JP4422674B2 - Energy absorbing structural member - Google Patents

Description

  The present invention relates to a structural member used for an impact absorbing member for automobiles, and more particularly to a structural member capable of absorbing a large amount of energy with small deformation when subjected to bending deformation.

  As an example of the prior art of a structural member that undergoes bending deformation at the time of an automobile collision, an impact absorbing member used as a door / side beam material, a bumper beam material, or the like can be given. These frames installed as structural materials are extruded / press-molded from a single material, and the cross-sectional shape is closed and enlarged to increase the strength and rigidity, thereby absorbing energy at the time of collision.

  When the deformation mode at the time of a side collision of an automobile is shown by taking a center pillar which is a side structure material as an example, the center pillar is subjected to three-point bending so as to be bent with an upper side roof rail and a lower side sill as fulcrums. As shown in the schematic diagram of FIG. 2A and the graph of Comparative Example 1 in FIG. 7, in the deformation at this time, the structural material breaks immediately after the load reaches the maximum strength, and the load decreases at a stretch. The amount of energy absorption is small, and the amount of deformation of the vehicle body is large.

  In order to solve this problem, a bending member has been proposed in which an FRP material is provided on a tensile surface of an aluminum hollow shape (see, for example, Patent Document 1). By using a member that is easy to plastically deform on the compression side (upper surface on which load F is applied in FIG. 2) and using a high-strength lightweight member on the tension side (lower surface in FIG. 2), it is responsible for shock absorption on the compression side. This is a technique for realizing large energy absorption efficiency and small deformation by reducing the amount of deformation on the tension side.

JP-A-6-101732

  However, since the composite bending member uses aluminum that is easily plastically deformed on the compression side, the yield stress on the compression side is the dominant factor in the amount of energy absorption. That is, the high-strength FRP material on the tension side has a low contribution as an energy absorbing material, and there is a limit to the improvement in weight efficiency by using aluminum. Further, in the composite bending member, FRP and aluminum are bolt-bonded. As a result, stress concentration occurs in the bolt-joint portion with the addition of a load, and there is a risk of breaking. Even if an adhesive is used instead of the bolt, the upper limit of the strength of the entire beam material is determined by the strength of the adhesive. As described above, even if the amount of deformation is suppressed in the bending member, the energy absorption efficiency cannot be significantly improved as compared with the conventional single material bending member, and the risk of destruction from the bonded portion of aluminum and FRP occurs. There is.

  This invention is made | formed in view of the said situation, and it aims at providing the energy absorption structure member which can make a short deformation | transformation stroke and large energy absorption efficiency compatible.

The present invention is an energy absorbing structural member that absorbs energy by bending deformation, and the energy absorbing structural member is a solid material and a plate material, and isotropic or anisotropic with respect to material property values. The thickness of the layer or solid material and plate that occupies the whole surface in the thickness direction of the solid material and plate material with two or more kinds of members that have different maximum tensile / compression load and / or maximum tensile and compression displacement In a layer that occupies a part of the direction, at least one of the two or more members is an anisotropic material oriented in any one direction. The thin layer has a structure in which the orientation directions of the thin layers are stacked at an arbitrary angle and perpendicular to the longitudinal direction of the energy absorbing structural member .

  According to the energy absorbing structural member having the above configuration, since two or more types of members having different material property values are alternately arranged, when bending deformation is applied, in a member having relatively high strength A load is generated without being deformed, and a member having a relatively low strength is deformed to transmit the load. As a result, it is possible to expand the deformation and destruction area during bending deformation, and to realize energy absorption with high bending deformation with a short stroke.

Hereinafter, preferred embodiments of the energy absorbing structure member of the present invention will be described.
One embodiment of the energy absorbing structural member of the present invention is shown in FIG. FIG. 1 shows a plate-like long material composed of a member A and a member B. As shown in FIG. 1A, the material property values of the member A and the member A are different from each other in the longitudinal direction of the long material. The members B are alternately stacked. Moreover, as shown in FIG.1 (b), when cut in the cross section perpendicular | vertical to the longitudinal direction of a long material, it can also be set as the form by which the member A and the member B were alternately laminated | stacked on a part of long material. .

  As shown in FIG. 2 (a), the conventional structural member composed of one kind of homogeneous member is concentrated when the load F is applied, and breaks immediately after the load reaches the maximum strength. However, while the displacement amount (strain) S at that time is large, in the energy absorbing structural member of the present invention, as shown in FIG. Since the fracture occurs, the load is dispersed and the displacement amount S is small. That is, it is possible to provide a structural member that can achieve both a short deformation stroke and a large energy absorption efficiency.

