JPH03272828A - Structure of compression fastening section for fiber reinforced composite material - Google Patents

Abstract

PURPOSE:To prevent the generation of creep phenomenon by fitting a fastening element with a through-hole having its axis vertical in the fiber orienting direction of a compos ite material and its one end forming a conical tapered shape and also with a seating face of conical tapered shape in an opening of conical tapered section through a washer of conical tapered shape fit for the opening. CONSTITUTION:A through-hole for a fastening element with an inner wall face 21 of conical tapered shape and a cylindrical inner wall face 22 is formed on a laminate fiber reinforced composite material 2, and an axis l of the through-hole conforms with a laminate path 11 of the fiber reinforced composite material 2. A washer 3 covering the fiber reinforced wall face 21 and the cylindrical wall face 22 is installed in the through-hole. A part 5 is fastened on the opposite side of a forming face of an opening of conical tapered shape of the composite material 2 by bolts 4 and nuts 1. Tapered sitting faces 11 of the nuts 1 are closely in contact with the washer 3 covering the conical tapered opening section. Creep phenomenon can be prevented sufficiently by forming a compression fastening section of said structure even when thermal stress caused by the thermal expansion is applied in the laminating direction of the fiber reinforced composite material.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a compression fastening structure for fiber reinforced composite materials.

[Problems to be solved by conventional techniques and inventions] In recent years,
In order to reduce weight, attempts have been made widely to form structural members such as white motor vehicles using composite materials reinforced with #a fibers. For joining fiber-reinforced composite materials, sweat binding elements such as bolts are often used from the viewpoint of strength (1). In this case, the fastening part of the fiber-reinforced composite material has a cylindrical through-hole for receiving a bolt, etc., and the fibers in the fiber-reinforced composite material are arranged perpendicularly to the axes 1 and 2 of the through-hole. , the direction (9, had a structure. 7) is a structure like this, the following 1.
・There are problems such as 5''' and 7. In other words, generally speaking, when fibers are added to the resin, the coefficient of thermal expansion decreases, but the coefficient of thermal expansion in the direction perpendicular to the direction of fiber orientation decreases. Since the coefficient of thermal expansion does not decrease that much, when the compression fastening part is heated, the fiber-reinforced composite material near the fastening part tends to expand greatly in the axial direction of the through hole.In other words, the area around the through hole The resin tends to expand against the compressive force of the fastening element.As a result, a creep phenomenon occurs in the resin near the fastening portion, resulting in a problem in that the tightening force of the fastening element decreases.

Various proposals have been made to solve these problems. Japanese Utility Model Application No. 60-182202 discloses a structure in which a spring washer is used to press the periphery of a through hole. Furthermore, Jitsuma No. 195L-36901 discloses a structure in which a metal insert is embedded around a through hole.

However, above 5. Both structures result in increased weight and contradict the intent of using fiber-reinforced composites to reduce weight. Furthermore, in the latter structure, since the fiber-reinforced composite material and the metal insert have different properties such as linear expansion coefficients, cracks are likely to occur near the interface between the fiber-reinforced composite material and the metal insert.

Furthermore, a step of attaching a metal insert after forming the fiber-reinforced composite material is required, which is unfavorable in terms of productivity and economy.

In addition, a structure was devised to prevent the creep phenomenon by placing a heat insulating material around the compression fastening part and reducing thermal expansion near the compression fastening part (Utility Model Application No. 59-8156801).
However, it cannot be expected that the heat insulating effect will be perfect, and problems remain such as the bonding strength of the heat insulating material and the complexity of molding.

Furthermore, there is a resin structure in which long fibers are oriented in the direction of the compression fastening force in the peripheral part of the through hole of the compression fastening part. Long fibers are embedded in the manufactured structure σ), and the molding around the compression fastening part is complicated, and the productivity θ) is unfavorable.

Therefore, an object of the present invention is to be able to prevent the creep phenomenon;
Another object of the present invention is to provide a fiber-reinforced composite material clasp fastening structure that can be formed firmly, easily, and with a low degree of stiffness without causing problems such as increased weight.

[Means to solve the problem]

Achieved the above objective r<<As a result of various studies, the present inventor has developed a through hole having a conically tapered hole portion with its axis perpendicular to the fiber orientation direction as a compression fastening part provided in a fiber reinforced composite material. If a fastening element with a tapered seat surface is attached to this through a conical washer,
The present invention was completed by discovering that it is possible to create a fastening structure that prevents the creep phenomenon, does not increase the weight of the compression fastening part, and can be formed easily and with a low degree of compression. did.

