JP7779084B2 - Composite materials - Google Patents

Description

The present invention relates to a composite member in which a reinforcing member is joined to a reinforced member via an adhesive layer, and in which part or all of the outermost layer of the reinforcing member or reinforced member involved in the joining is made of unidirectional prepreg.

Components made from prepregs, which are made by impregnating reinforcing fibers with thermosetting resin, are particularly suitable for use in aircraft due to their lightweight and high strength characteristics. When using this type of material to manufacture aircraft fuselage barrels, wings, tails, etc., composite component structures are preferably used, in which reinforcing components such as stringers are joined together with panel-shaped surface components (reinforced components), which have low rigidity against bending loads on their own. By combining components, the desired rigidity can be provided for the airframe structure. In this type of application, how to strengthen the bonds between components and maintain high reliability is a technical field that has received particular attention not only during aircraft operation but also in aircraft design and manufacturing.

Patent Document 1 discloses a composite member in which a stringer-like reinforcing member is fastened to a panel-like member with fasteners for integration. This mechanical fastening method is applicable regardless of the type of material used to construct the members, and also provides highly reliable fastening. During manufacturing, holes are drilled in each of the separate members to be fastened, and the members are positioned relative to each other before fastening the fasteners. This typically involves fastening the members together with multiple fasteners spaced apart, and because the above process is repeated the desired number of times for each fastener, the entire process takes a long time and it is difficult to improve efficiency. Furthermore, the weight of the metal fasteners themselves compromises the lightweight nature of the composite member.

Separately, Patent Document 2 discloses a method in which a panel-shaped component is manufactured from a prepreg of reinforcing fiber and thermosetting resin, and then a stringer, a reinforcing component, is adhesively bonded to the component. The adhesive is a lightweight resin material, and does not increase the weight of the composite component, as occurs with fasteners. Furthermore, the adhesive bonding process does not require drilling holes in the component, which is advantageous in that it is relatively simple compared to fasteners.

Patent Document 3 discloses a configuration for adhesively joining components made of composite materials containing reinforcing fibers, with the aim of increasing the strength of the joint. It states that the strength of the joint is increased by forming an uneven joint surface in the cross section of the joint between the composite components, where the adhesive contacts the areas of each component that come into contact with the adhesive. A similar configuration is also disclosed in Patent Document 4.

: International Publication No. 2010/046684 : International Publication No. 2018/170330 : International Publication No. 2006/089534 : International Publication No. 2004/060658

As described in Patent Documents 2 to 4, these adhesive methods for joining components provide an approach to improving the problems associated with conventional fastener fastening for composite materials containing reinforcing fibers. However, when prepregs containing reinforcing fibers and thermosetting resins are used as reinforcing or reinforced components, the bonding surfaces between components can sometimes peel off under low loads due to the characteristic of this type of material that varies in stiffness and strength depending on the direction of the fibers. This peeling limits the load-bearing capacity of the components, and remains an issue that must be resolved when joining components made of composite materials.

The object of the present invention is to provide a composite member having enhanced load-bearing performance by drastically improving the resistance to peeling at the joint as described above, when a reinforcing member is bonded to a reinforced member via an adhesive layer, and the outermost layer in contact with the adhesive layer of the reinforced member or the reinforcing member is composed of a unidirectional prepreg containing reinforcing fibers and a thermosetting resin.

The present invention provides a composite component in which a reinforcing member having an aspect ratio according to the following formula (1) greater than 1 and less than 1,000,000,000 is joined to a reinforced member via an adhesive layer, wherein the adhesive layer contains reinforcing fibers that constitute at least one or both of the reinforcing member and the reinforced member, and a part or all of the outermost layer of the reinforcing member that contacts the adhesive layer is made of a unidirectional prepreg containing reinforcing fibers and a thermosetting resin, and the angle α between the orientation direction of the reinforcing fibers of the unidirectional prepreg and the longitudinal direction of the projected length of the reinforcing member in a top view is 0°<α<30°.
Aspect ratio = Projected length of reinforcing member (m) / Projected width of reinforcing member (m) (1)

Another aspect of the present invention is a composite material in which a reinforcing member having an aspect ratio according to the following formula (1) greater than 1 and less than 1,000,000,000 is joined to a reinforced member via an adhesive layer, wherein the adhesive layer contains reinforcing fibers that constitute at least one or both of the reinforcing member and the reinforced member, and a part or all of the outermost layer of the reinforced member that contacts the adhesive layer is made of a unidirectional prepreg containing reinforcing fibers and a thermosetting resin, and the angle β between the orientation direction of the reinforcing fibers of the unidirectional prepreg and the longitudinal direction of the projected length of the reinforcing member in a top view is 0°<β<30°.
Aspect ratio = Projected length of reinforcing member (m) / Projected width of reinforcing member (m) (1)

In a preferred embodiment of the composite member of the present invention, in the reinforced member to which the reinforcing member is joined, the angle α satisfies the range 0°<α<30°, and the angle β satisfies the range 0°<β<30°.

In a preferred embodiment of the composite member of the present invention, the adhesive layer is made of a thermosetting resin.

In a preferred embodiment of the composite member of the present invention, the thermosetting resin is at least one selected from epoxy resin, benzoxazine resin, cyanate ester resin, bismaleimide resin, and phenolic resin.

In a preferred embodiment of the composite member of the present invention, the adhesive layer is made of a thermoplastic resin.

