Metal composite material and manufacturing method thereof

Abstract

Provided is a metal composite material which contains an adhesive layer and has superior rigidity than conventional metal composite materials. In this metal composite material (10), the sheet thickness (h1) of a thin steel sheet (1) and the sheet thickness (h2) of a low-specific-gravity sheet material (2) are set so as to satisfy the following numerical formula (1) that represents the bending rigidity [D] of the metal composite material (10) that has been set in advance: "numerical formula 1" imgabs0 # (in numerical formula (1), b is the width of the metal composite material (1), E1 is the longitudinal elastic coefficient of the thin steel sheet (1), E2 is the longitudinal elastic coefficient of the low-specific-gravity sheet material (2), and the thickness (h2) of the low-specific-gravity sheet material (2) is the thickness (h1) of the thin steel sheet (1). V1 is the Poisson's ratio of the thin steel plate (1), v2 is the Poisson's ratio of the low-specific-gravity sheet material (2), h1 is the sheet thickness of the thin steel plate (1), h2 is the sheet thickness of the low-specific-gravity sheet material (2), h3 is the thickness of the adhesive layer (3), h0 is the thickness of the adhesive layer (3) from the bonding interface between the low-specific-gravity sheet material (2) and the adhesive layer (3) to the neutral axis (Ax), and h1 and h2 satisfy the relationship h1 < h2.

Description

Technical Field

[0001] The present invention relates to a metal composite material and a method for manufacturing the same. Background Art

[0002] In recent years, we have actively promoted the participation of vulnerable groups such as the elderly, the disabled, and children in sustainable transportation systems. In order to achieve this, we are committed to research and development to further improve the safety and convenience of transportation through the development of vehicle enhancement effects.

[0003] In the past, a lower longitudinal beam structure is known, which has a plate member that divides the closed cross section of the lower longitudinal beam in the vehicle width direction, and a pair of reinforcing members arranged in the closed cross section of the lower longitudinal beam in a manner of sandwiching the plate member from both sides in the vehicle width direction (for example, refer to Patent Document 1). The reinforcing members of the lower longitudinal beam structure are respectively roughly hat-shaped when observed in cross-section, and have a bulging portion bonded to the plate member, and a flange portion bonded to the inner wall surface of the lower longitudinal beam. According to such a lower longitudinal beam structure, the rigidity of the lower longitudinal beam is guaranteed by the plate member and the reinforcing member, and the collapse stroke of the lower longitudinal beam during a side collision can be ensured to be larger. As a result, the lower longitudinal beam can efficiently absorb energy during a side collision.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2010-143461 Summary of the invention

[0007] However, in the conventional side sill structure (for example, see Patent Document 1), an adhesive layer is sandwiched between the reinforcing member and the plate member. Therefore, in the side sill structure, the adhesive layer may be peeled off first before the reinforcing member and the plate member are broken during a side collision, and the reinforcing effect cannot be fully exerted. Therefore, it is desired that a metal composite material that is suitable for a vehicle body structure such as the side sill structure and that includes an adhesive layer and helps transfer the collision load exert a better reinforcing effect.

[0008] The present invention aims to provide a metal composite material having an adhesive layer and excellent reinforcement effect without causing damage starting from the adhesive, and a method for producing the same, which can contribute to reducing the weight of a vehicle body required for collision safety.

[0009] The present invention for achieving the above-mentioned problems is a metal composite material, which comprises: a thin steel plate; a low-density plate having a smaller specific gravity and lower strength than the thin steel plate; and an adhesive layer which joins the thin steel plate and the low-density plate and has a strength lower than that of the thin steel plate and the low-density plate. The metal composite material is characterized in that the thickness of the thin steel plate and the thickness of the low-density plate are set in a manner that satisfies the following formula (1) and the following formula (2) representing a predetermined bending rigidity [D] of the metal composite material.

[0010] [Formula 1]

[0011]

[0012] Wherein, in formula (1), b is the width of the metal composite material, E1 is the longitudinal elastic coefficient of the thin steel plate, E2 is the longitudinal elastic coefficient of the low specific gravity plate, ν1 is the Poisson's ratio of the thin steel plate, ν2 is the Poisson's ratio of the low specific gravity plate, h1 is the plate thickness of the thin steel plate, h2 is the plate thickness of the low specific gravity plate, h3 is the thickness of the adhesive layer, h0 is the thickness of the adhesive layer from the bonding interface between the low specific gravity plate and the adhesive layer to the neutral axis,

[0013] [Formula 2]

[0014] h1<h2…(2)

[0015] In the formula (2), h1 and h2 have the same meanings as h1 and h2 in the formula (1).

[0016] In addition, the present invention that achieves the problem is a method for manufacturing a metal composite material, comprising: a process of preparing a thin steel plate and a low-specific gravity plate, wherein the low-specific gravity plate has a smaller specific gravity and lower strength than the thin steel plate; and a process of joining the thin steel plate and the low-specific gravity plate via an adhesive layer having lower strength than the thin steel plate and the low-specific gravity plate. The method for manufacturing the metal composite material is characterized in that the joining process between the thin steel plate and the low-specific gravity plate is performed in such a way that the neutral axis of the metal composite material during bending deformation is set in the adhesive layer, or is set at the joining interface between the adhesive layer and the thin steel plate or between the adhesive layer and the low-specific gravity plate.

