Short fiber multiphase reinforced thermoplastic resin structure with different fiber content, bonded body thereof, and manufacturing method

Abstract

To provide a short fiber multi-phase reinforced thermoplastic resin structure having multiple phases of short fibers with different fiber contents, a joint body thereof, and a manufacturing method thereof.SOLUTION: Before laser irradiation, a short carbon fiber SC of a short carbon fiber reinforced thermoplastic resin structure 1 is arranged discretely and spaced apart along a X direction (orientation direction). A laser beam L from a laser light source 31 is locally irradiated onto a portion 1a of a surface of the short carbon fiber reinforced thermoplastic resin structure 1, heating the thermoplastic resin to a temperature above its melting point and causing it to move or evaporate. After the laser irradiation, recesses 31 are formed in the short carbon fiber reinforced thermoplastic resin structure 1, and as a result, a short carbon fiber reinforced multi-phase thermoplastic resin structure 3 having different fiber contents is formed. In the recesses 31, the thermoplastic resin disappears, so that the short carbon fibers SC are locally exposed at a bottom of the recesses 31 and overlap with each other, essentially converting into short carbon fibers SC' having a high fiber content.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a short fiber multi-phase reinforced thermoplastic resin structure containing short fiber multi-phase fibers with different fiber contents, a bonded body thereof, and a manufacturing method thereof. [Background technology]

[0002] There are two methods for reinforcing thermoplastic resin structures formed by 3D printers, injection molding, compression molding, etc. with fibers: one that uses short fibers and one that uses long fibers (continuous fibers) (see Patent Document 1). In particular, carbon fiber reinforced plastic (CFRP) is superior to metals in terms of specific rigidity and specific strength (see Non-Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-98042 [Non-patent literature]

[0004] [Non-Patent Document 1] T. Gerngross, D. Nieberl, “Automated manufacturing of large, three-dimensional CFRP parts from dry textiles”, CEAS Aeronautical Journal, 7(2), 2016, 241-257. Summary of the Invention [Problem to be solved by the invention]

[0005] However, while short fibers can be used as reinforcements to take advantage of their advantages, their mechanical properties are limited. In particular, when electrical conductivity is required, short carbon fibers have low or no electrical conductivity compared to carbon nanotubes and carbon black, making it difficult to ensure electrical conductivity in short carbon fiber-reinforced thermoplastic resin structures. On the other hand, long fibers, when used as reinforcements, have excellent mechanical properties, but when molding long fiber-reinforced thermoplastic resin structures with complex shapes, the long fibers are folded back, reducing the strength of those areas. One solution is to install a cutting mechanism to cut the long fiber-reinforced thermoplastic resin structure to a predetermined length. This results in increased manufacturing costs. Furthermore, when 3D printing is performed using only long fiber thermoplastic resin, surface irregularities are created. Therefore, short fiber thermoplastic resin is used for the entire surface, which results in the inability to ensure electrical and thermal conductivity of the surface. Furthermore, if the volume content of continuous short fibers is high during 3D printing, there is the issue that they are prone to clogging the nozzle and are difficult to bend, which limits the curvature of the printing path, making it impossible to print with continuous short fibers at a high volume content. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the short fiber multi-phase reinforced thermoplastic resin structure according to the present invention has a first short fiber having a first fiber length and a first fiber content locally on at least a part of the surface of the short fiber multi-phase reinforced thermoplastic resin structure. Contains The first short fiber multi-phase reinforced thermoplastic resin structure is formed on at least a portion of the surface thereof. a second fiber length equal to the first fiber length and a second fiber content less than the first fiber content; Fiber content have The second short fiber The short fibers are contained in the short fiber multiphase reinforced thermoplastic resin structure, and the surface of a part of the structure is in a hair-like state where the short fibers come into contact with each other to form a conductive layer and exhibit hydrophilicity with a contact angle of water droplets of 30° or less. It is something.

