JP7263619B2 - Joining method and joined body - Google Patents

Description

The present disclosure relates to methods and articles for joining fiber reinforced thermoplastics (FRTP).

As a method for joining members to be joined made of FRTP, bolting, fusion and adhesion (see Patent Document 1) are known.

In bolt connection, members to be joined are fixed with bolts and nuts. In fusion bonding, members to be joined are joined together by melting the base material (thermoplastic resin) of FRTP. In adhesion, members to be joined are joined together using an adhesive.

JP 2016-175331 A

However, the above joining methods each have their own problems.

Bolted joints have a low bolted joint strength, and it is necessary to increase the plate thickness of the members to be joined. Moreover, when drilling, bolting, and sealing operations are performed at many locations, the number of assembling man-hours increases and the weight of the product increases. Furthermore, in the use of bolts and nuts, there is concern about electrolytic corrosion when using carbon fibers as reinforcing fibers.

In fusion bonding, since the base material of the member to be joined is melted, it is difficult to control the plate thickness and shape. In addition, the melting of the base material may cause the reinforcing fibers contained in the members to be joined to undulate.

In adhesion, since a material different from the adherend is used as an adhesive, there are problems such as deterioration of the adhesion interface and additional costs. Thermosetting resins are mainly used as structural adhesives. Thermosetting resins used as structural adhesives include epoxy resins. Epoxy resin loses strength due to moisture absorption, and its heat resistance and toughness may differ greatly from those of the adherend (base material).

As a bonding method other than the above, bonding using plasma processing is being considered. When a member to be joined made of FRTP is irradiated with plasma, the surface of the member is activated and a functional group such as a hydroxyl group is introduced. When the surfaces to which the functional groups have been introduced are brought together and heated and pressurized, the functional groups are chemically reacted and bonded. In the method using plasma treatment, the base material of FRTP is heated at a temperature below the melting point of the base material, so the base material is not melted. Therefore, the plate thickness and shape do not change due to melting, and the reinforcing fibers do not undulate.

However, the method using plasma treatment also has room for improvement. For example, as shown in FIG. 7, the surfaces of the FRTP that become the members to be joined 21 and 22 are not flat. When the non-flat surfaces are brought together, a gap G is generated between the surface to be bonded _S21 and the surface to be bonded _S22 . In the gap G portion, since the surfaces cannot be joined together, the joining force becomes weak.

The present disclosure has been made in view of such circumstances, and a bonding method capable of improving the strength of bonding in bonding between FRTPs by activating the surfaces to be bonded, and a bonded body bonded by the method intended to provide

In order to solve the above problems, the joining method and joined body of the present disclosure employ the following means.
The present disclosure relates to a joining method for joining members to be joined that are made of a fiber-reinforced thermoplastic whose base material is a thermoplastic resin, and wherein a resin layer is formed on one surface of the member to be joined. activating the outer surface of the resin layer to introduce an active functional group capable of causing a chemical bond ; and placing the members to be joined together with the activated outer surfaces of the resin layer facing each other. The present invention provides a joining method for heating and pressurizing the members to be joined in a superimposed state so that the temperature of the base material is maintained below the melting point.

The present disclosure relates to a joined body in which members to be joined are made of a fiber-reinforced thermoplastic whose base material is a thermoplastic resin, and the members to be joined are joined to each other, and a resin layer is provided on one surface of the members to be joined. The outer surface of the resin layer is activated to introduce an active functional group capable of causing a chemical bond, and the two members to be joined are stacked with the activated outer surfaces of the resin layers facing each other. Provided is a joined body formed by heating and pressurizing the members to be joined in a superimposed state so that the temperature of the base materials is maintained below the melting point.

According to the above disclosure, by providing a resin layer and activating the resin layer, the amount of functional groups on the surfaces to be bonded increases and the resin becomes more mobile. As the amount of functional groups increases, the portion that can be joined increases. By making the resin easy to move, the opportunities for chemical reactions between functional groups can be increased. As a result, the bonding strength of the bonding surfaces is improved.

The surfaces to be joined of the members to be joined are smoothed by forming the resin layer. By aligning the smoothed surfaces, the gap between the surfaces can be eliminated or reduced. As a result, it is possible to reduce portions that cannot be joined between the surfaces to be joined. Elimination or reduction of the gap increases the chances that the functional groups on the facing surfaces meet with a reaction partner. As a result, it is possible to stably obtain a bonded body with improved bonding strength.

It is a figure explaining superposition|superposition of a to-be-joined member. FIG. 2 is an exploded view taken along the line AA of FIG. 1; FIG. 2 is a cross-sectional view of a joined body joined by the joining method according to the first embodiment; FIG. 10 is a cross-sectional view of members to be joined on which a resin layer is formed according to a second embodiment; 1 is a cross-sectional view of an example second thermoplastic prepreg; FIG. It is a figure which joins about the joining method which concerns on 2nd Embodiment. It is a figure explaining the to-be-joined member which overlapped by the conventional method.

[First embodiment]
In this embodiment, a method for joining members to be joined will be described.

(Member to be joined)
The members to be joined are made of fiber reinforced thermoplastic (FRTP). The member to be joined may be composed of a single layer of FRTP, or may be composed of a plurality of layers of FRTP. In this embodiment, the members to be joined are those after molding the FRTP.

