JPH05332385A - Energy absorbing member - Google Patents

Abstract

PURPOSE:To provide high ability of absorbing an impact even against a load from a diagonal direction and further to improve energy absorbing efficiency per member weight without generating unexpected load at the time of collision deformation. CONSTITUTION:An energy absorbing member 1 is formed into a shape that one end of a tubular body of circular section is diagonally cut off. An area in an end part of the tubular body in a side, where a tilt surface 2 is formed, is generated 2/3 times or less the sectional area of a complete tubular part. The energy absorbing member 1 is formed of FRP(fiber reinforced plastic) of reinforcing synthetic resin by a long fiber (filament), into a condition that the filament is wound in a circumferential direction.

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 used for a supporting member of a bumper mounted on an automobile or a lower floor of a helicopter.

[0002]

2. Description of the Related Art In order to protect a vehicle body and an occupant at the time of a collision, an automobile is generally provided with a bumper in front of and behind the vehicle body for absorbing impact energy at the time of a collision. The bumper needs to irreversibly absorb energy against a large load applied when the vehicle collides with an obstacle. In order to increase the absorbed energy, various improvements have been made to the material and structure of the support member that supports the bumper body.

In addition, a member that is lightweight and has a high energy absorbing function is required in order to soften the impact when the aircraft lands on the lower floor of the seat of a helicopter due to an accidental accident, and especially to reduce the influence on passengers. Has been.

For example, German Patent (3626150) published on February 18, 1988 discloses a bumper attached to a stay of a vehicle body through an elastically deformable damping molded body made of fiber reinforced plastic. .. The damping molded body is formed in a substantially ring shape, and the reinforcing fibers of the fiber-reinforced plastic forming the damping molded body are arranged in the circumferential direction. The damping molded body is used in a state where an impact force is applied from its side surface, that is, in a state where the axis of the damping molded body is orthogonal to the direction in which the impact force is applied.

Further, in Japanese Patent Laid-Open No. 57-124142, an impact protection structural material used for a bumper is a strip 21 made of a fiber composite material (eg, epoxy resin-impregnated glass fiber) as shown in FIG. A structure 22 formed of a mesh structure and having a cylindrical shape has been proposed. The structure 22 is used in a state in which a compressive load is applied in the axial direction of the cylinder, and when an axial load acts on the structure 22, the nodes 2 of the reticulated tissue which face each other are opposed.
3 causes delamination, and shear yield occurs at the interface between the fiber and the matrix to absorb energy stepwise. The strip 21 is inclined at an inclination angle of 30 to 60 degrees with respect to the longitudinal axis of the structure 22. Further, each knot 23 is formed by about 10 layers of the strip 21 made of a fiber composite material.

[0006]

However, when a substantially ring-shaped fiber-reinforced plastic as disclosed in the above-mentioned German Patent is destroyed by applying an external force from its side,
The deformed portion is destroyed only in the portion in the same direction as the load, and the portion in the direction perpendicular to the external force remains substantially in its original shape and is not destroyed. Therefore, the energy represented by the product of the stress and the deformation amount (specifically, the area between the compression load-displacement amount curve and the axis representing the displacement amount) generated in the compressive deformation process when a load is applied to the member. There is a problem that the absorption amount is extremely small and the efficiency per member weight is poor.

On the other hand, the tubular impact protection structural material disclosed in JP-A-57-124142 is used in a state in which the bumper is supported so that a compressive load is applied from the axial direction of the tube. Therefore, when a compressive load is applied for destruction, all parts are destroyed, so that the energy absorption efficiency per member weight can be increased as compared with the case where a compressive load is applied from the side. However, the crossing angle of the strip 21 is 3
Since it is composed of a mesh structure of 0 to 60 degrees, there is a problem that when a compressive load in the axial direction acts, the cylindrical structure is easily compressed and deformed by a small load due to the deformation of the mesh structure. In addition, if there is a condition to reduce the impact on the human body like a bumper support member, it is necessary to suppress the maximum value of the load to a level that has a low effect on the human body. The energy absorption amount of becomes smaller. Therefore,
In order to meet the requirements of reducing the impact on the human body and increasing the amount of energy absorption during deformation, the sudden load is prevented from occurring and the compression load-displacement amount curve is set to a flat level with minimal load fluctuation. It is important to keep However, this impact protection structural material has a problem that the amount of energy absorbed is difficult to increase because the load is gradually reduced as the amount of displacement increases.

