embodiment 1 is that the continuous fiber reinforced composite material in this embodiment is a continuous glass fiber / epoxy resin matrix composite material.

[0058] When preparing the continuous glass fiber / epoxy resin matrix composite material of this embodiment using a 3D printing device:

[0059] Using heating rod 10, the temperature of the prepreg mixing chamber 7 and resin tank 17 is heated to 100°C. The instant heating device of printing outlet 13 is activated, raising its internal temperature to 120°C. The instant heating device of pressure heat guide roller 15 is activated, raising its temperature to 122°C.

[0060] Weigh 5g of CNTs and 995g of epoxy resin curing system composition, stir them initially with a glass rod, and then add them to two three-roll mills 11. Start the three-roll mills 11, and after grinding and dispersing 10 times, turn on the switch, and the CNTs-containing resin liquid 12 enters the pre-impregnation mixing chamber 7 and the resin tank 17 through the hose.

[0061] The ultrasonic probe 8 has a startup frequency set to 25KHz.

[0062] The servo motor of the prepreg printing device is activated, driving the printing outlet 13 to move in a predetermined direction at a speed of 10 cm / min. This causes the continuous fiber 2 to move in the prepreg mixing chamber 7 at a speed of 10 cm / min, and subsequently, the continuous fiber / resin-based prepreg bundle is printed on the printing platform 18 at a speed of 10 cm / min. The driving pressure heat guide roller 15 provides a pressure of 30 N. When the continuous fiber / resin-based prepreg bundle reaches the other end of the release paper, the prepreg printing device automatically rotates 180 degrees under the action of the servo motor to continue printing. This printing step is repeated to obtain CNTs-reinforced continuous glass fiber / epoxy resin-based prepreg.

[0063] The servo motor of the jetting device is restarted to control the resin tank 17 and the nozzle 14. The CNTs-reinforced continuous glass fiber / epoxy resin-based prepreg is moved at a speed of 15 cm / min to print the CNTs-containing resin liquid 12. When the nozzle 14 reaches the other side of the prepreg, the jetting printing device automatically turns 180 degrees under the action of the servo motor to continue printing. This printing step is repeated to obtain a transversely oriented CNTs19-reinforced continuous glass fiber / epoxy resin-based prepreg.

[0064] The continuous glass fiber / epoxy resin matrix composite material of this embodiment was subjected to a transverse tensile test according to GB / T 3354-2014, and the transverse tensile strength was measured to be 90 MPa, which is 125% higher than that of the continuous glass fiber / epoxy resin matrix composite material without CNT transverse orientation reinforcement.

[0065] Example 3

[0066] The difference between this embodiment and Embodiment 1 is that the continuous fiber reinforced composite material in this embodiment is a continuous aramid fiber / epoxy resin matrix composite material.

[0067] When preparing the continuous aramid fiber / epoxy resin-based composite material of this embodiment using a 3D printing device:

[0068] Using heating rod 10, the temperature of the prepreg mixing chamber 7 and resin tank 17 is heated to 95°C. The instant heating device of the printing outlet 13 is activated, raising its internal temperature to 120°C. The instant heating device of the pressure heat guide roller 15 is activated, raising its temperature to 125°C.

[0069] Weigh 7.5g of CNTs and 992.5g of epoxy resin curing system composition, stir them initially with a glass rod, and then add them to two three-roll mills 11. Start the three-roll mills 11, and after grinding and dispersing 10 times, turn on the switch. The resin liquid 12 containing CNTs enters the pre-impregnation mixing chamber 7 and the resin tank 17 through the hose.

[0070] The ultrasonic probe 8 has a startup frequency set to 35KHz.

[0071] The servo motor of the prepreg printing device is activated, driving the printing outlet 13 to move in a predetermined direction at a speed of 15 cm / min. This causes the continuous fiber 2 to move in the prepreg mixing chamber 7 at a speed of 15 cm / min, and subsequently, the continuous fiber / resin-based prepreg tow is printed on the printing platform 18 at a speed of 15 cm / min. The driving pressure heat guide roller 15 provides a pressure of 25 N. When the continuous fiber / resin-based prepreg tow reaches the other end of the release paper, the prepreg printing device automatically rotates 180 degrees under the action of the servo motor to continue printing. This printing step is repeated to obtain CNTs-reinforced continuous aramid fiber / epoxy resin-based prepreg.

