JP3362445B2 - Energy absorbing member - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an energy absorbing member, and more particularly to the structure of an energy absorbing member made of a composite material of resin and reinforcing fibers having a plurality of reinforcing fiber layers.

[0002]

2. Description of the Related Art For example, an energy absorbing member that absorbs impact energy is used for a seat around an aircraft, a seat around an automobile, a bumper, and various structural members (JP-A-60-109630). 62-17
No. 438, etc.). In addition to the ability to absorb impact energy well, this energy absorbing member is generally lightweight,
Since high rigidity is required, a composite material of a resin and reinforcing fibers, so-called fiber reinforced plastic (hereinafter sometimes referred to as FRP), especially carbon fiber reinforced plastic (hereinafter also referred to as CFRP) There is) is said to be suitable. In such an energy absorbing member, an energy absorbing mechanism may be considered in which local destruction is caused from a certain portion of the energy absorbing member, for example, a member end portion, and the energy is absorbed by utilizing the local destruction.

[0003]

However, the conventional energy absorbing member made of a composite material of resin and reinforcing fiber has a surface which is still insufficient for efficiently absorbing energy. In the case of destroying and absorbing energy, the strength of the member is often not effectively utilized for energy absorption over the entire thickness direction, and the fact is that it has not been put to practical use sufficiently.

The present invention provides a structure of an energy absorbing member that can effectively utilize the strength of the member over the entire thickness direction of the member for absorbing energy, and can efficiently and highly absorb energy, reliability and practicality. The aim is to realize a high energy absorption member.

[0005]

The energy absorbing member of the present invention for this purpose is an energy absorbing member made of a composite material of resin and reinforcing fibers, having at least three reinforcing fiber layers, and having an outer surface. The reinforcing fiber layer located is thinner than the reinforcing fiber layer located inside.

The energy absorbing member of the present invention has a structure in which a plurality of prepregs in which reinforcing fibers are impregnated with a resin are laminated to have at least three reinforcing fiber layers. The laminated structure of the reinforcing fiber layer is preferably 3 layers or more, and more preferably 4 layers or more.

In the thickness direction of the energy absorbing member, the thickness of the reinforcing fiber layer located outside is made thinner than the thickness of the reinforcing fiber layer located inside. When the number of laminated reinforcing fiber layers is large, the thickness of the reinforcing fiber layers at the center of the member in the thickness direction or both sides in the center of the thickness direction should be maximized, and the thickness of the outermost reinforcing fiber layers on both sides should be minimized. Then, it is preferable that the thickness gradually decreases from the central portion to the outer side.

For example, as shown in FIG. 1, there is a cylindrical energy absorbing member 41 made of a composite material of resin and reinforcing fibers, which has six reinforcing fiber layers. The thickness of the reinforcing fiber layers 42a, 42b on the inner side in the member thickness direction is larger than the thickness of the outer reinforcing fiber layers 44a, 44b, and the thickness of the intermediate reinforcing fiber layers 43a, 43b is the intermediate size between them. Has become. That is, the inner side is thicker and the outer side is thinner.

In the energy absorbing member of the present invention having such a structure, for example, when absorbing the impact energy in the compression direction, as shown in the enlarged view of the member 41 of FIG. When the member 41 is destroyed, the member 41 tries to open at the end of the member 41 so that the member 41 bends so as to tear in the thickness direction. When the expanded both sides are bent, the member 41 has a laminated structure of the reinforcing fiber layers, so that delamination occurs to some extent at the laminated boundary portion. Therefore, the laminated reinforcing fiber layers 42a, 43a, 44a and 42b, 43b, 4
Bending stress similar to that when each layer is bent in a single layer state is generated in each of 4b. This bending stress is a tensile stress on the outer surface side (side with a large radius of curvature) and a compressive stress on the inner surface side (side with a small radius of curvature) of the bent layer.

