Carbon fiber reinforced thermoplastic tow preparation device and method for additive manufacturing

Abstract

According to the carbon fiber reinforced thermoplastic tow preparation device and method for additive manufacturing, in the device, a carbon fiber tow spreading module is used for removing a sizing agent on the surface of a carbon fiber tow and spreading the carbon fiber tow; the hot processing module is used for enabling thermoplastic resin and the unfolded carbon fiber tows to form a sandwich structure, and mixing and extruding to obtain a tow-shaped composite material; and the forming module is used for cooling and shaping the tow-shaped composite material to obtain the carbon fiber reinforced thermoplastic tow. The device unfolds the carbon fiber tows in advance, and then the carbon fiber tows are mixed with thermoplastic resin to prepare the fiber-reinforced thermoplastic tows.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon fiber, and in particular to a device and method for preparing carbon fiber reinforced thermoplastic filament bundles for additive manufacturing. Background Art

[0002] Carbon fiber reinforced thermoplastic composites have broad application prospects in aerospace, automotive industry, and high-performance sports equipment due to their light weight and high strength. However, traditional carbon fiber reinforced composite preparation methods often have problems such as complex processes, high costs, and inability to manufacture complex structures, which limits their application in customized production. The use of additive manufacturing technology to manufacture carbon fiber reinforced thermoplastic composites can get rid of the limitations of traditional molds and has unique technical advantages.

[0003] At present, when preparing carbon fiber reinforced thermoplastic printing tows, due to the high viscosity of thermoplastic resins, the carbon fiber tows are directly blended and extruded with thermoplastic resins, and the molten resin cannot enter the interior of the fibers, resulting in a large number of pores in the fibers, which seriously affects the mechanical properties of the printed structural parts. In addition, many existing commercial continuous fiber printing tows use thermosetting resins to impregnate carbon fiber tows, and then blend them with thermoplastic resins to prepare printing tows, but when the tows are subjected to force, the interface between the thermosetting resin and the thermoplastic resin is prone to peeling, and the mechanical properties are still limited.

[0004] The information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0005] In view of the shortcomings or defects of the above-mentioned prior art, a device and method for preparing carbon fiber reinforced thermoplastic bundles for additive manufacturing are provided, which can effectively reduce the porosity inside the carbon fiber bundles, achieve uniform mixing of carbon fiber and thermoplastic resin and reduce porosity, which is of great significance for promoting the application of carbon fiber reinforced thermoplastic composites in the field of additive manufacturing.

[0006] The purpose of the present invention is achieved through the following technical solutions.

[0007] A device for preparing carbon fiber reinforced thermoplastic tow for additive manufacturing comprises: A carbon fiber spreading module, which is used to remove the sizing agent on the surface of the carbon fiber tow and to spread the carbon fiber tow; A thermal processing module, which is used to form a sandwich structure with a thermoplastic resin and the unfolded carbon fiber tow, and mix and extrude them to obtain a tow-shaped composite material; The forming module is used for cooling and shaping the tow-shaped composite material to obtain carbon fiber reinforced thermoplastic tow.

[0008] In the carbon fiber reinforced thermoplastic tow preparation device for additive manufacturing, along the carbon fiber tow supply direction, the carbon fiber spreading module is sequentially connected to the thermal processing module and the molding module.

[0009] In the device for preparing carbon fiber reinforced thermoplastic tow for additive manufacturing, the carbon fiber spreading module comprises: A carbon fiber tow unwinding unit and a rewinding unit, which are arranged at intervals for continuously supplying and rewinding the carbon fiber tow; A heating unit for removing a sizing agent from the surface of the carbon fiber tow; A pressure wheel unit for providing tension to the carbon fiber tow; A blowing unit, which is used to blow the carbon fiber tow; A tension sensor, which is used to detect the tension of the carbon fiber tow in real time; The fiber spreading unit is used to spread the carbon fiber tow.

[0010] In the device for preparing carbon fiber reinforced thermoplastic tow for additive manufacturing, the pressure wheel unit includes a mounting plate perpendicular to the moving direction of the carbon fiber tow and a top plate perpendicular to the mounting plate and mounted on the top of the mounting plate. A linear rail is fixedly provided on the surface of the mounting plate, and a sliding slider is provided on the linear rail. A PU wheel hanging plate is fixedly connected to the slider. The slider is flush with the top of the PU wheel hanging plate. A PU wheel upper shaft is fixedly provided below the PU wheel hanging plate. The end of the PU wheel upper shaft supports a freely rotatable first PU wheel. A PU wheel lower shaft is provided at a position of the mounting plate below the PU wheel hanging plate. The end of the PU wheel lower shaft supports a freely rotatable second PU wheel. The first PU wheel and the second PU wheel are arranged oppositely, and the carbon fiber tow passes between the first PU wheel and the second PU wheel. A clamping screw for controlling the height of the PU wheel hanging plate is provided on the top plate, and the clamping screw passes through the top plate and extends downward. The PU wheel hanging plate is located at the lower end of the clamping screw. The extension length of the clamping screw is adjusted by rotating the clamping screw to control the height of the lower PU wheel hanging plate.

[0011] In the device for preparing carbon fiber reinforced thermoplastic filament bundles for additive manufacturing, the filament spreading unit spreads the distance between the carbon fiber filament bundles to 3-10 mm.

