JP2023066506A - Fiber-reinforced member - Google Patents

Abstract

To provide a fiber-reinforced member which has a long fatigue life, excels in strength, is flat in cross-sectional shape and has an internal space.SOLUTION: A fiber-reinforced member has a film disposed on the inner surface side of a substrate comprising a fiber-reinforced composite material which is flat in cross-sectional shape and has an internal space, the film having a thickness of 10 μm or more and 200 μm or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a fiber reinforced member suitable for use in propeller blades.

Fiber-reinforced composite materials are used in a wide range of industrial fields due to their light weight, high strength, and high rigidity. In particular, molded articles using prepreg, which is an intermediate material in which reinforcing fibers are impregnated with resin, and molded articles in which reinforcing fibers are impregnated with resin at the time of molding are preferably used. In recent years, blade-shaped fiber-reinforced composite materials have been widely used in the fields of wind turbines and aircraft. Blade-shaped fiber-reinforced composite materials sometimes have a hollow structure to reduce weight. , ships and other means of transportation, and in the field of wind power generation.

As a fiber-reinforced composite material having such a hollow structure, there is a spar with a hollow structure molded using a bladder (for example, Patent Document 1) and a hollow blade composed of a core with a grid structure and a skin layer containing a fiber-reinforced resin. It has been proposed (for example, Patent Document 2). Further, the hollow blade includes a hollow blade main body having a cylindrical blade root portion and extending along the blade length direction from the blade root portion, and a reinforcing plate provided so as to be in contact with the inner surface of the blade root portion. has been proposed (for example, Patent Document 3).

European Registered Patent No. 3556544 U.S. Patent Application Publication No. 2019/0195073 JP 2018-127963 A

As a method for producing a blade-like fiber-reinforced composite material having a hollow structure, two sheet-like members having curved surfaces are bonded together to form a blade-like shape, or tubular members are connected in the longitudinal direction. It is convenient to join cap members on both ends to form a blade-like shape. In some cases, moisture and undesired substances can enter the interior space leading to degradation of the fiber reinforced composite. Such moisture and substances may shorten the life of the product or impair its mechanical properties.

Therefore, the present invention provides a fiber-reinforced member having a flat cross-sectional shape and internal space, which has a long fatigue life and excellent strength by reducing the influence of such substances that are undesirable on the product life and the like. The challenge is to

The present invention employs one of the following means in order to solve this problem. i.e.
[1] A fiber-reinforced member in which a film is disposed on the inner surface side of a substrate made of a fiber-reinforced composite material having a flat cross-sectional shape and an internal space, wherein the film has a thickness of 10 μm or more and 200 μm or less. A fiber reinforced member.
[2] When the melting point of the resin constituting the film is Tm1 and the glass transition temperature of the resin constituting the fiber-reinforced composite material is Tg, the relationship therebetween is Tm1>Tg. ] The fiber reinforced member as described in .
[3] When the melting point of the resin that constitutes the film is Tm1 and the melting point of the resin that constitutes the fiber-reinforced composite material is Tm2, the relationship therebetween is Tm1>Tm2; A fiber reinforced member as described.
[4] The fiber-reinforced member according to any one of [1] to [3], wherein Tm1 is 150° C. or higher, where Tm1 is the melting point of the resin constituting the film.
[5] The film according to any one of [1] to [4], wherein the water vapor transmission rate of the film is 100 g/(m ² ·24 hr) or less under conditions of 40°C and 90% RH. fiber reinforced member.
[6] The fiber-reinforced member according to any one of [1] to [5], wherein the ratio of the film covering the inner surface of the base material is 90% or more of the area of the inner surface.
[7] The fiber-reinforced member according to any one of [1] to [6], wherein the resin constituting the film is any one of polypropylene resin, polyamide resin, and fluororesin.
[8] The fiber-reinforced member according to any one of [1] to [7], wherein the substrate has two or more spaces having a volume of 10 cm ³ or more.
[9] The fiber-reinforced member according to any one of [1] to [8], which has a length of less than 150 cm.
[10] The fiber-reinforced member according to any one of [1] to [9], wherein the fibers used in the fiber-reinforced composite material are either or both carbon fibers and glass fibers.
[11] Resins used in the fiber-reinforced composite material include unsaturated polyester resins, vinyl ester resins, epoxy resins, phenolic resins (resol type), urea-melamine resins, polyimide resins, copolymers thereof, and The fiber-reinforced member according to any one of [1] to [10], which is at least one resin selected from the group consisting of modified substances.

