JP2021142757A - Hybrid structural member of fiber-reinforced resin molded article and metal - Google Patents

Abstract

To provide a hybrid structural member of a fiber-reinforced resin molding and metal having excellent light weight property and high impact resistance.SOLUTION: The hybrid structural member of a fiber-reinforced resin molding and metal is provided in which a fiber-reinforced resin molding (1) and metal are integrated with each other through an adhesive (2). The fiber-reinforced resin molding (1) is a fiber-reinforced resin molding containing: a fiber bundle in which a plurality of reinforcing fibers are bundled; and a matrix resin, wherein a coefficient of variation of a reinforcement fiber content per unit section of 0.1 mm square in a thickness direction-cross section of the fiber-reinforced resin molding is 40% or less. The adhesive (2) has a coefficient of elasticity of 2 GPa or less.SELECTED DRAWING: None

Description

The present invention relates to a hybrid structural member made of a fiber reinforced resin molded product and a metal, and particularly to a dissimilar material structural member that can be used in a vehicle.

The hybrid structural member of the fiber reinforced resin molded product and the metal can exhibit both the excellent light weight and high mechanical properties of the fiber reinforced resin molded product and the impact resistance of the metal, and the fiber reinforced resin can be used. As a method of integrating a molded product and a metal, a method of bonding and integrating a fiber reinforced resin molded product and a metal or mechanically joining them with a bolt or the like is known.

However, the hybrid structural member of the fiber-reinforced resin molded product and the metal, which is simply bonded to the fiber-reinforced resin molded product, has a weak adhesive strength and may not exhibit predetermined characteristics.

Structures with improved adhesiveness between fiber reinforced plastic molded products and metals (for example, Patent Document 1) and structures with improved adhesiveness by increasing the toughness of the adhesive itself (for example, Patent Documents 2 and 3) Although it has been proposed, sufficient adhesive strength has not been obtained due to peeling at the interface between the fiber reinforced resin molded product and the adhesive layer or the base material of the fiber reinforced resin molded product being destroyed.

Japanese Unexamined Patent Publication No. 2006-297927 Japanese Unexamined Patent Publication No. 58-189277 Japanese Unexamined Patent Publication No. 2004-263104

The present invention is intended to solve the above-mentioned problems associated with the prior art, and improves the adhesiveness between the fiber reinforced plastic molded product and the metal to provide excellent lightness and high impact resistance. An object of the present invention is to provide a hybrid structural member of a fiber-reinforced resin molded product and a metal.

As a result of diligent research to solve the above problems, the present inventor has achieved excellent lightness and advancedness by using a fiber reinforced resin molded product and a metal having improved fiber dispersibility in the fiber reinforced resin molded product. It has been found that it is possible to provide a hybrid structural member of a fiber reinforced resin molded product and a metal having excellent impact resistance and the like. That is, the gist of the present invention lies in the following [1] to [8].

[1] A hybrid structural member of a fiber-reinforced resin molded body and a metal in which the following fiber-reinforced resin molded body (1) and a metal are integrated via an adhesive (2).
<Fiber reinforced plastic molded body (1)>
A fiber-reinforced resin molded body containing a fiber bundle in which a plurality of reinforcing fibers are bundled and a matrix resin, and the reinforcing fibers per unit section of 0.1 mm square on the cut surface in the thickness direction of the fiber-reinforced resin molded body. The fluctuation coefficient of the content rate is 40% or less.
<Adhesive (2)>
An adhesive having an elastic modulus of 2 GPa or less.
[2] The hybrid structural member according to the above [1], wherein the tensile adhesive shear strength of the hybrid structural member at 23 ° C. is 14 MPa or more.
[3] The average fiber length of the reinforcing fibers in the fiber-reinforced resin molded body is 5 to 100 mm.
The hybrid structural member according to the above [1] or [2].
[4] The hybrid structural member according to any one of [1] to [3] above, wherein the coefficient of variation of the reinforcing fiber content per unit section of 0.1 mm square is 10% or less.
[5] The hybrid structural member according to any one of the above [1] to [4], wherein the reinforcing fiber is a carbon fiber.
[6] The hybrid structural member according to any one of [1] to [5] above, wherein the thickness of the adhesive is 0.1 or more and 4 mm or less.
[7] The hybrid structural member according to any one of [1] to [5] above, wherein the thickness of the adhesive is 0.1 or more and 1 mm or less.
[8] The hybrid structural member according to any one of the above [1] to [7], wherein the adhesive is an epoxy adhesive.

