Pre-cured fiber-reinforced thermosetting composite 3D printing apparatus and method

Abstract

A 3D printing device and method for pre-cured fiber-reinforced thermosetting composite materials includes a tension module, an elliptical mirror-converging UV pre-curing system, and a 3D printing head. The elliptical mirror-converging UV pre-curing system includes a UV light module and a motor drive module. The 3D printing head includes a printing cavity and a high-temperature printing nozzle connected below it. The fiber prepreg bundle is first controlled by the tension module, and then pre-cured by the UV light module. The pre-cured fiber prepreg bundle is then fed into the 3D printing head through the motor drive module. The fiber prepreg bundle undergoes a dark reaction in the cationic photocuring system after being radiated and heated by the printing cavity, completing the deep curing of the resin inside the fiber prepreg bundle that cannot be irradiated by UV light. Finally, it is further heated by the high-temperature printing nozzle and 3D printed onto the printing plane, completing the 3D printing shaping. This invention enables the 3D printing of non-transparent fiber-reinforced composite materials.

Description

Technical Field

[0001] This invention relates to the field of 3D printing of carbon fiber reinforced thermosetting composite materials, and specifically to a 3D printing apparatus and method for pre-cured fiber reinforced thermosetting composite materials. Background Technology

[0002] 3D printing technology using fiber-reinforced resin matrix composites combines the material performance advantages of composite materials with the process characteristics of 3D printing. It holds promise for breaking the limitations of traditional manufacturing methods such as winding, lay-up, and stacking on composite material structural design, enabling low-cost and rapid prototyping of complex curved surface composite components. Thermosetting polymer molecules form a robust three-dimensional network structure through chemical bonding, exhibiting higher strength, hardness, and lower strain under load. Currently, thermosetting composite 3D printing technology mainly relies on in-situ pre-curing to achieve immediate shaping of extruded materials. The in-situ pre-curing methods include laser pre-curing, electron beam pre-curing, and ultraviolet light pre-curing. Among these, in-situ ultraviolet light pre-curing is characterized by fast shaping, low cost, and high efficiency, making it the mainstream technology in thermosetting composite 3D printing.

[0003] According to the literature (Md Atikur Rahman. (2021). 3D printing of continuous carbon fiber reinforced thermoset composites using UV curable resin. PolymerComposites. 42 / 11: 5859-5868), using chopped carbon fiber to reinforce the matrix material suppresses the opacity of the carbon fiber, further increases the fiber volume fraction, and compared with carbon fiber, glass fiber is more transparent, which helps to better transmit ultraviolet rays. It can be seen that the main limitation of current UV-cured thermosetting composite material 3D printing technology lies in the problem of UV light penetration. It is often limited to fiber reinforcements with good light transmittance, such as glass fiber and quartz fiber. However, for fiber reinforcements with poor light transmittance, such as carbon fiber, basalt fiber, and graphite fiber, if the pre-impregnated filament is only simultaneously irradiated with UV light during the 3D printing process, although the resin on the surface of the fiber filament can undergo a photocuring reaction, the resin on the back of the pre-impregnated filament that is in contact with the printing platform, as well as the resin impregnated inside the filament, cannot be irradiated with UV light. Therefore, the photocuring reaction cannot be initiated, which means that the degree of curing of the extruded printed filament cannot be further improved in the subsequent thermocuring reaction, resulting in a low degree of curing of the overall structure, which seriously affects the final performance of the 3D printed composite material. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a 3D printing device and method for pre-curing fiber-reinforced thermosetting composite materials. Based on the curing characteristics of cationic thermosetting resin with deep penetration and slow reaction, the device pre-cures the material to achieve 3D printing of non-transparent fiber-reinforced composite materials such as carbon fiber, graphite fiber, and basalt fiber.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A 3D printing device for pre-cured fiber-reinforced thermosetting composite materials includes a tension module 2, an elliptical mirror-converging UV pre-curing system, and a 3D printing head. The elliptical mirror-converging UV pre-curing system includes an ultraviolet light module 3 and a motor drive module 4. The fiber prepreg bundle 1 is first controlled by the tension module 2 to control its transmission tension, and then pre-cured by the ultraviolet light module 3. The pre-cured fiber prepreg bundle 1 is then fed into the 3D printing head through the motor drive module 4 to complete the printing and shaping.