In a preferred embodiment of the composite member of the present invention, the thermoplastic resin is at least one selected from polyamide resin, polyphenylene sulfide resin, polyether ketone ketone resin, and polyether ether ketone resin.

In a preferred embodiment of the composite member of the present invention, the adhesive layer contains reinforcing fibers that constitute at least one or both of the reinforcing member and the reinforced member.

In a preferred embodiment of the composite member of the present invention, the thickness of the adhesive layer is 10 μm or more and less than 500 μm.

In composite members in which a reinforcing member is joined to a reinforced member via an adhesive layer, the orientation direction of the reinforcing fibers in the unidirectional prepreg that constitutes the outermost layer of the reinforcing member or reinforced member is within a specific range relative to the direction of the main load that the reinforcing member receives, making it less likely for delamination to occur between the reinforcing member and the reinforced member, resulting in a composite member with improved load-bearing capacity.

Fig. 1(a) is a perspective view showing an example of a composite member of the present invention. Fig. 1(b) is a perspective view showing the outermost layer in contact with the adhesive layer of the reinforcing member and the reinforced member, seen through the reinforcing member of Fig. 1(a). In this example, a unidirectional prepreg is disposed on the outermost surface of the reinforcing member. Fig. 1(c) is a top view of Fig. 1(b). Fig. 2(a) is a perspective view showing an example of a composite member of the present invention. Fig. 2(b) is a perspective view showing the outermost layer in contact with the adhesive layer of the reinforcing member and the reinforced member, seen through the reinforcing member of Fig. 2(a). In this example, a unidirectional prepreg is disposed on the outermost surface of the reinforced member. Fig. 2(c) is a top view of Fig. 2(b). Figure 3(a) is a perspective view of a composite member similar to Figure 2(a), showing the outermost layer in contact with the adhesive layer of the reinforcing member and the reinforced member. In this example, unidirectional prepregs are disposed on the outermost surfaces of both the reinforcing member and the reinforced member. Figure 3(b) is a top view of Figure 3(a). Fig. 4(a) shows an example of a reinforcing member when the reinforcing member has an in-plane bent shape, and Fig. 4(b) shows an example of a reinforcing member when the reinforcing member has an out-of-plane bent shape. Fig. 5(a) is a top view of the outermost layer in contact with the adhesive layer of the reinforcing member in Fig. 4(a). Fig. 5(b) is a perspective view of the outermost layer in contact with the adhesive layer of the reinforcing member in Fig. 4(b), and is a diagram illustrating the coordinate system x'y' defined for a portion having an out-of-plane bend. Fig. 5(c) is a top view of Fig. 5(b).

Next, we will explain in detail the embodiments of the molded product of the present invention.

The composite member of the present invention comprises a long reinforcing member, a reinforced member, and an adhesive layer, the reinforcing member and the reinforced member being joined via the adhesive layer, and part or all of the outermost layer of the reinforcing member or the reinforced member that contacts the adhesive layer is made of a unidirectional prepreg containing reinforcing fibers and a thermosetting resin, with the orientation direction of the reinforcing fibers of the unidirectional prepreg being within a specific range.

Part or all of the outermost layer in contact with the adhesive layer is made of unidirectional prepreg, and the orientation direction of the reinforcing fibers of the unidirectional prepreg may be within a specific range in only the reinforcing member, only the reinforced member, or both the reinforcing member and the reinforced member.

In other words, if the angle between the orientation direction of the reinforcing fibers of some or all of the unidirectional prepregs in the outermost layer that contacts the adhesive layer of the reinforcing member and the longitudinal direction of the projected length of the reinforcing member in a top view is α, then the composite member of the present invention has an angle of 0° < α < 30°.

Furthermore, if the angle β is defined as the angle between the orientation direction of the reinforcing fibers of part or all of the outermost layer of the unidirectional prepreg that contacts the adhesive layer of the reinforced component and the longitudinal direction of the projected length of the reinforcing component when viewed from above, the composite component of the present invention has a β of 0°<β<30°.

In addition, a preferred embodiment of the composite member of the present invention is one in which 0° < α < 30° and 0° < β < 30°.

The angle α formed in a top view is shown in Figure 1. Figure 1(a) shows a perspective view of an example of a composite member of the present invention, and Figure 1(b) shows a perspective view of the reinforcing member of Figure 1(a) showing the outermost layer in contact with the adhesive layer of the reinforcing member and the reinforced member. In this example, a unidirectional prepreg is disposed on the outermost surface of the reinforcing member. Figure 1(c) shows a top view of Figure 1(b), and the angle α is shown as 5 and 15 in Figure 1(c). Figure 2 also shows an example of the angle β formed in a top view. Figure 2(a) shows a perspective view of an example of a composite member of the present invention, and Figure 2(b) shows a perspective view of the reinforcing member of Figure 2(a) showing the outermost layer in contact with the adhesive layer of the reinforcing member and the reinforced member. In this example, a unidirectional prepreg is disposed on the outermost surface of the reinforced member. Figure 2(c) is a top view of Figure 2(b), and the angle β is illustrated at 6 and 16 in Figure 2(c). Figure 3 also illustrates a structure in which both the angle α and the angle β can be defined simultaneously. Figure 3(a) is a perspective view of a composite member similar to Figure 2(a), showing the outermost layer in contact with the adhesive layer of the reinforcing member and the reinforced member. In this example, unidirectional prepreg is disposed on the outermost surface of both the reinforcing member and the reinforced member. Figure 3(b) is a top view of Figure 3(a), and α and β are illustrated at 5, 15 and 6, 16 in Figure 3(b), respectively.