According to the present invention, it is possible to provide a hybrid structural member of a fiber-reinforced resin molded body and a metal having excellent lightness and high impact resistance.

In the hybrid structural member of the fiber-reinforced resin molded body and the metal of the present invention, the following fiber-reinforced resin molded body (1) and the metal are integrated via an adhesive (2).
<Fiber reinforced plastic molded body (1)>
A fiber-reinforced resin molded body containing a fiber bundle in which a plurality of reinforcing fibers are bundled and a matrix resin, and the reinforcing fibers per unit section of 0.1 mm square on the cut surface in the thickness direction of the fiber-reinforced resin molded body. The fluctuation coefficient of the content rate is 40% or less.
<Adhesive (2)>
An adhesive having an elastic modulus of 2 GPa or less.
Hereinafter, the hybrid structural member of the fiber-reinforced resin molded product and the metal of the present invention will be described in detail.

(Fiber reinforced plastic molded body (1))
The fiber-reinforced resin molded product that can be used for the hybrid structural member of the present invention contains reinforcing fibers and a matrix resin. The fiber-reinforced resin molded product of the present invention can be obtained, for example, by molding a fiber-reinforced resin material (SMC) containing a matrix resin in a fiber bundle group composed of a plurality of fiber bundles.

(Matrix resin)
As the matrix resin, a thermosetting resin and a thermoplastic resin can be used. As the matrix resin, only the thermosetting resin may be used, only the thermoplastic resin may be used, or both the thermosetting resin and the thermoplastic resin may be used.
When the fiber-reinforced resin molded product of the present invention is produced from SMC, a thermosetting resin is preferable as the matrix resin.

The thermosetting resin is not particularly limited, and includes epoxy resin, phenol resin, unsaturated polyester resin, vinyl ester resin, phenoxy resin, alkyd resin, urethane resin, urea resin, melamine resin, maleimide resin, cyanate resin and the like. Can be mentioned.
One type of thermosetting resin may be used alone, or two or more types may be used in combination.

Examples of the thermoplastic resin include polyolefin resins, polyamide resins, polyester resins, polyphenylene sulfide resins, polyether ketone resins, polyether sulfone resins, aromatic polyamide resins and the like. As the thermoplastic resin, one type may be used alone, or two or more types may be used in combination.

(Reinforcing fiber)
The type of reinforcing fiber that can be used in the fiber-reinforced resin molded body of the present invention is not particularly limited, and inorganic fiber, organic fiber, metal fiber, or a hybrid-structured reinforcing fiber that combines these can be used. .. Examples of the inorganic fiber include carbon fiber, graphite fiber, silicon carbide fiber, alumina fiber, tungsten carbide fiber, boron fiber, glass fiber and the like. Examples of the organic fiber include aramid fiber, high-density polyethylene fiber, other general nylon fiber, polyester and the like. Examples of the metal fiber include fibers such as stainless steel and iron, and carbon fibers coated with metal may also be used. Among these, carbon fiber is preferable in consideration of mechanical properties such as strength of the final molded product. The average fiber diameter of the reinforcing fibers is preferably 1 to 50 μm, more preferably 5 to 20 μm.

(Carbon fiber)
The carbon fiber is not particularly limited, and any carbon fiber such as polyacrylonitrile (PAN) type, petroleum / coal pitch type, rayon type, and lignin type can be used. In particular, PAN-based carbon fiber made from PAN is preferable because it is excellent in productivity and mechanical properties on an industrial scale. These are available as commercial products.

The carbon fibers that can be used in the fiber-reinforced resin molded product of the present invention are preferably surface-treated, particularly electrolytically treated. Examples of the surface treatment agent include epoxy-based sizing agents, urethane-based sizing agents, nylon-based sizing agents, olefin-based sizing agents, and the like. The surface treatment has the advantage of improving the tensile strength and bending strength.

(Fiber content, coefficient of variation of fiber content)
The fiber-reinforced resin molded product of the present invention has a coefficient of variation (hereinafter, also referred to as “variation coefficient Q”) of the fiber content of the reinforcing fiber per unit section of 0.1 mm square on the cut surface along the thickness thereof. It is 40% or less.

When the coefficient of variation Q is 40% or less, the fibers are evenly dispersed in the fiber-reinforced resin molded body and the resin-rich portion is suppressed, so that the adhesive strength and the fracture form between the fiber-reinforced resin molded body and the metal are suppressed. Variation is suppressed.
The coefficient of variation Q is obtained by cutting the fiber-reinforced resin molded body along the thickness direction, measuring the fiber content of the reinforcing fiber per 0.1 mm unit section at 2000 points on the cut surface, and using the standard deviation as the standard deviation. It means a value obtained by calculating an average value (hereinafter referred to as "average value P") and dividing the standard deviation by the average value P.

