JP2568028B2 - FRP pipe structure - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe-shaped structure made of FRP, and more particularly to a pipe-shaped structure made of FRP which exhibits unique elastic behavior by applying mechanical anisotropy. .

[0002]

2. Description of the Related Art Conventionally, in a pipe-shaped structure made of an isotropic material such as iron or aluminum, when a load is applied on its geometrical main axis, only bending occurs and no twist occurs. On the other hand, when a load is applied to a point that is not on the geometrical principal axis, a twist occurs together with the bending.

That is, as shown in FIGS. 8 and 9, one end of the pipe-shaped structure 1 made of the above-mentioned isotropic material is fixed to the fixed end 1.
a, the other end is a free end 1b, and a load is applied to the free end 1b so that the line of action intersects with the geometric main axis G of the pipe-shaped structure, as shown by the arrow in the figure. As indicated by the chain line, the pipe-shaped structure 1 is bent by the above load, but is not twisted.

On the other hand, as shown in FIGS. 10 and 11, one end of the pipe-shaped structure 1 made of the above-mentioned isotropic material is a fixed end 1a and the other end is a free end 1b. When a load is applied so that the line of action does not intersect the geometric main axis G of the pipe-shaped structure as indicated by the arrow in the figure, the pipe-shaped structure 1 is As well as bending, twisting occurs.

Incidentally, for example, in a robot arm or the like, it may be more convenient for the arm to be bent and twisted when a load is applied to a point on the geometric main axis. On the contrary, in some cases, for example, in the same robot arm or the shaft of a golf club, when a load is applied to a point that is not on the geometrical main axis, it is preferable that only bending occurs and no twist occurs.

The present applicant has previously filed Japanese Patent Application No. 1-307050.
Proposed a pipe-like structure made of FRP which exhibits the above-mentioned favorable deformation behavior. That is, an FRP formed by using two or more kinds of prepreg sheets having different fiber angles.
A pipe-shaped structure made of metal was proposed.

[0007]

However, in the above-mentioned pipe-shaped structure made of FRP, since two or more kinds of prepreg sheets are used, the fibers become discontinuous at the joint between the prepreg sheets and the strength decreases, There is a drawback that the original purpose of the fiber-reinforced material, that is, strength improvement, cannot be achieved. Further, joining of two or more kinds of prepreg sheets requires a high degree of workability in operation, and a pipe-shaped structure made of FRP could not be easily manufactured.

[0008]

In order to solve the above problems, the invention according to claim 1 makes the cycle length of the periodical change in the fiber alignment direction substantially equal to the circumferential length of the fiber reinforcing layer. As a result, the fiber directions of the layers constituting the fiber reinforcing layer are substantially the same in the thickness direction.
Moreover, in addition to the matters specifying the invention of the invention described in claim 1, the invention described in claim 2 is characterized in that in the alignment direction of the fibers as the peripheral length of each layer slightly increases from the inner layer to the outer layer of the fiber reinforcement layer. The feature is that the cycle length of the periodic change is slightly increased.

[0009]

According to the first aspect of the present invention, the cycle length of the periodical change in the fiber alignment direction and the circumferential length of the fiber reinforcing layer are substantially the same. Thereby, the fiber directions of the layers constituting the fiber reinforcing layer can be made substantially the same in the thickness direction. On the other hand, when different parts on the same circumference are compared, it means that fiber reinforcing layers with different fiber directions are formed, and the balance of deformation of each part generated when an external force is applied is lost, so-called mechanical anisotropy. Sex can be achieved. That is, even when a load is applied so that the line of action intersects with the geometric main axis G of the pipe-shaped structure, the shear deformation of each part is not canceled out as a whole of the pipe, and it is possible to cause bending and twisting. . On the other hand, even when a load is applied so that the line of action does not intersect with the geometrical principal axis G of the pipe-shaped structure, the shear deformation of each part can be canceled out as a whole of the pipe, and thus the geometrical principal axis G It is possible to compensate for the deviation of the line of action, to prevent twisting, and to cause only bending. Further, the pipe-shaped structure according to claim 1 does not need to use two or more kinds of prepreg sheets, and the fibers are continuous in the circumferential direction, so that the pipe-shaped structure has sufficient strength and is easy to manufacture. In addition, when the prepreg sheet is wound, the outer circumference of the already wound portion slightly increases according to the winding, and is slightly deviated from the cycle length of the periodic change in the fiber alignment direction. Even in this case, the effect of mechanical anisotropy is not greatly impaired if the fiber directions in the thickness direction are substantially the same,
As in the invention according to claim 2, as the circumferential length of each layer slightly increases from the inner layer to the outer layer of the fiber-reinforced layer, the cycle length of the periodical change in the fiber alignment direction is slightly increased to thereby reduce the lengthwise direction. The fiber directions can be matched more reliably.

