JP2023139412A - Fiber-reinforced resin joined structure - Google Patents

Abstract

To provide a joined structure of a fiber-reinforced resin which exhibits good joining characteristics, and can be executed under a simpler process condition than a joining process when the joined structure is manufactured.SOLUTION: There is provided a fiber-reinforced resin joined structure in which an adherend 1 and an adherend 2 that are formed of fiber-reinforced resins having uneven shapes thereon are integrated with each other through a joining component 1, where the joining component 1 is made to fill the adherends within a range of 30-95% of a depth D1 of the uneven shape existing on the surface of the adherend 1.SELECTED DRAWING: Figure 2

Description

The present invention relates to a fiber-reinforced resin bonded structure, and relates to a fiber-reinforced resin bonded structure that can maintain a good bonded state between the fiber-reinforced resin and another adherend. As long as the conditions are within a feasible range, it is also possible to reduce the bonding process load such as bonding temperature, bonding pressure, and bonding time during bonding.

In order for FRP bonded structures, which are made by bonding fiber reinforced resin (FRP) and other adherends, to effectively exhibit their functions, it is necessary to provide an uneven shape to the FRP surface in order to maintain a good bonding state. A method of increasing the contact area between the bonding components that bond FRP and other adherends, or forming a so-called anchor structure between the two to prevent the bonding components from being easily peeled off. is common. However, it is not easy to spread the bonding component to every corner of the uneven shape of the FRP surface, and the load of the bonding process becomes extremely large.

On the other hand, Patent Document 1 describes a method in which a thermoplastic resin, which is a bonding component, is impregnated when FRP is cured and molded, thereby spreading the bonding component to every corner of the uneven shape formed during molding. has been done. However, this method cannot be applied to FRP molded without a bonding component, and in the first place cannot be implemented when bonding is performed using a bonding component after molding.

Further, Patent Document 2 describes a configuration in which a fine uneven shape is imparted to the FRP surface and other members are bonded thereto using a bonding component, but the degree of filling of the bonding component into the fine uneven shape is not mentioned. However, the description is based on the premise that all the fine irregularities are filled, and in some cases, the bonding process load may become large.

Patent Document 3 describes a joining structure in which only the matrix resin of FRP is removed to expose the reinforcing fibers, and the reinforcing fibers are filled and joined with a second polymeric material as a joining component. This method requires pre-treating the FRP surface to expose only the reinforcing fibers and then filling them with the bonding component, but there is no mention of the degree to which the exposed reinforcing fibers are filled with the bonding component. Bonding is described on the premise that all exposed reinforcing fibers are filled, and in some cases, the bonding process load may become large.

International publication WO2004/060658 JP2017-52127A Japanese Patent Application Publication No. 2011-79289

Therefore, an object of the present invention is to provide an FRP bonded structure that can maintain a good bonded state between FRP and other adherends, focusing on the problems in the prior art as described above. As long as the bonded state of the bonded structure can be realized, it is also possible to reduce the bonding process load such as the bonding temperature, bonding pressure, and bonding time during bonding.

In order to solve the above problems, the present invention employs the following configuration.
(1) A bonded structure in which an adherend 1 and an adherend 2 made of fiber-reinforced resin having an uneven surface are integrated via a bonding component 1, and the bonding component 1 A fiber-reinforced resin bonded structure that is filled to a depth of 30 to 95% of the depth D1 of the uneven shape existing on the surface.
(2) The fiber-reinforced resin bonded structure according to (1), wherein the bonding component 1 is filled in a range of 50 to 80% of the depth D1 of the uneven shape existing on the surface of the adherend 1.
(3) The adherend 2 has an uneven shape on its surface, and the bonding component 1 is filled in a range of 30 to 95% of the depth D2 of the uneven shape existing on the surface of the adherend 2, (1 ) or the fiber-reinforced resin bonded structure according to (2).
(4) The fiber-reinforced resin bonded structure according to any one of (1) to (3), wherein the adherend 1 and/or the adherend 2 are made of carbon fiber-reinforced resin.
(5) The fiber-reinforced resin bonded structure according to any one of (1) to (4), wherein bonding component 1 is any one of epoxy resin, urethane resin, acrylic resin, polyamide resin, and polyolefin resin.
(6) The fiber-reinforced resin bonded structure according to any one of (1) to (5), wherein the bonding component 1 has a tensile strength of 10 to 200 MPa.

