Manufacturing method for fiber reinforced plastic molded products

Abstract

To provide a manufacturing method of a fiber-reinforced plastic molded product, which is capable of suppressing variations in resin pressure.SOLUTION: There is provided a manufacturing method of a fiber-reinforced plastic molded product, comprising the steps of: installing a preform 10 in a mold 20; and supplying a resin composition to an outer periphery of the preform in the mold. The manufacturing method is configured in that: regarding a push pin 27 that presses the resin composition to a necessary pressure, a sliding resistance force is measured when the push pin moves; and the push pin is controlled by a force required to press the resin composition plus the sliding resistance force.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a molded article reinforced by a fiber layer impregnated with resin (fiber-reinforced resin molded article). [Background technology]

[0002] For example, a high-pressure tank for a fuel cell vehicle has a liner that forms the internal space of the high-pressure tank, and a reinforcing layer made of a fiber layer impregnated with resin is disposed around the periphery of the liner to achieve high strength. Furthermore, not only high-pressure tanks for fuel cell vehicles, but also other products may be formed as fiber-reinforced resin molded products by disposing a reinforcing layer to achieve high strength.

[0003] One method for producing such fiber-reinforced plastic molded products is RTM (Resin Transfer Molding), in which a preform is prepared by wrapping fibers around a liner to form a fiber layer, and the fiber layer is then impregnated with uncured resin and cured to form a reinforcing layer.

[0004] Patent Document 1 discloses a method in which, when impregnating a mold with resin by RTM, the resin is temporarily stored in a resin reservoir, and a piston (push pin) is pushed up by air pressure to inject the resin into the mold. Furthermore, Patent Document 2 discloses a method for manufacturing a high-pressure tank in which a fiber layer is impregnated with a resin and then hardened. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-084317 [Patent Document 2] Japanese Patent Publication No. 2021-154639 Summary of the Invention [Problem to be solved by the invention]

[0006] Resin pressure is controlled by the pushing force of the push pin (torque in the case of servo motor control), but sliding resistance occurs when the push pin operates, and this sliding resistance changes with each molding due to changes in the state of resin adhesion to the seal part of the push pin, etc. And because the resin pressure decreases by the amount of the torque of the sliding resistance, changes in sliding resistance also change the resin pressure, causing variations in resin pressure and, as a result, there is a risk of variations in the state of resin impregnation.

[0007] The present disclosure provides a method for manufacturing a fiber-reinforced plastic molded product that can suppress variations in resin pressure. [Means for solving the problem]

[0008] The present application discloses a method for producing a fiber-reinforced plastic molded product, which includes the steps of placing a preform in a mold and supplying a resin composition to the outer periphery of the preform within the mold, in which a push pin presses the resin composition to the required pressure, and the method measures the sliding resistance force as the push pin moves, and controls the push pin with a force obtained by adding the sliding resistance force to the force required to press the resin composition.

[0009] The sliding resistance may be measured before the resin composition is filled into the mold.

[0010] The push pin may be controlled by a servo motor, and the force may be obtained by its torque.

[0011] The push pin may be hydraulically controlled and may be powered by its operating pressure. [Effects of the Invention]

[0012] According to the manufacturing method of the present disclosure, variations in resin pressure can be suppressed by correcting for the sliding resistance of the push pin. [Brief explanation of the drawings]

[0013] [Figure 1]FIG. 1(a) is an exploded view illustrating a mold 20 and a preform 10, showing a cross section along the axis of the preform, and FIG. 1(b) is a cross section perpendicular to the axis. [Figure 2] FIG. 2(a) is a diagram illustrating one position in which the preform 10 is placed in the mold 20, and is a cross section taken along the axis of the preform, while FIG. 2(b) is a cross section perpendicular to the axis. [Figure 3] FIG. 3 is a diagram illustrating the flow of the manufacturing method S100 for the high-pressure tank (fiber-reinforced resin molded product). [Figure 4] FIG. 4 is a diagram illustrating the flow of the push pin moving condition calculation S130. [Figure 5] FIG. 5 is a diagram illustrating the supply of the resin composition S140. [Figure 6] FIG. 6 is a diagram illustrating the step S160 of applying pressure with a push pin. DETAILED DESCRIPTION OF THE INVENTION

