Method for manufacturing fiber-reinforced resin bolt and fiber-reinforced resin bolt

Provided is a fiber-reinforced resin bolt having a strength higher than that of a conventional fiber-reinforced resin bolt. A fiber-reinforced resin bolt 1 formed by a winding step of winding a CFRP resin tape 14, which is formed in a band shape by integrating CFRP 12 with a thermosetting resin in such a manner that the CFRP 12 is oriented in a longitudinal direction, so that the CFRP 12 is arranged concentrically around a winding axis, thereby forming a CFRP resin tape layer 10; and a curing step of placing the CFRP resin tape layer 10 formed by the winding step in a die 40 whose inner wall surface is formed with a screw shape, pressurizing the die 40 in which the CFRP resin tape layer 10 is placed from one direction of the winding axis to the other, and heating the die 40 with a heater 82, thereby curing the resin containing the CFRP resin tape layer 10.

TECHNICAL FIELD

The present invention relates to a high-strength bolt including a reinforcing fiber and a resin material.

BACKGROUND ART

As a conventional fiber-reinforced resin bolt, there is a fiber-reinforced resin bolt obtained by press-forming a rod-shaped material obtained by incorporating, into a synthetic resin, long fibers of carbon fiber or the like in such a manner that the fibers are arranged in the longitudinal direction, wherein at least the long fibers in a straight part are arranged linearly along the axial direction at outer peripheral parts of the fiber-reinforced resin bolt and arranged in a bent shape at an axial center part thereof (for example, Patent Document 1).

PRIOR ART DOCUMENTS

Patent Document

Patent Document 1: JP H06-185514 A

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

However, the conventional fiber-reinforced resin bolt described above has a structure in which the long fibers in the straight part are linearly arranged along the axial direction at the outer peripheral parts and arranged in a bent shape at the axial center part, and thus involves a problem of insufficient strength as a bolt.

The present invention has been made in view of such a problem, and an object thereof is to provide a method for manufacturing a fiber-reinforced resin bolt having a strength higher than that of a conventional fiber-reinforced resin bolt, and a fiber-reinforced resin bolt.

Means for Solving the Problem

Application Example 1

A method for manufacturing a fiber-reinforced resin bolt according to the present invention includes forming a fiber-reinforced resin bolt (1) by:

a winding step of winding a reinforcing fiber resin tape (14), which is formed in a band shape by integrating a reinforcing fiber (12) with a resin in such a manner that the reinforcing fiber (12) is oriented in a longitudinal direction, so that the reinforcing fiber (12) is arranged concentrically around a winding axis, thereby forming a reinforcing fiber resin tape layer (10); and

a curing step of placing the reinforcing fiber resin tape layer (10) formed by the winding step in a die (40) whose inner wall surface is formed with a screw shape, and pressurizing the reinforcing fiber resin tape layer (10) placed in the die (40) from one direction of the winding axis toward the other, thereby curing the resin of the reinforcing fiber resin tape layer (10).

In such a method for manufacturing a fiber-reinforced resin bolt, the reinforcing fiber resin tape (14) is wound concentrically around the winding axis to form the reinforcing fiber resin tape layer (10).

Then, in a state of being placed in the die (40), the formed reinforcing fiber resin tape layer (10) is pressurized from one direction of the winding axis toward the other to cure the resin of the reinforcing fiber resin tape layer (10) (curing step).

Here, upon pressurization of the reinforcing fiber resin tape layer (10), the reinforcing fiber layer extends spirally in the winding axis direction to form a reinforcing fiber layer (70).

The inner wall surface of the die (40) is formed with a screw shape, and the reinforcing fiber resin tape layer (10) is placed in the die (40) so that its winding axis is parallel to the inner wall surface formed with a screw shape. Therefore, when the resin is cured, a screw is formed on its outer wall surface.

The fiber-reinforced resin bolt (1) manufactured by such a manufacture method has, inside the cured resin, the reinforcing fiber layer (70) wound spirally around the winding axis.

When such a fiber-reinforced resin bolt (1) is used, axial tensile force and circumferential bending force are applied to the fiber-reinforced resin bolt (1). The tensile force and the bending force are received by the reinforcing fiber (12). Since the reinforcing fiber layer (70) is formed spirally, both the tensile force and the bending force are received by the reinforcing fiber (12).

Therefore, the fiber-reinforced resin bolt (1) can have a strength higher than that of a conventional bolt in which the reinforcing fiber is arranged only in the axial direction.

