Fiber reinforced plastic structure

Abstract

To provide a fiber reinforced plastic structure that suppresses anisotropy of mechanical characteristics while having excellent lightweightness and mechanical characteristics, and further has excellent fluid permeability.SOLUTION: A fiber reinforced plastic structure has a bicontinuous structure consisting of: a continuous three-dimensional skeleton formed by bonding and integrating a plurality of fiber reinforced plastic pieces together; and a continuous space being an area where the three-dimensional skeleton does not exist.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a structure made of fiber-reinforced plastic pieces. [Background technology]

[0002] Fiber-reinforced plastics are materials with excellent mechanical properties and light weight, and are primarily used as components for aircraft, automobiles, and other applications. In recent years, fiber-reinforced plastic materials with porous structures formed by forming voids within the fiber-reinforced plastic have come into use to further enhance the excellent lightness of fiber-reinforced plastics. For example, Patent Document 1 discloses a structure consisting of resin, reinforcing fibers, and voids. By forming voids within the structure by raising the reinforcing fibers, the structure is characterized by superior lightness and rigidity compared to conventional fiber-reinforced plastic materials. Patent Document 2 also discloses a fluid-permeable member that includes discontinuous reinforcing fibers, a thermoplastic resin, and voids that are communicating holes, and in which the orientation angles of the discontinuous reinforcing fibers in both the in-plane and out-of-plane directions are specified. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 110528 [Patent Document 2] International Publication No. 2019 / 065625 Summary of the Invention [Problem to be solved by the invention]

[0004] The mechanical properties of fiber-reinforced plastics are significantly affected by the orientation direction of the reinforcing fibers, resulting in anisotropy, i.e., the mechanical properties vary depending on the direction. However, in order to apply fiber-reinforced plastics to a wider range of fields, it is preferable for them to have three-dimensionally isotropic mechanical properties so that they can withstand loads in all directions. Furthermore, it is preferable for them to have lightweight properties due to their porous structure, and furthermore, the fluid permeability due to the continuous internal voids is desirable, as this allows for potential applications different from those of conventional fiber-reinforced plastics.

[0005] The fiber-reinforced composite material described in Patent Document 1 produces a lightweight composite material, but because it uses a reinforcing fiber mat, it has a structure in which the reinforcing fibers are biased in the in-plane direction, resulting in a large difference in mechanical properties between the in-plane and out-of-plane directions (anisotropy), which is a problem.In addition, the liquid-permeable member described in Patent Document 2 specifies the orientation of the reinforcing fibers in the in-plane and out-of-plane directions, but still has anisotropy in the mechanical properties.

[0006] The present invention aims to solve the above problems, and has as its object to provide a fiber-reinforced plastic structure that is lightweight and has excellent mechanical properties, while suppressing the anisotropy of the mechanical properties and further having excellent fluid permeability. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a fiber-reinforced plastic structure having a co-continuous structure consisting of a three-dimensional skeletal structure formed by bonding and integrating multiple fiber-reinforced plastic pieces together, and a space as an area where the three-dimensional skeletal structure does not exist. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a fiber-reinforced plastic structure that is lightweight, has excellent mechanical properties, suppresses anisotropy in the mechanical properties, and has excellent fluid permeability. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing a structural schematic diagram of a fiber-reinforced plastic structure of the present invention. FIG. [Figure 2] 1 is a diagram illustrating an example of a fiber-reinforced plastic piece of the present invention. [Figure 3] 1 is a diagram showing an example of a cross section of a fiber-reinforced plastic structure of the present invention. [Figure 4] FIG. 1 is a diagram showing a schematic diagram of a method for evaluating fluid permeability. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the present invention will now be described. [Fiber reinforced plastic structure] The fiber-reinforced plastic structure of the present invention is a fiber-reinforced plastic structure having a co-continuous structure consisting of a continuous three-dimensional skeletal structure formed by bonding and integrating a plurality of fiber-reinforced plastic pieces together, and a continuous space which is a region where the three-dimensional skeletal structure does not exist. A schematic diagram of the fiber-reinforced plastic structure of the present invention is shown in Figure 1. The fiber-reinforced plastic structure 1 of the present invention has a three-dimensional skeletal structure 3 formed by bonding and integrating a plurality of fiber-reinforced plastic pieces 2 together. In addition, there is a space 4 which is a region where the three-dimensional skeletal structure 3 does not exist, and the three-dimensional skeletal structure 3 and the space 4 form a co-continuous structure.

