JPS61261035A - Manufacture of sandwich cylindrical material provided with hole and made of fiber reinforced plastics - Google Patents

Abstract

PURPOSE:To enable stable manufacturing by mitigating tensile stress drastically, by a method wherein an inner layer skin molded on a winding mold is shifted on a processing mold whose diameter is slightly larger than that of the winding mold and a core material is stuck to the external circumference. CONSTITUTION:An inner layer skin 1 molded on a winding mold A through a filament winding (FW) method is shifted onto a processing mold B whose diameter is slightly larger than that of the winding mold by removing the inner layer skin 1 from the winding mold and a form of the outside of the same is shaped through machining. Then a core material molded beforehand is stuck to the external circumferential surface of the skin 1 and a form of the external circumferential surface of a core 2 is shaped through machining. As for a laminate whose dimensions of the outside diameter of the core 2 has been shaped, winding, curing and molding of an outer layer skin 3 based on the FW method are performed on the external circumferential surface of the core 2 by either shifting the same to the winding mold A by removing the same once from the processing mold B or leaving the same on the processing mold B as it is and the external circumferential surface of the skin 3 is machine. With this construction, mitigation effect on tensile stress can be obtained. A crack is not generated on a foam.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a sandwich cylinder made of fiber reinforced plastics (FRP), particularly a sandwich cylinder in which a syntactic 7 ohm core layer is wrapped with an FRP skin layer. Relating to a manufacturing method.

[Conventional technology and its problems]

Although the purpose of using FRP is diverse, the most important factor is to reduce the weight of the structure. However, reinforcing fibers and resin ma)
Reducing the weight of FRP made of IJ socks (there is a limit to this. Therefore, we selected a material with extremely low specific gravity such as foam as the core material, and a material with excellent strength and rigidity as the skin material. A so-called sand-inch structure is being considered.

The core material for this sand inch structure is generally
The honeycomb structure made of metal, FRP, paper, etc. is rigid,
It is adopted from the viewpoint of weight, but in applications such as deep-sea structural materials, there is a risk of water intrusion into the core cavity.
Not practical.

On the other hand, the above-mentioned syntactic 7 ohm, in which microscopic hollow bodies made of glass, plastic, etc. are uniformly dispersed in a resin matrix, ■ has closed cells, so water will not enter the voids unless cracks occur in the resin matrix. It has the following characteristics: (1) it has high compressive strength and can withstand strong lateral pressure; (2) it has a relatively low specific gravity, and it satisfies the various conditions necessary for a buoyant body.

Therefore, a sandwich cylindrical body having a skin layer of FRP and a core layer of syntactic 7 ohm is considered to be appropriate as an outer structural material for a deep-sea submersible or the like.

However, syntactic foam has a low tensile strength (approximately 34/d) and a high coefficient of thermal expansion (30XiO"
-'/°C), so when combined with FRP materials, the foam tends to crack due to thermal residual stress during hardening, resulting in poor manufacturability.

That is, in the conventional manufacturing method, resin-impregnated fibers are first wound onto a winding die in an optimal configuration using the FW (filament winding) method, and then cured, and the resulting inner layer skin is slightly smaller than the winding die. The skin is transferred onto a processing mold with a large diameter with zero interference or a slight interference, and the inner diameter of the skin is expanded and the outer periphery is machined to reduce uneven thickness and bring it closer to a perfect circle.

Thereafter, the inner layer skin is transferred onto the wrapping mold again and attached to the outer circumferential surface of the preformed syntactic foam core material using an adhesive.

Next, the laminate of the inner skin and core is transferred onto a processing mold, the thickness unevenness is adjusted by machining the outer periphery of the core, and the FW
The outer skin is formed by the method. After that, final circumferential processing and length adjustment processing are performed to produce the product.

However, a problem with this method is that there is a high probability that cracks will occur for 7 ohms when inserting the syntactic foam into a processing mold after pasting or during machining.

As a result of examining the cause, the present inventors reached the following conclusion.

