JP3360870B2 - 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 in particular, it is made of a composite material of resin and carbon fiber,
The present invention relates to the structure of an impact energy absorbing member.

[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.

[0003]

However, the conventional energy absorbing member made of a composite material of resin and carbon fiber is still insufficient in practical use because of its insufficient energy absorbing ability. It's a reality.

It is an object of the present invention to provide an energy absorbing member capable of exhibiting a sufficiently high energy absorbing ability by causing the carbon fiber to perform a special operation during energy absorption.

[0005]

The energy absorbing member according to claim 1 of the present invention which meets this object is made of a composite material of resin and carbon fiber, and has an energy release rate G of the resin.
_IC is 100 J / m ² or more, the tensile strength of the carbon fiber is 450 kgf / mm ² or more, and the surface functional group amount (O / O) is the atomic number ratio of oxygen (O) to carbon (C) on the surface. C) is less than 0.08.

The energy absorbing member according to claim 2 of the present invention is made of a composite material of resin and carbon fiber, the breaking elongation of the resin is 30% or more, and the tensile strength of the carbon fiber is Is 450 kgf / mm ² or more, and the surface functional group amount (O / C), which is the atomic number ratio of oxygen (O) to carbon (C) on the surface, is less than 0.08.

Further, in each of the energy absorbing members of the present invention, it is preferable that the surface roughness of the carbon fiber is 1.0 or more and less than 1.08.

In each of the above energy absorbing members, the reinforcing fiber is made of carbon fiber, and the amount of surface functional group (O), which is the atomic number ratio of oxygen (O) and carbon (C) on the surface of the carbon fiber.
/ C) is less than 0.08. This surface functional group amount (O
/ C) is the atomic ratio of oxygen (O) to carbon (C) on the carbon fiber surface, and indicates the ratio of activated O on the carbon fiber surface, and the adhesiveness with the resin on the carbon fiber surface. Is an index of. That is, if the surface functional group amount (O / C) is high, the adhesiveness of the carbon fiber surface is high,
When the amount of surface functional groups (O / C) is low, the adhesiveness of the carbon fiber surface is low. In the present invention, the surface functional group amount (O / C) is set to 0.
When it is less than 08, the adhesiveness of the carbon fiber surface with the resin can be suppressed low.

In the energy absorbing member, for example, a trigger is devised so that destruction occurs from the end portion of the member at the time of energy absorption, and impact energy or the like is absorbed in the process of destruction of the end portion. In such energy absorption, if the adhesiveness between the carbon fiber surface and the resin is suppressed as described above, the carbon fiber and the resin are peeled off at the broken portion when the end of the member is broken, and the peeled carbon fibers are separated from each other. Are intricately intertwined. For example, as shown in FIG. 1, an impact load P is applied to the end face 42 of the energy absorbing member 41 made of a cylindrical composite material at the central portion in the member thickness direction, and the member end is broken so as to open in the thickness direction. Then, in the space formed by the destruction, the carbon fibers 43 separated from the resin are intricately entangled so as to straddle the fractured portions opened on both sides. At this time, the peeled carbon fiber 43 is not yet broken, or even if it is broken, it remains in only a part of the fiber, or the broken portion opens on both sides while cutting the carbon fiber 43, so The carbon fiber 43 thus formed causes a great resistance. Particularly, when the broken portion opens while cutting the carbon fiber 43 in the pulling direction, an extremely large resistance occurs. Since this resistance acts to suppress the destruction of the end of the member, the end breaking load or end breaking energy of the energy absorbing member is greatly increased, and the energy absorbing capacity of the energy absorbing member is correspondingly increased. To be enhanced.

In the energy absorbing member of the present invention, the tensile strength of the carbon fiber is 450 kgf / m while maintaining the above-mentioned characteristics regarding the adhesiveness between the carbon fiber and the resin.
m ² or more, and the energy release rate G _IC of the resin is 100 J / m ² or more.

Carbon fiber has a tensile strength of 450 kgf / mm
^{By setting the} number to be ² or more, when the carbon fibers straddle the two fracture ends in a bridge shape as shown in FIG. 1, the carbon fibers are hard to be cut, and more energy is required for cutting, A high level of energy absorption capacity is achieved.