That is, the fiber-reinforced composite ω compression fastening structure of the present invention has an axis substantially perpendicular to the fiber orientation direction of the composite material as a through hole for receiving a fastening element that generates a compressive force in the axial direction. 7. A through hole is formed in which the −@ portion is a conically tapered hole portion, and a conically tapered seat surface is provided through a conically tapered washer that fits the conically tapered hole portion. It is characterized in that a fastening element is fastened L2 to the conically tapered hole portion.

[Examples and effects] The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a partial sectional view showing an example of the compression fastening structure of the present invention. In the figure, the fiber-reinforced composite material 2 is a laminated fiber-reinforced composite material made by laminating a plurality of prepregs in the vertical direction, and the reinforcing fibers in the composite material are oriented in the horizontal direction (randomly in two dimensions in the horizontal plane). I'm here. A fastening element through-hole is formed in the laminated fiber-reinforced composite material 2 and has a conically tapered inner wall surface 2j and a cylindrical inner wall surface 22, and the axis l of this through-hole is The stacking direction and - L7 are the same. 7, the axis line is substantially perpendicular to the surface of the fiber-reinforced composite material 2. The through hole also has a conical arbor-shaped inner wall surface 21 and a cylindrical inner crab surface 2.
A washer 3 having a shape of 2-7 is attached.

The component 5 fixed to this fastening part is secured to the composite material 2 by means of a nut 1 having a pole 1-4 and a seat surface having a tapered shape-9.
Ql) It is fastened to the opposite side of the forming surface of the conical tapered hole portion. Here, the tapered seat surface 11 of the nut 1 comes into close contact with the washer 3 covering the conically tapered hole portion. Between Eoboldu 4 and the parts;
A commonly used deck ring-shaped washer 6 is interposed.

The compression fastening part 2] having such a structure can sufficiently prevent the creep phenomenon even if thermal stress is applied due to thermal expansion in the lamination direction of the fiber-reinforced composite material.

In other words, since the seat surface of the nut has a conical taper shape, if the fastening part is of the same size, it will be faster than when using a nut with a seat surface that is perpendicular to the normal fastening direction. , 0) is advantageous in that the contact area between the nut and the composite material can be increased.

Furthermore, compressive force by the fastening elements (bolts 4 and nuts in FIG. Expansion in the axial direction (force to push the washer 3 and nut 1) will be dispersed by the taper angle θ.For example, as shown in Fig. 2(a)
As schematically shown in , the tapered surface 2 of the fiber reinforced composite material 2
The compressive force f of the fastening element 1 is considered to be the resultant force of the component force fX perpendicular to the tapered surface 21 and the component force fy parallel to it. f is the component. In the fastening part structure of the present invention, as described above, f8 is reduced by adjusting the taper angle θ, thereby making it possible to prevent the creep phenomenon.Also, as schematically shown in Fig. 2, etc., the fiber-reinforced composite The force g applied to the washer and nut due to thermal expansion of the material is also applied to the tapered surface 21.
The component force gN perpendicular to , and the component force g which is flat f′i can be considered separately, but it is the component force axis perpendicular to the tapered surface 21 that is involved in the creep phenomenon, and in this way, the component force gx Creep can be prevented by reducing the size of .

It is preferable that the taper angle θ of the conically tapered inner wall surface 2I in the through hole is 3" to 45 degrees with respect to the axis l. If the taper angle θ is less than 30', the V of the tapered portion of the washer 3 The volume of the composite material part (region V) in Figure 1 corresponding to '1ffl' becomes smaller, and the bolt 4 and oak) 1
It becomes difficult to support the tightening force due to Therefore,
The region V of the composite material is likely to be damaged, and thereby fastening elements such as bolts and nuts are likely to separate from the composite material 2 in the direction of vertical force. If the taper angle θ exceeds 45°, the tightening force of the fastening element will not be sufficiently dispersed on the tapered surface, and the surface pressure (unit area (corresponding to f8 in FIG. 2(a)) cannot be reduced by a force perpendicular to the surface of contact. Similarly, the force (g, in FIG. 2 (1)) that attempts to push up the washer 3 and nut 1 due to thermal stress is not sufficiently reduced, and the IJ-bump phenomenon 4 cannot be reliably prevented.

Hereinafter, the present invention will be further described in detail with reference to specific examples.

Example 1.2, Comparative Example 1 A flat brif mold was placed in a vacuum chamber equipped with an exhaust fan. - Adsorbed. Next, apply nylon powder in the same manner as 1. It was adsorbed to the mold. At this time, the ratio of carbon fiber to nylon powder in the adsorption lid was adjusted so that the carbon fiber accounted for 40% by volume of the total.