The present invention has been made in view of the above problems, and its purpose is to soften the impact at the time of landing due to a collision of an automobile or a rotor failure of a helicopter, and to reduce the influence on passengers. It is an object of the present invention to provide an energy absorbing member which does not generate a sudden load at the time of collision deformation, has a high impact absorbing ability even against a load from an oblique direction, and has a high energy absorbing efficiency per member weight.

[0009]

In order to achieve the above object, in the present invention, a reinforcing fiber is wound at least in the circumferential direction, and is formed into a tubular shape from a fiber-reinforced composite material filled with a matrix. The shape was cut obliquely so that the area of one end of the body was ⅔ or less of the cross-sectional area of the complete tubular portion, and the cross-sectional area continuously changed in the axial direction.

[0010]

The energy absorbing member of the present invention is attached so as to receive a compressive load from the axial direction of the tubular portion. When a load is applied to the energy absorbing member in the axial direction, the fracture starts gradually from the end portion having the smaller area. Then, the delamination in the circumferential direction along the reinforced fiber caused by the fracture propagates to the complete cylindrical part one after another, and the load fluctuation due to the occurrence of delamination is shown. It keeps changing and absorbs large amounts of energy in the meantime. When the energy absorbing member receives a compressive load from the axial direction and breaks, buckling failure occurs in all parts of the tubular body and the energy is absorbed. Therefore, the energy absorption efficiency per member weight is improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment embodying the present invention will now be described with reference to FIGS.
This will be described with reference to FIG. As shown in FIG. 1, the energy absorbing member 1 is formed in a shape in which one end of a cylindrical body having a circular cross section is obliquely cut. Two cutouts are provided, and two inclined surfaces 2 that form a predetermined angle with respect to a surface orthogonal to the axis are formed symmetrically. The energy absorbing member 1 is an FR made of synthetic resin reinforced with long fibers (filaments).
It is made of P (fiber reinforced plastic) and is formed in a state in which filaments are wound in the circumferential direction.

The energy absorbing member 1 is formed by winding a glass fiber (filament) around a mandrel while adhering the resin thereto, and then forming a FRP cylinder by a filament winding method in which the resin is heated and cured, and one end thereof is cut at a predetermined angle. It is formed by

The energy absorbing member 1 is used as a support member for a bumper or as a shock protection member to which a load is directly applied while receiving a compressive load from the axial direction. When an axial load is applied to the tubular body in which the reinforcing fibers are wound in the circumferential direction in this manner to cause compressive fracture, the tubular body causes buckling fracture at all parts over the entire circumference of the tubular body, resulting in energy loss. Absorbs. Therefore, although the weight of the material forming the tubular body is small, it absorbs a large amount of energy and becomes an excellent energy absorbing member with extremely high efficiency.

As the winding direction of the fibers is closer to the circumferential direction perpendicular to the axis of the tubular body, the fibers of all layers are arranged in parallel with each other, and the voids between the fibers due to the interlacing of the fibers are reduced, thereby filling the fibers. The rate is increased. The fibers mainly support the load applied to the tubular body from the outside, and the higher the fiber filling rate, the larger the load can be carried and the absorbed energy also increases.

If the fibers are arranged in parallel, lateral rubbing displacement of the fibers occurs in many portions due to a load perpendicular to the fibers, and they become fine circular ring-shaped strips that are fragmented and collapsed. Therefore, a large amount of energy can be absorbed even with the same weight.

When the fiber array stands in the axial direction, the crossing angle becomes large due to the axially symmetric array, and the gap caused by the disturbance of the parallelism also becomes large to form a mesh. When a compressive load in the axial direction acts in this state, the tubular body is easily compressed and deformed by a small load due to the deformation of the tissue, and the absorbed energy becomes small, which is not preferable. Therefore, it is preferable that the fibers wound in the circumferential direction of the tubular body be arranged as perpendicular to the axis as possible.

When the cross-sectional area of the tubular body is constant along the axial direction, when a compressive load is applied from the axial direction, the total load acts evenly on the entire cross section of the tubular body, and the tubular body forms one rigid body. It behaves as and withstands a large load above the average load. However, when delamination occurs at the weakest point of the tubular body and shear fracture occurs, the cracks expand at once and the tubular state collapses, and the load instantaneously shows a drastic decrease. However, thereafter, the load gradually increases and rises to a load level specific to the cross-sectional area of the tubular body, and the deformation progresses while maintaining the load, and the fracture energy is absorbed during that time. However, the absorbed energy is calculated by the displacement x load, and the total absorbed energy becomes an extremely small value because of the low load level after once collapsed.