According to the present invention, it is possible to provide a fiber-reinforced member having a long fatigue life, excellent strength, a flat cross-sectional shape, and an internal space.

1 is a cross-sectional view of an example of a fiber-reinforced member of the present invention; FIG. FIG. 4 is a cross-sectional view of another example of the fiber-reinforced member of the present invention; 1 is a top view of an example of a fiber-reinforced member of the present invention; FIG. It is an example of an end reinforcing layer that can be used in the present invention, (a) shows an example of an end reinforcing layer of a roll structure, and (b) shows an example of an end reinforcing layer of a folded structure.

The present invention is a fiber-reinforced member in which a film is arranged on the inner surface side of a substrate made of a fiber-reinforced composite material having a flat cross-sectional shape and an internal space. A film is placed on the side of the inner surface as illustrated in FIG. By placing the film on the side of the inner surface in this way, it acts as a protective layer, preventing moisture such as rain, fog, dew, and sea salt water from penetrating into the fiber-reinforced composite material, thereby improving fatigue life and strength. can suppress the decrease in

The substrate made of the fiber-reinforced composite material of the present invention has a flat cross-sectional shape. Here, the cross-sectional shape is flat, assuming a solid with uniform density formed on the outer surface of the base material, and among the cross sections passing through the center of gravity, the cross section with the smallest area (the cross section is In the cross section L for convenience), the length (l1) of the line segment passing through the center of gravity of the figure formed by the outer edge of the cross section L and connecting the farthest two points on the outer edge (l1) and the center of gravity of the figure The ratio (l1/l2) to the length (l2) of the line segment that passes through and connects the two closest points on the outer edge is 1.5 or more, preferably perpendicular to the cross section L It is desirable that 50% or more of a line segment that is straight and within the solid body satisfies the relationship of the ratio (l2/l1) in a cross section orthogonal to the line segment.

The fiber-reinforced member of the present invention preferably has a length of less than 150 cm, and preferably has two or more spaces with a volume of 10 cm ³ or more inside the substrate made of the fiber-reinforced composite material. As a structure for providing a plurality of spaces inside the base material, a structure partitioned by shear webs that play a role of reinforcing rigidity, as illustrated in FIG. 2, can be cited. Here, the length of the fiber-reinforced member refers to the length of the longest side of the rectangular parallelepiped with the smallest volume that circumscribes the fiber-reinforced member. For example, the fiber-reinforced member has a wing shape as shown in FIG. If so, it means the length from the wing root to the wing tip.

Materials constituting the fiber-reinforced member of the present invention and a method for producing the fiber-reinforced member will be described below with reference to examples.

<Fiber used for fiber-reinforced composite material (reinforced fiber)>
A base material made of a fiber-reinforced composite material is used for the fiber-reinforced member of the present invention. The fibers used to reinforce the composite material are not limited as long as they have a reinforcing effect, but carbon fibers, glass fibers, aramid fibers, and metal fibers are preferably used. Among them, it is preferable to use carbon fiber. Although the carbon fiber is not particularly limited, for example, polyacrylonitrile (PAN)-based, pitch-based, and rayon-based carbon fibers can be preferably used from the viewpoint of improving mechanical properties and reducing the weight of fiber-reinforced resin molded products. may be used alone or in combination of two or more. Among them, PAN-based carbon fiber is more preferable from the viewpoint of the balance between the strength and the elastic modulus of the resulting fiber-reinforced resin molded product.

The single fiber diameter of the reinforcing fibers is preferably 0.5 μm or more, more preferably 2 μm or more, and even more preferably 4 μm or more. Further, the single fiber diameter of the reinforcing fibers is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. The strand strength of the reinforcing fibers is preferably 3.0 GPa or higher, more preferably 4.0 GPa or higher, and even more preferably 4.5 GPa or higher. The strand elastic modulus of the reinforcing fiber is preferably 200 GPa or higher, more preferably 220 GPa or higher, even more preferably 240 GPa or higher. If the strand strength or elastic modulus of the reinforcing fiber is within this range, the mechanical properties of the fiber-reinforced resin molded product can be enhanced.

