Manufacturing method for fiber reinforced plastic molded products

Abstract

To provide a method for producing a fiber reinforced resin molded product that can improve productivity while reducing an amount of carbon fiber waste and ensuring a mechanical strength of the molded product.SOLUTION: A method for producing a fiber reinforced resin molded product includes producing a fiber reinforced resin molded product having a fiber volume content (Vf) of 45% or more to 52% or less by impregnating and curing a thermosetting resin material into a preform made by arranging tape substrates comprising carbon fiber bundles in a width direction and stacking them in a thickness direction, the preform placed inside a cavity of a mold, and then forming them. In the method for producing a fiber reinforced resin molded product, when the preform is produced, the tape substrates are arranged with a gap therebetween.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a fiber-reinforced plastic molded product, and more particularly to a method for manufacturing a fiber-reinforced plastic molded product that can reduce the amount of carbon fiber waste, ensure the mechanical strength of the molded product, and improve productivity. [Background technology]

[0002] A molding method for fiber-reinforced plastics has been proposed that is lightweight, has high mechanical strength, and maintains a good appearance while allowing for easy trimming and ensuring that the strength of the outer periphery is equivalent to that of the central part of the product (see Patent Document 1). This fiber-reinforced plastic molding method is characterized by constructing a preform in which a second substrate, in which reinforcing fibers have been pre-impregnated with resin, is placed on at least a portion of the outer periphery of a first substrate made solely of reinforcing fibers such as a woven fabric, and then placing the preform in a mold cavity, followed by injecting and curing resin. This molding method utilizes the RTM (Resin Transfer Molding) molding method. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-76356 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when attempting to further thicken the fiber-reinforced plastic as described in Patent Document 1, the reinforcing fibers, i.e., the woven portion made of carbon fibers, become thicker, which causes problems such as a longer resin impregnation time, which can lead to imperfect resin impregnation and a decrease in mechanical strength. Furthermore, taking longer for resin impregnation to prevent imperfect resin impregnation also causes a problem of reduced productivity. Furthermore, using carbon fiber woven fabrics in layers tends to increase the trimming amount during preform construction, which results in a large amount of carbon fiber waste.

[0005] The present invention has been made in consideration of the problems associated with the conventional technology, and aims to provide a method for manufacturing fiber-reinforced plastic molded products that can reduce the amount of carbon fiber waste, ensure the mechanical strength of the molded products, and improve productivity. [Means for solving the problem]

[0006] As a result of extensive research into achieving the above-mentioned object, the inventors discovered that the above-mentioned object can be achieved by using a preform made by arranging tape substrates made of carbon fiber bundles in their width direction, stacking them in their thickness direction, and then shaping them, and by arranging the tape substrates with gaps between them when producing this preform, thereby completing the present invention.

[0007] That is, the method for producing a fiber-reinforced plastic molded product of the present invention is to impregnate and harden a thermosetting resin material into a preform made by arranging tape substrates made of carbon fiber bundles in the width direction and stacking them in the thickness direction, and then shaping the preform, and the fiber volume content (V f In this method for producing a fiber-reinforced plastic molded product, when producing a preform, the tape base materials are arranged with gaps between them. Also, The molding die comprises a fixed die and a movable die, the movable die has a resin injection port, and when the tape substrates constituting the surface of the preform located on the resin injection port side are arranged, no gaps are provided between the tape substrates within the area from the position of the resin injection port to its vicinity in a direction perpendicular to the moving direction of the movable die. [Effects of the Invention]

[0008] According to the present invention, a preform is used in which tape substrates made of carbon fiber bundles are aligned in the width direction, stacked in the thickness direction, and then shaped, and when this preform is produced, the tape substrates are aligned with gaps between them, thereby providing a method for producing fiber-reinforced plastic molded products that reduces the amount of carbon fiber waste and can improve productivity while ensuring the mechanical strength of the molded product. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a flow diagram showing one embodiment of a method for producing a fiber-reinforced resin molded product of the present invention. [Figure 2] 2(A) to 2(F) are plan views schematically showing some examples of sheet-like substrates. [Figure 3] 3(A) and 3(B) are exploded perspective views schematically showing an example and another example of the laminated base material. [Figure 4] 4(A) and 4(B) are a plan view and a cross-sectional view schematically showing an example of a preform. [Figure 5] 1A to 1C are explanatory diagrams schematically illustrating a process for producing a molded product. [Figure 6] 1 is a graph showing the relationship between the gap between tape substrates and the fiber volume fraction (Vf). [Figure 7] 1 is a graph showing the relationship between the gap between tape substrates and compressive strength. [Figure 8] 1 is a graph showing the relationship between the gap between tape substrates and the tensile strength. DETAILED DESCRIPTION OF THE INVENTION