FRTP includes a thermoplastic resin and reinforcing fibers. Thermoplastic resin is the base material (matrix) of FRTP.

Thermoplastic resins are not particularly limited, but may be super-engineered plastics such as polyaryletherketone (PAEK), polyphenylene sulfide (PPS), polyetherimide (PEI), and liquid crystal polymer (LCP). PAEKs are, for example, polyetheretherketone (PE EK ), polyetherketoneketone (PEKK) and low melting point PAEK (LM PAEK).

The reinforcing fibers may be inorganic fibers or organic fibers. Inorganic fibers include carbon fibers, glass fibers, silicon carbide fibers, and the like. Organic fibers include aramid fibers, polyparaphenylene-benzobis-oxazole (PBO) fibers, polyarylate fibers, and PEEK fibers. The reinforcing fibers may be in the form of unidirectionally oriented fiber bundles, wovens and nonwovens.

The thermoplastic resins contained in the two members to be joined may be the same or different. The reinforcing fibers contained in the two joined members to be joined may be of the same type or of different types. The forms of reinforcing fibers contained in the two members to be joined may be the same or different.

The joining method according to this embodiment includes the following steps.
(S1) Formation of resin layer (S2) Activation treatment (S3) Joining members to be joined

(S1) Resin layer formation A resin layer is formed on one surface of the member to be joined.
The resin layer is formed by superimposing the material of the resin layer on one surface of the member to be joined and applying heat and pressure. One surface of the member to be joined and the surface of the material of the resin layer are activated in advance. The member to be joined and the resin layer are superimposed on each other with the activated surfaces facing each other.

One surface of the member to be joined covered with the resin layer becomes smoother than before being covered with the resin layer.

A resin film is used as the material of the resin layer. The thickness of the resin film is desirably less than 250 μm. The thickness of the resin film is preferably equal to or larger than the radius of the reinforcing fibers included in the members to be joined. As a result, even if the reinforcing fibers are exposed on one surface of the member to be joined, the gaps between the fiber bundles can be filled.

The resin film is made of thermoplastic resin. The resin film has heat resistance equivalent to that of the base material. Equivalent heat resistance means that the strength and function of the base material are not substantially affected at the operating environmental temperature of the product in which the members to be joined are joined. For example, when the base material is PEEK, PEEK and PAEK such as PEKK can be used as the thermoplastic resin of the resin film.

The thermoplastic resin used for the resin film may be the same material as the base material of the member to be joined.

The thermoplastic resin used for the resin film may be a material having a higher melting point than the base material of the member to be joined. Since the resin film, which has a higher melting point than the base material, does not melt when heated and pressed during bonding, it is easy to ensure the thickness of the resin layer.

The thermoplastic resin used for the resin film may be a material having a lower melting point than the base material of the member to be joined. When using a resin film having a lower melting point than the base material, it is preferable to use a nonwoven fabric or a woven fabric as the material of the resin layer together with the resin film. A nonwoven or woven fabric is inserted as a spacer between the resin film and the base material. By interposing the spacer, it is possible to prevent the resin of the resin film from being absorbed by the base material. Thereby, a resin layer can be formed more reliably.

Nonwovens and woven fabrics are made from inorganic or organic fibers.

Inorganic fibers include carbon fibers and glass fibers. Non-woven fabrics or woven fabrics made of inorganic fibers do not contribute much to the joining force during joining, so it is desirable to make them as low as possible. The “low basis weight” is at least equal to or less than the basis weight of the reinforcing fibers of the base material, preferably 10 g/m ² or less.

Organic fibers include aramid fibers and PEEK fibers. It is desirable that the organic fibers have a higher melting point than the base material.

When a spacer is interposed, both sides or one side of the spacer should be activated before being inserted between the member to be joined and the resin film. The activation treatment facilitates impregnation of the spacer (nonwoven fabric) with the resin.

By "activated" is meant the introduction of active functional groups that cause chemical bonding. Activation can be performed by methods such as plasma treatment, ultraviolet (UV) treatment, vacuum ultraviolet (VUV) treatment, flame treatment, and chemical solution treatment.

When activation is performed by plasma treatment, plasma is first applied to each of one surface of the member to be joined and one surface of the resin film. For example, an oxygen-containing active functional group (hereinafter referred to as a functional group) is introduced to a surface irradiated with oxygen-containing plasma. When a nonwoven fabric is used as the spacer, plasma is applied to both sides or one side of the nonwoven fabric. In the case of a nonwoven fabric with a low basis weight, plasma passes through the back side as well, so both sides can be activated by irradiating only one side.

A plasma irradiation apparatus using a known plasma generation technique can be used for plasma irradiation. Plasma irradiation to large parts (members) is desirably carried out by an atmospheric pressure plasma irradiation apparatus. Plasma irradiation to the small member may be carried out by a low-pressure plasma irradiation apparatus.

A plasma can be formed by any gas. The plasma can be formed from at least one substance that is gaseous at room temperature, such as air, oxygen, nitrogen, carbon dioxide, water vapor, helium, neon, argon, and the like.

The conditions for plasma irradiation are appropriately selected according to the type of plasma irradiation device, the material of the member to be irradiated such as the resin film and the member to be joined, the required bonding strength, and the state of one surface of the member to be joined. should be.