[0017] Effects of the Invention

[0018] According to the present invention, a metal composite material including an adhesive layer, having excellent reinforcement effect without causing destruction starting from the adhesive, and contributing to lightweighting of a vehicle body required for collision safety, and a method for producing the same can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a diagram for explaining the structure of a metal composite material according to an embodiment of the present invention.

[0020] Figure 2 This is a schematic diagram showing the relationship between the thickness of a thin steel plate, a low-density plate, and an adhesive layer in a metal composite material, and the stress distribution.

[0021] Figure 3 This is a perspective view showing a side sill structure to which a metal composite material according to an embodiment of the present invention is applied, viewed downward from the vehicle interior.

[0022] Figure 4 yes Figure 3 IV-IV cross-sectional view.

[0023] Figure 5 It is a schematic explanatory diagram showing the deformation behavior of the side sill structure during a side collision.

[0024] Figure 6 is a schematic diagram of a test member of a metal composite material used in an example of the present invention.

[0025] Description of Reference Numerals

[0026] 1 Thin steel plate

[0027] 2Low specific gravity sheet

[0028] 3 Adhesive layer

[0029] 10. Metal composite materials DETAILED DESCRIPTION

[0030] Next, refer to the attached Figure 1 Modes (embodiments) for carrying out the metal composite material of the present invention will be described in detail.

[0031] As described in detail later, the metal composite material of the present embodiment has an asymmetric sandwich structure composed of a plurality of plate components. The metal composite material of the present embodiment envisions a composite material in which a predetermined plate-like component is overlapped on a thin steel plate via an adhesive layer. Specifically, the metal composite material is configured so that when a buckling stress is generated in the metal composite material by a load input in a direction along a bonding surface in the metal composite material, a neutral axis in the metal composite material is set in the adhesive layer, or is set at the bonding interface between the adhesive layer and the thin steel plate, or is set at the bonding interface between the adhesive layer and the plate-like component. Preferably, the neutral axis is set at the bonding interface between the adhesive layer and the thin steel plate, or is set at the bonding interface between the adhesive layer and the plate-like component.

[0032] The neutral axis in the metal composite material of the present embodiment is set based on a relational expression described in detail later.

[0033] Figure 1 It is a diagram for explaining the structure of a metal composite material 10 according to an embodiment of the present invention.

[0034] like Figure 1 As shown, the metal composite material 10 of this embodiment includes: a thin steel plate 1; a low-specific-gravity plate 2 having a smaller specific gravity than the thin steel plate 1; and an adhesive layer 3 for bonding the thin steel plate 1 and the low-specific-gravity plate 2.

[0035] The thin steel plate 1 of this embodiment may be a known one or a commercially available one. The thin steel plate 1 of this embodiment is assumed to be a high-tensile steel plate with a thickness of 1.0 mm to 2.0 mm and a tensile strength of 340 MPa or more, but is not limited thereto.

[0036] In addition, if Figure 1 As shown, the plate thickness h2 of the low specific gravity plate 2 is greater than the plate thickness h1 of the thin steel plate 1 (h1<h2).

[0037] Specific examples of the low-density plate 2 include, but are not limited to, aluminum alloy plates (including duralumin plates), magnesium alloy plates, CFRP (Carbon Fiber Reinforced Plastics) plates, and GFRP (Glass Fiber-Reinforced Plastics) plates. Therefore, the low-density plate 2 can be appropriately selected in accordance with the required bending strength of the metal composite material 10 predetermined according to the type of vehicle body structure to which the metal composite material 10 is applied (for example, a side sill structure, a center pillar structure, etc.).

[0038] As the adhesive layer 3, for example, a material composed of a structural adhesive such as an epoxy-based adhesive or a urethane-based adhesive is conceivable, but the adhesive layer 3 is not limited thereto.

[0039] Alternatively, the adhesive layer 3 may be formed of a material composed of an injection molding resin (thermoplastic resin) injected between the thin steel plate 1 and the low specific gravity plate material 2 placed in a predetermined mold.

[0040] Such an adhesive layer 3 has a longitudinal elastic modulus significantly lower than that of the thin steel plate 1 .

[0041] In addition, the strength of the adhesive layer 3 is also significantly lower than that of the thin steel plate 1 .

[0042] In addition, the strength of the adhesive layer 3 is also significantly lower than that of the low specific gravity plate material 2 .

[0043] like Figure 1 As shown in FIG. 1 , the thickness h3 of the adhesive layer 3 is greater than the thickness h1 of the thin steel plate 1 (h1 ≤ h3). Figure 1As shown, the thickness h3 of the adhesive layer 3 is preferably thinner than the thickness h2 of the low specific gravity plate material 2 (h2>h3).

