JPS6217438A - Compression energy absorbing member - Google Patents

Abstract

PURPOSE:To obtain a member of light weight while having a large energy absorbing capacity against a shocking compression load by installing a supporting table on both end parts of a cylindrical resin body in which reinforcing fiber is arranged in the longitudinal and circumferential directions. CONSTITUTION:A cylindrical body 1 is made of a thermoset resin such as, an epoxy resin, an unsaturated polyester resin, a phenolic resin, etc. or of a thermoplastic resin such as, an ABS resin, a nylon resin, etc., and a reinforcing fiber such as, a carbon fiber, a graphite fiber, a glass fiber, etc. is arranged in its longitudinal and circumferential directions. Supporting tables 2, 3 are installed on both ends of the body 1, and chamfers 4 which triggers the breakage of the body 1 when a shock load is applied, are formed on the inside of the end part of the body 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a compression energy absorbing member, and more particularly, to a member suitable as a shock absorber for an aircraft seat or the like.

For example, when an aircraft fails to land, most of the impact energy generated is absorbed by the aircraft body, landing gear, etc. However, the occupants and passengers are also subjected to considerable shock. Sometimes it even exceeds 9G. Therefore, if such impact energy can be absorbed by the seat, passenger safety will be greatly improved. Compression energy absorbing members are used as members that absorb such impact energy.

As an impact energy absorbing member in an aircraft, 19
A held in the United States from February 12th to 14th, 1985.
ERO8PACE ENGINEERING C0
The one announced at NFERENCE AND 5HOW is well known. This member has a cylindrical body made of a composite material of resin and carbon fiber, and the carbon fibers are arranged in two directions of ±60'' with respect to the longitudinal direction of the body using a filament winding method. This is used as a diagonal member of the seat frame to absorb impact energy applied to the seat.

This member uses a composite material of resin and carbon fiber, which has higher specific strength and specific modulus than conventional metals such as aluminum alloy, so it is lightweight and suitable for other means of transportation. It is suitable as an aircraft member because it has a much greater weight reduction effect. However, if an attempt is made to further improve the impact energy absorption ability while maintaining the weight reduction effect, the following problems arise.

That is, in the conventional member, the carbon lIN is arranged in two directions of ±60' with respect to the longitudinal direction of the main body, as described above. That is, there is no carbon IIN extending in the longitudinal direction of the body. Therefore, the compressive strength in the longitudinal direction is not so high. Therefore, even if this is used as a compression energy absorbing member, the crush load (crushing load) corresponding to the amount of energy absorbed will not become so high.

This means that in order to further improve the absorption capacity, the crush stroke must be made longer or the wall thickness must be increased to increase the diameter of the main body. However, if this is done, the weight reduction effect will be diminished.

1. An object of the present invention is to solve the above-mentioned drawbacks of conventional members and to provide a member that is lighter in weight and has a greater ability to absorb energy against impulsive compressive loads.

To achieve the above object, the present invention has a cylindrical main body made of a composite material of resin and reinforcing fibers, and support stands attached to both ends of the main body. , and the reinforcement IIN is
It is characterized by compressive energy absorbing members arranged in two directions, a longitudinal direction and a circumferential direction of the main body.

When an impact load is applied to a working member due to compression in its longitudinal direction, the amount of strain energy absorbed by the member before it completely breaks due to the impact is determined by the amount of strain energy after plastic deformation of the material constituting the member. Depends on behavior. therefore,
If a composite material of resin and fiber is used, which does not undergo plastic deformation like metal but breaks rapidly, that is, it breaks brittle, it is expected that the energy absorption ability will be greatly reduced. The reinforcing fibers arranged in two directions, the longitudinal direction and the circumferential direction of the main body, work together to prevent local buckling and Euler buckling of the main body during impact, and to prevent brittle fracture at the ends. The destruction continues and progresses sequentially. This significantly improves the impact energy absorption ability.

Friend 11 To explain this invention in more detail based on an example of a real box, in FIG. 1, the compression energy absorbing member is made of resin that absorbs the impact energy generated when an impact load is applied due to compression in the longitudinal direction. And reinforcement I! A cylindrical main body 1 made of a composite material with fibers, a support base 2 fitted at one end of the main body 1 and inside the main body 1, and a support base 2 fitted at the other end of the main body 1 and also inside the main body 1, Moreover, it has a support base 3 fitted to the main body 1 with a slight gap. A chamfer 4, for example, formed by chamfering, is attached to the inside of the other end of the main body 1, and the support base 3 is provided with a curvature corresponding to the chamfer 4. However, if the main body has a diaphragm, this curvature is not necessarily attached.
You don't have to do it. The bumper 4 serves as a so-called trigger for the failure of the main body 1 when an impact load due to longitudinal compression of the main body 1 is applied to the member. In other words, since it is a trigger, the main body 1 is sequentially destroyed starting from the support base 3 side. Further, the main body 1 and the support base 2.3 are integrally connected, for example, by rivets, adhesives, or a combination of these. However, although this bond does not fail under normal use conditions, it will fail when subjected to a compressive impact load.