Furthermore, alcohol-soluble nylon A-,,,TO(
A 5% methanol solution (manufactured by Toshi Co., Ltd.) was sprayed as a binder and dried to produce a flat brifol.

Stack 10 of these preforms and heat them at 280 t for 5 minutes.
) The pressure catheter was removed and made into a laminated flat plate molded body.

A through hole was formed in this M carbon fiber reinforced composite material, as shown in FIG. 1, in which a conically tapered hole portion and a cylindrical hole portion were continuous so as to have the same axis. In this case, the taper angle θ of the conical Te-moon shape is 45 in Example 1.
°, and in Example 2, it was closed by 3".

As Comparative Example I, a through hole with a taper angle of 15° was also formed.

Attach a washer+ to the conical taper-shaped hole portion of each through-hole, and as shown in FIG. Bolts were tightened using a Ni-bolt and an oak with a conically tapered seat surface. The initial axial force of each bolt tightening is 2001)k
gf.

Each bolted joint was heated at 100 t for 4 hours, and the axial force of the bolted tightening was measured immediately after heating.

Next, let it cool to room temperature, measure the axial force again, adjust the bolt tightening axial force to 2000 kgf again for each fastening part that has undergone the above operation, and then heat it at 100 t for 4 hours to measure the axial force. After cooling, the axial force at room temperature was measured.

Figure 3 shows the measurement results of each axial force.

As can be seen from Fig. 3, in the fastening structure of Examples 1 and 21J, the reduction in the tightening force (axial force) caused by the bolts and nuts is small even when subjected to the cooling cycle in 7. . In particular, the decrease in axial force after the second heating/cooling cycle is smaller than that during the first cycle, but this is due to the minute depressions in the conically tapered surface of the laminated fiber-reinforced composite material caused by the first heating. This is thought to be because the contact surface between the conical tapered surface and the washer became smoother. - It can be seen that in the fastening section of the comparison example, the axial force for tightening the bolt is reduced.

As is clear from the above, in the compression fastening part III structure of the present invention, the contact surface between the fastening element and the composite material is set obliquely with respect to the axial direction of the fastening element, so that the The force acting on the fastening element is dispersed not only in the axial direction of the fastening element and in the direction perpendicular to the fiber orientation direction of the composite material, but also in other directions, thereby preventing the creep phenomenon caused by thermal expansion. . Moreover, since the through-hole into which the compression fastening element 4 is inserted is integrally formed in the fiber-reinforced composite material without using metal inserts or the like, its molding becomes easy.

Although the present invention has been described based on examples, the present invention is not limited thereto, and various changes can be made without departing from the spirit of the present invention.

For example, fastening elements are not only a combination of bolts and nuts, but also
Other mechanical fastening elements such as rivets may also be used.7 Also, when combining a bolt and a nut, it is not necessary to set the nut to have a conical arbor-shaped seat m'J. The seat surface on the bolt side may be deformed into a conical taper shape (7).

Further, the fibers used in the fiber reinforced composite material may be either long fibers or short fibers.

〔Effect of the invention〕

The compression fastening section of the fiber reinforced composite material according to the present invention does not cause a creep phenomenon even if it is repeatedly heated, and there is almost no decrease in the tightening force for attaching parts. Moreover, its structure is simple and can be easily formed. Therefore, such a compression fastening part can be applied to various parts of an object made of fiber-reinforced composite material. For example, it can be applied to a compression fastening part where heat generated by a disc brake is propagated and heated, such as a compression fastening part of a road wheel of a car made of fiber-reinforced composite material.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view showing a compression fastening structure according to an embodiment of the present invention, and FIGS. FIG. 3 is a schematic diagram showing the direction of the acting force, and FIG. 3 is a graph showing the axial force for tightening the bolt and nut in Example 1.2 and Comparative Example 1. 1... Nut 2... Fiber reinforced composite material 3... Washer 4... Bolt 11... Conical tapered seat surface 21 L... Conical tapered inner wall surface/Axis of through hole Applicant Honda Saeto, Representative of Giken Co., Ltd. Patent Attorney Tachibana Takaishi
Horse figure 2

Claims (1)

[Claims] In a compression fastening structure of a fiber-reinforced composite material, the through hole for receiving a fastening element that generates a compressive force in the axial direction has an axis substantially perpendicular to the fiber orientation direction of the composite material, and one end thereof has a conical taper. A through hole serving as a hole portion of the shape is formed, and a fastening element having a conically tapered seat surface is inserted into the conically tapered hole portion through a conically tapered washer that fits the conically tapered hole portion. A compression fastening structure made of fiber-reinforced composite material, which is characterized by fastening.