[0007] Furthermore, the joined short fiber multi-phase reinforced thermoplastic resin structures of the present invention have a first short fiber having a high fiber content locally arranged on at least a portion of the surface of each of the first and second short fiber multi-phase reinforced thermoplastic resin structures, and a second short fiber having a lower fiber content than the first short fiber arranged on the first and second short fiber multi-phase reinforced thermoplastic resin structures other than at least a portion of the surface, and at least a portion of the surface of the first short fiber multi-phase reinforced thermoplastic resin structure and at least a portion of the surface of the second short fiber multi-phase reinforced thermoplastic resin structure are melt-bonded, and the first and second short fibers are electrically conductive or highly thermally conductive.

[0008] Furthermore, the method for producing a short fiber multi-phase reinforced thermoplastic resin structure according to the present invention comprises: having a second fiber length and a second fiber content; No. 2 a molding step for molding a short fiber reinforced thermoplastic resin structure comprising the short fibers; multi-phase At least a part of the thermoplastic resin on the surface of the reinforced thermoplastic resin structure is locally melted, moved or evaporated to form short fibers. multi-phase and a resin melting step for converting at least a portion of the surface of the reinforced thermoplastic resin structure into second short fibers having a fiber content higher than that of the first short fibers. The resin melting step involves irradiating at least a portion of the surface of the short fiber multiphase reinforced thermoplastic resin structure with a defocused scanning laser beam to promote mutual contact between the short fibers, thereby forming a conductive layer. This is what we do. [Effects of the Invention]

[0009] According to the present invention, short fibers with different fiber content are used as reinforcing materials, which reduces the manufacturing cost of composite materials with locally different physical properties, and increases the strength by locally increasing the fiber content. If the short fibers on the surface are electrically and thermally conductive, the electrical conductivity and thermal conductivity of the surface can be ensured. [Brief explanation of the drawings]

[0010] [Figure 1] 1A and 1B are diagrams for explaining the short carbon fiber reinforced thermoplastic resin structure molding process of an embodiment of the method for manufacturing a short fiber multiphase reinforced thermoplastic resin structure according to the present invention, in which (A) is a cross-sectional view showing a short carbon fiber reinforced thermoplastic resin structure, and (B) is a diagram showing a 3D printer. [Figure 2]1A and 1B are diagrams for explaining the laser irradiation step as a heating step in an embodiment of the method for producing a short-fiber multiphase reinforced thermoplastic resin structure according to the present invention, in which (A) is a cross-sectional view and an electron microscope image of a short-carbon fiber reinforced thermoplastic resin structure before laser irradiation, (B) is a cross-sectional view of the short-carbon fiber reinforced thermoplastic resin structure during laser irradiation, and (C) is a cross-sectional view and an electron microscope image of the short-carbon fiber multiphase reinforced thermoplastic resin structure after laser irradiation. [Figure 3] This shows another short carbon fiber multiphase reinforced thermoplastic resin structure after laser irradiation. (A) is an electron microscope image, (B) is a photograph of a water droplet when it is dropped on the structure, and (C) is a photograph of a water droplet when it is dropped on the short carbon fiber reinforced thermoplastic resin structure before laser irradiation. [Figure 4] 3 is a diagram showing an application example of the short carbon fiber multi-phase reinforced thermoplastic resin structure of FIG. 1 and FIG. 2. [Figure 5] 1 and 2. (A) shows a joint interface type resin fusion bonding, (B) shows a one-sided current type resin fusion bonding, and (C) shows a vise pressure joint interface type resin fusion bonding. [Figure 6] 1 and 2. FIG. 4 is a diagram illustrating another bonding method for the short carbon fiber multi-phase reinforced thermoplastic resin structure shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] 1 and 2 are diagrams for explaining an embodiment of the method for producing a short fiber multi-phase reinforced thermoplastic resin structure according to the present invention.

[0012] First, the short carbon fiber reinforced thermoplastic resin structure molding process will be described with reference to Figure 1. (A) is a cross-sectional view of the short carbon fiber reinforced thermoplastic resin structure, and (B) is a front view of the 3D printer.

[0013] The short carbon fiber reinforced thermoplastic resin structure 1 shown in FIG. 1(A) is molded by a 3D printer 2 shown in FIG. 1(B).