As described above, the fiber-reinforced resin bonded structure of the present invention exhibits good bonding properties and can be manufactured using simpler process conditions. can be provided.

It is a schematic sectional view showing an example of the uneven shape of the fiber reinforced resin surface. FIG. 2 is a schematic cross-sectional view showing an example of an uneven shape on the surface of a fiber-reinforced resin filled with bonding component 1. FIG. FIG. 2 is a schematic perspective view showing a bonded structure (bonded test piece). FIG. 2 is a schematic perspective view showing an adherend subjected to laser processing. FIG. 2 is a schematic perspective view showing a sandblasted adherend.

The present invention will be described in more detail below along with embodiments.

The FRP bonded structure according to the present invention is a bonded structure in which an adherend 1 made of fiber-reinforced resin having an uneven surface and an adherend 2 are integrated via a bonding component 1. 1 is a fiber-reinforced resin bonded structure that is filled in a range of 30 to 95% of the depth D1 of the uneven shape existing on the surface of the adherend 1, and the bonding component 1 is filled with the depth D1 of the unevenness. Although it is not completely filled, it is characterized by being filled to a certain degree to ensure good bonding. Here, a good bond is ideally a state in which, when bonding strength is evaluated, the bonding components exhibit cohesive failure over the entire bonding surface, resulting in stable and high bonding strength. Conversely, if the bonding component causes interfacial peeling at the interface with the adherend, the variation in bonding strength will increase and the bonding strength will also tend to decrease. In addition, there may be a case where cohesive failure of bonding components and interfacial peeling coexist, and in that case, the higher the rate of cohesive failure, the more stable and good the bond can be judged to be.

Specifically, as shown in FIGS. 1 and 2, in the cross-sectional schematic diagram of the FRP part of the FRP bonded structure, the surface F of the FRP is provided with an uneven shape, and the bonding component 1 is filled in this uneven shape. A good FRP bonded structure can be obtained by bonding FRP and adherend 2. At this time, it is not necessary that the bonding component 1 is filled over the entire region of the uneven shape of the FRP surface, and good bonding can be maintained as long as the bonding component 1 is filled to the extent that cohesive failure occurs. In order to fill the entire area of the uneven shape with bonding component 1, it is necessary to increase the load such as bonding temperature, bonding pressure, bonding time, etc. in the bonding process, and this is from the perspective of reducing power consumption and energy consumption in the bonding process. From now on, I want to keep the load as small as possible.

Here, the depth D1 of the uneven shape on the FRP surface and the filling of the bonding component 1 into the uneven shape D1, which are important parameters of the present invention, will be explained. The uneven shape of the FRP surface of the present invention refers to the uneven shape imparted to the FRP surface by a surface treatment method such as sandblasting, laser processing, flame treatment, chemical treatment, electrolytic treatment, plasma treatment, surface roughening with sandpaper, etc. It indicates an uneven shape. In addition, the depth D1 of the uneven shape is defined as the depth D1 formed between two points AB at the shallowest position of the uneven shape on the FRP surface within the range of a specific length L shown by 2 in the FRP cross section shown in FIG. Among the distances from the reference surface 1 of the FRP to the uneven surface 3 formed with uneven shapes, the maximum to fifth depths Dmax1 to Dmax5 and the minimum to fifth depths Dmin1 to Dmin5. The average depth of the 10 locations is defined as the depth D1 of the uneven shape. Furthermore, regarding the filling of the bonding component 1 into the depth D1 of the uneven shape, the distance Dmax1p to Dmax5p filled with the bonding component 1 is determined from Dmax1 to Dmax5 within the range of the specific length L indicated by 2 in FIG. The ratio is defined as the average value of the values expressed as a percentage. For example, if the bonding component 1 fills all of the depths Dmax1 to Dmax5 of the uneven shape to half, the filling becomes 50%. Here, the specific length L is selected in the range of 0.1 mm to 10 mm, excluding areas where the FRP has been given extreme irregularities such as bending, in order to fully reflect the characteristics of FRP in the evaluation results. That is appropriate. Further, the evaluation of the depth D1 of the uneven shape and the evaluation of the filling of the bonding component 1 may be performed at the same part of the FRP or at different parts.