The upper limit of the coefficient of variation Q in the fiber-reinforced resin molded product used in the present invention is 40%, preferably 35%, and more preferably 30%.
When the coefficient of variation Q is not more than the upper limit value, a hybrid structural member of the fiber reinforced resin molded body and the metal in which the adhesive strength between the fiber reinforced resin molded body and the metal and the variation in the fracture form are suppressed can be obtained.

The coefficient of variation Q affects not only the dispersed state of the fibers in the fiber-reinforced resin molded body but also the fiber axial direction of each fiber. Specifically, for example, in the case of a fiber bundle having a circular cross-sectional shape, if the angle of the cut surface of the fiber bundle with respect to the fiber axis direction is 90 °, the cross-sectional shape of the fiber bundle on the cut surface is circular. On the other hand, when the angle of the cut surface of the fiber bundle with respect to the fiber axis direction is smaller than 90 °, the cross-sectional shape of the fiber bundle on the cut surface becomes elliptical. In this way, when the fiber axis direction of each fiber bundle changes, the cross-sectional shape of the fiber bundle for each unit section changes, and the proportion of the fiber bundle in the cross section changes, which affects the coefficient of variation Q.

The smaller the coefficient of variation Q is, the more evenly the fibers are dispersed in the fiber-reinforced resin molded product. However, the closer the coefficient of variation Q is to zero, the smaller the change in the cross-sectional shape of the fiber bundle for each unit section is, that is, the fiber axial direction of each fiber bundle is aligned in the fiber reinforced resin molded body. ..

In order to suppress variations in the adhesive strength between the fiber-reinforced resin molded body and the metal and the fractured form, it is preferable that the fiber directions of the fibers are random. From this, the lower limit of the coefficient of variation Q is preferably 10%, preferably 12%, and more preferably 15%.

When the coefficient of variation Q is at least the lower limit value, a hybrid structural member of the fiber reinforced resin molded body and the metal in which the adhesive strength between the fiber reinforced resin molded body and the metal and the variation in the fracture form are suppressed can be obtained.

The average fiber length of the fiber-reinforced resin molded product that can be used in the present invention is preferably 5 to 100 mm, more preferably 20 to 60 mm.
If the average fiber length of the fiber-reinforced resin molded product is at least the above lower limit value, a fiber-reinforced resin molded product having excellent physical properties can be obtained. If the above upper limit value or less is obtained, the fiber-reinforced resin material becomes easier to flow during molding, so that molding becomes easier.

(Adhesive (2))
Examples of the adhesive used in the present invention include vinyl acetate-based, polyvinyl alcohol-based, polyacetal-based, vinyl chloride-based, acrylic-based, polyethylene-based, cellulose-based, urea-based, resorcinol-based, melamine-based, and phenol-based (Novolak). , Water-soluble), epoxy-based, polyurethane-based, polyester-based, polyimide-based, polyaromatic-based, chlorobrene-based, nitrile rubber-based, SBR-based, polysulfide-based, butyl rubber-based, silicone rubber-based, epoxy-nylon-based, phenol-nitrile Examples include system, epoxy-nitrile system, epoxy-phenol system and the like.

The elastic modulus of the adhesive used in the present invention is preferably 2 GPa or less. If the elastic modulus of the adhesive is 2 GPa or more, the adhesive strength between the fiber-reinforced resin molded body and the metal is too high, and the fiber-reinforced resin molded body may be destroyed by the base material, and the fatigue resistance required for the structural member is high. Cannot be obtained.

The thickness of the adhesive that can be used in the present invention is preferably 0.1 to 4 mm, more preferably 0.1 to 1 mm. If the thickness of the adhesive layer is not less than the lower limit value, the fatigue resistance required for the structural member cannot be obtained, and if it is more than the upper limit value, the physical properties such as impact resistance required for the structural member cannot be obtained.

(Manufacturing method of hybrid structural member of fiber reinforced plastic molded product and metal)
For the hybrid structural member of the fiber reinforced resin molded product and the metal, the adhesive (2) is applied to the metal and bonded so as to overlap with the fiber reinforced resin molded product, and the adhesive is used at room temperature or as appropriate. It can be obtained by heating at a high temperature to solidify the adhesive.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the inventions described in the Examples.