[0014] As shown in FIG. 1B, a short carbon fiber reinforced filament F wound around a loop 11 is supplied to a 3D printer 2. The 3D printer 2 is, for example, an X-Plus printer from QiDi Tech, and is composed of an extruder 21, a heated nozzle 22, and a print bed 23. The short carbon fiber reinforced filament F wound around the loop 11 is a thermoplastic composite material containing short carbon fibers (SCFRP). The higher the carbon fiber content of this thermoplastic composite material, the stronger it becomes, but the short carbon fiber reinforced filament F becomes hard and brittle. As a result, it cannot be wound around the loop 11. For this reason, the fiber content of the short carbon fiber reinforced filament F is low, at 10 to 25%.

[0015] In Fig. 1(B), the short carbon fiber reinforced filament F is adjusted and extruded by two gears 21a and 21b of the extruder 21, and is injected from a heater nozzle 22 with a heater temperature of about 270 to 290°C. The thermoplastic resin of the short carbon fiber reinforced filament F is, for example, Nylon (registered trademark), and the short carbon fibers are short, with an average length of about 50 to 300 µm.

[0016] The obtained short carbon fiber reinforced thermoplastic resin structure 1 shown in FIG. 1(A) is laminated in multiple layers in the Z direction, and the short carbon fibers in each layer are oriented along the X direction (orientation direction) shown in FIG. 1(B).

[0017] Next, the laser irradiation step as a heating step will be described with reference to Fig. 2. The laser irradiation step is also performed during the molding step using the filament F. Fig. 2(A) is a cross-sectional view and an electron microscope image of the short carbon fiber reinforced thermoplastic resin structure before the laser irradiation step, Fig. 2(B) is a diagram explaining the laser irradiation, and Fig. 2(C) is a cross-sectional view and an electron microscope image of the short carbon fiber multiphase reinforced thermoplastic resin structure after the laser irradiation step.

[0018] 2(A), the short carbon fibers SC of the short carbon fiber reinforced thermoplastic resin structure 1 before laser irradiation are arranged discretely and spaced apart along the X direction (orientation direction). Therefore, the carbon fiber content is low throughout the short carbon fiber reinforced thermoplastic resin structure 1, and therefore the strength of the short carbon fiber reinforced thermoplastic resin structure 1 is not very high.

[0019] As shown in Figure 2(B), a laser light source LS The laser beam L from the laser diode is locally irradiated onto a portion 1a of the surface of the short carbon fiber reinforced thermoplastic resin structure 1. For example, the conditions for the laser beam L are as follows. 455nm wavelength semiconductor laser Laser power: 40% Focal length F: 40mm Therefore, the laser beam L is absorbed by the surface portion 1a of the short carbon fiber reinforced thermoplastic resin structure 1, which heats the thermoplastic resin above its melting point and causes it to move or evaporate. In this case, if the laser beam L is too strong, too much thermoplastic resin will burn and disappear. To prevent this, the defocus amount DF of the laser beam L is adjusted to, for example, 20 mm. Also, a galvano scanning mirror can be provided to extend the portion 1a in the X or Y direction, and the laser beam L can be scanned at, for example, 5 mm / s.

[0020] After the laser irradiation, as shown in FIG. 2C, recesses 31 are formed in the short carbon fiber reinforced thermoplastic resin structure 1, resulting in a short carbon fiber multiphase reinforced thermoplastic resin structure 3 composed of short carbon fibers with different fiber contents. That is, since the thermoplastic resin disappears in the recesses 31, the short carbon fibers SC are locally exposed at the bottom of the recesses 31, overlapping and essentially converted into short carbon fibers SC'. As a result, the bottom region of the recesses 31 becomes a short carbon fiber region with a high fiber content, e.g., 45 to 50%, and therefore its strength is increased. This results in a short carbon fiber multiphase reinforced thermoplastic resin structure 3 having both a region of short carbon fibers SC and a region of short carbon fibers SC'. In this way, a short carbon fiber multiphase reinforced thermoplastic resin structure 3 is realized that achieves both low manufacturing cost and high strength. Furthermore, when short carbon fibers SC' are included, high electrical conductivity can also be achieved.

[0021] Furthermore, when the laser irradiation conditions are changed or a thermoplastic resin with low transparency is used, the surface of the thermoplastic resin becomes hairy, as shown in the electron microscope image in Figure 3(A). When a water droplet is placed directly on this hairy surface, the contact angle of the water droplet is approximately 30° or less, as shown in Figure 3(B), indicating hydrophilicity. Furthermore, as shown in Figure 3(C), before irradiation with laser light L, the contact angle of the water droplet is 90°, indicating hydrophobicity. In this way, the surface of the short carbon fiber multiphase reinforced thermoplastic resin structure 3 can be modified.