That is, when inserting the workpiece into the processing mold, normally, in order to remove uneven thickness, a workpiece mold with an outer diameter equal to or slightly larger than the inner diameter of the workpiece is pre-cooled with a cryogen, and the workpiece is inserted into this mold and allowed to cool to room temperature. A ``cold fit'' method is applied, which involves machining after return. In this case, the processing mold needs to have a larger coefficient of thermal expansion in the circumferential direction than the workpiece, since the whole is cooled again after forming the form and the workpiece is removed.

When fitting a laminated cylindrical body of FRP and sintered foam into a processing mold using this "cold fitting" method, for example,
When FRP (Carbon Fiber Reinforced Plastics) is 2m long and 7 ohm layer is 1111 m thick, the 7 ohm layer has a tensile stress of 1.71'f/mJ even if the mold cooling temperature difference is 1300 degrees. It only works and does not cause any cracks during processing. However, when the thickness of the layer is set to 1, a tensile stress of approximately 6.0 Kiil/- is applied to the adhesive MJ HA that adheres the FRP and the syntactic foam at a temperature difference of -300°C. This is approximately equal to the tensile strength of the adhesive.

Therefore, it is thought that the above cracks are mainly caused by the adhesive, and the cracks in the adhesive propagate to the 7 ohm material, and cracks also occur in the 7 ohm material.

Therefore, the inventors of the present invention further investigated and researched a forming method that allows cold fitting for machining and does not cause cracks at 7 ohms.As a result, the following method was found to be effective in solving the problem. I came to invent it.

[Means for solving problems]

There are two methods of the present invention to solve the above-mentioned problems, and one of them will be described first.

In the first method, as shown in Fig. 2, continuous fibers impregnated with resin in advance by the FW method are wound onto a winding die A in an optimal configuration, hardened and molded, and the inner layer skin 1 of FRP is formed. get.

Next, this inner layer skin 1 is removed from the wrapping mold and transferred onto the processing mold B shown in Fig. 3, which has a slightly larger outer diameter than the wrapping mold, by cold fitting, and the uneven thickness on the outer surface is removed. Machined to predetermined dimensions.

Next, while the inner skin 1 is still fitted into the processing mold B, a pre-formed sintered foam core material is adhered to the outer peripheral surface of the skin 1, and the skin 1 and the core 2 are integrated as shown in FIG. Obtain a laminate.・For the core 2, in addition to inserting and gluing one cylindrical body, it can also be a curved plate divided in the circumferential direction, a ring divided in the axial direction, or divided into two directions, the circumferential direction and the axial direction, as shown in Fig. 5. The curved blocks 2a may be bonded together, and then the outer peripheral surface of the core 2 is shaped by machining.

Once the outer diameter of the core 2 has been adjusted, the laminate is removed from the processing die B. ! As shown in Fig. 4, it is transferred to a winding die A, on which an FRP outer layer skin 3 is formed by the FW method, and then returned to the processing die B and the outer periphery of the outer skin 3 is machined or shaped. The outer skin 3 is left as it is on the processing mold shown in FIG. 3, and the outer skin 3 is wrapped around the outer peripheral surface of the core 2 by the FW method and then hardened and molded, and the outer peripheral surface of the skin 3 is machined. Thereafter, when the core 2 is removed from the processing mold and the length dimension is adjusted by machining, the inner and outer circumferential surfaces of the core 2 are adjusted to the skin 1 as shown in FIG.
A sandwich cylinder 4 covered with 3 is obtained.

According to the above method, regardless of whether the outer layer skin 3 is molded on molds A or H, the resulting products are, for example, skins 111.3 each weighing 2 g of CFRP, and core 2 containing 11 mg of CFRP.
Assuming that it is a sandwich cylindrical body with a total thickness of 15 mm, the stress generated in the syntactic 7 form core when a temperature difference of -300°C is applied to it is approximately 2.4 KF/
1rd tensile stress, and the core sufficiently withstands this stress, so no cracks occur. This stress relieving effect is produced by fitting the inner layer skin 1 onto a processing mold and adhering the core material.