  FIG. 3 shows another embodiment of the energy absorbing structure member of the present invention. As shown in FIGS. 3A and 3B, a connecting material C made of any material can be connected to the energy absorbing member of the present invention made up of member A and member B. Further, the energy absorbing structural member of the present invention is arranged in a hollow material D having a hollow cross section as shown in FIG. 3 (c), or from the energy absorbing structural member of the present invention as shown in FIG. 3 (d). It is also possible to produce a hollow material and to dispose an energy absorbing structural member therein.

  The materials constituting the member A and the member B are not particularly limited as long as they have different physical properties, i.e., a property of transmitting a load by deformation and a property of generating a large load. Examples of such substances include materials having isotropic or anisotropy, and specifically, fiber reinforced plastic (hereinafter abbreviated as FRP) and fiber reinforced metal (hereinafter abbreviated as FRM). Fiber reinforced materials such as iron, metals such as iron and aluminum, and various resins.

  As the member B having the property of transmitting a load by deformation, any material having isotropicity or anisotropy can be used as described above. In particular, when laminating materials having anisotropy, By arranging the anisotropic material so as to be oriented in an arbitrary direction, the member B having desired properties can be produced. For example, when the member B is laminated with the fiber direction of the FRP or FRM in which the fibers are provided in parallel and the longitudinal direction of the long material being oriented in the same direction, the fiber direction and the load direction are the same with respect to compression and tension in the longitudinal direction. Because it antagonizes, the load is large. On the other hand, when the member B is laminated with the fiber direction of FRP or FRM oriented at right angles to the longitudinal direction of the long material, the load is large because the fiber does not antagonize the load.

  Furthermore, in the present invention, a plurality of plate-like members having different fiber directions of FRP and FRM may be prepared, and these may be laminated to form member B. An example of such an energy absorbing structure member is shown in FIG. FIG. 4A is an example in which members B are provided by alternately laminating members perpendicular to the longitudinal direction of the long material and members perpendicular to the longitudinal direction of the long material, and FIG. This is an example in which members B are provided by alternately laminating members in which fibers are oriented at 45 ° and −45 ° with respect to the direction. In this way, the material physical properties of the member B can be changed.

  FIG. 5 shows a graph representing physical property values in tension with respect to the energy absorbing structural member shown in FIGS. 4A and 4B in a stress-displacement (strain) diagram. As is clear from the graph of FIG. 5, a member with 0 ° / 90 ° orientation has a direct relationship between strain and stress, and a strong stress is generated with respect to the applied strain. Even if the strain increases, the member does not generate a stress exceeding a certain level. That is, the former can be given strong and brittle characteristics, and the latter can be given weak and elongated characteristics.

Each role of the members having such different properties and effects when these properties are combined will be described below.
A beam material composed only of a strong and brittle material has a high tensile and compressive strength, and therefore can withstand a large bending moment and generate a high load. However, since the bending moment takes a peak value at the load portion, the maximum load generation portion is limited to the periphery of the load, and the deformation / fracture region is limited, so that energy absorption is small (see FIG. 2A). On the other hand, in the case of a weak and stretchable material, the bending moment value that can be withstood is lower than that of a strong and brittle material, but it deforms greatly under a low load, and therefore has a large deformation region.

  Therefore, by sandwiching a weak and stretchable material between beams made of a strong and brittle material, expansion of deformation and distribution of load load are realized, and the distribution of bending moment is changed from the load part to the periphery as in distributed load. It can be expanded toward the part (see FIG. 2B). Thereby, a large bending moment is applied to a strong and brittle material arranged other than the load portion, and a load can be generated.

Hereinafter, the energy absorbing structural member of the present invention will be described in more detail with reference to Examples and Comparative Examples.
[Example 1]
A member B (carbon fiber (trade name: HTA, manufactured by Toho Tenax Co., Ltd.)) and matrix (epoxy resin # 112) having a length of 600 mm and a width of 50 mm and having different material properties in a section of 95 mm in the longitudinal direction of the central portion The long members A1 to A3 in which a plurality of FRPs) are arranged are manufactured and connected to the top of the cross section by a connecting member, and the structural member of Example 1 shown in FIG. As shown to Fig.6 (a), in all A1-A3, the member B was provided in the half of the width direction of a long material. The width of the member B was 2 mm, and the arrangement interval between the adjacent members B in the same long material was 15 mm.