[0012] In the device for preparing carbon fiber reinforced thermoplastic filament bundles for additive manufacturing, the filament spreading unit is a cubic structure, which includes a bottom plate, a top plate, and a first air outlet plate, a second air outlet plate, a fiber inlet plate, and a fiber outlet plate located between the bottom plate and the top plate. The first air outlet plate and the second air outlet plate are arranged relative to each other and parallel to the carbon fiber filament bundles, the fiber inlet plate and the fiber outlet plate are arranged relative to each other and perpendicular to the carbon fiber filament bundles, the holes on the fiber inlet plate and the holes on the fiber outlet plate are of the same size and are relatively positioned. When working, the carbon fiber filament bundles are arranged along the fiber inlet plate The wind enters through the holes on the fiber outlet plate and exits along the holes on the fiber outlet plate. Ventilation holes are provided on both the first outlet plate and the second outlet plate. Negative pressure exhaust units are connected to the fiber inlet plate and the fiber outlet plate on both sides respectively. The negative pressure exhaust unit on one side of the fiber inlet plate enables the wind to flow in along the direction of the holes on the fiber inlet plate and along the moving direction of the carbon fiber bundle, and then flow out along the direction of the holes on the air volume adjusting plates on both sides. The negative pressure exhaust unit on one side of the fiber outlet plate enables the wind to flow in along the direction of the holes on the fiber outlet plate and against the moving direction of the carbon fiber bundle, and then flow out along the direction of the holes on the air volume adjusting plates on both sides.

[0013] In the device for preparing carbon fiber reinforced thermoplastic tow for additive manufacturing, the thermal processing module comprises: A hot roll unit for forming a sandwich structure with thermoplastic resin and unrolled carbon fiber tows, A screw extruder is used to melt thermoplastic resin particles and extrude them into a molding die; The molding die is used for co-extruding the thermoplastic resin and the unfolded carbon fiber tow to obtain a tow-shaped composite material.

[0014] In the device for preparing carbon fiber reinforced thermoplastic tows for additive manufacturing, the diameter of the carbon fiber tows in the tow-shaped composite material is 0.4-0.8 mm.

[0015] In the device for preparing carbon fiber reinforced thermoplastic filament bundles for additive manufacturing, the molding module includes an air cooling unit, which is used to cool the temperature of the filament bundle-shaped composite material to below 40° C. to obtain a fiber reinforced thermoplastic filament bundle.

[0016] A method for preparing a carbon fiber reinforced thermoplastic tow preparation device for additive manufacturing comprises: Step 1, removing the sizing agent on the surface of the carbon fiber tow, and unfolding the carbon fiber tow, wherein the temperature for removing the sizing agent on the surface of the carbon fiber tow is 300-500° C.; Step 2, forming a sandwich structure with the thermoplastic resin and the unfolded carbon fiber tow, and mixing and extruding them to obtain a tow-shaped composite material; Step 3, cooling and shaping the tow-shaped composite material to obtain carbon fiber reinforced thermoplastic tow.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a stable carbon fiber reinforced thermoplastic tow preparation device and method for additive manufacturing. By unfolding the carbon fiber tow, it is ensured that the thermoplastic resin can penetrate more deeply into the carbon fiber tows, overcoming the problem of uneven penetration caused by excessive resin viscosity in the traditional process. The continuous supply of thermoplastic resin and the efficient heating and pressing process improve the production efficiency, so that the thermoplastic resin is evenly wrapped on the carbon fiber tow and fills the gaps between the fibers, thereby achieving the improvement of mechanical properties with a relatively simple process.

[0018] The above description is only an overview of the technical solution of the present invention. In order to make the technical means of the present invention clearer and to achieve the extent that those skilled in the art can implement it according to the contents of the specification, and in order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are exemplified below. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] By reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The drawings in the specification are only for the purpose of illustrating the preferred embodiments and are not considered to be limitations of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative work. Moreover, the same reference numerals are used to represent the same components throughout the drawings.

[0020] In the attached picture: Figure 1 A schematic structural diagram of a device for preparing a carbon fiber reinforced thermoplastic tow for additive manufacturing according to a preferred embodiment of the present invention is shown; Figure 2 A schematic diagram showing the structure of a pressure wheel unit in a preferred embodiment of the present invention; Figure 3 A schematic diagram showing the structure of a wire spreading unit according to a preferred embodiment of the present invention is shown; Figure 4 A schematic diagram showing the change in distance between carbon fiber bundles before and after fiber spreading; Figure 5 (a) shows a schematic diagram of the state of the carbon fiber tow and the thermoplastic resin before hot pressing; Figure 5 (b) shows a schematic diagram of a thermoplastic resin film containing carbon fiber tows; Figure 6 A schematic diagram showing a thermoplastic resin formed into a tow shape.

[0021] The present invention is further explained below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0022] The specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0023] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the attached claims.

[0024] To facilitate understanding of the embodiments of the present invention, several specific embodiments will be further explained below with reference to the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present invention.

[0025] For a better understanding, Figures 1 to 6 As shown, a device for preparing carbon fiber reinforced thermoplastic filament bundles for additive manufacturing includes: A carbon fiber spreading module, which is used to remove the sizing agent on the surface of the carbon fiber tow and to spread the carbon fiber tow; A thermal processing module, which is used to form a sandwich structure with a thermoplastic resin and the unfolded carbon fiber tow, and mix and extrude them to obtain a tow-shaped composite material; The forming module is used for cooling and shaping the tow-shaped composite material to obtain carbon fiber reinforced thermoplastic tow.

