Honeycomb members and skin-core structures

Abstract

We provide a honeycomb component made of a fiber-reinforced composite material that achieves both lightweight properties and shock absorption characteristics. [Solution] A honeycomb member having a structure consisting of an aggregate of hollow columnar cells partitioned by cell walls, wherein the cell walls are made of a fiber-reinforced composite material containing organic fibers and inorganic fibers, and a resin, and the fiber diameter of the organic fibers is 5 to 25 μm.

Description

[Technical Field]

[0001] This invention relates to a honeycomb member used in a skin-core structure. [Background technology]

[0002] Skin-core structures, which use a core material consisting of an aggregate of hollow, columnar cells partitioned by cell walls, are widely used as structural members and building materials for aircraft and ships due to their excellent mechanical properties such as light weight and high rigidity. These core materials include aluminum honeycomb cores made of aluminum foil and FRP honeycomb cores made of reinforcing fibers and matrix resin. Among these, aramid honeycomb cores, made by impregnating aramid fiber nonwoven fabric with phenolic resin, are primarily used in aircraft and other flying objects where weight reduction is a strong requirement. Furthermore, from the viewpoint of mechanical properties and light weight, the development of FRP honeycomb cores using carbon fiber as reinforcing fiber is also progressing (Patent Documents 1 and 2). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2023 / 167334 [Patent Document 2] Japanese Patent Publication No. 2019-155850 [Overview of the project] [Problems that the invention aims to solve]

[0004] FRP honeycomb structures using nonwoven fabrics made of carbon fibers, as described in Patent Documents 1 and 2, can achieve both lightweight properties and improved mechanical properties. On the other hand, FRP honeycomb structures have the drawback of having lower impact absorption properties compared to aluminum honeycomb structures. Patent Documents 1 and 2 do not specify any particular effects regarding the improvement of impact absorption properties, and improvement of impact absorption properties is needed. The object of the present invention is to provide a honeycomb member made of a fiber-reinforced composite material that achieves both lightweight properties and impact absorption properties. [Means for solving the problem]

[0005] To solve the above problems, the present invention provides a honeycomb member having a structure consisting of an aggregate of hollow columnar cells partitioned by cell walls, wherein the cell walls are made of a fiber base material consisting of organic fibers and inorganic fibers, and a fiber-reinforced resin composite material containing resin, and the fiber diameter of the organic fibers is 5 to 25 μm. Another aspect of the present invention is a skin-core structure formed by bonding the honeycomb member described above with a skin material. [Effects of the Invention]

[0006] The present invention makes it possible to obtain honeycomb members and skin-core structures that achieve a high level of both shock absorption properties and lightweight properties. [Brief explanation of the drawing]

[0007] [Figure 1] A schematic diagram showing one embodiment of the honeycomb member of the present invention. [Figure 2] A schematic diagram showing one embodiment of the sandwich structure of the present invention. [Modes for carrying out the invention]

[0008] <Honeycomb material> The honeycomb member of the present invention will be described below with reference to the drawings as appropriate, but the present invention is not limited to these drawings. However, as will be easily understood by those skilled in the art, the description of the embodiments shown in the drawings can also function as a description of the honeycomb member of the present invention as a broader concept.

[0009] FIG. 1 is a schematic view showing an embodiment of the honeycomb member of the present invention together with an enlarged view of the cell wall. The honeycomb member 1 has a structure composed of an aggregate of a large number of hollow columnar cells (hereinafter sometimes referred to as "columnar cells") partitioned by cell walls 5. The cell wall 5 is made of a fiber reinforced composite material containing a fiber base material composed of organic fibers 2 and inorganic fibers 3 and a resin 4. And as shown in the enlarged view in FIG. 1, the cell wall 5 made of the fiber reinforced composite material is composed of a fiber base material coated with the resin 4.

[0010] The organic fiber used in the material of the present invention has a fiber diameter of 5 to 25 μm. By setting the range in this way, the load-bearing capacity of the organic fiber becomes sufficiently large, fiber breakage due to impact load can be sufficiently suppressed, the honeycomb member has high impact absorption characteristics and also has light weight. When the upper limit value of such a range is exceeded, the thin cell wall becomes non-uniform, and it becomes difficult to exhibit sufficient impact absorption characteristics.

[0011] Further, it is preferable that the organic fiber and the resin satisfy any one of the following (A) to (D). (A) The melting point of the organic fiber is higher than the melting point of the resin. (B) The melting point of the resin does not exist, and the melting point of the organic fiber is higher than the glass transition temperature of the resin + 100 °C. (C) The organic fiber does not have a melting point, and the glass transition temperature of the organic fiber + 50 °C is higher than the melting point of the resin. (D) The organic fiber and the resin do not have a melting point, and the glass transition temperature of the organic fiber is higher than the glass transition temperature of the resin. By satisfying any of these conditions, it becomes easier for the organic fiber to exist in the cell wall while maintaining the fiber form. When the organic fiber exists in the fiber form in the cell wall, the number of contact points increases due to the entanglement of the fibers including the inorganic fibers, forming a dense structure, and contributes to the expression of impact absorption characteristics due to the pulling out from the resin.