In bending the end portions of the member as shown in FIG. 2, the radius of curvature increases toward the inner layers 42a and 42b,
The radius of curvature becomes smaller toward the outer layers 44a and 44b. Now suppose each layer 42a, 43a, 44a and 42b, 43
Assuming that the thicknesses of b and 44b are the same, the tensile stress on the bending outer surface side (side where the radius of curvature increases) of the inner layers 42a and 42b having a large radius of curvature , Smaller than those of the outer layers 43a, 44a and 43b, 44b having a smaller radius of curvature. Therefore, when bending is advanced in such a state, the expanded member will be destroyed and the outermost layer 44 will not be destroyed.
It occurs on the side of a and 44b, and at that time, the layers 43a and 43b and the innermost layers 42a and 42b inside thereof are not broken. When the energy is absorbed by such a destruction mechanism, the layers 42a, 42b, 43 are eventually
The strength possessed by a and 43b themselves will not be utilized to the maximum extent in energy absorption.

In the energy absorbing member of the present invention,
Since the thickness of the inner layers 42a and 42b is increased, the difference in the radius of curvature between the bending outer surface side of the layers 42a and 42b itself and the bending inner surface side becomes large, and the tensile force generated on the bending outer surface side of the layers 42a and 42b itself. The stress and the compressive stress generated on the inner side of the bending are increased. If this stress generation state is adjusted,
That is, if the thicknesses of the innermost layers 42a and 42b are appropriately set, the outermost layers 44a and 44b can be destroyed by bending, and at the same time, the innermost layers 42a and 42b can be destroyed. Similarly, for the intermediate layers 43a and 43b, the outermost layers 44a and 44b or the innermost layers 42a and 4b.
2b can be destroyed at the same time. As a result, all layers can be destroyed substantially simultaneously.

The fact that all the layers are destroyed at substantially the same time means that the strength of each layer is maximized when the member is destroyed, and all the strength of each layer is effective in absorbing energy. Will be used.

Further, since the destruction of all layers occurs at substantially the same time and the strength of all layers is maximized, the amount of energy that can be absorbed by the energy absorbing member as a whole is maximized.

In order to further promote efficient energy absorption as described above, the reinforcing fiber layers on both sides of the central portion in the member thickness direction are symmetrical with respect to the reinforcing fiber layers in the central portion in the member thickness direction. It is preferable to be laminated on. By adopting such a symmetrical laminated structure, when the member breaks so as to tear from the center in the thickness direction to both sides, the strength possessed by both sides is maximized efficiently and a higher energy absorption amount is obtained. To be

The kind of the reinforcing fiber in the composite material constituting the energy absorbing member of the present invention is not particularly limited, and examples thereof include carbon fiber, glass fiber, aromatic polyamide fiber, alumina fiber, silicon carbide fiber, boron fiber and the like. You can choose from.

The arrangement of these reinforcing fibers is different from that of the energy absorbing member 4 unless a special combination arrangement is performed.
0 with respect to the energy absorption axis 45 of 1 (shown in FIG. 1)
It may be performed in the range of ± 60 °. If the angle is too large, the reinforcing fibers are not effectively used for absorbing the impact energy acting in the compression direction.

Further, each reinforcing fiber layer may be a single layer, or may have a laminated structure (for example, one having ± 25 ° layers,
A layer having ± 25 ° layers and ± 15 ° layers). Further, the form of the reinforcing fiber is not particularly limited, and a woven fabric of the reinforcing fiber can be used in addition to ordinary filaments.

The resin forming the matrix of the composite material of the present invention is not particularly limited, and examples thereof include epoxy resin and
Unsaturated polyester resin, polyvinyl ester resin, phenol resin, guanamine resin, polyimide resin such as bismaleimide / triazine resin, furan resin, polyurethane resin, polydiallyl phthalate resin, and amino resin such as melanin resin and urea resin. A thermosetting resin may be used. Also, nylon 6, nylon 66,
Polyamides such as nylon 11, nylon 610 and nylon 612, copolyamides of these polyamides, polyesters such as polyethylene terephthalate and polybutylene terephthalate, copolyesters of these polyesters, and further polycarbonates, polyamide imides and polyphenylene sulfides. , Polyphenylene oxide, polysulfone, polyether sulfone, polyether ether ketone, polyether imide, polyolefin, and the like, and thermoplastic elastomers typified by polyester elastomer, polyamide elastomer and the like. Furthermore, as the resin satisfying the above range, acrylic rubber,
It is also possible to use rubber such as acrylonitrile butadiene rubber, urethane rubber, silicone rubber, styrene butadiene rubber, and fluororubber. Furthermore, it is also possible to use a resin obtained by blending a plurality of the above-mentioned thermosetting resins, thermoplastic resins, and rubber.