[0022] When the thermoplastic resin is a polyamide resin (PA-6), such as Nylon (registered trademark), the laser light L passes through the Nylon (registered trademark) and is absorbed by the short carbon fibers SC, causing the Nylon (registered trademark) to melt and scatter, as described above. Therefore, to make the surface of Nylon (registered trademark) hairy, a dye is added to the Nylon (registered trademark) to reduce the transmittance of the Nylon (registered trademark).

[0023] When the thermoplastic resin is polyetherimide (PEI), the laser light L is absorbed by the surface of the polyetherimide (PEI), and only the resin melts and vaporizes. Therefore, a hairy surface is formed with short carbon fibers SC half embedded in it. To create a conductive surface with polyetherimide (PEI), an infrared laser or a multi-step laser process is required, such as removing the resin with laser light of intensity A and then applying laser light of intensity B with short carbon fibers.

[0024] FIG. 4 is a top view for explaining an application example in which the short carbon fiber multiphase reinforced thermoplastic resin structure of FIGS. 1 and 2 is made to function as a strain sensor.

[0025] As shown in Figures 4A, 4B, 4C, 4D, and 4E, short carbon fiber multiphase reinforced thermoplastic resin structures 3-A, 3-B, 3-C, 3-D, and 3-E have lengths L = 120 mm, width W = 18 mm, and thickness W = 1.6 mm. The recesses 31-A, 31-B, 31-C, 31-D, and 31-E, each 65% deep in the short carbon fiber region with a high fiber content, are formed with electrodes E1 and E2 of 5 mm x 15 mm and a current path E3 of 1 mm width connected between the electrodes E1 and E2. In this case, the current path E3 of the short carbon fiber multiphase reinforced thermoplastic resin structures 3-A, 3-B, 3-C, 3-D, and 3-E has 0, 1, 2, 3, and 4 folds and lengths of 30 mm, 64 mm, 8.2 mm, 116 mm, and 134 mm. As a result, the initial resistance values ​​of the short carbon fiber multi-phase reinforced thermoplastic resin structures 3-A, 3-B, 3-C, 3-D, and 3-E were 0.68 kΩ, 6.42 kΩ, 7.29 kΩ, 7.72 kΩ, and 13.29 kΩ. In this way, the initial resistance value of the short carbon fiber multi-phase reinforced thermoplastic resin structure 3 can be adjusted by changing the pattern of the recesses 31, and it can be made to function as a strain sensor.

[0026] In the above-mentioned short carbon fiber multi-phase reinforced thermoplastic resin structure 3, the fiber content at the bottom of the recess 31 where the surface resin has been moved or evaporated by the laser light L is high, and therefore the electrical resistance value is low. Therefore, two short carbon fiber multi-phase reinforced thermoplastic resin structures 3 can be joined by melting the resin through resistance heating.

[0027] FIG. 5 is a diagram illustrating a joined body of the short carbon fiber multi-phase reinforced thermoplastic resin structures shown in FIGS.

[0028] In Fig. 5(A), two short carbon fiber multi-phase reinforced thermoplastic resin structures 3, 3' are joined by a joint interface type resin fusion joining. That is, electrodes E3, E4 are provided in the recesses 31, 31' of the short carbon fiber regions with a high fiber content of the short carbon fiber multi-phase reinforced thermoplastic resin structures 3, 3'. Then, with the recesses 31, 31' of the short carbon fiber regions with a high fiber content of the short carbon fiber multi-phase reinforced thermoplastic resin structures 3, 3' in contact with each other, an electric current is passed between the electrodes E3, E4, and the two are fusion-joined by Joule heat. Note that the recesses 31, 31' do not need to be formed entirely, but may be formed partially, for example, linearly.

