Flat lightweight member and method for manufacturing the same

Abstract

Provided is a flat lightweight member which is constituted by a fiber-reinforced resin molded article and which has good appearance quality and also excellent productivity while having excellent mechanical characteristics in an end part thereof and excellent adhesiveness between a core layer and a skin layer thereof. The flat lightweight member is characterized by comprising: a skin layer which is constituted by a braided material and a matrix resin; a separation layer which has a bag-like shape and which is present inside the braided material; and a mixture of a matrix resin and a thermally expandable material which is present inside the separation layer.

Description

Technical Field

[0001] The present invention relates to a flat lightweight member (fiber reinforced resin molded product) composed of a skin layer on the surface and a core layer inside that can be used as a propeller blade, and a method for manufacturing the same. Specifically, the present invention relates to a method for manufacturing a flat lightweight member made of a fiber reinforced resin molded product that is excellent in mechanical properties at the end portion, adhesiveness between the core layer and the skin layer, has good appearance quality, and is also excellent in productivity.

Background Art

[0002] Fiber reinforced resins are lightweight, high-strength, and high-rigidity, and thus are used in a wide range of industrial fields. In particular, molded products using prepregs, which are intermediate materials in which a resin is impregnated into a fiber reinforcing material made of long fibers such as reinforcing fibers, are preferably used. In addition, sandwich structure materials in which the skin layer is a fiber reinforced resin and the core layer is porous are effectively used in transportation means such as aircraft, automobiles, and ships, as well as in the sports and leisure fields due to their light weight and toughness. As such a molded product having a sandwich structure, a molded product composed of a skin layer made of a fiber reinforced base material and a core layer made of a thermally expandable material and a matrix resin is known.

[0003] As such a molded product, a propeller blade in which an upper surface prepreg and a lower surface prepreg are laminated and adhered in the thickness direction at the end of the molded product is known. This molded product can be obtained by laminating an upper surface prepreg on one split mold and a lower surface prepreg on the other split mold, and disposing a foaming agent in the space formed by both prepregs when the molds are combined. (For example, Patent Document 1)

[0004] Furthermore, a similar propeller blade is known in which the main part is composed of a skin layer, a core layer, and a separation layer, the peripheral part (the outer circumference of the propeller blade when viewed from the direction in which the projected area of ​​the propeller blade is largest) is composed of a skin layer and a core layer, and additional reinforcing fibers are placed on the leading edge and trailing edge of the propeller blade. In this molded product, a separation layer is placed between the core layer and the skin layer to suppress the passage of thermally expandable material. The separation layer separates the thermally expandable material from the matrix resin that constitutes the core layer, and impregnates only the matrix resin into the dry reinforcing fiber substrate that constitutes the skin layer, thereby forming the skin layer. (For example, Patent Document 2).

[0005] Furthermore, another known form of reinforced fiber substrate is the braiding (braiding or shaping) of the fiber material. Braiding is produced by mechanically weaving fiber bundles together in two or three directions into a cylindrical or other shape. This allows the fiber material to be produced in the desired shape automatically, thereby improving the manufacturing efficiency of reinforced fiber substrates. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 6789887 [Patent Document 2] Japanese Patent Application Publication No. 8-276441 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, in the flat lightweight member described above, where the upper and lower prepregs are laminated and bonded in the thickness direction at the end of the molded product, a region for laminating and bonding the prepregs is required at the end. Therefore, it becomes necessary to place prepregs, which have a higher specific gravity than the core layer, even in the region that should ideally be the core layer for lightweight purposes, resulting in an increase in the weight of the flat lightweight member. Also, for similar reasons, the shape of the flat lightweight member to which this configuration can be applied was sometimes limited. On the other hand, if the structure is simply made by butting the ends of the prepregs together, the joint strength decreases, and foamed resin leaks out of the flat lightweight member, impairing its appearance and surface quality.

[0008] Furthermore, conventional flat, lightweight members, in which the main part consists of a skin layer, a core layer, and a separation layer, the peripheral part consists of a skin layer and a core layer, and additional reinforcing fibers are placed on the leading edge and trailing edge, have the problem that if the separation layer is not placed appropriately, delamination may occur near the separation layer after long-term use, and the core layer and skin layer cannot be firmly integrated.

[0009] Furthermore, conventional methods for manufacturing fiber-reinforced resins, in which a top prepreg is laminated into one split mold and a bottom prepreg into the other split mold, and a foaming agent is placed in the space formed by the two prepregs when the molds are joined, require the prepreg to be laminated onto the surface of a three-dimensional mold at room temperature, and then the mold is heated to cure the prepreg. This process requires considerable effort, special technology and equipment, and also takes a lot of time to heat and cool the mold, resulting in productivity problems.

[0010] In addition, conventional methods for manufacturing fiber-reinforced resins, in which a portion of the matrix resin for the core layer is passed through a separation layer to impregnate and harden a dry reinforcing fiber substrate to form a skin layer, have difficulty obtaining highly accurate and consistent flat lightweight members when the flat lightweight member has a three-dimensional shape rather than being a simple flat plate. This is because the separation layers, which are positioned separately at the top and bottom, may shift during molding. Furthermore, positioning the reinforcing fibers for reinforcement is difficult, and they are prone to shifting during molding, which can cause the center of gravity of the flat lightweight member to change. Moreover, voids, or air bubbles, can form at the edges of the flat lightweight member during the process of impregnating the reinforcing fibers with the matrix resin, which can lead to a decrease in mechanical properties and damage to the appearance of the finished product.

[0011] Thus, with the conventional technologies described above, it has been extremely difficult to obtain a flat, lightweight member that exhibits excellent mechanical properties and adhesion between the core layer and skin layer, as well as good appearance quality, all the way to the edges of the member.