Functional groups that can be introduced by irradiation with oxygen-containing plasma include a hydroxyl group, a carboxyl group, and a carbonyl group. The same type of functional groups or different types of functional groups may be generated on the surfaces to be bonded between the members to be bonded. By selecting the type of plasma to be irradiated, the types of functional groups to be introduced can be controlled.

Heating and pressing are not particularly limited, but can be carried out, for example, with a hot press machine, rollers, or the like. It should be noted that the heating and pressurization may be a combination of mechanisms. For example, it can be pressurized with a transparent block and heated with a laser, sandwiched between blocks and energized, and the like.

When a resin film having a higher melting point than the base material is used, the heating and pressurization should be carried out under conditions that soften the base material. “Softening” means that the elastic modulus decreases beyond the glass transition temperature. More specifically, the heating and pressing are desirably performed under the condition that the base material exceeds the glass transition temperature.

When using a resin film having a higher melting point than the base material, the heating and pressurization may be performed under the condition that the base material melts. At this time, it is possible to suppress the waviness of the reinforcing fibers of the base material by firmly applying pressure to the same level as the molding pressure of the base material. Alternatively, heating and pressurization may be performed so that the undulating region is removed from the final product, and the undulating portion may be cut off after the resin layer is formed.

When a resin film having a melting point higher than that of the base material is used, the heating temperature of the members to be joined may be increased and the pressure may be increased to ensure the bonding strength. At this time, deformation may occur in the members to be joined. When heating and pressing under such conditions, a base material larger than the product size is prepared, and the deformed portion of the member to be joined is removed after forming the resin layer.

When a resin film having a melting point lower than that of the base material is used, it softens at a temperature lower than that of the base material, so deformation of the base material of the member to be joined due to heating and pressure during joining can be avoided. This eliminates the need for additional processing after forming the resin layer.

(S2) Activation Processing The surfaces to be joined of the members to be joined are activated. Activation can be performed by methods such as plasma treatment, ultraviolet (UV) treatment, vacuum ultraviolet (VUV) treatment, flame treatment, and chemical solution treatment. In the present embodiment, the following description is based on the assumption that the surfaces to be bonded are activated by plasma processing.

In the plasma treatment, first, the surfaces to be bonded are irradiated with plasma. In the member to be joined on which the resin layer is formed, the outer surface of the resin layer (the surface not in contact with the member to be joined) is the surface to be joined.

A plasma irradiation apparatus using a known plasma generation technique can be used for plasma irradiation. Plasma irradiation to large parts (members) is desirably carried out by an atmospheric pressure plasma irradiation apparatus. Plasma irradiation to the small member may be carried out by a low-pressure plasma irradiation apparatus.

A plasma can be formed by any gas. The plasma can be formed from at least one substance that is gaseous at room temperature, such as air, oxygen, nitrogen, carbon dioxide, water vapor, helium, neon, argon, and the like.

Conditions for plasma irradiation may be appropriately selected according to the type of plasma irradiation device, materials of the resin layer and members to be joined, required joining strength, condition of the surfaces to be joined, and the like.

By irradiating the surfaces to be bonded with plasma, functional groups are introduced into the surfaces to be bonded. For example, functional groups that can be introduced by irradiation with oxygen-containing plasma include a hydroxy group, a carboxy group, and a carbonyl group. The same type of functional groups or different types of functional groups may be generated on the surfaces to be bonded between the members to be bonded. By selecting the type of plasma to be irradiated, the types of functional groups to be introduced can be controlled.

(S3) Joining members to be joined After the activation process, the members to be joined 1 and 2 are overlapped as shown in FIG.

FIG. 2 shows an exploded view taken along the line AA of FIG. A resin layer 3 is formed on one surface of the member 1 to be joined. A resin layer 4 is formed on one surface of the joined member 2 . In FIG. 2, the members to be joined 1 and 2 are arranged so that the surfaces on which the resin layers 3 and 4 are formed (surfaces to be joined S ₁ and S ₂ ) face each other.

The member to be joined 1 and the member to be joined 2 are pressed while being heated while being superimposed. As a result, the functional group on the surface to be joined _S1 and the functional group on the surface to be joined _S2 are chemically bonded, and the member to be joined 1 and the member to be joined 2 are joined.

Heating and pressing are not particularly limited, but can be carried out, for example, with a hot press machine, rollers, or the like. It should be noted that the heating and pressurization may be a combination of mechanisms. For example, it can be pressurized with a transparent block and heated with a laser, sandwiched between blocks and energized, and the like.

Heating and pressing are performed under the condition that the temperature of the base material of the members to be joined 1 and 2 does not exceed the melting point (the temperature can be maintained below the melting point). Heating and pressurization are performed under conditions that allow chemical reaction between the functional groups on the surfaces S ₁ and S ₂ to be joined. Here, "the temperature of the base material does not reach the melting point or higher" is synonymous with "the base material is not melted." When an amorphous thermoplastic resin is used as the base material of FRTP, "the base material is not melted" means "the glass transition temperature of the base material is exceeded, the elastic modulus is significantly reduced, and shape retention becomes impossible. It is synonymous with "not reaching the temperature".

The above conditions are preferably acquired in advance by preliminary tests or the like.

