JPH0671654A - Resin mandrel - Google Patents

Abstract

PURPOSE:To provide a resin mandrel which is thermally expanded only in the radial direction while the thermal expansion in the longitudinal direction is controlled. CONSTITUTION:In a mandrel 1 in which a mandrel main body 3 made of a thermally expansible resin is fixed on a cylindrical core body 2, more than one void which penetrates the mandrel main body 3 in the longitudinal direction is installed. A detachable control member 4 which controls the mandrel main body 3 to expand in the longitudinal direction of the core body 2 is attached on the core body 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin mandrel used for internal pressure molding of a composite material pipe having a thermoplastic resin as a matrix. More specifically, the present invention relates to a resin mandrel which suppresses thermal expansion in the longitudinal direction and heats only in the radial direction. The present invention relates to a resin mandrel capable of expanding.

[0002]

2. Description of the Related Art Heretofore, a resin mandrel made of a thermally expansive resin such as polytetrafluoroethylene (PTEF) has been used for producing a composite pipe made of a thermoplastic resin as a matrix. The thermal expansion of the resin mandrel is used to perform internal pressure molding of the composite material pipe. An example of such a resin mandrel is shown in FIG.
Those shown in are generally known.

The resin mandrel is integrally constructed of a rod-shaped core body 21 made of iron, aluminum or the like, and a cylindrical mandrel body 22 made of a heat-expandable resin fitted and mounted on the core body 21. Has been done. The resin mandrel is set on the inner peripheral portion of the pipe material when the composite material pipe is heat-molded, and the mandrel body 22 is thermally expanded and presses the inner peripheral surface of the pipe, whereby the composite material pipe is pressurized to the internal pressure. It is molded.

[0004]

However, in the above-described resin mandrel, the material of the mandrel body is isotropic, and therefore, when a long pipe (about 1 m or more) made of a composite material is produced. Is remarkable in the amount of thermal expansion in the longitudinal direction of the mandrel body, and the elongation of the mandrel body in the longitudinal direction causes the pipe material during heat forming to move and deform, which significantly deteriorates the quality of the pipe after forming. There was a problem to say.

The present invention has been devised in view of such conventional problems. It is possible to suppress thermal expansion in the longitudinal direction and to perform thermal expansion only in the radial direction, without being limited in length. It is an object of the present invention to provide a resin mandrel capable of significantly improving the quality of a composite material pipe.

[0006]

In order to achieve the above object, the present invention provides a resin mandrel in which a mandrel body made of a heat-expandable resin is mounted on a rod-shaped core,
The mandrel body is provided with a plurality of hollow portions penetrating in the circumferential direction along the longitudinal direction of the core body, and a suppressing member for suppressing both ends of the mandrel body from expanding in the longitudinal direction of the core body in the core body. The gist is that it is detachably attached.

[0007]

The present invention is constructed as described above, and since the core body is provided with the restraining member for restraining both ends of the mandrel body from expanding in the longitudinal direction of the core body, thermal expansion in the longitudinal direction of the mandrel body is effective. Therefore, the mandrel body can be thermally expanded only in the radial direction, and the pipe material during the heat molding is not moved by the elongation of the mandrel body in the longitudinal direction, so that the pipe is not deformed. Therefore, it is possible to obtain a high quality composite material pipe without being limited in length.

Further, although the restraining member prevents the expansion in the longitudinal direction and increases the expansion pressure in the radial direction, the mandrel body is formed with a cavity portion penetrating both ends along the longitudinal direction in the circumferential direction thereof. Therefore, due to the deformation of the hollow portion, the high expansion pressure to the mandrel body is released to the hollow portion, and the mandrel body is not easily broken. Further, even if an excessive pressure is generated during heating, the pressure can be released to the cavity, and the outer mold and the mandrel body can be prevented from being broken.

Further, although the mandrel body shrinks during cooling, since the hollow portion is formed, a pressure toward the radially outer side of the mandrel body is generated as the hollow portion expands in the radial direction. The inner peripheral surface of is cooled while receiving a pressing force. Therefore, it is possible to effectively perform mold clamping during cooling, and it is possible to obtain a molded product that is more homogeneous and has excellent quality.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a perspective view of a resin mandrel according to the present invention. The resin mandrel 1 includes a rod-shaped core body 2,
A cylindrical mandrel body 3 fitted and mounted on the core body 2.
And a restraining member 4 which is provided on the core body 2 on both ends of the mandrel body 3 and restrains expansion of the mandrel body 3 in the longitudinal direction (axial direction).