(Fiber content average value P and fiber content coefficient of variation Q)
After cutting the fiber-reinforced resin molded product of Examples and Comparative Examples in the thickness direction and embedding the cut surface with methacrylic resin (product name "Technobit 4004", manufactured by Heraeus) so that the cut surface is covered. Polishing was performed to expose the cut surface. Next, the cut surface was imaged with an optical microscope (product name "BX51M", manufactured by Olympus Corporation) at a magnification of 100 times. The image of the cut surface is divided into 0.1 mm square unit sections by image processing software (product name "Winroof 2015, manufactured by Mitani Shoji Co., Ltd.", and then binarized with the brightness fighting value set to 136 to obtain fibers. Distinguished from the matrix resin. Next, for each of the 2000 unit compartments, the ratio of the area of the region where the brightness is equal to or higher than the fighting value (the region occupied by the fibers) to the area of the unit compartment was measured, and the fiber content was measured. Next, the average value (average value P) and the standard deviation of the fiber content for 2000 unit sections were calculated, and the standard deviation was divided by the average value P to calculate the variation coefficient Q.

(Measurement method of adhesive strength)
An adhesive is applied to the tip of the fiber-reinforced resin molded product (length 100 mm × width 25 mm × thickness 2 mm) of Examples and Comparative Examples, and an aluminum base material (length 100 mm × width 25 mm × thickness 2 mm) is used as a metal. A 1 kg weight was placed on top of the stack so as to overlap with the tip of the resin, and the mixture was heat-cured at 140 ° C. for 1 hour to obtain a hybrid member of a fiber-reinforced resin molded product and a metal, which was used as a test piece.

Both ends of this test piece were fixed by the machine name, pulled at a speed of 5 mm / min at room temperature, the shear strength was measured, and the fracture morphology was observed.
The shear strength is 10 MPa or more and the fracture form is the cohesive failure of the adhesive ○, the shear strength is 10 MPa or less and the fracture form is the cohesive failure of the adhesive Δ, and the fracture form is the substrate destruction or fiber of the fiber-reinforced resin molded product. When peeling occurred at the interface between the reinforced resin molded product and the metal, it was evaluated as x.

(Example 1)
As the fiber (trade name "TR50S15L", manufactured by Mitsubishi Rayon Co., Ltd.) was used.
A 75% solution of 1,1-di (t-butylperoxy) cyclohexane as a curing agent with respect to 100 parts by mass of an epoxy acrylate resin (product name: Neopol 8051, manufactured by Iupica Japan), which is a thermosetting resin (product name). : Perhexa C-75, manufactured by Nippon Oil & Fats Co., Ltd.) 0.5 parts by mass and 74% solution of t-butylperoxyisopropyl carbonate (product name: Kayacarboxylic BIC-75, manufactured by Kayaku Akzo) 0.5 parts by mass As an internal mold release agent, 0.35 parts by mass of a phosphate ester derivative composition (product name: MOLD WIZ INT-EQ-6, manufactured by Axel Plastic Research Lab et al., Tory Co., Ltd.) was added to add a thickener. As a stabilizer, 15.5 parts by mass of modified diphenylmethane diisocyanate (product name: Cosmonate LL, manufactured by Mitsui Kagaku Co., Ltd.) was added, and as a stabilizer, 1.4-benzoquinone, manufactured by Wako Pure Chemical Industries, Ltd., 0.02 parts by mass was added. After addition, these were thoroughly mixed and stirred to obtain a paste containing a matrix resin.

The paste was applied onto the conveyed first carrier sheet to form a first resin sheet having a thickness of 0.45 mm. Further, a carbon fiber bundle having a thickness of 0.05 mm and a width of 7.5 mm, which has been opened and separated, is cut with a cutting machine and dropped as a chopped fiber bundle having an average fiber length of 50.8 mm to have a thickness of 1.3 mm. A sheet-like fiber bundle group was formed. Between the first resin sheet and the cutting machine, a plurality of inclined combs having a circular cross section with a diameter of 3 mm were arranged side by side so as to be parallel to the traveling direction of the first resin sheet. The height of the inclined comb from the first resin sheet was 400 mm, the distance between adjacent inclined combs was 65 mm, and the logarithmic inclination angle in the horizontal direction of the inclined comb was 15 °. The line speed was 1.5 m / min.