FIG. 3 shows a cross-sectional view of a joined body obtained by joining according to the above embodiment. The joined body 5 includes a joined member 1 (first joined member), a joined member 2 (second joined member), and resin layers 3 and 4 (first resin layer and second resin layer).

The resin layer 3 is arranged so as to cover one surface of the member 1 to be joined. The resin layer 3 is joined to the joined member 1 by chemical bonding.

The resin layer 4 is arranged so as to cover one surface of the joined member 2 . The resin layer 4 is joined to the joined member 2 by chemical bonding.

The resin layer 3 and the resin layer 4 are adjacent to each other. At the contact surface between the resin layer 3 and the resin layer 4, the functional groups on each surface are chemically bonded. By bonding the resin layer 3 and the resin layer 4 together, a bonded body 5 in which the member to be bonded 1 and the member to be bonded 2 are bonded is formed.

[Second embodiment]
This embodiment differs from the first embodiment in that a resin material is used instead of the resin film as the material of the resin layer. Other configurations are the same as those of the first embodiment.

The resin material is made of thermoplastic resin. The resin material has heat resistance equivalent to that of the base material of the member to be joined. The resin material may contain reinforcing fibers.

The thermoplastic resin used for the resin material is preferably the same material as the base material of the member to be joined. The resin material is thicker than the maximum depth of the recesses present in the surfaces to be joined of the members to be joined.

The resin material has a surface (imitation surface) that imitates the shape of the surface to be joined of the member to be joined in which the resin material is to be interposed. For example, the resin material A to be brought into contact with the member A to be joined has a simulated surface and another smooth surface. The imitation surface can be formed by measuring the surface to be joined of the member to be joined by taking a mold using a resin material or the like or by using a three-dimensional scanner or the like, and by simulating the surface based on the measurement result.

FIG. 4 shows a cross-sectional view of members to be joined 11 and 12 on which resin layers 13 and 14 are formed in this embodiment. A resin layer 13 is formed on one surface of the joined member 11 . A resin layer 14 is formed on one surface of the member 12 to be joined. In FIG. 4, the members to be joined 11 and 12 are arranged so that the surfaces on which the resin layers 13 and 14 are formed (surfaces to be joined S ₁₁ and S ₁₂ ) face each other.

For large members such as skin-stringers, it is difficult to obtain the precision of individual parts. If the precision of the part is not good, there is a concern that even if the resin film is interposed and the heat and pressure are applied, a gap that cannot be completely filled will remain. For a product in which it is difficult to achieve such component precision, it is preferable to use a resin material having a surface that follows the surface shape of the member to be joined, and arrange the resin material so that the surface matches the shape of the surface to be joined. As a result, the gap generated between the surfaces to be joined can be more reliably filled, thereby improving the joining strength.

[Third Embodiment]
The joining method according to this embodiment differs from the first embodiment in the procedure for forming the resin layer. The activation process and the joining of members to be joined are performed in the same manner as (S2) and (S3) in the first embodiment.

In this embodiment, a resin layer is formed when molding the member to be joined.

A first thermoplastic prepreg is used as the material of the member to be joined. The first thermoplastic prepreg is a sheet-like intermediate material containing a thermoplastic resin that serves as a base material of the members to be joined and reinforcing fibers. The materials exemplified in the first embodiment can be used for the thermoplastic resin and reinforcing fibers.

At least one of a resin film, a second thermoplastic prepreg, a nonwoven fabric, and a woven fabric is used as a material for the resin layer.

The resin film is made of thermoplastic resin. The resin film has heat resistance equivalent to that of the base material. For example, when the base material is PEEK, PEEK and PAEK such as PEKK can be used as the thermoplastic resin of the resin film.

The thermoplastic resin used for the resin film may be the same material as the base material of the member to be joined. The thermoplastic resin used for the resin film may be a material having a higher melting point than the base material of the member to be joined.

The second thermoplastic prepreg is a sheet-like intermediate material containing a thermoplastic resin and reinforcing fibers. The second thermoplastic prepreg has heat resistance equivalent to that of the first thermoplastic resin. The type of thermoplastic resin and the type and form of reinforcing fibers are desirably the same as those of the first thermoplastic prepreg, but may be different.

The second thermoplastic prepreg has a higher resin content than the first thermoplastic prepreg. The resin content may be appropriately set according to the diameter and type of the reinforcing fiber. The resin content of the second thermoplastic prepreg is desirably set in consideration of the amount necessary to make up for the difference in heat shrinkage between the resins that occurs during cooling.

FIG. 5 shows a cross section of the second thermoplastic prepreg 6 as an example. The second thermoplastic prepreg 6 is preferably composed of a region X in which the thermoplastic resin 7 fills the gaps between the reinforcing fibers 8 and a region Y that covers the region X and does not contain the reinforcing fibers 8 . The term "does not contain" is not limited to the fact that the reinforcing fibers 8 are not contained at all.

Nonwovens and woven fabrics are made from inorganic or organic fibers.

Inorganic fibers include carbon fibers and glass fibers. Non-woven fabrics or woven fabrics made of inorganic fibers do not contribute much to the joining force during joining, so it is desirable to make them as low as possible. The “low basis weight” is at least equal to or less than the basis weight of the reinforcing fibers of the base material, preferably 10 g/m ² or less.

