Molding method and laminated structure

Abstract

It is possible to provide a molding method and a laminated structure that can suppress the occurrence of manufacturing defects and improve production technology. [Solution] This is a method for molding fiber-reinforced plastics by injecting resin into a mold (upper mold 10, lower mold 11) with a sheet-like fiber preform 2 placed inside, and molding the plastic. The method includes a lamination step in which fiber preforms 2 made of fibers are stacked in multiple layers inside the mold to form a laminate 3, an injection step in which resin is injected into the mold to impregnate it, and a removal step in which a molded product is removed from the mold after the resin has hardened. Each layer of the laminate 3 is made up of two or more fiber preforms 2, and in the outermost layer of the laminate 3, which is located on the outermost side, the joints 4 between adjacent fiber preforms 2 are arranged in a plane approximately perpendicular to the removal direction of the mold.

Description

[Technical Field]

[0001] The present invention relates to a method for molding a fiber-reinforced plastic product, for example, consisting of a laminate structure, and to the laminate structure. [Background technology]

[0002] Conventionally, a method for manufacturing fiber-reinforced plastic products consisting of a laminated structure has been proposed, in which a laminate formed by stacking fiber preforms made of preformed fibers is placed in a mold (molding die) that can be sealed, and resin is injected into the mold to impregnate the laminate.

[0003] For example, Patent Document 1 discloses that, in forming a fiber preform, the base material for a three-dimensional product is made of a sheet-like material in which multiple sheets are stacked, and the overlapping portions for sewing provided on the edges of this sheet-like material are sewn together to form a three-dimensional fiber preform.

[0004] In addition, in order to be able to accommodate a wide variety of product shapes, a technology has been proposed in which a fiber preform is divided into a plurality of sub-preforms, which are then combined to form a laminate, and products made from this laminate are manufactured.

[0005] However, in the conventional technology, when combining sub-preforms to form a laminate, there is a problem that the joints between the sub-preforms tend to get caught when fitting into the mold, which can easily cause defects in the manufacturing process. For this reason, there is a need to suppress the occurrence of manufacturing defects and improve production technology. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-182776 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a novel molding method and laminated structure that can suppress the occurrence of manufacturing defects and improve production technology. [Means for solving the problem]

[0008] The present invention is a method for molding fiber-reinforced plastics, in which resin is injected into a mold inside which a sheet-like fiber preform made of fiber is placed, and the method comprises a lamination step of stacking the fiber preforms in multiple layers in the thickness direction inside the mold to form a laminate, and an injection step of injecting resin into the mold to impregnate the laminate, each layer of the laminate being made of two or more fiber preforms, and the lamination step is characterized in that the joints between adjacent fiber preforms in the outermost layer located on the outside of the laminate are positioned in a plane approximately perpendicular to the mold-pulling direction of the mold.

[0009] The present invention also provides a laminated structure having a laminate in which sheet-like fiber preforms are stacked in multiple layers in the thickness direction, wherein each layer of the laminate is composed of two or more fiber preforms, and the joints between adjacent fiber preforms in the outermost layer located on the outermost side of the laminate are arranged in a plane approximately perpendicular to the molding direction of the molding die. [Effects of the Invention]

[0010] The present invention can provide a novel molding method and laminated structure that can suppress the occurrence of manufacturing defects and improve production technology. [Brief explanation of the drawings]

[0011] [Figure 1]1 is a flow diagram of a method for molding fiber reinforced plastic in one embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view showing an example of the configuration of an upper mold and a lower mold used in a molding method. [Figure 3] FIG. 10 is a perspective view showing a part of an example of a method for arranging a fiber preform in a lower mold. [Figure 4] FIG. 10 is a perspective view showing another part of an example of a method for arranging a fiber preform in a lower mold. [Figure 5] FIG. 10 is a perspective view showing another part of an example of a method for arranging a fiber preform in a lower mold. [Figure 6] 1 is a schematic cross-sectional view showing an example of the configuration of a fiber preform, a laminate, and a laminate structure. [Figure 7] 10A and 10B are schematic cross-sectional views showing other examples of the configuration of a fiber preform, a laminate, and a laminate structure. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention relates to a method for molding a resin product containing fiber (reinforced fiber) and a laminated structure, and to a laminated structure formed by integrating multiple layers of fiber preforms to form an integrated laminate, and a molded product (fiber reinforced plastic: FRP) formed by injecting resin into the laminated structure and curing the entire structure.