[0012] Among the above conditions, it is preferable that the melting point or glass transition temperature + 100 °C of the resin is 20 to 200 °C higher than the melting point or glass transition temperature + 50 °C of the organic fiber, more preferably 30 to 180 °C higher, and even more preferably 50 to 160 °C higher. By setting the range as such, the resin can be impregnated into the fiber base material within the temperature range where the organic fiber is not melted and the fiber form is maintained during molding. The melting point and glass transition temperature of the organic fiber and resin of the present invention can be measured by a differential scanning calorimeter (DSC) based on JIS K7121 (2012). Pack 1 to 10 mg of the organic fiber or resin taken out from the honeycomb member into a sealed sample container with a volume of 50 μl, heat it at a heating rate of 10 °C / min, and use the step of the DSC curve detected in the range of 30 to 400 °C as the glass transition temperature and the exothermic peak as an index of the melting point, and set the respective temperatures as the glass transition temperature and the melting point.

[0013] The number average fiber length of the organic fiber is preferably 3 mm or more and 15 mm or less, and the number average fiber length of the inorganic fiber is preferably 2 mm or more and 15 mm or less. When the number average fiber length of the organic fiber is within such a range, the organic fiber has a large number of contact points with the inorganic fiber and the resin, and when impacted, a large number of resin fractures or pulling out of the organic fiber from the resin will occur, and excellent impact strength can be exhibited. In addition, when the average fiber length of the inorganic fiber is 2 mm or more, the reinforcing effect of the inorganic fiber can be made sufficient, sufficient dispersibility can be obtained even in a thin cell wall, and excellent mechanical properties can be imparted to the cell wall and the honeycomb member. The average fiber length of each fiber can be calculated by removing the resin component by methods such as burning out or elution, randomly selecting 400 from the remaining fibers, measuring their lengths up to the unit of 100 μm, and taking their number average length.

[0014] The tensile elongation at break of an organic fiber is preferably 2.5 to 100%, more preferably 2.5 to 30%, and even more preferably 2.5 to 15%. By keeping it within this range, the breakage of the organic fiber when an impact is applied can be sufficiently suppressed, and excellent impact strength can be provided. The tensile elongation at break (%) of an organic fiber can be determined by the following method: A tensile test is performed on one organic fiber in a room under standard conditions (20°C, 65%RH) with a gripping distance of 250 mm and a tensile speed of 300 mm / min. The length at which the fiber breaks is measured (however, if the fiber breaks near the chuck, it is treated as a chuck break and excluded from the data), and the result is calculated to two decimal places using the following formula, and the second decimal place is rounded. The average value of n=3 data points in this measurement is taken as the tensile elongation at break. Tensile elongation at break (%) = [(Length at break (mm) - 250) / 250] × 100

[0015] Examples of organic fibers used in the present invention include polyolefin resins such as polyethylene and polypropylene, polyamide resins such as nylon 6, nylon 66, and aromatic polyamide, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and liquid crystal polyester, polyaryl ether ketone resins such as polyether ketone, polyethersulfone, polyarylene sulfide, polyetherimide, polycarbonate, and fluororesin. Two or more of these may be used in combination. In particular, from the viewpoint of suppressing fiber breakage during impact, the organic fiber of the present invention is preferably selected from polyolefin resins, polyester resins, aromatic polyamide resins, polyaryl ether ketone resins, polyetherimide resins, polycarbonate resins, cellulose fibers such as cellulose nanofibers, and polyarylene sulfide resins. Examples of organic fibers made from polyester resins include "Tetron" (registered trademark) and "Trecon" manufactured by Toray Industries, Inc., and "Ecopet" (registered trademark) manufactured by Teijin Frontier Co., Ltd. Examples of organic fibers made from aromatic polyamide resins include DuPont's "Kevlar" (registered trademark) and "Nomex" (registered trademark), and Teijin Limited's "Technora" (registered trademark). Examples of fibers made from polyaryletherketone resins include VICTREX's PEEK fiber and Solvay's "Keitaspire" (registered trademark). Examples of organic fibers made from polyetherimide resins include Kuraray's "Kurakis" (registered trademark). Examples of organic fibers made from polyarylene sulfide resins include Toray Industries, Inc.'s "Torcon" (registered trademark).