As mentioned above, the main body is made of a composite material of resin and reinforcing fibers. The resin forms the so-called matrix of the composite material, and typically thermosetting resins such as epoxy resins, unsaturated polyester resins, phenolic resins, and polyimide resins are used. However, it is also possible to use thermoplastic resins such as ABS resin, nylon resin, polycarbonate resin. Also,
Reinforced lIM is, for example, carbon a! Vagina, graphite 1 miscellaneous, organic high elastic fibers (e.g. polyaramid fibers), glass li
t, alumina Mi11. High strength and high elasticity such as alumina silica fiber, boron fiber, silicon carbide fiber, etc.
It is IN. Among them, it has relatively high strength and high elasticity,
Carbon fibers, graphite fibers, and organic high-modulus fibers are preferred because they have low specific gravity and can increase the specific strength of the main body. However, at least two of these reinforcing fibers can also be used in combination. The reinforcing fiber is in the form of a strand (multifilament) or a woven fabric. In the case of woven fabrics, it is most preferable to use plain woven fabrics, which have relatively little bending (crimping) of the warp and weft yarns at the intersection (and have a stable texture), but woven fabrics with other textures, such as satin woven fabrics and twill woven fabrics, are most preferable. However, these reinforcing fibers may have a content of 40 to 40% in the main body.
It contains 75% by volume, preferably 50-65% by volume.

The most important thing is the direction in which these reinforcing fibers are arranged. That is, the reinforcing IMs are arranged in two directions: the longitudinal direction and the circumferential direction of the main body. This is because composite materials are highly anisotropic materials whose properties are greatly influenced by the direction of reinforcing fibers. Therefore, if the reinforcing fibers are arranged only in the longitudinal direction, there will be only resin in the circumferential direction, and when an impact load due to compression in the longitudinal direction is applied, the main body will break at once, and it will be difficult to maintain a constant load. , and almost no impact energy absorption ability can be obtained. On the other hand, if the reinforcing fibers are arranged only in the circumferential direction, then only the resin will be used in the longitudinal direction.
After all, the absorption capacity becomes almost impossible. In this way, it is very important to arrange the reinforcing fibers in two directions, the longitudinal direction and the circumferential direction of the main body. However, in addition to these directions, the reinforcing fibers may be arranged roughly in two directions, for example, ±45 degrees. It is most preferable that they are arranged correctly in the circumferential direction, but a deviation in the direction of about ±5° can be tolerated.

To explain this point in more detail, the distribution of reinforcing fibers
The directions include two directions, the longitudinal direction and the circumferential direction of the main body as in this invention, that is, the two directions Oo and 906, and the ±45
Two directions of ° and two directions of ±606 are possible, but the crush load depends on the compressive strength in the longitudinal direction of one body, and as the compressive strength increases, the crush load, that is, the compressive energy absorption capacity also increases. . However,
The reinforcing fibers arranged in two directions, 00 and 90', are ±
The compressive strength in the longitudinal direction is about 4 times higher than that of 456 or those arranged in two directions of ±60°. In other words, the impact energy absorption ability becomes higher.

In this way, the reinforcing fibers are distributed in two directions: in the long direction of the main body and in the circumferential direction.
However, even if the amount of reinforcement WrN in the longitudinal direction is increased, the peak load at the time of a crash only increases, and the crush load corresponding to the amount of absorption of impact energy does not increase. Conversely, increasing the amount of reinforcing fibers in the circumferential direction reduces the crush load. Therefore, it is most preferable that the amounts of reinforcing fibers in the longitudinal direction and the circumferential direction are equal or approximately equal to each other.

The main body as described above uses so-called unidirectional prepreg, in which reinforcing fibers are arranged parallel to each other in a sheet shape and impregnated with resin, and so-called woven prepreg, in which reinforcing fiber fabric is impregnated with resin. can be obtained by winding the reinforcing fibers around a mandrel a desired number of times in such a way that the reinforcing fibers are oriented in the long direction and the circumferential direction of the mandrel, and then heating and pressurizing to shape. In addition, when molding is performed using a unidirectional prepreg, it is preferable that the layer in the circumferential direction becomes the outermost layer of the main body.

Most preferably, the innermost layer and the outermost layer are reinforced in the circumferential direction.
i, with a layer of reinforcing fibers in the longitudinal direction between them,
This is to adopt a so-called sandwich inch configuration. This is because unidirectional prepreg does not have reinforcing fibers interlaced like woven prepreg, so the outermost layer has longitudinal reinforcement 4.
This is because when the INs are arranged, cracks generated between the reinforcing fibers during the fracture process tend to propagate. In this regard, the use of woven prepreg is advantageous because the warp and weft yarns of the woven fabric are intertwined, so there is no need to worry about crack propagation as described above, and load fluctuations during a crash can be reduced. Furthermore, for example, if the warp yarns are oriented in the longitudinal direction of the mandrel, the weft yarns will inevitably be oriented in the circumferential direction, making it easy to form.