The core body 2 is preferably made of a material that has heat resistance, a small change in thermal expansion, and is capable of adhering to the mandrel body 3 at room temperature. For example, a metal material such as iron or aluminum, or a ceramic material. It is configured. The mandrel body 3 is made of a resin having a thermal expansion property, for example, PTE.
F and ultra high molecular weight polyethylene. Further, as shown in FIGS. 2 and 3, the mandrel body 3 is provided along the longitudinal direction of the mandrel body 3 (through hole 3b into which the core body 2 is fitted).
A plurality of cavities 3a penetrating both ends are formed along the circumferential direction of the mandrel body 3. This cavity 3
The number, shape, etc. of a are actually determined in consideration of the ease of formation, the shape of each mandrel body 3 and the actual use conditions, but some principles are shown below.

The porosity of the hollow portion 3a is preferably 10 to 30% of the volume of the mandrel body 3. 1
If the ratio is less than 40%, both ends of the mandrel body 3 are restraining members 4
The mandrel body 3 is destroyed during the heating because it is limited by. If it exceeds 30%, the strength of the mandrel main body 3 is lowered, and the mold clamping pressure at the time of cooling the composite material pipe to be molded is lowered, so that a sufficient mold clamping effect cannot be often obtained. .

It is preferable that a plurality of hollow portions 3a having small voids be provided in the hollow portion 3a rather than a plurality of hollow portions 3a having large voids. Further, the hollow portions 3a are provided along the circumferential direction of the mandrel body 3. Rather than being localized, it is preferable to arrange them uniformly at substantially equal intervals along the circumferential direction. If the cavity 3a is too large, the mold clamping pressure and the like during cooling will be non-uniform, and if it is localized, the mold clamping pressure and the like during cooling will be non-uniform and the strength of the mandrel body 3 will be reduced at that part.

Furthermore, the cross-sectional shape of the cavity 3a is preferably circular or elliptical in order to evenly disperse the pressure received from the surroundings, and it is suitable that the outer peripheral surface of the mandrel body 3 is not too close to the cavity 3a. Distance L1 (cavity 3a
It is preferably 1/2 or more of the diameter). If the distance L1 is too small, the mold clamping pressure at the time of cooling becomes uneven between the part with the cavity 3a and the part without the cavity 3a, and a sufficient mold clamping effect cannot be obtained. Each of the above principles is selected to the extent that it does not cause a decisive problem.

The restraining member 4 is formed in a ring shape, the through hole 4a in the inner circumferential portion of the ring shape is formed so as to be fittable to the outer circumference of the core body 2, and the size of the ring portion 4b is within a range in which the restraining effect appears. Therefore, it is preferable that it is as small as possible in handling during insertion. It is usually formed with reference to the size of both end faces of the mandrel body 3 during thermal expansion. The restraining member 4 is provided so as to come into contact with both end faces of the mandrel body 3 and be detachably attached to the core bodies 2 at both ends. The restraining member 4 may be attached / detached by, for example, forming a thread groove on the end portion of the core body 2 and attaching / detaching the restraining member 4 with a nut via the abutting member. Absent. Since the restraining member 4 has a rubber-like hardness under the temperature condition when the mandrel body 3 is used, it does not need to be considered so much in terms of strength, and can be made of, for example, an iron plate having a thickness of 1 to 2 mm. . Next, the operation of the above-described resin mandrel 1 of the present invention will be described. A resin mandrel 1 is formed by molding a preform with a prepreg, which is a material of a pipe made of a composite material using a thermoplastic resin as a matrix, and inserting the preform into the outer mold, and then the mandrel body 3 corresponds to the hollow inner peripheral portion of the preform. Is set, and after the restraining members 4 are attached to both ends of the mandrel body 3, the mandrel body 3 is expanded by heat when heated for a predetermined time.

At this time, since the expansion of the mandrel body 3 in the longitudinal direction is suppressed by the suppressing member 4, the mandrel body 3 expands only in the radial direction, and the outer peripheral surface of the mandrel body 3 is within the preform of the pipe made of the composite material. Internal pressure is formed by pressing the peripheral surface. As a result, the pipe material during the heat forming is not moved by the elongation of the mandrel body 3 in the longitudinal direction, and the pipe material is not deformed such as misaligned. Therefore, the quality is not limited to the length. It is possible to obtain high composite pipes.