[0010]

EXAMPLES The present invention will be described in detail below with reference to examples. A curing agent was mixed with a liquid epoxy resin and applied on a release-treated sheet. Carbon fiber was continuously supplied on this.
The fiber supply source was swung in a direction perpendicular to the supply direction so that the fibers had a substantially sinusoidal shape as shown in FIG. Next, a release-treated sheet was superposed on this, and pressure-bonded with a pressure roller to prepare a prepreg sheet.

Next, this prepreg sheet was cut into a width of 400 mm, wound around a release-treated mandrel having a diameter of 16 mm, and 12 layers were laminated. In the prepreg sheet, the period length L of the sine wave of the fiber of the first layer is substantially the same as the outer peripheral length of the mandrel, and the period length of the sine wave of the fibers of the second and subsequent layers is determined by the lamination of the prepreg sheets. As the perimeter length increases, it is gradually increased in an arithmetic series. Therefore, in all positions of the pipe, the directions of the laminated fibers are substantially the same.

A wrapping tape was spirally wound around the obtained laminate and heated to cure the resin, and the mandrel was pulled out to obtain an FRP pipe-shaped structure. The second plan view of the obtained FRP pipe-shaped structure
A front view is shown in FIG. FR according to the present invention
The pipe-shaped structure made of P could be made extremely easily as compared with the conventional pipe-shaped structure made of FRP made by using two or more kinds of prepreg sheets.

As shown in FIGS. 4 and 5, the FRP pipe-shaped structure has one end as a fixed end 1a and the other end as a free end 1b, and the free end 1b is indicated by an arrow in the drawing. As shown, when a load is applied so that the line of action intersects with the geometric main axis G of the pipe-shaped structure, the pipe-shaped structure 1 is bent and twisted by the load as shown by the chain line in the figure. It was Note that, in FIG. 4, the pipe-shaped structure made of FRP is installed so that it can be seen from the same direction as in FIG.

On the other hand, as shown in FIGS. 6 and 7, one end of the above FRP pipe-shaped structure is fixed end 1a,
If the other end is set as the free end 1b and a load is applied to the free end 1b so that a line of action is applied to a point Q not on the geometric main axis G of the pipe-shaped structure, as indicated by an arrow line in the figure As shown by the chain line in the figure, the pipe-shaped structure 1 was only bent by the above load and was not twisted.

As described above, the pipe-shaped structure according to the first and second aspects uses continuous fibers in which the fiber alignment direction changes periodically, and the fiber direction of each layer constituting the fiber reinforcement layer is Since they are substantially the same in the thickness direction, they exhibit mechanical anisotropy. Further, since the fibers are continuous in the circumferential direction, they have sufficient strength and are extremely easy to manufacture.

[Brief description of drawings]

FIG. 1 is a diagram showing a part of a prepreg sheet used in an example of the present invention, which is a diagram showing a state where fibers are aligned.

FIG. 2 is a plan view of an FRP pipe-shaped structure according to an embodiment of the present invention.

FIG. 3 is a front view of an FRP pipe-shaped structure according to an embodiment of the present invention.

FIG. 4 is a view showing a state of a bending test of a pipe-shaped structure made of FRP according to an example of the present invention.

FIG. 5 is a diagram showing a state of a bending test of a pipe-shaped structure made of FRP according to an example of the present invention.

FIG. 6 is a view showing a state of a bending test of a pipe-shaped structure made of FRP according to an example of the present invention.

FIG. 7 is a diagram showing a state of a bending test of a pipe-shaped structure made of FRP according to an example of the present invention.

FIG. 8 is a view showing a state of a bending test of a conventional pipe-shaped structure made of an isotropic material.

FIG. 9 is a diagram showing a state of a bending test of a conventional pipe-shaped structure made of an isotropic material.

FIG. 10 is a view showing a state of a bending test of a conventional pipe-shaped structure made of an isotropic material.

FIG. 11 is a diagram showing a state of a bending test of a conventional pipe-shaped structure made of an isotropic material.

[Explanation of symbols]

 1 pipe-like structure 1a fixed end of pipe-like structure 1b free end of pipe-like structure 2 prepreg sheet 3 fiber

Claims (2)

(57) [Claims] 1. A FRP pipe-like structure having a fiber reinforcing layer, which is formed by laminating prepreg sheets having continuous fibers in which the fiber alignment direction changes periodically. By making the cycle length of the periodical change in the direction and the circumferential length of the fiber reinforcement layer substantially the same, the fiber directions of the layers forming the fiber reinforcement layer are substantially the same in the thickness direction. A pipe-shaped structure made of FRP. 2. The cycle length of the periodical change in the fiber alignment direction is slightly increased as the circumferential length of each layer slightly increases from the inner layer to the outer layer of the fiber reinforcing layer.
The pipe-shaped structure made of FRP according to claim 1.