Further, the energy release rate G _{IC of the} resin is 10
When it is set to 0 J / m ² or more, the resin itself is not easily broken, and the energy absorption performance of the composite material as a whole is enhanced. This energy release rate G _IC is
It is obtained as shown in the measuring method described later and shows the energy release rate when the resin itself is peeled off. When the energy release rate G _IC is less than 100 J / m ² , the resin itself is relatively easily peeled off,
It becomes difficult to achieve high energy absorption capacity. In the present invention, by using a composite material of a resin having this high energy release rate G _IC and a carbon fiber having a high tensile strength in which the adhesiveness between the resin is suppressed as described above, excellent energy absorption is achieved. The ability can be demonstrated and a high amount of specific absorbed energy can be achieved.

In the energy absorbing member according to another aspect of the present invention, the breaking elongation of the resin is 30% or more and the tensile strength of the carbon fiber is 450 kgf / mm ² .
The amount of surface functional groups (O / C) is less than 0.08. By using a composite material of a resin having a high elongation at break and a carbon fiber having a high tensile strength, the strength and toughness of the composite material itself are increased, and the energy absorption capacity is improved. If the breaking elongation of the resin is less than 30%, it becomes difficult to achieve a high energy absorption capacity. In the energy absorbing member according to the present invention, a high toughness resin having a high elongation at break and a composite material of carbon fiber having high strength and appropriately suppressing the adhesiveness with the resin are excellent, The energy absorption capability can be demonstrated, and a high specific absorbed energy amount can be achieved. Then, by setting the amount of surface functional groups (O / C) of the carbon fiber to less than 0.08, the adhesiveness between the carbon fiber and the resin can be appropriately suppressed, and the end portion of the member as shown in FIG. A breakage state is easily obtained, an extremely large resistance is obtained as described above, and the energy absorbing capacity of the energy absorbing member is enhanced.

In the energy absorbing member according to the present invention as described above, the surface undulation degree of the carbon fiber is preferably 1.0 or more and less than 1.08. When the surface undulation degree of the carbon fiber is 1.08 or more, the so-called anchor effect due to the undulation of the surface becomes large, the adhesiveness between the carbon fiber and the resin becomes high, and the destruction as shown in FIG. 1 occurs. In that case, the carbon fibers are not easily separated from the resin, and it becomes difficult to form carbon fibers that extend between the fractured portions. As a result, as described above, the resistance due to the fiber bridge cannot be expected, and the improvement of the energy absorption capacity cannot be expected. The surface roughness of the carbon fiber is 1.0 or more.
By setting it to be less than 08, the adhesiveness of the carbon fiber to the resin can be appropriately suppressed, and a large amount of energy can be absorbed by the resistance due to the fiber bridge when the member is broken.

Examples of the resin having a breaking elongation of 30% or more include polyamides such as nylon 6, nylon 66, nylon 11, nylon 610 and nylon 612, copolyamides of these polyamides, polyethylene terephthalate and polybutylene. Polyesters such as terephthalate, or copolyesters of these polyesters, and further polycarbonates, polyamideimides, polyphenylene sulfides, polyphenylene oxides, polysulfones, polyether sulfones, polyether ether ketones, polyetherimides, polyolefins, etc., and polyester elastomers. , Thermoplastic elastomers typified by polyamide elastomers, and the like.

In the energy absorbing member of the present invention,
The arrangement of the carbon fibers in the composite material may be within the range of 0 ° to ± 60 ° with respect to the axis of the energy absorbing member in the compression direction, except when a special combination arrangement is performed. When the angle is too large, the carbon fibers are not effectively used for absorbing the impact energy acting in the compression direction. Further, the form of the carbon fiber is not particularly limited, and in addition to ordinary filaments, carbon fiber woven fabric can be used.

The shape of the energy absorbing member made of the composite material of the present invention is not particularly limited, and various shapes such as a cylindrical shape, a columnar shape and a plate shape can be adopted. Representative shapes or applicable shapes are illustrated in FIGS. 2 to 11.

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. 3, a cylinder 2 in which the top of the cylinder is formed into 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. 5, for example, a cross section T having ribs 5 is provided.
The shape 6 may be a V shape, or a shape 7 having a U-shaped cross section as shown in FIG. In the shape 7 having a U-shaped cross section shown in FIG. 6, the lid member 8 can be provided as shown by a chain double-dashed line. Further, as shown in FIG. 7, 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, FIGS.
As shown in FIG. 3, by inserting small elongated cylinders 12 and 13 in a large cylinder 10 and a large truncated cone 11 and composing these with a composite material, an energy absorbing member that is less likely to buckle can be obtained. .

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. 11, 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. 11, 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.

[Characteristic Measuring Method] The characteristic measuring method used in the description of the present invention will be described below. (1) Method of measuring tensile elongation at break of resin Measured according to ASTM-D-638.