[0010] The method for producing a fiber-reinforced plastic molded article of the present invention will be described in detail below with reference to the drawings. Note that the dimensional proportions in the drawings cited below are exaggerated for the sake of explanation and may differ from the actual proportions.

[0011] As shown in FIG. 1, the method for producing a fiber-reinforced plastic molded article of this embodiment includes a preform production step S1 and a molded article production step S2.

[0012] <Preform manufacturing process S1> The preform manufacturing process S1 includes a sheet-like substrate manufacturing process S11, a laminated substrate manufacturing process S12, and a shaping process S 13. Each process will be described in more detail below.

[0013] (Sheet-shaped substrate preparation process S11) In the sheet-like substrate preparation step, as shown in Figures 2(A) to 2(E), tape substrates 15 made of carbon fiber bundles are arranged in the width direction to prepare a sheet-like substrate 13 for forming the pre-shaping laminated substrate 11 (11') (see Figure 3). When preparing the sheet-like substrate 13, the tape substrates 15 are arranged with gaps 15A between them.

[0014] Examples of the tape substrate 15 made of carbon fiber bundles include a tape-shaped carbon fiber bundle made by bundling continuous carbon fibers with thread and integrating them, and a tape-shaped carbon fiber bundle made by further bundling and integrating carbon fiber bundles with thread. The width of the tape substrate 15 is preferably, for example, 5 mm or more and 50 mm or less, and more preferably 5 mm or more and 25 mm or less. The thickness of the tape substrate 15 is preferably, for example, 0.1 mm or more and 0.5 mm or less. Furthermore, the tape substrate 15 preferably contains a binder such as an epoxy resin on the front and back sides thereof that can be used to fix the tape substrate to other tape substrates or molding dies, and the content of the binder is 5 g / m or less. 2 More than 15g / m 2 It is preferable that:

[0015] The width of the gap 15A is preferably 0.5 mm or more and 3 mm or less, and more preferably 0.5 mm or more and 2 mm or less.

[0016] When arranging the tape substrates 15, for example, when the longitudinal direction of the molded product is set to the 0° direction, it is preferable to appropriately use sheet-like substrates 13 in which the orientation of the tape substrate 15 is changed relative to the molded product, such as sheet-like substrates 131 and 134 in which the longitudinal direction of the tape substrate 15 is set to the 0° direction (see Figures 2(A) and (D)), sheet-like substrates 132 and 135 in which the longitudinal direction is set to the 45° direction (see Figures 2(B) and (E)), and sheet-like substrate 133 in which the longitudinal direction is set to the -45° direction (see Figure 2(C)).

[0017] Although only the narrow-width sheet-like substrate 134 is shown with the longitudinal direction of the tape substrate 15 set to the 0° direction (see Figure 2(D)), it is also possible to use tape substrates with the longitudinal direction set to the 45° or -45° direction as appropriate, similar to the wide-width sheet-like substrates 132 and 133 shown in Figures 2(B) and (C).

[0018] In this embodiment, when producing the sheet-like substrate 13 that is disposed on the resin injection port 33A side of the movable mold 33 for producing a molded product and that forms the surface of the preform 10, it is preferable that no gap 15A is provided between the tape substrates 15 in the region from the position of the resin injection port 33A to its vicinity in the direction perpendicular to the direction of movement of the movable mold 33 (see Figures 2(E), 4, and 5). Note that the perpendicular direction is the in-plane direction of the sheet-like substrate in Figure 2(E).

[0019] The distance from the position where the resin injection port 33A is disposed to the area nearby is preferably 50 mm or less.

[0020] Furthermore, a woven fabric or non-crimp fabric 136 made of carbon fiber may be provided as the sheet-like substrate 13 on the surface of the preform 10 on the side of the resin injection port 33A (see FIG. 2(F)).