[0007] The tension module 2 includes a tensioning wheel 201, a tensioning wheel mounting bracket 202, and a tension module bottom cover 203. The tensioning wheel 201 is mounted on the tensioning wheel mounting bracket 202 via a tensioning wheel shaft. The tensioning wheel mounting bracket 202 is installed inside the tension module bottom cover 203. The tension module 2 straightens and maintains tension on the pre-impregnated yarn bundle.

[0008] The ultraviolet light module 3 includes an ultraviolet light module housing 301, a reflector body 302, and an ultraviolet light tube 303. The reflector body 302 is installed inside the ultraviolet light module housing 301. The interior of the reflector body 302 is hollow and the inner surface is a mirror. The cross-section is elliptical. The ultraviolet light tube 303 is installed inside the reflector body 302 and its axis coincides with one focus of the elliptical cross-section. The fiber prepreg bundle 1 conveying line coincides with the other focus of the elliptical cross-section.

[0009] The motor drive module 4 includes a servo motor 401, which is connected to a motor mounting bracket 402. The motor mounting bracket 402 is connected to a motor cover 408, and the motor cover 408 is connected to a motor connecting wheel mounting plate 407. A motor connecting wheel 406 is connected to the motor output shaft 403 of the servo motor 401. The motor connecting wheel 406 and the tension wheel 404 cooperate with each other. The motor connecting wheel 406 and the tension wheel 404 are mounted on the motor connecting wheel mounting plate 407, which is installed inside the bottom cover 405 of the motor drive module.

[0010] The 3D printing head includes a printing cavity 5 and a high-temperature printing nozzle 6 connected below it. The fiber prepreg bundle 1 is first heated by radiation in the printing cavity 5 to carry out the dark reaction in the cationic photocuring system, which completes the deep curing of the resin inside the fiber prepreg bundle 1 that cannot be irradiated by ultraviolet light. Finally, it is further heated by the high-temperature printing nozzle 6 to 3D print and form on the printing plane, thus completing the 3D printing shaping.

[0011] The fibers in the fiber prepreg tow 1 are transparent or opaque fibers; opaque fibers include carbon fiber, basalt fiber, graphite fiber, and aramid fiber; the fibers are continuous fibers or chopped fibers.

[0012] The fiber prepreg tow 1 is a revitalized material obtained by passing the fiber through a cationic thermosetting resin melt pool. The cationic thermosetting resin includes: oligomers, reactive diluents, photoinitiators, and additives; wherein the oligomers include epoxy resins and vinyl ether resins; the reactive diluents include epoxy resin diluents, cyclic ethers, intracyclic esters, and vinyl ether monomers, etc.; the photoinitiators include diaryliodomonium salts, triarylthiomonium salts, and ferrocene salt initiators; the additives include stabilizers (to reduce polymerization during storage and improve the storage stability of the resin), defoamers (to prevent and eliminate bubbles generated during the manufacturing and use of the coating), and photosensitizers (to improve the initiation efficiency of the photoinitiator), etc.

[0013] A printing method using a pre-cured fiber-reinforced thermosetting composite material 3D printing device involves the following steps: The fiber prepreg bundle 1 is drawn in by the motor drive module 4 and the portion already shaped to the printing plane. First, it is straightened by the tension module 2, ensuring that the fiber prepreg bundle 1 accurately enters the ultraviolet light module 3 and that its transport path coincides with the focal point of the ellipse of the reflector 302. Ultraviolet light emitted from the ultraviolet lamp tube at the other focal point of the ellipse of the reflector 302 is reflected by the elliptical mirror and irradiates the fiber prepreg bundle 1 from different directions, pre-curing it. After leaving the ultraviolet light module 3, the fiber prepreg bundle 1 is transported to the 3D printing head. Heated by the printing chamber 5, it enters the dark reaction stage of cationic photocuring, curing the resin inside the fiber prepreg bundle. Finally, it is shaped to the printing plane by the high-temperature printing nozzle 6, completing the 3D printing of the thermosetting continuous carbon fiber composite material.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] (1) In the existing 3D printing of photocurable continuous fiber thermosetting composite materials, the ultraviolet light is integrated with the print head, the trajectory of the light is consistent with the printing path, and the light is continuously irradiated within a certain range, which makes it impossible to precisely control the irradiation time. The present invention adopts pre-curing with light, which is beneficial to control the irradiation time and further control the degree of photocuring.