[0072] The servo motor of the jetting device is restarted to control the resin tank 17 and the nozzle 14. The CNTs-containing resin liquid 12 is moved at a speed of 10 cm / min along the transverse direction of the CNTs-reinforced continuous aramid fiber / epoxy resin-based prepreg. When the nozzle 14 reaches the other side of the prepreg, the jetting printing device automatically turns 180 degrees under the action of the servo motor to continue printing. This printing step is repeated to obtain a transversely oriented CNTs19-reinforced continuous aramid fiber / epoxy resin-based prepreg.

[0073] The continuous aramid fiber / epoxy resin matrix composite material of this embodiment was subjected to transverse tensile testing according to GB / T 3354-2014, and the transverse tensile strength was measured to be 80 MPa, which is 100% higher than that of the continuous aramid fiber / epoxy resin matrix composite material without transverse orientation CNTs reinforcement.

[0074] Example 4

[0075] The difference between this embodiment and Embodiment 1 is that the continuous fiber reinforced composite material in this embodiment is a continuous PBO fiber / epoxy resin matrix composite material.

[0076] When preparing the continuous PBO fiber / epoxy resin matrix composite material of this embodiment using a 3D printing device:

[0077] Using heating rod 10, the temperature of the prepreg mixing chamber 7 and the resin tank 17 is heated to 95°C. The instant heating device of the printing outlet 13 is activated, raising the internal temperature of the CNTs-containing resin liquid to 120°C. The instant heating device of the pressure heat guide roller 15 is activated, raising its temperature to 123°C.

[0078] Weigh 4g of CNTs and 996g of epoxy resin curing system composition, stir them initially with a glass rod, and then add them to two three-roll mills 11. Start the three-roll mills 11, and after grinding and dispersing 8 times, turn on the switch, and the CNTs-containing resin liquid 12 enters the pre-impregnation mixing chamber 7 and the resin tank 17 through the hose.

[0079] The ultrasonic probe 8 is set to a startup frequency of 45KHz.

[0080] The servo motor of the prepreg printing device is activated, driving the printing outlet 13 to move in a predetermined direction at a speed of 9 cm / min. This causes the continuous fiber 2 to move in the prepreg mixing chamber 7 at a speed of 9 cm / min, and subsequently, the continuous fiber / resin-based prepreg tow is printed on the printing platform 18 at a speed of 9 cm / min. The driving pressure heat guide roller 15 provides a pressure of 26 N. When the continuous fiber / resin-based prepreg tow reaches the other end of the release paper, the prepreg printing device automatically rotates 180 degrees under the action of the servo motor to continue printing. This printing step is repeated to obtain CNTs-reinforced continuous PBO fiber / epoxy resin-based prepreg.

[0081] The servo motor of the jetting device is restarted to control the resin tank 17 and the nozzle 14. The CNTs-containing resin liquid 12 is moved at a speed of 17 cm / min along the transverse direction of the CNTs-reinforced continuous PBO fiber / epoxy resin-based prepreg. When the nozzle 14 reaches the other side of the prepreg, the jetting printing device automatically turns 180 degrees under the action of the servo motor to continue printing. This printing step is repeated to obtain a transversely oriented CNTs19-reinforced continuous PBO fiber / epoxy resin-based prepreg.

[0082] The continuous PBO fiber / epoxy resin matrix composite material of this embodiment was subjected to transverse tensile testing according to GB / T 3354-2014, and the transverse tensile strength was measured to be 86 MPa, which is 115% higher than that of the continuous PBO fiber / epoxy resin matrix composite material without transverse orientation CNTs reinforcement.

[0083] Example 5

[0084] The difference between this embodiment and embodiment one is that the continuous fiber reinforced composite material in this embodiment is a continuous high molecular weight polyethylene fiber / epoxy resin-based composite material, and an infrared heating lamp is set above the prepreg laying device to pre-cure the CNTs-containing resin adhesive 12 sprayed by the spraying device.