[0029] In Fig. 5(B), two short carbon fiber multiphase reinforced thermoplastic resin structures 3, 3' are joined by one-sided current-type resin fusion joining. That is, electrodes E3, E4 are provided in the recesses 31 or 31' in the short carbon fiber region with a high fiber content of one of the short carbon fiber multiphase reinforced thermoplastic resin structures 3, 3'. Then, with the recesses 31, 31' in the short carbon fiber region with a high fiber content of the short carbon fiber multiphase reinforced thermoplastic resin structures 3, 3' in contact with each other, current is passed between the electrodes E3, E4 to fusion-join the two structures by Joule heat. Note that in this case, too, the recesses 31, 31' do not need to be formed entirely, but may be formed partially, for example, linearly.

[0030] In Fig. 5(C), two short carbon fiber multi-phase reinforced thermoplastic resin structures 3, 3' are joined by a vise-processed joint interface-type resin fusion joining. That is, as in Fig. 5(A), electrodes E3, E4 are provided in the recesses 31 in the short carbon fiber regions with a high fiber content of the short carbon fiber multi-phase reinforced thermoplastic resin structures 3, 3'. The recesses 31 in the short carbon fiber regions with a high fiber content of the short carbon fiber multi-phase reinforced thermoplastic resin structures 3, 3' are brought into contact with each other and pushed back by the slits 4, 4'. An electric current is then passed between the electrodes E3, E4, and the two structures are fusion-joined by Joule heat. Note that, in this case, the recesses 31, 31' do not need to be formed entirely; they may be formed partially, for example, linearly.

[0031] Incidentally, the one-sided current-type resin fusion joining shown in FIG. 5(B) can also be performed as a vice-processed one-sided current-type resin fusion joining.

[0032] The joining methods shown in Figures 5A, 5B, and 5C can also be applied to joining two short carbon fiber multi-phase reinforced thermoplastic resin structures 3, 3' with completely different stacking directions as shown in Figure 6. That is, in Figure 6, the stacking direction of the short carbon fiber multi-phase reinforced thermoplastic resin structure 3 is the Z direction, while the stacking direction of the short carbon fiber multi-phase reinforced thermoplastic resin structure 3' is the X direction, so that the stacking directions are almost perpendicular to each other. Even in this case, the joining methods shown in Figures 5A, 5B, and 5C can be used to melt-join the short carbon fiber multi-phase reinforced thermoplastic resin structures 3, 3'.

[0033] 2(B), the laser irradiation is performed locally on a portion 1a of the surface of the short carbon fiber multi-phase reinforced thermoplastic resin structure 1, but it may be performed on the entire surface. In this case, a region of short carbon fiber SC' with a high fiber content is formed on the entire surface of the short carbon fiber multi-phase reinforced thermoplastic resin structure 1, while the short carbon fiber multi-phase reinforced thermoplastic resin structure 1 other than the surface remains as a region of short carbon fiber SC with a low fiber content.

[0034] In addition, in FIG. 2B, the short carbon fibers SC on the surface of the short carbon fiber-reinforced thermoplastic resin structure 1 are converted to short carbon fibers SC' by laser irradiation. However, other localized heat rays, such as xenon lamp light, other than laser light may also be used. Alternatively, a solvent that melts the thermoplastic resin may also be used. For example, if the thermoplastic resin is a polyamide resin such as Nylon (registered trademark), the short fibers can be left on the surface by locally melting it using the dissolving solution "e-Solv 21RS" (registered trademark) manufactured by Kaneko Chemical Co., Ltd. After that, high-temperature resin or adhesive can be dripped.

[0035] Furthermore, in the above-described embodiment, the recesses 31 and 31' are formed, but if protrusions are formed before the heating step and the heating step is then performed on these protrusions, the recesses 31 and 31' will not exist.

[0036] Furthermore, in the above-described embodiment, carbon fibers are used as the conductive fibers, but other conductive fibers, such as metal fibers of metal whiskers, ceramic fibers, or organic fibers, may also be used.

[0037] Furthermore, the thermoplastic resin may be other resins such as polyphenylene sulfide resin (PPS), polyetherimide (PEI), polyetheretherketone (PEEK) in addition to polyamide resin such as nylon (registered trademark).