When the reinforcing fiber is made of carbon fiber, the surface functional group amount (O / C), which is the atomic number ratio of oxygen (O) and carbon (C) on the surface of the reinforcing fiber, is 0.08 or more. Is preferred. When the amount of surface functional groups (O / C) is 0.08 or more, the activated O enhances the adhesiveness of the surface of the reinforcing fiber, and the adhesive strength between the resin and the reinforcing fiber is increased to make it more difficult to break. Therefore, the composite material as a whole can exhibit extremely high rigidity and energy absorption capability. If the amount of surface functional groups (O / C) is less than 0.08, the adhesiveness between the resin and the reinforcing fiber becomes insufficient, and peeling or breakage easily occurs at the interface between the resin and the reinforcing fiber during energy absorption. , The energy absorption capacity is reduced accordingly.

The shape of the energy absorbing member made of the composite material of the present invention is not particularly limited, and may be cylindrical, columnar, or
Various shapes such as a plate shape can be adopted. Representative shapes or applicable shapes are illustrated in FIGS. 3 to 12.

As a typical shape of the energy absorbing member, first, a cylindrical shape can be mentioned. The most typical shape as a cylindrical shape is a cylinder 1 as shown in FIG. The direction of the arrow in the figure is the compressive load acting direction as impact energy. Further, as shown in FIG. 4, a cylinder 2 in which the top of the cylinder is formed in a conical shape or a spherical shape can also be applied. Further, although not shown, a prism, a cone, a pyramid, a truncated cone, a truncated pyramid, or a cylinder having an elliptical cross section, and further, as shown in FIG. A tubular shape 4 such as a tube) can also be adopted.

The shape is not limited to the cylindrical shape, but may be a columnar shape. For example, a columnar shape or a prismatic shape can be mentioned.

Further, it is possible to adopt a plate shape. For example, a corrugated plate-shaped member can be used as an energy absorbing member because it is strong against buckling. Also,
As shown in FIG. 6, for example, a cross section T having a rib 5 is provided.
The shape 6 may be a V shape, or may be a shape 7 having a U-shaped cross section as shown in FIG. 7. In the shape 7 having a U-shaped cross section shown in FIG. 7, the lid member 8 can be provided as shown by a two-dot chain line. Further, as shown in FIG. 8, a cross-shaped cross section 9 may be used.

Furthermore, it is also possible to adopt a structure in which members of various shapes are combined. For example, FIG. 9 and FIG.
As shown in FIG. 0, small elongated cylinders 12 and 13 are put in a large cylinder 10 and a large truncated cone 11 and are made of a composite material, so that an energy absorbing member that is less likely to buckle can be obtained. it can.

Further, the energy absorbing member may be composed of one member, or may be composed of a plurality of members stacked or combined. For example, in FIG.
As shown in FIG. 12, the energy absorbing members 16 and 17 may be configured by vertically stacking members 14, 15a, 15b and 15c made of a composite material having the same or similar shapes. In the configuration of FIG. 12, each member may be alternately laminated inside and outside.

In the energy absorbing member as described above, it is desirable to form a trigger shape for sequentially destroying the energy absorbing member from the end, and this trigger is a pressing member for pressing the energy absorbing member. It may be provided on the side.

[Method of measuring characteristics and method of evaluating effects]
The method of measuring the characteristics used in the description of the present invention will be described below. (1) Tensile Strength and Tensile Modulus of Fiber Measured according to the resin-impregnated strand test method specified in JIS-R7601. The resin formulation and curing conditions used in the test are shown below. Resin Formulation: "Bakelite" ERL-4221 100 parts of 3 boron trifluoride monoethylamine (BF ₃ · MEA) ₃ parts acetone 4 parts Curing conditions: 130 ° C., 30 minutes