[0012] Therefore, the object of the present invention is to focus on the above-mentioned problems and provide a flat, lightweight member made of a fiber-reinforced resin molded product and a method for manufacturing the same, which has excellent mechanical properties at the edges and adhesion between the core layer and the skin layer, as well as good appearance quality and excellent productivity. [Means for solving the problem]

[0013] To solve the above problems, the present invention employs one of the following configurations. (1) A flat, lightweight member characterized by comprising a skin layer composed of a braiding substrate and a matrix resin, a bag-shaped separation layer located inside the braiding substrate, and a mixture of matrix resin and a thermally expandable material located inside the separation layer. (2) The flat lightweight member according to (1), wherein the braiding base material is composed of a plurality of fiber bundles that form central threads arranged parallel to each other in the same direction, and fiber bundles that form braided threads that intersect with the central threads, and the weight per unit length of the fiber bundles that form central threads used in at least one end region of the flat lightweight member is smaller than the weight per unit length of the fiber bundles that form central threads used in the central region of the flat lightweight member. (3) The flat lightweight member according to (1), wherein the braiding base material is composed of a plurality of fiber bundles that form central threads arranged parallel to each other in the same direction, and fiber bundles that form braided threads that intersect with the central threads, characterized in that the weight per unit length of the fiber bundles that form central threads used in one end region of the flat lightweight member is smaller than the weight per unit length of the fiber bundles that form central threads used in the central region of the flat lightweight member, and the weight per unit length of the fiber bundles that form central threads used in the other end region of the flat lightweight member is larger than the weight per unit length of the fiber bundles that form central threads used in the central region of the flat lightweight member. (4) The flat lightweight member according to any one of (1) to (3), characterized in that the braiding substrate has at least one rib portion containing a fiber-reinforced substrate inside, and the separation layer and the mixture are present in each of the plurality of regions inside the braiding substrate separated by the rib portion. (5) The flat lightweight member according to (4), characterized in that the rib portion includes a fiber-reinforced substrate and a foam and / or resin block disposed inside the fiber-reinforced substrate. (6) A method for manufacturing a flat lightweight member, A process for producing a braiding substrate that constitutes the skin layer, A separation layer placement step involves arranging a bag-shaped separation layer having a shape corresponding to the outer shape of the flat lightweight member inside the braiding substrate, The process involves introducing a mixture of matrix resin and a thermally expandable material into the separation layer, The steps include placing the braiding substrate, in which the separation layer and the mixture are disposed, into the cavity of a lower mold heated to the molding temperature, A mold closing step is performed in which the mold is heated to the molding temperature, the mold is closed, and the cavity is vacuumed. An expansion step is performed to expand the thermally expandable material to integrate the braiding substrate, the separation layer, and the mixture. A method for manufacturing a flat, lightweight member, characterized by including the following: (7) A method for manufacturing a flat lightweight member having at least one rib portion, A process for producing a braiding substrate that constitutes the skin layer, A preparation step for preparing the fiber-reinforced base material that constitutes the rib section, A rib placement step involves arranging the fiber-reinforced substrate constituting the rib portion inside the braiding substrate to divide the inside of the braiding substrate into two or more spaces, A separation layer placement step involves arranging a bag-shaped separation layer having a shape corresponding to the shape of the two or more spaces in the two or more spaces, A feeding step involves introducing a mixture of matrix resin and a thermally expandable material into the separation layer, A material placement step involves placing the braiding substrate, which contains the separation layer, the mixture, and the fiber-reinforced substrate constituting the rib portion, on a lower mold heated to the molding temperature. The process involves heating the mold to the molding temperature, closing the mold, and then vacuuming the mold cavity. An expansion step is performed to expand the thermally expandable material to integrate the braiding substrate, the separation layer, the mixture, and the fiber-reinforced substrate constituting the rib portion. A method for manufacturing a flat, lightweight member having at least one rib portion, characterized by including the following: (8) The method for manufacturing a flat lightweight member according to (7), characterized in that the rib portion is composed of a fiber-reinforced base material and foam and / or wood disposed inside the fiber-reinforced base material. (9) In the braiding base material production step, the braiding base material is composed of a plurality of fiber bundles serving as central yarns arranged in parallel in the same direction and fiber bundles serving as cross yarns intersecting the central yarns. In at least one end region of the flat lightweight member, a fiber bundle smaller than the fiber bundle serving as the central yarn in the central region of the flat lightweight member is used for the fiber bundle serving as the central yarn. The method for manufacturing a flat lightweight member according to any one of (6) to (8) above, characterized in that. (10) In the braiding base material production step, the braiding base material is composed of a plurality of fiber bundles serving as central yarns arranged in parallel in the same direction and fiber bundles serving as cross yarns intersecting the central yarns. In one end region of the flat lightweight member, a fiber bundle smaller than the fiber bundle serving as the central yarn in the central region of the flat lightweight member is used for the fiber bundle serving as the central yarn, and in the other end region of the flat lightweight member, a fiber bundle larger than the fiber bundle serving as the central yarn in the central region of the flat lightweight member is used for the fiber bundle serving as the central yarn. The method for manufacturing a flat lightweight member according to any one of (6) to (8) above, characterized in that. (11) The method for manufacturing a flat lightweight member according to any one of (6) to (10) above, characterized in that the fiber bundles serving as central yarns and the fiber bundles serving as cross yarns constituting the braiding base material are both dry fiber bundles. (12) The method for manufacturing a flat lightweight member according to any one of (6) to (10) above, characterized in that the fiber bundles serving as central yarns and the fiber bundles serving as cross yarns constituting the braiding base material are both prepregs containing resin. [[Effect of the Invention]]

[0014] According to the flat lightweight member and the method for manufacturing the same according to the present invention, it is possible to obtain a flat lightweight member made of a fiber reinforced resin molded product that is excellent in mechanical properties at the ends and adhesiveness between the core layer and the skin layer, has good appearance quality, and is also excellent in productivity. [[Brief Description of the Drawings]]