[0016] It is preferable to use inorganic fibers with a tensile modulus of 100 GPa or higher. By keeping the value within this range, when an external force is applied and the cell wall breaks, the energy absorbed by the crack passing through the inorganic fibers becomes higher, which is advantageous in improving the shock absorption characteristics of the honeycomb member. Examples of fibers with a tensile modulus of 100 GPa or higher include para-aramid fibers, boron fibers, carbon fibers, and graphite fibers. Among these, it is preferable to use carbon fibers, which enhance shock absorption, do not have the water absorption problem that is an issue in aerospace applications, and have excellent strength and modulus. Here, the tensile modulus of the fiber is a value measured in accordance with JIS R7601-2006.

[0017] The basis weight of the fiber base material is 5-80 g / m². 2 This is preferable. By setting the range in this manner, the reinforcing effect of the cell wall can be sufficiently obtained, and the requirement for lightness can also be met.

[0018] The fibrous base material preferably has a volume content of 20-40% organic fibers and 60-80% inorganic fibers. By keeping the content within this range, it is possible to achieve both high mechanical properties due to the inorganic fibers, which generally have excellent tensile properties, and impact absorption properties due to the organic fibers, which have excellent ductility.

[0019] The resin contained in the fiber-reinforced composite material constituting the honeycomb member of the present invention may be either a thermoplastic resin or a thermosetting resin, but from the viewpoint of excellent shock absorption properties, a thermoplastic resin is preferred. Examples of thermoplastic resins include polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyolefins such as polyethylene, polypropylene, polybutylene, and modified polypropylene, polyamides such as polyoxymethylene, polyamide 6, and polyamide 66, polycarbonate, polymethyl methacrylate, polyvinyl chloride, polyarylene sulfide such as polyphenylene sulfide, polyphenylene ether, modified polyphenylene ether, polyimide, polyamide-imide, polyetherimide, polysulfone, modified polysulfone, polyethersulfone, polyketone, polyetherketone, polyetheretherketone, polyetherketoneketone, polyarylene ether ketone, polyarylate, polyethernitrile, and phenoxy resins. Furthermore, these thermoplastic resins may also be copolymers, modified resins, and / or blends of two or more types of resins.

[0020] Examples of thermosetting resins include unsaturated polyester resins, vinyl ester resins, epoxy resins, phenolic resins, urea resins, melamine resins, thermosetting polyimide resins, BT resins, cyanate ester resins, bismaleimide resins, benzoxazine resins, or copolymers, modified versions thereof, and / or blends of two or more resins.

[0021] Furthermore, from the viewpoint of satisfying flame retardancy requirements for the honeycomb material, the LOI (Limited Oxygen Index) value is preferably 26% or higher, and more preferably 30% or higher. The LOI value can be measured, for example, according to JIS K7201-2 (2007). Examples of resins with an LOI value of 26% or higher include polyarylene sulfide resin, polyetherimide resin, polyethersulfone resin, polyarylene etherketone resin, polyimide resin, and phenolic resin. This range of LOI values ​​may also be achieved by adding a flame retardant to the resin.

[0022] Among these, from the viewpoint of satisfying the heat resistance required for aerospace applications, it is more preferable that the thermoplastic resin be at least one selected from the group consisting of polyarylene sulfide, polyetherimide, polyethersulfone, polysulfone, and polyarylene etherketone, and the thermosetting resin be at least one selected from the group consisting of epoxy resin, phenolic resin, benzoxazine resin, BT resin, cyanate ester resin, bismaleimide resin, and polyimide resin.

[0023] Furthermore, the resin contained in the fiber-reinforced composite material constituting the honeycomb member of the present invention may contain other fillers and additives as appropriate, depending on the application, etc., as long as it does not impair the objectives of the present invention.

[0024] The coating state of the resin-coated fiber substrate is sufficient from the viewpoint of shape stability, ease of thickness control, and degree of freedom of the cell wall made of the fiber-reinforced composite material, as long as at least the intersection points of the individual organic and inorganic fibers constituting the fiber-reinforced composite material are covered. In a more desirable embodiment, the surfaces of the organic and inorganic fibers are not exposed by the resin; in other words, the organic and inorganic fibers are coated with a wire-like film by the resin. As a result, the cell wall made of the fiber-reinforced composite material has further shape stability and exhibits sufficient mechanical properties.

[0025] Furthermore, the cell walls made of fiber-reinforced composite material may contain voids. In this case, it is preferable that the resin-coated fibers act as columnar supports, and that the voids are formed as spaces created by overlapping or intersecting these supports. It is even more preferable that this structure is formed by springback, where the fiber substrate, which is impregnated with resin and in a compressed state, returns to its pre-compression state as the compression is released due to the melting or softening of the resin. This structure provides strength and elastic modulus through the reinforcement effect of the fibers, as well as a weight reduction effect due to the porous structure.

[0026] Furthermore, making the fiber-reinforced composite material of the present invention porous is preferable from the viewpoint of achieving both improved buckling resistance by increasing the thickness of the cell walls and weight reduction of the honeycomb members. In addition, when bonding with the skin material, a portion of the adhesive or the resin of the skin material can flow into the voids of the cell members that come into contact with the skin material, thereby further strengthening the adhesive strength between the skin material and the core member.