[0014] 1. Preform and impregnation equipment 1 and 2 schematically show a preform 10 to be impregnated with a resin composition, and a mold 20 for impregnating the resin composition into the preform 10. In Fig. 1, Fig. 2, and the subsequent figures, the mold 20 is shown as a cross section (hatched), the preform 10 is shown as a surface rather than a cross section, and the internal shape of the preform 10 is shown by dashed lines. Fig. 1 is an exploded view of the mold 20 and the preform 10. Fig. 1(a) is a cross section along the cylindrical axis of the preform 10, and Fig. 1(b) is a cross section perpendicular to the axis, taken along A-A' in Fig. 1(a). Figure 2 is a diagram showing a scene in which the preform 10 is placed in the mold 20. Figure 2(a) is a cross section along the cylindrical axis of the preform 10, and Figure 2(b) is a cross section perpendicular to the axis, taken along B-B' in Figure 2(a).

[0015] As will be understood from the following description, the present disclosure relates to a fiber-reinforced resin molded product produced by so-called RTM (Resin Transfer Molding), in which a fiber layer provided in a preform is impregnated with a resin composition and then cured to form a reinforcing layer.

[0016] 1.1.Preform The preform is an intermediate part that will eventually become a fiber-reinforced plastic molded product such as a high-pressure tank. Hereinafter, a high-pressure tank will be used as an example of one embodiment of a fiber-reinforced plastic molded product. This embodiment is a high-pressure tank for a fuel cell vehicle. As can be seen from FIGS. 1 and 2, the preform 10 is configured to have at least a liner 11 and a fiber layer 12 .

[0017] The liner 11 is a hollow cylindrical member that defines the internal space of the high-pressure tank. The liner may be made of any material that can hold the contents stored in the internal space without leakage, and known materials may be used, such as nylon resin, polyethylene-based synthetic resin, or metal such as stainless steel or aluminum. The thickness of the liner 11 is not particularly limited, but is preferably 0.5 mm to 1.0 mm.

[0018] The fiber layer 12 is a layer in which fibers are wound in multiple layers to a predetermined thickness on the outer surface of the liner 11. The thickness of the fiber layer 12 is not particularly limited as it is determined by the required strength, but is generally set to about 10 mm to 30 mm. In particular, high-pressure tanks for fuel cell vehicles require a thick fiber layer to ensure strength, and from the perspective of impregnating the fiber layer with resin, the pressure during impregnation becomes high. The fibers of the fiber layer are carbon fibers, specifically, band-shaped carbon fiber bundles each having a predetermined cross-sectional shape (e.g., rectangular cross-section) formed by bundling carbon fibers. The fiber layer is formed by winding such carbon fiber bundles around the outer surface of the liner 11. The winding of the fibers (bundles) around the outer surface of the liner 11 is performed, for example, by a filament winding method.

[0019] The fiber layer 12 of such a preform 10 is impregnated with resin, and a protective layer of glass fiber is further formed on the outer periphery to form a high-pressure tank.

[0020] Types The mold 20 is a mold for impregnating the fiber layer 12 of the preform 10 with the resin composition, and in this embodiment is configured to have an upper mold 21 and a lower mold 25. By overlapping the upper mold 21 and the lower mold 25, an internal space conforming to the shape of the preform 10 is formed inside the mold 20, and the preform 10 is placed in this space. This internal space can be formed as a sealed space.

[0021] In this embodiment, the upper mold 21 can move relative to the lower mold 25 as shown by arrow C in Figures 1(a), 1(b), 1(a), and 1(b). This allows the preform 10 to be placed in the mold 20 and removed (demolded) from the mold 20, and also allows the preform 10 to be moved so as to apply pressure to the preform 10 and to be moved so as to release this applied pressure.