[0011] A first feature of the fiber-reinforced plastic structure of the present invention is that it has a three-dimensional skeletal structure formed by bonding and integrating multiple fiber-reinforced plastic pieces together. This configuration maximizes the reinforcing effect of the reinforcing fibers, resulting in a lightweight structure with excellent mechanical properties. Furthermore, the materials forming the skeleton (reinforced fibers and matrix resin) can be locally concentrated, suppressing interference between skeletons and increasing the degree of freedom of the skeleton structure, thereby suppressing anisotropy in the mechanical properties. A second feature is that the fiber-reinforced plastic structure has a co-continuous structure consisting of a three-dimensional skeletal structure and voids. This configuration allows large-scale continuous voids to be formed inside the fiber-reinforced plastic structure, resulting in lightweight construction and high fluid permeability. [Fiber-reinforced plastic piece] The fiber-reinforced plastic piece of the present invention will be described with reference to Fig. 2. The fiber-reinforced plastic piece 2 is a fiber-reinforced plastic containing a plurality of reinforcing fibers 5 and a matrix resin 6, and has a volume of 1 cm 3 It refers to the following:

[0012] The reinforcing fibers contained in the fiber-reinforced plastic pieces are not particularly limited, and examples thereof include carbon fibers, glass fibers, aramid fibers, alumina fibers, silicon carbide fibers, boron fibers, metal fibers, natural fibers, mineral fibers, etc., and two or more of these may be used in combination. Among these, PAN-based, pitch-based, rayon-based, and other carbon fibers are preferably used because of their high specific strength, specific rigidity, and excellent weight reduction effect.

[0013] The matrix resin contained in the fiber-reinforced plastic pieces is not particularly limited, and thermosetting resins, thermoplastic resins, copolymers thereof, etc. can be used. Multiple resins may also be mixed. As a thermosetting resin, epoxy resin is particularly preferred from the viewpoint of the mechanical properties and heat resistance of the molded article. As a thermoplastic resin, polyolefin is preferred from the viewpoint of the light weight of the resulting molded article, polyamide is preferred from the viewpoint of strength, polyarylene sulfide is preferred from the viewpoint of heat resistance, polyether ether ketone is preferred from the viewpoint of continuous use temperature, and fluorine-based resin is preferred from the viewpoint of chemical resistance. In the present invention, if the main component of a matrix resin (a component that accounts for more than 50% by weight when the entire matrix is taken as 100% by weight), it is called a thermoplastic resin, and if it is a thermosetting resin, it is called a thermosetting resin.

[0014] In the fiber-reinforced plastic piece of the present invention, the reinforcing fibers may be contained in the form of continuous fibers that have no ends inside the fiber-reinforced plastic piece, or in the form of discontinuous fibers that have ends inside the fiber-reinforced plastic piece, or both of the continuous fibers and the discontinuous fibers may be contained. From the viewpoints of light weight and mechanical properties, it is preferable that the reinforcing fibers be contained in the form of continuous fibers.

[0015] In the fiber-reinforced plastic piece of the present invention, the orientation direction of the reinforcing fibers is not particularly limited, but it is preferable that the reinforcing fibers are oriented in one direction. By adopting such a configuration, the fiber volume content of the fiber-reinforced plastic piece can be increased and the reinforcing effect of the reinforcing fibers can be enhanced.

[0016] The fiber-reinforced plastic piece of the present invention may have a laminated structure in which a plurality of layers formed of groups of reinforcing fibers in which the reinforcing fibers are oriented in substantially the same direction are laminated.

[0017] In the fiber-reinforced plastic piece of the present invention, the reinforcing fibers may have a woven structure. The woven structure is not particularly limited, but typical woven structures include plain weave, satin weave, and twill weave.

