JP7093610B2 - Structural members - Google Patents

Description

The present invention relates to a structural member in which a wrought member using an aluminum alloy and a fiber reinforced resin material are composited.

In the field of vehicles, structural members such as bumper reinforces and door beams are required to be lightweight, shock-absorbing, and highly rigid.
Structural materials made of aluminum alloy are high-strength lightweight members, but in recent years, further weight reduction and impact absorption are required.
For example, Patent Document 1 discloses a CFRP reinforced pipe in which grooves are provided on each of the four side surfaces of a square pipe and a CFRP flat plate is fitted and bonded.
However, since the composite member disclosed in the same publication is intended for improving the torsional rigidity and not for improving the bending rigidity, fitting and adhering CFRP to all four side surfaces requires a manufacturing man-hour. Large and expensive.
Patent Document 2 discloses a beam-shaped member made of a shock absorbing material (aluminum alloy) that is easily plastically deformed on the side on which an impact load is applied and a high-strength lightweight material (fiber reinforced plastic) on the opposite side.
However, the composite member disclosed in the same gazette uses fiber reinforced plastic on the pulling side so that the shock absorber is plastically deformed, and the plastic reinforced with glass fiber rather than carbon fiber is used in the same gazette. The purpose is to increase the deflection of the entire length of the beam member, as clearly stated.
Therefore, it cannot withstand a local impact such as a pole collision, and there is a high possibility that the glass fiber reinforced plastic will break.
Patent Document 3 discloses a composite member in which a metal material and a fiber reinforced plastic material are adhesively bonded with an adhesive.
However, the invention disclosed in the same publication aims at facilitating the separation of the two materials at the time of recycling, and is insufficient for improving the high rigidity.

Japanese Unexamined Patent Publication No. 11-210937 Japanese Unexamined Patent Publication No. 6-101732 Japanese Patent Application Laid-Open No. 2002-240658

An object of the present invention is to provide a structural member in which a lightweight and highly rigid aluminum alloy wrought member and a carbon fiber reinforced member are combined.

The structural member according to the present invention is a bar-shaped structural member having a predetermined length, and is a stretched member using an aluminum alloy and a tensile stress when the stretched member receives a compressive bending load from the surface side. The carbon fiber reinforced resin member is bonded to the back surface side with an adhesive, and the carbon fiber reinforced resin member contains 50 to 70% of carbon fibers oriented in the longitudinal direction of the wrought member in terms of volume ratio. It is characterized in that it is a sheet-like composite material.
Here, the term "bar-shaped structural member" having a predetermined length means a member having a predetermined length that can be used as a structural member of a vehicle, various industrial machines, or the like.
Examples of structural members for vehicles include bumper reinforces and door beams.
When a bending compressive load such as a pole collision is applied to such a structural member, it is transmitted as a tensile stress load to the carbon fiber reinforced resin member on the back surface side.
Therefore, the present invention uses a carbon fiber reinforced resin (CFRP) in which carbon fibers containing 50 to 70% by volume are oriented in the longitudinal direction of the structural member.

The wrought member made of an aluminum alloy according to the present invention preferably has a 0.2% proof stress value of 420 MPa or more.
By using a stretch member with high yield strength, weight reduction can be achieved.
Here, the wrought member may be an extruded material, an drawn material, or the like, and the chemical composition of the aluminum alloy is JIS7000 series, and those in the following range can be used.
Hereinafter, all in mass%, Zn: 6.0 to 7.2%, Mg: 1.0 to 1.9%, Cu: 0.1 to 0.4%, Zr: 0.15 to 0.25%. , Ti: 0.05% or less, and the balance is Al and impurities.
Here, Zn: 6.4 to 7.0%, Mg: 1.05 to 1.60%, and Cu: 0.2 to 0.3% are preferable.
The impurities are preferably Si: 0.1% or less and Fe: 0.25% or less.
Further, Cr may be contained in the range of 0.001 to 0.05% and Mn may be contained in the range of 0.3% or less.
The cross-sectional shape of the extension member may be a solid cross-sectional shape such as a U-shape, a hollow cross-sectional shape such as a mouth-shaped shape, a Japanese-shaped shape, or an eye-shaped shape.

