JP2023105450A - Method for producing fiber reinforced resin molded product - Google Patents

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

The present invention relates to a method for producing a fiber-reinforced resin molded product, and more particularly, a fiber-reinforced resin that can improve productivity while reducing the amount of carbon fiber waste and ensuring the mechanical strength of the molded product. The present invention relates to a method for manufacturing molded articles.

Conventionally, there have been proposals for molding methods for fiber-reinforced plastics that are lightweight, have high mechanical strength, can be easily trimmed while ensuring a good appearance, and have the strength of the outer peripheral portion equivalent to that of the central portion of the product. (See Patent Document 1.). This method of molding a fiber-reinforced plastic is a preform in which a second base material in which the reinforcing fibers are pre-impregnated with a resin is arranged on at least a part of the outer peripheral portion of the first base material made only of reinforcing fibers such as textiles. and after housing the preform in the cavity of the mold, the resin is injected and cured. In this molding method, an RTM (Resin Transfer Molding) molding method is used.

JP 2010-76356 A

However, when trying to further increase the thickness of the fiber-reinforced plastic as described in Patent Document 1, the portion of the woven fabric made of reinforcing fibers, that is, carbon fibers, becomes even thicker. There is a problem that there is a possibility that the mechanical strength may be reduced. In addition, if the resin impregnation takes time in order to prevent resin impregnation failure, there is a problem that productivity decreases. Furthermore, when fabrics made of carbon fibers are laminated and used, there is also the problem that the trimming allowance during preform construction tends to increase, resulting in a large amount of carbon fiber waste.

The present invention has been made in view of such problems of the prior art, and is a fiber that can improve productivity while reducing the amount of carbon fiber waste and ensuring the mechanical strength of the molded product. An object of the present invention is to provide a method for manufacturing a reinforced resin molded product.

As a result of intensive studies to achieve the above object, the inventors of the present invention used a preform formed by arranging tape substrates made of carbon fiber bundles in the width direction and laminating them in the thickness direction and shaping them, The present inventors have found that the above object can be achieved by arranging the tape substrates with a gap between them when producing this preform, and have completed the present invention.

That is, in the method for producing a fiber-reinforced resin molded product of the present invention, tape substrates made of carbon fiber bundles placed in a cavity of a mold are arranged in the width direction and laminated in the thickness direction, and shaped. A method for producing a fiber-reinforced resin molded article having a fiber volume content (V _f ) of 45% or more and 52% or less, which is obtained by impregnating and curing a thermosetting resin material in a preform produced by the above. In this method for producing a fiber-reinforced resin molded product, when the preform is produced, the tape substrates are arranged with a gap therebetween.

According to the present invention, when using a preform obtained by arranging tape base materials made of carbon fiber bundles in the width direction and laminating them in the thickness direction and shaping the preform, when producing this preform, the tape base material is Since the carbon fibers are arranged with a gap between them, it is possible to provide a method for manufacturing a fiber-reinforced resin molded product that can improve productivity while reducing the amount of carbon fiber waste and ensuring the mechanical strength of the molded product.

BRIEF DESCRIPTION OF THE DRAWINGS It is a flowchart which shows one Embodiment of the manufacturing method of the fiber reinforced resin molding of this invention. FIGS. 2A to 2F are plan views schematically showing some examples of sheet-like substrates. FIGS. 3A and 3B are exploded perspective views schematically showing one example and another example of the laminated substrate. 4A and 4B are a plan view and a cross-sectional view schematically showing an example of a preform. It is explanatory drawing which shows the point of a molded article production process typically. 1 is a graph showing the relationship between the gap between tape substrates and fiber volume fraction (V _f ). 4 is a graph showing the relationship between the gap between tape substrates and compressive strength. 4 is a graph showing the relationship between the gap between tape substrates and tensile strength.

Hereinafter, the method for producing a fiber-reinforced resin molded product of the present invention will be described in detail with reference to the drawings. Note that the dimensional ratios in the drawings quoted below are exaggerated for convenience of explanation, and may differ from the actual ratios.

As shown in FIG. 1, the method for manufacturing a fiber-reinforced resin molded product according to this embodiment includes a preform manufacturing step S1 and a molded product manufacturing step S2.

<Preform manufacturing step S1>
The preform manufacturing process S1 includes a sheet-like base material manufacturing process S11, a laminated base material manufacturing process S12, and a shaping process S13. Each step will be described in more detail below.

(Sheet-like base material preparation step S11)
In the sheet-shaped base material production process, as shown in FIGS. 2A to 2E, tape base materials 15 made of carbon fiber bundles are arranged in the width direction to form a laminated base material 11 (11′) before shaping. (see FIG. 3) is produced. When the sheet-shaped base material 13 is produced, the tape base materials 15 are arranged with a gap 15A between them.