Application Example 2

The method for manufacturing a fiber-reinforced resin bolt according to Application Example 1 includes, after the winding step, a bending step of bending the reinforcing fiber resin tape layer (10) formed by the winding step with respect to an axis parallel to the winding axis.

According to such a method for manufacturing a fiber-reinforced resin bolt, the reinforcing fiber resin tape layer (10) formed by the winding step is further bent in an axis parallel to the winding axis by the bending step. Therefore, the formed reinforcing fiber resin tape layer (10) has a more multilayered structure, and thus it is possible to manufacture a fiber-reinforced resin bolt (1) having a higher strength.

Furthermore, even if the diameter of the reinforcing fiber resin tape layer (10) to be formed by winding is increased in the winding step, the reinforcing fiber resin tape layer (10) having an appropriate diameter can be formed by the subsequent bending step. Therefore, the winding step can be facilitated.

Application Example 3

A method for manufacturing a fiber-reinforced resin bolt according to the present invention includes forming a fiber-reinforced resin bolt (1) by:

a winding step of winding a reinforcing fiber tape (62), which is formed in a band shape in such a manner that a reinforcing fiber (12) is oriented in a longitudinal direction, so that the reinforcing fiber (12) is arranged concentrically around a winding axis, thereby forming a reinforcing fiber tape layer (60);

a resin injection step of placing the reinforcing fiber tape layer (60) formed by the winding step in a die (40) whose inner wall surface is formed with a screw shape, and injecting a resin into the die (40) in which the reinforcing fiber tape layer (60) is placed; and a curing step of pressurizing the die (40) into which the resin is injected by the resin injection step from one direction of the winding axis toward the other, thereby curing the resin containing the reinforcing fiber tape layer (60).

In such a method for manufacturing a fiber-reinforced resin bolt, the reinforcing fiber tape (62) is wound concentrically around the winding axis to form the reinforcing fiber tape layer (60).

Then, the formed reinforcing fiber tape layer (60) is placed in the die (40), and the resin is injected (resin injection step). The die (40) into which the resin is injected is pressurized from one direction of the winding axis to the other to cure the resin containing the reinforcing fiber tape layer (60) (curing step).

Here, the reinforcing fiber tape layer (60), when heated and pressurized, extends spirally in the winding axis direction. The inner wall surface of the die (40) is formed with a screw shape, and the reinforcing fiber tape layer (60) is placed in the die (40) so that its winding axis is parallel to the inner wall surface formed with a screw shape. Therefore, when the resin is cured, a screw is formed on its outer wall surface.

The fiber-reinforced resin bolt (1) manufactured by such a manufacture method can have a strength higher than that of a conventional bolt in which the reinforcing fiber is arranged only in the axial direction, similarly to the fiber-reinforced resin bolt (1) in Application Example 1.

Application Example 4

The method for manufacturing a fiber-reinforced resin bolt according to Application Example 3 includes, after the winding step, a bending step of bending the reinforcing fiber tape layer (60) formed by the winding step with respect to an axis parallel to the winding axis. The resin injection step includes placing the reinforcing fiber tape layer (60) formed by the bending step in a die (40) whose inner wall surface is formed with a screw shape, and injecting a resin into the die (40) in which the reinforcing fiber tape layer (60) is placed.

According to such a method for manufacturing a fiber-reinforced resin bolt, the same effect as that of Application Example 3 can be obtained.

Application Example 5

A fiber-reinforced resin bolt (1) according to the present invention includes:

a reinforcing fiber layer (70) in which a reinforcing fiber (12), which is formed in a band shape in such a manner that the fiber is oriented in a longitudinal direction, is formed in a state where the reinforcing fiber (12) is wound spirally around a central axis;

a resin layer (20) containing the reinforcing fiber layer (70); and

a screw part (30) formed on an outer peripheral surface thereof by heating and pressurization in a state where the reinforcing fiber layer (70) is contained in the resin layer (20).

Such a fiber-reinforced resin bolt (1) can have a strength higher than that of a conventional bolt in which the reinforcing fiber is arranged only in the axial direction, similarly to the fiber-reinforced resin bolt (1) manufactured by the method for manufacturing a fiber-reinforced resin bolt according to Application Example 1.

Application Example 6

In the fiber-reinforced resin bolt (1) according to Application Example 3, the reinforcing fiber (12) is carbon fiber-reinforced plastic.

In such a fiber-reinforced resin bolt (1), carbon fiber-reinforced plastic is used as the reinforcing fiber (12). Thus, the fiber-reinforced resin bolt (1) can be lightweight and have a high strength.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments to which the present invention is applied will be described with reference to the drawings. It should be noted that the embodiments of the present invention are not limited to the following embodiments at all, and can take various forms within the technical scope of the present invention.