[0022] The mold 20 is also provided with a flow path 20a that communicates with the outside. The flow path 20a is shown in Figures 1(b) and 2(b) and is a flow path for the resin composition. The resin composition before curing is supplied from this flow path 20a toward the fiber layer 12. Therefore, the flow path 20a reaches the fiber layer 12 of the preform 10 placed in the mold 20 from the outside of the mold 20. In this embodiment, the flow path 20a extends from above the upper mold 21, penetrates the upper mold 21, and reaches the surface that overlaps with the lower mold 25, and from there extends to the preform 10, the periphery of the preform 10, and the opposite side via grooves provided in the lower mold 25.

[0023] In addition, a flow path for vacuum degassing (not shown) may be formed.

[0024] Furthermore, in this embodiment, lower mold 25 is provided with cylinder 26 that communicates with flow path 20a and forms a space that can draw in a portion of the resin composition present in flow path 20a. Cylinder 26 is provided with push pin 27, which is a piston that can move inside cylinder 26 in directions toward and away from flow path 20a as indicated by arrow D. A seal member is provided between the cylinder 26 and the push pin 27 to prevent leakage of the resin composition, and this seal generates sliding resistance when the push pin 27 moves. In addition, the movement of such a piston can be controlled by a servo motor or hydraulically. In this embodiment, as can be seen from FIG. 2(b), such a set of cylinders 26 and pistons 27 are arranged on both sides of the axis when viewed in a radial cross section of the preform 10.

[0025] The material used for the mold 20 is not particularly limited, but metal is preferably used as usual, and the mold 20 is a so-called metal mold.

[0026] 1.3.Other In the mold 20, a device corresponding to the flow path 20a is placed. That is, a device for supplying the resin composition to be impregnated into the flow path 20a is connected to the mold 20. Furthermore, a vacuum pump is connected to the degassing flow path (not shown). The specific specifications of each device are not particularly limited, and known devices can be used.

[0027] 2. Manufacturing method of high-pressure tank Next, a method for manufacturing a high-pressure tank will be described. The method will be described using the above-mentioned mold 20. However, the present invention is not limited to the use of the mold 20.

[0028] Fig. 3 shows the flow of a manufacturing method S100 for a high-pressure tank according to one example of a method for manufacturing a fiber-reinforced resin molded product. As can be seen from Fig. 3, the manufacturing method S100 for a high-pressure tank according to this embodiment includes the steps of: placing in a mold S110, degassing S120, calculating push pin movement conditions S130, supplying a resin composition S140, changing to a clamped state S150, applying pressure with a push pin S160, stopping the supply of the resin composition S170, and releasing from the mold S180. Each step will be described below.

[0029] 2.1. Installation in the mold S110 In setting in the mold S110 (sometimes referred to as "step S110"), the preform 10 is set in the mold 20, and the mold 20 is put into an unloaded state. That is, the preform 10 is set inside the mold 20, and at this time, the upper mold 21 is positioned so as to be separated from the lower mold 25 so that the gap between the upper mold 21 and the preform 10 is larger than the gap between the lower mold 25 and the preform 10. Even in this unloaded state, the inside of the mold 20 remains an enclosed space, allowing for degassing in subsequent steps and supplying the resin composition without leakage. More specifically, in this embodiment, the preform 10 is placed on the lower mold 25 in a state where the upper mold 21 is completely separated from the lower mold 25 and the top surface of the lower mold 25 is completely exposed and open. Next, the upper mold 21 is placed so as to cover the lower mold 25 and the preform 10 placed thereon. Then, the upper mold 21 is placed so as to be separated from the lower mold 25 as described above.

[0030] 2.2. Degassing S120 In degassing S120 (sometimes referred to as "step S120"), after the preform 10 and mold 20 are in the state obtained in step S110, vacuum degassing is performed to remove air from the outer periphery of the preform 10. More specifically, in this embodiment, after the preform 10 and mold 20 are in the state obtained in step S110, degassing is performed using a vacuum pump through a flow path not shown. Vacuum degassing allows the resin composition to be impregnated to penetrate the fiber layer more smoothly. This also has a certain effect in preventing air bubbles from being entrained in the impregnated resin.