The depth D1 of the uneven shape is preferably 1 μm or more from the viewpoint of achieving good bonding. Further, from the viewpoint of not reducing the strength of the FRP itself by imparting an excessive uneven shape to the FRP, and from the viewpoint of reducing the load when imparting the uneven shape, the thickness is preferably 5000 μm or less. A more preferable range is 10 μm to 3000 μm, and even more preferably 50 to 1000 μm.

In addition, it is important that the filling of the bonding component 1 into the depth D1 of the uneven shape is 30% or more from the perspective of achieving good bonding, and from the perspective of reducing the load of the bonding process, it is important to fill the bonding component 1 to the depth D1. It is important that it be smaller than 100%, specifically 95% or less. The preferred range is 40 to 90%, more preferably 50 to 80%.

The adherend 2 of the present invention is not particularly limited in its constituent materials, and includes metal materials such as steel and aluminum, various resin materials, films, and FRP similar to the adherend 1, which have the characteristics required for FRP bonded structures. Can be combined appropriately depending on the situation. From the viewpoint of enhancing the bonding between the adherends 1 and 2 in the FRP bonded structure, the surface of the adherend 2 as well as the adherend 1 has an uneven shape with a depth D2 of 1 to 5000 μm. It is preferable. A more preferable range is 10 μm to 3000 μm, and even more preferably 50 to 1000 μm.

Further, from the viewpoint of achieving good bonding and reducing the load of the bonding process, the filling of the bonding component 1 into the depth D2 of the uneven shape is preferably 30 to 95%, more preferably 40 to 90%. %, more preferably 50 to 80%.

Regarding the method of measuring the depth of the uneven shape on the FRP surface, for example, by observing the cross section of FRP with a microscope, the maximum to 5th depths Dmax1 to Dmax5 and the minimum to 5th depths shown in Fig. 1 are measured. Examples include a method of measuring Dmax1 to Dmax5 by image analysis. Regarding the method of measuring the filling of the bonding component 1 into the depth D1 of the uneven shape, from the microscopic observation of the cross section of the FRP bonded structure after being filled with the bonding component 1, as shown in FIG. Examples include a method of measuring the distances Dmax1p to Dmax5p by image analysis. The adherend 2 can also be measured in the same manner.

Since at least one of the adherends 1 and 2 made of FRP of the present invention is made of carbon fiber reinforced resin, the FRP bonded structure can be made lighter and superior in strength and rigidity. preferable. The strength and elastic modulus of the carbon fibers used are selected depending on the purpose and required characteristics. Furthermore, the matrix resin used for the carbon fiber reinforced resin may be either a thermosetting resin or a thermoplastic resin. As the thermosetting resin, epoxy resin, vinyl ester resin, phenol resin, etc. can be used. As the thermoplastic resin, polypropylene resin, polyamide resin, PPS resin, PEEK resin, etc. can be used.

As the bonding component 1 of the present invention, various bonding resins can be used, but among them, epoxy resin is thermosetting, forms a three-dimensional crosslinked structure, has excellent strength and heat resistance, and has high durability. preferred. Further, urethane resin is also preferable from the viewpoint of enabling a bonded structure that has high elongation at break and is resistant to deformation. Furthermore, acrylic resin has a wide variety of chemical structures and is preferred as a bonding component because it is a resin whose performance balance can be easily controlled. Furthermore, thermoplastic resins such as polyamide resins and polypropylene resins can be bonded by applying heat to melt them and then cooling and solidifying them, making it easy to shorten the bonding cycle and bonding by heat. It is also preferable from the viewpoint of having recyclability that allows the structure to be dismantled.