[0013] The molded article (fiber-reinforced plastic product) according to the present invention is formed by the resin transfer molding (RTM) method (hereinafter referred to as the "RTM method"), in which reinforcing fiber sheets are preformed by stacking them in the thickness direction, and then impregnating them with resin. The RTM method is a molding method in which a preformed laminated structure is placed in a mold, liquid resin is injected into it to impregnate it, and then the resin is cured naturally, or by heating or applying pressure. This method allows fiber-reinforced plastic products to be manufactured with high precision and efficiency. The structure of the molded article according to the present invention is obtained by such an RTM method.

[0014] The reinforcing fiber sheet used in the present invention is not particularly limited, and known ones can be used as appropriate. For example, reinforcing fiber sheets include carbon fiber sheets and glass fiber sheets. The type of these fibers is not particularly limited, but it is desirable to use ones that have the effect of improving strength when used as fiber-reinforced plastics.

[0015] FIG. 1 is a flow diagram of a method for molding fiber-reinforced plastics according to one embodiment of the present invention. An overall overview of the molding method of the present invention will be described with reference to FIG. 1. First, a gel coat is applied to the surface of a molding die (step S1). For example, in step S1, a predetermined amount of gel coat is applied to the surface of the molding die. The amount of gel coat applied is set appropriately depending on the size and shape of the molding die or molded body. For example, the amount of gel coat applied can be set so that the thickness of the gel coat after application is approximately 0.5 mm.

[0016] Next, a barrier coat is applied onto the gel coat layer (step S2). For example, in step S2, a predetermined amount of the barrier coat is applied to the surface of the mold. The amount of the barrier coat applied is set appropriately depending on the size and shape of the mold or molded body. For example, the amount of the barrier coat applied can be set so that the film thickness of the barrier coat after application is approximately 0.2 to 0.3 mm.

[0017] In steps S1 and S2, the thickness of each of the gel coat and the barrier coat may be checked after application (film thickness inspection).

[0018] Then, the sheet-like reinforcing fiber substrate (fiber substrate) is cut into a predetermined shape to produce a sheet-like fiber preform (step S3). In step S3, the fiber preform is cut into a shape that matches the installation position in the mold. Furthermore, multiple fiber preforms are produced for each installation position in the mold, and each fiber preform is assigned identifiable information (for example, a number, etc.).

[0019] Next, each fiber preform is placed at a predetermined installation position inside the mold (on the surface of the upper mold and / or lower mold) (step S4). In step S4, the fiber preforms are stacked in multiple layers in the thickness direction to form a laminate.

[0020] The number of layers to be stacked, the number of fiber preforms constituting each layer, the thickness of each fiber preform, and the bonding structure between adjacent fiber preforms are preset in each part of the laminate inside the mold. By appropriately arranging such laminates inside the mold, a laminate structure is formed.

[0021] Next, the upper and lower dies are fitted together (fitted), and the hoses necessary for injecting the resin are connected (step S5). In step S5, when the upper and lower dies are fitted together, the inside of the mold is evacuated to a predetermined vacuum pressure (intra-mold vacuum pressure).

[0022] Next, resin is injected into the mold (step S6). Examples of resins that can be injected into the mold in step S6 include unsaturated polyester resin, epoxy resin, vinyl ester resin, phenolic resin, polyurethane resin, polyamide resin, polyimide resin, and other similar resins. The most common types are unsaturated polyester resin, epoxy resin, and vinyl ester resin. Unsaturated polyester resin is easy to handle and inexpensive, making it widely used for general purposes such as automotive parts. Epoxy resin has high mechanical properties and heat resistance, making it suitable for aerospace applications and high-performance structural components. Vinyl ester resin has excellent corrosion resistance and mechanical properties, exhibiting performance comparable to that of epoxy resin, while being easy to handle.

[0023] In step S6, the discharge pressure from the injection machine is adjusted appropriately, and a hardener can be added to the resin injected into the mold as needed. The hardening time of the injected resin is also set according to the conditions at the time of injection.

[0024] Next, the molded body is cured (step S7). In step S7, the cured state is confirmed by touch and temperature measured with a predetermined measuring device, and curing can be considered complete after a predetermined time (for example, 120 minutes after curing) has passed. Known measuring devices such as a radiation thermometer, thermocouple, and dielectric sensor can be used as appropriate to measure the cured state. In step S7, the mold temperature and the time until demolding can also be confirmed.

[0025] Thereafter, the hardened molded body is released from the mold (step S8), and the released molded body is subjected to appropriate processing such as scribing, trimming, drilling holes, correction, and polishing (step S9).