Here, as the tape substrate 15 made of a carbon fiber bundle, for example, a carbon fiber bundle formed by bundling carbon fibers made of continuous fibers with a thread and integrated into a tape shape, or a carbon fiber bundle further bundled with a thread. can be exemplified as a tape-like material formed by integrating the tape. The width of the tape substrate 15 is, for example, preferably 5 mm or more and 50 mm or less, more preferably 5 mm or more and 25 mm or less. Moreover, it is preferable that the thickness of the tape base material 15 is, for example, 0.1 mm or more and 0.5 mm or less. Furthermore, the tape base 15 preferably contains a binder such as an epoxy resin that can be used for fixing to other tape bases or molds on the front side and back side, and the content is 5 g/m. It is preferably ² or more and 15 g/m ² or less.

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.

When arranging the tape substrates 15, for example, when the longitudinal direction of the molded product is the direction of 0°, the sheet-like substrates 131 and 134 (see FIG. 2 ( A) and (D)), sheet-like substrates 132 and 135 in the direction of 45° (see FIGS. 2B and 2E), sheet-like substrate 133 in the direction of −45° (see FIG. 2C )), it is preferable to appropriately use the sheet-like substrate 13 in which the orientation of the tape substrate 15 is changed with respect to the molded product.

As the sheet-like base material 134 having a narrow width, only the tape base material 15 whose longitudinal direction is 0° direction is shown (see FIG. 2(D)), but FIG. As with the wide-shaped sheet-like substrates 132 and 133 shown in (C), it is also possible to appropriately use tape substrates whose longitudinal direction is 45° or -45°.

In the present embodiment, when producing the sheet-like base material 13 which is arranged on the resin injection port 33A side of the movable mold 33 for producing a molded product and constitutes the surface of the preform 10, the movable direction of the movable mold 33 is In the direction orthogonal to , it is preferable not to provide a gap 15A between the tape substrates 15 in the region from the arrangement position of the resin injection port 33A to the vicinity thereof (Figs. 5). The orthogonal direction is the in-plane direction of the sheet-like substrate in FIG. 2(E).

It is preferable that the distance from the arrangement position of the resin injection port 33A to the neighboring area is 50 mm or less.

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

In addition, in the sheet-like base material production process, trimming may be performed at the end.

(Laminated substrate preparation step S12)
In the layered base material production step, for example, 19 sheet-like base materials 13 are laminated to produce a layered base material 11 (11') before shaping (see FIG. 3). In addition, although not shown, it is preferable that the gaps provided between the sheet-like base materials are shifted between the layers of the laminated base material from the viewpoint of suppressing disorder of the tape base material. On the other hand, from the viewpoint of improving resin impregnation, it is preferable that the gaps provided in each sheet-like base material are evenly provided between the layers of the laminated base material. A typical example of the staggered arrangement is the staggered arrangement by half the width of the tape substrate.

Here, the layered base material 111 is obtained by laminating a sheet-like base material 133 on a sheet-like base material 132 . Further, the laminated base material 112 is obtained by laminating eleven narrow sheet-like base materials. More specifically, six sheet-like substrates 134 are laminated, and tape substrates whose orientation is changed in the 45° direction and −45° direction are laminated, and three sheet-like substrates 134 are laminated. It is laminated. Further, the laminated base material 113 is obtained by laminating a sheet-like base material 133 on a laminate of four sheet-like base materials 131 . When laminating the sheet-shaped substrates 13, it is preferable to integrate them by changing the orientation of the tape substrates 15 constituting the sheet-shaped substrates 13 as described above.

In addition, in the layered base material production process, it is preferable to perform trimming at the end from the viewpoint of facilitating the positioning of the sheet-like base material. Further, depending on the shape of the laminated base material, trimming may be performed in the middle.

(Shaping step S13)
In the shaping step, for example, the laminated base material 11 is placed in a preform mold (not shown), for example, by pressing at a pressure of 25 kPa or more and 100 kPa or less and holding it for 10 seconds or more and 60 seconds or less to shape it. , to produce a preform 10 (see FIG. 4).

<Molded article production step S2>
It is preferable to use, for example, a high-pressure RTM molding method in the molded product manufacturing process. Specifically, as shown in FIG. 5, a fixed mold 31 and a movable mold 33 are provided, and the movable mold 33 places a preform (not shown) in a cavity 30A of the mold 30 having a resin column inlet 33A. Next, the thermosetting resin main agent 21 and the curing agent 23 are supplied from the thermosetting resin main agent container 35 and the curing agent container 37 under high pressure, and the thermosetting resin material 20, which is a mixture of these, is supplied to the resin injection path 39 and the resin injection path 39. Cavity 30A is fed through inlet 33A. After that, a preform (not shown) is impregnated with the thermosetting resin material 20 and cured to produce a fiber-reinforced resin molded product 1 having a fiber volume content (V _f ) of 45% or more and 52% or less. Such a fiber-reinforced resin molded product can be applied, for example, to a center pillar, which is an example of automobile parts. In FIG. 5, a resin column inlet 33A is provided substantially in the center of the movable mold 33 so that the thermosetting resin material 20 is evenly impregnated and cured.