[0018] The shape of the fiber-reinforced plastic piece of the present invention is not particularly limited. Examples of the shape of the fiber-reinforced plastic piece are shown in Figure 2. For example, the shape may be cylindrical as shown in Figure 2(a), prismatic as shown in Figure 2(b), or irregular as shown in Figure 2(c), but is not limited to these.

[0019] The fiber-reinforced plastic pieces contained in the three-dimensional skeletal structure of the present invention preferably have an average maximum dimension of 100 mm or less. Here, the maximum dimension refers to the maximum distance between two imaginary points on the surface of the fiber-reinforced plastic piece. This configuration is preferable because it suppresses interference between the fiber-reinforced plastic pieces and forms a three-dimensional skeletal structure with suppressed anisotropy. To calculate the average maximum dimension, ten fiber-reinforced plastic pieces contained in the three-dimensional skeletal structure are randomly selected, the maximum dimension of each is measured, and the average value is used. The method for measuring the maximum dimension is not particularly limited, but examples include a method of obtaining three-dimensional structural data by X-ray CT scanning of the fiber-reinforced plastic structure and measuring it, or a method of measuring it using vernier calipers.

[0020] The fiber-reinforced plastic pieces contained in the three-dimensional skeletal structure of the present invention preferably have an average fiber volume content of 30% or more and 70% or less. The fiber volume content here refers to the ratio of the volume of the reinforcing fibers contained in the fiber-reinforced plastic pieces to the volume of the fiber-reinforced plastic pieces. This configuration enhances the reinforcing effect of the three-dimensional skeletal structure, resulting in a fiber-reinforced plastic structure with excellent mechanical properties. Furthermore, since the reinforcing fibers contained in the fiber-reinforced plastic structure can be locally concentrated, interference between the fiber-reinforced plastic pieces is reduced, suppressing anisotropy in the mechanical properties. Furthermore, since the size of the space can be increased while maintaining the number of reinforcing fibers, fluid permeability can be improved. The fiber volume content is more preferably 50% or more, and even more preferably 60% or more. The method for measuring the fiber volume content is not particularly limited. For example, a cross-sectional image of an arbitrary cross section of the fiber-reinforced plastic structure may be obtained, a cross section of a fiber-reinforced plastic piece may be selected from the cross-sectional image, and a value calculated by (the sum of the areas of the reinforcing fiber cross sections present in the cross section of the selected fiber-reinforced plastic piece) / (the area of the cross section of the selected fiber-reinforced plastic piece) × 100 [%] may be used. In this case, at least 10 cross sections of the fiber-reinforced plastic piece should be selected, and the average fiber volume content calculated for each of them should be used. When selecting the cross section of the fiber-reinforced plastic piece, if the reinforcing fibers are oriented obliquely to the cross section, the shape of the reinforcing fiber cross section may be distorted, making measurement difficult. Therefore, it is preferable to select a cross section of a fiber-reinforced plastic piece containing reinforcing fibers oriented nearly perpendicular to the cross section. A guideline for the reinforcing fibers being oriented nearly perpendicular to the cross section is that when the shape of the reinforcing fiber cross section is approximated to an ellipse, the ratio of the major axis to the minor axis of the ellipse is 1.2 or less.

[0021] The fiber-reinforced plastic pieces of the present invention are preferably crushed fiber-reinforced plastic. This form is preferable because, even if the volume of the fiber-reinforced plastic pieces is very small, they become fiber-reinforced plastic pieces in which the matrix resin sufficiently impregnates the reinforcing fibers, resulting in a skeletal structure with excellent mechanical properties. Furthermore, since an irregularly textured shape is formed on the surface of the fiber-reinforced plastic pieces, the fiber-reinforced plastic pieces are bonded to each other via the surfaces on which the textured shape is formed, thereby achieving stronger bonding between the pieces. Furthermore, this is preferable because it allows existing fiber-reinforced plastics to be reused to obtain a fiber-reinforced plastic structure, thereby reducing the environmental impact of production. The crushed pieces may be subjected to a heat treatment to treat the surface of the crushed pieces or remove part of the matrix resin.