The reinforcing fibers may be continuous fibers (long fibers) or discontinuous fibers (short fibers).

<Resin (matrix resin) used for fiber-reinforced composite material>
In the base material made of the fiber-reinforced composite material used for the fiber-reinforced member of the present invention, the resin is used as a matrix material that encloses the reinforcing fibers. The matrix resin is not particularly limited, and thermoplastic resins or thermosetting resins can be used. Examples include epoxy resins, unsaturated polyester resins, vinyl ester resins, phenol resins, epoxy acrylate resins, urethane acrylate resins, Thermosetting resins such as phenoxy resin, alkyd resin, urethane resin, maleimide resin, cyanate resin, polyamide, polyacetal, polyacrylate, polysulfone, ABS, polyester, acrylic, polybutylene terephthalate (PBT), polyethylene terephthalate (PET) ), polyethylene, polypropylene, polyphenylene sulfide (PPS), polyetheretherketone (PEEK), liquid crystal polymer, vinyl chloride, fluororesins such as polytetrafluoroethylene, and thermoplastic resins such as silicone. Further, copolymers and modified products of polymers forming these resins can also be used. Moreover, it does not prevent using multiple types of resins.

<Film placed on the inner surface side of the substrate made of fiber-reinforced composite material>
In the fiber-reinforced member of the present invention, a film is arranged on the inner surface side of a substrate made of a fiber-reinforced composite material having an internal space. The lower limit of the thickness of the film used here is 10 µm or more, preferably 20 µm or more, and more preferably 30 µm or more. If the thickness of the film is less than 10 μm, the film may be torn during production or use of the fiber-reinforced member. The upper limit of the thickness of the film is 200 µm or less, preferably 150 µm or less, and more preferably 100 µm or less. If the thickness exceeds 200 μm, the film may not follow the shape of the molded article during production of the fiber-reinforced member, resulting in poor molding.

When the melting point of the resin constituting the film used in the present invention is Tm1 and the glass transition temperature of the resin used in the fiber-reinforced composite material is Tg, the relationship between them is preferably Tm1>Tg. If Tm1 is less than Tg, the film may tear during production of the fiber-reinforced member and may not function as a protective layer. Also, Tm1 is preferably 150° C. or higher, more preferably 180° C. or higher, and even more preferably 210° C. or higher. If Tm1 is less than 150°C, the film may melt during the production of the fiber-reinforced member and lose its function as a protective layer.

Further, when the melting point of the resin used in the fiber-reinforced composite material is Tm2, the relationship with Tm1 is preferably Tm1>Tm2. If Tm1 is less than Tm2, the film may tear during production of the fiber-reinforced member and may not function as a protective layer. Here, the melting points Tm1 and Tm2 and the glass transition temperature Tg are measured according to JIS 7121:2012.

The film used in the present invention preferably has a water vapor transmission rate of 100 g/(m ² ·24 hr) or less, more preferably 10 g/(m ² ·24 hr) or less under conditions of 40°C and 90% RH. , 1 g/(m ² ·24 hr) or less is more preferable. Here, water vapor permeability is measured according to JIS 7129-1:2019.

The type of resin constituting the film used in the present invention is not particularly limited as long as it can be molded as a film, and is polyamide, polyacetal, polyacrylate, polysulfone, ABS, polyester, acrylic, and polybutylene terephthalate. (PBT), polyethylene terephthalate (PET), polyethylene, polypropylene, polyphenylene sulfide (PPS), polyether ether ketone (PEEK), liquid crystal polymer, polyvinyl chloride, fluorine-based resins such as polytetrafluoroethylene, and thermoplastic resins such as silicone. mentioned. Among them, it is preferable to use a polypropylene resin, a polyamide resin, or a fluororesin because they are advantageous in terms of weather resistance and chemical resistance.

The shape of the film constituting the fiber-reinforced member of the present invention is preferably a bag-like film. The bag-like shape can reduce the area where humidity such as rain, fog, dew, sea salt water, etc. directly adheres to the fiber reinforced resin. Also, compressed air, particles, etc. can be efficiently introduced during molding.