[0027] Furthermore, the density of the cell wall, expressed as mass Wc per unit volume, is 0.1 g / cm³. 3 More than 0.8g / cm 3 The following is the result: 0.2 g / cm³ 3 More than 0.7g / cm 3 It is more preferable that the following is the case: 0.3 g / cm³ 3 More than 0.7g / cm 3 The following is even more preferable. By setting the range in this way, it becomes possible to fully satisfy the weight reduction effect. The density of the cell walls will be described in detail in the examples.

[0028] The cell shape of the honeycomb member of the present invention (the cross-sectional shape perpendicular to the axial direction of the columnar cell) is not particularly limited to polygons such as triangles, squares, and hexagons, or to circles and ellipses, but a regular hexagon, i.e., a honeycomb structure, is desirable from the viewpoint of impact resistance. From the viewpoint of the impact absorption characteristics of the honeycomb member, the length of one side of the regular hexagon is preferably 1.5 mm to 15 mm, and more preferably 3 mm to 10 mm.

[0029] As the cell wall of the present invention, a sheet substrate can be made by impregnating a fibrous substrate with resin, and this sheet can be used as the base material for a honeycomb member. From the viewpoint of ease of manufacture, a method of manufacturing the sheet substrate is preferable in which a resin heated to a temperature above the melting or softening temperature is applied to the fibrous substrate and pressure is applied to impregnate the fibrous substrate. The heating temperature at this time becomes the resin impregnation temperature. Suitable equipment for realizing such a method includes compression molding machines and double belt presses. In addition to heating, another example is a method in which the apparent viscosity is reduced by diluting the resin component with a solvent in which it is soluble, then the resin is absorbed into the fibrous substrate, and then only the solvent is removed by volatilization or evaporation.

[0030] The honeycomb member of the present invention can be manufactured using a sheet substrate, which is made by impregnating a resin with a fibrous substrate composed of organic and inorganic fibers, as the base material, by known stretching methods or corrugating methods.

[0031] As a method for manufacturing a fibrous substrate composed of organic and inorganic fibers, for example, there is a method in which the fibers are dispersed in strands and / or nearly single fibers beforehand. Examples of fiber dispersion methods include dry processes such as the airlaid method, which disperses the fibers into a sheet using an airflow, and the carding method, which shapes the fibers by mechanically combing them and forming them into a sheet, as well as wet processes such as the radlite method, which stirs the fibers in water to form paper. In particular, it is desirable to manufacture the fibrous substrate by a wet method, as the proportion of fibers in the fibrous substrate can be easily adjusted by adjusting the concentration of the input fibers, the flow rate of the dispersion liquid, and the speed of the mesh conveyor. The fibrous substrate may consist of individual fibers, or the fibers may be mixed with a matrix resin component in powder or fiber form, or the fibers may be sealed with a resin component.

[0032] In this embodiment, the fibrous base material is preferably a nonwoven fabric composed of discontinuous organic and inorganic fibers, and it is more preferable that the fibers are dispersed in a single-fiber shape, in order to increase the number of contact points by the fibers, improve the homogeneity of the cell walls, and effectively exhibit shock absorption properties.

[0033] The average pore diameter of the porous structure of the cell wall, as measured by the mercury intrusion method, is preferably between 10 μm and 80 μm. This range allows for both the development of mechanical properties through the formation of a dense porous structure and lightweight properties. The mercury intrusion method is a method of measuring pore diameter using a mercury intrusion porosimeter. Mercury is injected into the sample under high pressure, and the pore diameter can be determined from the applied pressure and the amount of mercury injected. The average pore diameter can be calculated using the following formula (1). (Average pore diameter) = 4 × (Pore volume) / (Specific surface area) ... Equation (1).

[0034] <Skin-Core Structure> The honeycomb member of the present invention is not particularly limited, but is typically used as a skin-core structure in which a skin material is bonded to at least one, preferably both, end faces (core opening faces) where columnar cells open. The placement of the skin material is preferable because it allows the load to be received by the surface of the structure when an external force is applied from the skin material side. Furthermore, in a canapé structure in which the skin material is placed on only one side, when an external force is applied to the honeycomb member side, it is preferable because the core can be compressed and receive the load while following the shape of the object, for example, the lunar surface. Hereinafter, in this specification, a structure in which a skin material is bonded to both sides of a honeycomb member, which is a particularly preferred embodiment, will be referred to as a sandwich structure among skin-core structures.