[0022] [Bonding fiber-reinforced plastic pieces together] The fiber-reinforced plastic structure of the present invention has a three-dimensional skeletal structure formed by bonding and integrating a plurality of fiber-reinforced plastic pieces together. The fiber-reinforced plastic pieces may be bonded together by a matrix resin contained in the fiber-reinforced plastic pieces, or may be bonded by a resin different from the matrix resin (hereinafter, sometimes referred to as adhesive resin 7), as shown in FIG. 1. The type of adhesive resin is not particularly limited, and the same resin as the resin that can be used as the matrix resin described above can be used, and it may be the same resin as the matrix resin or a different resin. When the fiber-reinforced plastic pieces are bonded together by an adhesive resin, not only can the fiber-reinforced plastic pieces be firmly bonded together, but also a fillet structure due to the adhesive resin can be formed at the bonded portions between the fiber-reinforced plastic pieces, resulting in a three-dimensional skeletal structure with excellent mechanical properties, which is preferable.

[0023] [3D skeletal structure] The fiber-reinforced plastic structure of the present invention has a three-dimensional skeletal structure formed by bonding and integrating multiple fiber-reinforced plastic pieces. The three-dimensional skeletal structure is a structure in which the skeletal structure formed by bonding and integrating fiber-reinforced plastic pieces extends three-dimensionally, and is lightweight yet has excellent mechanical properties, and further exhibits mechanical properties with suppressed anisotropy. Here, "three-dimensional" refers to a state in which there is no imaginary plane in which all of the fiber-reinforced plastic pieces contained in the skeletal structure come into contact.

[0024] [space] The fiber-reinforced plastic structure of the present invention has a space as a region where the three-dimensional skeletal structure is not present, and at least a portion of the space may be filled with a substance such as a gas, a fluid, or a solid.

[0025] [Co-continuous structure] The fiber-reinforced plastic structure of the present invention has a co-continuous structure consisting of the three-dimensional skeletal structure and the voids. A co-continuous structure refers to a state in which the continuous three-dimensional skeletal structure and the continuous voids are present in a common region without overlapping each other. There are no particular limitations on the method for confirming that a fiber-reinforced plastic structure has a co-continuous structure. For example, if it can be confirmed that gas or liquid can pass through the interior of the fiber-reinforced plastic structure, the fiber-reinforced plastic structure is considered to have a co-continuous structure.

[0026] [others] The fiber-reinforced plastic structure of the present invention preferably has a porosity of 50% or more and 99% or less. Here, the porosity refers to the ratio of the volume of the voids to the apparent volume of the fiber-reinforced plastic structure. This configuration ensures that the volume of the voids in the fiber-reinforced plastic structure is sufficient, resulting in a fiber-reinforced plastic structure with excellent fluid permeability and lightweight properties. There are no particular limitations on the method for measuring the porosity. For example, the porosity may be calculated by measuring the volume of the three-dimensional skeletal structure and the voids from three-dimensional data obtained by X-ray CT scanning the fiber-reinforced plastic structure. Alternatively, an arbitrary cross-sectional image of the fiber-reinforced plastic structure may be acquired and the value calculated using the formula: (area of the cross section where the voids are exposed) / (sum of the area of the cross section of the three-dimensional skeletal structure and the cross section where the voids are exposed) × 100 [%] may be used. A more preferred porosity is 70% or more, and even more preferably 80% or more.

[0027] The fiber-reinforced plastic structure of the present invention has a density of 0.1 g / cm 3 More than 0.9g / cm 3 It is preferable that the following is true: By adopting such a configuration, a fiber reinforced plastic structure having excellent light weight can be obtained.