In the reinforcing member or reinforced member, it is preferable that the angle α or angle β be defined as described above for the entire outermost layer that contacts the adhesive layer. Furthermore, in the case of a long reinforcing member, given that a large load is applied to the longitudinal ends, it is particularly preferable that the angle be defined within a range of 10% of the projected length of the reinforcing member at each of the longitudinal ends of the reinforcing member.

Fiber-reinforced materials, such as carbon fiber prepregs, are brittle when it comes to fracture, and often exhibit the characteristic of rapidly breaking and losing the load when a certain load is exceeded. Furthermore, the load varies. When forming a joint structure using this type of material, if the angle α or angle β is within the above-mentioned angle range, it is easy to induce cohesive failure of the adhesive layer at the joint surface. This means that the reinforcing member or reinforced member, which are the base materials of the joint, are less likely to fracture, resulting in a composite member with improved joint strength.

The range of the angle α or the angle β is preferably 5°<α<25° or 5°<β<25°, and even more preferably 5°<α<15° or 5°<β<15°. When the angle α or the angle β is smaller than 25° or 15°, the reinforcing member or the reinforced member is less likely to break, and the load-bearing capacity of the composite member is further improved. Furthermore, when the angle α or the angle β is greater than 5°, the ability to form complex shapes is improved. As a result, the shape of the joining surface can be stabilized, thereby improving the load-bearing capacity of the composite member.

[Reinforcing member]
The reinforcing member of the present invention is characterized in that its aspect ratio is greater than 1 and less than 1,000,000,000. Here, the aspect ratio of the reinforcing member is defined as the projected length (m) of the reinforcing member divided by the projected width (m) of the reinforcing member. Here, the projected length is defined as the longest dimension along the shape of the projected shape of the reinforcing member when viewed from above, and the projected width is defined as the average dimension of the projected shape when viewed from above in a direction approximately perpendicular to the projected length direction.

The aspect ratio of the reinforcing member is preferably greater than 10 and less than 10,000,000, and more preferably greater than 100 and less than 10,000. Increasing the aspect ratio increases the efficiency of the reinforcing effect in the load direction. Furthermore, while increasing the projected width of the reinforcing member while keeping its projected length the same reduces the aspect ratio, increasing the projected width of the reinforcing member increases the second moment of area of the reinforcing member, improving buckling resistance and enhancing the reinforcing effect.

The reinforcing member, due to its own rigidity, restrains longitudinal deformation of the projected length of the reinforcing member in a composite structure integrated with the reinforced member to which it is joined.

The effect of this reinforcing member is most pronounced when a bending or torsional load is applied to the composite structure. To enhance this effect, it is preferable to select a cross-sectional shape for the reinforcing member with a high moment of inertia. To increase the moment of inertia while also increasing the reinforcing member's lightness, the reinforcing member can be made hollow. Here, "hollow" refers to the formation of a closed space between the reinforcing member and the reinforced member at the cross section where the reinforcing member is joined to the reinforced member. This can be achieved in the form of reinforcing members known as hat stringers or omega stringers.

The reinforcing member can also be shaped to have a twist or bend in the longitudinal direction so as to conform to the shape of the reinforced member. The reinforcing member has a portion for joining to the reinforced member, which may be flat or curved. The shape of the joining surface of this reinforcing member matches the shape of the joining surface on the reinforced member side, and when the reinforcing member and the reinforced member are joined together, it is preferable for there to be contact across the joining surface or for there to be a roughly uniform clearance, in order to increase the strength of the joint.

Figure 4 shows a schematic example of the projected length and projected width of a reinforcing member when the reinforcing member has a twisted or bent shape. Figure 4(a) shows an example of a reinforcing member when the reinforcing member has an in-plane bent shape, and Figure 4(b) shows an example of a reinforcing member when the reinforcing member has an out-of-plane bent shape.

When a reinforcing member has a twisted or bent shape, the longitudinal direction of the projected length of the reinforcing member is defined as the longitudinal direction of the projected length when viewed from above along the shape at each position of the longitudinal shape. Figure 5 shows a schematic example of the longitudinal direction of the projected length defined along the shape and the top view direction. Figure 5(a) shows a perspective view of the reinforcing member in Figure 4(a), with the outermost layer in contact with the adhesive layer shown from above. In this example, the orientation angle of the reinforcing fibers in the outermost layer is constant in space, but the longitudinal direction of the projected length of the reinforcing member changes depending on the longitudinal position of the reinforcing member. Therefore, the magnitude of the angle α varies depending on the longitudinal position of the reinforcing member's projected length. An example of an angle α that varies in magnitude depending on the longitudinal position of the reinforcing member's projected length is shown at 37. Figure 5(b) shows a perspective view of the reinforcing member in Figure 4(b), with the outermost layer in contact with the adhesive layer shown from above. In this example, because the reinforcing member has an out-of-plane bent shape, the top view direction varies depending on the longitudinal position of the reinforcing member's projected length. At both ends of the reinforcing member, the plane approximately perpendicular to the top view direction is the xy plane, while at the central inclined portion of the reinforcing member, the plane approximately perpendicular to the top view direction is the x'y' plane. Figure 5(c) illustrates the angle α defined by the xy plane and the x'y' plane, with Figure 5(b) showing the top view. At both ends of the reinforcing member, the top view direction is approximately perpendicular to the xy plane, so the angle α is defined in the xy plane. At the central inclined portion of the reinforcing member, the top view direction is approximately perpendicular to the x'y' plane, so the angle α is defined in the x'y' plane. In this case, the angle α is shown as 47. While the above example focused on the angle α, the angle β is also defined in the same way.