[0035] In Figure 2, the honeycomb member 1 and the skin material 7 are depicted separately to clarify the structure of the skin-core structure 8. The sandwich structure 8 is constructed by bonding the skin material 7 to the open end face of the honeycomb member 1. There are no particular restrictions on the method of bonding the skin material and the honeycomb member, and examples include bonding with adhesive or heat welding. For example, an adhesive sheet and the skin material or a prepreg that is its precursor can be placed on both sides of the core opening surface and bonded to the honeycomb member while heating and curing. Although an adhesive may be used between the honeycomb member 1 and the skin material 7, from the viewpoint of lightweighting the skin-core structure, it is more preferable to directly bond the honeycomb member and the skin material without using an adhesive sheet, and it is preferable to arrange and laminate them so that the skin material is in contact with the core opening surface and bond them by heating and pressing. Furthermore, there are no particular restrictions on the bonding process, and it can be formed by vacuum bag molding, autoclave molding, press molding, etc.

[0036] The average peel torque M (climbing drum peel strength) of the skin material and the honeycomb member measured in accordance with ASTM D1781 (2004) of the structure bonded in this way is preferably 30 N·m / m or more, more preferably 35 N·m / m or more. By having a climbing drum peel strength of 30 N·m / m or more, when an external force is applied, the skin material and the core material are less likely to peel off, and it can be received over the entire surface of the skin material. Therefore, it is suitable as a skin-core structure that can effectively exhibit impact characteristics.

[0037] In a preferred embodiment, the skin material is a fiber-reinforced composite material containing a reinforcing fiber base material selected from at least one of unidirectional continuous fibers, fiber fabrics, and non-woven fabrics and a resin. In that case, the fiber-reinforced composite material serving as the skin material is preferably formed from a prepreg in which a resin is impregnated into a reinforcing fiber base material using the fiber as the reinforcing fiber. Among them, a fiber fabric can be preferably used. The fiber fabric is not particularly limited, but fabrics such as plain weave, twill weave, interlaced weave, and crepe weave are preferred. In particular, the plain weave structure is suitable in terms of being easy to manufacture a thin molded body.

[0038] Also, the areal density of the fibers of the aforementioned prepreg is preferably 150 to 550 g / m 2 This makes it possible to obtain a skin material having excellent mechanical strength. By setting it within such a range, the mechanical strength as the skin material becomes sufficient, and when an external force is applied, the load can be effectively transmitted to the honeycomb member, and the formability during molding and the light weight of the skin-core structure are not impaired, which is preferable. The areal density of the fibers is more preferably 170 to 500 g / m 2 Furthermore, the mass fraction of the fibers in the prepreg is preferably 40% by mass or more and less than 85% by mass. By setting it within such a range, the generation of voids in the skin material is suppressed, and the rigidity of the skin material becomes sufficient, which is preferable.

[0039] The fibers used in the skin material of the present invention can be selected from the same range as the fibers described above. Among these, inorganic fibers are preferred from the viewpoint of mechanical properties, and carbon fibers, which have good specific strength and specific modulus and make a significant contribution to weight reduction, are suitable for the present invention.

[0040] The resin included in the skin material may be either a thermoplastic resin or a thermosetting resin, and can be selected from the same range as the resins mentioned above. [Examples]

[0041] The materials used in the examples and comparative examples are as follows: [Carbon Fiber 1] A continuous carbon fiber with a total of 12,000 strands was obtained by spinning, calcining, and surface oxidation treatment from a copolymer mainly composed of polyacrylonitrile. The properties of this continuous carbon fiber were as follows. Single fiber diameter: 7 μm Specific gravity: 1.8 Tensile strength: 4600 MPa Tensile modulus: 220 GPa [PET fiber 1] Polyester fiber (Toray Industries, Inc. "Tetron" (registered trademark) 1700T-288F-702C, melting point 260℃, fiber diameter 23μm, density 1.38g / cm³) 3 A tensile strength of 14% was used for the fracture. [PET fiber 2] Polyester fiber (Toray Industries, Inc. "Tetron" (registered trademark), melting point 260℃, fiber diameter 7μm, density 1.38g / cm³) 3 A tensile strength of 46% was used. [LCP ​​fiber] Liquid crystal polyester fiber (Toray Industries, Inc. "Siberas" (registered trademark) 1700T-288F, melting point 330℃, fiber diameter 23μm, density 1.39g / cm³) 3 A tensile strength of 2.8% was used. [Aramid fiber] Para-aramid fiber (Toray Industries, Inc.'s "Kevlar" (registered trademark), fiber diameter 12 μm, density 1.44 g / cm³) 3A tensile strength of 3.6% was used.

[0042] [PP resin] This material consists of 80% by mass of unmodified polypropylene resin (Prime PolyPro® J105G, manufactured by Prime Polymer Co., Ltd.) and 20% by mass of acid-modified polypropylene resin (Admer® QB510, manufactured by Mitsui Chemicals, Inc.), with a basis weight of 80 g / m². 2 Resin film 1, basis weight 100g / m² 2 A resin film 2 was fabricated. [PPS resin] Made of polyphenylene sulfide resin (Toray Industries, Inc.'s "Torelina" (registered trademark) M2888), with a basis weight of 100 g / m². 2 A resin film 3 was fabricated. [PEI resin] Made of polyetherimide resin (SABIC's "ULTEM" (registered trademark) 1000), with a basis weight of 100 g / m². 2 A resin film 4 was fabricated.