[0028] The fiber-reinforced plastic structure of the present invention preferably has a compression modulus ratio (the highest compression modulus / the lowest compression modulus) of 1.5 or less among the compression moduli obtained from a compression test in three mutually perpendicular directions. This configuration results in a fiber-reinforced plastic structure with reduced anisotropy in mechanical properties. When the anisotropy in mechanical properties is large, the structure may deform significantly when a load is applied in a specific direction, resulting in a change in fluid permeability. However, a compression modulus ratio of 1.5 or less results in a fiber-reinforced plastic structure with minimal change in fluid permeability due to load. A more preferred range for the compression modulus ratio is 1.3 or less, and even more preferably 1.1 or less. The method for measuring the compression modulus is specifically described below. The compression modulus of the present invention is determined by performing a compression test in which a cubic measurement sample made of a fiber-reinforced plastic structure is compressed in three mutually perpendicular directions, and using the resulting stress-strain diagram, the highest value of the compression modulus calculated from the slope at a strain amplitude of 0.1% within a strain range of 0 to 1% is used. In this case, it is preferable to obtain the compression modulus in the three directions using the same measurement sample. In this case, the compression test must be repeated within a range that does not damage the measurement sample, so the maximum load applied in the compression test can be set arbitrarily. If the resulting strain is less than 1%, the highest value of the compressive elastic modulus calculated from the slope at a strain width of 0.1% within the range of the strain that occurred can be used. In the fiber-reinforced plastic structure of the present invention, the three-dimensional skeletal structure is preferably formed from fiber-reinforced plastic pieces in which the reinforcing fibers are oriented in one direction, and the three-dimensional fiber-reinforced plastic structure preferably includes reinforcing fibers such that, in each cross section formed by three mutually orthogonal planes of the three-dimensional fiber-reinforced plastic structure, the average angle α formed by the orientation directions of the reinforcing fibers projected onto the corresponding plane is 20° or greater. When the average angle α is 20° or greater in all three cross sections formed by the three mutually orthogonal planes, a fiber-reinforced plastic structure with suppressed anisotropy in mechanical properties is obtained. Here, a method for measuring the average angle α will be explained using FIG. 3. FIG. 3 is a schematic diagram of a cross section of the fiber-reinforced plastic structure of the present invention. A cross section 8 of the fiber-reinforced plastic structure has at least a fiber-reinforced plastic piece cross section 9 and a spatial cross section 10, each of which is composed of reinforcing fibers 5 and a matrix resin 6. Here, when the cross-sectional shape of the reinforcing fibers 5 is approximated to an ellipse, the direction along the major axis of the ellipse is considered to be the orientation direction of the reinforcing fibers projected onto the plane corresponding to the cross section. First, an arbitrary reinforcing fiber cross section in the cross section is selected as the "reference reinforcing fiber cross section 11." Next, a reinforcing fiber cross section belonging to a fiber-reinforced plastic piece different from the "reference reinforcing fiber cross section 11" is selected as the "reference reinforcing fiber cross section 12." Next, the acute angle 13 between the direction along the major axis of the ellipse of the "reference reinforcing fiber cross section 11" and the direction along the major axis of the ellipse of the "reference reinforcing fiber cross section 12" is calculated as the angle between the orientation directions of the reinforcing fibers projected onto a plane corresponding to the cross section. This operation is performed for a total of 10 different "reference reinforcing fiber cross sections 12" using the same "reference reinforcing fiber cross section 11," and the average of the obtained angles is used as the average angle α of the present invention. Note that it is preferable that the total of 10 "reference reinforcing fiber cross sections 12" are selected from different fiber-reinforced plastic piece cross sections 9. A more preferable average angle α is 30° or more, and more preferably 40° or more.

[0029] [Application] The fiber-reinforced plastic structure of the present invention is lightweight, has excellent rigidity, suppresses anisotropy in mechanical properties, and further has excellent fluid permeability. These characteristics make it suitable for use in lightweight structural materials, impact absorbers, heat insulators, reinforcing materials, filters, catalyst carriers, flow straightening materials, planting bases, and the like. [Example]

[0030] The present invention will be described in more detail below with reference to examples.

