High-roundness continuous fiber composite reinforced prepreg wire and preparation method thereof

Abstract

The invention discloses a high roundness continuous fiber composite reinforced prepreg wire material and a preparation method thereof, the prepreg wire material is a special wire material for 3D printing manufactured by FFF fuse wires and is composed of a reinforcing material and a matrix, the matrix is thermoplastic resin, and the reinforcing material is chopped fibers and continuous fibers. The preparation method comprises the following steps: blending thermoplastic resin particles and chopped fibers according to a set ratio, and carrying out extrusion pelletizing to obtain short fiber reinforced particles; after short fiber reinforced granules are extruded by a single screw, the short fiber reinforced granules and the continuous fiber bundles enter a hot mold impregnation bin from different channels at the same time, and impregnation rods with different angles are arranged in the impregnation bin so as to promote a matrix to be adhered to the continuous fiber bundles; and then the continuous fiber bundle impregnated with the short fiber reinforced particles passes through a forming die with a certain diameter, and is finally drawn and wound to a wire coil. After the prepared prepreg wire is synergistically enhanced by the continuous fibers and the chopped fibers, not only are the fiber content and the mechanical property improved, but also the diameter uniformity of the wire is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the field of continuous fiber reinforced thermoplastic resin matrix composites, and particularly relates to a prepreg wire with high roundness and continuous fiber composite reinforcement and a preparation method thereof. Background Art

[0002] Fiber reinforced plastic composites (FRP) play an extremely important role in aerospace engineering due to their advantages such as high strength, low coefficient of thermal expansion, and strong corrosion resistance. Traditional FRP manufacturing processes, such as pultrusion, compression molding, and film stacking, cannot produce complex FRP parts due to the limitations of high-cost molds and complex processes. In recent years, 3D printing technologies represented by fused filament fabrication (FFF) have developed rapidly. This technology can not only retain the excellent inherent properties of FRP but also make full use of the advantages of strong flexibility and adaptability of 3D printing technology, providing a new method for manufacturing FRP parts with complex structures.

[0003] As the reinforcing phase in fiber reinforced composites, fibers bear the main load when the composites are stressed. Compared with short fiber reinforced resin-based filaments, continuous fiber reinforced resin-based filaments have better mechanical properties. For continuous fiber reinforced resin-based filaments, an increase in fiber content is beneficial to improving the mechanical properties of the composites. However, an excessively high fiber volume content will reduce the interfacial bonding performance between the fibers and the matrix and bring more pore defects, resulting in poor surface quality and weak interlayer bonding ability during the forming process due to low resin content and poor resin impregnation effect, seriously affecting the forming quality and mechanical properties of the formed parts. Therefore, limited by the fiber content, the mechanical properties of continuous fiber reinforced resin-based filaments have reached a deadlock; and currently, most of the preparation methods of continuous fiber reinforced resin-based filaments prepared in China to achieve the effect of fiber bundle impregnation will cause problems with poor diameter uniformity of the filaments. Therefore, it is urgent to solve the above technical problems. Summary of the Invention

[0004] The purpose of the present invention is to prepare a prepreg wire with high roundness and continuous fiber composite reinforcement, which has the comprehensive performance of single-type short fiber or continuous fiber reinforced resin filaments, and has excellent mechanical properties and a round and uniform wire diameter under the premise of a high fiber content.

[0005] The purpose of the present invention is achieved as follows: Thermoplastic resin particles and chopped fibers are melt-blended and extruded to prepare a particulate material with short fiber reinforcement. The continuous fibers are melt-impregnated with the resin particulate material with short fiber reinforcement, and finally a prepreg wire is prepared by synchronously reinforcing the resin with chopped fibers and continuous fibers.

[0006] In order to achieve the above purpose, the technical solution of the present invention is as follows:

[0007] Further, the short fiber-reinforced pellet includes chopped fibers and a thermoplastic resin. The chopped fibers are at least one of carbon fiber, glass fiber, basalt fiber, and plant fiber; the thermoplastic resin is one of PPS, PA66, PEEK, and PLA.

[0008] Further, the chopped fibers are powders with lengths of 60 mesh, 100 mesh, 200 mesh, and 300 mesh; the thermoplastic resin is a pellet.

[0009] Further, the short fiber-reinforced pellet is prepared by extrusion granulation, and the temperatures of each zone of the extruder are set according to the resin characteristics.

[0010] Further, the continuous fiber is at least one of carbon fiber, glass fiber, basalt fiber, and plant fiber; preferably, the carbon fiber is 1K or 1.5K.

[0011] Further, the continuous fiber melt impregnation process is as follows:

[0012] (1) The resin pellet containing short fiber reinforcement is extruded by a single screw and enters the fiber-matrix mixing zone from different channels simultaneously with the continuous fiber bundle;

[0013] (2) The continuous fiber bundle impregnated by the matrix passes through the sizing die;

[0014] (3) Finally, it is drawn and wound onto a spool.

