JPS598537B2 - Hole processing method for FRP molded body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for drilling holes in an FRP molded body, and for steel leaf springs used in vehicle suspension systems, for assembly as a stacked leaf spring device and positioning when installing on a vehicle. A center bolt insertion hole is provided in the longitudinally intermediate portion and opened in the thickness direction.

In the case of an FRP leaf spring, if a through hole is drilled after molding, the embedded reinforcing fibers will be cut, resulting in a decrease in strength.

Additionally, facilities are required to remove dust from the resin and reinforcing fibers generated during drilling, and depending on the type of reinforcing fibers, expensive drills are required. Furthermore, there is a problem that cracks are likely to occur in the resin part. In addition, in order to eliminate such defects, in the conventional method, a pin is inserted into the material in advance during leaf spring molding, and a pin is removed after the material hardens to form a through hole. Due to the flow of the reinforcing fibers, the reinforcing fibers move to the left and right with the pin as the border, and as a result, there are parts in front and behind the hole where there are no reinforcing fibers (only resin), and there is also a partial flow in the resin part. This is accompanied by a decrease in D strength. For example, the rate of decrease in bending elastic modulus was about 10% compared to the one without holes (more than 30% in the case of holes made after forming), and almost the same tendency was observed in fatigue strength. . The present invention has been made under the above circumstances, and an object of the present invention is to provide a method for forming holes in an FRP molded body in which holes can be formed without causing a substantial decrease in strength.

Hereinafter, the present invention will be explained with reference to the drawings.

In FIGS. 1 to 3, a mold 1 has an upper mold 2 and a lower mold 3, which may be almost the same as those in conventional equipment, and is used to mold a leaf spring b of a predetermined shape from an FRP material a. It is configured to obtain. Above upper mold 2 and lower mold 3
A guide hole 5 is formed in the plate spring b, into which a pin 4 having a sharp tip for forming a through hole c in the leaf spring b is slidably inserted. Note that 6 in the figure is a spacer for positioning the material a. The above-mentioned material a is formed by laminating a desired number of prepregs made of satin weave mats in which the matrix resin is epoxy, the curing agent is amine, and the reinforcing material is glass fiber, and is placed in mold 1 as shown in FIG. be done.

The prepreg may be laminated either before being inserted into the mold 1 or within the mold 1. Then, the material a is heated and pressed between the upper mold 2 and the lower mold 3 by, for example, a hot press or other appropriate means. In this case, the temperature is set according to the composition of the material a, as in the conventional case, and is maintained almost constant until curing is completed. Also, the pressure is about 0.5k
g/Cd or higher. When the resin reaches a semi-hardened state after a predetermined period of time determined according to its gelling properties, the pressure applied to the material a is applied to at least the peripheral area of the area where the holes c are to be formed, so that the pressure is approximately 11< 9/Crll or more, preferably approximately 2
kg/d or more, but not more than about 10k9/d, and in this state, insert the pin 4 into the guide hole 5 as shown in FIG.
A pin 4 is inserted through the hole c to form a through hole c. Pin 4 like this
The timing for inserting the material a is set in advance according to the gelling characteristics of the matrix resin that constitutes the material a. and,
After a predetermined period of time has elapsed after the pin 4 has been inserted and the material a has become hardened, the mold 1 is slowly cooled to near room temperature and then removed from the mold as shown in FIG. 3 to take out the leaf spring b. The characteristics of Example 1, which was formed as described above, and Comparative Example 1, which was formed using the same material by a conventional method, are shown in the following table in comparison.

Comparative Example 1 is a case where the hole forming pin is inserted from the beginning and the hole is drilled after forming, and the leaf spring dimensions are the same as in Example 1, with a width of 60 m71 L.
1 length is 13807! Im, thickness 12mm 1 hole diameter 8
．． It is 51m. As can be seen from the table, the products formed by the present invention are superior to those made by the conventional method in terms of both bending elastic modulus and fatigue strength, and this is due to the resin flow pattern and fiber cut. This is considered to be due to the fact that no fibers are observed and the fiber distribution is uniform.

Furthermore, when a laminated material of the glass fiber cloth-containing prepreg and the unidirectional carbon fiber-containing prepreg as described above was used as material a, the flexural modulus was approximately twice the value in the table. In other respects, almost the same characteristics as above were obtained.

Note that the present invention is not limited to the above-mentioned embodiments, and can be applied to, for example, forming holes in any FRP molded body in addition to leaf springs.

Furthermore, molded bodies such as leaf springs may be either mutually independent single figures or continuous composite bodies, and the number of holes formed in the same molded body may be either singular or plural. good. Further, instead of using the prepreg, a material may be used, for example, by a filament winding method or a continuous forming method in which braided fibers are impregnated with resin and passed through a predetermined mold by drawing or extrusion. In addition, various modifications and applications are possible within the scope of the gist of the present invention. As described above, when an FRP material is hardened and formed into a predetermined shape, the material in a semi-hardened state is pressurized at a position corresponding to the hole periphery, and the tip is sharpened. This is characterized in that a hole-forming pin is press-fitted to penetrate the material to form a through-hole.

Therefore, since there is no need to make holes after molding, the reinforcing fibers will not be cut, the number of man-hours can be reduced, and no dust or the like will be generated. Furthermore, existing molds can be used. In addition, compared to the conventional method of curing with a hole-forming pin inserted from the beginning, there is no generation of flow patterns of resin that can easily cause cracks, and there are no areas where there is only resin before and after the hole. The flexural modulus and fatigue strength are improved to the same level as those without holes.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a sectional view showing a state in which a material is placed in a mold, FIG. 2 is a sectional view showing a state in which a pin is press-fitted into the material, and FIG. FIG. 3 is a cross-sectional view showing a demolded state. 1...Molding mold, 2...Upper mold, 3...
...Lower mold, 4...Pin, 5...Guide hole, a...Material, b...Plate spring (molded body), c ......Through hole.

Claims (1)

[Claims] 1. When curing the FRP material and molding it into a predetermined shape,
When the above-mentioned material is in a semi-hardened state, pressurize at least the surrounding area of the material where the hole is to be formed, and press-fit a hole-forming pin with a sharp tip into the material and pass it through to form a through-hole. A method for forming holes in an FRP molded body, characterized in that: 2. The method of forming a hole in an FRP molded body according to claim 1, wherein the pressure applied to a position corresponding to the periphery of the hole is set to approximately 1 kg/cm^2 or greater.