[0031] 2.3. Push pin movement condition calculation S130 In push pin moving condition calculation S130 (sometimes referred to as "step S130"), the force for moving the push pin 27 is calculated. The pressure for impregnating the fiber layer with the resin composition is controlled by the pushing force of the push pin 27, but as mentioned above, sliding resistance occurs when the push pin 27 is operated, and this sliding resistance changes with each molding due to changes in the adhesion state of the resin composition to the seal part of the push pin, etc. Then, since the resin pressure is reduced by the torque of the sliding resistance, the resin pressure also changes due to the change in sliding resistance, resulting in variations in the resin pressure. Therefore, in step S130, the sliding resistance force is obtained in advance, and preparations are made to set the movement conditions (pressing conditions) of the push pin 27 in the subsequent pressurization step S160 by the push pin taking this sliding resistance force into consideration. Specifically, step S130 includes steps S131 for measuring the sliding resistance force and S132 for calculating the conditions, as shown in FIG.

[0032] 2.3.1. Sliding resistance force measurement S131 In the sliding resistance measurement S131 (sometimes referred to as "step S131"), the sliding resistance force when the push pin 27 moves inside the cylinder 26 is measured. Specifically, the push pin 27 is moved in its current state (a state in which the resin composition is not filled in the flow path 20a and the cylinder 26), and the force required for the movement at that time is taken as the sliding resistance force. Therefore, in step S131, the push pin 27 is moved to obtain the force required for that. There are no particular limitations on the method for measuring the sliding resistance force, but if the push pin 27 is moved by a servo motor, the torque required for movement can be obtained from the torque required for movement, and if it is moved by hydraulic pressure, the force required to move the piston 27 can be obtained from the operating pressure required for movement, and this can be used as the sliding resistance force.

[0033] 2.3.2. Condition Calculation S132 In condition calculation S132 (sometimes referred to as "step S132"), the applied force, which is the force to be applied to the push pin 27 in the step of applying pressure with the push pin S160 described later, is calculated taking into account the sliding resistance force obtained in step S131. Specifically, the following formula is used. Applied force = Target resin pressure x Conversion coefficient + Frictional resistance force

[0034] Here, the target resin pressure is the pressure required to impregnate the fiber layer with the resin composition, and the conversion factor is a factor for converting this target resin pressure into force.

[0035] When the push pin 27 is controlled by a servo motor, the force can be expressed in terms of torque instead of force. In this case, the torque to be applied to the push pin 27 is calculated by the following formula. Applied torque = Target resin pressure x Torque conversion coefficient + Friction resistance torque

[0036] Here, the torque conversion coefficient is a coefficient for converting the target resin pressure into the required torque, and the frictional resistance torque is the torque of the servo motor obtained when measuring the frictional resistance force in step S131.

[0037] 2.4. Supply of Resin Composition S140 In step S140 of supplying the resin composition (sometimes referred to as "step S140"), the resin composition before curing is supplied to the flow path 20a. More specifically, in this embodiment, as shown in FIG. 5, the resin composition before curing is supplied to the flow path 20a from a device that supplies the resin composition, and the resin composition fills the flow path 20a and reaches the outer periphery of the fiber layer 12 of the preform 10. At this time, as can be seen from FIG. 5, the push pin 27 has been moved away from the flow path 20a, and the resin composition is also filled into the cylinder 26 between the flow path 20a and the push pin 27.

[0038] The resin composition is not particularly limited as long as it reaches and penetrates the fiber layer in a fluid state and can then be cured by some method to increase the strength of the fiber layer. Examples of suitable resin compositions include thermosetting resins that are cured by heat, such as epoxy resins and unsaturated polyester resins that contain an amine- or anhydride-based curing accelerator and a rubber-based toughening agent. Other examples include resin compositions that use an epoxy resin as the base agent and are cured by mixing a curing agent into the resin composition. In this case, the resin composition, which is a mixture of the base agent and the curing agent, reaches and penetrates the fiber layer between the time of mixing and the time of curing, and automatically hardens.