Organic fibers include aramid fibers and PEEK fibers. The organic fiber preferably has a higher melting point than the base material of the first thermoplastic prepreg.

In this embodiment, the resin layer is formed as follows.
First, as shown in FIG. 6, the material 10 of the resin layer is laminated on the laminated first thermoplastic prepreg 9 (outermost surface).

The first thermoplastic prepreg 9 and the material 10 of the resin layer are heated and pressed to be integrally molded. Thereby, a resin layer is formed. The "outermost surface" is on the side that is to become the surface to be joined of the member to be joined after molding.

By using a resin film or a second thermoplastic prepreg having a high resin content as the material, one surface of the member to be joined can be made smoother than when the first thermoplastic prepreg 9 is used as the outermost surface.

When a nonwoven fabric or a woven fabric is used as the material, the thermoplastic resin of the first thermoplastic prepreg permeates into the material due to heating and pressurization during molding. Thereby, a resin layer containing the material is formed.

If the impregnated amount of the thermoplastic resin into the material is insufficient, it is preferable to arrange the resin film on the nonwoven fabric or the woven fabric and integrally mold it with the base material. Alternatively, after forming a resin layer according to this embodiment, another resin layer may be further formed on the resin layer by the method using the resin film described in the first embodiment.

If it is desired to increase the adhesion, one surface of the material of the resin layer is activated, and then laminated with the activated surface facing the first thermoplastic prepreg, followed by integral molding. When combining two or more kinds of materials for the resin layer, each material should be laminated and integrally formed after activating the contact surface with the other material or the first prepreg. Also, one surface of the first thermoplastic prepreg may be activated.

[Fourth embodiment]
The joining method according to this embodiment differs from the first embodiment in the procedure for forming the resin layer. The activation process and the joining of members to be joined are performed in the same manner as (S2) and (S3) in the first embodiment.

A non-woven fabric or a woven fabric is used as the material of the resin layer. Non-woven fabrics and woven fabrics are made of inorganic or organic fibers.

Inorganic fibers include carbon fibers and glass fibers. Non-woven fabrics or woven fabrics made of inorganic fibers do not contribute much to the joining force during joining, so it is desirable to make them as low as possible. The “low basis weight” is at least equal to or less than the basis weight of the reinforcing fibers of the base material, preferably 10 g/m ² or less.

Organic fibers include aramid fibers and PEEK fibers. It is desirable that the organic fiber has a higher melting point than the base material of the member to be joined.

The resin layer is formed by superimposing the material of the resin layer on one surface of the member to be joined and applying heat and pressure.

In this embodiment, the heating and pressurization for forming the resin layer is performed under the condition that the temperature of the base material of the members to be joined reaches the melting point or higher.

The base material melts when the temperature exceeds the melting point. The resin layer is formed by the melted base material (thermoplastic resin) soaking into the material of the resin layer.

If the amount of the thermoplastic resin impregnated into the material of the resin layer is insufficient, the first embodiment may be combined to further form a resin layer using a resin film.

If the amount of impregnation of the thermoplastic resin into the material of the resin layer is predicted to be insufficient, or if it is desired to more reliably impregnate the thermoplastic resin, the material (nonwoven fabric or woven fabric) of the resin layer of the present embodiment is It is preferable to apply heat and pressure after superimposing a resin film as described in the first embodiment thereon. The melting point of the resin film is preferably the same as or lower than the base material of the member to be joined.

If it is desired to increase the adhesion, one surface of the member to be joined and one surface of the material of the resin layer are respectively activated, and then the activated surfaces are opposed to each other and laminated to be integrally molded. When two or more types of materials are combined for the resin layer, it is preferable to laminate and integrally mold each material after activating the surface to be contacted with the other material or the member to be joined.

The joining methods according to the first to fourth embodiments can be applied to join components of an aircraft. For example, the joining methods according to the first to fourth embodiments are suitable for joining the outer skin of the fuselage or wing of an aircraft and the stringers that reinforce it.

Note that the bonding methods according to the first to fourth embodiments may include a step of polishing the resin layer (polishing process) before performing the activation process.

Polishing can be performed by known mechanical means such as sanding and blasting. "Polishing" may include cutting the resin layer as well as polishing the surface of the resin layer.

Polishing is performed within the thickness of the resin layer. This makes it possible to control the increase in plate thickness caused by the formation of the resin layer.

By polishing the outer surface of part or all of the resin layer, the smoothness of the surfaces to be joined can be improved. In the polishing process, it is desirable to bring the surfaces to be joined closer to a mirror surface as far as possible.

The conditions for the polishing treatment are appropriately set according to the materials of the members to be joined.
For example, when the members to be joined contain hard and brittle reinforcing fibers such as SiC fibers, the surface of the members to be joined may be polished using diamond as an abrasive. Even if the member to be joined contains SiC fibers, if the outermost surface is a resin layer (a layer that does not contain SiC fibers) or if the amount of SiC fibers contained in the outermost layer is small, it should be polished by other methods. good too.

Moreover, in the bonding methods according to the first to fourth embodiments, the step of forming the resin layer may be performed in two steps.

First, a first resin layer is formed directly above a member to be joined based on any one of the first to fourth embodiments.

Next, a second resin layer is formed using a resin material directly above the first resin layer.