Here, as a thermosetting resin, an epoxy resin can be given as a suitable example. The viscosity of the main thermosetting resin 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 main agent and curing agent is preferably, for example, 8 MPa or more and 20 MPa or less. The injection speed of the thermosetting resin material is preferably 80 cm ³ /s or more and 200 cm ³ /s or less, and the volume ratio of the thermosetting resin main agent and the curing agent is preferably 2.5 to 4:1. preferable. It is particularly preferable that the injection speeds of the main thermosetting resin and curing agent are, for example, 78 cm ³ /s and 22 cm ³ /s, respectively. The mold clamping force is preferably 250 tons or more and 300 tons or less, for example. It is preferable that the mold gap amount is, for example, 2.5 mm or more and 3.5 mm or less. The degree of vacuum in the mold is preferably, for example, 0.35 kPa or more and 0.55 kPa or less. The clamping holding time is preferably 30 seconds or more and 40 seconds or less.

Next, advantages of this embodiment will be described.
According to the method for producing a fiber-reinforced resin molded product of the present embodiment, when the preform is produced as described above, the tape substrates are arranged with a gap between them, and the fiber volume content of the fiber-reinforced resin molded product ( By setting V _f ) to 45% or more and 52% or less, waste carbon fibers can be reduced, resin flow during resin impregnation can be promoted, and resin impregnability can be improved. As a result, it is possible to provide a method for manufacturing a fiber-reinforced resin molded product that can reduce the amount of carbon fiber waste and improve productivity while ensuring the mechanical strength of the molded product. Furthermore, since resin impregnation is improved, there is a secondary advantage that the required mold clamping force can be reduced and the size of the press machine can be reduced.

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

According to the present embodiment, by setting the width of the above-described gap to 0.5 mm or more and 2 mm or less, in addition to the advantages described above, there is an advantage that the compressive strength and the tensile strength can be reliably secured.

According to this embodiment, in addition to the advantages described above, by not providing a gap between the tape substrates in the area from the position where the resin injection port is arranged to the vicinity thereof, resin injection can be achieved. Disturbance of the tape substrate near the entrance can be suppressed. Thereby, a decrease in mechanical strength can be suppressed.

According to this embodiment, by setting the distance from the resin injection port to the neighboring area to 50 mm or less, it is possible to ensure mechanical strength in addition to the advantages described above. It also has the side advantage of being able to make a preform from just the tape substrate without using a woven or non-crimped fabric.

According to this embodiment, by providing the surface of the preform on the side of the resin injection port with the woven fabric or non-crimp fabric made of carbon fiber, in addition to the advantages described above, it is possible to suppress the disturbance of the tape base material. This makes it possible to suppress a decrease in mechanical strength.

The present invention will now be described in more detail with some test examples.

(Test Examples 1 to 9)
A sheet-like substrate was obtained by arranging tape substrates (width: 25 mm, thickness: 0.33 mm) made of carbon fiber bundles with a gap between the tape substrates of −2.5 mm to 10 mm (see FIG. 2). ).

Next, eight sheets of the obtained sheet-like base material were laminated to obtain a laminated base material of each example. The orientation directions of the tape base material of each sheet-like base material in the laminated base material of each example are −45°/45°/0°/0°/0°/0°/45°/−45° (Fig. 3). The gaps between the sheet-like substrates made of the tape substrates having the same orientation direction were evenly spaced.

Furthermore, the obtained laminated base material of each example was placed on a flat plate and pressurized at 50 kPa for 30 seconds to obtain a preform of each example.

After that, the obtained preform was placed in a cavity of a mold equipped with a fixed mold and a movable mold, and impregnated with an epoxy resin material and cured to obtain a fiber-reinforced resin molded product of each example (Fig. 5 reference). The gap of -2.5 mm means that the tape substrates are overlapped by 2.5 mm.

Here, the viscosity of the epoxy resin main agent is 10000 mPa·s at 25°C. The injection pressure of the epoxy resin main agent and curing agent is 10 MPa. Furthermore, the injection speeds of the epoxy resin main agent and curing agent are 78 cm ³ /s and 22 cm ³ /s, respectively. The mold clamping force is 275 tons. The mold gap amount is 3 mm. The degree of vacuum in the mold is 0.45 kPa. The clamp holding time is 35 seconds. The mold temperatures of the stationary mold and the movable mold are both 120°C.