Although the restraining member 4 prevents expansion in the longitudinal direction and increases the expansion pressure in the radial direction, the mandrel body 3 is formed with a plurality of cavities 3a penetrating both ends along the longitudinal direction. Therefore, this cavity 3a
Due to the deformation of the mandrel body 3, a high expansion pressure on the mandrel body 3 is released to the cavity 3a, and the mandrel body 3 is not easily broken. Further, even if an excessive pressure is generated during heating, the pressure can be released to the hollow portion 3a, and the outer mold and the mandrel body 3 can be prevented from being broken.

Furthermore, since the core body 2 is located inside, the thermal expansion of the mandrel body 3 in the outward direction can be increased during molding. Therefore, even if the mandrel body 3 is thin, the inner peripheral surface of the pipe material is small. A sufficient pressing force for can be obtained. After the heat molding, the pipe material is cooled with water or the like with the outer mold and the resin mandrel 1 set. Although the mandrel main body 3 contracts due to cooling, since the hollow portion 3a is formed, the radial expansion of the hollow portion 3a causes a pressure toward the radially outer side of the mandrel main body 3, and this pressure causes the pipe material The inner peripheral surface of is cooled while receiving a pressing force. Therefore, it is possible to effectively perform mold clamping during cooling, and it is possible to obtain a molded product that is more homogeneous and has excellent quality.

Further, the restraining member 4 is removed from the used resin mandrel 1 and is heated at a temperature not lower than the crystallization temperature of the resin constituting the mandrel body 3 in a substantially unloaded state. It can be reused by cooling to temperature. Resin mandrel 1 is core 2
Therefore, the mandrel body 3 is prevented from being unnecessarily reduced in size during the reuse process.

As described above, according to the present invention, a plurality of hollow portions 3a penetrating along the longitudinal direction of the mandrel body 3 are provided in the circumferential direction thereof, and the core body 2 is expanded in the longitudinal direction of both ends of the mandrel body 3. Since the restraining member 4 for restraining the heat is detachably provided, it is possible to restrain the thermal expansion in the longitudinal direction and to thermally expand only in the radial direction, and limit the quality of the composite material pipe as a molded product to the length. It can be greatly improved without being done. Further, since the mold can be clamped at the time of cooling, it is possible to make the composite material pipe having the thermoplastic resin as a matrix more homogeneous and excellent in quality.

Even if the restraining member 4 prevents expansion in the longitudinal direction, since the mandrel body 3 has a plurality of hollow portions 3a, a high expansion pressure is released to the hollow portions 3a. The destruction of the mandrel body 3 can be easily prevented. Further, even if an excessive pressure is generated during heating, the pressure can be released to the cavity 3a, and the outer mold and the mandrel body 3 can be prevented from being broken.

Examples of the present invention will be described below more specifically together with comparative examples. Example 1 The mandrel body was made of PTFE, the outer diameter was 43 mm, the inner diameter was 18 mm, the length in the longitudinal direction was 100 mm, and the cavities that penetrated were 6 mm, and the cavities were equally spaced as shown in FIG.
0 pieces were formed. This mandrel body is made of iron with a total length of 110
A resin mandrel was constructed by connecting ten cores of 0 mm in a state of being in close contact with each other. Therefore, the effective length of this resin mandrel is 1
It has become m. The restraining member is made of iron with a thickness of 3 mm and has an outer diameter of 42 mm and an inner diameter of 18 mm.

Then, according to a standard method, a preform of a pipe made of a composite material is molded by a PEEK (polyether ether kent) / CF (carbon fiber) prepreg (APC-2 / AS4 ICI-Fiberite).
After being inserted into an outer mold made of copper and the resin mandrel being inserted, restraining members were fixedly attached to both ends of the mandrel body via a core body. The outer diameter of the outer mold was 55 mm and the length of the preform was 1000 mm, which was made to match the effective length of the resin mandrel.
The stacking is repeated ± 30 ° 10 times and the wall thickness is 2.5.
It is wound to be mm.