Next, another method of this invention will be described.

In this second method, the steps from forming the core 2 on the inner layer skin 1 transferred from the winding mold to the processing mold and machining the outer circumferential surface are the same as the previous method. That is, the difference between the second method and the first method is that after this, the laminate of the inner skin 1 and core 2 is removed from the processing mold, and the outer skin 3, which has been molded in advance by the FW method, is inserted into the laminate. There is only a point where it is press-fitted to the outer periphery.

In this case, it is preferable that the outer diameter of the laminate be equal to or slightly larger than the inner diameter of the outer circumferential skin 3, and specifically, the interference should be about 0 to 0.37 diameter to eliminate misalignment of the axes of the two.

According to this second method, the temperature applied to the adhesive layer can be limited to only the temperature necessary for curing the adhesive, so that the influence of thermal stress on the core is even smaller than in the former method.

〔effect〕

As described above, in the method of the present invention, the inner layer skin formed on the wrapping die is transferred onto a processing die whose diameter is slightly larger than that of the wrapping die, and the core material is adhered to the outer periphery. , the tensile stress occurring in the adhesive layer can be greatly alleviated, and therefore, there is no cracking of the syntactic firm core due to the tensile stress of the adhesive, making it possible to manufacture a stable cylindrical body. .

The crack prevention effect of the core is due to the second layer that press-fits the outer skin.
This is more noticeable than in the case of the above method.

In addition, since the outer peripheral surfaces of the inner and outer skins and the core are individually machined and shaped, a cylindrical body with less uneven thickness and high buckling resistance can be manufactured.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a sandwich cylinder obtained by the method of the present invention, and FIGS.
FIG. 5 is a perspective view showing an example of the core material. DESCRIPTION OF SYMBOLS 1... Inner layer skin, 2... Core, 3... Outer layer skin, 4... Sandwich cylindrical body, A... Wrap type, B
...Processing type.

Claims (5)

[Claims] (1) In a method for manufacturing a sandwich cylindrical body in which the inner and outer skin layers are made of fiber-reinforced plastic and the core is made of sintered foam, the inner layer skin is formed on a wrapping mold by the filament winding method, and then this skin material is placed on the wrapping mold. The outer circumferential surface is machined onto a processing die with a larger outer diameter than the original skin. Next, a pre-fabricated core material is bonded to this surface, the outer circumferential surface of the core material is machined, and then the inner layer skin is formed. The laminate of the core and the core is once transferred to a winding mold or left as is on the processing mold, and an outer skin layer is formed on the core by a filament winding method, and finally the outer periphery of the skin layer is shaped by machining. A method for producing a sandwich cylindrical body made of fiber-reinforced plastics, characterized by: (2) The method for producing a sandwich cylindrical body made of fiber-reinforced plastics according to claim (1), characterized in that the core material is molded in sections in the circumferential direction, the axial direction, or both directions and then bonded. (3) In a method for manufacturing a sandwich cylindrical body in which the inner and outer skin layers are made of fiber-reinforced plastic and the core is made of sintered foam, the inner layer skin is formed on a wrapping die by the filament winding method, and then this skin material is placed on the wrapping die. The outer circumferential surface is machined onto a processing die with a larger outer diameter than the original skin. Next, a pre-fabricated core material is bonded to this surface, the outer circumferential surface of the core material is machined, and then the inner layer skin is formed. A method for producing a sandwich cylindrical body made of fiber-reinforced plastics, characterized in that a laminate of a core and a core is removed from a processing mold, and an outer skin formed in advance by a filament winding method is press-fitted onto the outer periphery of the laminate. (4) The method for manufacturing a sandwich cylindrical body made of fiber-reinforced plastics according to claim (3), characterized in that the core material is molded in sections in the circumferential direction, the axial direction, or both directions and then bonded together. (5) A fiber-reinforced plastic sandwich according to claim (3) or (4), wherein the outer diameter of the laminate is equal to or slightly larger than the inner diameter of the outer layer skin. Method of manufacturing a cylindrical body.