Further, the bonding component 1 of the present invention preferably has a tensile strength (ISO527 standard) of 10 to 200 MPa from the viewpoint of developing stronger bonding strength. More preferably 15 to 200 MPa, still more preferably 20 to 200 MPa.

Applications of FRP bonded structure The FRP bonded structure of the present invention can be used in various applications such as aircraft parts, automobile parts, mobility applications such as drones, electrical/electronic parts, building materials, various containers, daily necessities, household goods, and sanitary products. can do. Among these, it is preferable to use FRP in structural parts, exterior parts, interior parts, etc. in mobility applications.

Examples will be shown below to further specifically explain the present invention, but the following examples do not limit the present invention in any way, and changes within the scope of the gist of the present invention are within the scope of the technology of the present invention. range. The characteristics of the present invention were evaluated according to the following method.

(1) Depth D1 of unevenness of adherend 1
A cross section of the adherend 1 is wet-polished and observed under a microscope, and within the range where the specific length L shown by 2 is 5 mm in the cross section (schematic diagram shown in FIG. 1), the unevenness of the FRP surface is determined. Among the distances from the FRP reference surface 1 formed between the two points AB at the shallowest position to the uneven surface 3 formed in an uneven shape, the depths Dmax1 to Dmax5 from the maximum to the fifth, and from the minimum to The average depth of the 10 locations from the fifth depth Dmin1 to Dmin5 was defined as the depth D1 of the uneven shape. Note that the depth D2 of the unevenness of the adherend 2 was also evaluated in the same manner.

(2) Filling of bonding component 1 (%)
Wet-polish the cross section of the FRP bonded structure and observe it with a microscope, and in the cross section (schematic diagram shown in FIG. 2) where the adherend 1 is filled with the bonding component 1, the specific length L indicated by 2 is set to 5 mm. Within the range Dmax1 to Dmax5, the ratio to the distance Dmax1p to Dmax5p filled with bonding component 1 was evaluated as the average value expressed as a percentage. The filling (%) of bonding component 1 into adherend 2 was also evaluated in the same manner.

(3) Bonding strength of FRP bonded structure A bonded test piece (Fig. 3) consisting of adherend 1 and adherend 2 bonded with bonding component 1 was subjected to a tensile shear test at a speed of 5 mm/min using a tensile testing machine. was carried out with n=5, and the average value was taken as the bonding strength. Bonding strength of 20 MPa or more was graded A, bonding strength of 10 MPa or more but less than 20 MPa was graded B, and bonding strength of less than 10 MPa was graded C.

(4) Bonding strength variation of FRP bonded structure In the bonding strength evaluation, the difference between the maximum value and the minimum value of the evaluation of n = 5 is defined as the bonding strength variation, and bonding strength variation of less than 5 MPa is A, and 5 MPa or more and less than 8 MPa. B, 8 MPa or higher was rated C. A, B, and C are ranked in descending order of bonding strength variation.

(5) Fracture form of FRP bonded structure Visually observe the fracture surface of the FRP bonded structure after evaluating the bond strength, and A indicates cohesive failure of bond component 1 over the entire surface of the bond. B is the case where the area of cohesive failure is larger than the area of interfacial peeling; C is the case where the area of cohesive failure of bonding component 1 is smaller than the area of interfacial peeling; and C is the case where interfacial peeling of bonding component 1 occurs over the entire surface of the joint. It was set as D. A, B, C, and D are listed in descending order of bonding state.

[Reference Example 1] Manufacture of carbon fiber reinforced resin (CFRP1) Unidirectional prepregs made of carbon fiber "Torayca" (registered trademark) T700S (12K) manufactured by Toray Industries, Inc. are laminated in the same direction and cured to a thickness of 1.5 mm. CFRP1 was obtained. Before joining, it was degreased with acetone.