[0015] [Figure 1]This shows a top view (a) and a cross-sectional view (b) in AA' of an example of a flat, lightweight member obtained by the manufacturing method of the present invention. [Figure 2] The images show a top view (a) and cross-sectional views (b) to (d) in AA' of an example of a flat, lightweight member obtained by the manufacturing method of the present invention. [Figure 3] Figures 2(b) and 2(c) are perspective top views showing examples of the shape of the separation layer in the flat, lightweight member. [Figure 4] This figure shows the steps in the method for manufacturing a flat, lightweight member according to the present invention. [Figure 5] This is a schematic diagram showing an example of the basic structural framework that forms the basis of braiding materials. [Figure 6] This is a top view (a) showing only the contour of the braiding base material in the flat lightweight member of the present invention, and a partially enlarged schematic diagram (b) of this top view (a). [Modes for carrying out the invention]

[0016] The present invention will be described in detail below, along with embodiments, with reference to the drawings.

[0017] The method for manufacturing a flat, lightweight member according to the present invention is: A process for producing a braiding substrate that constitutes the skin layer, A separation layer placement step involves arranging a bag-shaped separation layer having the outer shape of the flat lightweight member inside the braiding substrate, The process involves introducing a mixture of matrix resin and a thermally expandable material into the interior of the separation layer. The steps include placing the braiding substrate, in which the separation layer and the mixture are disposed, onto a lower mold heated to the molding temperature, The process involves heating the mold to the molding temperature, closing the mold, and then vacuuming the cavity. An expansion step is performed to expand the thermally expandable material to integrate the braiding substrate, the separation layer, and the mixture. It is characterized by including.

[0018] In this method for manufacturing flat, lightweight members, by using a braiding substrate as the base material constituting the skin layer, the continuity of the fibers at both ends in the direction intersecting the longitudinal direction of the flat, lightweight member is maintained, thereby eliminating delamination at the ends. Furthermore, by making the separation layer a bag-like shape with the outer shape of the flat, lightweight member, displacement of the separation layer during molding is prevented, and the thermally expandable material is prevented from flowing out to the surface. As a result, the surface quality is improved, and the occurrence of voids is prevented, thus preventing deterioration of the end strength.

[0019] Figure 1 shows one embodiment of a flat, lightweight member obtained by the manufacturing method of the present invention.

[0020] In Figure 1(a), 1 is a top view of a flat lightweight member, with the right side of the paper being the tip a and the left side being the base b. Figure 1(b) shows the AA' cross-section of this flat lightweight member 1 (i.e., the cross-section in a direction intersecting the longitudinal direction of the flat lightweight member 1). This flat lightweight member 1 mainly consists of a skin layer 21, a core layer 30, and a separation layer 40.

[0021] Figure 4 shows each step in the manufacturing method of the flat lightweight member of the present invention, and shows the process of molding fiber-reinforced resin using a double-sided mold in which a cavity in the shape of the flat lightweight member is formed at the mating surface of the upper mold 81 and the lower mold 82. The steps will be described in order below. Figure 4(a) shows the braiding substrate preparation step, Figure 4(b) shows the separation layer placement step, Figure 4(c) shows the input of a mixture containing matrix resin and thermally expandable material, Figure 4(d) shows the placement of the braiding substrate containing the separation layer and mixture, Figure 4(e) shows the mold closing step, Figure 4(f) shows the expansion step of the thermally expandable material, and Figure 4(g) shows the demolding step to obtain the flat lightweight member.

[0022] [Braiding substrate preparation process (Figure 4(a)] In the present invention, the skin layer is composed of at least one braiding base material 100. Figure 5 shows a schematic diagram of the basic braided structure of the braiding base material 100. The braiding base material 100 refers to a fiber base material obtained by weaving fiber bundles of reinforcing fibers using a braiding machine. It is manufactured by mechanically braiding the fiber bundles into a three-dimensional shape such as a cylinder, using braiding threads in only two directions, or in three directions including a central thread in addition to the braiding threads. Using a braiding machine, braiding base materials can be laminated while adjusting the braiding angle θ of the fiber bundles, and since there are no breaks in the reinforcing fibers except at the longitudinal ends of the hollow braiding base material, it is possible to obtain a molded product that is lighter, more rigid, and stronger. Furthermore, by using a mandrel having the desired flat, lightweight member outer shape, it is possible to manufacture a braiding base material that conforms to the product shape in advance (for example, a braiding base material 100 with the shape shown in Figure 4(a)), thereby improving production efficiency.

[0023] If necessary, multiple layers of braiding substrate can be laminated. Furthermore, if the mandrel shape changes its cross-sectional shape along its longitudinal direction, the weave can be controlled by increasing the braiding angle in areas with longer cross-sectional perimeters and decreasing it in areas with smaller cross-sectional perimeters when laminating the fiber bundles. This allows for the creation of a braiding substrate with smaller gaps. To maintain a constant braiding angle, the size of the fiber bundles used (number of single threads constituting the bundle) can be reduced, and multiple layers of braiding substrate can be laminated to minimize gaps. Therefore, the details of the braiding substrate should be designed according to the performance requirements of the product.

[0024] It is preferable to prepare the mandrel used for braiding by dividing it into at least two or more parts. This makes it easier to remove the mandrel from the braiding substrate after it has been prepared.

[0025] Examples of reinforcing fibers used in braiding substrates include organic fibers such as aramid fibers, polyethylene fibers, and poly(p-phenylene benzoxide) (PBO) fibers; inorganic fibers such as glass fibers, carbon fibers, silicon carbide fibers, alumina fibers, tyranno fibers, basalt fibers, and ceramic fibers; metallic fibers such as stainless steel fibers and steel fibers; and other fibers such as boron fibers, natural fibers, and modified natural fibers. Among these, carbon fibers are particularly lightweight, possess excellent properties in specific strength and specific modulus, and also have excellent heat resistance and chemical resistance, making them suitable for components such as automobile panels where weight reduction is desired. Among these, PAN-based carbon fibers, which are easily obtained as high-strength carbon fibers, are preferred.