In forming the second resin layer, first, the outer surface of the first resin layer and one surface of the resin material are activated.

Next, the shape of the outer surface of the first resin layer and the shape of one surface of the resin material (imitation surface, which will be described later) are aligned, and the resin material is overlaid on the first resin layer.

Finally, the member to be joined provided with the first resin layer on which the resin material is superimposed is heated and pressurized. A second resin layer is thus formed.

The resin material is made of thermoplastic resin. The resin material has heat resistance equivalent to that of the base material of the first resin layer. The resin material may contain reinforcing fibers.

The thermoplastic resin used for the resin material is preferably made of the same material as the first resin layer.

As the resin material, two or more kinds of materials may be combined. For example, a material with a melting point lower than that of the base material is combined with the same material as the base material. In this case, the resin material should preferably have a three-layer structure (a structure in which two resin materials made of a material having a lower melting point than the base material sandwich a resin material made of the same material as the base material).

The resin material has a surface (imitation surface) that imitates the shape of the outer surface of the first resin layer. The simulated surface can be formed by measuring the outer surface of the first resin layer with a resin material or the like or by measuring the outer surface of the first resin layer with a three-dimensional scanner or the like, and by simulating based on the measurement results.

The formation of the second resin layer is effective when, for example, a gap occurs between the superposed surfaces when the member to be joined on which the first resin layer is formed is superimposed on another member to be joined.

<Appendix>
The joining method and the joined body described in each of the embodiments described above are grasped, for example, as follows.

The present disclosure is a joining method for joining members to be joined (1, 2, 11, 12) made of a fiber-reinforced thermoplastic whose base material is a thermoplastic resin. In the bonding method according to the present disclosure, a resin layer (3, 4, 13, 14) is formed on one surface of the member to be bonded, the outer surface of the resin layer is activated, and the activated resin layer is activated. The two members to be joined are superimposed with the outer surfaces facing each other, and the superposed members to be joined are heated and pressurized so that the temperature of the base material is maintained below the melting point.

A functional group containing oxygen is introduced into the activated surface. The activated surfaces are brought together and heated and pressed to chemically bond the functional groups on the opposing surfaces. Thereby, the two members to be joined are joined. Chemical bonds may be ester bonds, ether bonds, hydrogen bonds, van der Waals bonds, and the like.

Heating and pressing are carried out so that the temperature of the base material is maintained below the melting point, so that the base material does not melt. Therefore, since the plate thickness and shape do not change due to melting, it becomes easy to control the plate thickness and shape before and after joining. Since the base material does not melt, there is no concern that the reinforcing fibers will undulate.

By forming the resin layer, the surfaces of the members to be joined are smoothed. When the members to be joined are superimposed on each other with the smoothed surfaces as the surfaces to be joined, no gaps are formed in the joint surfaces, or the gaps formed in the joint surfaces can be reduced. As a result, the parts that cannot be joined can be reduced, and the distance between the surfaces to be joined can be shortened.

According to the bond potential curve, if the internuclear distance between oxygen-containing functional groups is more than 0.5 nm, the functional groups do not react with each other. Therefore, at the heating temperature during bonding, the distance between the surfaces to be bonded is preferably 0.5 nm or less.

If there is no gap or if the distance between the surfaces to be bonded is reduced, the chances of the functional groups on the facing surfaces meeting with the reaction partners increase. Therefore, the number of locations to be chemically bonded increases, and the bonding strength increases.

By smoothing the surface of the member to be joined, the quality of the joint can be stabilized.

In one aspect of the above disclosure, a resin film made of a thermoplastic resin is used as the material (10) of the resin layer, and the one surface of the member to be joined and the one surface of the resin film are activated, With one surface of the resin film that has undergone activation treatment facing one surface of the member to be joined, the resin film is superimposed on the member to be joined, and the member to be joined on which the resin film is superimposed is heated and heated. The resin layer can be formed by pressing.

The resin film easily conforms to the surface shape of the member to be joined. When the member to be joined on which the resin film is superimposed is heated and pressurized, the resin film conforms to the surface shape of the member to be joined. Thereby, one surface of the member to be joined can be smoothed.

The activation treatment improves the bonding strength between the resin film and the member to be bonded.

In one aspect of the above disclosure, the resin film having a melting point lower than that of the base material is used, and the member to be joined on which the resin film is stacked is heated so that the temperature of the base material is maintained below the melting point. The resin layer may be formed by pressing.

A resin film having a lower melting point than the base material becomes softer than the base material when heated and pressurized. As a result, it becomes easier to adapt to the surface shape of the member to be joined.

Since the heating and pressing are carried out so that the temperature of the base material is maintained below the melting point, the base material of the member to be joined does not melt during the formation of the resin layer. Therefore, since the plate thickness and shape of the base material do not change due to melting when the resin layer is formed, the plate thickness and shape can be easily managed. Since the base material does not melt, there is no concern that the reinforcing fibers will undulate.

In one aspect of the above disclosure, in the step of forming the resin layer, a nonwoven fabric may be inserted between the resin film and the member to be joined, and the heating and the pressing may be performed. In addition, the nonwoven fabric may be activated in order to increase the adhesion to the resin.

By inserting the non-woven fabric, the resin film softened by heating and pressurization is less likely to be absorbed by the base material. Thereby, a resin layer can be formed more reliably.