[0044] like Figure 1 As shown, the thickness h of the metal composite material 10 of the present embodiment is obtained by adding the thickness h1 of the thin steel plate 1, the thickness h3 of the adhesive layer 3, and the thickness h2 of the low specific gravity plate material 2 (h=h1+h3+h2).

[0045] like Figure 1 As shown, the neutral axis Ax of the metal composite material 10 of the present embodiment is set, for example, in the adhesive layer 3. Alternatively, although not shown, the neutral axis Ax is set at the bonding interface between the adhesive layer 3 and the thin steel plate 1, or at the bonding interface between the adhesive layer 3 and the low specific gravity plate 2.

[0046] Specifically, the metal composite material 10 sets the plate thickness h1 of the thin steel plate 1 and the plate thickness h2 of the low specific gravity plate 2 in a manner that satisfies the following formula (1) and the following formula (2) representing the bending rigidity [D] of the metal composite material, thereby setting the neutral axis Ax in the adhesive layer 3, or at the bonding interface between the adhesive layer 3 and the thin steel plate 1, or at the bonding interface between the adhesive layer 3 and the low specific gravity plate 2, preferably, at the bonding interface between the adhesive layer 3 and the thin steel plate 1, or at the bonding interface between the adhesive layer 3 and the low specific gravity plate 2.

[0047] [Formula 3]

[0048]

[0049] [Formula 4]

[0050] h1<h2…(2)

[0051] In the formula (1), b is the width of the metal composite material 10 (refer to Figure 1 ), E1 is a thin steel plate 1 (refer to Figure 1 ) is the longitudinal elastic coefficient, E2 is the low specific gravity plate 2 (refer to Figure 1 ) is the longitudinal elastic coefficient of the thin steel plate 1 (refer to Figure 1 ) is the Poisson's ratio, ν2 is the Poisson's ratio of the low specific gravity plate 2 (refer to Figure 1 ), h1 is the thin steel plate 1 (refer to Figure 1 ) plate thickness, h2 is the low specific gravity plate 2 (refer to Figure 1 ) is the thickness of the plate, h3 is the thickness of the adhesive layer 3 (refer to Figure 1 ) thickness. And, if Figure 1As shown, h0 is the thickness of the adhesive layer 3 from the bonding interface between the low specific gravity plate 2 and the adhesive layer 3 to the neutral axis Ax. In the formula (2), h1 and h2 have the same meanings as h1 and h2 in the above formula (1).

[0052] The neutral axis Ax is set to be located in the adhesive layer 3, or at the bonding interface between the adhesive layer 3 and the thin steel plate 1, or at the bonding interface between the adhesive layer 3 and the low specific gravity plate 2. That is, h0 satisfies 0≤h0≤h3.

[0053] Next, the inventive principle of the metal composite material 10 according to the present embodiment will be described.

[0054] Figure 2 Schematic diagram showing the relationship between the thicknesses h1, h2, and h3 of the thin steel plate 1, the low specific gravity plate 2, and the adhesive layer 3 in the metal composite material 10 and the stress distribution.

[0055] like Figure 2 As shown, in this embodiment, it is assumed that a bending moment M acts on the metal composite material 10 in such a manner that the low specific gravity plate material 2 is compressed by the load L input in the direction along the joint surface in the metal composite material 10. That is, in this embodiment, it is assumed that a buckling stress is generated in the metal composite material 10. At this time, the vertical stress generated in the thin steel plate 1 behaves elastically before the metal composite material 10 is destroyed.

[0056] The longitudinal elastic coefficient E3 of the adhesive layer 3 is smaller than the longitudinal elastic coefficient E1 of the thin steel plate 1 and the longitudinal elastic coefficient E2 of the low specific gravity plate 2 (E3<E1, E3<E2). This can eliminate the need for the adhesive layer 3 to bear the bending moment.

[0057] However, the metal composite material 10 of this embodiment, which is an asymmetric sandwich structure in which the longitudinal elastic coefficients E1, E2 and the breaking strength of the thin steel plate 1 and the low specific gravity plate 2 are different, is set as follows. Figure 2 As shown, the neutral axis Ax does not coincide with the center of gravity.

[0058] Specifically, Figure 2 As shown, the neutral axis Ax is set at a position from the bonding interface between the low-specific-gravity plate material 2 and the adhesive layer 3 to a local thickness h0 of the adhesive layer 3 .

[0059] That is, h0 can be defined as shown in the following equation (3) based on the so-called "beam theory".

[0060] [Formula 5]

[0061]

[0062] In the above formula (3), E1 is the thin steel plate 1 (refer to Figure 2 ) is the longitudinal elastic coefficient of the low specific gravity plate 2 (refer to Figure 2 ) is the longitudinal elastic coefficient of the thin steel plate 1 (refer to Figure 2 ) plate thickness, h2 is the low specific gravity plate 2 (refer to Figure 2 ) is the plate thickness, and h3 is the thickness of the adhesive layer 3 (refer to Figure 2 ). Furthermore, the thickness h3 of the adhesive layer 3 is greater than or equal to the thickness h1 of the thin steel plate 1 and thinner than the thickness h2 of the low specific gravity plate 2 (h1≤h3, h2>h3).