First Embodiment

A method for manufacturing a fiber-reinforced resin bolt1(hereinafter, also referred to simply as “bolt1”) will be described with reference toFIGS.1to4. In the present embodiment, carbon fiber-reinforced plastic (hereinafter, also referred to as “CFRP12”) is used as a reinforcing fiber12.

First, as shown inFIG.1(a), a CFRP resin tape14, which is formed in a band shape by integrating CFRP12with a predetermined amount of resin in such a manner that the fiber is oriented in the longitudinal direction, is wound concentrically around a winding axis as shown inFIG.1(b)(plan view) andFIG.1(c)(side view), thereby forming a ring-shaped CFRP resin tape layer10(winding step). At this time, the CFRP resin tape14is wound around the winding axis with as little gap as possible.

Here, the phrase “integrating CFRP with a predetermined amount of resin” means that long fibers of CFRP are arranged in a band shape, immersed in the resin for solidification, and formed in a tape shape. The amounts of CFRP and resin at this time are the amount of CFRP necessary for attaining a predetermined strength of the bolt1, and determined by the amount of resin necessary for forming a screw part30as the bolt1(amount of resin after winding) or the type of thermosetting resin.

In the present embodiment, a thermosetting resin such as vinyl ester is used as the resin. Furthermore, the proportions of the CFRP12and the thermosetting resin are 50% to 60% by weight and 50% to 40% by weight, respectively, and, particularly in the present embodiment, were set to 57% by weight for the CFRP12and 43% by weight for the thermosetting resin.

FIGS.1(a) and1(c)are conceptualized in order to show fibers of the CFRP12. InFIG.1(b), gaps are drawn larger than the actual size for easy understanding of the laminated state of the wound CFRP resin tape14.

Next, electric power is supplied to a heater82of a die40to preheat the die40(about 90° C. in the case of vinyl ester) so as to attain a temperature lower than the curing temperature of the thermosetting resin.

Next, as shown inFIG.2, the CFRP resin tape layer10formed in a ring shape is placed in a portion close to a cylindrical part44of a screw part46of the die40so that the winding axis substantially matches the axial direction of the screw part46of the die40.

As shown inFIGS.3(a) and3(b), the die40has a shape formed by halving a metal block made of a SUS material or the like (one half is defined as a die40a, and the other half is defined as a die40b). The dies40aand40bcan be integrated with a bolt41and a nut42. In addition, the inner surfaces of the dies40aand40beach having a halved shape have an outer diameter shape of the bolt1.

InFIG.3,FIGS.3(a) and3(b)are line-symmetric with respect to a chain double-dashed line A-A′.

That is, as shown inFIG.3(a), the die40ahas a die shape for forming a head part43a, a cylindrical part44a, an incomplete screw part45a, and a screw part46aof the bolt1. Further, an insertion hole47a, which is a hole for inserting an insertion part51of the insertion tool50for compressing the resin, is provided at one end of the die40.

In the die40b, a head part43b, a cylindrical part44b, an incomplete screw part45b, a screw part46band an insertion hole47bhaving the same shapes as those of the die40aare formed at line-symmetric positions of the die40b. Hereinafter, a hole formed by the insertion hole47aand the insertion hole47bis referred to as an insertion hole47.

Further, the die40ais provided with four through holes49afor integrating the die40awith the die40bwith the bolts41and the nuts42and two pins48afor positioning at the time of integration.

The die40bis provided with four through holes49band two holes48bfitted with two pins48a, respectively, at line-symmetric positions of the die40a.

Furthermore, two (a total of four as the die40) heaters82are embedded in the dies40aand40b, respectively, so that the die40can be heated by supplying power to the heaters82from the external.

The CFRP resin tape layer10is placed in the die40, the halved dies40are integrated with the bolts41and the nuts42, and the insertion tool50is inserted into the insertion hole47as shown inFIG.4(a). The insertion tool50is made of a metal such as a SUS material, and includes the insertion part51having an outer diameter slightly smaller than the diameter of the insertion hole47, and a columnar head part52provided at one end of the insertion part51.

Then, as shown inFIG.4(b), in a state where the insertion part51of the insertion tool50is inserted into the insertion hole47, the die40is mounted on a bolster plate80of a pressing machine with the head part52up. The resin in the die40is pressurized by depressing the head part52with a slide81of the press machine, and then power is supplied to the heaters82so that the temperature of the die40(that is, the temperature of the resin, about 150° C. in the case of vinyl ester) is raised to the curing temperature of the resin, thereby curing the resin (curing step).