[0016] (2) In the existing 3D printing of photocurable continuous fiber thermosetting composite materials, the ultraviolet light can only irradiate the surface of the fiber bundle, and the side that is in contact with the printing plane cannot receive ultraviolet light irradiation, resulting in uneven curing. Based on the optical characteristics of an ellipse, the present invention irradiates the surface of the fiber prepreg fiber bundle in advance to ensure that the fiber prepreg fiber bundle is uniformly photocured. Then, by utilizing the characteristics of cationic photocuring with deep penetration, slow reaction and dark reaction, 3D printing is achieved.

[0017] (3) Most of the existing photocurable continuous fiber thermosetting composite material 3D printing is free radical photocuring. This invention uses cationic photocuring, which has the curing characteristics of deep penetration and slow reaction. After the fiber prepreg bundle is precured, the dark reaction of cationic photocuring is initiated by heating. That is, the curing reaction is still in progress without the action of UV, so that the fiber prepreg bundle can be deeply cured inside, which solves the problem that UV light cannot penetrate the non-transparent prepreg bundle. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the device of the present invention.

[0019] Figure 2 This is a schematic diagram of the tension module of the present invention.

[0020] Figure 3 This is a schematic diagram of the ultraviolet light module of the present invention.

[0021] Figure 4 This is a schematic diagram illustrating the principle of ultraviolet light elliptical mirror focusing in this invention.

[0022] Figure 5 This is a schematic diagram of the motor drive module of the present invention.

[0023] Figure 6 This is a honeycomb-shaped sample of continuous carbon fiber reinforced bisphenol A type epoxy resin thermosetting composite material in an embodiment of the present invention.

[0024] Figure 7 This is a flat plate sample of a continuous carbon fiber reinforced bisphenol A type epoxy resin thermosetting composite material in an embodiment of the present invention.

[0025] Figure 8 The thermogravimetric analysis results of the continuous carbon fiber reinforced bisphenol A type epoxy resin thermosetting composite material in the embodiments of the present invention are shown in the figure.

[0026] Figure 9 This is a diagram showing the internal fiber distribution of the continuous carbon fiber reinforced bisphenol A type epoxy resin thermosetting composite material in an embodiment of the present invention. Detailed Implementation

[0027] The technical solution of the present invention will now be clearly and completely described with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Reference Figure 1 A 3D printing device for pre-cured fiber-reinforced thermosetting composite materials includes a tension module 2, an elliptical mirror-converging UV pre-curing system, and a 3D printing head. The elliptical mirror-converging UV pre-curing system includes an ultraviolet light module 3 and a motor drive module 4. The 3D printing head includes a printing cavity 5 and a high-temperature printing nozzle 6 connected below it. The fiber prepreg bundle 1 is first controlled by the tension module 2, and then pre-cured by the ultraviolet light module 3. The pre-cured fiber prepreg bundle 1 is fed into the 3D printing head through the motor drive module 4. The fiber prepreg bundle 1 is radiated and heated by the printing cavity 5 to carry out the dark reaction in the cationic photocuring system, completing the deep curing of the resin inside the fiber prepreg bundle 1 that cannot be irradiated by ultraviolet light. Finally, it is further heated by the high-temperature printing nozzle 6 and 3D printed onto the printing plane to complete the 3D printing shaping.

[0029] Reference Figure 2 The tension module 2 includes a tensioning wheel 201, a tensioning wheel mounting bracket 202, and a tension module bottom cover 203. The tensioning wheel 201 is mounted on the tensioning wheel mounting bracket 202 via a tensioning wheel shaft. The tensioning wheel mounting bracket 202 is installed inside the tension module bottom cover 203. The tensioning wheels 201 are installed at a certain angle and distance and can rotate freely via the tensioning wheel shaft. The tension module 2 straightens and maintains tension on the prepreg tow to increase the light-receiving area of ​​the fiber prepreg tow 1 and improve the curing degree of the pre-cured fiber.

[0030] Reference Figure 3 , Figure 4The ultraviolet light module 3 includes an ultraviolet light module housing 301, a reflector body 302, and an ultraviolet lamp tube 303. The reflector body 302 is installed inside the ultraviolet light module housing 301. The reflector body 302 is hollow inside and has a mirror surface on its inner surface. Its cross-section is elliptical. The ultraviolet lamp tube 303 is installed inside the reflector body 302 and its axis coincides with one focus of the elliptical cross-section. The fiber prepreg bundle 1 conveying line coincides with the other focus of the elliptical cross-section. Since the ellipse satisfies the optical properties that light emitted from one focus of the ellipse will pass through the other focus of the ellipse after being reflected by the ellipse, it ensures that the ultraviolet light emitted by the ultraviolet lamp tube 303 is reflected by the reflector body 302 and irradiates the fiber prepreg bundle 1 from all directions, thus pre-curing the surface of the fiber prepreg bundle 1 evenly and fully in advance.