[0063] in addition, Figure 2 The maximum bending stress σ1 generated in the thin steel plate 1 by the bending moment M shown is defined by the following formula (α): Figure 2 The maximum bending stress σ2 generated in the low specific gravity plate material 2 by the bending moment M is defined by the following formula (β).

[0064] [Formula 6]

[0065]

[0066] [Formula 7]

[0067]

[0068] Here, E1, h0, h1 and h3 in formula (α), and E2, h0 and h2 in formula (β) have the same meanings as E1, E2, h0, h1, h2 and h3 in formula (3). In addition, D in formula (α) and formula (β) is the metal composite material 10 (refer to Figure 2 )'s bending rigidity.

[0069] Furthermore, as described above, the adhesive layer 3 (see Figure 2 ) in the bending moment M (refer to Figure 2 ) is shared, therefore, the metal composite material 10 (refer to Figure 2 ) can be expressed by the following formula (γ).

[0070] [Formula 8]

[0071] D=E1I1+E2I2…(γ)

[0072] In the formula (γ), E1 has the same meaning as E1 in the above formula (α), and E2 has the same meaning as E2 in the above formula (β).

[0073] Furthermore, I1 is the secondary moment of cross section of the thin steel plate 1, and I2 is the secondary moment of cross section of the low specific gravity plate material 2, so the equation (γ) becomes the equation (1).

[0074] [Formula 9]

[0075]

[0076] The metal composite material 10 of this embodiment (see Figure 2 ) The low specific gravity plate 2 (reference Figure 2 ) has a plate thickness h2 greater than that of the thin steel plate 1 (refer to Figure 2 ) is set so as to satisfy the equation (1) with the thickness h1 (h1 < h2) of the thin steel plate 1 (refer to Figure 2 ) plate thickness h1 and low specific gravity plate 2 (refer to Figure 2 ) of the plate thickness h2, thus, the neutral axis Ax (the position of h0) is set in the adhesive layer 3 (0<h0<h3), or is set at the bonding interface between the adhesive layer 3 and the thin steel plate 1 (h0=h3), or is set at the bonding interface between the adhesive layer 3 and the low specific gravity plate 2 (h0=0). Preferably, although the illustration is omitted, the neutral axis Ax (the position of h0) is set at the adhesive layer 3 (refer to Figure 2 ) and thin steel plate 1 (refer to Figure 2 ) between the bonding interface, or the adhesive layer 3 (refer to Figure 2 ) and low specific gravity plate 2 (refer to Figure 2 ) between the bonding interfaces.

[0077] That is, the metal composite material 10 (see Figure 2 ) is configured such that when a bending moment M (see Figure 2 ), the neutral axis Ax (position of h0) is set at the adhesive layer 3 with the lowest strength (refer to Figure 2 ).

[0078] A method for manufacturing such a metal composite material 10 includes preparing a thin steel plate 1 (see Figure 1 ) and low specific gravity plate 2 (refer to Figure 1 ) and bonding the thin steel plate 1 and the low specific gravity plate 2 via the adhesive layer 3 (refer to Figure 1 )The second step of joining.

[0079] Furthermore, in the manufacturing method, the plate thickness h1 of the thin steel plate 1 and the plate thickness h2 of the low-density plate 2 of the metal composite material 10 are set in a manner to satisfy the above-mentioned numerical formula (1) representing the bending rigidity D which is pre-set according to the type of specific structure such as the lower longitudinal beam structure and the center pillar structure. Thus, the neutral axis Ax of the metal composite material 10 is set at a predetermined position. That is, the neutral axis Ax is set in the adhesive layer 3 (0<h0<h3), or is set at the bonding interface between the adhesive layer 3 and the thin steel plate 1 (h0=h3), or is set at the bonding interface between the adhesive layer 3 and the low-density plate 2 (h0=0). Preferably, the neutral axis Ax is set at the bonding interface between the adhesive layer 3 and the thin steel plate 1, or is set at the bonding interface between the adhesive layer 3 and the low-density plate 2.

[0080] Next, the metal composite material 10 (see Figure 1 Here, a side sill structure is used as an example of a vehicle structure to specifically describe how the metal composite material 10 is used.

[0081] Figure 3 2 is a perspective view showing the side sill structure 20 viewed downward from the vehicle interior. Figure 3 , the up-down, front-back, left-right directions indicated by arrows coincide with the up-down, front-back, left-right directions of the vehicle having the side sill structure 20. In the following description, the left-right direction of the vehicle may be referred to as the vehicle width direction.

[0082] like Figure 3 As shown, the side sill S constituting the side sill structure 20 is a vehicle frame member extending in the vehicle front-rear direction at the side of the lower portion of the vehicle.

[0083] To the vehicle width direction inner side of the side sill S, the vehicle width direction outer side edge of the floor panel 8a is joined by spot welding or the like.

[0084] A floor cross member 8c extending in the vehicle width direction is disposed on the floor panel 8a. The floor cross member 8c has a hat shape open downward when viewed in a cross-section intersecting the extending direction. A flange F10 of the floor cross member 8c corresponding to the eaves of the hat shape is joined to the floor panel 8a by spot welding or the like.