[0026] In the present invention, the thickness of the skin layer is preferably 0.1 mm or more and 10 mm or less, more preferably 0.2 mm or more and 5 mm or less, and even more preferably 0.4 mm or more and 2 mm or less. This thickness should be set considering the balance between strength and lightness required for a flat, lightweight member.

[0027] [Separation layer placement process (Figure 4(b)] In this invention, a separation layer is placed inside the braiding substrate obtained in the braiding substrate manufacturing process described above. The separation layer is bag-shaped with the outer shape of a flat lightweight member. This shape prevents the separation layer from shifting during the molding of the flat lightweight member and prevents the thermally expandable material from flowing out to the surface, thereby improving surface quality and preventing the formation of voids. It also improves the occurrence of "resin-rich" areas at the edges of the flat lightweight member.

[0028] As the separation layer, a thin sheet with a separation function that allows resin to pass through but substantially blocks the thermally expandable material after thermal expansion is used. Suitable materials include thin nonwoven fabrics with small mesh openings, woven or knitted fiber sheets, and porous films such as polyethylene or polypropylene. Two or more of these can be used in combination. The mesh opening size is selected to be within a range that prevents the passage of the thermally expandable material, depending on the type and expansion properties of the material. In addition, glass fibers, carbon fibers, and aramid fibers, which themselves have reinforcing properties, can also be used as the material for the separation layer.

[0029] The separation layer is made of a material having the external shape of the desired flat lightweight member. Here, the "external shape of the flat lightweight member" may be exactly the same as the shape of the flat lightweight member, or it may be an affine transformed shape obtained by affine transformation of the flat lightweight member, or an offset shape obtained by offsetting the flat lightweight member in the thickness direction. Furthermore, the dimensions of the separation layer may be the same as those of the flat lightweight member, or they may be different. If the dimensions are different, for example, by the aforementioned affine transformation or offset, it is preferable to make one axis or two or more axes of the Cartesian coordinate system 80% to 150% of the original dimensions of the flat lightweight member. In other words, in the present invention, the separation layer is made of a material having a shape corresponding to the external shape of the desired flat lightweight member.

[0030] [Step of adding a mixture containing matrix resin and thermally expandable material (Figure 4(c)] Next, as described above, a thermally expandable material and a matrix resin are introduced into the separation layer located inside the braiding substrate. The core layer is formed from these thermally expandable materials and the matrix resin (hereinafter referred to as the first matrix resin).

[0031] The weight ratio of the thermally expandable material to the first matrix in the core layer is preferably in the range of 5% to 100%, and more preferably in the range of 10% to 40%, when the weight of the first matrix resin is set to 100%. Setting the weight of the thermally expandable material to 5% or more reduces the specific gravity of the core layer, making it easier to achieve lightweight properties. Setting it to 10% or more reduces the partial "resin richness" that occurs when the first matrix resin separates from the thermally expandable material, resulting in a more homogeneous structure for the core layer and reducing variations in the center of gravity. On the other hand, setting it to 100% or less allows the first matrix resin to be present between the thermally expandable materials, enabling crosslinking of the thermally expandable materials, making the core layer rigid and able to maintain its shape. If it is greater than 100%, the crosslinking of the thermally expandable materials will be insufficient, making the core layer brittle and prone to deformation. Furthermore, by keeping the amount below 40%, the first matrix resin can cover the thermally expandable material, thereby suppressing the occurrence of cracks in the core layer and maintaining good mechanical properties of the core layer over a long period of time.

[0032] [Matrix resin] Examples of the first matrix resin in the present invention include thermosetting resins such as epoxy resins, unsaturated polyester resins, vinyl ester resins, phenolic resins, epoxy acrylate resins, urethane acrylate resins, phenoxy resins, alkyd resins, urethane resins, maleimide resins, and cyanate resins, as well as thermoplastic resins such as polyamide resins, polyacetal resins, polyacrylate resins, polysulfone resins, acrylic butadiene styrene (ABS) resins, polyester resins, acrylic resins, polybutylene terephthalate (PBT) resins, polyethylene terephthalate (PET) resins, polyethylene resins, polypropylene resins, polyphenylene sulfide (PPS) resins, polyether ether ketone (PEEK) resins, liquid crystal polymers, vinyl chloride, polytetrafluoroethylene and other fluororesins, and silicones. Among these, thermosetting resins are particularly preferred. Because the first matrix resin is a thermosetting resin, the cured matrix resin covers the thermally expandable material of the core layer, forming a porous structure. This prevents deformation and expansion of the core layer even when heat is applied to the fiber-reinforced resin molded product.

[0033] [Thermally expandable materials] The thermally expandable materials used in this invention refer to thermally expandable resin particles that undergo volume expansion when heated and warmed during molding, and thermally expandable materials that are already in a thermally expanded state but can be compressed by pressurization.

[0034] When a thermally expandable material is mixed with a first matrix resin and heated, it undergoes volume expansion. If the first matrix resin is a thermosetting resin, the curing of the thermosetting resin forms a lightweight, porous core layer. If the first matrix resin is a thermoplastic resin, the molten thermoplastic resin solidifies or the softened thermoplastic resin binds together during cooling, forming a lightweight, porous core layer.

[0035] The volume expansion coefficient α (%) of a mixture of a thermally expandable material and a first matrix resin is given by V1 (cm³) of the volume of the mixture before expansion. 3 ), the volume after expansion is V2(cm3 When ), it is expressed by the following equation (1). α = 100 × (V2 - V1) ÷ V1 ... (1) The volume expansion coefficient α varies depending on the weight ratio of the thermally expandable material to the first matrix resin and the heating conditions during molding, but it is preferably in the range of 30% to 2000%.

