Manufacturing method for fiber-reinforced sheet

Abstract

To provide a method for manufacturing fiber-reinforced sheets that can effectively utilize sheet materials such as prepreg sheets and reinforcing fibers, and that does not generate end materials.SOLUTION: The method for manufacturing a fiber-reinforced sheet has a cutting step for cutting a sheet material in a molded product shape from a sheet material formed of continuous fibers, a shredding step for shredding end materials of the sheet material cut out of the above molded product shape, and a placing step for placing the end materials shredded in the above shredding step on the above molded product-shaped sheet material. This enables effective utilization of sheet materials such as prepreg sheets and reinforcing fibers, and provides a method for manufacturing fiber-reinforced sheets in which end materials are not generated.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a fiber-reinforced sheet, and more specifically, to a method for manufacturing a fiber-reinforced sheet cut into a molded product shape at a preliminary stage in which the fiber-reinforced sheet is combined with resin to be molded into a fiber-reinforced resin molded product. [Background technology]

[0002] Fiber-reinforced plastic molded products are lighter and stronger than steel components, so they are used in a wide range of fields, including automobiles and aerospace.

[0003] The fiber-reinforced plastic molded products are generally formed by placing a sheet material, such as a prepreg in which resin has been pre-impregnated between the fibers or reinforcing fibers that have not yet been impregnated with resin, in a mold, adding resin as necessary, and heating and pressurizing the mold to harden the resin impregnated between the fibers, and the sheet material is then cut into the shape of the molded product for use.

[0004] Therefore, when producing fiber-reinforced plastic molded products, scraps of the above-mentioned sheet material are inevitably generated, and in order to reduce the environmental load by reducing CO2 emitted from the production of fiber-reinforced plastic molded products and to reduce costs, it is desirable to make effective use of the above-mentioned scraps.

[0005] Although it does not utilize scraps of the above-mentioned sheet materials, Patent Document 1 describes a method for producing a fiber-reinforced thermoplastic resin sheet having random fiber directions by scattering small pieces of unidirectional prepreg, and this production method makes it possible to utilize the above-mentioned scraps. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 7083544 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the manufacturing method described in Patent Document 1 involves allowing small pieces of prepreg to fall freely to produce a fiber-reinforced thermoplastic resin sheet with random fiber orientation, and the small pieces are not arranged in the shape of a molded article. As a result, the pieces need to be cut into the shape of the molded article, which ultimately results in waste material.

[0008] The present invention has been made in consideration of the problems associated with such conventional techniques, and an object of the present invention is to provide a method for producing a fiber-reinforced sheet that does not produce waste material and can effectively utilize sheet materials such as prepreg sheets and reinforcing fibers. [Means for solving the problem]

[0009] As a result of extensive research into achieving the above-mentioned object, the inventors discovered that the above-mentioned object can be achieved by placing scraps generated when cutting out a sheet material into a molded product shape on the cut-out sheet material into the molded product shape, and laminating the sheet material into the molded product shape and the scraps, thereby completing the present invention.

[0010] That is, the method for producing the fiber-reinforced sheet of the present invention is as follows: a cutting process for cutting out a sheet material having a shape of a molded product from a sheet material formed of continuous fibers; a shredding step of shredding the scraps of the sheet material cut into the shape of the molded product; The method further comprises a step of arranging and stacking the scraps chopped in the chopping step on the sheet material having the shape of the molded product. Effect of the Invention

[0011] According to the present invention, scraps generated when cutting out a sheet material into a molded product shape are placed on the cut-out sheet material into the molded product shape, and the sheet material into the molded product shape and the scraps are laminated together. This makes it possible to provide a method for manufacturing a fiber-reinforced sheet that does not generate scraps and can effectively utilize prepreg sheets and reinforcing fiber sheet materials. [Brief description of the drawings]

[0012] [Figure 1] FIG. 13 is a diagram illustrating a cutting process, a shredding process, and a placement process. [Diagram 2] 1A and 1B are diagrams illustrating a state in which a small piece of scrap material is placed on a sheet material having a molded product shape, and further a sheet material having a molded product shape is laminated thereon. [Diagram 3] 1 is a graph showing the relationship between the orientation direction of fibers and the flexural modulus. [Figure 4] 1 is a graph showing the relationship between the stacking position of the rectangular pieces and the flexural modulus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The method for producing the fiber-reinforced sheet of the present invention will now be described in detail. The method for manufacturing a fiber-reinforced sheet of the present invention includes a cutting process for cutting out a sheet material in the shape of a molded product from a sheet material formed of continuous fibers, a shredding process for shredding scraps of the sheet material into small pieces, and an arrangement process for arranging and stacking the scraps on the sheet material in the shape of the molded product.

[0014] The method for producing a fiber-reinforced sheet of the present invention involves chopping scraps of sheet material cut into the shape of a molded product into small pieces in a shredding process, and then arranging and stacking the small pieces on the sheet material in the shape of the molded product in an arrangement process, and utilizing the scraps produced in the cutting process as part of the fiber-reinforced sheet.As a result, no scraps are produced and the sheet material can be effectively used without being left over.