[0085] The vehicle width direction outer side end portion of the floor cross member 8 c is welded to the vehicle width direction inner side of the side sill S.

[0086] The side sill S constituting the side sill structure 20 includes a side sill inner member S2 , a side sill outer member S1 , a panel member S4 , a reinforcement S3 , and a bulkhead 5 .

[0087] The side sill inner member S2 is arranged on the inner side in the vehicle width direction compared with the side sill outer member S1 ( Figure 3), in the direction of the long side ( Figure 3 When viewed in cross section (i.e., in the front-rear direction of the vehicle), the side sill inner member S2 is in the shape of a hat that is open to the outside in the vehicle width direction. Specifically, the lower side sill inner member S2 is configured to include a bulging portion 24, an upper flange F6, and a lower flange F7.

[0088] The side sill outer member S1 is arranged on the vehicle width direction outer side of the side sill inner member S2 ( Figure 3 The lower side beam outer member S1 is in the direction of the long side ( Figure 3 When viewed in cross section (i.e., in the front-rear direction of the vehicle), the side sill outer member S1 is in the shape of a hat that is open toward the inner side in the vehicle width direction. Specifically, the side sill outer member S1 includes a bulging portion 14, an upper flange F4, and a lower flange F5.

[0089] The plate member S4 is formed by making its plate surface face the vehicle width direction and along the long side direction of the lower side member S ( Figure 3 It is formed into a roughly flat plate with a long dimension extending in the front-to-back direction.

[0090] The panel member S4 is sandwiched between the flanges F6 and F7 of the side sill inner member S2 and the flanges F4 and F5 of the side sill outer member S1 and joined by overlapping welding of three sheets.

[0091] Figure 3 In the figure, the bulkheads 5 indicated by the dashed lines (dotted lines) are arranged to be spaced apart from each other in the long-side direction (front-rear direction) of the side sill S so as to correspond to the pair of floor cross members 8c. The bulkhead 5 is arranged in the bulged portion 24 of the side sill inner member S2 so as to be located inside the plate member S4 in the vehicle width direction.

[0092] The position of the bulkhead 5 in the bulged portion 24 coincides with the joint between the floor cross member 8 c and the side sill inner member S2 in the front-rear direction.

[0093] The bulkhead 5 of the present embodiment is oriented inward in the vehicle width direction ( Figure 3 left side) open hat shape.

[0094] The bulkhead 5 is joined to the inner wall of the side sill inner S2 by spot welding or the like.

[0095] The reinforcement member S3 is formed by having a longitudinal direction ( Figure 3 The reinforcement member S3 is a long resin member made of fiber-reinforced resin or the like and having a substantially M-shaped cross-section and extending in the front-rear direction. The reinforcement member S3 is arranged inside the bulged portion 14 of the side sill outer member S1.

[0096] As Figure 3 IV-IV cross-sectional view Figure 4As shown, the reinforcement S3 has a pair of upper and lower outer convex parts 31 and an inner convex part 32 protruding toward the plate member S4 between the outer convex parts 31. The protruding tip of the inner convex part 32 is engaged with the plate member S4 by fitting or the like.

[0097] The upper outer convex portion 31 is formed so as to be in close contact with the upper wall 11 and the outer wall 12 of the side sill outer member S1 at the corner formed by the upper wall 11 and the outer wall 12. The upper outer convex portion 31 is bonded to the side sill outer member S1 by the structural adhesive A so as to be integrally formed in the range from the upper wall 11 to the outer wall 12.

[0098] The lower outer convex portion 31 is formed so as to be in close contact with the lower wall 13 and the outer wall 12 of the side sill outer member S1 at the corner formed by the lower wall 13 and the outer wall 12. The lower outer convex portion 31 is bonded to the side sill outer member S1 by the structural adhesive A so as to be integrally formed in the range from the lower wall 13 to the outer wall 12.

[0099] In such a lower side member structure 20, Figure 4 As shown, a pair of upper and lower metal composite materials 10 are provided in portions corresponding to the upper wall 11 and the lower wall 13 of the side sill outer member S1.

[0100] That is, the metal composite material 10 of the side sill structure 20 comprises a thin steel plate 1 (see Figure 1 ); low specific gravity plate 2 composed of a fiber-reinforced resin reinforcement member S3 (reference Figure 1 ); and the adhesive layer 19 composed of the structural adhesive A (reference Figure 1 ).

[0101] <Effects>

[0102] Next, the effects achieved by the metal composite material 10 of the present embodiment will be described.

[0103] In the metal composite material 10 of the present embodiment, the plate thickness h1 of the thin steel plate 1 and the plate thickness h2 of the low specific gravity plate material 2 are set so as to satisfy the above equations (1) and (2) representing the preset bending rigidity D of the above metal composite material 10 .