Prepreg, a component of the reinforcing member of the present invention, is a sheet-like molding material made by impregnating reinforcing fibers with a thermosetting resin.

There are no particular limitations on the type of reinforcing fiber; carbon fiber, glass fiber, aramid fiber, etc. can be used, and a hybrid structure combining these is also possible. A form containing carbon fiber is preferred to increase the strength of the molded product.

The thermosetting resin contained in the prepreg of the present invention can be any of a variety of thermosetting resins. It is preferably at least one selected from epoxy resin, benzoxazine resin, cyanate ester resin, bismaleimide resin, phenolic resin, and modified resins thereof. Epoxy resin is particularly preferred due to its excellent mechanical properties. For applications requiring heat resistance, it is recommended to select cyanate ester resin or bismaleimide resin.

The reinforcing member of the present invention is preferably composed, in part or in whole, of thermosetting unidirectional prepreg. Unidirectional prepreg, which is made by impregnating a fiber sheet in which continuous fibers are aligned in one direction with resin, is a form in which the strength characteristics of the reinforcing fibers are efficiently exhibited. Because it exhibits a high modulus of elasticity and strength in the orientation direction of the reinforcing fibers, a laminate of unidirectional prepregs may be used to give the reinforcing member the desired thickness, rigidity, and strength. A laminated composite plate, obtained by stacking unidirectional prepregs with varying fiber angles and then baking them to impart isotropic properties, is suitable for use as a reinforced member.

An example of a form of reinforced member that is easy to produce is a molded product made from a metal material. In this case, aluminum alloys are preferred due to their balance of light weight and strength, and aluminum-lithium alloys are particularly preferred.

Autoclave molding, press molding, and ultraviolet irradiation are preferred methods for producing the reinforcing member of the present invention. Among these, autoclave molding allows for precise application of heat and pressure to the prepreg laminate, thereby improving the quality of the reinforcing member and making it suitable for aircraft applications. Furthermore, when the laminate contains a fiber substrate, the so-called resin transfer molding (RTM) method is preferred. By injecting a matrix resin from the outside of the laminate using vacuum or pressure into the voids in the fiber substrate, filling the voids with resin, and then maintaining the laminate at the desired temperature, curing of the matrix resin and the resin contained in the prepreg is induced, resulting in a baked and hardened laminated composite board. There are no limitations on the type of matrix resin, but the same type of resin as the prepreg can be used. Furthermore, the composition of the matrix resin can be appropriately adjusted to optimize the desired heat resistance, mechanical properties, and impregnation ability into the fiber substrate.

[Reinforced member]
The reinforced member of the present invention is a panel-shaped member. Examples include the so-called outer shell of an aircraft wing or fuselage. In particular, for aircraft and other flying bodies, the reinforced member is required to be lightweight. Increasing the thickness of a panel-shaped member in order to increase its structural rigidity will result in a loss of lightweight properties. Therefore, it is preferable to use the panel-shaped member as a composite member integrated with the above-mentioned reinforcing member.

The material used to construct the reinforced member can be the same as the material used for the reinforcing member.

Unidirectional prepregs, which are made by impregnating aligned reinforcing fibers with thermosetting resin, are highly compatible with automated tape layup (ATL) systems, making them preferable because they can dramatically increase productivity, especially when the reinforced component is in the form of a large panel.

One form of reinforced member that is highly manufacturable is a sheet metal molded product made from a metal material. In this case, aluminum alloys are preferred for their balance of light weight and strength, with aluminum-lithium alloys being particularly preferred.

The reinforced member of the present invention is joined to the reinforcing member via an adhesive layer. Therefore, when the reinforcing member bears the main load, the outermost layer of the reinforced member to which the load is transmitted bears a load of the same magnitude but in the opposite direction to the load, in accordance with the third law of motion. Therefore, it is preferable that the outermost layer of the reinforced member that contacts the adhesive layer have the same load-bearing capacity as the outermost layer that contacts the adhesive layer of the reinforcing member.

[Adhesive layer]
The adhesive layer according to the present invention, interposed between the reinforcing member and the reinforced member, functions to distribute the external force applied to the composite member between the reinforcing member and the reinforced member, thereby enabling the composite member to acquire the designed rigidity and strength.

In order to ensure a strong bond and not impair the lightweight nature of the composite material, it is preferable that the components of the adhesive layer be selected from resin materials.

The thermosetting resin used in the adhesive layer is preferably at least one selected from the group consisting of epoxy resin, benzoxazine resin, cyanate ester resin, bismaleimide resin, and phenolic resin.

When combining materials through adhesion, uncured resin materials are placed as an adhesive layer between the reinforcing and reinforced members, which have been cured and solidified, and heat and pressure are applied to solidify the adhesive layer, resulting in a bonded composite member. Even when the reinforcing or reinforced members are in an uncured state, a resin material that will form an adhesive layer can be applied or placed between them, and the thermosetting resin contained in the reinforcing or reinforced members can be solidified while the adhesive layer is hardened to obtain a composite member.

Solidification of the adhesive layer can be carried out in an autoclave or similar molding device with heating and/or pressure mechanisms.

Furthermore, it is possible to manufacture reinforcing members and reinforced members with adhesive components made of thermoplastic resin fixed to their surfaces, and then join the members by using the thermoplastic resin on the surface of each member as an adhesive layer.