[0015] The above-mentioned method for producing a fiber-reinforced sheet can be carried out using a twin-head cutting plotter having two heads, as shown in Figs.

[0016] The cutting plotter head has a head that can move in four axes - front-to-back, left-to-right, up-down and rotation - relative to the sheet material to be cut, and moves to trace the outline of the graphic based on the input graphic data, cutting the sheet with a cutting blade attached to the head.

[0017] In the present invention, a cutting plotter is used in which a cutting blade is attached to the head 4 on the upstream side and a suction pad is attached to the head 5 on the downstream side instead of the cutting blade.

[0018] Specifically, as shown in the upper part of Figure 1, a sheet material 1 formed from continuous fibers is placed on a cutting table equipped with a conveyor belt 7, and the sheet material 2 in the shape of a molded product is cut out by an upstream head 4 equipped with a cutting blade (cutting process), and the remaining scraps of the sheet material are finely shredded into small pieces 3 (shredding process).

[0019] In the shredding process, it is preferable to shred the scraps into small rectangular pieces 3, except for the vicinity of the sheet material 2 in the shape of a molded product. When shredding the scraps into rectangular pieces, the cutting direction is uniform and the head can be moved linearly, making shredding easy and improving production efficiency.

[0020] Then, as shown in the middle and bottom diagrams of Figure 1, the sheet material 2 in the shape of the molded product and the chopped pieces 3 are transported by a conveyor belt 7, and the pieces 3 are lifted up one by one by a suction pad attached to the downstream head 5, and placed on the sheet material 2 in the shape of the molded product (placement process).

[0021] The cutting plotter head can move in four directions as described above, so by attaching a suction pad, it is not only possible to position the small pieces in the desired position, but also to position the small pieces 3 with the fibers oriented in the desired direction.

[0022] For example, the fibers can be oriented in the same direction, or at angles of 0°, 45°, or 90°, or even randomly.

[0023] In this way, by using a twin-head cutting plotter, the entire process from cutting to placement of the sheet material can be carried out using a single cutting device, eliminating the need for new capital investment to layer scrap material onto the sheet material in the shape of a molded product, and also eliminating the need to secure space for arranging the equipment.

[0024] In the method for producing the fiber-reinforced sheet of the present invention, as shown in the lower diagram of Figure 2, the above-mentioned arrangement step preferably includes a process of further arranging the above-mentioned molded product-shaped sheet material 2 on a small piece of scrap material 3 arranged on the above-mentioned molded product-shaped sheet material 2.

[0025] As a result, the layers formed from the chopped scraps are sandwiched between the sheets of the molded product, making it difficult for the scrap pieces to shift, and improving the strength of the fiber-reinforced resin molded product produced in the subsequent process. The stacking of the sheets of the molded product can be performed by a handling robot 6.

[0026] In addition, when cutting out the second and subsequent sheets of sheet material in the shape of a molded product to be layered on top of the scrap pieces from the sheet material formed from continuous fibers, scraps of sheet material are generated. These scraps can also be chopped into small pieces and placed alongside the small pieces previously placed on the first sheet material in the shape of a molded product, allowing the sheet material to be used without being wasted.

[0027] In addition, when arranging the small pieces in the above-mentioned arrangement process, the weight of the material per unit area (g / m 2 It is preferable to arrange the small pieces so that the basis weight of the pieces arranged on the sheet material is 70% or more of the basis weight of the sheet material. As shown in the upper and middle figures of Figure 2, the small pieces may be arranged uniformly without sparseness or density all the way to the edge of the sheet material in the shape of a molded product, covering 70% or more of the sheet material in the shape of a molded product, and the fiber directions of the small pieces may be aligned in the same direction.

[0028] In this way, by making the thickness of the layer formed from small pieces of scrap material and the orientation of the fibers uniform, it is possible to produce high-strength fiber-reinforced plastic molded products.

[0029] The amount of small pieces produced in the shredding process can be adjusted depending on the size of the sheet material formed from continuous fibers from which the sheet material in the shape of the molded product is cut. If there are not enough small pieces, the sheet material formed from the continuous fibers may be shredded as is to produce small pieces.

[0030] That is, prior to the cutting process, a rough cutting process is carried out in which a long piece of sheet material formed from continuous fibers is cut out into pieces of sheet material larger than the shape of the molded product to be used in the cutting process. By cutting out the sheet material in a size corresponding to the amount of pieces required to cover the sheet material in the shape of the molded product, it is possible to obtain just the right amount of pieces.

[0031] In addition, in the rough cutting process, the sheet material of the size required in the cutting process is cut out, and in the arrangement process, further sheet material of a size corresponding to the amount of pieces that are lacking is cut out, and the pieces resulting from both sheet materials can be used together.

[0032] The sheet material made of continuous fibers used in the present invention can be UD material (unidirectional material), NCF material (two sheets of UD material laminated with different fiber directions and fixed with stitch thread), or woven fabric. Examples of materials constituting the sheet material include carbon fiber, glass fiber, aramid fiber, flax fiber, and kenaf. EXAMPLES

[0033] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples.