[0026] In a preferred embodiment of a carbon fiber reinforced thermoplastic tow preparation device for additive manufacturing, along the carbon fiber tow supply direction, the carbon fiber spreading module is sequentially connected to the thermal processing module and the molding module.

[0027] In a preferred embodiment of a carbon fiber reinforced thermoplastic tow preparation device for additive manufacturing, the carbon fiber spreading module comprises: A carbon fiber tow unwinding unit and a rewinding unit, which are arranged at intervals for continuously supplying and rewinding the carbon fiber tow; A heating unit for removing a sizing agent from the surface of the carbon fiber tow; A pressure wheel unit for providing tension to the carbon fiber tow; A blowing unit, which is used to blow the carbon fiber tow; A tension sensor, which is used to detect the tension of the carbon fiber tow in real time; The fiber spreading unit is used to spread the carbon fiber tow.

[0028] In a preferred embodiment of a carbon fiber reinforced thermoplastic tow preparation device for additive manufacturing, the pressure wheel unit includes a mounting plate perpendicular to the moving direction of the carbon fiber tow and a top plate perpendicular to the mounting plate and mounted on the top of the mounting plate, a linear rail is fixedly provided on the surface of the mounting plate, a sliding block connected in a sliding manner is provided on the linear rail, a PU wheel hanging plate is fixedly connected to the slider, the slider is flush with the top of the PU wheel hanging plate, a PU wheel upper shaft is fixedly provided below the PU wheel hanging plate, the end of the PU wheel upper shaft supports a freely rotatable first PU wheel, a PU wheel lower shaft is provided at a position of the mounting plate below the PU wheel hanging plate, the end of the PU wheel lower shaft supports a freely rotatable second PU wheel, the first PU wheel and the second PU wheel are arranged oppositely, the carbon fiber tow passes between the first PU wheel and the second PU wheel, a clamping screw for controlling the height of the PU wheel hanging plate is provided on the top plate, the clamping screw passes through the top plate and extends downward, the PU wheel hanging plate is located at the lower end of the clamping screw, and the extension length of the clamping screw is adjusted by rotating the clamping screw to control the height of the lower PU wheel hanging plate.

[0029] In a preferred embodiment of a device for preparing carbon fiber reinforced thermoplastic tows for additive manufacturing, the fiber spreading unit spreads the distance between the carbon fiber tows to 3-10 mm.

[0030] In a preferred embodiment of a carbon fiber reinforced thermoplastic filament preparation device for additive manufacturing, the filament spreading unit is a cubic structure, which includes a bottom plate, a top plate, and a first air outlet plate, a second air outlet plate, a fiber inlet plate, and a fiber outlet plate located between the bottom plate and the top plate. The first air outlet plate and the second air outlet plate are arranged relative to each other and parallel to the carbon fiber filament bundle, the fiber inlet plate and the fiber outlet plate are arranged relative to each other and perpendicular to the carbon fiber filament bundle, the holes on the fiber inlet plate and the holes on the fiber outlet plate are of the same size and are relatively positioned. When working, the carbon fiber filament bundle is stretched along the fiber inlet plate. The wind enters through the holes on the fiber outlet plate and exits along the holes on the fiber outlet plate. Ventilation holes are provided on both the first outlet plate and the second outlet plate. Negative pressure exhaust units are respectively connected on both sides of the fiber inlet plate and the fiber outlet plate. The negative pressure exhaust unit on one side of the fiber inlet plate enables the wind to flow in along the direction of the holes on the fiber inlet plate and along the moving direction of the carbon fiber bundle, and then flows out along the direction of the holes on the air volume adjusting plates on both sides. The negative pressure exhaust unit on one side of the fiber outlet plate enables the wind to flow in along the direction of the holes on the fiber outlet plate and against the moving direction of the carbon fiber bundle, and then flows out along the direction of the holes on the air volume adjusting plates on both sides.

[0031] In a preferred embodiment of a device for preparing carbon fiber reinforced thermoplastic tow for additive manufacturing, the thermal processing module comprises: A hot roll unit for forming a sandwich structure with thermoplastic resin and unrolled carbon fiber tows, A screw extruder is used to melt thermoplastic resin particles and extrude them into a molding die; The molding die is used for co-extruding the thermoplastic resin and the unfolded carbon fiber tow to obtain a tow-shaped composite material.

[0032] In a preferred embodiment of a device for preparing a carbon fiber reinforced thermoplastic tow for additive manufacturing, the diameter of the carbon fiber tow in the tow-shaped composite material is 0.4-0.8 mm.

[0033] In a preferred embodiment of a device for preparing a carbon fiber reinforced thermoplastic filament bundle for additive manufacturing, the molding module includes an air cooling unit, which is used to cool the temperature of the filament bundle-shaped composite material to below 40° C. to obtain a fiber reinforced thermoplastic filament bundle.

[0034] In one embodiment, a method for preparing a carbon fiber reinforced thermoplastic tow preparation device for additive manufacturing includes: Step 1, removing the sizing agent on the surface of the carbon fiber tow, and unfolding the carbon fiber tow, wherein the temperature for removing the sizing agent on the surface of the carbon fiber tow is 300-500° C.; Step 2, forming a sandwich structure with the thermoplastic resin and the unfolded carbon fiber tow, and mixing and extruding them to obtain a tow-shaped composite material; Step 3, cooling and shaping the tow-shaped composite material to obtain carbon fiber reinforced thermoplastic tow.