Subsequently, after heating in an oven at 380 ° C. for 120 minutes, it was cooled in cooling water to obtain a PEEK / CF composite material pipe. The inner peripheral surface of the pipe was not deformed due to displacement of the pipe material, etc., and a good and high-quality composite material pipe with no defects in appearance could be obtained. Comparative Example-1 The same as Example 1 except that the mandrel body was not provided with hollow portions penetrating both ends thereof.

During the heat molding, the mandrel body was thermally expanded, and since the cavity was not formed, the mandrel body resin was extruded while being deformed and destroyed from the end of the mandrel body. Therefore, the resin mandrel is destroyed and cannot be reused, and both ends of the molded product are about 10 cm.
The wall thickness fluctuated over time, and a good composite material pipe could not be obtained. Comparative Example 2 The mandrel body was made of PTFE and was formed to have an outer diameter of 45 mm, an inner diameter of 18 mm, and a length of 100 mm in the longitudinal direction without providing a hollow portion penetrating both ends. A resin mandrel was constructed by connecting eight of the mandrel bodies in a state of closely adhering to the same core body as in Example 1. Therefore, the effective length of this resin mandrel is 8
It is 00 mm. Further, a restraining member that restrains thermal expansion in the longitudinal direction of the mandrel body is not provided.
After that, the same procedure as in Example 1 was followed.

The resin mandrel expands during the heat molding,
A 00 mm length of PEEK / CF composite pipe was molded. Generally, it was a good molded product with no problem in appearance, but at one end the prepreg layer on the inner surface was extruded partly out of the product, and the fiber orientation was disturbed and a decrease in wall thickness was observed. And some problems occurred. Although such a problem does not always occur in all cases, it has been confirmed that it often appears when the resin mandrel moves a considerable distance (in this case, 100 mm at each end).

The reason why the PTFE mandrel body which is slightly larger than that of Example 1 is used is that the PTFE mandrel body of the same size has a slightly insufficient expansion and weak mold clamping. This is because, although the thin mandrel body made of PTFE is used in Example-1, the thermal expansion in the longitudinal direction is suppressed, and the thermal expansion corresponding to that increases the radial expansion. Example-2 The restraining member was removed from the resin mandrel used in Example-1, and the core was supported and heated in an oven at a temperature of 380 ° C for 60 minutes. The strain on the mandrel body after heating was removed and the mandrel body had a natural shape (that is, it expanded equally in the radial direction and the axial direction). Do this at a rate of 2 ° C / min
The temperature was gradually reduced to ℃. As a result, the distortion of the mandrel body was removed, and the mandrel body was lined up with a gap on the core body in a state where it was almost returned to the state before use. When this gap was filled and rearranged, a restraining member was attached, and molding was repeated again under the same conditions as in Example-1, a similarly good and high-quality composite material pipe could be obtained.

[0028]

The present invention is constructed as described above, and a plurality of hollow portions are provided in the mandrel body so as to penetrate the mandrel body along the longitudinal direction of the mandrel body. Since the restraining member that restrains expansion in the longitudinal direction of the body is provided detachably, the mandrel body can be thermally expanded only in the radial direction without being destroyed, and the pipe material during heat molding can be There is an effect that the quality of the composite material pipe, which is a molded product, can be significantly improved without being affected by the movement due to the elongation in the longitudinal direction and the length is not limited.

Further, although the mandrel body shrinks during cooling, since the hollow portion is formed, a pressure toward the radially outer side of the mandrel body is generated as the hollow portion expands in the radial direction. Since the inner peripheral surface of is cooled while receiving a pressing force, it is possible to effectively perform mold clamping during cooling, and it is possible to obtain a molded product that is more homogeneous and has excellent quality.

[Brief description of drawings]

FIG. 1 is a perspective view of a resin mandrel according to the present invention.

FIG. 2 is a cross-sectional view of FIG.

FIG. 3 is a side view of the mandrel body.

FIG. 4 is a cross-sectional view of a conventional resin mandrel.

[Explanation of symbols]

 1 Resin Mandrel 2 Core 3 Mandrel Main Body 3a Cavity 4 Suppression Member

Claims (1)

[Claims] 1. A resin mandrel in which a mandrel body made of a heat-expandable resin is mounted on a rod-shaped core body, and a plurality of cavities penetrated in the circumferential direction of the mandrel body along the longitudinal direction of the core body. A resin mandrel, wherein the resin mandrel is detachably attached to the core body, and a restraining member that restrains both ends of the mandrel body from expanding in the longitudinal direction of the core body is provided.