[0104] According to such a metal composite material 10, the neutral axis Ax is set in the adhesive layer 3 (0<h0<h3), or is set at the bonding interface between the adhesive layer 3 and the thin steel plate 1 (h0=h3), or is set at the bonding interface between the adhesive layer 3 and the low specific gravity plate 2 (h0=0), and preferably, the neutral axis Ax is set at the bonding interface between the adhesive layer 3 and the thin steel plate 1, or is set at the bonding interface between the adhesive layer 3 and the low specific gravity plate 2. Thus, when a bending moment M is applied to the metal composite material 10, the neutral axis Ax is set at the adhesive layer 3 with the lowest strength.

[0105] In the metal composite material 10, stress is not applied to the adhesive layer 3 where the neutral plane (neutral axis Ax) is located, and the low specific gravity plate 2 is prevented from peeling off from the thin steel plate 1. The metal composite material 10 can exhibit higher bending rigidity than conventional metal composite materials of the same weight.

[0106] In addition, the metal composite material 10 has an asymmetric sandwich structure by satisfying the above formula (1) and the above formula (2). Therefore, the metal composite material 10 can suppress out-of-plane deformation in accordance with the position of the neutral axis Ax adjusted as described above. The metal composite material 10 can fully utilize the material properties that cannot be fully utilized by the conventional thin steel plate, and can improve the buckling strength of the thin steel plate 1.

[0107] Figure 5 (a) to (c) are in the order of (a), (b) and (c) to represent the metal composite material 10 (refer to Figure 4 ) of the lower side member structure 20 (refer to Figure 4 ) is a schematic diagram illustrating the deformation behavior during a side collision. In addition, Figure 5 The reference numeral 50 in (a) to (c) indicates an object relatively close to the side sill S. As shown in FIG.

[0108] like Figure 5 As shown in (a), the object 50 approaching the side sill S first abuts against the vehicle outer side surface of the side sill outer member S1. Figure 4 The upper wall 11 and the lower wall 13 of the lower side sill outer member S1 are arranged along the vehicle width direction ( Figure 4 There is a compressive load ( Figure 2 of load L).

[0109] like Figure 4 As shown, the portions corresponding to the upper wall 11 and the lower wall 13 of the side sill outer S1 formed of the metal composite material 10 transmit the side collision load to the side sill inner S2 while exerting their high rigidity.

[0110] Then, if Figure 5As shown in (b), the bulkhead 5 provided in the side sill inner member S2 in a manner corresponding to the floor cross member 8c begins to break and deform in response to the transmitted side collision load. The side sill outer member S1 having the reinforcement S3 on the inner side together with the bulkhead 5 causes the side sill inner member S2 to break and deform preferentially over the side sill outer member S1.

[0111] And, if Figure 5 As shown in (c), when the load input from the object 50 further develops and the side sill outer member S1 begins to bend and deform, the reaction force of the side sill outer member S1 increases along with the development of displacement. The increase in the reaction force of the side sill outer member S1 continues until the input load reaches the maximum bearing load of the side sill outer member S1.

[0112] According to the metal composite material 10 (see Figure 4 ) of the lower side member structure 20 (refer to Figure 4 ), when a side collision occurs, the lower side sill inner member S2 having the bulkhead 5 is broken and deformed, and then the lower side sill outer member S1 is deformed in stages. Figure 4 ) of the lower side member structure 20 (refer to Figure 4 ) can prevent the lower side sill outer member S1 from being excessively bent and deformed in the early stage of a side collision.

[0113] The side sill structure 20 can obtain a large energy absorption effect from the early stage to the late stage of a side collision.

[0114] In the metal composite material 10 , h0 in the equation (1) is expressed by the equation (3), and the thickness h3 of the adhesive layer 3 is equal to or greater than the thickness h1 of the thin steel plate 1 (h1 ≤ h3).

[0115] According to such a metal composite material 10, by setting the neutral axis Ax within the range of the thickness h3 of the adhesive layer 3, the stress applied to the bonding interface between the low-density plate material 2 and the thin steel plate 1 can be reduced. The metal composite material 10 can more effectively suppress the low-density plate material 2 from peeling off from the thin steel plate 1.

[0116] In addition, the thickness h3 of the adhesive layer 3 is preferably thinner than the thickness h2 of the low specific gravity plate 2 (h2>h3). Thus, the metal composite material 10 can more effectively suppress the low specific gravity plate 2 from peeling off from the thin steel plate 1.

[0117] In the metal composite material 10 , it is preferable that the thickness h3 of the adhesive layer 3 is larger than the thickness h1 of the thin steel plate 1 ( h1 < h3 ).

[0118] According to such a metal composite material 10 , by increasing the thickness of the adhesive layer 3 , the neutral axis Ax can be more reliably set within the adhesive layer 3 .

[0119] In addition, in the metal composite material 10 , the longitudinal elastic coefficient E3 of the adhesive layer 3 is smaller than the longitudinal elastic coefficient E1 of the thin steel plate 1 , and smaller than the longitudinal elastic coefficient E2 of the low specific gravity plate material 2 .

[0120] According to such a metal composite material 10 , the neutral axis Ax can be set more reliably within the adhesive layer 3 .