[0035] In one embodiment, a carbon fiber reinforced thermoplastic tow preparation apparatus for additive manufacturing includes: A carbon fiber spreading module, which is used to remove the sizing agent on the surface of the carbon fiber tow 2 and spread the carbon fiber tow 2; A thermal processing module, which is used to form a sandwich structure with a thermoplastic resin and the unfolded carbon fiber tow 2, and mix and extrude them to obtain a tow-shaped composite material; The forming module is used for cooling and shaping the filament bundle-shaped composite material to obtain the fiber-reinforced thermoplastic filament bundle.

[0036] Along the supply direction of the carbon fiber tow 2, the carbon fiber spreading module is connected to the thermal processing module and the molding module in sequence. The carbon fiber tow 2 is evenly spread through the carbon fiber spreading module, which reduces the entanglement and clogging of the carbon fiber tow 2 on the one hand and improves the production efficiency; on the other hand, the carbon fiber tow 2 is spread, which increases the contact area between it and the thermoplastic resin, so that the thermoplastic resin in the molten state can more fully penetrate between the carbon fiber tow 2, thereby effectively reducing the porosity inside the final product tow, which not only improves the printing density, but also enhances the mechanical properties; on the other hand, the contact between the carbon fiber tow 2 and the thermoplastic resin after the spread is more uniform and tight, which helps to form a stronger interface bonding, which can prevent peeling when subjected to force, and further improve the overall strength and durability; finally, due to the reduction of internal porosity and the stronger bonding force between the carbon fiber tow 2 and the thermoplastic resin, a smoother and denser product tow can be obtained, which not only improves the surface quality and appearance of the product tow, but also reduces the defects caused by pores.

[0037] In the present invention, the carbon fiber tow 2 is unfolded in advance, then pressed into a sandwich structure with a thermoplastic resin film, and then extruded into a tow-like structure through a molding die, which fundamentally solves the problem that high-viscosity thermoplastic resin is difficult to penetrate into the tightly arranged carbon fiber tow 2 and the problem of insufficient interface bonding strength between the carbon fiber tow 2 and the thermoplastic resin, and provides a simple and effective solution for the preparation of high-performance carbon fiber reinforced thermoplastic tows.

[0038] According to a preferred embodiment, Figure 1 As shown, the carbon fiber spreading module includes: A carbon fiber tow unwinding unit 1, which is used to continuously supply a carbon fiber tow 2; A heating unit 3, which is used to remove the sizing agent on the surface of the carbon fiber tow 2; A pressure wheel unit 4, which is used to provide tension to the carbon fiber tow 2; A blowing unit 5, which is used to blow the carbon fiber tow 2; A tension sensor 6, which is used to detect the tension of the carbon fiber tow 2 in real time; The fiber spreading unit 7 is used to spread the carbon fiber tow 2 .

[0039] Furthermore, a carbon fiber tow unwinding unit 1, a heating unit 3, a pressure wheel unit 4, a blowing unit 5, a tension sensor 6 and a spreading unit 7 are sequentially arranged along the supply direction of the carbon fiber tow 2. When working, the carbon fiber tow unwinding unit 1 feeds the carbon fiber tow 2 into the heating unit 3, removes the sizing agent on the carbon fiber tow 2 by means of high temperature, provides appropriate tension through the pressure wheel mechanism 4, blows the carbon fiber tow 2 by the blowing mechanism 5, and spreads the carbon fiber tow 2 appropriately, and detects the tension of the carbon fiber tow 2 in real time through the tension sensor 6. After the carbon fiber tow 2 enters the spreading unit 7, the carbon fiber tow 2 is spread by means of the lateral airflow generated by the negative pressure exhaust unit.

[0040] In the present invention, the unwinding speed of the carbon fiber tow unwinding unit 1 is 200-500 mm / min, preferably 200-300 mm / min, for example 220 mm / min.

[0041] Among them, a lower unwinding speed helps to better control the tension and uniformity of the carbon fiber tow 2; a too fast unwinding speed may cause the carbon fiber tow 2 to stretch, break or entangle, affecting the quality of the final product. An unwinding speed of 200-500 mm / min helps to achieve high quality control standards.

[0042] In the present invention, the carbon fiber tow 2 is heated to 300-500° C. by the heating unit 3 to remove the sizing agent of the carbon fiber tow 2. Preferably, the heating temperature is 330-380° C., for example, 350 degrees Celsius.

[0043] Among them, the sizing agent is mainly used to protect the carbon fiber tow 2 from damage during the manufacturing and transportation process and improve its bonding performance with the thermosetting resin, but the sizing agent will hinder the bonding of the carbon fiber tow 2 with the thermoplastic resin; removing the sizing agent can enhance the interface bonding between the carbon fiber tow 2 and the thermoplastic resin, thereby improving the overall performance of the product. The heat resistance of the carbon fiber tow 2 is very high. The sizing agent decomposes or burns in the temperature range of 300~500℃, but it will not affect the structure of the carbon fiber tow 2.

[0044] In the present invention, if Figure 2 As shown, the pressure wheel unit 4 includes a mounting plate 21 and a top plate 14 , wherein the mounting plate 21 is perpendicular to the moving direction of the carbon fiber tow 2 , and the top plate 14 is perpendicular to the mounting plate 21 and is mounted on the top of the mounting plate 21 .