[0026] The above molding method only describes the main steps, and other steps can be added. The details of each step can be changed without departing from the spirit of each step. For example, the mold surface can be checked before step S1. After step S9, the product's appearance can be inspected and its weight can be measured. Step S1 or S2 can be omitted depending on the product specifications.

[0027] In the present invention, a new process is adopted in step S4 from the viewpoint of suppressing the occurrence of manufacturing defects and improving production technology. In step S4 of the present invention, each fiber preform is layered in a new arrangement on the surface of the upper mold and / or the lower mold to form a laminate. The fiber preform layering method of the present invention is carried out based on a predetermined design (layup design) of the laminate or laminate structure.

[0028] Fig. 2 is a perspective view showing an example of the configuration of an upper mold 10 and a lower mold 11 used in the molding method. Fig. 3 is a perspective view showing a part of an example of a method for arranging a fiber preform 2 in the lower mold 11. Figs. 4 and 5 are perspective views showing other parts of an example of a method for arranging a fiber preform 2 in the lower mold 11 (steps subsequent to the previous figure).

[0029] 2, the molding method of the present invention uses an upper mold 10 and a lower mold 11. Since the shapes of the upper mold 10 and the lower mold 11 themselves are not essential to the present invention, for the sake of convenience, the description will be given using upper mold 10 and lower mold 11 with a simple shape (C-shaped cross section).

[0030] The lower mold 11 has a main space (cavity) for forming the outer shape of the product, and functions as a base for placing and holding the fiber preform 2. On the other hand, the upper mold 10 fits (fits) into the lower mold 11 to form an enclosed space, presses down the fiber preform 2, determines the thickness of the fiber preform 2 or the laminate 3, and has a role of controlling the resin flow by being provided with a resin injection port and an exhaust port.

[0031] In the present invention, when producing a molded body, fiber preforms 2 are placed in an upper mold 10 and a lower mold 11. Although the fiber preforms 2 can be stacked and placed in either the upper mold 10 or the lower mold 11, the following description of this embodiment will be given taking as an example a case where the fiber preforms 2 are stacked in the lower mold 11.

[0032] As shown in Figures 3 to 5, each fiber preform 2 is cut to a shape that matches the edge of each surface of the lower mold 11. That is, each fiber preform 2 is cut to match the shape (outline) of each surface of the corresponding lower mold 11, and a predetermined adhesive material (e.g., spray glue) is applied to the surface on which the fiber preform 2 is placed. Therefore, each surface of the lower mold 11 and the fiber preform 2 are bonded by the adhesive material. With this adhesive structure, each fiber preform 2 is fixed to each surface of the lower mold 11.

[0033] For example, as shown in Fig. 3, a first fiber preform 2A is first placed on one upper surface (the upper surface on the left side in Fig. 3) of the lower mold 11. Then, as shown in Fig. 4, a second fiber preform 2B is placed on an adjacent surface (connecting surface) adjacent to (connected to) the surface on which the first fiber preform 2A is placed.

[0034] Subsequent fiber preforms are sequentially placed on adjacent surfaces adjacent to the surface on which the previous fiber preform 2 was placed, following the same procedure. In the example shown in FIG. 5, the first to fifth fiber preforms 2A to 2E are placed in this order. These first to fifth fiber preforms 2A to 2E cover one surface of the lower mold 11 (the surface facing the upper mold 10). In other words, the first to fifth fiber preforms 2A to 2E form the layer closest to the lower mold 11. Each of the first to fifth fiber preforms 2A to 2E may be preformed into a three-dimensional shape, a flat sheet, or a predetermined shape. For example, the first to fifth fiber preforms 2A to 2E may be preformed or may be formed by manually placing fibers cut to an appropriate length directly into a mold without preforming.

[0035] Furthermore, in the joint 4, where adjacent fiber preforms 2 are joined, a woven material such as glass cloth or carbon cloth can be added to strengthen the joint 4. For example, a woven material such as glass cloth or carbon cloth with a thickness of approximately 0.2 to 0.5 mm can be added to the joint 4. The joint 4 is configured so that the ends of adjacent fiber preforms 2 abut (contact in a butt-jointed state) or so that the ends cross in the thickness direction and are joined (lapped) in the planar direction. In addition to the joint 4, a woven material such as glass cloth or carbon cloth can be added to areas where a decrease in strength is a concern or where a required strength must be ensured structurally.

[0036] Fig. 6 is a schematic cross-sectional view showing an example of the configuration of the fiber preform 2, the laminate 3, and the laminate structure 1. Fig. 7 is a schematic cross-sectional view showing another example of the configuration of the fiber preform 2, the laminate 3, and the laminate structure 1.