In the present invention, the carbon fiber reinforced resin member may be processed so that the carbon fibers are exposed on the adhesive surface, and the carbon fibers are exposed on the adhesive surface by, for example, shot blasting to provide an adhesive. Improves adhesion.
The surface roughness of the exposed surface is in the range of Rz = 5 to 50 μm, preferably in the range of Rz = 20 to 30 μm.

In the present invention, the adhesive preferably has an adhesive shear force of 15 MPa or more.
The elongation of the adhesive is preferably 75% or more and 250% or less.
As a result, the reinforcing effect is exhibited while following the bending deformation of the wrought member made of an aluminum alloy.

In the structural member according to the present invention, when a bending load in the pushing direction is applied to the stretched member of the aluminum alloy, it is transmitted as tensile stress to the CFRP member on the opposite side, so that the structural member can withstand the deformation while suppressing the amount of deformation as a whole. It is effective for improving the load and reducing the weight.

The chemical composition of the aluminum alloy used for the evaluation is shown. The manufacturing conditions and physical property values of the extruded member (extruded profile) used for the evaluation are shown. The physical property values of the carbon fiber reinforced resin (CFRP) used for the evaluation are shown. The adhesive used for the evaluation and its adhesive conditions are shown. The evaluation result of the performance (strength, rigidity) of the structural member is shown. The evaluation method of the structural member is shown. The sample used for the evaluation is shown. (A) to (c) show an example of the cross-sectional shape of the structural member which concerns on this invention. (A) to (c) show an example of the bonding position of the CFRP material. The range of application of CFRP material is shown. Examples of structural members to which CFRP material is partially attached are shown in (a) and (b).

Hereinafter, the structural members have been manufactured and evaluated under various conditions, and will be described below.
The molten aluminum alloy having the chemical composition shown in the table of FIG. 1 was adjusted to cast a cylindrical billet having a diameter of 8 inches.
The cast billets were homogenized at the HOMO holding temperature in the table of FIG.
The homogenization treatment temperature is preferably in the range of 500 to 540 ° C.
An extruded profile with a cross-sectional shape was extruded.
The extrusion conditions are shown in the table of FIG.
The billet temperature is preferably in the range of 490 to 530 ° C, and the die temperature during extrusion is preferably in the range of 440 to 500 ° C.
It is preferable to set the cooling rate to 80 ° C./min or more, preferably 100 ° C./min or more by cooling the fan immediately after extrusion.
After that, a two-stage artificial aging treatment at 50 to 140 ° C. + 140 to 200 ° C. was performed.
The physical characteristics of the extruded profile are shown in the table of FIG.
In the present invention, the target is a proof stress of 420 MPa or more and an elongation of 10% or more.
In the table, <toughness> was tested according to JIS Z 2242 "Charpy impact test method for metallic materials".
The target was 12 J / cm ² or more.
<SCC> was carried out according to JIS H 8711 "Stress corrosion cracking test method for aluminum alloy", and the test was carried out with a stress value of 40% applied by a three-point bending jig.
The time until cracks that could cause recrystallization were evaluated.
The target was 72 hours or more.
For <recrystallization rate>, the area ratio of the recrystallized layer to the cross-sectional area of the extruded profile was determined.
The target is 20% or less.
The physical property values of the CFRP member used for the evaluation are shown in FIG.
In the table, 0 ° in the CF fiber direction means that the fibers are oriented in the longitudinal direction.
The bonding conditions between the extruded aluminum alloy profile and the CFRP member are shown in the table of FIG.
In addition, Comparative Example 13 is a structural member to which the CFRP member is not bonded.
The cross section of the sample used for the evaluation is shown in FIG.
The thickness of the adhesive layer was in the range of 50 μm to 1 mm, and no significant difference in rigidity appeared.