The orientation state of the FRP in the member B is in accordance with the method described in FIG. 4 and a plurality of FRP thin layers in which fibers are oriented in one direction are oriented at the following angle with the thickness direction of the long material being 0 °. And produced.
A1: (6 layers of 45 ° / 0 ° / 90 ° / 135 ° / 0 ° / 90 °) × 3 layers A2: (3 layers of 45 ° / 0 ° / 135 °) × 6 layers A3: (45 ° / Two layers at 135 °)

[Comparative Example 1]
Three homogeneous long members having a length of 600 mm and a width of 50 mm, which do not have an alternately arranged portion, are connected in a cross-sectional shape with a connecting member to produce a structural member of Comparative Example 1 shown in FIG. did.

  Using the structural members of Example 1 and Comparative Example 1, a three-point bending test result in which a forced displacement and a forced load were applied in the parallel direction was performed, and the result is shown in the graph of FIG. As is clear from FIG. 7, in the structural member of Comparative Example 1, a load is suddenly generated in proportion to the displacement in the initial stage, and the fracture occurs locally at a certain point and the load is reduced at a stroke. On the other hand, in the structural member of Example 1, since the locations with large displacement are dispersed, local breakage does not occur, and the load is not reduced as a whole. As a result, a large amount of energy absorption can be obtained.

[Comparative Example 2]
A tubular structural member (length 600 mm, cross section 50 mm × 50 mm) shown in FIG. 8A having a hollow rectangular cross section using a fiber reinforced material (member A) as a whole was produced.

[Comparative Example 3]
A long member made of the same material (member A) was placed inside the hollow cross-sectional structure of the structural member of Comparative Example 2, and a structural member shown in FIG. 8B having a hollow rectangular + simple vertical plate cross section was produced.

[Example 2]
Of the structural member (length 600 mm, cross section 50 mm × 50 mm) made of the same material (member A) as in Comparative Example 2 (length: 600 mm, cross section: 50 mm × 50 mm), the section of the top wall in FIG. A member B (FRP made of carbon fiber (trade name HTA, manufactured by Toho Tenax Co., Ltd.) and a matrix (epoxy resin # 112)) having a material property different from that of the material (member A) is arranged in the width direction of the long material. Then, the members A and B are alternately arranged in the longitudinal direction, and the members B are alternately arranged in the longitudinal direction at half the width in the width direction of the long material of the side wall. The structural member which has was produced. The width in the longitudinal direction of the member B was 2 mm, and the arrangement interval between the adjacent members B was 15 mm.

  The orientation state of the FRP in the member B is the same as the method described in FIG. 4B. The FRP thin layer in which the fibers are oriented in one direction is 45 ° and 135 ° with the thickness direction of the long material being 0 °. A plurality of layers were alternately stacked.

[Example 3]
In FIG. 8D, a long material having a structure in which the members A and B are alternately arranged is arranged inside the hollow cross-sectional structure of the structural member of the second embodiment, and the cross-sectional shape is a hollow rectangle + alternately arranged vertical plate cross section. The structural member shown was made. This long member B is made of an FRP thin layer in which fibers are oriented in one direction, as in the method described in FIG. 4A. A plurality of layers were alternately stacked.

  These structural members were subjected to a three-point bending test in which a forced displacement and a forced load were applied in a direction parallel to the long material, and the results are shown in FIG. As is clear from FIG. 9, in the structural members of Comparative Example 2 and Comparative Example 3, in the initial stage, a load was suddenly generated in proportion to the displacement, and the load was reduced at a stretch due to local breakage at the load point. To do. On the other hand, in the structural members of Example 2 and Example 3, since the locations where the displacement is large are dispersed, the distribution of the displacement (strain) is widened in the longitudinal direction, and the strain is dispersed to cause local fracture. An area where the load is maintained without being generated is generated, and the amount of energy absorption is increased. In particular, in Example 3, since the long material is disposed inside the hollow structure, the strain is further dispersed in the longitudinal direction, and as a result, a very large amount of energy absorption can be obtained.

  Further, impact tests were performed on the structural members of Examples 2 and 3 and Comparative Examples 2 and 3, and the measurement results of energy absorption efficiency are shown in FIG. The vertical axis in FIG. 10 indicates the amount of energy absorbed per unit weight. As shown in FIG. 10, compared with the conventional structural member produced from a homogeneous material, the structural member of Example 2 having the alternate arrangement structure of the member A and the member B has an energy absorption amount of about twice, It can be seen that the structural member of Example 3 to which a vertical plate is added has an absorption amount of about three times.