(2) Tensile strength 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

(3) Surface Roughness The composite material is cut perpendicularly to the fiber direction, and the cut surface is mirror-polished by metal phase polishing. Here, the cross-sectional shape of the single fiber perpendicular to the polishing surface was measured by a scanning electron microscope (JSM manufactured by JSM Co., Ltd.).
-T300 type) is used to photograph a backscattered electron composition image at an accelerating voltage of 15 kV and a photographing magnification of 10,000 times on a film. The backscattered electron composition image photograph thus obtained was further stretched to 2 times at the time of printing, that is, the magnification was 2 in total.
It is taken as a photograph for surface undulation analysis with a magnification of 0000. Here, from the photograph for surface undulation analysis, the area S (m
m ² ) and the outer peripheral length L (mm) are measured. The surface undulation degree is obtained according to the following formula as a ratio of the above L and the outer peripheral length of a virtual perfect circle having the same S. Surface relief = L · (πS) ^−1/2 / 2 L is measured at 20000 times. After accurately sticking a non-stretchable cotton thread on the outer periphery of the single fiber cross-sectional image in the photograph, Can be removed and the length of the straight line can be measured. Further, S was measured by placing a trace paper of known weight per unit area on a photograph printed at 20000 times, accurately tracing the outer periphery of the single fiber cross-sectional image, and accurately cutting the trace line. The weight can be converted from the weight of the cut single fiber cross-sectional image and the weight per unit area of the trace paper. The measurement is carried out on 10 monofilaments, and the average value is taken as the surface relief. There is no limitation on the method of measuring L and S as long as it can be accurately measured, and an image analyzer can be used in addition to the above method.

(4) Amount of surface functional group (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).

(5) Energy release rate of resin G _IC compact test (CT test) Standard: ASTM-E-39
It measured based on 9.

(6) There is no standard for specific absorbed energy amount or standardized method. As shown in FIG. 12, when a compressive load P is applied to the energy absorbing member 21 via the pressing member 22 to destroy the member 21, generally a load-displacement (displacement of the pressing member) diagram as shown in FIG. Is obtained. In this load-displacement diagram, displacements x ₁ to x ₂
The energy absorbed during is calculated as the area of the shaded area in the figure. The weight of the energy absorbing member destroyed during that period is calculated (if the members have the same cross section, the cross sectional area and (x
₂ −x ₁ ) and specific gravity)), and the value obtained by dividing the absorbed energy amount by the weight is taken as the specific absorbed energy amount. x ₁ , x
The setting of ₂ , the speed of displacement of the pressing member, and the like can be set appropriately.

[0029]

As described above, according to the energy absorbing member of the present invention, the energy absorbing member is made of a composite material of resin and carbon fiber, and the resin has a high energy release rate G _IC or a high breaking elongation. And the carbon fiber has high tensile strength and low surface functional group content (O
/ C), it is possible to effectively utilize the strength of the carbon fiber peeled from the resin during energy absorption,
High energy absorption performance can be obtained.

[Brief description of drawings]

FIG. 1 is a partial vertical cross-sectional view showing a state when an end portion of an energy absorbing member of the present invention is broken.

FIG. 2 is a perspective view showing an example of the shape of the energy absorbing member of the present invention.

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

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

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

FIG. 10 is a vertical sectional 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 an exploded perspective view showing a method for measuring a specific absorbed energy amount.

FIG. 13 is a load-displacement diagram in the measurement of the amount of specific absorbed energy.

[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 21 Energy absorbing member 22 Pressing member 41 Energy absorbing member 42 End portion 43 Carbon fiber

Continuation of the front page (56) References JP-A-2-305860 (JP, A) JP-A-3-168219 (JP, A) JP-A-4-146210 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) F16F 7/12 C08J 5/04

Claims (3)

(57) [Claims] 1. A composite material of resin and carbon fiber,
The energy release rate G _{IC of the} resin is 100 J / m ² or more, and the tensile strength of the carbon fiber is 450 kgf.
/ Mm ² or more, the amount of surface functional groups (O / C), which is the atomic number ratio of oxygen (O) and carbon (C) on the surface, is less than 0.08. 2. A composite material of resin and carbon fiber,
The surface elongation of the resin is 30% or more, the tensile strength of the carbon fiber is 450 kgf / mm ² or more, and the amount of surface functional groups is the atomic ratio of oxygen (O) to carbon (C) on the surface. (O / C) is less than 0.08. 3. The energy absorbing member according to claim 1, wherein the surface roughness of the carbon fiber is 1.0 or more and less than 1.08.