Moreover, from the viewpoint of protecting the inner surface of the substrate made of the fiber-reinforced composite material, the film preferably covers 90% or more of the area of the inner surface of the substrate made of the fiber-reinforced composite material. The larger the inner surface covering ratio, the more moisture such as rain, fog, dew, and sea salt water can be prevented from penetrating into the fiber-reinforced composite material, and the deterioration of fatigue life and strength can be suppressed. Here, the area covered by the film refers to the area in which the film is in contact with the inner surface of the substrate made of the fiber-reinforced composite material. In addition, in FIGS. 1 and 2, the film is intentionally separated from the substrate made of the fiber-reinforced composite material in order to clearly show the presence of the film.

<End reinforcement layer>
Since the fiber-reinforced member of the present invention uses a base material made of a fiber-reinforced composite material having a flattened cross-sectional shape, particularly preferably a wing-like shape, the end portion thereof breaks when an impact is applied. Possibilities are considered. Therefore, this layer is provided for the purpose of reinforcing the end. FIG. 1 illustrates an embodiment in which edge reinforcement layers are provided, and edge reinforcement layers 3 can be seen at the front and rear edges of the interior space. The edge reinforcing layer is preferably used in the peripheral part, and the peripheral part is the fiber reinforced member when projected from the upper part (the side of the plane with the largest area in the circumscribed rectangular parallelepiped with the smallest volume; the same applies to the bottom) It means the peripheral portion, and means the entire circumference in the case of a fiber reinforced member manufactured using a mold, and both the left and right ends in the case of a long fiber reinforced member manufactured by a continuous molding method.

The end reinforcing layer is desirably made of a fiber-reinforced composite material, more preferably a fiber-reinforced composite material composed of unidirectionally aligned reinforcing fibers and a matrix resin.

In addition, the end reinforcing layer on the leading edge 5 side is preferably a laminate of two or more sheet-like fiber-reinforced composite materials, and preferably a laminate of four or more sheet-like fiber-reinforced composite materials. more preferred.

Moreover, the end reinforcing layer on the trailing edge 6 side is preferably one or more layers of a sheet-like fiber-reinforced composite material or a laminate thereof.

On the other hand, the sheet-like fiber-reinforced composite material used for the end reinforcing layers is also preferably fiber-reinforced foam. Examples of such fiber-reinforced foams include sandwich structures (e.g., WO2014/162873) and nonwoven fabrics in which one surface is impregnated with a thermoplastic resin and reinforcing fibers are exposed from the other surface (e.g., Japanese Unexamined Patent Application Publication No. 2014-172201) can be exemplified.

Although it depends on the dimensions of the fiber-reinforced member of the present invention, the cross-sectional area of the end reinforcing layer is preferably 1 mm ² or more, more preferably 5 mm ² or more in a cross section perpendicular to the contour direction of the peripheral portion. The cross-sectional area of the edge reinforcing layer is preferably 1200 mm ² or less, more preferably 500 mm ² or less. When the thickness is within the above preferable range, it becomes easy to conduct heat uniformly to the inside of the laminate, and as a result, a fiber-reinforced member having an excellent appearance can be obtained.

The edge reinforcing layer preferably has a fiber orientation along the contour of the peripheral edge. For example, by fabricating a longitudinally oriented elongated laminate and then arranging it along the contour of the peripheral edge, the fibers can be oriented in the direction along the contour of the peripheral edge.

The edge reinforcing layer preferably has a roll structure or a folded structure.

FIG. 4(a) shows an example of a roll structure, and FIG. 4(b) shows an example of a folding structure. The end reinforcing layer having a scroll structure can be easily adjusted in thickness and cross-sectional area by adjusting the amount of winding, and is easy to manufacture, so that the ends of the fiber reinforced member are rounded. It is particularly suitable for use when On the other hand, the thickness of the end reinforcing layer having a folded structure can be changed by adjusting the folding width and the number of folding times, and the thickness can be easily adjusted to be thinner than the roll structure, so the ends of the fiber reinforced member are sharp. It can be used particularly preferably when it has a similar shape.