  Since the energy absorbing structure member of the present invention has a characteristic that the amount of energy absorption is large and the amount of deformation is small, it can be applied as an impact absorbing member for automobiles.

It is a perspective view which shows the embodiment of the energy absorption structure member of this invention. (A) is a schematic diagram which shows the load F and the displacement amount S at the time of fracture | rupture of the conventional structural member, (b) is a schematic diagram which shows the load F and the displacement amount S at the time of fracture | rupture of this invention. It is. It is a perspective view which shows the embodiment of the energy absorption structure member of this invention. (A) is a perspective view which shows the energy absorption structure member which laminated | stacked the material which the fiber in a fiber reinforced material orientated 0 degree / 90 degree, (b) laminated | stacked the material which the fiber orientated 45 degree / -45 degree. It is a perspective view which shows the energy absorption structure member which was made. It is a graph which shows the relationship between the displacement (strain) and the stress in the tensile test of a 0 degree / 90 degree orientation member and a 45 degree / -45 degree orientation member. It is a perspective view which shows the structural member in an Example and an Example. It is a graph which shows the relationship between the displacement amount (strain) and a load in an Example and a comparative example. It is a perspective view which shows the structural member in an Example and a comparative example. It is a graph which shows the relationship between the displacement amount (strain) of a structural member and a load in an Example and a comparative example. It is a graph which shows the comparison result of the energy absorption efficiency of the structural member in an Example and a comparative example.

Explanation of symbols

A Member A
B Member B
C Connecting material D Hollow material F Load S Displacement (strain)

Claims (10)

An energy absorbing structure member for energy absorption by performing bending deformation, the energy absorbing structural member is a solid plate material,
Two or more members to the difference in isotropic or comprising anisotropic and tension and compression maximum load and / or tensile and compression maximum displacement with respect to material property value, the thickness direction of the solid plate at layer or the solid occupies the entire surface of the layer occupying a portion of the surface in the thickness direction of the sheet material, arranged alternately with respect to the longitudinal direction of the solid plate member,
At least one of the two or more types of members is formed by laminating a thin layer of anisotropic material oriented in any one direction perpendicular to the longitudinal direction of the energy absorbing structure member with each other having an arbitrary orientation direction. energy absorbing structural member, characterized in that the the structure. The energy absorbing structural member is tension / compressed by providing a difference in the thickness of the energy absorbing structural member in the longitudinal direction or the thickness of the energy absorbing structural member in a layer where two or more kinds of members are alternately arranged. The energy absorbing structural member according to claim 1 , wherein a difference is provided in the maximum load and / or the maximum tensile / compressive displacement. At least one of the two or more types of members includes a first thin layer oriented parallel to the longitudinal direction of the energy absorbing structural member, and a second thin layer oriented perpendicular to the longitudinal direction of the energy absorbing structural member, energy absorbing structure according to claim 1 or 2, characterized in that the a structure of alternately laminated. At least one of the two or more types of members is oriented at -45 ° C with respect to the first thin layer oriented at 45 ° C with respect to the longitudinal direction of the energy absorbing structural member and with respect to the longitudinal direction of the energy absorbing structural member. energy absorbing structure according to claim 1 or 2, characterized in that a second thin layer is a structure formed by alternately laminating was. One of the two or more types of members includes a first thin layer oriented parallel to the longitudinal direction of the energy absorbing structural member, and a second thin layer oriented perpendicular to the longitudinal direction of the energy absorbing structural member. The other of the two or more members is a first thin layer oriented at 45 ° C. with respect to the longitudinal direction of the energy absorbing structural member, and the longitudinal direction of the energy absorbing structural member. energy absorbing structure according to claim 1 or 2, characterized in that a structure formed by alternately laminating a second thin layer oriented to -45 ° C. for.   The energy absorption according to any one of claims 1 to 5, wherein the two or more types of members are selected from the group consisting of fiber reinforced plastic, fiber reinforced metal, iron, aluminum, and resin. Structural member. It is a solid material of a rectangular parallelepiped, The energy absorption structure member in any one of Claims 1-6 characterized by the above-mentioned. An energy absorbing structure member having a structure in which a plurality of energy absorbing structure members according to any one of claims 1 to 7 are joined using a connecting material. The energy absorption structure member according to any one of claims 1 to 6 , wherein the energy absorption structure member is a hollow material having a substantially square shape in a cross section perpendicular to the longitudinal direction. The energy absorbing structure member according to claim 9 , wherein a hollow connecting member having a rectangular shape is provided by providing a rectangular connecting member inside the hollow member having a substantially mouth-shaped cross section.

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