[0043] [Mat 1] Chopped PET fiber 1 was cut to 13 mm as an organic fiber, and chopped carbon fiber 1 was cut to 6 mm as an inorganic fiber, to obtain chopped PET fiber and chopped carbon fiber. A dispersion with a concentration of 0.1% by mass was prepared consisting of water and a surfactant (Nacalai Tex Co., Ltd., polyoxyethylene lauryl ether (trade name)). Using this dispersion, chopped PET fiber, and chopped carbon fiber, a wet papermaking apparatus was used to adjust the fiber concentration in the dispersion to 0.05% by mass. The resulting fibrous substrate was dried in a drying oven at 200°C for 10 minutes, with the organic and inorganic fibers in the proportions shown in Table 1, resulting in a basis weight of 60 g / m². 2 I obtained mat 1. [Mat 2] The method is the same as for mat 1, except that PET fiber 2 was used as the organic fiber, with a basis weight of 60g / m². 2 I got Matt 2. [Mat 3] Except for using LCP fibers as the organic fiber in the proportions shown in Table 1, the method was the same as for Mat 1, resulting in a basis weight of 55 g / m². 2 I got Matt 3. [Mat 4] Aside from using aramid fiber as the organic fiber, the process was the same as for Mat 3, resulting in a basis weight of 55g / m². 2 I got a mat 4. [Mat 5] The only difference is that it uses only carbon fiber 1 and no organic fibers, and is produced in the same way as mat 1, with a basis weight of 100g / m². 2 I got a Matt 5. [Mat 6] Except for the basis weight and proportions shown in Table 1, the same method as for Mat 1 was used, resulting in a basis weight of 55g / m². 2 I obtained a mat 6.

[0044] [Sheet base material 1] A laminate was prepared by arranging a mat 1 as the fiber base material and a resin film 1 made of PP resin as the resin film in the order of [resin film / fiber base material / resin film]. Then, a sheet base material 1 was obtained by going through the following steps (I) to (IV). The properties of the sheet base material 1 are shown in Table 1. (I) The laminate was placed in a press molding die cavity preheated to 160°C, the die was closed, and it was held for 120 seconds. (II) Next, a pressure of 5 MPa was applied to raise the temperature to 200°C and it was held there for 10 minutes. (III) The cavity temperature was cooled to 50°C while maintaining the pressure. (IV) The mold was opened and the sheet substrate was removed. [Sheet base material 2] Sheet substrate 2 was obtained in the same manner as sheet substrate 1, except that mat 2 was used as the fiber substrate. The properties of sheet substrate 2 are shown in Table 1. [Sheet base material 3] Mat 3 was used as the fiber base material, and resin film 3 made of PPS resin was used as the resin film. Next, sheet base material 3 was obtained in the same manner as sheet base material 1, except that the preheating temperature in step (I) was 200°C and the impregnation temperature in step (II) was 280°C. The characteristics of sheet base material 3 are shown in Table 1. [Sheet base material 4] Mat 4 was used as the fiber base material, and resin film 4 made of PEI resin was used as the resin film. Next, sheet base material 4 was obtained in the same manner as sheet base material 1, except that the preheating temperature in step (I) was 250°C and the impregnation temperature in step (II) was 350°C. The characteristics of sheet base material 4 are shown in Table 1. [Sheet base material 5] Sheet substrate 5 was obtained in the same manner as sheet substrate 1, except that mat 5 was used as the fiber substrate and resin film 2 made of PP resin was used as the resin film. The characteristics of sheet substrate 5 are shown in Table 1. [Sheet base material 6] Sheet substrate 6 was obtained in the same manner as sheet substrate 3, except that mat 6 was used as the fiber substrate. The properties of sheet substrate 6 are shown in Table 1.

[0045] Example 1 A honeycomb core 1 was fabricated using the corrugation method with sheet substrate 1 as the base material. First, the base material was bent into a corrugated sheet using a mold with a surface temperature of 200°C, so that the distance between opposing adhesive parts in the columnar cells (cell size) was 9.5 mm. By adjusting the clearance between the upper and lower molds, multiple corrugated sheets with a cell wall thickness of 125 μm were obtained. The honeycomb core 1 was fabricated by laminating the sheets in a block-like manner, with adhesive interposed between each trough and apex, at positions offset by half a wave pitch, and then bonding them by heating and pressurizing. The characteristics of the honeycomb core 1 are shown in Table 1.