[0037] As shown in FIG. 6, a layer (second layer) 3B made of fiber preform 2 is formed on a layer (first layer) 3A made of fiber preform 2 and closest to the lower mold 11. Furthermore, as shown in FIG. 7, a layer (third layer) 3C made of fiber preform 2 is formed on the second layer 3B. In this manner, a plurality of layers (first layer 3A to third layer 3C in this embodiment) of fiber preform 2 are integrated to form an integrated laminate 3, and a laminate structure 1 made of this laminate 3 can be constructed. The method for bonding each layer can be a general method such as using a known adhesive material (e.g., spray glue), and is not particularly limited. Note that each layer of the laminate 3 is composed of two or more fiber preforms. Furthermore, although the example shown in FIG. 7 has a three-layer structure, the number of layers is not particularly limited as long as it is two or more layers.

[0038] As shown in Figures 6 and 7, in the laminated structure 1 of the present invention, the joints 4 between the ends of the fiber preforms 2 of each layer that form the laminate 3 are arranged at different positions when viewed from the mold removal direction of the molding mold (upper mold 10 and lower mold 11).

[0039] Specifically, the joints 4 between the ends of the fiber preforms 2 in one layer are positioned at different positions (in the extension direction of the fiber preforms 2) as viewed from the drawing direction of the molds (upper mold 10 and lower mold 11) relative to the joints 4 between the ends of the fiber preforms 2 in another layer. Therefore, in the laminate structure 1 (laminate 3), the joints 4 are not located at the same position in the planar direction in two or more consecutive layers (the positions of the joints 4 do not overlap in multiple layers), and weak points that make the multilayer fiber preform 2 prone to bending at the same position do not occur. Also, care can be taken to ensure that weak points in each layer do not overlap. Furthermore, misalignment and interference between the fibers in each layer can be prevented.

[0040] Here, the fiber preform 2 constituting the first layer (innermost layer) 3A can be referred to as a preform for the innermost layer, the fiber preform 2 constituting the second layer (intermediate layer) 3B can be referred to as a preform for the intermediate layer, and the fiber preform 2 constituting the third layer 3C can be referred to as a preform for the outermost layer.

[0041] In this embodiment, in the fiber preform 2 (preform for the outermost layer) constituting the third layer 3C, the joint 4 between adjacent fiber preforms 2 is arranged on a surface approximately perpendicular to the mold-pulling direction of the molding die (the opposing surfaces where the upper die 10 and the lower die 11 face each other when viewed from the mold-pulling direction).

[0042] Here, what is important in the configuration of the laminated structure 1 (laminate 3) is to design the laminated structure 1 (laminate 3) so that, when setting the position of the joint 4 in the outermost preform for the outermost layer, the laminated structure 1 (laminate 3) will not be displaced when the upper mold 10 and the lower mold 11 are fitted together. In particular, if the joint 4 is arranged on a surface (such as a wall surface or a rising portion) parallel to the fitting direction of the upper mold 10 (the removal direction of the molding die), the fiber preform 2 is likely to get caught at the joint 4 when the upper mold 10 and the lower mold 11 are fitted together. Therefore, at least for the outermost layer preform, it is desirable to avoid arranging the joint 4 on a surface parallel to the removal direction of the molding die (particularly in the middle of a parallel surface).

[0043] Therefore, according to the configuration of this embodiment, it is possible to suppress or prevent the fiber preform 2 from getting caught when the upper mold 10 and the lower mold 11 are fitted together, thereby suppressing the occurrence of manufacturing defects and improving production technology.

[0044] In addition, in this embodiment, the laminate 3 is made up of alternating layers of a first type in which the joints 4 between adjacent fiber preforms 2 are arranged in a plane that is approximately parallel to the mold-removal direction of the mold, and layers of a second type in which the joints 4 between adjacent fiber preforms 2 are arranged in a plane that is approximately perpendicular to the mold-removal direction of the mold.

[0045] In the example of Figure 7, the first layer 3A (preform for the innermost layer) and the third layer 3C (preform for the outermost layer) correspond to the second type of layer in which the bonding portion 4 is arranged on a surface approximately perpendicular to the drawing direction of the mold, and the second layer 3B (preform for the intermediate layer) corresponds to the first type of layer in which the bonding portion 4 is arranged on a surface approximately parallel to the drawing direction of the mold. Therefore, the laminate structure 1 (laminate 3) is stacked in the following order from the innermost layer: the preform for the innermost layer (second type of layer), the preform for the intermediate layer (first type of layer), and the preform for the outermost layer (second type of layer). In other words, the first type of layers and the second type of layers are stacked alternately.