[0045] Furthermore, a linear rail 20 is fixedly provided on the surface of the mounting plate 21, and a slider 19 is provided on the linear rail 20, and the slider 19 is fixedly connected to the PU wheel hanging plate 16, and the linear rail 20 provides guidance for the slider 19 and the PU wheel hanging plate 16 to ensure that the slider 19 and the PU wheel hanging plate 16 slide up and down on the linear rail 20.

[0046] In the present invention, the width and length of the slider 19 are smaller than the corresponding width and length of the PU wheel hanging plate 16 to ensure that the slider 19 can move freely under the PU wheel hanging plate 16; the slider 19 is flush with the top of the PU wheel hanging plate 16.

[0047] In the present invention, a clamping screw 15 is provided on the top plate 14, and the clamping screw 15 is used to control the height of the PU wheel hanging plate 16. More specifically, the clamping screw 15 passes through the top plate 14 and extends downward, and the PU wheel hanging plate 16 is located at the lower end of the clamping screw 15. By rotating the clamping screw 15, that is, adjusting the extension length of the clamping screw 15, the height of the lower PU wheel hanging plate 16 is controlled.

[0048] In the present invention, a PU wheel upper shaft 17 is fixedly provided below the PU wheel hanging plate 16, and the end of the PU wheel upper shaft 17 supports the first PU wheel 18, and the first PU wheel 18 can rotate freely. A PU wheel lower shaft 171 is provided on the mounting plate 21 and below the PU wheel hanging plate 16, and the end of the PU wheel lower shaft 171 supports the second PU wheel 181, and the second PU wheel 181 can rotate freely. The first PU wheel 18 and the second PU wheel 181 are arranged opposite to each other. During operation, the carbon fiber tow 2 passes between the first PU wheel 18 and the second PU wheel 181. The position of the slider 19 is preliminarily adjusted to adjust the position of the PU wheel hanging plate 16. Then, the pressing screw 15 is adjusted to tighten the PU wheel hanging plate 16 to accurately adjust the height of the first PU wheel 18 on the PU wheel hanging plate 16. Since the second PU wheel 181 is fixedly set on the mounting plate 21, the position of the first PU wheel 18 is adjusted to control the distance between the first PU wheel 18 and the second PU wheel 181 to control the extrusion force between the first PU wheel 18 and the second PU wheel 181. When the carbon fiber tow 2 passes through, the resistance formed makes the carbon fiber tow 2 maintain a certain tension, and the tension is detected in real time by the tension sensor 6.

[0049] In the present invention, the tension of the carbon fiber tow 2 is controlled to be 2-30N, preferably 2-8N, for example 4N.

[0050] If the tension is too small, the carbon fiber tow 2 may become loose or knotted; if the tension is too large, the tow may break or be damaged. 2-30N is sufficient to maintain the straightness and uniformity of the carbon fiber tow 2.

[0051] In the present invention, the blowing unit 5 is used to blow the fiber bundle 2 into a relatively loose bundle, which is convenient for the subsequent fiber spreading process.

[0052] In the present invention, the blowing unit 5 blows vertically over the carbon fiber tows 2 at a wind speed of 1-3 m / s, so that the spacing between the carbon fiber tows 2 is expanded to 1.5-3 mm, preferably 2-3 mm, for example 2.2 mm.

[0053] Among them, the wind speed of 1~3m / s can effectively control the distance between the carbon fiber tows 2 while maintaining the integrity of the carbon fiber tows 2.

[0054] In the present invention, the fiber spreading unit 7 utilizes the airflow to expand the width of the carbon fiber tow 2 to 3-6 mm, preferably 5-6 mm, for example 6 mm. This width is conducive to better infiltration of the subsequent thermoplastic film into the fiber interior.

[0055] In the present invention, if Figure 3 As shown, the fiber spreading unit 7 includes a first air outlet plate 22, a second air outlet plate 26, a fiber inlet plate 27 and a fiber outlet plate 24. The first air outlet plate 22 and the second air outlet plate 26 are arranged opposite to each other, and the fiber inlet plate 27 and the fiber outlet plate 24 are arranged opposite to each other. The first air outlet plate 22, the second air outlet plate 26, the fiber inlet plate 27 and the fiber outlet plate 24 have the same thickness and height, and their ends are perpendicular to each other, that is, they form a cubic structure. The cubic structure formed by the first air outlet plate 22, the second air outlet plate 26, the fiber inlet plate 27 and the fiber outlet plate 24 is provided with a bottom plate 25 at the bottom and a top plate at the top.

[0056] Furthermore, the thickness is 3-8 mm, preferably 5-8 mm, for example 7 mm. A larger plate thickness is beneficial to the stability of the structure.

[0057] Furthermore, the height is 20-40 mm, preferably 20-30 mm, for example 22 mm. A smaller height will reduce the internal space volume of the wire spreading structure, which is conducive to forming high-speed airflow and promoting better wire spreading.

[0058] In the present invention, the fiber inlet plate 27 is provided with a hole, and the fiber outlet plate 24 is provided with a hole. The holes on the fiber inlet plate 27 and the holes on the fiber outlet plate 24 are of the same size and are relatively positioned. During operation, the carbon fiber tow 2 enters along the holes on the fiber inlet plate 27 and exits along the holes on the fiber outlet plate 24.