[0021] In the sheet-like substrate production process, trimming may be carried out at the end.

[0022] (Laminated substrate manufacturing process S12) In the laminated substrate preparation step, for example, 19 sheets of sheet-like substrates 13 are stacked to prepare the laminated substrate 11 (11') before shaping (see FIG. 3). Although not shown, the gaps provided in each sheet-like substrate are preferably offset between the layers of the laminated substrate from the viewpoint of suppressing disorder of the tape substrate. On the other hand, the gaps provided in each sheet-like substrate are preferably aligned between the layers of the laminated substrate from the viewpoint of improving resin impregnation. A typical example of the gaps being offset is one in which the gaps are offset by half the width of the tape substrate.

[0023] Here, the laminated substrate 111 is formed by laminating a sheet-like substrate 133 on a sheet-like substrate 132. The laminated substrate 112 is formed by laminating eleven narrow sheet-like substrates. More specifically, six sheet-like substrates 134 are laminated, and tape substrates with orientations changed in the 45° direction and the −45° direction are laminated on top of these, and three sheet-like substrates 134 are further laminated on top of these. The laminated substrate 113 is formed by laminating four sheet-like substrates 131 and then laminating the sheet-like substrate 133 on top of these. When laminating the sheet-like substrates 13, it is preferable to integrate the tape substrates 15 constituting the sheet-like substrate 13 by changing the orientation as described above.

[0024] In the laminated substrate production process, trimming is preferably performed at the end from the viewpoint of facilitating positioning of the sheet-like substrate. Depending on the shape of the laminated substrate, trimming may be performed midway.

[0025] (Shaping process S13) In the shaping process, for example, the laminated substrate 11 is placed in a preform mold not shown, and is shaped by, for example, applying pressure to 25 kPa or more and 100 kPa or less using a press, and holding the pressure for 10 seconds or more and 60 seconds or less to produce a preform 10 (see Figure 4).

[0026] <Molded product production process S2> In the molded product manufacturing process, for example, it is preferable to use a high-pressure RTM molding method. Specifically, as shown in FIG. 5, a preform (not shown) is placed in a cavity 30A of a molding die 30, which includes a fixed die 31 and a movable die 33, and the movable die 33 has a resin column inlet 33A. Next, a thermosetting resin base 21 and a curing agent 23 are supplied under high pressure from a thermosetting resin base container 35 and a curing agent container 37, and a thermosetting resin material 20, which is a mixture of these, is supplied into the cavity 30A through a resin injection path 39 and a resin injection port 33A. Thereafter, the thermosetting resin material 20 is impregnated into and cured in a preform (not shown), thereby increasing the fiber volume content (V f ) is 45% or more and 52% or less. Such a fiber reinforced plastic molded product can be applied to, for example, a center pillar, which is an example of an automobile part. In FIG. 5, a resin column inlet 33A is provided at approximately the center of the movable mold 33 so that the thermosetting resin material 20 is uniformly impregnated and hardened.

[0027] Here, epoxy resin can be cited as a suitable example of the thermosetting resin. The viscosity of the thermosetting resin base is preferably, for example, 5000 mPa·s or more and 15000 mPa·s or less at 25°C. The injection pressure of the thermosetting resin base and the curing agent is preferably, for example, 8 MPa or more and 20 MPa or less. The injection speed of the thermosetting resin material is 80 cm 3 / s or more 200cm 3 The injection speed of the thermosetting resin base and the curing agent is preferably 78 cm / s or less, and the volume ratio of the thermosetting resin base and the curing agent is preferably 2.5 to 4:1. 3 / s, 22cm 3 / s is particularly preferable. The mold clamping force is preferably, for example, 250 tons or more and 300 tons or less. The mold gap amount is preferably, for example, 2.5 mm or more and 3.5 mm or less. The degree of vacuum inside the mold is preferably, for example, 0.35 kPa or more and 0.55 kPa or less. The mold clamping holding time is preferably 30 seconds or more and 40 seconds or less.