In one aspect of the above disclosure, the resin film having a higher melting point than the base material is used, and the member to be joined on which the resin film is superimposed is heated and pressed under the condition that the base material exceeds the glass transition temperature. The resin layer may be formed.

A resin film having a melting point higher than that of the base material does not melt when pressurized and heated, so it is easy to ensure the thickness of the resin layer.

In one aspect of the above disclosure, a resin material made of a thermoplastic resin having an imitation surface following the shape of one surface of the member to be joined and another smooth surface is used as a material of the resin layer, and the member to be joined is made of a resin material. The one surface of the joining member and the imitation surface of the resin material are activated, and the imitation surface of the resin material that has been activated is directed to one surface of the member to be joined, and the resin material is applied to the surface of the member to be joined. The resin layer may be formed by overlapping the member to be joined and heating and pressurizing the member to be joined on which the resin material is superimposed.

By using a resin material having a surface that follows the shape of one surface of the member to be joined, the resin material can be brought into close contact with the member to be joined. Thereby, the bonding strength between the resin material and the member to be bonded can be increased.

In one aspect of the above disclosure, the first thermoplastic prepreg (9) is used as the material of the member to be joined, and the first thermoplastic prepreg located on the outermost surface is coated with the The resin layer may be formed by laminating materials (10) for the resin layer and integrally molding them.

By integrally molding the material of the resin layer and the first thermoplastic prepreg, the resin layer is firmly bonded to the member to be bonded.

In one aspect of the above disclosure, the material for the resin layer is at least a thermoplastic resin film, a second thermoplastic prepreg (6) having a higher resin content than the first thermoplastic prepreg, a nonwoven fabric, and a woven fabric. Using one, the non-woven fabric may be made of inorganic fibers or organic fibers, and the woven fabric may be made of inorganic fibers or organic fibers.

By using the above materials, it is possible to increase the bonding strength between the members to be bonded. When the resin film or the second thermoplastic prepreg is used as the material of the resin layer, the surface to be joined can be smoothed.

When the second thermoplastic prepreg is used as the material for the resin layer, by making the resin content of the second thermoplastic prepreg higher than that of the first thermoplastic prepreg, the outer surface of the resin layer is made to be less than the one surface of the member to be joined. can also be smoothed.

In one aspect of the above disclosure, one surface of the material for the resin layer is activated, and the activated one surface of the material for the resin layer is directed toward one surface of the first thermoplastic prepreg, and the resin A layer of material may be laminated to the first thermoplastic prepreg.

In one aspect of the above disclosure, one surface of the first thermoplastic prepreg may be activated before laminating the material of the resin layer.

The activation treatment improves the adhesion between the resin layer and the member to be joined.

In one aspect of the above disclosure, as the material of the resin layer, a nonwoven fabric made of inorganic fibers or organic fibers, or a woven fabric made of inorganic fibers or organic fibers is used, and the material of the resin layer is the member to be joined. The resin layer may be formed by heating and pressurizing the member to be joined on which the material of the resin layer is superimposed so that the temperature of the base material is equal to or higher than the melting point of the base material.

By melting the base material, the melted base material soaks into the material of the resin layer to form the resin layer. By forming a resin layer on the surfaces to be joined, the bonding strength between the members to be joined can be increased.

In one aspect of the above disclosure, one surface of the member to be joined and one surface of the material of the resin layer are subjected to an activation treatment, and the one surface of the material of the resin layer that has been subjected to the activation treatment is applied to the member to be joined. The material of the resin layer may be overlaid on the member to be joined so as to face one surface.

The activation treatment improves the adhesion between the resin layer and the member to be joined.

In one aspect of the above disclosure, the step of forming the resin layer includes forming a first resin layer on one surface of the member to be joined, and forming a second resin layer on the outer surface of the first resin layer. and using a thermoplastic resin material having one surface that follows the shape of the outer surface of the first resin layer as the material of the second resin layer, and the outer surface of the first resin layer. and one surface of the resin material is activated, and the shape of the outer surface of the first resin layer and the shape of the one surface of the resin material are aligned so that the shape of the outer surface of the resin material matches the shape of the one surface of the resin material. The second resin layer may be formed by heating and pressurizing the first resin layer and the member to be joined on which the resin material is superimposed.

By using a resin material having a surface that follows the shape of the outer surface of the first resin layer, the resin material can adhere to the first resin layer. By forming the second resin layer, it is possible to more reliably reduce the gap between the surfaces to be joined.

In one aspect of the above disclosure, the outer surface of the resin layer may be polished after forming the resin layer and before performing the activation treatment.

By polishing, it is possible to control the increase in plate thickness caused by the formation of the resin layer. In addition, the polished surface of the resin layer becomes smoother. By using the smoothed surface as the surface to be bonded, the bonding strength between the members to be bonded is improved.

A joined body (5) according to the present disclosure comprises a first joined member (1) made of fiber-reinforced thermoplastic, a second joined member (2) made of fiber-reinforced thermoplastic, and the first joined member (1) made of fiber-reinforced thermoplastic. A first thermoplastic resin layer (3) covering one surface of a member and chemically bonded to the first member to be joined, and a first resin layer (3) covering one surface of the second member to be joined and covering the second member to be joined A second resin layer (4) made of a thermoplastic resin chemically bonded to the member, wherein the first resin layer and the second resin layer are adjacent and chemically bonded.