[0031] <Evaluation method> (1) Method for measuring the average value of the maximum dimension of fiber-reinforced plastic pieces The maximum dimensions of the fiber-reinforced plastic pieces used in the examples were measured using a vernier caliper. The maximum dimensions of a total of 10 randomly selected fiber-reinforced plastic pieces were measured, and the average value was calculated. (2) Method for measuring the fiber volume content of fiber-reinforced plastic pieces An arbitrary cross-sectional image of the fiber-reinforced plastic structure produced in the examples was taken, and a total of 10 cross-sections of fiber-reinforced plastic pieces were selected from the cross-sectional image. For each cross-section of the fiber-reinforced plastic piece, the fiber volume content was calculated by (sum of the areas of the cross-sections of the reinforcing fibers present in the cross-section of the selected fiber-reinforced plastic piece) / (area of the cross-section of the selected fiber-reinforced plastic piece) × 100 [%], and the average value of these was used. (3) Method for measuring porosity of fiber-reinforced plastic structures An arbitrary cross-sectional image of the fiber-reinforced plastic structure produced in the examples was obtained, and the area of the cross section where the space is exposed was calculated by dividing the area of the cross section of the three-dimensional skeletal structure and the area of the cross section where the space is exposed by 100%. (4) Method for measuring the density of fiber-reinforced plastic structures The weight [g] of the fiber-reinforced plastic structure manufactured in the examples was measured using an electronic balance, and the apparent volume [cm 3 ] was used. (5) Average angle α Calculated using the method described above. (6) Mechanical evaluation Compression tests were performed on the test specimens using an Instron (registered trademark) Model 5565 universal material testing machine (manufactured by Instron Japan Co., Ltd.). The test specimens were cubes with sides measuring 1 cm, and compression tests were performed on the same specimens in three orthogonal directions, applying loads of 0 to 50 N. The compressive modulus for each compression direction was calculated from the slope of the resulting stress-strain curve, and the compressive modulus ratio was calculated as (highest compressive modulus) / (lowest compressive modulus). The closer the compressive modulus ratio value is to 1, the smaller the anisotropy of the elastic modulus and the more excellent the isotropy. (7) Fluid permeability evaluation The method for evaluating fluid permeability will be explained using Figure 4. A disk-shaped test piece 15, 5 mm thick and 20 mm in diameter, was placed on the bottom of a container 14, which had a hole with a diameter of 10 mm, so as to cover the hole, and was then covered with a waterproofing material 16. Next, 100 mL of water was poured into the container at a temperature of 23°C, and the time (seconds) until the poured water passed through the test piece under its own weight and was completely drained out of the hole was measured. The shorter the measurement time, the better the fluid permeability was evaluated.

[0032] <Material Preparation> [Fiber reinforced plastic piece material] Prepreg 1 Torayca (registered trademark) prepreg P3252S-10 manufactured by Toray Industries, Inc. was used as the material for the fiber reinforced plastic pieces. [Fiber reinforced plastic that is the source of fiber reinforced plastic pieces] Fiber-reinforced plastics 1 Prepreg 1 was cut into a size of 300 mm x 300 mm and laminated in a lamination configuration of [0° / 90° / 90° / 0°], where the orientation direction of the reinforcing fibers contained in the outermost prepreg was 0°, to obtain a laminate. Next, the laminate was heated at a temperature of 150°C and a pressure of 1 MPa for 20 minutes using a press molding machine to harden the resin, thereby obtaining fiber-reinforced plastic 1. Fiber-reinforced plastics 2 Prepreg 1 was cut into a size of 300 mm x 300 mm and laminated in a lamination configuration of [0° / 0° / 0° / 0°], where the orientation direction of the reinforcing fibers contained in the outermost prepreg was 0°, to obtain a laminate. Next, the laminate was heated at a temperature of 150°C and a pressure of 1 MPa for 20 minutes using a press molding machine to harden the resin, thereby obtaining fiber-reinforced plastic 2.

[0033] [Fiber-reinforced plastic piece] 1 piece of fiber-reinforced plastic The fiber reinforced plastic 1 was cut using a cutter to obtain fiber reinforced plastic pieces 1 as cut pieces. 2 pieces of fiber-reinforced plastic The fiber reinforced plastic 2 was cut using a cutter to obtain fiber reinforced plastic pieces 2 as cut pieces. 3 pieces of fiber-reinforced plastic The fiber reinforced plastic 2 was cut using a cutter, and then pressed using upper and lower dies to be crushed by the pressure of the press, thereby obtaining crushed fiber reinforced plastic pieces 3.