On the other hand, the energy absorbing member 1 of the present invention has a shape in which one end side of a tubular body is cut obliquely,
The cross-sectional area of the tubular body changes continuously from the one end side in the axial direction,
It is the same as the area of the other end from the middle. When an axial compressive load is applied to such a tubular body, it gradually begins to break from the side with a smaller cross-sectional area, and the delamination along the fiber array direction (circumferential direction) that occurs due to the breakage is successively completed. It also propagates to the tubular part. Although the load changes due to the occurrence of delamination, the load changes while maintaining a substantially constant load level, and a large amount of energy can be absorbed during the change.

On the other hand, even in the case of the energy absorbing member 3 having the tapered portion 3a formed at the tip of the FRP cylinder as shown in FIG. 2, it is possible to avoid the sudden load fluctuation which is seen at the initial stage of breakage of the tubular body. However, by providing the tapered portion 3a at the tip of the tubular body in this way, the end portion of the tubular body becomes thin over the entire circumference. As a result, the whole area of the end works effectively against the compressive load from the front side, but there is no problem, but the compressive load from the diagonal direction with respect to the axis of the tubular body (oblique load)
However, the load level decreases and the absorbed energy decreases. Further, forming the taper portion at the end portion forms a sharp surface with a thin tip, and therefore involves a risk of cutting an object in front at the time of collision.

However, in the case of the energy absorbing member 1 in which the wall thickness of the tubular body is uniform over the entire length and the inclined surface 2 is provided on one end side, the direction of the end portion having the inclined surface 2 from which direction the oblique load is applied. Even if a load is applied, the cross-sectional area of the tubular body at the point of displacement is larger than that of the tapered portion 3a. Therefore, the absorbed energy also increases. Also, unlike the tapered portion, it has no thin and sharp surface and is excellent in safety.

The area of the tip end surface of the energy absorbing member 1 and the inclination angle of the inclined surface 2 with respect to the axis of the cylindrical body are determined by the maximum load and the load speed allowed during compression deformation. In order to reduce the maximum load generated, the area of the tip surface is mainly reduced. Further, the inclination angle is preferably 5 ° or more, and it is preferable to increase the inclination angle when the loading speed is high. The smaller the area of the tip surface, the smaller the burst of the initial compression load.However, if the area of the tip surface is extremely small, the tip becomes a bamboo spear-like shape and the absorbed energy at that part decreases. Therefore, the larger area is preferable, and the limit should be 2/3 of the cylindrical area.
Fig. 3 is a plot of how the maximum load at the initial stage of fracture changes depending on the ratio of the end area to the cylindrical area. The maximum load decreases linearly as the end area decreases, and Intersects with the line of (the peak value = 1) of the breakage load peculiar to the tubular body shown at the time of stable breakage from the end. Considering the variation of data, if the end area is 2/3 or less of the area of the tubular body, the initial breaking load does not exceed the stable breaking load. Therefore, a large energy absorption effect can be obtained while alleviating the shock at the time of collision. You can get it. Therefore, the area of the tip surface of the tubular body needs to be 2/3 or less of the cross-sectional area of the complete tubular portion of the tubular body.

When the energy absorbing member 1 is used in a moving body such as an automobile in a state where the energy absorbing member 1 directly receives a load without a bumper or the like, the tip of the energy absorbing member 1 is placed in the direction in which the load is most easily applied. It is preferable to install them so that they face each other. That is, when the moving body is installed near the center of the front portion or the rear portion, the energy absorbing member 1
Is installed parallel to the forward or backward direction, and when installed on the side, it is preferable to install so that the tip faces diagonally forward or diagonally backward.

Next, the energy absorbing member manufactured by using glass fiber (2310 tex) having a diameter of 13 μm as a filament and epoxy resin as a synthetic resin will be described more specifically.

While adhering a liquid containing a curing agent to an epoxy resin, glass fibers were wound in a substantially hoop shape on a metal cylinder (mandrel) having a diameter of 50 mm to form a cylinder having a thickness of 4 mm. Next, after putting it in the hot air oven for 8 hours to cure the resin, remove it from the mandrel and use FRP with a fiber filling rate of 65%.
A cylinder was obtained. This FRP cylinder is processed into two inclined surfaces 2
Energy absorbing member 1 of the present invention having the above, and energy absorbing member 3 as a comparative example having a tapered portion 3a at the tip.
And formed.

The energy absorbing member 3 of the comparative example has a tapered portion 3a formed at the tip thereof and having an angle of approximately 30 ° with respect to the axis. The tapered portion 3a is formed by cutting so that the thickness of the tip is 1 mm. On the other hand, the area of the tip surface of the energy absorbing member 1 of the present invention is the same as the area of the tip surface of the energy absorbing member 3 of the comparative example, and the angle between the inclined surface 2 and the tip surface is approximately 19 °. Like 2
It has been cut in places. The angle of the inclined surface 2 is set so that the length L1 of the tapered portion 3a and the length L2 of the inclined surface 2 match.