[0059] In the present invention, in order to allow enough carbon fiber bundles 2 to enter and exit through the holes on the fiber inlet plate 27 and the holes on the fiber outlet plate 24, the holes on the fiber inlet plate 27 and the holes on the fiber outlet plate 24 are large enough, and their shapes are not limited to rectangles, diamonds or circles. Taking rectangles as an example, their sizes are usually (30~40) mm×(10~20) mm, for example 35 mm×20 mm.

[0060] In the present invention, the first air outlet plate 22 and the second air outlet plate 26 are both provided with vents, which are of the same size and opposite to each other, and the vents are used for gas circulation. The shape of the vents is not limited to rectangle, diamond or circle. Taking rectangle as an example, its size is usually (30-40) mm×(10-20) mm, for example, 40 mm×15 mm.

[0061] According to a preferred embodiment, at least two air volume adjustment plates 23 are provided in parallel between the first air outlet plate 22 and the second air outlet plate 26, and the air volume adjustment plates 23 are an even number, and the air volume adjustment plates 23 are symmetrically distributed on both sides of the carbon fiber tow 2, and one end of each air volume adjustment plate 23 abuts against the fiber inlet plate 27, and the other end abuts against the fiber outlet plate 24, and the size of the air volume adjustment plate 23 is preferably consistent with the first air outlet plate 22 or the second air outlet plate 26; preferably, two air volume adjustment plates 23 are provided between the first air outlet plate 22 and the second air outlet plate 26.

[0062] In one embodiment, taking two air volume adjustment plates 23 as an example, the air volume adjustment plates 23 are symmetrically distributed on both sides of the carbon fiber tow 2, and the distance between the two air volume adjustment plates 23 is 10-20 mm, preferably 10-15 mm, for example 12 mm. The distance between the air volume adjustment plate 23 close to the first air outlet plate 22 and the first air outlet plate 22 is 10-20 mm, preferably 12-16 mm, for example 14 mm; the distance between the air volume adjustment plate 23 close to the second air outlet plate 26 and the second air outlet plate 26 is preferably consistent with the distance between the air volume adjustment plate 23 close to the first air outlet plate 22 and the first air outlet plate 22.

[0063] In the present invention, the air volume adjustment plate 23 is provided with a plurality of holes for ventilation, preferably two rows of holes, each row of 10 to 20 holes, for example 16 holes. The holes are not limited to regular shapes such as square, diamond, triangle or irregular shapes, and the size of the holes is not strictly limited.

[0064] In the present invention, negative pressure exhaust units are respectively connected on both sides of the fiber inlet plate 27 and the fiber outlet plate 24. The negative pressure exhaust unit on one side of the fiber inlet plate 27 allows the wind to flow in along the direction of the holes on the fiber inlet plate 27 and along the moving direction of the carbon fiber bundle 2, and then flow out along the direction of the holes on the air volume adjustment plates 23 on both sides. The negative pressure exhaust unit on one side of the fiber outlet plate 24 allows the wind to flow in along the direction of the holes on the fiber outlet plate 24 and against the moving direction of the carbon fiber bundle 2, and then flow out along the direction of the holes on the air volume adjustment plates 23 on both sides.

[0065] Furthermore, the wind speed of the negative pressure exhaust unit is controlled to be 10-30 m / s, preferably 10-25 m / s, for example 12 m / s. Too small a wind speed cannot achieve an effective silk spreading effect, and too large a wind speed will cause airflow turbulence.

[0066] In one embodiment, the distance between the carbon fiber tows 2 before and after the fiber spreading is as follows: Figure 4 As shown, the left side shows the distance between the carbon fiber tows 2 before the fiber spreading, and the right side shows the distance between the carbon fiber tows 2 after the fiber spreading. The distance between the carbon fiber tows 2 is expanded by the fiber spreading unit 7 under the action of the airflow, which is beneficial to the subsequent infiltration of the thermoplastic resin.

[0067] In the present invention, the film extrusion module comprises: A thermoplastic film roll unit 8 for continuously supplying thermoplastic resin; A hot rolling roller unit 9 is used for heating and pressurizing, and controls the gap between the upper and lower rolling rollers to be between 0.1 and 0.5 mm, preferably between 0.2 and 0.4 mm, for example, 0.4 mm, so that the thermoplastic resin and the unfolded carbon fiber tow 2 form a sandwich structure; A screw extruder 10 is used to mix the thermoplastic resin and the unfolded carbon fiber tow 2 and extrude them once, and the temperature is controlled to be 10-20° C. above the melting temperature of the thermoplastic resin; The molding die 11 is used for secondary extrusion of the thermoplastic resin and the thermoplastic resin film containing the carbon fiber tow 2 to obtain a tow-shaped composite material.

[0068] In the present invention, along the processing direction, the filament spreading unit 7 is sequentially connected to the hot rolling roller unit 9 and the screw extruder 10, and the hot rolling roller unit 9 is also connected to the thermoplastic film roll unit 8, and a forming die 11 is provided below the screw extruder 10. During operation, the thermoplastic film roll unit 8 supplies thermoplastic resin, and the thermoplastic resin and the unfolded carbon fiber tow 2 enter the hot rolling roller unit 9 together to form a sandwich structure, and then are mixed and extruded once through the screw extruder 10, and are extruded twice through the forming die 11 to form a tow-shaped composite material.