[0031] Reference Figure 5 The motor drive module 4 includes a servo motor 401, a motor mounting bracket 402, a motor output shaft 403, a tension wheel 404, a motor drive module bottom cover 405, a motor connecting wheel 406, a motor connecting wheel mounting plate 407, and a motor cover 408. The servo motor 401 is connected to the motor mounting bracket 402, the motor mounting bracket 402 is connected to the motor cover 408, and the motor cover 408 is connected to the motor connecting wheel mounting plate 407. The motor output shaft 403 of the servo motor 401 is connected to the motor connecting wheel 406, which cooperates with the tension wheel 404. The motor connecting wheel 406 and the tension wheel 404 are mounted on the motor connecting wheel mounting plate 407, which is installed inside the motor drive module bottom cover 405. The fiber prepreg tow 1 is continuously pre-cured by passing through an elliptical mirror under the drive of the servo motor 401, and then conveyed to the 3D printing head.

[0032] A printing method using a pre-cured fiber-reinforced thermosetting composite material 3D printing device involves a fiber prepreg bundle 1 being drawn by a motor drive module 4 and a portion already shaped to the printing plane. First, it is straightened by a tension module 2, increasing the light-receiving area of ​​the fiber prepreg bundle 1 while ensuring it accurately enters the ultraviolet light module 3 and its transport path coincides with the focal point of the ellipse of the reflector 302. Ultraviolet light emitted from an ultraviolet lamp at another focal point of the ellipse of the reflector 302 is reflected by the elliptical mirror and irradiates the fiber prepreg bundle 1 from different directions, thus pre-curing the fiber prepreg bundle 1 uniformly and thoroughly. After leaving the ultraviolet light module 3, the fiber prepreg bundle 1 is transported to the 3D printing head. Heated by the printing chamber 5, it enters the dark reaction stage of cationic system photocuring, solidifying the resin inside the fiber prepreg bundle. Finally, it is shaped to the printing plane by a high-temperature printing nozzle 6, completing the 3D printing of the thermosetting continuous carbon fiber composite material.

[0033] The fiber prepreg tow 1 uses a continuous carbon fiber reinforced bisphenol A type epoxy resin thermosetting composite material. The resin matrix of the thermosetting composite material is a high molecular weight thermosetting epoxy resin F-44 that has not undergone a curing reaction. The cationic photoinitiator in the resin matrix is ​​a diaryliodonium salt photoinitiator; the maximum absorption wavelength of ultraviolet light is 275nm, and the addition amount is 1%-5%. It is 3D printed in a honeycomb shape, such as... Figure 6 As shown, the printed sample has a smooth surface and a good shape.

[0034] The fiber prepreg tow 1 uses a continuous carbon fiber reinforced bisphenol A type epoxy resin thermosetting composite material. The resin matrix of the thermosetting composite material is a high molecular weight thermosetting epoxy resin E-20 that has not undergone a curing reaction. The cationic photoinitiator in the resin matrix is ​​a triarylsulfonium salt photoinitiator; the maximum absorption wavelength of ultraviolet light is 290nm, and the addition amount is 1%-5%. It is 3D printed in a flat plate shape, such as... Figure 7 As shown, the printed sample has a smooth surface and good printing effect. Thermogravimetric analysis (TGA) was performed on the continuous carbon fiber reinforced bisphenol A epoxy resin thermosetting composite material. At 800℃, the epoxy resin and initiator completely decomposed, and the remaining mass was the mass of the continuous carbon fibers, with a fiber content of 54%. The test results are shown in [Figure number missing]. Figure 8 The continuous carbon fiber reinforced bisphenol A type epoxy resin thermosetting composite material, according to GB / T30969—2014 Test Method for Shear Strength of Short Beams of Polymer-Based Composite Materials and GB / T 3356—2014 Test Method for Bending Properties of Directed Fiber Reinforced Polymer-Based Composite Materials, has a flexural strength of 680 MPa and an interlaminar shear strength of 46 MPa. The internal fiber distribution of the continuous carbon fiber reinforced bisphenol A type epoxy resin thermosetting composite material is as follows: Figure 9 As shown, the fibers are evenly distributed within the resin with few voids.