5 and 6 show the results of measuring the relationship between the compressive load and the amount of displacement when a compressive load is applied to both energy absorbing members 1 in the axial direction. 7 and 8 show the results of measuring the relationship between the compressive load and the displacement amount when a compressive load is applied to both energy absorbing members 1 from an oblique 30 ° direction. When an oblique load is applied, the energy absorbing members 1 and 3 are tilted at a predetermined angle as shown in FIG. 4, the base ends of the energy absorbing members 1 and 3 are fixed by a jig 4, and the load is applied in the direction of the arrow.

In the case of axial compression, there is little difference in the behavior between the energy absorbing member 1 of the present invention and the energy absorbing member 3 of the comparative example, and the energy absorption amount is almost the same. On the other hand, in the case of oblique compression, the energy absorbing member 1 of the present invention obviously has a faster rise of load and a larger absorbed energy. That is, the above is supported.

The present invention is not limited to the above embodiments, and for example, the number of inclined surfaces 2 may be one as shown in FIG. 9 (a), or may be three or more. .. It is preferable that the number of the inclined surfaces 2 is small in terms of energy absorption capability against an oblique load, and also from the viewpoint of reducing the number of processing steps and cost reduction. However, when it is required to eliminate the directionality of the compression behavior of the energy absorbing member 1 with respect to the axis, it is better to increase the number of inclined surfaces to balance the tip shape. Further, when cutting off a part of the cylindrical body, the cut may be made perpendicular to the peripheral surface as shown in FIG. 9B. Further, the cylindrical body forming the energy absorbing member 1 is preferably a cylindrical body from the viewpoint of easy manufacturing, but may be a polyhedral cylinder. However, in the case of a polyhedral cylinder, in order to prevent abnormal stress concentration from being formed at the joints between the faces as corners, the joints are formed as curved faces and the interlayer generated between fibers in the circumferential direction is prevented. It is preferable that the crack propagates smoothly. Further, the resin forming the FRP of the material is not limited to the epoxy resin, but thermosetting resins such as phenol resin and unsaturated polyester, as well as thermoplastic resins such as polyester and polyimide may be used. Further, as the reinforcing fibers, various functional fibers having high strength physical properties such as carbon fibers and aramid fibers may be used instead of glass fibers. In addition to using the energy absorbing member as a support member for the bumper, the energy absorbing member may be applied to a shock absorbing member that directly receives a shock load or a seat floor of a helicopter.

[0029]

As described above in detail, the energy absorbing member of the present invention, when broken, gradually starts to break from the end of the tubular body having the smaller area, and the load level is generally constant. The energy absorption amount is increased and the energy absorption efficiency per member weight is improved because the energy is absorbed and the energy is absorbed by buckling and breaking at all parts of the energy absorption member.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of an energy absorbing member of the present invention.

FIG. 2 is a schematic perspective view of an energy absorbing member of a comparative example.

FIG. 3 is a diagram showing the relationship between the end area of a tubular body and the maximum load at the initial stage of fracture when the ratio of the end area and the cylindrical area is changed.

FIG. 4 is a front view showing a supporting state when an oblique compression load is applied to the energy absorbing member.

FIG. 5 is a compression load-displacement amount curve when an axial load is applied to the energy absorbing member of the present invention.

FIG. 6 is a compression load-displacement amount curve when an axial load is applied to the energy absorbing member of the comparative example.

FIG. 7 is a compression load-displacement amount curve when a 30 ° oblique load is applied to the energy absorbing member of the present invention.

FIG. 8 is a compression load-displacement amount curve when a 30 ° oblique load is applied to the energy absorbing member of the comparative example.

FIG. 9A is a schematic perspective view showing an energy absorbing member of a modified example, and FIG. 9B is a front view showing an energy absorbing member of another modified example.

FIG. 10 is a schematic perspective view showing a conventional structural member for impact protection.

[Explanation of symbols]

 1 ... Energy absorbing member, 2 ... Inclined surface.

Claims (1)

[Claims] 1. Reinforcement fibers are wound at least in the circumferential direction and formed into a tubular shape from a fiber-reinforced composite material filled with a matrix, and one end portion of the tubular body has a complete tubular section. An energy-absorbing member having a shape that is cut diagonally so that the cross-sectional area continuously changes in the axial direction so as to be ⅔ or less of the area.