In each of the test examples described above (excluding the case where the gap was -2.5 mm), the resin flow during resin impregnation could be promoted, and the resin impregnation property could be improved. As a result, in these manufacturing methods, the amount of carbon fiber waste can be reduced, and productivity can be improved while ensuring the mechanical strength of the fiber-reinforced resin molded product. On the other hand, in the test example in which the gap was -2.5 mm, poor resin impregnation was observed.

<Measurement of Fiber Volume Content (V _f )>
A sample was cut out from the relatively inside of the fiber-reinforced resin molded product of each example, and the fiber volume content (V _f ) was measured and calculated by the combustion method.

From FIG. 6, there is a correlation between the gap between the tape substrates and the fiber volume fraction (V _f ). In particular, when the width of the tape base material is 25 mm, it was found that the experimental value and the calculated value substantially match. When the width of the tape substrate is 25 mm or less, it is preferable to make the width of the gap narrower than when the width of the tape substrate is 25 mm so that the fiber volume fraction (V _f ) is 45% or more and 52% or less. Moreover, when the width of the tape base material is more than 25 mm, the width of the gap can be slightly widened in order to make the fiber volume fraction (V _f ) 45% or more and 52% or less. For example, when the width of the tape substrate is 50 mm, the width of the gap can be increased to about 7 mm.

<Measurement of compressive strength>
A sample was cut out from the relatively inside of the fiber-reinforced resin molded product manufactured by the same manufacturing method as the fiber-reinforced resin molded product of each example described above, and the compressive strength in the 0° direction was measured in accordance with JIS K 7076. , was calculated.

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

<Measurement of tensile strength>
A sample was cut out from the relatively inside of the fiber-reinforced resin molded product produced by the same manufacturing method as the fiber-reinforced resin molded product of each example described above, and the tensile strength in the 0 ° direction was measured according to JIS K 7073. , was calculated.

7 and 8, from the viewpoint of ensuring a compressive strength of 350 MPa or more and a tensile strength of 750 MPa or more, it is preferable that the width of the gap between the tape substrates is 0.5 mm or more and 3 mm or less. rice field. Furthermore, from FIGS. 7 and 8, 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. I found out.

As described above, the present invention has been described by one embodiment and some test examples, but the present invention is not limited to these, and various modifications are possible within the scope of the present invention.

For example, in the above-described embodiment, the tape base material is arranged to form a sheet-like base material, and then the sheet-like base material is laminated to prepare the laminated base material. A laminated base material may be produced by laminating the materials while arranging them.

Further, for example, in the above-described embodiments, the mold has a fixed mold and a movable mold, and the movable mold has a resin column inlet. Therefore, the shape of the mold can be changed as appropriate.

1 Fiber-reinforced resin molded article 10 Preforms 11, 11', 111, 112, 113 Laminated base material 13, 131, 132, 133, 134, 135, 136 Sheet-like base material 15 Tape base material 15A Gap 20 Thermosetting resin Material 21 Thermosetting resin main agent 23 Curing agent 30 Mold 30A Cavity 31 Fixed mold 33 Movable mold 33A Resin injection port 35 Thermosetting resin main agent container 37 Curing agent container 39 Resin injection path

Claims (6)

A thermosetting resin material is impregnated into a preform made by arranging carbon fiber bundle tape substrates in the width direction, laminating them in the thickness direction, and shaping them, placed in the cavity of the mold. - A method for producing a fiber-reinforced resin molded product obtained by curing and having a fiber volume content (V _f ) of 45% or more and 52% or less,
A method for producing a fiber-reinforced resin molded article, wherein the tape substrates are arranged with a gap therebetween when producing the preform. 2. The method for producing a fiber-reinforced resin molded article according to claim 1, wherein the width of said gap is 0.5 mm or more and 3 mm or less. 2. The method for producing a fiber-reinforced resin molded article according to claim 1, wherein the width of said gap is 0.5 mm or more and 2 mm or less. the mold comprises a fixed mold and a movable mold;
The movable mold has a resin injection port,
When arranging the tape base material constituting the surface of the preform positioned on the resin injection port side, within the area from the arrangement position of the resin injection port to the vicinity thereof in the direction orthogonal to the moving direction of the movable mold The method for producing a fiber-reinforced resin molded product according to any one of claims 1 to 3, wherein no gap is provided between the tape base materials. 5. The method for producing a fiber-reinforced resin molded product according to claim 4, wherein the distance from the position where the resin injection port is arranged to the area in the vicinity thereof is 50 mm or less. the mold comprises a fixed mold and a movable mold;
The movable mold has a resin injection port,
The method for producing a fiber-reinforced resin molded product according to any one of claims 1 to 3, wherein a woven fabric or non-crimped fabric made of carbon fiber is provided on the surface of the preform on the resin injection port side. .

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