[0028] Next, the advantages of this embodiment will be described. According to the method for producing a fiber reinforced plastic molded product of this embodiment, when producing a preform as described above, the tape substrates are arranged with gaps between them, and the fiber volume content (V f By setting the carbon fiber content to 45% or more and 52% or less, it is possible to reduce the amount of wasted carbon fiber, promote resin flow during resin impregnation, and further improve resin impregnation. This makes it possible to provide a method for producing fiber-reinforced plastic molded products that can reduce the amount of carbon fiber waste, ensure the mechanical strength of the molded product, and improve productivity. Furthermore, improved resin impregnation has the secondary benefit of reducing the required mold clamping force and allowing the press to be made smaller.

[0029] According to this embodiment, by setting the width of the gap to 0.5 mm or more and 3 mm or less, in addition to the above-mentioned advantages, there is an advantage that the compressive strength can be reliably ensured.

[0030] According to this embodiment, by setting the width of the gap to 0.5 mm or more and 2 mm or less, in addition to the above-mentioned advantages, there is an advantage that the compressive strength and tensile strength can be reliably ensured.

[0031] According to this embodiment, by not providing gaps between the tape substrates in the region from the location of the resin injection port to its vicinity, in addition to the above-mentioned advantages, it is possible to suppress disturbance of the tape substrates in the vicinity of the resin injection port, thereby suppressing a decrease in mechanical strength.

[0032] According to this embodiment, by setting the distance from the resin injection port to the surrounding area to 50 mm or less, in addition to the above-mentioned advantages, mechanical strength can be reliably ensured. Another secondary advantage is that a preform can be produced using only a tape substrate without using a woven fabric or non-crimp fabric.

[0033] According to this embodiment, by providing a carbon fiber woven fabric or non-crimp fabric on the surface of the preform on the resin injection inlet side, in addition to the above-mentioned advantages, it is possible to suppress the disorder of the tape substrate, thereby suppressing the decrease in mechanical strength. [Example]

[0034] The present invention will now be described in more detail with reference to some test examples.

[0035] (Test Examples 1 to 9) Tape substrates (width: 25 mm, thickness: 0.33 mm) made of carbon fiber bundles were arranged with gaps between the tape substrates of −2.5 mm to 10 mm to obtain sheet-like substrates (see FIG. 2).

[0036] Next, eight of the obtained sheet-like substrates were stacked to obtain the laminated substrate of each example. The orientation directions of the tape substrates of each sheet-like substrate in the laminated substrate of each example were -45° / 45° / 0° / 0° / 0° / 0° / 45° / -45° (see Figure 3). The gaps between the sheet-like substrates consisting of tape substrates with the same orientation direction were uniform.

[0037] Furthermore, the obtained laminated substrate of each example was placed on a flat plate mold, and a pressure of 50 kPa was applied by pressing, and the pressure was maintained for 30 seconds, thereby obtaining a preform of each example.

[0038] The resulting preform was then placed in the cavity of a mold equipped with a fixed and movable die, and the epoxy resin material was impregnated and cured to obtain the fiber-reinforced resin molded product of each example (see Figure 5). Note that a gap of -2.5 mm means that the tape substrate was overlapped by 2.5 mm.

[0039] Here, the viscosity of the epoxy resin base is 10,000 mPa·s at 25°C. The injection pressure of the epoxy resin base and hardener is 10 MPa. Furthermore, the injection speed of the epoxy resin base and hardener is 78 cm 3 / s, 22cm 3 / s. The mold clamping force is 275 tons. The mold gap is 3 mm. The degree of vacuum inside the mold is 0.45 kPa. The mold clamping holding time is 35 seconds. The molding temperature of both the fixed mold and the movable mold is 120°C.

[0040] In each of the above test examples (except for the case where the gap was -2.5 mm), the resin flow during resin impregnation was promoted, and the resin impregnation was improved. As a result, these manufacturing methods were able to reduce the amount of carbon fiber waste and improve productivity while maintaining the mechanical strength of the fiber-reinforced resin molded product. On the other hand, in the test example where the gap was -2.5 mm, poor resin impregnation was observed.

[0041] < Fiber volume content (V f ) Measurement A sample was cut from the relatively inner part of each fiber-reinforced resin molded product, and the fiber volume content (V f ) was measured and calculated.

[0042] From Figure 6, the gap between the tape substrates and the fiber volume content (V f ) is correlated with the calculated value. In particular, when the tape substrate width is 25 mm, the experimental value and the calculated value are almost the same. When the tape substrate width is 25 mm or less, the fiber volume content (V f In order to make the fiber volume content (V) 45% or more and 52% or less, it is preferable to make the width of the gap narrower than when the width of the tape substrate is 25 mm. f The gap width can be slightly increased to make the ratio 45% to 52%. For example, if the tape substrate width is 50 mm, the gap width can be increased to about 7 mm.