[0036] Examples of thermally expandable materials include polyacrylonitrile copolymers, polymethacrylonitrile copolymers, polyvinylidene chloride copolymers, polystyrene or polystyrene copolymers, polyolefins, and polyphenylene oxide copolymers, and it is preferable that they be capsule-shaped particles containing a thermally expandable gas. In particular, thermally expandable materials using low-boiling-point hydrocarbons as the thermally expandable gas are preferred because they have a large volume expansion coefficient and allow for the formation of a lightweight core layer.

[0037] The size of the thermally expandable particles is preferably in the range of 1 μm to 1 mm in average particle size before volume expansion. By setting the average particle size to 1 μm or larger, leakage of the thermally expandable material onto the surface of the fiber-reinforced resin molded product due to resin flow during molding can be suppressed. Furthermore, by setting it to 1 mm or less, even if the core layer has a thin-walled section, the thermally expandable material can penetrate to that section, making the core layer lighter and reducing density unevenness between the thermally expandable particles and the first matrix resin in the core layer.

[0038] Examples of such thermally expandable materials include "Matsumoto Microsphere" (registered trademark) manufactured by Matsumoto Oil & Fat Pharmaceutical Co., Ltd., "Expancell" (registered trademark) manufactured by Nobel Co., Ltd., and "Eslen Beads" manufactured by Sekisui Chemical Co., Ltd., but the present invention is not limited to these products.

[0039] In this invention, only one type of thermally expandable material may be used, or a mixture of multiple types of thermally expandable materials may be used. Furthermore, the thermally expandable material may be used alone, or it may be used in combination with non-thermally expandable particles such as glass beads.

[0040] In the step of introducing a mixture of resin and thermally expandable material into the separation layer, it is preferable to preheat the mixture of thermally expandable material and the first matrix resin. By using this method, the viscosity of the mixture of thermally expandable material and the first matrix resin is reduced, which shortens the introduction time and makes it easier to adjust the amount introduced. The mixture of thermally expandable material and the first matrix resin can be preheated using an oven or microwave oven. After introducing the resin and thermally expandable material into the separation layer, the edges of the separation layer can be sealed with a heat sealer or the like, or the edges can be folded in several layers, if necessary. This procedure makes it possible to prevent the thermally expandable material from flowing out of the separation layer.

[0041] [Process of placing the braiding substrate containing the separation layer and mixture into the mold (Figure 4(d)] In the present invention, the braiding substrate containing the separation layer and mixture obtained through the aforementioned input step is then placed in the lower mold. The molding temperature set as the temperature of the lower mold depends on the type of first matrix resin, but when using a thermosetting resin, it is preferable to set the temperature in the range of 80°C to 230°C. Setting the temperature above 80°C promotes the reaction of the matrix resin, and setting it below 230°C suppresses the decomposition of the matrix resin. According to the manufacturing method of fiber-reinforced resin of the present invention, there is no need to raise or lower the temperature of the mold, so the manufacturing time can be shortened compared to conventional methods that raise or lower the temperature of the mold. In addition, since the braiding substrate is pre-formed into a three-dimensional shape that conforms to the product, positioning can be done relatively easily.

[0042] [Mold closing process (Figure 4(e) to demolding process diagram (4(g))] Next, the upper mold, heated to the molding temperature, is closed over the lower mold in which the braiding substrate containing the separation layer and mixture from the previous step is placed. The mold closing process makes the mold cavity, which has the shape of the desired flat, lightweight member, airtight, and the air is exhausted, creating a vacuum inside the mold cavity.

[0043] While it is preferable to set the temperature of the upper mold to the same temperature as the temperature of the lower mold, the present invention is not limited to this.

[0044] Then, by expelling the air from the mold and creating a vacuum in the cavity, the thermally expandable material begins to expand after reaching a predetermined temperature, forming a core layer. Due to the expansion of the thermally expandable material, the first matrix resin permeates through the separation layer, impregnates the skin layer, is pressed against the mold cavity, and is pressurized, resulting in a fiber-reinforced resin molded product of excellent quality.

[0045] In the present invention, by going through such a mold closing process, it is possible to reduce voids in the skin layer and improve the mechanical properties of the flat lightweight member, as well as prevent the generation of air bubbles on the surface, thereby obtaining a flat lightweight member made of fiber-reinforced resin molded product with excellent appearance quality.

[0046] [More Preferred Embodiments of the Invention] The braiding base material in the present invention is composed of a plurality of fiber bundles that form central threads arranged parallel to each other in the same direction, and fiber bundles that form braided threads that intersect with the central threads. Preferably, there is a difference in size between the central and end regions of the cross-section in a direction intersecting the longitudinal direction of the flat lightweight member, and in particular, it is preferable that the fiber bundle that forms the central thread used in at least one end region of the flat lightweight member is smaller than the fiber bundle that forms the central thread used in the central region of the flat lightweight member.

[0047] Figure 6 shows a top view (a) showing only the outline of the braiding base material in the form of a flat lightweight member, and a schematic diagram (b) of the fiber bundle configuration as seen from the side of a part of the top view (a). The schematic diagram shown here is just one example, and the number of fiber bundles used is not limited thereto. In this flat lightweight member, the central thread 72 of the end region 90 is composed of a smaller fiber bundle than the central thread 71 used in the central region 80. From the viewpoint of energy efficiency, if at least one end of the flat lightweight member has a pointed shape, it is preferable to use a smaller fiber bundle for the central thread of the end region. By arranging an appropriate amount of reinforcing fibers at the ends in this way, delamination during manufacturing can be prevented, and even when dry fibers are used, the occurrence of unimpregnated areas in the flat lightweight member can be prevented.