(2) Surface functional group amount (O / C) It was determined by the following procedure by X-ray photoelectron spectroscopy. First, carbon fiber (bundle) from which sizing agents have been removed with a solvent
After cutting and arranging them on a copper sample support, the photoelectron escape angle was set to 90 °, and MgKα1, X-ray source was used.
2 is used and the sample chamber is kept at 1 × 10 ⁻⁸ Torr. The kinetic energy value (KE) of the main peak of C _1S is set to 969 eV as a correction of the peak associated with charging during measurement. The C _1S peak area was calculated as K. E. As 958-97
It is obtained by drawing a linear baseline in the range of 2 eV. The O _1S peak area was measured by K.K. E. As 714-726
It is determined by drawing a straight baseline in the range of eV. Here, the amount of surface functional groups (O / C) is calculated as an atomic number ratio from the ratio of the O _1S peak area and the C _1S peak area using a sensitivity correction value specific to the apparatus. The inventors of the present invention used a model ESCA-75 manufactured by Shimadzu Corporation.
0 was used to measure the ratio of the O _1S peak area to the C _1S peak area, and the ratio was divided by the sensitivity correction value of 2.85 to obtain the surface functional group amount (O / C).

[0029]

As described above, according to the energy absorbing member of the present invention, the energy absorbing member has at least three reinforcing fiber layers, and the reinforcing fiber layer is thinner on the outer side in the thickness direction. By arranging a thicker reinforcing fiber layer on the inside so that when the member ruptures, the inner and outer layers rupture at substantially the same time, so that the strength of the member is absorbed over the entire thickness direction of the member. Therefore, the energy absorption ability can be improved, the thickness and weight can be reduced, and a highly practical energy absorption member that can be suitably used in various fields can be realized.

[Brief description of drawings]

FIG. 1 is a partial vertical sectional view of an energy absorbing member according to the present invention.

FIG. 2 is an enlarged partial vertical sectional view of the member of FIG.

FIG. 3 is a perspective view showing an example of the shape of the energy absorbing member of the present invention.

FIG. 4 is a perspective view showing another example of the shape of the energy absorbing member of the present invention.

FIG. 5 is a perspective view showing still another example of the shape of the energy absorbing member of the present invention.

FIG. 6 is a perspective view showing still another example of the shape of the energy absorbing member of the present invention.

FIG. 7 is a perspective view showing still another example of the shape of the energy absorbing member of the present invention.

FIG. 8 is a perspective view showing still another example of the shape of the energy absorbing member of the present invention.

FIG. 9 is a perspective view showing another structural example of the energy absorbing member of the present invention.

FIG. 10 is a perspective view showing still another structural example of the energy absorbing member of the present invention.

FIG. 11 is a vertical sectional view showing still another structural example of the energy absorbing member of the present invention.

FIG. 12 is a vertical sectional view showing still another structural example of the energy absorbing member of the present invention.

[Explanation of symbols]

1, 2 Cylindrical energy absorbing member 3 Flange portion 4 Cylindrical energy absorbing member having a flange portion 5 Rib 6 Energy absorbing member 7 having T-shaped cross section 7 Energy absorbing member 8 having U-shaped cross section 8 Lid member 9 Cross section Cross-shaped energy absorption member 10 Cylindrical energy absorption member 11 Frustum-shaped energy absorption members 12, 13 Elongated members 14, 15a, 15b, 15c Energy absorption member members 16, 17 Combination energy absorption Member 41 Energy absorbing members 42a, 42b Innermost layer reinforcing fiber layers 43a, 43b Intermediate layer reinforcing fiber layers 44a, 44b Outermost layer reinforcing fiber layer 45 Energy absorption axis

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Claims (4)

(57) [Claims] 1. Having at least three reinforcing fiber layers,
An energy absorbing member made of a composite material of resin and reinforcing fibers, characterized in that a thickness of a reinforcing fiber layer located outside is smaller than a thickness of a reinforcing fiber layer located inside. 2. The energy absorbing member according to claim 1, wherein the reinforcing fiber layer is thickest in the central portion in the thickness direction of the member, and the reinforcing fiber layer is successively thinner toward the outer side in the thickness direction of the member. 3. The reinforcing fiber layer located on both sides of the reinforcing fiber layer at the central portion in the thickness direction of the member is symmetrical with respect to the reinforcing fiber layer at the central portion in the thickness direction. Energy absorbing member. 4. The energy absorbing member according to claim 1, 2 or 3, wherein the reinforcing fibers are arranged in a direction within a range of 0 ° ± 60 ° with respect to the energy absorbing axis direction.