<Method for producing fiber-reinforced member>
The fiber-reinforced member of the present invention can be easily molded using a sheet-like fiber-reinforced composite material and a film. In particular, a sheet-like fiber-reinforced composite material can be obtained by preferably using a prepreg known as an intermediate base material in which reinforcing fibers are previously impregnated with a resin. As a molding method, autoclave molding, filament winding molding, press molding, transfer molding, stamping molding, and injection molding can be applied.

A molding method using prepreg will be described below as an example.

A prepreg is composed of reinforcing fibers and a matrix resin. The lower limit of the volume content of reinforcing fibers contained in the prepreg is preferably 40% or more, more preferably 45% or more, and even more preferably 50% or more. If it is less than 40%, there is a possibility that desired mechanical properties cannot be obtained when molded. Moreover, the upper limit of the volume content is preferably 80% or less, more preferably 75% or less, and even more preferably 70% or less. If it exceeds 80%, voids may be included and the mechanical properties may be impaired.

The basis weight of the reinforcing fibers contained in the prepreg is preferably 50 g/m ² or more and 1000 g/m ² or less. If the basis weight is too small, voids in which reinforcing fibers do not exist may occur in the plane of the prepreg. By setting the weight per unit area to 50 g/m ² or more, it is possible to eliminate voids that serve as starting points for fracture. Also, if the basis weight is 1000 g/m ² or less, heat can be uniformly conducted to the inside during preheating for molding. The basis weight is more preferably 100 g/m 2 or more and 600 g/m ² or less, still more preferably 150 g/m ^{2 or} more and 400 g/m ² or less, in order to achieve both structural uniformity and heat transfer uniformity. is. The basis weight of the reinforcing fiber is measured by cutting out a 10 cm square region from the reinforcing fiber sheet, measuring the mass, and dividing by the area. The measurement is performed 10 times for different parts of the reinforcing fiber sheet, and the average value is taken as the basis weight of the reinforcing fiber.

As the prepreg used in the present invention, a prepreg having cuts on its surface can be preferably used (such a prepreg is referred to as "cut prepreg"). The cut prepreg preferably has cuts that are regularly distributed over the entire surface of the prepreg, and the cuts cut the reinforcing fibers contained in the prepreg at the locations where the cuts exist. Such regularly distributed cuts can be provided by the method described in Japanese Patent No. 5272418, for example.

According to the cut prepreg, openings and deviations are more likely to occur at the locations where the cuts are provided, and the extensibility of the prepreg in the direction of the reinforcing fibers is improved. In addition, the flow at the time of compression molding opens the incision insertion point and separates the fiber bundles of the reinforcing fibers, thereby exhibiting flexibility as a prepreg and increasing fluidity. By making the prepreg flowable or easily deformable in this way, the reinforcing fibers reach the ends, and the area where the resin is excessive is reduced, resulting in a fiber-reinforced member with excellent mechanical properties and appearance. Obtainable. From the viewpoint of fluidity, it is preferable that the cuts be made throughout the thickness direction of the prepreg.

The use of cut prepreg for the end reinforcing layer suppresses tension in the fiber direction when the end reinforcing layer is pressed against the end contour of the fiber reinforced member due to internal pressure and is deformed. The occurrence is suppressed, which is preferable in terms of appearance quality and mechanical properties at the end. The fiber direction of the reinforcing fibers of the end reinforcing layer is preferably along the end contour of the fiber reinforced member.

Next, a specific example of a molding method using prepreg will be described.

As a method for molding the fiber-reinforced member of the present invention, autoclave molding and filament winding molding are performed by preparing a core offset by the thickness of the base material made of the fiber-reinforced composite material and the thickness of the film. A film and a prepreg are wound in this order around the core to form a mold. The molding pressure is preferably 0.3 MPa or more so that the resin is filled between the fibers, and the type of the core is preferably a heat-resistant resin having a melting point higher than the molding temperature. The core can also be split so that it can be removed after molding.