An example of a method for manufacturing reinforcing members and reinforced members is to laminate a sheet of thermoplastic resin, which serves as the adhesive component, onto the outermost layer of a prepreg containing a thermosetting resin, and then, while maintaining the temperature above the melting point of the thermoplastic resin, apply pressure to form the prepreg into the desired shape, integrating the prepreg and thermoplastic resin.

Preferably, the composite member is characterized by the reinforcing member and the reinforced member being joined by thermal welding. One example of a method for joining is to heat the area to be joined using infrared rays, a laser, or other means, and then press the reinforcing member and the reinforced member together to weld them. Alternatively, ultrasonic welding or induction welding can also be used.

The form of the sheet-like material made of thermoplastic resin is not particularly limited, but from the standpoint of ease of handling, it is preferable to use a nonwoven fabric, film, mat, woven fabric, knitted fabric, or a cloth made of aligned, continuous resin fibers sealed and fixed in shape (so-called NCF: Non-crimp fabric). A nonwoven fabric form with excellent uniformity of basis weight is preferred, as it can provide a uniform layer of thermoplastic resin on the surface of the molded product.

When the thermosetting resin contained in the prepreg has a low melt viscosity, a film form can be preferably selected. A non-porous film has the advantage of effectively preventing the thermosetting resin from leaking from the prepreg onto the surface of the molded product, allowing a thermoplastic resin layer with high purity to be formed on the surface of the molded product.

The thermoplastic resin used in the adhesive layer can be at least one selected from polyamide resin, polyester resin, polyphenylene sulfide resin, polyacetal resin, polyphenylene oxide resin, polycarbonate resin, polylactic acid resin, polypropylene resin, thermoplastic polyimide resins including polyimide resin (PI resin) and polyamideimide resin (PAI resin), polyaryletherketone resins including polyetheretherketone resin (PEEK resin) and polyetherketoneketone resin (PEKK resin), aromatic polyethersulfone resins including polysulfone resin (PSU resin), polyethersulfone resin (PES resin) and polyphenylenesulfone resin (PPSU resin), and modified resins thereof. From the perspective of achieving both moldability and heat resistance in the molded product, at least one selected from polyamide resin, polyphenylene sulfide resin, polyetherketoneketone resin, and polyetheretherketone resin is preferably used.

It is preferable that the adhesive layer contains reinforcing fibers that make up at least one or both of the reinforcing member and the reinforced member. The presence of both the reinforcing fibers of the reinforcing member and the reinforced member within the adhesive layer reduces stress disturbances within the adhesive layer. As a result, the number of high-stress areas in the adhesive layer is reduced, which can be seen as an example of a configuration with increased bonding strength.

In the composite member of the present invention, the thickness of the adhesive layer is preferably 10 μm or more and less than 500 μm. If the adhesive layer is too thin, it may not be able to absorb the difference in shape between the reinforcing member and the reinforced member (so-called dimensional error between the members), which is likely to lead to poor adhesion. Even if the thickness is too thick, the adhesive layer is more likely to contain air bubbles, which is one factor in reducing the strength of the joint. In terms of increasing joint strength, the thickness of the adhesive layer is more preferably 12 μm or more and less than 150 μm, and even more preferably 15 μm or more and less than 50 μm.

The adhesive layer may contain fillers to control its strength and thickness. Examples of such fillers include fibrous fillers such as glass fiber, milled glass fiber, carbon fiber, potassium titanate whisker, zinc oxide whisker, aluminum borate whisker, aramid fiber, alumina fiber, silicon carbide fiber, ceramic fiber, asbestos fiber, gypsum fiber, and metal fiber; wollastonite, zeolite, sericite, kaolin, mica, clay, pyrophyllite, bentonite, asbestos, talc, and silicates such as alumina silicate; metal compounds such as alumina, silicon oxide, magnesium oxide, zirconium oxide, titanium oxide, and iron oxide; carbonates such as calcium carbonate, magnesium carbonate, and dolomite; sulfates such as calcium sulfate and barium sulfate; hydroxides such as magnesium hydroxide, calcium hydroxide, and aluminum hydroxide; and non-fibrous fillers such as glass beads, ceramic beads, boron nitride, and silicon carbide. These fillers may be hollow, and two or more of these fillers may be used in combination. Furthermore, it is preferable to pre-treat these fibrous or non-fibrous fillers with a coupling agent such as an isocyanate compound, an organosilane compound, an organotitanate compound, an organoborane compound, or an epoxy compound before use, in order to obtain better mechanical properties.

When using such fillers to improve strength and dimensional stability, there are no particular restrictions on the amount used, but it is preferable to use 50 to 400 parts by weight per 100 parts by weight of thermoplastic resin.

To improve the mechanical properties of the adhesive layer and increase bonding strength, the adhesive layer may contain a fibrous substrate. Such fibrous substrates are preferably in the form of woven fabric, knitted fabric, or nonwoven fabric. These types of fibrous materials have the advantage of being highly formable, making them less likely to wrinkle when shaped, and highly adaptable to the clearance between the reinforcing material and the reinforced material. There are no particular restrictions on the type of fiber used in the fibrous substrate; carbon fiber, glass fiber, aramid fiber, etc. can be used, and a hybrid structure combining these is also possible.

The present invention will be explained in detail below using examples, but the present invention is not limited to the descriptions in these examples.