The support base fitted to the main body is made of a material with relatively high surface hardness, such as a composite material of metal and reinforced Ti fiber, stainless steel, nickel-chromium steel, nickel-chromium-molybdenum steel, etc. Among these, the most preferred is a composite material of metal and reinforcing fiber that has a high specific strength and can be made lightweight, especially one using an aluminum alloy as the metal. In that case, it is preferable to coat the surface in contact with the main body with chromium by plating or the like to improve the hardness of that surface.

The support provides a surface for transmitting impact loads to the body and for the body to fracture sequentially from the ends. Therefore, it is made larger than the outer diameter of the main body.

Now, when the above-mentioned member is subjected to a compressive load in the longitudinal direction, the connection between the main body 1 and the support base 2.3 is broken, the main body 1 comes into contact with the surface of the support base 3, and the chimney 4 contacts the trigger. Then, it is destroyed one by one starting from the end. Figure 2 shows the displacement (compression (7) I)t (mm
) and compression cylinder IP (Kg). In Figure 2, Pp is the peak load, p
c is the crush load. Absorbed energy is expressed by the area under the curve, but the actual energy absorption effect depends on the behavior after fracture initiation, that is, after the peak load appears. In other words, the crush load is important,
The best failure mode is one in which the crush load remains at a constant level. The energy absorption effect is calculated by dividing the crush load by the cross-sectional area and specific gravity of the main body.
In other words, they are compared in terms of specific absorbed energy.

Next, another example of the trigger that triggers the destruction of the main body will be explained. However, in this invention, it is not essential that the bird has -. However, it is preferable to provide a trigger because instability of the fracture can be prevented.

What is shown in Fig. 3 is the chamfer 4 shown in Fig. 1 above.
is applied over the entire thickness of the main body 1. This is the so-called Fulcienfa.

The one shown in FIG. 4 differs from the one shown in FIG. 1 in that the main body 1 is not provided with a chamfer, and the main body 1 rides on the curved part of the support base 3 under load and is pushed out from the inside. The destruction was made to proceed. in this case,
Although the curvature depends on the size of the main body, the radius may generally be 5 mm or less.

The fifth factor and the one shown in FIG. 6 are the same as that shown in FIG. 4, but a notch 5 is provided at the end of the main body 1 corresponding to the curvature of the support base, and this notch 5 is used as a trigger. be.

Furthermore, by applying a longitudinal compressive load that slightly exceeds the peak load to the main body as described above, and then removing the load and allowing the ends to crash in advance, it is possible to make the peak load and crush load approximately equal. . In that case, it would be an ideal mode of destruction, but it would add one more manufacturing process.

■3 Noribi This invention has high compressive strength and can prevent brittle fracture because the reinforcing fibers in the main body are arranged in two directions, the longitudinal direction and the circumferential direction of the main body. A large ability to absorb energy due to longitudinal compressive loads is obtained. Moreover, since the main body is made of a composite material of resin and reinforcing fibers with high specific strength, it can be made lightweight.

FIG. 7 is a graph showing the displacement-load characteristics tested for the member explained in FIG. However, the main body is made of a composite material of epoxy resin and carbon fiber plain fabric with equal fiber density in the warp and weft directions, and the warp is in the longitudinal direction and the weft is in the circumferential direction. are arranged in In addition, the inner diameter of the main body is 20mm,
The thickness is 1°55mm. The chip at the end of the main body is
It is attached at an angle of 30'' up to 0.95 mm from the inner surface of the main body, and the force support is provided with a curvature of 1 mm in radius.The support is made of stainless steel.

Further, the applied acceleration of the compressive load during the test was 1 mmZ. From FIG. 7, it can be seen that the compression energy member of the present invention has almost the same peak load and crush load.
It can be seen that this shows an ideal failure mode. However, this test is not based on impact loading. however,
A similar fractured t7 JT needle is obtained for impact loading.

The compression energy absorbing member of the present invention is suitable as a shock absorber for, for example, a seat in an aircraft or a motor vehicle, which has a particularly large impact reduction effect. Furthermore, it can be used as a shock absorber when an elevator falls, or as a shock absorber when a railway vehicle or the like collides.

[Brief explanation of drawings]

FIG. 1 is a schematic longitudinal cross-sectional view showing an example of the compressive energy absorbing member of the present invention, FIG. 2 is a graph showing general displacement-load characteristics of the member of the present invention, and FIG. 3 is the same as shown in FIG. 1 above. Fig. 4 is a partially cutaway schematic side view showing the main parts of the main body different from that shown in Fig. 1; 5 and 6 are schematic side views showing main parts of the main body different from those shown in FIGS. 1, 3, and 4, and FIG. It is a graph showing displacement-load characteristics obtained. 1: Main body made of a composite material of resin and reinforcing fibers 2: Support base 3: Support base 4: Chianon 7 5: Incision Patent applicant Japan Aircraft Development Association Figure 1 Figure 2 t (mm) Figure 3 Figure 5 Figure 6

Claims (1)

[Claims] A cylindrical body made of a composite material of resin and reinforcing fibers,
A compressive energy absorbing member comprising: a support base attached to both ends of the main body, and wherein the reinforcing fibers are arranged in two directions, a longitudinal direction and a circumferential direction of the main body.