[0121] In addition, in the metal composite material 10, the low specific gravity plate material 2 is selected from an aluminum alloy plate (including a duralumin plate), a magnesium alloy plate, a CFRP plate, and a GFRP plate. According to such a metal composite material 10, the selection range of the low specific gravity plate material 2 is expanded, thereby, the selection range of the bending rigidity D of the metal composite material 10 that is preset is also expanded. Therefore, the range of vehicle body structures to which the metal composite material 10 is applicable is also expanded.

[0122] In addition, the metal composite material 10 can be suitably used for vehicle body structural parts.

[0123] According to such a metal composite material 10, a vehicle body structural component having excellent collision load transmission performance can be provided.

[0124] Specifically, the metal composite material 10 can be applied to, for example, a lower longitudinal beam structure, a roof side beam structure, a front pillar structure, a center pillar structure, a bumper structure, a door cross beam structure, etc. In addition, in addition to such vehicle structural parts, the metal composite material 10 can also be applied to mobile bodies such as aircraft and ships that are expected to achieve both improved rigidity and reduced weight.

[0125] As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, It can be implemented in various forms.

[0126] Example

[0127] Next, examples for verifying the effects of the metal composite material 10 according to the present embodiment will be described.

[0128] (Example 1)

[0129] In this embodiment, it is assumed that Figure 4 The metal composite material 10 in the side sill structure 20 shown in the figure is prepared as a thin steel plate 1 (see Figure 1 ) of cold-rolled high-tensile steel plate [material 980] (unit width b: 1, longitudinal elastic coefficient E1: 210GPa, Poisson's ratio ν1: 0.3, plate thickness h1: 1.0mm), and as a low-density plate 2 (reference Figure 1 ) of CFRP plate (unit width b: 1, longitudinal elastic coefficient E2: 70GPa, Poisson's ratio ν2: 0.3, plate thickness h2: 3.0mm).

[0130] Furthermore, the plate thickness h2 of the FRP plate is larger than the plate thickness h1 of the thin steel plate 1 .

[0131] Next, the cold-rolled high-tensile steel plate and the FRP plate are bonded together using an epoxy-based structural adhesive, thereby manufacturing the metal composite material 10 .

[0132] In order to make the neutral axis Ax (refer to Figure 1 ) is close to the bonding interface (h0=h3) between the thin steel plate 1 and the adhesive layer 3, and the adhesive layer 3 (refer to Figure 1 ) is set to satisfy the above formula (1). In addition, it is assumed that the bending rigidity of the metal composite material 10 of the lower side sill structure 20 is 1180000 Nm 2 , the thickness h3 of the adhesive layer 3 is 0.2 mm.

[0133] Next, in this embodiment, a test member composed of the metal composite material 10 was manufactured.

[0134] Figure 6 It is a schematic diagram of the test component TP.

[0135] like Figure 6 As shown, the test member TP is composed of four metal composite materials 10 of a predetermined size, and is formed by a square-section prism with a thin steel plate on the outside.

[0136] In this embodiment, a compression test was performed on the test member TP with a load L0 applied in the axial direction. In this compression test, the measurement range A of the thin steel plate in the vertical direction of the test member TP when the load L0 was applied was measured (refer to Figure 6 ), the axial strain of the CFRP plate obtained based on the strain gauge, and the maximum load (maximum reaction force) of the test member TP when the load L0 is applied in the axial direction.

[0137] In addition, the vertical displacement of the test member TP is measured by the digital image correlation method (DIC). In addition, in this embodiment, the vertical displacement and the axial strain obtained by the strain gauge are used to determine the FRP plate (low specific gravity plate 2 (refer to Figure 1 )) or adhesive layer 3 (refer to Figure 1 ) whether a fracture occurs in the metal composite material 10.

[0138] The maximum load (maximum reaction force) of the test member TP when the load L0 was applied in the axial direction was 506.6 kN. In addition, fracture in the metal composite material 10 occurred in the FRP plate (low-density plate material 2).

[0139] (Example 2)

[0140] In this embodiment, in order to make the neutral axis Ax (refer to Figure 1 ) is closer to the bonding interface between the thin steel plate 1 and the adhesive layer 3 (h0=h3) than in Example 1, and the adhesive layer 3 (refer to Figure 1 ) was set to a thickness h3 of 5.6 mm. A test member TP was prepared in the same manner as in Example 1, and a compression test was performed thereon.

[0141] As a result, the maximum load (maximum reaction force) of the test member TP when the load L0 was applied in the axial direction was 966.95 kN. In addition, fracture in the metal composite material 10 occurred in the FRP plate (low-density plate 2).

[0142] (Comparative Example 1)

[0143] In Comparative Example 1, a test piece TP was prepared and a compression test was conducted in the same manner as in Example 1 except that the plate thickness h2 of the FRP plate (low specific gravity plate 2) was set to 1.0 mm, which was the same as the plate thickness h1 of the thin steel plate 1: 1.0 mm.

[0144] As a result, the maximum load (maximum reaction force) of the test piece TP when the load L0 was applied in the axial direction was 186.93 kN. In addition, the fracture in the metal composite material 10 occurred in the adhesive layer 3 .