[0038] Furthermore, the present invention can be applied to any obvious modifications of the above-described embodiments. [Explanation of symbols]

[0039] 1: Short carbon fiber multi-phase reinforced thermoplastic resin structure 11: Loop F: Short carbon fiber multi-phase reinforcing filament 2:3D printer 21: Extruder 21a, 21b: Gear 22: Heated nozzle 23: Print head 4, 4′: Vise SC: Short carbon fiber SC': Short carbon fiber with a high fiber content (overlap of exposed short carbon fiber) 3, 3-A, 3-B, 3-C, 3-D, 3-E, 3-F, 3-G, 3,3′: Short carbon fiber multiphase reinforced thermoplastic resin structures with different fiber contents 31, 31': recess

Claims

1. A short fiber multi-phase reinforced thermoplastic resin structure, First short fibers having a first fiber length and a first fiber content are locally contained in at least a portion of the surface of the short fiber multi-phase reinforced thermoplastic resin structure, The short fiber multi-phase reinforced thermoplastic resin structure other than the at least part of the surface contains second short fibers having a second fiber length identical to the first fiber length and a second fiber content smaller than the first fiber content, A short fiber multi-phase reinforced thermoplastic resin structure in which the surface of the portion of the structure is in a hair-like state where the short fibers are in contact with each other to form a conductive layer and exhibit hydrophilicity with a water droplet contact angle of 30° or less.

2. A short fiber multiphase reinforced thermoplastic resin structure as described in claim 1, wherein the thermoplastic resin is a thermoplastic resin containing a dye in accordance with an increase in transmittance.

3. 2. The short fiber multi-phase reinforced thermoplastic resin structure according to claim 1, wherein the first and second short fibers are electrically conductive.

4. 2. The short fiber multi-phase reinforced thermoplastic resin structure according to claim 1, wherein the first and second short fibers are carbon fibers.

5. The short fiber multiphase reinforced thermoplastic resin structure according to claim 3, wherein the portion has two electrode regions when viewed from the surface and a current path region that connects the two electrode regions and is narrower than the electrode regions, and acts as a strain sensor.

6. The short fiber multiphase reinforced thermoplastic resin structure according to claim 5 , wherein the current path region has a folded portion.

7. A bonded body of first and second short fiber multi-phase reinforced thermoplastic resin structures, The first short fibers are locally contained in at least a portion of the surface of each of the first and second short fiber multi-phase reinforced thermoplastic resin structures, The first and second short fiber multi-phase reinforced thermoplastic resin structure other than the at least part of the surface contains second short fibers having a fiber content lower than that of the first short fibers, At least a portion of the surface of the first short fiber multi-phase reinforced thermoplastic resin structure and at least a portion of the surface of the second short fiber multi-phase reinforced thermoplastic resin structure are melt-bonded together; A bonded body of a short fiber multi-phase reinforced thermoplastic resin structure, wherein the first and second short fibers are electrically conductive.

8. 8. A joined body of short fiber multi-phase reinforced thermoplastic resin structures according to claim 7, wherein the first and second short fibers are short carbon fibers.

9. A joined body of short fiber multi-phase reinforced thermoplastic resin structures according to claim 7, wherein the lamination direction of the first short fiber multi-phase reinforced thermoplastic resin structure is different from the lamination direction of the second short fiber multi-phase reinforced thermoplastic resin structure.

10. A molding process for molding a short fiber multi-phase reinforced thermoplastic resin structure comprising second short fibers having a second fiber length and a second fiber content; a resin melting step for locally melting, moving, or evaporating at least a portion of the thermoplastic resin on the surface of the short fiber multi-phase reinforced thermoplastic resin structure, and converting the at least a portion of the short fiber multi-phase reinforced thermoplastic resin structure into first short fibers having a first fiber length identical to the second fiber length and a first fiber content greater than the second fiber content; Equipped with The resin melting step is a method for manufacturing a short fiber multi-phase reinforced thermoplastic resin structure, in which a defocused scanning laser beam is irradiated onto at least a portion of the surface of the short fiber multi-phase reinforced thermoplastic resin structure to promote mutual contact between the short fibers and form a conductive layer.

11. 11. The method for producing a short fiber multi-phase reinforced thermoplastic resin structure according to claim 10, wherein the first and second short fibers are electrically conductive.

12. 12. The method for producing a short fiber multi-phase reinforced thermoplastic resin structure according to claim 11, wherein the first and second short fibers are carbon fibers.

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