After completion of the curing step, the power supply to the heaters82is stopped. The nuts42of the die40are loosened, the die40is disassembled, and the bolt1is removed from the die40.

The fiber-reinforced resin bolt1manufactured by such a manufacture method includes a resin layer20, the screw part30, a head part31, a cylindrical part32, and an incomplete screw part33, as shown inFIG.5(a). Further, the fiber-reinforced resin bolt1is formed such that the CFRP resin tape layer10formed in a ring shape by the winding step is pushed in the winding axis direction inside the die40, by pressurization in the curing step, to be in a spiral shape.

Therefore, the fiber-reinforced resin bolt1has, inside the cured resin layer20, a CFRP layer70wound spirally around the winding axis.FIG.5(a)shows a cross-sectional photograph of the entire actual fiber-reinforced resin bolt1, andFIG.5(b)shows an enlarged cross-section photograph of the screw part30of the fiber-reinforced resin bolt1.

As shown inFIGS.5(a) and5(b), it can be seen that the CFRP layer70is formed over the entire inside of the resin layer20of the fiber-reinforced resin bolt1.

The CFRP12receives the axial tensile force and circumferential bending force applied to such a fiber-reinforced resin bolt1. Since the CFRP layer70has a spiral shape, the CFRP12receives both the tensile force and the bending force.

Therefore, the fiber-reinforced resin bolt1can have a strength higher than that of a conventional bolt in which the reinforcing fiber is arranged only in the axial direction.

Further, in the fiber-reinforced resin bolt1, CFRP (carbon fiber-reinforced plastic) is used as the reinforcing fiber12. Thus, the fiber-reinforced resin bolt1can be lightweight and have a high strength.

Here,FIG.6shows the results of a tensile break test performed on the fiber-reinforced resin bolt1of M8 size, a RENY (registered trademark) bolt (50% glass fiber-reinforced polyamide MXD6 bolt) and a PEEK bolt (polyetheretherketone bolt) by a test method in conformity with JIS B 1051. As described above, the fiber-reinforced resin bolt1includes 57% by weight of the CFRP12and 43% by weight of the thermosetting resin.

As shown inFIG.6(a)andFIG.6(b), the fiber-reinforced resin bolt1exhibits a tensile breaking load at which the bolt breaks of 14346.3 [N], and thus can have a tensile break strength which is about 2.4 times higher than the tensile breaking load, 6023.5 [N], of the conventional RENY bolt and about 4.5 times higher than the tensile breaking load, 3158.6 [N], of the conventional PEEK bolt.

Second Embodiment

Next, a second embodiment in which the carbon fiber content rate and resin content rate of the fiber-reinforced resin bolt1are changed will be described. The material and manufacture method for the fiber-reinforced resin bolt1in the second embodiment are the same as those for the fiber-reinforced bolt1in the first embodiment, and thus descriptions thereof will be omitted.

FIG.7shows the results of a tensile break test on the fiber-reinforced resin bolt1when the carbon fiber content rate and the resin content rate are changed. The tensile break test was performed by the test method in conformity with JIS B 1051, as in the case shown inFIG.6.

The fiber-reinforced resin bolt1of M3 size was used as a test body to perform the tensile break test in the following three cases:Case No. 1: carbon fiber content rate: 43.8% and resin content rate: 56.2%Case No. 2: carbon fiber content rate: 50.9% and resin content rate: 49.1%Case No. 3: carbon fiber content rate: 56.4% and resin content rate: 43.6%,

as shown inFIG.7(a).

As shown inFIGS.7(a) and7(b), the tensile break strength of the fiber-reinforced resin bolt1is as follows: the tensile breaking load is 2030 [N] in Case No. 1, 2370 [N] in Case No. 2, and 2042 [N] in Case No. 3.

In contrast, the conventional M3 RENY bolt exhibits a tensile breaking load of 762 [N], and it can be seen that the fiber-reinforced resin bolt1has a tensile break strength which is about 2.7 to 3.1 times higher than that of the RENY bolt.

In addition, the conventional M3 PEEK bolt exhibits a tensile breaking load of 430 [N], and it can be seen that the fiber-reinforced resin bolt1has a tensile break strength which is about 4.7 to 5.5 times higher than that of the PEEK bolt.