[0034] [Experimental Example 1] A fiber-reinforced plastic molded product was produced using the following seven-layer fiber-reinforced sheet, which was made of NFC material (0 / 90) and a layer of 2.7 mm thick in which small rectangular pieces of 25 x 50 mm made from the NFC material's scraps were arranged without gaps, and the relationship between the fiber orientation direction and the flexural modulus was investigated. The evaluation results are shown in Figure 3.

[0035] A: [0 / Tabs / 60 / Tabs / 60 / Tabs / 0] (The fiber direction of the strip is oriented at 0° to the longitudinal direction of the test piece (perpendicular to the bending line)) B: [0 / Tabs / 60 / Tabs / 60 / Tabs / 0] (The fiber direction of the strips is randomly oriented relative to the longitudinal direction of the specimen) C: [0 / Tabs / 60 / Tabs / 60 / Tabs / 0] (The fiber direction of the strip is oriented at 90° to the longitudinal direction of the test piece (parallel to the bending line)) D: [0 / 30 / 60 / 90 / 60 / 30 / 0] (Continuous substrate only)

[0036] The results of Experimental Example 1 show that by arranging the small rectangular pieces so that their fibers are oriented in the same direction as the longitudinal direction of the fiber-reinforced plastic molded product (the direction perpendicular to the bending line), the flexural modulus is improved, and that by orienting them randomly, a flexural modulus equivalent to that of a fiber-reinforced plastic molded product formed using only NCF material can be obtained.

[0037] [Experimental Example 2] A fiber-reinforced plastic molded product was produced using the following four-layer fiber-reinforced sheet, which was made of NCF material (0 / 90) and a 1.7 mm thick layer of 25 x 50 mm rectangular pieces made from its scraps, arranged randomly with no gaps between them. A rectangular test piece with the longitudinal direction at 45° (bending line at -45°) was cut out, and the relationship between the stacking position of the rectangular pieces and the bending modulus was investigated. The evaluation results are shown in Figure 4.

[0038] F: [(45), (0), (90), (-45)] (Continuous substrate only) G: [(45), (0), strip, (-45)] (Inner layer of the strip) H: [Tanzaku, (0), (90), (-45)] (Outer layer of strip) I: [(45), (0), (90), strip] (Outer layer of strip)

[0039] From the results of Experimental Example 2, it is clear that by stacking the rectangular pieces in the middle of the plate thickness direction, a fiber-reinforced plastic molded product with a high flexural modulus can be obtained. This is because it is generally believed that bending loads are applied to the outside of the plate and that loads applied to the inside of the plate are low. Therefore, by stacking rectangular material with lower rigidity than continuous fibers in the center of the plate thickness, it is possible to obtain rigidity equivalent to that of an all-continuous fiber molded product. [Explanation of symbols]

[0040] 1 Sheet material (long roll) 2 Sheet material cut into the shape of the molded product 3. Small pieces of chopped scrap wood 4. Upstream head 5 Downstream head 6 Handling robot 7 Conveyor belt

Claims

1. a cutting process for cutting out a sheet material having a shape of a molded product from a sheet material formed of continuous fibers; a shredding step of shredding the scraps of the sheet material cut into the shape of the molded product into small pieces; and an arrangement step of arranging and stacking the scraps chopped in the chopping step on the sheet material having the molded product shape.

2. Using a twin-head cutting plotter with a cutting blade attached to one head and a suction pad attached to the other head, The cutting step and the shredding step are carried out by a head equipped with a cutting blade, 2. The method for manufacturing a fiber-reinforced sheet according to claim 1, wherein the positioning step is performed by using a head equipped with a suction pad.

3. The method for producing a fiber-reinforced sheet according to claim 1, characterized in that the cutting step includes cutting the end material of the sheet material into small rectangular pieces.

4. The method for manufacturing a fiber-reinforced sheet according to claim 1, characterized in that the placing step includes a process of placing a further sheet material having the shape of a molded product on an end material placed on the sheet material having the shape of a molded product.

5. 2. The method for manufacturing a fiber-reinforced sheet according to claim 1, wherein the arranging step includes a process of arranging the small pieces so that the basis weight of the small pieces arranged on the sheet material is 70% or more of the basis weight of the sheet material.

6. The sheet material is a long material, A rough cutting process is performed before the cutting process, in which a sheet material larger than the shape of the molded product is cut out from the long material, The method for manufacturing a fiber-reinforced sheet according to claim 5, characterized in that the rough cutting step cuts out the sheet material to a size corresponding to the amount of the small pieces required to cover the sheet material in the shape of the molded product.

7. The sheet material is a long material, A rough cutting process is performed before the cutting process, in which a sheet material larger than the shape of the molded product is cut out from the long material, The rough cutting step includes a process of cutting out the sheet material of a size required in the cutting step, and a process of cutting out sheet material of a size corresponding to an amount of the small pieces that is insufficient to cover the sheet material of the molded product shape from the long material, The method for producing a fiber-reinforced sheet according to claim 5, wherein the shredding step includes a process of shredding both of the sheet materials cut out in the rough cutting step.

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