[0048] Here, the end region where relatively small fiber bundles are arranged as described above is preferably the region in a cross-section in a direction intersecting the longitudinal direction of the flat lightweight member, from the end of the flat lightweight member to a position five times the thickness of the skin layer. More preferably, it is the region in a cross-section in a direction intersecting the longitudinal direction of the flat lightweight member to a position five times the thickness of the skin layer. Even more preferably, it is the region in a cross-section in a direction intersecting the longitudinal direction of the flat lightweight member to a position twenty times the thickness of the skin layer. On the other hand, the central region where relatively large fiber bundles are arranged is preferably the region in a cross-section in a direction intersecting the longitudinal direction of the flat lightweight member, within a range of ±30% of the center position in the longitudinal direction of that cross-section.

[0049] Methods for reducing the size of fiber bundles include reducing the number of individual fibers that make up the bundle, using thinner individual fibers (smaller diameter), and using thicker individual fibers (larger diameter) while reducing the number of individual fibers, thereby reducing the weight per unit length of the fiber bundle. However, these methods are not limited to these, and it is also possible to use multiple methods or combine multiple fibers.

[0050] On the other hand, the braiding base material in the present invention is composed of a plurality of fiber bundles that form central threads arranged parallel to each other in the same direction, and fiber bundles that form braided threads that intersect with the central threads, and it is also preferable that the fiber bundle that forms the central threads used in at least one end region of the flat lightweight member is larger than the fiber bundle that forms the central threads used in the central region of the flat lightweight member.

[0051] In the flat lightweight member shown in Figure 6, the central thread 73 in the end region 91 is composed of a larger fiber bundle than the central thread 71 used in the central region 80. When at least one end of the flat lightweight member has a rounded shape that is thicker than the other parts, using a larger fiber bundle for the central thread in the end region makes it possible to improve the end strength. With this method, positional displacement is less likely to occur compared to when additional reinforcing materials are placed, so a molded product with less variation and stability can be obtained.

[0052] Furthermore, the end region where relatively large fiber bundles are arranged, as described above, is preferably the region in a cross-section in a direction intersecting the longitudinal direction of the flat lightweight member, extending from the end of the flat lightweight member to a position five times the thickness of the skin layer. More preferably, it is the region extending from the end of the flat lightweight member to a position ten times the thickness of the skin layer. Even more preferably, it is the region extending from the end of the flat lightweight member to a position twenty times the thickness of the skin layer. On the other hand, the central region where relatively small fiber bundles are arranged is preferably the region in a cross-section in a direction intersecting the longitudinal direction of the flat lightweight member, extending within ±30% of the center position in the longitudinal direction of that cross-section.

[0053] Methods for increasing the size of a fiber bundle include increasing the number of individual fibers that make up the bundle, using thicker individual fibers (larger diameter), and using thinner individual fibers (smaller diameter) and increasing the number of individual fibers to increase the weight per unit length of the fiber bundle. However, methods are not limited to these, and it is also possible to use multiple methods or combine multiple fibers.

[0054] Furthermore, in the braiding substrate of the present invention, it is preferable that the fiber bundle that becomes the central thread used in one end region of the flat lightweight member is smaller than the fiber bundle that becomes the central thread used in the central region of the flat lightweight member, and the fiber bundle that becomes the central thread used in the opposite end region of the flat lightweight member is larger than the fiber bundle that becomes the central thread used in the central region of the flat lightweight member. If one end of the flat lightweight member is pointed and the other end is rounded and thicker than the other parts, by using a fiber bundle smaller than the fiber bundle that becomes the central thread used in the central region of the flat lightweight member in the pointed end region, and by using a fiber bundle larger than the fiber bundle that becomes the central thread used in the central region of the flat lightweight member in the rounded end region, the strength of both ends can be improved and the resin impregnation of the pointed end can be prevented.

[0055] In the present invention, it is preferable that both the fiber bundle that forms the central yarn and the fiber bundle that forms the braided yarn constituting the braiding base material are dry fiber bundles. In this case, the process passability in the braiding machine is good, and it becomes possible to stably produce the braiding base material.

[0056] On the other hand, it is also preferable that both the fiber bundle that forms the central thread and the fiber bundle that forms the braided thread constituting the braiding base material are resin-containing prepregs. In this case, the shape stability of the braiding base material can be further improved. Examples of the second matrix resin used in such a prepreg include thermosetting resins such as epoxy resin, unsaturated polyester resin, vinyl ester resin, phenolic resin, epoxy acrylate resin, urethane acrylate resin, phenoxy resin, alkyd resin, urethane resin, maleimide resin, and cyanate resin, as well as thermoplastic resins such as polyamide resin, polyacetal resin, polyacrylate resin, polysulfone resin, acrylic butadiene styrene (ABS) resin, polyester resin, acrylic resin, polybutylene terephthalate (PBT) resin, polyethylene terephthalate (PET) resin, polyethylene resin, polypropylene resin, polyphenylene sulfide (PPS) resin, polyether ether ketone (PEEK) resin, liquid crystal polymer, vinyl chloride, polytetrafluoroethylene and other fluororesins, and silicone. Among these, it is particularly preferable to use thermosetting resins.