[0069] Furthermore, the hot rolling roller unit 9 includes one or more pairs of rollers, and the one or more pairs of rollers are symmetrically distributed on both sides of the upper and lower sides along the moving direction of the carbon fiber tow 2, and the upper roller and the lower roller are respectively connected to the thermoplastic film roll unit 8. During operation, the rollers symmetrically distributed on both sides are used for the movement of the carbon fiber tow 2, and the upper and lower layers of thermoplastic resin are continuously supplied to the hot rolling roller unit 9 by the upper and lower thermoplastic film roll units 8, respectively. The rollers symmetrically distributed on both sides of the hot rolling roller unit 9 heat the thermoplastic resin into a fluid, and when the carbon fiber tow 2 passes through, the carbon fiber tow 2 is clamped between the upper and lower layers of thermoplastic resin by pressure to form a sandwich structure.

[0070] In the present invention, the gap between the symmetrically distributed rollers on the upper and lower sides is controlled to be 0.1-0.5 mm, preferably 0.2-0.4 mm, for example 0.3 mm. Too small a gap will cause poor film lamination and form pores, while too large a gap will weaken the interface performance between the fiber and the resin.

[0071] In the present invention, the unwinding speed of the thermoplastic film roll unit 8 is 8-50 mm / min, preferably 10-35 mm / min, for example 20 mm / min.

[0072] In the present invention, the thermoplastic resin generally used has a width of 3 to 5 mm and a thickness of 0.1 to 0.5 mm, for example, a width of 4 mm and a thickness of 0.2 mm.

[0073] In the present invention, the temperature of the rollers in the hot rolling roller unit 9, that is, the temperature when the interlayer is formed, is 160-230°C, preferably 180-200°C. For example, too low a temperature will make the viscosity of the thermoplastic resin too high, making it difficult to infiltrate into the fiber, and too high a temperature will make the viscosity of the resin too low, causing flow and making it impossible to form.

[0074] In the present invention, the die temperature of the molding die 11 is 20-30° C. higher than the temperature of the roller.

[0075] In one embodiment, the sandwich structure formed by the carbon fiber tow 2 and the thermoplastic resin in the hot rolling roller unit 9 is as follows: Figure 5 As shown in (a), the structure of the composite material in the form of a tow is formed by the forming die 11. Figure 5 As shown in (b), it can be seen that the carbon fiber tow 2 is evenly distributed in the thermoplastic resin. The diameter of the carbon fiber tow 2 in the tow-shaped composite material is 0.3-0.8 mm, for example, 0.4 mm. The tow diameter is detected in real time by a laser diameter gauge, and the tow diameter is accurately adjusted and controlled by automatically adjusting the winding speed.

[0076] In the present invention, the molding module comprises: An air cooling unit 12, which is used to cool the temperature of the tow-shaped composite material to below 40°C to obtain a fiber-reinforced thermoplastic tow; The winding unit 13 is used for winding the fiber-reinforced thermoplastic tow.

[0077] Among them, along the processing direction, the forming die 11 is connected to the air cooling unit 12 and the winding unit 13 in sequence.

[0078] In one embodiment, the structure of the fiber-reinforced thermoplastic tow after winding is as follows Figure 6 Shown.

[0079] On the other hand, according to the present invention, a method for preparing a carbon fiber reinforced thermoplastic tow for additive manufacturing is provided, the method comprising: Step 1, removing the sizing agent on the surface of the carbon fiber filaments 2 and unfolding the carbon fiber filament bundles 2; Step 2, forming a sandwich structure with the thermoplastic resin and the unfolded carbon fiber tow 2, and mixing and extruding them to obtain a tow-shaped composite material; Step 3, cooling and shaping the tow-shaped composite material to obtain the fiber-reinforced thermoplastic tow.

[0080] The present invention is further described below through specific examples, but these examples are merely exemplary and do not constitute any limitation to the scope of protection of the present invention.

[0081] Example 1 like Figures 1 to 6As shown, a T300-1K carbon fiber tow 2 is selected and unwound through a carbon fiber tow unwinding unit 1 at an unwinding speed of 20 mm / min. The carbon fiber tow 2 is heated to 340°C by a heating unit 3 to remove the sizing agent of the carbon fiber tow 2. The tension of the carbon fiber tow 2 is controlled at 4N by a pressure wheel unit 4. The carbon fiber tow 2 is blown vertically by a blowing unit 5 at a wind speed of 2 m / s, so that the carbon fiber tow 2 is expanded to 2.2 mm. When the carbon fiber tow 2 passes through the spreading unit 7, the exhaust wind speed is controlled to be 10 m / s, and the width of the carbon fiber tow 2 is expanded to 3 mm. The thermoplastic film roll unit 8 is used to unwind the PETG / PLA thermoplastic resin with a width of 4mm and a thickness of 0.5mm at an unwinding speed of 20mm / min. The rollers symmetrically distributed on the upper and lower sides of the hot roller unit 9 heat the thermoplastic resin into a fluid. The carbon fiber tow 2 clamped between the rollers symmetrically distributed on the upper and lower sides and the upper and lower layers of thermoplastic resin are pressed into a sandwich structure. In this process, the gap between the upper and lower rollers is controlled to be 0.3mm, and the temperature of the rollers is 190°C. The sandwich structure is mixed and extruded once by a screw extruder 10, and extruded twice through a forming die 11 to form a tow-like composite material. The die temperature of the forming die 11 is 210°C. The diameter of the carbon fiber tow 2 in the tow-like composite material is 0.4mm. The tow-like composite material is cooled to below 40°C by an air cooling unit 12 to obtain a product fiber-reinforced thermoplastic tow, and then wound by a winding unit 13. The porosity test result of the carbon fiber tow is 3.0±0.5%, and the tensile strength of the carbon fiber reinforced PLA composite material sample printed by 3D printing technology is 522±15MPa. This embodiment confirms the following technical effects: the thermoplastic resin is evenly wrapped on the carbon fiber tow and fills the gaps between the fibers, and the mechanical properties are improved by a relatively simple process.