[0145] (Comparative Example 2)

[0146] In Comparative Example 2, a test member TP was produced using only a cold-rolled high-tensile steel sheet having a thickness of 1.0 mm constituting the metal composite material 10, and a compression test was performed thereon.

[0147] As a result, the maximum load (maximum reaction force) of the test member TP when the load L0 was applied in the axial direction was 74.36 kN.

[0148] (Evaluation results)

[0149] The maximum load of the metal composite material of Comparative Example 1 (186.93 kN) is approximately 2.5 times the maximum load of the cold-rolled high-tensile steel sheet alone of Comparative Example 2 (74.36 kN).

[0150] In contrast, the maximum load (506.6 kN) of the metal composite material 10 of Example 1 is 6.8 times the maximum load (74.36 kN) of the cold-rolled high-tensile steel plate alone of Comparative Example 2. In addition, the maximum load (966.95 kN) of the metal composite material 10 of Example 2 is 13.0 times the maximum load (74.36 kN) of the cold-rolled high-tensile steel plate alone of Comparative Example 2.

[0151] That is to say, the conventional thin steel plate did not fully exert the material strength due to the insufficient deflection (rigidity) of the plate, and deformed and buckled in the out-of-plane direction. In contrast, the metal composite material of the present invention is bonded to the thin steel plate via an adhesive layer through an FRP material with excellent rigidity, and the neutral axis is set at the adhesive layer, preferably, at the bonding interface between the thin steel plate and the adhesive layer. As a result, the metal composite material of the present invention can fully exert the strength of the thin steel plate and further improve the "rigidity" of the entire plate. In addition, the metal composite material can have an excellent strengthening effect without being damaged starting from the adhesive while including the adhesive layer, and it also helps to reduce the weight of the vehicle body necessary for collision safety.

Claims

1. A metal composite material comprising: a thin steel plate; a low-density plate having a smaller specific gravity and lower strength than the thin steel plate; and an adhesive layer which joins the thin steel plate and the low-density plate and has a strength lower than that of the thin steel plate and the low-density plate, wherein the metal composite material is characterized in that: The thickness of the thin steel plate and the thickness of the low specific gravity plate are set so as to satisfy the following equation (1) and the following equation (2) which represent the predetermined bending rigidity [D] of the metal composite material. 【Formula 1】 in, In formula (1), b is the width of the metal composite material, E1 is the longitudinal elastic coefficient of the thin steel plate, E2 is the longitudinal elastic coefficient of the low specific gravity plate, ν1 is the Poisson's ratio of the thin steel plate, ν2 is the Poisson's ratio of the low specific gravity plate, h1 is the plate thickness of the thin steel plate, h2 is the plate thickness of the low specific gravity plate, h3 is the thickness of the adhesive layer, h0 is the thickness of the adhesive layer from the bonding interface between the low specific gravity plate and the adhesive layer to the neutral axis, 【Formula 2】 h1<h2…(2) In the formula (2), h1 and h2 have the same meanings as h1 and h2 in the formula (1).

2. The metal composite material according to claim 1, characterized in that: The h0 is expressed by the following equation (3), and the thickness of the thin steel plate and the thickness of the adhesive layer are set so as to satisfy the following equation (4): 【Formula 3】 In formula (3), E1, E2, h0, h1, h2 and h3 have the same meanings as E1, E2, h0, h1, h2 and h3 in formula (1). 【Formula 4】 h1≤h3…(4) In the formula (4), h1 and h3 have the same meanings as h1 and h3 in the formula (1).

3. The metal composite material according to claim 1, characterized in that: The neutral axis of the metal composite material is set in the adhesive layer, or is set at the bonding interface between the adhesive layer and the thin steel plate or the low-specific-gravity plate.

4. The metal composite material according to claim 1, characterized in that: The thickness of the adhesive layer is greater than the thickness of the thin steel plate.

5. The metal composite material according to claim 1, characterized in that: The longitudinal elastic coefficient of the adhesive layer is smaller than the longitudinal elastic coefficient of the thin steel plate, and smaller than the longitudinal elastic coefficient of the low specific gravity plate.

6. The metal composite material according to claim 1, characterized in that: The low specific gravity plate is selected from aluminum alloy plates, magnesium alloy plates, CFRP plates and GFRP plates.

7. The metal composite material according to claim 1, characterized in that: The metal composite material is a vehicle body structural component.

8. A method for manufacturing a metal composite material, comprising: Process for preparing thin steel plates and low specific gravity plates, wherein: The low specific gravity plate has a smaller specific gravity and lower strength than the thin steel plate; and The step of bonding the thin steel plate and the low specific gravity plate through an adhesive layer having a strength lower than that of the thin steel plate and the low specific gravity plate, The method for producing the metal composite material is characterized in that: The joining process between the thin steel plate and the low-density plate is performed in such a way that the neutral axis of the metal composite material during bending deformation is set in the adhesive layer, or is set at the joining interface between the adhesive layer and the thin steel plate or between the adhesive layer and the low-density plate.

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