[0035] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Those skilled in the art should understand that modifications can still be made to the technical solutions described in each embodiment, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A 3D printing device for pre-cured fiber-reinforced thermosetting composite materials, comprising a tension module (2), an elliptical mirror-converging UV pre-curing system, and a 3D printing head; characterized in that: The elliptical mirror-converging UV pre-curing system includes an ultraviolet light module (3) and a motor drive module (4); the fiber prepreg bundle (1) is first controlled by the tension module (2), and then pre-cured by the ultraviolet light module (3). The pre-cured fiber prepreg bundle (1) is then fed into the 3D printing head through the motor drive module (4) to complete the printing and shaping. The 3D printing head includes a printing cavity (5) and a high-temperature printing nozzle (6) connected below it. The fiber prepreg bundle (1) is first heated by radiation in the printing cavity (5) to carry out the dark reaction in the cationic photocuring system, and completes the deep curing of the resin inside the fiber prepreg bundle (1) that cannot be irradiated by ultraviolet light. Finally, it is further heated by the high-temperature printing nozzle (6) to 3D print and form on the printing plane, thus completing the 3D printing shaping. The fiber prepreg tow (1) is a revitalized material obtained by passing the fiber through a cationic thermosetting resin melt pool. The cationic thermosetting resin includes: oligomers, reactive diluents, photoinitiators, and additives; wherein the oligomers include epoxy resin and vinyl ether resin; the reactive diluents include epoxy resin diluents, cyclic ethers, intracyclic esters, and vinyl ether monomers; the photoinitiators include diaryliodonium salts, triarylthionium salts, and ferrocene salt initiators; and the additives include stabilizers, defoamers, and photosensitizers.

2. The apparatus according to claim 1, characterized in that: The tension module (2) includes a tensioning wheel (201), a tensioning wheel mounting bracket (202), and a tension module bottom cover (203). The tensioning wheel (201) is mounted on the tensioning wheel mounting bracket (202), and the tensioning wheel mounting bracket (202) is installed inside the tension module bottom cover (203). The tension module (2) straightens and maintains tension on the prepreg bundle.

3. The apparatus according to claim 1, characterized in that: The ultraviolet light module (3) includes an ultraviolet light module shell (301), a reflector body (302), and an ultraviolet light tube (303). The reflector body (302) is installed inside the ultraviolet light module shell (301). The reflector body (302) is hollow inside and has a mirror surface on its inner surface. Its cross-section is elliptical. The ultraviolet light tube (303) is installed inside the reflector body (302) and its axis coincides with one focus of the elliptical cross-section. The fiber prepreg bundle (1) conveying line coincides with the other focus of the elliptical cross-section.

4. The apparatus according to claim 1, characterized in that: The motor drive module (4) includes a servo motor (401), which is connected to a motor mounting bracket (402). The motor mounting bracket (402) is connected to a motor cover (408), and the motor cover (408) is connected to a motor connecting wheel mounting plate (407). A motor connecting wheel (406) is connected to the motor output shaft (403) of the servo motor (401). The motor connecting wheel (406) and the tension wheel (404) cooperate with each other. The motor connecting wheel (406) and the tension wheel (404) are mounted on the motor connecting wheel mounting plate (407), which is installed inside the bottom cover (405) of the motor drive module.

5. The apparatus according to claim 1, characterized in that: The fibers in the fiber prepreg tow (1) are transparent or opaque fibers; opaque fibers include carbon fiber, basalt fiber, graphite fiber, and aramid fiber. The fibers used are either continuous or chopped fibers.

6. A printing method using the apparatus according to any one of claims 1-5, characterized in that: The fiber prepreg bundle (1) is drawn in by the motor drive module (4) and the part that has been shaped to the printing plane. First, it is straightened by the tension module (2) to ensure that the fiber prepreg bundle (1) accurately enters the ultraviolet light module (3) and its transport path coincides with the focal point of the ellipse of the reflector body (302). The ultraviolet light emitted by the ultraviolet lamp tube at the other focal point of the ellipse of the reflector body (302) is reflected by the ellipse and irradiates the fiber prepreg bundle (1) from different directions, thus pre-curing the fiber prepreg bundle (1) in advance. After the fiber prepreg bundle (1) leaves the ultraviolet light module (3), it is transported to the 3D printing head. After being heated by the printing chamber (5), it enters the dark reaction stage of cationic system photocuring, so that the resin inside the fiber prepreg bundle is cured. Finally, it is shaped to the printing plane by the high temperature printing nozzle (6) to complete the 3D printing of thermocurable continuous carbon fiber composite material.

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