[0082] Example 2 like Figures 1 to 6As shown, a T700SC-3K carbon fiber tow 2 is selected and unwound through a carbon fiber tow unwinding unit 1 at an unwinding speed of 180 mm / min. The carbon fiber tow 2 is heated to 380°C by a heating unit 3 to remove the sizing agent of the carbon fiber tow 2. The tension of the carbon fiber tow 2 is controlled at 5N by a pressure wheel unit 4. The carbon fiber tow 2 is blown vertically by a blowing unit 5 at a wind speed of 3 m / s, so that the carbon fiber tow 2 is expanded to 4 mm. When the carbon fiber tow 2 passes through the spreading unit 7, the exhaust wind speed is controlled to be 13 m / s, and the width of the carbon fiber tow 2 is expanded to 6 mm. The thermoplastic film roll unit 8 is used to unwind the PBAT / PLA thermoplastic resin with a width of 8mm and a thickness of 0.2mm at an unwinding speed of 20mm / min. The rollers symmetrically distributed on the upper and lower sides of the hot roller unit 9 heat the thermoplastic resin into a fluid. The carbon fiber tow 2 clamped between the rollers symmetrically distributed on the upper and lower sides and the upper and lower layers of thermoplastic resin are pressed into a sandwich structure. In this process, the gap between the upper and lower rollers is controlled to be 0.4mm, and the temperature of the rollers is 210°C. The sandwich structure is mixed and extruded once by a screw extruder 10, and extruded twice through a forming die 11 to form a tow-like composite material. The die temperature of the forming die 11 is 205°C. The diameter of the carbon fiber tow 2 in the tow-like composite material is 0.6mm. The tow-like composite material is cooled to below 40°C by an air cooling unit 12 to obtain a product fiber-reinforced thermoplastic tow, and then wound by a winding unit 13. The porosity test result of the carbon fiber tow is 3.2±0.4%, and the tensile strength of the carbon fiber reinforced PLA composite material sample printed by 3D printing technology is 867±26MPa. This embodiment also confirms the following technical effects: the thermoplastic resin is evenly wrapped on the carbon fiber tow and fills the gaps between the fibers, thereby improving the mechanical properties with a relatively simple process.

[0083] The basic principle of the present invention is described above in conjunction with specific embodiments. However, it should be pointed out that the advantages, strengths, effects, etc. mentioned in the present invention are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. must be possessed by each embodiment of the present invention. In addition, the specific details disclosed above are only for the purpose of illustration and facilitation of understanding, rather than limitation, and the above details do not limit the present invention to being implemented by adopting the above specific details.

[0084] The above description has been given for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments of the present invention to the forms disclosed herein. Although a number of example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

Claims

1. A device for preparing carbon fiber reinforced thermoplastic tow for additive manufacturing, characterized in that: These include, A carbon fiber spreading module, which is used to remove the sizing agent on the surface of the carbon fiber tow and to spread the carbon fiber tow; A thermal processing module, which is used to form a sandwich structure with a thermoplastic resin and the unfolded carbon fiber tow, and mix and extrude them to obtain a tow-shaped composite material; The forming module is used for cooling and shaping the tow-shaped composite material to obtain carbon fiber reinforced thermoplastic tow.

2. The device for preparing carbon fiber reinforced thermoplastic tow for additive manufacturing according to claim 1, characterized in that: Preferably, along the supply direction of the carbon fiber tows, the carbon fiber spreading module is sequentially connected to the thermal processing module and the forming module.

3. The device for preparing carbon fiber reinforced thermoplastic tow for additive manufacturing according to claim 1, characterized in that: The carbon fiber spreading module comprises: A pressure wheel unit for providing tension to the carbon fiber tow; The fiber spreading unit is used to spread the carbon fiber tow.

4. The device for preparing carbon fiber reinforced thermoplastic tow for additive manufacturing according to claim 3, characterized in that: The pressure wheel unit comprises a mounting plate perpendicular to the moving direction of the carbon fiber tow and a top plate perpendicular to the mounting plate and mounted on the top of the mounting plate.

5. The device for preparing carbon fiber reinforced thermoplastic tow for additive manufacturing according to claim 3, characterized in that: The fiber spreading unit spreads the distance between the carbon fiber bundles to 3-10 mm.

6. The device for preparing carbon fiber reinforced thermoplastic tow for additive manufacturing according to claim 4, characterized in that: The wire spreading unit is a cubic structure.

7. The device for preparing carbon fiber reinforced thermoplastic tow for additive manufacturing according to claim 1, characterized in that: The diameter of the carbon fiber tow in the tow-shaped composite material is 0.4-0.8 mm.

8. A method for preparing a carbon fiber reinforced thermoplastic filament preparation device for additive manufacturing according to any one of claims 1 to 7.

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