1, 2, 11, 12, 21, 22 members to be joined 3, 4, 13, 14 resin layer 5 joined body 6 second thermoplastic prepreg 7 thermoplastic resin 8 reinforcing fiber 9 first thermoplastic prepreg 10 resin layer material

Claims (15)

A joining method for joining members to be joined, wherein the members to be joined are made of a fiber-reinforced thermoplastic whose base material is a thermoplastic resin,
forming a resin layer on one surface of the member to be joined;
activating the outer surface of the resin layer to introduce active functional groups capable of causing chemical bonding ;
The two members to be joined are superimposed with the outer surfaces of the resin layer that have been subjected to the activation treatment facing each other,
A joining method in which the members to be joined are heated and pressurized so that the temperature of the base material is maintained below the melting point. Using a resin film made of thermoplastic resin as a material for the resin layer,
activating the one surface of the member to be joined and the one surface of the resin film;
one surface of the resin film that has undergone activation treatment faces one surface of the member to be joined, and the resin film is superimposed on the member to be joined;
2. The joining method according to claim 1, wherein the member to be joined on which the resin film is laminated is heated and pressurized to form the resin layer. Using the resin film having a lower melting point than the base material,
3. The joining method according to claim 2, wherein the member to be joined on which the resin film is laminated is heated and pressed to form the resin layer so that the temperature of the base material is maintained below the melting point. 4. The bonding method according to claim 3, wherein in the step of forming the resin layer, a non-woven fabric is inserted between the resin film and the member to be bonded, and the heating and pressing are performed. Using the resin film having a higher melting point than the base material,
3. The joining method according to claim 2, wherein the member to be joined on which the resin film is laminated is heated and pressed under the condition that the base material exceeds the glass transition temperature to form the resin layer. using a resin material made of a thermoplastic resin as a material for the resin layer, the resin material having an imitation surface following the shape of one surface of the member to be joined and another smooth surface;
activating the one surface of the member to be joined and the simulated surface of the resin material;
laminating the resin material on the member to be joined, with the simulated surface of the resin material that has undergone activation treatment facing one surface of the member to be joined;
2. The joining method according to claim 1, wherein the members to be joined on which the resin material is superimposed are heated and pressed to form the resin layer. Using a first thermoplastic prepreg as a material for the member to be joined,
2. The bonding according to claim 1, wherein the resin layer is formed by laminating the material of the resin layer on the first thermoplastic prepreg positioned on the outermost surface and integrally molding the material when molding the member to be bonded. Method. As a material for the resin layer, at least one of a thermoplastic resin film, a second thermoplastic prepreg having a higher resin content than the first thermoplastic prepreg, a nonwoven fabric, and a woven fabric is used,
The nonwoven fabric is made of inorganic fibers or organic fibers,
The joining method according to claim 7, wherein the fabric is made of inorganic fibers or organic fibers. activating one surface of the material of the resin layer,
One surface of the material for the resin layer that has been activated is directed to one surface of the first thermoplastic prepreg, and the material for the resin layer is laminated on the first thermoplastic prepreg. Joining method as described. 10. The joining method according to claim 9, wherein one surface of the first thermoplastic prepreg is subjected to an activation treatment before laminating the material of the resin layer. As the material for the resin layer, nonwoven fabric made of inorganic or organic fibers, or woven fabric made of inorganic or organic fibers is used,
superimposing the material of the resin layer on one surface of the member to be joined;
2. The joining method according to claim 1, wherein the member to be joined on which the material of the resin layer is laminated is heated and pressed to form the resin layer so that the temperature of the base material is equal to or higher than the melting point. activating one surface of the member to be joined and one surface of the material of the resin layer;
12. The joining method according to claim 11, wherein one surface of the material of the resin layer that has been activated is directed toward one surface of the member to be joined, and the material of the resin layer is superimposed on the member to be joined. The step of forming the resin layer includes the step of forming a first resin layer on one surface of the member to be joined, and the step of forming a second resin layer on the outer surface of the first resin layer,
As a material for the second resin layer, using a thermoplastic resin material having one surface that follows the shape of the outer surface of the first resin layer,
activating the outer surface of the first resin layer and one surface of the resin material;
aligning the shape of the outer surface of the first resin layer and the shape of one surface of the resin material so as to match, and superimposing the resin material on the first resin layer;
The joining method according to any one of claims 2 to 12, wherein the second resin layer is formed by heating and pressurizing the first resin layer and the member to be joined, on which the resin material is superimposed. 14. The joining method according to any one of claims 1 to 13, wherein the outer surface of the resin layer is polished after forming the resin layer and before performing the activation treatment. A joined body in which the members to be joined are made of a fiber-reinforced thermoplastic whose base material is a thermoplastic resin, and the members to be joined are joined to each other,
A resin layer is provided on one surface of the member to be joined,
An active functional group capable of causing a chemical bond is introduced to the outer surface of the resin layer by an activation treatment,
The two members to be joined are arranged so that the outer surfaces of the resin layers subjected to the activation treatment face each other and overlap each other,
A joined body obtained by heating and pressurizing the members to be joined in a superimposed state so that the temperature of the base material is maintained below the melting point.

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