[0046] Example 2 A honeycomb core 2 was fabricated in the same manner as in Example 1, except that a sheet substrate 2 was used as the base material. The properties of the honeycomb core 2 are shown in Table 1.

[0047] Example 3 Honeycomb core 3 was fabricated in the same manner as honeycomb core 1, except that sheet substrate 3 was used as the base material, the mold surface temperature was set to 280°C, and the clearance between the upper and lower molds was changed to adjust the cell wall thickness to 108 μm. The characteristics of honeycomb core 3 are shown in Table 1.

[0048] Example 4 Honeycomb core 4 was fabricated in the same manner as honeycomb core 1, except that sheet substrate 4 was used as the base material, the mold surface temperature was set to 350°C, and the clearance between the upper and lower molds was changed to adjust the cell wall thickness to 111 μm. The characteristics of honeycomb core 4 are shown in Table 1.

[0049] Example 5 Honeycomb core 5 was fabricated in the same manner as honeycomb core 4, except that the clearance between the upper and lower molds was changed and the cell wall thickness was adjusted to 333 μm. The characteristics of honeycomb core 5 are shown in Table 1.

[0050] Comparative Example 1 A honeycomb core 6 was fabricated in the same manner as in Example 1, except that a sheet substrate 5 was used as the base material and the clearance between the upper and lower molds was changed to adjust the cell wall thickness to 144 μm. The characteristics of the honeycomb core 6 are shown in Table 1.

[0051] Comparative Example 2 A honeycomb core 7 was fabricated in the same manner as in Example 3, except that a sheet substrate 6 was used as the base material. The properties of the honeycomb core 7 are shown in Table 1.

[0052] [Prepreg 1 used for skin material] Epoxy resin (Huntsman Advanced Materials Co., Ltd. "Araldite®" MY721: 40 parts by mass, Japan Epoxy Resin Co., Ltd. "Epicote®" 828: 35 parts by mass, "Epicote®" 1001: 25 parts by mass, "Epicote®" 154: 25 parts by mass) with polyethersulfone (Sumitomo Chemical Co., Ltd. "Sumika Excel®" PES After uniformly dissolving polyethersulfone by heating and kneading 5 parts by mass of 5003P in a kneader, polyamide particles (Toray Industries, Inc.'s "Amiran®" SP-500: 13 parts by mass) and a curing agent (Seika Co., Ltd.'s "Seika Cure®" S: 36 parts by mass) were kneaded in a kneader to prepare an uncured epoxy resin composition, from which an epoxy resin film was prepared using a knife coater. Next, the resin composition was impregnated onto both sides of a carbon fiber fabric using a heat roll while heating and pressing, to produce prepreg 1 with a fiber volume content of 60%. The carbon fiber fabric used was a plain weave fabric CF6273H (fiber weight 193 g / m²) made of Toray Industries, Inc.'s carbon fiber "Torayca®" T700G-12K (12,000 fibers, tensile strength 4.9 GPa, tensile modulus 240 GPa, tensile elongation 2.1%). 2 ) was used. The evaluation methods for structure, physical properties, etc., in each example and comparative example are as follows.

[0053] [Evaluation of cell wall density ρm] The density ρm of the cell wall is determined by preparing a sample in which only the cell wall is cut out from the honeycomb material, and measuring the sample mass [g] and the volume [cm³] obtained from the outer circumference of the sample. 3 This value is obtained by dividing by [ ], and is the arithmetic mean of the values ​​measured in five randomly selected samples. To exclude the effect of adhesive between cell walls, a section with a single cell wall was cut out and used as the sample.

[0054] [Method for creating a sandwich structure] A sandwich structure (hereinafter referred to as the "honeycomb sandwich structure") was fabricated by joining a skin material to a honeycomb core according to the following procedures (1) and (2). (1) Layering of samples Prepreg 1 was laminated in two layers at (±45°) / (0° / 90°) and a CFRP plate was fabricated by autoclave molding at 180°C for 2 hours. The obtained CFRP plate was cut to the size of the honeycomb core, and a honeycomb sandwich structure was fabricated by laminating in the order of [CFRP plate / adhesive film / honeycomb core / adhesive film / CFRP plate] and autoclave molding at 120°C for 2 hours.

[0055] [Evaluation of compressive strength and crush strength] Samples were cut from the skin-core structure described above, and tested in accordance with ASTM C365 to measure compressive strength (tested using Stabilized Compression). Compression tests were performed up to a point where the strain exceeded 50%, and the peak stress value was calculated as the compressive strength σco, while the average compressive stress value in the strain range of 10% to 50% was calculated as the crush strength σcr. [Examples 1-5, Comparative Examples 1-2] Based on the material composition of the honeycomb core and skin material and the method for fabricating the sandwich structure described in Table 1, sandwich structures for Examples 1-5 and Comparative Examples 1-2 were fabricated. Samples were cut from the obtained sandwich structures and evaluated as described above. The characteristics of each are shown in Table 1.