FIG. 6 shows an evaluation method for structural members.
The total length of the structural member 10 is 1200 mm, so that the extruded member (extruded profile) 11 is located on the side (front surface) where the pushing load F by the pole 2 is applied, and the CFRP member 12 is adhesively bonded to the back surface on the opposite side. , Placed between fulcrums 1 and 1 with a span of 880 mm.
The pole diameter was 203.2 mm, and the pole was pushed downward at a constant speed, and the flexural rigidity (kN / mm) and the strength due to the total plastic moment (kNm) were measured.
The results are shown in the table of FIG.
In the present invention, the target is a rigidity of 4.1 kN / mm or more and a strength of 60 kNm or more, but Examples 1 to 6 have cleared them.
In Examples 7 to 9, the above target values could not be cleared, but the values were close to those, and there was no problem in practical use.

The contents of the evaluation results will be explained concretely.
As shown in FIG. 9A, as a method of attaching the CFRP material 12, a stretched member (aluminum extruded material) 11 is partially attached along the back surface side having a rib in a hollow cross section (adhesive range of FIG. 4). (Reinforcement rate 60%) and the entire back surface side (reinforcement rate 100%) are compared.
In Examples 3 and 4, the CFRP material is partially used because the proof stress of the wrought member is the same as L ₁ = 500 mm centering on the central portion of the reinforcing length shown in FIGS. 9 (b) and 10. It became clear that the target can be cleared even if it is attached to.

Next, as shown in FIGS. 9 (b) and 10, the CFRP material 12 is placed in the center of the stretching member 11 with L ₀ = 1000 mm (Example 2) and L ₁ = 500 mm from the center thereof. Comparing with (Example 3), it can be seen that the strength and rigidity clear the target even at half of L ₁ = 500 mm and L ₀ = 1000.

The elongation of the adhesive is necessary to follow the bending deformation of the wrought material, and it is preferable that it has 75% or more from the results of Examples 1 to 9 and the results of Comparative Examples 18 and 19, and more preferably. As shown in 1 to 5, the range of 75 to 120% is good.

Comparative Example 13 had no CFRP material, and Comparative Examples 10 and 12 had a proof stress of less than 420 MPa of the wrought member, and the strength and rigidity of the structural member could not meet the targets.
Comparative Examples 11 and 12 have poor adhesive elongation, and Comparative Example 15 has a low adhesive shear strength.

8 and 11 show examples of cross-sectional shapes of the structural material according to the present invention.
FIG. 8 is an example in which the CFRP material is adhered to the back surface side over the entire width direction centering on the central portion, and FIG. 12 is an example in which the CFRP material is partially adhered to the back surface side near the rib.
In this case, as shown in FIG. 9C, it is preferable that the CFRP material 12 is adhered to the 11b side, which is relatively thinner than the 11a having a thick cross-sectional wall thickness of the extension member 11.

1 fulcrum 2 pole 10 structural member 11 extension member 12 CFRP member

Claims (1)

A bar-shaped structural member having a length of 1200 mm or more.
All in mass%, Zn: 6.0 to 7.2%, Mg: 1.0 to 1.9%, Cu: 0.1 to 0.4%, Zr: 0.15 to 0.25%, Ti. : 0.05% or less and the wrought member using an aluminum alloy whose balance is Al and impurities, and the back side where tensile stress is generated when the wrought member receives a compressive bending load from the front side. It has a carbon fiber reinforced resin member that is directly bonded to the aluminum fiber with an adhesive.
The carbon fiber reinforced resin member is a sheet-shaped composite material containing 50 to 70% by volume of carbon fibers oriented in the longitudinal direction of the stretched member, and is processed so that the carbon fibers are exposed on the adhesive surface. A structural member characterized by being .

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