[0015] Further, the feeding speed of the matrix is proportional to the feeding speed of the continuous carbon fiber bundle;

[0016] Further, the fiber-matrix mixing zone is composed of a hot mold, which mainly melts and impregnates the continuous fiber;

[0017] Further, different-angle impregnation rods are provided in the melt impregnation mold chamber. When the fiber passes through the impregnation rod, due to the action of tension, the fiber bundle unfolds to a certain width, and the molten resin enters the area between the fiber bundle and the impregnation roll driven by the drag of the fiber. A certain pressure is generated in this area, making it easier for the resin matrix to enter the impregnation area between the two. This process is repeated, causing the fiber bundle to continuously bear the extrusion of the melt on both sides, so that the polymer melt penetrates into the fiber interior, achieving single-filament-level impregnation and dispersion, and achieving a good impregnation effect.

[0018] Further, the sizing die has a certain diameter, including 0.36 mm, 0.4 mm, 0.6 mm, and 0.8 mm. Preferably, the die diameter is 0.4 mm.

[0019] The beneficial effects of the present invention are:

[0020] (1) Prepare prepreg filaments by simultaneously reinforcing resin with chopped fibers and continuous fibers. After passing through an impregnation bin equipped with impregnation rods at different angles, the problem of poor impregnation with a high fiber content is solved, and the mechanical properties of the prepreg filaments are improved.

[0021] (2) Use resin reinforced with chopped fibers as the matrix to melt-impregnate continuous fibers, forming a uniform support structure on the outer surface of the continuous fiber bundle, improving the roundness and uniformity of the prepreg filament diameter. Brief Description of the Drawings

[0022] Figure 1 Schematic diagram for testing the minimum bending stiffness of prepreg filaments;

[0023] Figure 2 SEM observation diagram of the prepreg filament cross-section (a) prepreg filament of Example 1 (b) prepreg filament of Comparative Example 1;

[0024] Figure 3 Fiber mass fraction of prepreg filaments (a) Example 1; (b) Comparative Example 1; Detailed Embodiments

[0025] The present invention will be specifically introduced below in conjunction with the drawings and specific embodiments.

[0026] Example 1

[0027] A preparation method of prepreg filaments of short / continuous fiber composite-reinforced PA66 resin includes the following specific steps:

[0028] Mix PA66 resin and chopped fibers of 200 mesh in a high-speed mixer at a mass ratio of 62:10. After mixing evenly, melt-extrude through an extruder. Set the temperature of the first zone of the extruder at 240 °C, the second zone at 250 °C, the third zone at 260 °C, the fourth zone at 270 °C, the fifth zone at 280 °C, the sixth zone at 280 °C, the runner temperature at 280 °C, and the die temperature at 280 °C. Then cut into pellets containing short-fiber-reinforced PA66 via a pelletizer.

[0029] Extrude the pellets containing short-fiber-reinforced PA66 through a single-screw extruder and simultaneously introduce 1K continuous carbon fiber bundles from different channels into a melt impregnation die. Set the temperature of the first zone of the single-screw extruder at 250 °C, the second zone at 285 °C, the third zone at 285 °C, the fourth zone at 285 °C, and the temperature of the melt impregnation die at 285 °C. The outlet of the melt impregnation die is a die orifice. Each bundle of continuous carbon fiber bundles passes through a die orifice with a diameter of 0.4 mm, and finally wind and reel onto a spool to prepare prepreg filaments of short / continuous carbon fiber composite-reinforced PA66 with a diameter of about 0.4 mm.

[0030] Comparative Example 1

[0031] The difference from Example 1 is that short fibers are not added to the prepreg filaments for reinforcement.

[0032] The granular material of PA66 is extruded by a single-screw extruder and enters the melt impregnation die from different channels simultaneously with a 1K continuous carbon fiber bundle. The temperature of the first zone of the single-screw extruder is set at 250°C, the second zone at 285°C, the third zone at 285°C, the fourth zone at 285°C, and the melt impregnation die temperature at 285°C. There is a die at the outlet of the melt impregnation die. Each bundle of continuous carbon fiber passes through a die with a diameter of 0.4 mm, and finally it is drawn and wound onto a spool to obtain the prepreg filaments of continuous carbon fiber composite reinforced PA66.

[0033] Test and analysis

[0034] 1. Filament diameter

[0035] Take a 30-mm-long prepreg filament, and use a vernier caliper to measure the diameters at at least 5 positions at certain intervals, and compare the average diameters to obtain the deviation of the prepreg filament diameter.

[0036] As can be seen from Table 1, the diameters of the prepreg filaments prepared in Example 1 are relatively uniform and stable, meeting the set diameter range of 0.4 mm, and the diameters of the prepreg filaments are relatively uniform; the average diameter of the prepreg filaments measured in Comparative Example 1 is larger than the set 0.4-mm diameter, and the diameter deviation is also large. It shows that the diameter uniformity of the prepreg filaments is improved after being filled with short fibers.