[0056] A comparison of Examples 1 and 2 with Comparative Example 1 shows that the honeycomb member of the present invention exhibits superior crush strength and lightweight properties, which are indicators of impact absorption characteristics, by mixing organic fibers with the fibrous base material. Furthermore, Examples 3 and 4 show that the impact absorption characteristics and lightweight properties remain excellent even when the type of organic fiber or resin is changed. Upon examining the sandwich structures after these compression tests, it was observed that the organic fibers were pulled out from the fracture surface, indicating an improvement in impact absorption characteristics due to the organic fibers. In Example 5, fracture in a form where the cell walls folded was also observed, indicating an improvement in impact absorption characteristics due to the effect of creating a porous structure cell wall containing voids. In Comparative Example 2, the organic fibers melted at the molding temperature of the sheet substrate 6 and did not exist in fibrous form, resulting in inferior impact absorption characteristics compared to Example 3.

[0057] [Table 1] [Industrial applicability]

[0058] The honeycomb member and skin-core structure of the present invention can be placed on the surface of a target member and suitably applied as an impact absorbing member. Because it exhibits high impact absorption characteristics, it can be suitably applied as a barrier member installed in the escape zone of vehicles such as automobiles and trains, from the viewpoint of protecting the automobile, train, and the people riding in it. Furthermore, because it is also lightweight, when used in flying objects such as rockets, artificial satellites, UAMs (Urban air mobility), drones, and helicopters, as well as vehicles such as automobiles and trains, it suppresses the increase in weight of the flying object and the vehicle itself, making it possible to reduce the energy generated during a collision, thus making it suitably applicable. Among these, it can be suitably applied to the lower fuselage structure of a flying object, the landing gear of a flying object, battery protection members, containers for dropped materials, emergency stop devices of vehicles, leading edge members of wings, and cushioning materials for monocoque structures. [Explanation of Symbols]

[0059] 1: Honeycomb material 2: Organic fibers 3: Inorganic fibers 4: Resin 5: Cell wall 6:Void 7: Skin material (prepreg) 8: Skin-Core Structure

Claims

1. A honeycomb member having a structure consisting of an aggregate of hollow columnar cells partitioned by cell walls, wherein the cell walls are made of a fiber base material consisting of organic fibers and inorganic fibers, and a fiber-reinforced composite material containing resin, and the fiber diameter of the organic fibers is 5 to 25 μm.

2. The honeycomb member according to claim 1, wherein the organic fiber and the resin satisfy any of the following (A) to (D). (A) The melting point of the organic fiber is higher than the melting point of the resin. (B) The resin has no melting point, and the melting point of the organic fiber is higher than the glass transition temperature of the resin + 100°C. (C) The organic fiber has no melting point, and the glass transition temperature of the organic fiber + 50°C is higher than the melting point of the resin. (D) Neither the organic fiber nor the resin has a melting point, and the glass transition temperature of the organic fiber is higher than the glass transition temperature of the resin.

3. The honeycomb member according to claim 1, wherein the fiber length of the organic fiber is 3 to 15 mm and the fiber length of the inorganic fiber is 2 to 15 mm.

4. The honeycomb member according to any one of claims 1 to 3, wherein the volume content of the organic fibers is 20 to 40 volume%, and the volume content of the inorganic fibers is 60 to 80 volume%.

5. The basis weight of the aforementioned fiber base material is 5 to 80 g / m². ２ The honeycomb member according to claims 1 to 3.

6. The honeycomb member according to any one of claims 1 to 3, wherein the average pore diameter of the cell wall, as measured using the mercury intrusion method of JIS R1655 (2003), is 10 to 80 μm.

7. The honeycomb member according to any one of claims 1 to 3, wherein the organic fiber is a fiber made of a resin selected from polyolefin resin, polyester resin, polyaryletherketone resin, aromatic polyamide resin, all aromatic polyester resin, polyetherimide resin, polycarbonate resin, cellulose fiber, and polyarylene sulfide resin.

8. A skin-core structure comprising a honeycomb member according to any one of claims 1 to 3, wherein a skin material is bonded to the surface of the honeycomb member.

9. The skin-core structure according to claim 8, wherein the skin material comprises a fiber-reinforced resin composite material comprising a reinforcing fiber base material selected from at least one of unidirectional continuous fibers, woven textiles, and nonwoven fabrics, and a resin.

10. An impact absorbing member using the honeycomb member described in any one of claims 1 to 3 and / or the skin-core structure described in claim 8.

11. A structure for the lower fuselage of a flying vehicle, landing gear for a flying vehicle, battery protection member, container for dropped materials, emergency stop device for a vehicle, leading edge member for a wing, or cushioning material for a monocoque structure, using the honeycomb member according to any one of claims 1 to 3 and / or the skin-core structure according to claim 8.

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