[Reference Example 2] Production of glass fiber reinforced resin (GFRP1) Unidirectional prepregs made of glass fiber RS240PU-537 manufactured by Nittobo Co., Ltd. were laminated in the same direction to obtain GFRP1 which was cured to a thickness of 1.5 mm. Before joining, it was degreased with acetone.

[Reference example 3] Aluminum material 1
The surface of aluminum A5052 (thickness 1.5 mm) was degreased with acetone before use.

[Reference Example 4] Bonding component 1
Epoxy 1:3M panel bond 8115 was used.
Epoxy 2: ThreeBond 3951D manufactured by ThreeBond was used.
Polyamide: CM4000 manufactured by Toray Industries was press-molded and used as a 0.3 mm thick sheet.
Modified PP (polypropylene): QF500 manufactured by Mitsui Chemicals was press-molded and used as a 0.3 mm thick sheet.

Example 1
The CFRP1 fabricated in Reference Example 1 was used for adherend 1, and the CFRP1 fabricated in Reference Example 1 was used for adherend 2, each having a width of 25 mm and a length of 150 mm (the fiber orientation direction was the length direction). ), and as shown in FIG. 4, the surface of the CFRP 1 was laser-processed to form holes with a diameter of 100 μm and a depth of 20 μm on grid intersections spaced at 200 μm intervals. A bonded structure (bonded test piece) as shown in FIG. 3 was prepared by using bonding component 1 (epoxy 1) described in Reference Example 4 between the surfaces of this CFRP 1 where holes were formed. The area of the joint portion is 25 mm x 12.5 mm. The bonding process is as described in Table 1. Table 1 shows the filling of the bonding component 1 and the bonding strength evaluation of the obtained bonding test piece.

Examples 2 to 12, Comparative Examples 2 and 3
As shown in Tables 1 and 2, the surface of adherend 1, adherend 2, and adherend used is subjected to laser processing or sandblasting as shown in Figure 4 or Figure 5 to give a surface uneven shape. A bonded structure (bonded test piece) was prepared and evaluated in the same manner as in Example 1, except that the bonding component 1 and the bonding process conditions were changed. The evaluation results are shown in Tables 1 and 2. In addition, the bonding process when the bonding component 1 is polyamide is, for example, in Example 7, processing at 160° C. and a pressure of 0.1 MPa for 0.02 hours, and then processing at 25° C. and a pressure of 0.1 MPa for 0.5 hours. are doing. In the case where bonding component 1 was modified PP (Example 11), the bonding process was performed at 170°C and a pressure of 0.2 MPa for 0.02 hours, and then at 25°C and a pressure of 0.2 MPa for 0.5 hours. ing.

Comparative example 1
A bonded structure (bonded test piece) was produced and evaluated in the same manner as in Example 7, except that CFRP1 was not subjected to surface treatment. The evaluation results are shown in Table 2.

Example 1 is a bonded structure in which laser-processed CFRPs 1 are bonded together using epoxy 1, and a good bonded state is obtained.

In Example 2, the depths D1 and D2 of the unevenness were made deeper than in Example 1, resulting in better bonding strength.

In Example 3, the surface treatment of CFRP1 was changed to sandblasting, but a good bonding state was obtained.

In Example 4, the adherend 2 in Example 3 was changed to aluminum material 1, but a good bonding state was obtained.

In Example 5, the adherend 1 in Example 4 was changed to GFRP1, but a good bonding state was obtained.

In Example 6, the load in the bonding process of Example 4 was increased, specifically, the bonding temperature was changed from 50°C to 80°C and the bonding pressure was changed from 0.01 MPa to 0.05 MPa. The filling of component 1 increased from 70% to 95%, but the bonding conditions were equally good in both cases.

In Example 7, the bonding component 1 of Example 4 was changed to polyamide, but a good bonding state was obtained. Since polyamide, a thermoplastic resin, was used as the bonding component 1, the bonding time could be significantly shortened from 3 hours to about 30 minutes, although the bonding temperature and bonding pressure had to be increased.