[0057] Another preferred manufacturing method of the present invention is as follows: A method for manufacturing a flat, lightweight member having at least one rib portion, A process for producing a braiding substrate that constitutes the skin layer, A preparation step for preparing the fiber-reinforced base material that constitutes the rib section, A rib placement step involves arranging the fiber-reinforced substrate constituting the rib portion inside the braiding substrate to divide the inside of the braiding substrate into two or more spaces, A separation layer arrangement step involves arranging a bag-shaped separation layer having the shape of two or more spaces in the two or more spaces, A feeding step involves introducing a mixture of matrix resin and a thermally expandable material into the separation layer, A material placement step involves placing the braiding substrate, which contains the separation layer, the mixture, and the fiber-reinforced substrate constituting the rib portion, on a lower mold heated to the molding temperature. The process involves heating the mold to the molding temperature, closing the mold, and then vacuuming the mold cavity. An expansion step is performed to expand the thermally expandable material to integrate the braiding substrate, the separation layer, the mixture, and the fiber-reinforced substrate constituting the rib portion. It consists of being characterized by including

[0058] This configuration ensures the continuity of fibers at both ends in the direction intersecting the longitudinal direction of the flat lightweight member, preventing delamination at the ends. Furthermore, by making the separation layer a bag-like shape with spaces divided by the fiber-reinforced base material constituting the rib portion, displacement of the separation layer during molding is prevented, and the thermally expandable material is prevented from flowing to the surface, resulting in a flat lightweight member with good surface quality. Moreover, since the occurrence of voids can be prevented, deterioration of end strength can be prevented. In addition, according to this embodiment, a flat lightweight member with rib portions and even higher strength can be easily and productively obtained.

[0059] The shape of the separation layer may be exactly the same as the space divided by the fiber-reinforced substrate, or it may be an affine transformed shape obtained by affine transformation of the divided space, or an offset shape obtained by offsetting the divided space in the thickness direction. Furthermore, the dimensions of the separation layer may be the same as the dimensions of the divided space, or they may be different. If the dimensions are different, for example, by the aforementioned affine transformation or offset, it is preferable to make one axis or two or more axes of the Cartesian coordinate system 80% to 150% of the original dimensions of the divided space. In other words, in the present invention, the separation layer only needs to have a shape that corresponds to the external shape of the desired flat lightweight member.

[0060] Figures 2 and 3 show one embodiment of a flat lightweight member obtained by this manufacturing method. Figure 2(a) shows a top view of the flat lightweight member, with the right side of the paper being the tip a and the left side being the base b. The AA' cross section of this flat lightweight member 1 is shown in Figures 2(b) to 2(d). Figure 2(b) shows the case with one rib section, and Figures 2(c) and 2(d) show the case with two rib sections. Figure 3(a) is a top perspective view of the flat lightweight member corresponding to Figure 2(b), and Figure 3(b) is a top perspective view of the flat lightweight member corresponding to Figure 2(c) and Figure 2(d), respectively, showing the shape of the separation layer.

[0061] This manufacturing method allows for easy molding of rib sections according to the required rigidity and strength of the component. The fiber-reinforced substrate constituting the rib section may be a braiding substrate, similar to the skin layer, or it may be a prepreg as described above. Furthermore, as shown in Figure 2(d), it is possible to place a core material 34, pre-molded into a desired shape, inside the fiber-reinforced substrate constituting the rib section. By constructing the rib section with a core material and a fiber-reinforced substrate arranged around the core material 34, the position of the rib section can be molded stably. As the core material 34, foam, resin blocks, wood, etc., can be used, but foam is preferred in terms of weight reduction. As materials for foams and resin blocks, thermosetting resins such as epoxy resin, unsaturated polyester resin, vinyl ester resin, phenolic resin, epoxy acrylate resin, urethane acrylate resin, phenoxy resin, alkyd resin, urethane resin, maleimide resin, and cyanate resin can be used, as well as polyamide resin, polyacetal resin, polyacrylate resin, polysulfone resin, acrylic butadiene styrene (ABS) resin, polyester resin, acrylic resin, polybutylene terephthalate (PBT) resin, polyethylene terephthalate (PET) resin, polyethylene resin, polypropylene resin, polyphenylene sulfide (PPS) resin, polyether ether ketone (PEEK) resin, liquid crystal polymer, PVC, polytetrafluoroethylene and other fluororesins, and thermoplastic resins such as silicone can be used. As for the molding method of the core material, methods such as foam injection into a mold and molding with a 3D printer can be used. [Industrial applicability]

[0062] The present invention is applicable to flat, lightweight members made from any plate-shaped fiber-reinforced resin molded product and to the manufacture of such members. The flat, lightweight members obtained by the present invention are suitably used, for example, in transportation equipment such as aircraft, automobiles, and ships, and as propeller blade structures in the sports and leisure fields. [Explanation of symbols]

[0063] 1. Flat lightweight member 21, 22, 23 Skin layers 30, 31, 32, 33 Core Layer 34 Core Materials 35 mixture 40, 41, 42, 43, 44, 45, 46, 47 Separation layer 50, 51, 52 Fiber-reinforced base material constituting the rib section 60, 61 Braided yarn 70, 71, 72, 73 Central thread 80 central area 81 Upper mold 82 Lower mold 90, 91 End area 100 Braiding substrate X Width direction Y-direction (longitudinal direction) a Tip b. Base

Claims

1. A flat lightweight member comprising a skin layer composed of a braiding substrate and a matrix resin, a bag-shaped separation layer located inside the braiding substrate, and a mixture of matrix resin and a thermally expandable material located inside the separation layer, wherein the braiding substrate is composed of a plurality of fiber bundles that form central threads arranged parallel to each other in the same direction, and fiber bundles that form braided threads that intersect with the central threads, and the weight per unit length of the fiber bundles that form central threads used in at least one end region of the flat lightweight member is smaller than the weight per unit length of the fiber bundles that form central threads used in the central region of the flat lightweight member.

2. A flat lightweight member comprising a skin layer composed of a braiding substrate and a matrix resin, a bag-shaped separation layer located inside the braiding substrate, and a mixture of matrix resin and a thermally expandable material located inside the separation layer, wherein the braiding substrate is composed of a plurality of fiber bundles that form central threads arranged parallel to each other in the same direction, and fiber bundles that form braided threads that intersect with the central threads, wherein the weight per unit length of the fiber bundles that form central threads used in one end region of the flat lightweight member is smaller than the weight per unit length of the fiber bundles that form central threads used in the central region of the flat lightweight member, and the weight per unit length of the fiber bundles that form central threads used in the other end region of the flat lightweight member is larger than the weight per unit length of the fiber bundles that form central threads used in the central region of the flat lightweight member.