[0039] 2.5. Change to tightening state S150 In the change to the clamped state S150 (sometimes referred to as "step S150"), the upper mold 21 and the lower mold 25 are moved closer to each other, and the mold 20 is placed in the clamped state. In the clamped state, the preform 10 is placed on the mold 20, and the upper mold 21 and the lower mold 25 are completely connected and clamped. Even in this clamped state, it is preferable that there is a slight gap between the fiber layer 12 of the preform 10 before impregnation and the surfaces of the upper mold 21 and the lower mold 25. This gap takes into account the fact that the volume of the fiber layer 12 after impregnation with the resin composition will be larger than the volume before impregnation. This gap in the clamped state is the same between the upper mold 21 and the preform 10 and between the lower mold 25 and the preform 10.

[0040] This step S150 increases the pressure that the resin composition receives from the mold 20, accelerating the impregnation of the resin composition. In this embodiment, this is done by bringing the upper mold 21 closer to the lower mold 25. However, if sufficient impregnation can be achieved by applying pressure with a push pin S160, which will be described later, this step S150 is not necessarily required and may not be provided.

[0041] 2.6.Pressure by push pin S160 In step S160 of applying pressure with a push pin (sometimes referred to as "step S160"), the push pin 27 is pressed so as to move it toward the flow path 20a, as shown in Fig. 6. This presses the resin composition to a required resin pressure, thereby accelerating the impregnation of the resin composition into the fiber layer. At this time, the force and torque applied to the push pin 27 are the force and torque obtained in step S130. This takes into consideration the frictional resistance force that changes depending on the state, so it is possible to adjust the change in pressing force due to the change in frictional resistance force, enabling stable pressing and impregnation of the resin composition.

[0042] 2.7.Supply of resin composition S170 In S170 (sometimes referred to as "step S170"), when the resin composition has sufficiently impregnated the fiber layer 12 in step S160 and the desired amount has been supplied, the supply of the resin composition is stopped. Then, the process waits for the resin composition to harden.

[0043] 2.8.Mold Release S180 In demolding S180 (sometimes referred to as "step S180"), the resin-impregnated preform 10 is released from the mold 20 after the resin composition has been cured in step S170. In this embodiment, the upper mold 21 of the mold 20 is separated from the lower mold 25 to be in an open state, thereby performing mold release.

[0044] 3. Other forms In the above-mentioned manufacturing method S100 of a high-pressure tank, the measurement of the frictional resistance force and the calculation of the applied force and applied torque are performed before the resin composition is supplied to the flow path 20a, but this is not limited to this. For example, after the resin composition is supplied to the flow path 20a, an area can be provided in which the push pin 27 can be moved without being subjected to a load from the resin composition on the push pin 27, and the frictional resistance force can be measured and the applied force and applied torque can be calculated.

[0045] 4. Effects etc. According to the present disclosure, by measuring the sliding resistance of a push pin that applies a force to impregnate a fiber layer with a resin composition, calculating a control force (torque or hydraulic pressure) corrected for the sliding resistance, and using the calculated force during molding, it is possible to reduce variations in resin pressure and improve accuracy. According to tests conducted by the inventors, multiple tests were conducted to measure variations in the target resin pressure, and it was found that by controlling the resin pressure by correcting for the sliding resistance as disclosed herein, the σ value was 0.07, which was an improvement over the σ value of 0.26 obtained without the correction. [Explanation of symbols]

[0046] 10...preform, 11...liner, 12...fiber layer, 20...mold, 20a...flow path, 21...upper mold, 25...lower mold, 26...cylinder, 27...push pin (piston)

Claims

1. A method for producing a fiber-reinforced resin molded product, comprising: placing a preform in a mold; and supplying a resin composition to an outer periphery of the preform in the mold; a push pin that presses the resin composition to a necessary pressure is measured for a sliding resistance force when the push pin moves before the resin composition is filled into the mold, and the push pin is controlled with a force that is the sum of the sliding resistance force and the force required to press the resin composition. A method for manufacturing a fiber-reinforced plastic molded product.

2. The method for manufacturing a fiber-reinforced resin molded product according to claim 1 , wherein the push pin is controlled by a servo motor, and the force is obtained by the torque of the servo motor.

3. The method for manufacturing a fiber-reinforced plastic molded product according to claim 1 , wherein the push pin is controlled by hydraulic pressure, and the force is obtained by the operating pressure of the push pin.

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