[0034] [Carbon fiber nonwoven fabric] A copolymer primarily composed of polyacrylonitrile was spun, calcined, and surface-oxidized to obtain a carbon fiber bundle with a total number of 12,000 single fibers. The carbon fiber bundle was then cut into 6 mm lengths using a cartridge cutter to obtain chopped carbon fiber. A 0.1% by mass dispersion consisting of water and a surfactant (Nacalai Tesque, Inc., Polyoxyethylene Lauryl Ether (trade name)) was prepared, and a carbon fiber substrate was produced using this dispersion and chopped carbon fiber. The manufacturing equipment included a cylindrical 1000 mm diameter dispersion tank with an on-off valve at the bottom, and a linear transport section (inclined at 30°) connecting the dispersion tank and papermaking tank. An agitator was attached to the opening on the top of the dispersion tank, allowing chopped carbon fiber and dispersion liquid (dispersion medium) to be added through the opening. The papermaking tank was equipped with a mesh conveyor with a 500 mm wide papermaking surface at the bottom, and a conveyor capable of transporting the carbon fiber substrate (papermaking substrate) was connected to the mesh conveyor. The carbon fiber concentration in the dispersion was 0.05% by mass. The carbon fiber substrate was dried in a drying oven at 200°C for 30 minutes to obtain a carbon fiber nonwoven fabric in which the orientation directions of the carbon fiber monofilaments were dispersed in multiple directions. In the carbon fiber nonwoven fabric, the mass of carbon fiber per unit area was 100 g / m. 2 It was.

[0035] [Adhesive resin] ·Adhesive resin 1 "ADEKA RESIN" EM-0434AN manufactured by ADEKA Corporation was used as adhesive resin 1. This product is a one-component curing epoxy resin emulsion, and is a thermosetting resin.

[0036] <Method of manufacturing fiber-reinforced plastic structures> First, 5 g of any of the fiber reinforced plastic pieces 1 to 3 was placed in a container having an aluminum cylinder with a diameter of 3 cm, the bottom of which was provided with a wire mesh and the top of which was open.

[0037] Next, adhesive resin 1 was poured into the opening of the container until the fiber-reinforced plastic pieces were completely immersed, and after stirring the contents, excess adhesive resin 1 was drained through the wire mesh at the bottom, yielding fiber-reinforced plastic pieces with adhesive resin 1 attached.

[0038] Next, the container was placed in an oven set at 80°C and dried for 1 hour, and then the temperature was raised to 180°C and left to stand for 1 hour, curing the adhesive resin 1 and bonding the fiber-reinforced plastic pieces together to obtain a fiber-reinforced plastic structure.

[0039] Example 1 The fiber-reinforced plastic piece 3 was used as the fiber-reinforced plastic piece, and a fiber-reinforced plastic structure was manufactured by the above-mentioned method for manufacturing a fiber-reinforced plastic structure.

[0040] The obtained fiber-reinforced plastic structure was processed to obtain test specimens for mechanical evaluation and fluid permeability evaluation.

[0041] The obtained test specimens were subjected to porosity measurement, density measurement, mechanical evaluation, and permeability evaluation, and the results shown in Table 1 were obtained.

[0042] Example 2 A fiber-reinforced plastic structure was produced in the same manner as in Example 1, except that Fiber-reinforced plastic piece 1 was used as the fiber-reinforced plastic piece, and the fiber-reinforced plastic structure was obtained and processed into a test piece, and various measurements and evaluations were performed. The results shown in Table 1 were obtained.

[0043] Example 3 A fiber-reinforced plastic structure was produced in the same manner as in Example 1, except that fiber-reinforced plastic piece 2 was used as the fiber-reinforced plastic piece, and the fiber-reinforced plastic structure was obtained and processed into a test piece, and various measurements and evaluations were performed. As a result, the results shown in Table 1 were obtained.

[0044] Example 4 In the manufacturing process of the fiber-reinforced plastic structure, a fiber-reinforced plastic structure was manufactured in the same manner as in Example 1, except that after the excess adhesive resin 1 was discharged, the fiber-reinforced plastic pieces with adhesive resin 1 attached were compressed and densified. The fiber-reinforced plastic structure was obtained and processed into test pieces, and various measurements and evaluations were carried out. The results shown in Table 1 were obtained.