[0046] In this way, when constructing the laminated structure 1 (laminate 3), first type layers in which the joints 4 are located on surfaces approximately parallel to the die-removal direction and second type layers in which the joints 4 are located on surfaces approximately perpendicular to the die-removal direction, which offers less resistance, are alternately laminated to reduce the resistance applied to each fiber preform 2 when the upper die 10 and the lower die 11 are fitted together, thereby suppressing or preventing the fiber preforms 2 from getting caught and preventing manufacturing defects. However, the third layer 3C (preform for the outermost layer), which is the outermost layer, is always arranged on a surface approximately perpendicular to the die-removal direction.

[0047] In this embodiment, the layer (first type layer) of the laminate 3 where the joint between adjacent fiber preforms 2 on a surface approximately parallel to the drawing direction of the mold is located is arranged to be a layer other than the outermost layer. By not making the first type layer the outermost layer, the resistance applied to each fiber preform 2 when the upper mold 10 and the lower mold 11 are fitted together can be reduced, and the fiber preforms 2 can be suppressed or prevented from getting caught, which can prevent manufacturing defects.

[0048] The laminated structure of this invention corresponds to the laminated structure 1 of the above embodiment, and similarly, the fiber preform corresponds to the fiber preform 2, the laminate corresponds to the laminate 3, the joint corresponds to the joint 4, the molding die corresponds to the upper die 10 and the lower die 11, the laminating process corresponds to step S4, and the injection process corresponds to step S6, but this invention is not limited to this embodiment and can be embodied in various other ways. Furthermore, the specific configurations etc. given in the above embodiment are merely examples and can be changed as appropriate depending on the actual product. [Industrial Applicability]

[0049] The present invention can be used in industries that manufacture laminated structures and molded articles obtained by injecting resin into the laminated structures. [Explanation of symbols]

[0050] 1...Laminated structure 2...Fiber preform 3...Laminate 4…Joint part 10…Upper mold 11…Lower mold

Claims

1. A method for molding a fiber-reinforced plastic, comprising: injecting a resin into a mold having a sheet-like fiber preform made of fibers disposed therein; a lamination step of laminating the fiber preform in a thickness direction in a plurality of layers inside the molding die to form a laminate; an injection step of injecting a resin into the molding die to impregnate the laminate with the resin, Each layer of the laminate is composed of two or more fiber preforms, In the laminating step, joints between adjacent fiber preforms in the outermost layer located on the outermost side of the laminate are arranged on a plane approximately perpendicular to the drawing direction of the mold, and layers of the laminate including joints between adjacent fiber preforms on a plane approximately parallel to the drawing direction of the mold are arranged to be layers other than the outermost layer, and first-type layers of the laminate in which joints between adjacent fiber preforms are on a plane approximately parallel to the drawing direction of the mold and second-type layers in which joints between adjacent fiber preforms are on a plane approximately perpendicular to the drawing direction of the mold are alternately laminated. Molding method.

2. In the lamination step, the fiber preforms of each layer are arranged so that the joints of the fiber preforms of each layer are positioned differently from the joints of the fiber preforms of other layers when viewed from the mold removal direction of the molding die. The molding method according to claim 1.

3. In the lamination process, the joints between adjacent fiber preforms in the outermost layer located on the outermost side of the laminate are arranged so as to avoid at least the middle position of a surface approximately parallel to the molding direction of the molding die. The molding method according to claim 2.

4. A laminated structure including a laminate in which sheet-like fiber preforms are laminated in a thickness direction in a plurality of layers, Each layer of the laminate is composed of two or more fiber preforms, a joint between adjacent fiber preforms in the outermost layer located on the outermost side of the laminate is disposed on a plane substantially perpendicular to the drawing direction of the molding die, In the laminate, a layer including a joint between adjacent fiber preforms on a surface approximately parallel to the drawing direction of the molding die is arranged to be a layer other than the outermost layer. The laminate is configured such that first-type layers, in which the joints between adjacent fiber preforms are on a plane approximately parallel to the drawing direction of the mold, and second-type layers, in which the joints between adjacent fiber preforms are on a plane approximately perpendicular to the drawing direction of the mold, are alternately laminated. Laminated structure.

5. The joints of the fiber preforms of each layer are arranged at different positions relative to the joints of the fiber preforms of other layers when viewed from the mold removal direction of the molding die. The laminated structure according to claim 4.

6. The joints between adjacent fiber preforms in the outermost layer located on the outermost side of the laminate are arranged at least to avoid the middle position of a surface approximately parallel to the molding direction of the molding die. The laminated structure according to claim 5.

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