In Example 8, the depths D1 and D2 of the unevenness were made shallower than in Example 7, and although the bonding strength was slightly lower, good results were obtained.

In Example 9, the load in the bonding process of Example 7 was increased, specifically, the bonding temperature was increased from 160°C to 170°C, the bonding pressure was increased from 0.1 MPa to 0.2 MPa, and the bonding time was changed from 0.52 hours. The time was changed to 0.54 hours, and as a result, the filling of bonding component 1 increased from 75 to 80% to 95%, but the bonding conditions were equally good in both cases.

In Example 10, the load in the bonding process of Example 7 was reduced, specifically by changing the bonding pressure from 0.1 MPa to 0.01 MPa and the bonding time from 0.52 hours to 0.51 hours. The filling of bonding component 1 became smaller, and the bonding condition was good, but slightly deteriorated accordingly.

In Example 11, bonding component 1 of Example 7 was changed to modified PP, but since modified PP has lower polarity than polyamide, the bondability with CFRP1 tends to be lower than that of polyamide. Even though the tensile strength and filling of bonding component 1 were at the same level, the bonding strength was slightly lower.

In Example 12, bonding component 1 in Example 3 was changed to epoxy 2, but since epoxy 2 has a tensile strength of 8 MPa, which is lower than the 21 MPa of epoxy 1, the bonding strength was lower. Ta. However, the variation in bonding strength is small, and the fracture mode is cohesive failure of bonding component 1, and although the bonding strength is low, the bonding properties are stable and good.

On the other hand, in Comparative Example 1, no irregularities were formed on the surface of the adherend 1 and the bonding component 1 was not filled, so that the form of failure was interfacial peeling and the bonding state was poor.

In Comparative Example 2, in order to make the filling of bonding component 1 100%, it was necessary to increase the load of the bonding process, and compared to Example 7, the bonding temperature was increased from 160°C to 200°C, and the bonding pressure was 0. It was necessary to change the conditions from .1 MPa to 1 MPa and the bonding time from 0.52 hours to 0.7 hours, but there was no major difference in bonding characteristics, and the excessive conditions caused excessive filling. It can be determined that the condition is

In Comparative Example 3, the filling of bonding component 1 was as small as 20%, and the fracture form was a bonded state with low bonding strength in which interfacial peeling was often observed.

1. Reference surface 2 of adherend 1 (fiber reinforced resin). Specific length L
3. Uneven surface 4. Bonding component 1
5. FRP
6. Adherent 1
7. Adherent 2
a. 150mm
b. 25mm
c. 12.5mm

Claims (6)

A bonded structure in which an adherend 1 and an adherend 2 made of fiber-reinforced resin having an uneven surface are integrated via a bonding component 1, where the bonding component 1 is present on the surface of the adherend 1. A fiber-reinforced resin bonded structure in which the depth D1 of the uneven shape is filled in a range of 30 to 95%. The fiber-reinforced resin bonded structure according to claim 1, wherein the bonding component 1 is filled in a range of 50 to 80% of the depth D1 of the uneven shape existing on the surface of the adherend 1. Claim 1 or 2, wherein the adherend 2 has an uneven shape on its surface, and the bonding component 1 is filled in a range of 30 to 95% of the depth D2 of the uneven shape existing on the surface of the adherend 2. The fiber-reinforced resin bonded structure described in . The fiber-reinforced resin bonded structure according to any one of claims 1 to 3, wherein the adherend 1 and/or the adherend 2 are made of carbon fiber-reinforced resin. The fiber-reinforced resin bonded structure according to any one of claims 1 to 4, wherein bonding component 1 is any one of epoxy resin, urethane resin, acrylic resin, polyamide resin, and polyolefin resin. The fiber-reinforced resin bonded structure according to any one of claims 1 to 5, wherein the tensile strength of bonding component 1 is 10 to 200 MPa.