[0085] When preparing the continuous high molecular weight polyethylene fiber / epoxy resin-based composite material of this embodiment using a 3D printing device:

[0086] Using heating rod 10, the temperature of the prepreg mixing chamber 7 and the resin tank 17 is heated to 100°C. The instant heating device of the printing outlet 13 is activated, raising the internal temperature of the CNTs-containing resin liquid to 120°C. The instant heating device of the pressure heat guide roller 15 is activated, raising its temperature to 122°C.

[0087] Weigh 3g of CNTs and 997g of epoxy resin curing system composition, stir them initially with a glass rod, and then add them to two three-roll mills 11. Start the three-roll mills 11, and after grinding and dispersing 8 times, turn on the switch, and the CNTs-containing resin liquid 12 enters the pre-impregnation mixing chamber 7 and the resin tank 17 through the hose.

[0088] The ultrasonic probe 8 has a startup frequency set to 25KHz.

[0089] The servo motor of the prepreg printing device is activated, driving the printing outlet 13 to move in a predetermined direction at a speed of 13 cm / min. This causes the continuous fiber 2 to move in the prepreg mixing chamber 7 at a speed of 13 cm / min, and subsequently, the continuous fiber / resin-based prepreg tow is printed on the printing platform 18 at a speed of 13 cm / min. The driving pressure heat guide roller 15 provides a pressure of 20 N. When the continuous fiber / resin-based prepreg tow reaches the other end of the release paper, the prepreg printing device automatically rotates 180 degrees under the action of the servo motor to continue printing. This printing step is repeated to obtain CNTs-reinforced continuous high molecular weight polyethylene fiber / epoxy resin-based prepreg.

[0090] The servo motor of the jetting device is restarted to control the resin tank 17 and the nozzle 14. The CNTs-reinforced continuous high molecular weight polyethylene fiber / epoxy resin-based prepreg is moved at a speed of 15 cm / min to print the CNTs-containing resin liquid 12. When the nozzle 14 reaches the other side of the prepreg, the jetting printing device automatically turns 180 degrees under the action of the servo motor to continue printing. This printing step is repeated until the CNTs are spread across the entire surface of the prepreg in a lateral orientation.

[0091] The infrared heating lamps above the prepreg laying device are activated, and the CNTs-containing resin liquid 12 is sprayed by the heating spraying device until it reaches a gel state, thus obtaining a transversely oriented CNTs19 reinforced continuous high molecular weight polyethylene fiber / epoxy resin-based prepreg.

[0092] The continuous high molecular weight polyethylene fiber / epoxy resin matrix composite material of this embodiment was subjected to transverse tensile testing according to GB / T 3354-2014, and the transverse tensile strength was measured to be 92 MPa, which is 130% higher than that of the continuous high molecular weight polyethylene fiber / epoxy resin matrix composite material without transverse orientation CNTs reinforcement.