When press molding is adopted, a resin bag is produced and prepared by offsetting the thickness of the base material made of fiber-reinforced composite material, and compressed air or particles are put into the bag so as to apply internal pressure. The molding pressure is preferably 0.3 MPa or more so that the resin fills between the fibers. The type of particles is not particularly limited, and examples thereof include alumina particles, glass balloons, fly ash balloons, perlite and the like. The lower limit of the particle diameter is preferably 10 µm or more, more preferably 20 µm or more, and even more preferably 30 µm or more. If it is below the lower limit, it may be difficult to handle and the cost may be high. The upper limit is preferably 500 µm or less, more preferably 350 µm or less, and even more preferably 200 µm or less. When the upper limit is exceeded, the uneven shape transferred to the fiber-reinforced member becomes large, and the mechanical properties of the fiber-reinforced member may deteriorate.

For filament winding molding and transfer molding, a core is prepared by offsetting the thickness of the base material made of fiber-reinforced composite material and the thickness of the film, and the film and dry fiber are wound around the core in this order to form the core. . It is preferable to use a molding pressure of 0.3 MPa or more so that the resin is filled between the fibers, and a resin having a melting point higher than the molding temperature as the type of the core. The core can also be split so that it can be removed after molding.

The prepreg may be used by winding a core with one sheet-like prepreg, or two or more sheet-like prepregs may be used for molding. In obtaining a base material made of a flat fiber-reinforced composite material, it is convenient to use two sheet-like prepregs corresponding to the upper half surface side and the lower half surface side when viewed from the peripheral edge.

On the other hand, as a method of manufacturing using stamping molding or injection molding, molding is performed by attaching a film to the surface of a thermoplastic resin substrate or the surface of a mold. The molding pressure is preferably 1 Ma or more so that the thermoplastic resin is filled between the fibers. When there are a plurality of parts composed of a substrate made of a fiber-reinforced composite material and a film, they can be joined by welding or adhesion.

INDUSTRIAL APPLICABILITY The present invention can provide a fiber-reinforced member having a long fatigue life, excellent strength, a flat cross-sectional shape, and an internal space.

The fiber reinforced member of the present invention can be suitably used for propellers of UAM (Urban Air Mobility), UAS (Unmanned Aircraft Systems), aircraft, and the like.

1: Base material made of fiber reinforced composite material 2: Film 3: Edge reinforcing layer 4: Shear web 5: Leading edge 6: Trailing edge 7: Wing tip 8: Wing root

Claims (11)

A fiber-reinforced member in which a film is disposed on the inner surface side of a substrate made of a fiber-reinforced composite material having a flat cross-sectional shape and an internal space, wherein the film has a thickness of 10 μm or more and 200 μm or less. reinforcement material. 2. The method according to claim 1, characterized in that, when the melting point of the resin constituting the film is Tm1 and the glass transition temperature of the resin constituting the fiber-reinforced composite material is Tg, the relationship therebetween is Tm1>Tg. fiber reinforced member. 2. The fiber according to claim 1, wherein the relationship between Tm1 and Tm2 is Tm1>Tm2, where Tm1 is the melting point of the resin forming the film and Tm2 is the melting point of the resin forming the fiber-reinforced composite material. reinforcement material. The fiber-reinforced member according to any one of claims 1 to 3, wherein Tm1 is 150°C or higher, where Tm1 is the melting point of the resin constituting the film. The fiber-reinforced member according to any one of claims 1 to 4, wherein the film has a water vapor permeability of 100 g/(m ² ·24 hr) or less at 40°C and 90% RH. The fiber-reinforced member according to any one of claims 1 to 5, wherein the film covers the inner surface of the base material at a rate of 90% or more of the area of the inner surface. The fiber-reinforced member according to any one of claims 1 to 6, wherein the resin constituting the film is any one of polypropylene resin, polyamide resin and fluororesin. The fiber-reinforced member according to any one of claims 1 to 7, characterized in that there are two or more spaces with a volume of 10 cm ³ or more inside the base material. Fiber reinforced member according to any one of claims 1 to 8, characterized in that the length is less than 150 cm. The fiber-reinforced member according to any one of claims 1 to 9, wherein the fiber used in said fiber-reinforced composite material is either or both of carbon fiber and glass fiber. The resin used for the fiber-reinforced composite material consists of unsaturated polyester resin, vinyl ester resin, epoxy resin, phenolic resin (resol type), urea-melamine resin, polyimide resin, copolymers thereof and modified products thereof. The fiber-reinforced member according to any one of claims 1 to 10, characterized in that it is at least one resin selected from the group.

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