[0037] Table 1 Average diameter distribution of prepreg filaments

[0038]

[0039] 2. Curvature radius test

[0040] Design a fixture with fiber channels of different radii. The fiber channels are embedded in a Teflon tube (2×1) to reduce the damping when the fibers pass through and protect the fibers. The minimum curvature radius at which the fibers can pass through without being broken is tested, which can indirectly reflect the toughness of the filaments.

[0041] The test results show that the minimum curvature radii of the prepreg filaments in Example 1 and Comparative Example 1 are both R1.5, indicating that the toughness change of the resin reinforced with short / continuous carbon fiber composites is not significant compared to that reinforced only with continuous carbon fiber.

[0042] Table 2 Minimum curvature radius

[0043] Example 1 Control Example 1 Minimum radius of curvature R 1.5 1.5

[0044] 3. Fiber distribution

[0045] Three segments of each prepreg filament were taken to prepare epoxy resin specimens. A bench-top electron microscope was used to observe the fiber cross-section and scan the images to evaluate the fiber distribution. As follows Figure 2 , in Example 1, there are many aggregation regions in the fiber distribution, and there are many dispersed micro-pores inside, and the fiber uniformity is poor. In Comparative Example 1, there are aggregation regions in the fiber distribution, and there are many relatively large pores inside. After the chopped fibers are filled into the continuous carbon fiber reinforced resin filaments, the prepreg filaments are fuller and rounder, and the product quality is better.

[0046] 4. Fiber mass content test

[0047] Samples were taken from each prepreg filament and subjected to a TGA thermogravimetric decomposition test in a nitrogen environment until only carbon fibers remained. The test data is the mass fraction. The TGA curve is as follows Figure 3 As shown, it is calculated that the fiber content in Example 1 is 44.17 wt%, and the fiber content of the prepreg filament in Comparative Example 1 is relatively small, which is 34.66 wt%.

[0048] 5. Mechanical properties

[0049] According to the test method for tensile properties of carbon fiber multifilament GB / T 3362-2017, 5 pieces (250 mm, with thick cardboard reinforcement pieces pasted at both ends) were taken from each prepreg filament to prepare tensile specimens. During the tensile test, a preload of 5 N was applied, and the tensile speed was 1 mm / min.

[0050] The overall tensile performance of the prepreg filament in Example 1 is better than that in Comparative Example 1, and the performance is relatively stable.

[0051] Table 3 Tensile data of prepreg filaments

[0052]

Claims

1. A prepreg filament reinforced by high-roundness continuous fibers, characterized in that, Comprising reinforcing material and matrix materials, wherein the reinforcing material is chopped fiber and continuous fiber, and the matrix is a thermoplastic resin.

2. The preparation method of a prepreg filament reinforced by high-roundness continuous fibers according to claim 1, characterized in that, Comprising the following specific steps: (1) Blending and extruding thermoplastic resin particles with chopped fibers to prepare pelletized material reinforced with short fibers; (2) The resin pelletized material reinforced with short fibers and a continuous fiber bundle enter the fiber-matrix mixing zone from different channels simultaneously after being extruded by a single-screw extruder; (3) The continuous fiber bundle impregnated by the matrix passes through a shaping die; (4) Finally, it is drawn and wound onto a spool.

3. The preparation method of a prepreg filament reinforced by high-roundness continuous fibers according to claim 2, characterized in that, In the step (1), the pelletized material reinforced with short fibers comprises chopped fibers and a thermoplastic resin. The chopped fibers are at least one of carbon fiber, glass fiber, basalt fiber, plant fiber, etc., and are powders with lengths of 60 mesh, 100 mesh, 200 mesh, and 300 mesh; the thermoplastic resin is one of PPS, PA66, PEEK, and PLA and is in pellet form.

4. The preparation method of a prepreg filament reinforced by high-roundness continuous fibers according to claim 2, characterized in that In the step (1), the equipment for blending and extrusion is an extruder, and the temperatures of each zone of the extruder are set according to the resin characteristics.

5. The preparation method of a prepreg filament reinforced by high-roundness continuous fibers according to claim 2, characterized in that In the step (2), the continuous fiber is at least one of carbon fiber, glass fiber, basalt fiber, and plant fiber. Preferably, the carbon fiber is 1K or 1.5K.

6. In the step (2) according to claim 2, the shaping die has a certain diameter, including 0.4 mm, 0.6 mm, and 0.8 mm. Preferably, the die diameter is 0.4 mm.

7. The preparation method of a prepreg wire material reinforced by high-roundness continuous fibers according to claim 2, characterized in that, In the step (3), the fiber-matrix mixing zone is composed of a hot die, which mainly performs melt impregnation on the continuous fiber.

8. According to claim 7, the melt impregnation die chamber is provided with impregnation rods at different angles. When the fiber passes through the impregnation rods, due to the action of tension, the fiber bundle unfolds to a certain width, and the resin melt penetrates into the fiber interior, achieving impregnation and dispersion at the single-filament level and achieving a good impregnation effect.

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