[Raw materials]
Reinforcement fiber: Carbon fiber "TORAYCA" (registered trademark) T800S, manufactured by Toray Industries, Inc.
Thermosetting resin: Epoxy resin 3900-2 manufactured by Toray Industries, Inc.
Thermoplastic resin: Polyamide 6 resin (melting point 225°C, weight average molecular weight 30,000) manufactured by Toray Industries, Inc.

[Molding material]
Prepreg: A unidirectional prepreg was produced by placing resin films made of epoxy resin 3900-2 on the top and bottom surfaces of a fiber substrate made of unidirectionally aligned carbon fiber T800S, and impregnating the fiber bundles with the resin using a hot melt method. The prepreg had a thickness of 0.20 mm and a carbon fiber volume content of 52%.
Film adhesive: Thermosetting epoxy adhesive FM-300 manufactured by SOLVAY S.A.
Sheet-like material: Polyamide 6 resin was press-molded at a resin temperature of 300°C to form a thin film, which was then cooled to room temperature at a cooling rate of 50°C/min to obtain a film. The film had a basis weight of 102 g/ ^m2 .

Example 1
The prepregs, each 30 cm square, were laminated in a planar shape in the order of [5/-85] _2s to form a laminate. This laminate was placed in a sealing material, and while evacuating, autoclave molding was carried out under the conditions of a maximum temperature of T = 180 ° C, a pressure of 0.4 MPa, and a holding time of 3 hours to obtain a reinforced member.

In addition, 30 cm x 25 cm square prepregs were laminated in the order of [5/-85] _2s on a hat-shaped forming mold to obtain a hat-shaped laminate having a projected length dimension of 30 cm, a projected width dimension of 150 mm, and an aspect ratio of 2. In the laminate, portions in contact with the adhesive layer were provided at both ends in the projected width direction of the laminate, and the projected width direction dimension of the portions in contact with the adhesive layer was 5 cm at each end. This laminate was placed in a sealing material, and while performing evacuation, a reinforcing member was obtained by autoclave molding under conditions of a maximum temperature of T = 180 ° C, a pressure of 0.4 MPa, and a holding time of 3 hours.

The reinforcing member and the reinforced member were overlapped with a film adhesive placed between them to form a molding material. This molding material was placed inside a sealing material, and while vacuuming, the two members were joined at a maximum temperature of T = 180°C, a pressure of 0.3 MPa, and a holding time of 1 hour to obtain a composite molded product. When overlapping the reinforcing member and the reinforced member, the reinforcing member and the reinforced member were positioned so that the projected length direction of the reinforcing member matched the orientation angle of the reinforcing fibers in the outermost layer that contacted the adhesive layer of the reinforced member. At this time, the angle α = 5° and the angle β = 5°.

A four-point bending load was applied to the resulting composite molded product using a testing machine, causing bending deformation in the projected length direction of the reinforcing member until failure occurred at the joint. After failure, magnified observation of the area near the joint surface of the composite molded product under a microscope revealed that the failure occurred at the joint surface due to cohesive failure of the adhesive layer.

Furthermore, a joint-shaped test piece was cut from the resulting composite molded product, with the projected length direction of the reinforcing member as the load direction, and a single lap shear test was conducted in accordance with ISO 4587-2003. The joint strength was 28 MPa. After failure, magnified observation of the area near the joint surface of the test piece under a microscope revealed that the joint surface had been destroyed by cohesive failure of the adhesive layer.

Example 2
The lamination order when laminating prepregs to obtain a reinforced member was set to [20/-70] _2s , and the lamination order when laminating prepregs to obtain a reinforcing member was set to [20/-70] _2s . Except for this, a reinforcing member and a reinforced member were prepared in the same manner as in Example 1, and the two were joined together in the same manner as in Example 1 to obtain a composite molded product. At this time, the formed angle α = 20° and the formed angle β = 20°.

A joint-shaped test piece was cut from the resulting composite molded product in the same manner as in Example 1, and the bond strength was evaluated, finding it to be 24 MPa. After fracture, the test piece was observed under a microscope near the bonded surface, revealing that the fracture occurred due to cohesive failure of the adhesive layer at the bonded surface.

Example 3
A laminate was prepared by stacking 30 cm square prepregs in the order of [5/-85] _2s in a planar shape, and then placing a similar 30 cm square sheet on top of it. This laminate was placed in a mold and molded under conditions of an initial mold temperature Ti = 240 ° C, a pressure of 2.2 MPa, and a pressure holding time of 15 minutes. After that, while maintaining the mold temperature, the laminate was removed from the mold at a final mold temperature Te = 90 ° C at the time of demolding, and a reinforced member with the sheet as an adhesive layer was obtained.

In addition, a 30 cm x 25 cm square sheet was placed in a hat-shaped forming mold, and similarly, a 30 cm x 25 cm square prepreg was laminated on the sheet in the order of [5/-85] _2s to obtain a hat-shaped laminate having a projected length dimension of 30 cm, a projected width dimension of 150 mm, and an aspect ratio of 2. In the laminate, a portion in contact with the adhesive layer was provided at both ends in the projected width direction of the laminate, and the projected width direction dimension of the portion in contact with the adhesive layer was 5 cm at each end. This laminate was placed in a mold and molded under conditions of an initial mold temperature Ti = 240 ° C, a pressure of 2.2 MPa, and a pressure holding time of 15 minutes. Then, while maintaining the mold temperature, it was removed from the mold at a final mold temperature Te = 90 ° C at the time of demolding to obtain a reinforcing member.