[0045] (Comparative Example 1) A wire mesh was placed on the bottom of an aluminum cylinder with a diameter of 3 cm, and 10 sheets of carbon fiber nonwoven fabric cut into circles with a diameter of 3 cm were layered on top of the wire mesh in a container with an open top.

[0046] Next, adhesive resin 1 was poured into the container from the opening and allowed to soak into the carbon fiber nonwoven fabric, and excess adhesive resin 1 was drained through the wire mesh at the bottom.

[0047] Next, the container was placed in an oven set at 80°C and dried for 1 hour, and then the temperature was increased to 180°C and left to stand for 1 hour to harden the adhesive resin 1 and obtain a fiber-reinforced plastic structure.

[0048] The obtained fiber reinforced plastic structure had a co-continuous structure consisting of a network structure in which carbon fiber monofilaments were bonded with adhesive resin 1 and continuous spaces.

[0049] The resulting fiber-reinforced plastic structure was used to obtain test specimens for mechanical evaluation and fluid permeability evaluation.

[0050] The obtained test specimens were subjected to porosity measurement, density measurement, mechanical evaluation, and permeability evaluation, and the results shown in Table 1 were obtained.

[0051] [Table 1]

[0052] The mechanical evaluation results showed that the elastic modulus ratio of Comparative Example 1 was 10, indicating very high anisotropy. It is presumed that the carbon fibers forming the carbon fiber nonwoven fabric were oriented two-dimensionally, which resulted in differences in the reinforcing effect of the reinforcing fibers depending on the direction of the load. Furthermore, the fluid permeability evaluation results showed that water did not completely permeate even after 1 hour had passed since the water was introduced, making it impossible to evaluate the fluid permeability. [Explanation of symbols]

[0053] 1: Fiber reinforced plastic structure 2: Fiber-reinforced plastic piece 3: Three-dimensional skeletal structure 4: Space 5: Reinforced fiber 6: Matrix resin 7:Adhesive resin 8: Fiber-reinforced plastic structure cross section 9: Cross section of fiber reinforced plastic piece 10: Spatial cross section 11: Standard reinforcing fiber cross section 12: Reference reinforcing fiber cross section 13: The angle between the directions along the major axis of the ellipse 14: Container for fluid permeability evaluation 15: Disc-shaped test piece 16: Waterproof material

Claims

1. A fiber-reinforced plastic structure having a co-continuous structure consisting of a continuous three-dimensional skeletal structure formed by bonding and integrating multiple fiber-reinforced plastic pieces together, and a continuous space that is an area where the three-dimensional skeletal structure does not exist.

2. The fiber-reinforced plastic structure according to claim 1, wherein the porosity is 50% or more and 99% or less.

3. The fiber-reinforced plastic structure according to claim 1, wherein the average fiber volume content of the fiber-reinforced plastic pieces is 30 to 70%.

4. Density is 0.1 to 0.9 g / cm ３ The fiber-reinforced plastic structure according to claim 1,

5. 2. The fiber-reinforced plastic structure according to claim 1, wherein the compressive modulus ratio, expressed as the highest compressive modulus / the lowest compressive modulus among the compressive moduli obtained from compression tests in three mutually perpendicular directions, is 1.5 or less.

6. The fiber-reinforced plastic structure of claim 1 , comprising fiber-reinforced plastic pieces in which the reinforcing fibers are oriented in one direction.

7. 7. The fiber-reinforced plastic structure according to claim 6, wherein the three-dimensional skeletal structure includes reinforcing fibers in each cross section formed by three mutually perpendicular planes, the average value α of the angle formed by the orientation directions of the reinforcing fibers projected onto the corresponding planes being 20° or more.

8. The fiber-reinforced plastic structure according to claim 1, wherein the average maximum dimension of the fiber-reinforced plastic pieces is 100 mm or less.

9. The fiber-reinforced plastic structure according to claim 1 , wherein the fiber-reinforced plastic pieces are crushed fiber-reinforced plastic pieces.

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