3. The flat lightweight member according to claim 1 or 2, characterized in that it has at least one rib portion containing a fiber-reinforced substrate inside the braiding substrate, and the separation layer and the mixture are present in each of the plurality of regions inside the braiding substrate separated by the rib portion.

4. The flat lightweight member according to claim 3, characterized in that the rib portion includes a fiber-reinforced substrate and a foam and / or resin block disposed inside the fiber-reinforced substrate.

5. A method for manufacturing a flat, lightweight member, A process for producing a braiding substrate that constitutes the skin layer, A separation layer placement step involves arranging a bag-shaped separation layer having a shape corresponding to the outer shape of the flat lightweight member inside the braiding substrate, The process involves introducing a mixture of matrix resin and a thermally expandable material into the separation layer, The steps include placing the braiding substrate, in which the separation layer and the mixture are disposed, into the cavity of a lower mold heated to the molding temperature, A mold closing step is performed in which the mold is heated to the molding temperature, the mold is closed, and the cavity is vacuumed. An expansion step is performed to expand the thermally expandable material to integrate the braiding substrate, the separation layer, and the mixture. A method for manufacturing a flat lightweight member, comprising the steps for manufacturing the braiding base material, wherein the braiding base material is composed of a plurality of fiber bundles that will become central threads arranged parallel to each other in the same direction, and fiber bundles that will become braided threads intersecting the central threads, and wherein in at least one end region of the flat lightweight member, a fiber bundle that will become the central thread is used that is smaller than the fiber bundle that will become the central thread in the central region of the flat lightweight member.

6. A method for manufacturing a flat lightweight member, A process for producing a braiding substrate that constitutes the skin layer, A separation layer placement step involves arranging a bag-shaped separation layer having a shape corresponding to the outer shape of the flat lightweight member inside the braiding substrate, The process involves introducing a mixture of matrix resin and a thermally expandable material into the separation layer, The steps include placing the braiding substrate, in which the separation layer and the mixture are disposed, into the cavity of a lower mold heated to the molding temperature, A mold closing step is performed in which the mold is heated to the molding temperature, the mold is closed, and the cavity is vacuumed. An expansion step is performed to expand the thermally expandable material to integrate the braiding substrate, the separation layer, and the mixture. Includes, A method for manufacturing a flat lightweight member, characterized in that, in the braiding base material manufacturing step, the braiding base material is composed of a plurality of fiber bundles that will become central threads arranged parallel to each other in the same direction and fiber bundles that will become braided threads intersecting the central threads, and in one end region of the flat lightweight member, a fiber bundle smaller than the fiber bundle that will become the central thread in the central region of the flat lightweight member is used for the fiber bundle that will become the central thread, and in the other end region of the flat lightweight member, a fiber bundle larger than the fiber bundle that will become the central thread in the central region of the flat lightweight member is used for the fiber bundle that will become the central thread.

7. A method for manufacturing a flat, lightweight member having at least one rib portion, A process for producing a braiding substrate that constitutes the skin layer, A preparation step for preparing the fiber-reinforced base material that constitutes the rib section, A rib arrangement step involves arranging the fiber-reinforced substrate constituting the rib portion inside the braiding substrate to divide the inside of the braiding substrate into two or more spaces, A separation layer placement step involves arranging a bag-shaped separation layer having a shape corresponding to the shape of the two or more spaces in the two or more spaces, A feeding step involves introducing a mixture of matrix resin and a thermally expandable material into the separation layer, A material placement step involves placing the braiding substrate, which contains the separation layer, the mixture, and the fiber-reinforced substrate constituting the rib portion, on a lower mold heated to the molding temperature. The process involves heating the mold to the molding temperature, closing the mold, and then vacuuming the mold cavity. An expansion step is performed to expand the thermally expandable material to integrate the braiding substrate, the separation layer, the mixture, and the fiber-reinforced substrate constituting the rib portion. A method for manufacturing a flat, lightweight member having at least one rib portion, characterized by including the following:

8. The method for manufacturing a flat lightweight member according to claim 7, characterized in that the rib portion is composed of a fiber-reinforced base material and a foam and / or wood disposed inside the fiber-reinforced base material.

9. The method for manufacturing a flat lightweight member according to claim 7 or 8, characterized in that, in the braiding base material manufacturing step, the braiding base material is composed of a plurality of fiber bundles that will become central threads arranged parallel to each other in the same direction and fiber bundles that will become braided threads intersecting the central threads, and in at least one end region of the flat lightweight member, a fiber bundle that is smaller than the fiber bundle that will become the central thread in the central region of the flat lightweight member is used for the fiber bundle that will become the central thread.

10. The method for manufacturing a flat lightweight member according to claim 7 or 8, characterized in that, in the braiding base material manufacturing step, the braiding base material is composed of a plurality of fiber bundles that will become central threads arranged parallel to each other in the same direction and fiber bundles that will become braided threads intersecting the central threads, and in one end region of the flat lightweight member, a fiber bundle smaller than the fiber bundle that will become the central thread in the central region of the flat lightweight member is used for the fiber bundle that will become the central thread, and in the other end region of the flat lightweight member, a fiber bundle larger than the fiber bundle that will become the central thread in the central region of the flat lightweight member is used for the fiber bundle that will become the central thread.

11. A method for manufacturing a flat, lightweight member according to any one of claims 5 to 10, characterized in that both the fiber bundle that forms the central thread and the fiber bundle that forms the braided thread constituting the braiding base material are dry fiber bundles.

12. A method for manufacturing a flat, lightweight member according to any one of claims 5 to 10, characterized in that both the fiber bundle that forms the central thread and the fiber bundle that forms the braided thread constituting the braiding base material are prepregs containing resin.

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