Claims

1. A method for preparing a continuous fiber / resin-based composite material with improved transverse strength, characterized in that, The steps are as follows: 1) Assemble the 3D printing device The 3D printing device includes a fiber placement device, a CNTs dispersion device, a heating device, a prepreg printing device, a jetting device, and a prepreg placement device; the fiber placement device is used to spread the continuous fiber (2) into the prepreg printing device; The CNTs dispersion device is used to uniformly disperse CNTs in the resin curing system; the prepreg printing device includes a prepreg mixing chamber (7) and a driving device, used to fully impregnate the continuous fiber (2) with the CNTs-containing resin liquid (12), and under the action of the driving device, print the fully impregnated continuous fiber (2) on the prepreg placement device; the spraying device includes a resin tank (17) and a driving device, under the action of the driving device, the resin tank (17) moves along a predetermined direction and speed and sprays the CNTs-containing resin liquid (12); the heating device is used to heat the CNTs-containing resin liquid (12) in the prepreg mixing chamber (7) and the resin tank (17); the prepreg placement device is used to place the printed continuous fiber / resin-based prepreg; the cooling device is used to cool the continuous fiber / resin-based prepreg printed above the prepreg placement device; 2) Preparations before printing The release paper is fixed onto the prepreg laying device; the continuous fiber (2) is placed onto the fiber laying device; CNTs and resin curing system are weighed, wherein the mass content of CNTs is 0.3% to 0.75%; the CNTs dispersion device is started to disperse and mix the CNTs and resin curing system to prepare a CNTs-containing resin solution (12); the CNTs-containing resin solution (12) is added to the prepreg mixing chamber (7) and the resin tank (17); the heating device is started to heat the prepreg mixing chamber (7) and the resin tank (17) to 20 to 30°C below the gel temperature of the resin curing system; 3) Utilizing 3D printing equipment to prepare continuous fiber / resin-based prepregs Start the drive unit of the prepreg printing device, drive the printing outlet (13) to move in a predetermined direction, drive the continuous fiber (2) to move on the traction guide roller (9) in the prepreg mixing chamber (7), and fully wet with the CNTs-containing resin liquid (12). Finally, the continuous fiber / resin-based prepreg bundle is printed on the release paper to obtain CNTs-reinforced continuous fiber / resin-based prepreg. Then start the drive unit of the jetting device, control the resin tank (17) and nozzle (14), and print the CNTs-containing resin liquid (12) along the fiber transverse direction on the obtained CNTs-reinforced continuous fiber / resin-based prepreg. After printing to the required size, the transversely oriented CNTs (19)-reinforced continuous fiber / resin-based prepreg is obtained. 4) Continuous fiber / resin-based prepreg prepared by cooling The prepared transversely oriented CNTs (19) reinforced continuous fiber / resin-based prepreg was cooled to room temperature; 5) Preparation of continuous fiber / resin-based composite materials Continuous fiber / resin-based composite materials are prepared by using a compression molding process to prepare continuous fiber / resin-based prepreg cooled to room temperature.

2. The method for preparing a continuous fiber / resin-based composite material with improved transverse strength according to claim 1, characterized in that: The 3D printing device also includes a cooling device; in step 4), the cooling device is used to cool the prepared transversely oriented CNTs (19) reinforced continuous fiber / resin-based prepreg to room temperature.

3. The method for preparing a continuous fiber / resin-based composite material with improved transverse strength according to claim 1, characterized in that: The prepreg printing device also includes an instant heating device and a pressure application device. The prepreg mixing chamber (7) includes a printing outlet (13). There are two instant heating devices, one located at the printing outlet (13) and the other located at the pressure application device. In step 2), the instant heating device is used to heat the temperature at the printing outlet (13) to the gel temperature of the resin curing system. In step 3), the servo motor of the prepreg printing device drives the pressure application device to apply a pressure of 20-30N to the continuous fiber / resin-based prepreg bundle printed on the release paper and heat it to 2-5°C above the gel temperature of the resin curing system.

4. The method for preparing a continuous fiber / resin-based composite material with improved transverse strength according to claim 1, characterized in that: The CNTs dispersion device includes an ultrasonic probe (8) disposed on the wall of the pre-impregnation mixing chamber (7) and the resin tank (17), with an ultrasonic frequency of 25-45 KHz.

5. The method for preparing a continuous fiber / resin-based composite material with improved transverse strength according to claim 1, characterized in that: In step 3), the moving speed of the printing outlet (13) is 5-15 cm / min, and the moving speed of the nozzle (14) is 10-20 cm / min.

6. The method for preparing a continuous fiber / resin-based composite material with improved transverse strength according to claim 1, characterized in that: The 3D printing device also includes a film laying device (21); after the continuous fiber / resin-based prepreg prepared in step 4) is cooled to room temperature, a film is laid on its surface using the film laying device (21) for cold storage.

7. A method for preparing a continuous fiber / resin-based composite material with improved transverse strength according to claim 1 or 5, characterized in that: The prepreg laying device includes an infrared automatic sensor tension control device (16) for fixing the continuous fiber / resin-based prepreg or the film laid on top of it during the printing process.

Images