[0043] <Compression strength measurement> A sample was cut out from a relatively inner portion of a fiber-reinforced resin molded product produced by the same manufacturing method as the fiber-reinforced resin molded product of each of the above-mentioned examples, and the compressive strength in the 0° direction was measured and calculated in accordance with JIS K 7076.

[0044] From FIG. 7, it was found that, from the viewpoint of ensuring a compressive strength of 350 MPa or more, the width of the gap between the tape substrates is preferably 0.5 mm or more and 3 mm or less.

[0045] <Measurement of tensile strength> A sample was cut out from a relatively inner portion of a fiber-reinforced resin molded product produced by the same manufacturing method as the fiber-reinforced resin molded product of each of the above-mentioned examples, and the tensile strength in the 0° direction was measured and calculated in accordance with JIS K 7073.

[0046] 7 and 8, it is clear that from the viewpoint of ensuring a compressive strength of 350 MPa or more and a tensile strength of 750 MPa or more, the width of the gap between the tape substrates is preferably 0.5 mm or more and 3 mm or less. Furthermore, from the viewpoint of ensuring a compressive strength of 350 MPa or more and a tensile strength of 1200 MPa or more, it is clear that from the viewpoint of ensuring a compressive strength of 350 MPa or more and a tensile strength of 1200 MPa or more, the width of the gap between the tape substrates is preferably 0.5 mm or more and 2 mm or less.

[0047] Although the present invention has been described above with reference to one embodiment and some test examples, the present invention is not limited to these and various modifications are possible within the scope of the gist of the present invention.

[0048] For example, in the above-described embodiment, an example was given in which tape substrates were arranged to first produce a sheet-like substrate, and then these were stacked to produce a laminated substrate, but a laminated substrate may also be produced by arranging tape substrates and stacking them.

[0049] Furthermore, for example, in the above-described embodiment, an example was given in which the molding mold includes a fixed mold and a movable mold, and the movable mold has a resin column inlet, but the shape of the molding mold can also be changed appropriately depending on the shape of the fiber-reinforced resin molded product. [Explanation of symbols]

[0050] 1 Fiber-reinforced plastic moldings 10 Preform 11,11',111,112,113 Laminated base material 13,131,132,133,134,135,136 Sheet substrate 15 Tape substrate 15A Gap 20 Thermosetting resin materials 21 Thermosetting resin base 23 Hardener 30 mold 30A cavity 31 Fixed type 33 Movable type 33A Resin inlet 35 Thermosetting resin base container 37 Hardener container 39 Resin injection path

Claims

1. A preform is made by arranging tape substrates made of carbon fiber bundles in the cavity of a mold, arranging them in the width direction, stacking them in the thickness direction, and shaping them. The preform is then impregnated with a thermosetting resin material and hardened. The fiber volume content (V ｆ ) is 45% or more and 52% or less, When preparing the preform, the tape substrates are arranged with gaps between them, the mold comprises a fixed mold and a movable mold, the movable mold has a resin injection port, When arranging the tape substrates constituting the surface of the preform located on the resin injection port side, no gaps are provided between the tape substrates in the region from the position of the resin injection port to its vicinity in the direction perpendicular to the moving direction of the movable mold. A method for producing a fiber-reinforced resin molded product, comprising:

2. 2. The method for manufacturing a fiber-reinforced resin molded product according to claim 1, wherein the width of the gap is 0.5 mm or more and 3 mm or less.

3. 2. The method for manufacturing a fiber-reinforced resin molded product according to claim 1, wherein the width of the gap is 0.5 mm or more and 2 mm or less.

4. A method for manufacturing a fiber-reinforced resin molded product as described in claim 1, characterized in that the distance from the location of the resin injection port to its surrounding area is 50 mm or less.

5. The molding die comprises a fixed die and a movable die, the movable mold has a resin injection port, A woven fabric or a non-crimp fabric made of carbon fiber is provided on the surface of the preform on the resin injection port side.

4. The method for producing a fiber-reinforced resin molded product according to claim 1.

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