The reinforcing member and the reinforced member were overlapped so that the surfaces of the thermoplastic resin layer of each member were in contact with each other, and the two members were joined at a mold temperature of 250°C, a pressure of 1.0 MPa, and a pressure holding time of 4 minutes to obtain a composite molded product. When overlapping, the reinforcing member and the reinforced member were positioned so that the projected length direction of the reinforcing member matched the orientation angle of the reinforcing fibers in the outermost layer that contacted the adhesive layer of the reinforced member. At this time, the angle α = 5° and the angle β = 5°.

A four-point bending load was applied to the resulting composite molded product, as in Example 1. After fracture, the vicinity of the bonded surface of the composite molded product was observed under a microscope at a magnification; it was found that the fracture was due to cohesive failure of the adhesive layer at the bonded surface. Furthermore, a joint-shaped test piece was cut out from the resulting composite molded product, as in Example 1, and the bond strength was evaluated, which was found to be 44 MPa. After fracture, the vicinity of the bonded surface of the test piece was observed under a magnification microscope; it was found that the fracture was due to cohesive failure of the adhesive layer at the bonded surface.

Example 4
The lamination order when laminating prepregs to obtain a reinforced member was set to [20/-70] _2s , and the lamination order when laminating prepregs to obtain a reinforcing member was set to [20/-70] _2s . The reinforcing member and the reinforced member were prepared in the same manner as in Example 3, and then they were joined together in the same manner as in Example 3 to obtain a composite molded product. At this time, the formed angle α = 20° and the formed angle β = 20°.

A joint-shaped test piece was cut from the resulting composite molded product in the same manner as in Example 1, and the bond strength was evaluated, finding it to be 30 MPa. After fracture, the test piece was observed under a microscope near the bonded surface, revealing that the fracture occurred due to cohesive failure of the adhesive layer at the bonded surface.

Comparative Example 1
The lamination order when laminating prepregs to obtain a reinforced member was set to [30/-60] _2s , and the lamination order when laminating prepregs to obtain a reinforcing member was set to [30/-60] _2s . Except for this, a reinforcing member and a reinforced member were prepared in the same manner as in Example 1, and the two were joined together in the same manner as in Example 1 to obtain a composite molded product. At this time, the formed angle α = 30° and the formed angle β = 30°.

A joint-shaped test piece was cut from the resulting composite molded product in the same manner as in Example 1, and the bond strength was evaluated, finding it to be 20 MPa. After fracture, the test piece was observed under a microscope near the bonded surface, revealing that the fracture at the bonded surface was due to fracture of the base material of the reinforcing member.

Comparative Example 2
The lamination order when laminating prepregs to obtain a reinforced member was set to [75/-15] _2s , and the lamination order when laminating prepregs to obtain a reinforcing member was set to [75/-15] _2s . Except for this, a reinforcing member and a reinforced member were prepared in the same manner as in Example 1, and the two were joined together in the same manner as in Example 1 to obtain a composite molded product. At this time, the formed angle α = 75° and the formed angle β = 75°.

A joint-shaped test piece was cut from the resulting composite molded product in the same manner as in Example 1, and the bond strength was evaluated, finding it to be 22 MPa. After fracture, the test piece was observed under a microscope near the bonded surface, revealing that the fracture at the bonded surface was due to fracture of the base material of the reinforcing member.

Comparative Example 3
The lamination order when laminating prepregs to obtain a reinforced member was set to [30/-60] _2s , and the lamination order when laminating prepregs to obtain a reinforcing member was set to [30/-60] _2s . Except for this, a reinforcing member and a reinforced member were prepared in the same manner as in Example 3, and both were joined together in the same manner as in Example 3 to obtain a composite molded product. At this time, the formed angle α = 30° and the formed angle β = 30°.

A joint-shaped test piece was cut from the resulting composite molded product in the same manner as in Example 1, and the bond strength was evaluated, finding it to be 20 MPa. After fracture, the test piece was observed under a microscope near the bonded surface, revealing that the fracture at the bonded surface was due to fracture of the base material of the reinforcing member.

Comparative Example 4
The lamination order when laminating prepregs to obtain a reinforced member was set to [75/-15] _2s , and the lamination order when laminating prepregs to obtain a reinforcing member was set to [75/-15] _2s . The reinforcing member and the reinforced member were prepared in the same manner as in Example 3, and then they were joined together in the same manner as in Example 3 to obtain a composite molded product. At this time, the formed angle α = 75° and the formed angle β = 75°.

A joint-shaped test piece was cut from the resulting composite molded product in the same manner as in Example 1, and the bond strength was evaluated, finding it to be 22 MPa. After fracture, the test piece was observed under a microscope near the bonded surface, revealing that the fracture at the bonded surface was due to fracture of the base material of the reinforcing member.