Above the first carrier sheet, the paste on the second carrier sheet being conveyed in the opposite direction of the first carrier sheet is applied to form a second resin sheet having a thickness of 0.45 mm, and the conveying direction is reversed. Then, the second resin sheet was laminated on the sheet-shaped fiber bundle group. Further, the first resin sheet, the sheet-shaped fiber bundle group, and the laminated body of the second resin sheet were pre-impregnated and main-impregnated to obtain a sheet-shaped fiber-reinforced resin material having a thickness of 2 mm. Pre-impregnation includes a concavo-convex roll in which columnar convex portions (height of the convex portion: 3 mm, area of the tip of the convex portion: 38 mm2, pitch of the convex portion: 8 mm) are provided in a staggered manner on the outer peripheral surface of the roll. This was done with 5 pairs of rolls combined with flat rolls. This impregnation was performed from 11 pairs of flat rolls.

The obtained fiber-reinforced resin material was cured at a temperature of 25 ± 5 ° C. for 1 week, cut into 250 mm × 250 mm, and a panel molding die (300 mm × 300 mm × 2 mm, surface chrome) having a fitting number at the end. (Plating finish), the transport direction (MD direction) of the fiber reinforced resin material in the manufacturing apparatus was aligned, and two sheets (a total of about 156 g) were put into the center of the mold. Then, the fiber-reinforced resin material was heated and pressed in the mold under the conditions of 140 ° C., 8 MPa, and 5 minutes to obtain a fiber-reinforced resin molded product.
The fiber content P of the obtained fiber-reinforced resin molded product was 55.7%, and the fiber content coefficient of variation Q was 26.1%.

Next, the obtained fiber reinforced plastic molded body was cut into a length of 100 mm and a width of 25 mm, and IW2190 (an epoxy adhesive manufactured by 3M) was applied to an area of 12.5 mm and a width of 25 mm from the tip portion, and aluminum # was used as a metal. Adhere to the tip of 6000 (length 100 mm x width 25 mm x thickness 2 mm) so that it overlaps, place a 1 kg weight on top of the stack, heat cure at 140 ° C for 1 hour, and combine the fiber reinforced plastic molded body with the metal. The hybrid member of No. 1 was obtained and used as a test piece.

(Comparative Example 1)
Using STR120N131-KA6N (manufactured by Mitsubishi Rayon) as a fiber reinforced resin material, two 25 cm square test pieces with a thickness of 2 mm are cut out, stacked, and press-molded to obtain a fiber reinforced resin molded body on a 30 cm square plate. rice field. The average value P of the fiber content of the obtained molded product was 44.2%, and the coefficient of variation Q was 47.1%.

A hybrid member of a fiber-reinforced resin molded product and a metal was obtained in the same manner as in Example 1 and used as a test piece.

As is clear from Table 1, in Example 1, the shear strength was high and the fracture morphology was also good.

Since the fiber-reinforced resin molded product and the metal hybrid structural member of the present invention are excellent in adhesive strength and fracture form, they can be used in a wide range of fields such as aircraft members, automobile members, and sports equipment.

Claims (8)

A hybrid structural member of a fiber reinforced resin molded body and a metal in which the following fiber reinforced resin molded body (1) and a metal are integrated via an adhesive (2).
<Fiber reinforced plastic molded body (1)>
A fiber-reinforced resin molded body containing a fiber bundle in which a plurality of reinforcing fibers are bundled and a matrix resin, and the reinforcing fibers per unit section of 0.1 mm square on the cut surface in the thickness direction of the fiber-reinforced resin molded body. The fluctuation coefficient of the content rate is 40% or less.
<Adhesive (2)>
An adhesive having an elastic modulus of 2 GPa or less. The hybrid structural member according to claim 1, wherein the tensile adhesive shear strength of the hybrid structural member at 23 ° C. is 14 MPa or more. The hybrid structural member according to claim 1 or 2, wherein the average fiber length of the reinforcing fibers in the fiber-reinforced resin molded body is 5 to 100 mm. The hybrid structural member according to any one of claims 1 to 3, wherein the coefficient of variation of the reinforcing fiber content per unit section of 0.1 mm square is 10% or less. The hybrid structural member according to any one of claims 1 to 4, wherein the reinforcing fiber is carbon fiber. The hybrid structural member according to any one of claims 1 to 5, wherein the thickness of the adhesive is 0.1 or more and 4 mm or less. The hybrid structural member according to any one of claims 1 to 5, wherein the thickness of the adhesive is 0.1 or more and 1 mm or less. The hybrid structural member according to any one of claims 1 to 7, wherein the adhesive is an epoxy adhesive.