1: Reinforcing member 1
2: Longitudinal direction of the projected length of the reinforcing member 1 3: Outermost layer in contact with the adhesive layer of the reinforcing member 1 4: Orientation direction of the reinforcing fibers in the outermost layer in contact with the adhesive layer of the reinforcing member 1 5: Angle α between the longitudinal direction of the projected length of the reinforcing member 1 and the orientation direction of the reinforcing fibers in the outermost layer in contact with the adhesive layer of the reinforcing member 1
6: Angle β between the longitudinal direction of the projected length of the reinforcing member 1 and the orientation direction of the reinforcing fibers in the outermost layer in contact with the adhesive layer of the reinforced member
11: Reinforcing member 2
12: Longitudinal direction of the projected length of the reinforcing member 2 13: Outermost layer in contact with the adhesive layer of the reinforcing member 2 14: Orientation direction of the reinforcing fibers in the outermost layer in contact with the adhesive layer of the reinforcing member 2 15: Angle α between the longitudinal direction of the projected length of the reinforcing member 2 and the reinforcing fiber direction in the outermost layer in contact with the adhesive layer of the reinforcing member 2
16: Angle β between the longitudinal direction of the projected length of the reinforcing member 2 and the orientation direction of the reinforcing fibers in the outermost layer in contact with the adhesive layer of the reinforced member
21: Reinforced member 22: Orientation direction of reinforcing fibers of the reinforced member 31: Reinforcing member 3 having an in-plane bent shape
32: Projected shape of the reinforcing member 3 as viewed from above 33: Approximate dimension of the projected length of the reinforcing member 3 34: Approximate dimension of the projected width of the reinforcing member 3 35: Longitudinal direction of the projected length of the reinforcing member 3 36: Orientation direction of the reinforcing fibers in the outermost layer in contact with the adhesive layer of the reinforcing member 3 37: Angle α formed between the longitudinal direction of the projected length of the reinforcing member 3 and the orientation direction of the reinforcing fibers in the outermost layer in contact with the adhesive layer of the reinforcing member 3
41: Reinforcing member 4 having an out-of-plane bent shape
42: Projected shape of the reinforcing member 4 as viewed from above 43: Approximate dimension of the projected length of the reinforcing member 4 44: Approximate dimension of the projected width of the reinforcing member 4 45: Longitudinal direction of the projected length of the reinforcing member 4 46: Orientation direction of the reinforcing fibers in the outermost layer in contact with the adhesive layer of the reinforcing member 4 47: Angle α formed between the longitudinal direction of the projected length of the reinforcing member 4 and the orientation direction of the reinforcing fibers in the outermost layer in contact with the adhesive layer of the reinforcing member 3
48: A portion of the outermost layer of the reinforcing member 4 that is in contact with the adhesive layer and is parallel to the xy plane. 49: A portion of the outermost layer of the reinforcing member 4 that is in contact with the adhesive layer and is parallel to the x'y' plane.

The composite member of the present invention has high load-bearing capacity and can therefore be suitably used in mobile objects including aircraft, sports applications, and electronic device housings, which require high reliability.

Claims (9)

A composite component in which a reinforcing member having an aspect ratio greater than 1 and smaller than 1,000,000,000 according to the following formula (1) is joined to a reinforced member via an adhesive layer, wherein the adhesive layer contains reinforcing fibers that constitute at least one or both of the reinforcing member and the reinforced member, and a part or all of the outermost layer of the reinforcing member that contacts the adhesive layer is made of a unidirectional prepreg containing reinforcing fibers and a thermosetting resin, and the angle α between the orientation direction of the reinforcing fibers of the unidirectional prepreg and the longitudinal direction of the projected length of the reinforcing member in a top view is 0°<α<30°.
Aspect ratio = Projected length of reinforcing member (m) / Projected width of reinforcing member (m) (1) A composite component in which a reinforcing member having an aspect ratio greater than 1 and smaller than 1,000,000,000 according to the following formula (1) is joined to a reinforced member via an adhesive layer, wherein the adhesive layer contains reinforcing fibers that constitute at least one or both of the reinforcing member and the reinforced member, and a part or all of the outermost layer of the reinforced member that contacts the adhesive layer is made of a unidirectional prepreg containing reinforcing fibers and a thermosetting resin, and the angle β between the orientation direction of the reinforcing fibers of the unidirectional prepreg and the longitudinal direction of the projected length of the reinforcing member in a top view is 0°<β<30°.
Aspect ratio = Projected length of reinforcing member (m) / Projected width of reinforcing member (m) (1) A composite member in which a reinforcing member having an aspect ratio of greater than 1 and less than 1,000,000,000 according to the following formula (1) is joined to a reinforced member via an adhesive layer, wherein a part or all of the outermost layer of the reinforcing member in contact with the adhesive layer is made of a unidirectional prepreg containing reinforcing fibers and a thermosetting resin, and the angle α between the orientation direction of the reinforcing fibers of the unidirectional prepreg and the longitudinal direction of the projected length of the reinforcing member in a top view is 0° < α < 30°, and a part or all of the outermost layer of the reinforced member to which the reinforcing member is joined is made of a unidirectional prepreg containing reinforcing fibers and a thermosetting resin, and the angle β between the orientation direction of the reinforcing fibers of the unidirectional prepreg and the longitudinal direction of the projected length of the reinforcing member in a top view is 0° < β < 30°.
Aspect ratio = Projected length of reinforcing member (m) / Projected width of reinforcing member (m) (1) The composite member according to any one of claims 1 to 3, wherein the adhesive layer is made of a thermosetting resin. The composite material described in claim 4, wherein the thermosetting resin is at least one selected from epoxy resin, benzoxazine resin, cyanate ester resin, bismaleimide resin, and phenolic resin. A composite member according to any one of claims 1 to 3, wherein the adhesive layer is made of a thermoplastic resin. The composite member according to claim 6, wherein the thermoplastic resin is at least one selected from polyamide resin, polyphenylene sulfide resin, polyether ketone ketone resin, and polyether ether ketone resin. 4. The composite member according to claim 3 , wherein the adhesive layer contains reinforcing fibers that constitute at least one of the reinforcing member and the reinforced member. The composite material according to any one of claims 1 to 8, wherein the adhesive layer has a thickness of 10 µm or more and less than 500 µm.