From the above, it can be seen that a sufficient tensile break strength can be obtained even when the proportions of the CFRP12and the thermosetting resin are 40% to 60% by weight and 60% to 40% by weight, respectively.

Third Embodiment

Next, a third embodiment in which a bending step is added after the winding step in the first embodiment will be described.

In the winding step in the third embodiment, unlike the winding shape of the CFRP resin tape14in the first embodiment, the CFRP resin tape14is concentrically wound around the winding axis so as to have a diameter of several centimeters, thereby forming the ring-shaped CFRP resin tape layer10.

As a winding method at this time, the CFRP resin tape14is wound around a columnar or cylindrical bar material90as shown inFIG.8(a)or two rod-shaped bar materials91aand91barranged in parallel as shown inFIG.8(b).

In the bending step, as shown inFIG.8(c), the ring-shaped CFRP resin tape layer10formed by the winding step is collapsed from the lateral direction into a band shape. The band-shaped CFRP resin tape layer10is pinched, at its one end, by two thin metal rods92aand92b, and wound concentrically around an axis of the metal rod92aas shown by arrows inFIGS.8(c) and8(d). By doing so, it is possible to form the CFRP resin tape layer10having a larger number of layers.

The curing step in the third embodiment is the same as that in the first embodiment, and a description thereof will be omitted.

The fiber-reinforced resin bolt1manufactured by the manufacture method including the above-described steps has an improved strength (tensile breaking load) as a bolt because the CFRP layer60is further multilayered.

Furthermore, even if the diameter of the CFRP resin tape layer10to be formed by winding is increased in the winding step, the CFRP resin tape layer10having an appropriate diameter can be formed by the subsequent bending step. Therefore, the winding step can be facilitated.

Fourth Embodiment

Next, the fiber-reinforced resin bolt1using a CFRP tape62instead of the CFRP resin tape14will be described.

While the CFRP resin tape14is formed in a band shape by integrating the CFRP fiber with the predetermined amount of resin so that the CFRP fiber is oriented in the longitudinal direction, the CFRP tape62is formed by arranging long fibers of CFRP in such a manner that the fibers of CFRP are oriented in the longitudinal direction and bundling them, or forming a fiber bundle into a band shape with a small amount of resin.

The winding step in a fourth embodiment is the same as that in the first embodiment except that the CFRP tape layer60is formed using the CFRP tape62instead of forming the CFRP resin tape layer10using the CFRP resin tape14, and a detailed description thereof will be omitted.

After the CFRP tape layer60is placed in this die40, the halved dies40are integrated with the bolts41and the nuts42, and a thermosetting resin such as vinyl ester is injected into the die40from the insertion hole47.

After injection of the resin into the die40, the insertion tool50is inserted into the insertion hole47as in the first embodiment. In this state, the resin within the die40is pressurized by depressing the head part52with a slide81of the pressing machine, and, at the same time, power is supplied to the heaters82to heat the die40, thereby curing the resin.

After completion of the curing step, the nuts42of the die40are loosened, the die40is disassembled, and the bolt1is removed from the die40.

The fiber-reinforced resin bolt1manufactured by such a manufacture method has similar structure and performance to those of the first embodiment (seeFIGS.5and6).

Fifth Embodiment

Next, a fifth embodiment will be described. The fifth embodiment is an embodiment in which a bending step is added to the fourth embodiment, similarly to the third embodiment (a bending step is added after the winding step in the first embodiment). In this case, the steps are the same as those of the third embodiment except that the CFRP tape62is used in place of the CFRP resin tape14used in the third embodiment, and thus a detailed description thereof is omitted (seeFIG.8).

The fiber-reinforced resin bolt1manufactured by the manufacture method according to the fifth embodiment has similar structure and performance as those of the fiber-reinforced resin bolt1manufactured by the manufacture method according to the third embodiment. Further, as is the case with the third embodiment, the winding step can be facilitated.

Other Embodiments

(1) In the above embodiments, CFRP (carbon fiber-reinforced plastic) is used as the reinforcing fiber12. However, instead of CFRP, an inorganic fiber-based reinforcing fiber such as glass fiber-reinforced plastic (GFRP) or an organic fiber-based reinforcing fiber such as aramid fiber-reinforced plastic (AFRP) may be used.

(2) In the above embodiments, a thermosetting resin such as vinyl ester is used as the resin. However, a thermoplastic resin such as PEEK (polyetheretherketone) or Teflon (registered trademark) may be used. In that case, it is not necessary to heat the die40up to the thermosetting temperature in the curing step.

(3) In the above embodiments, in the bending step of forming the CFRP resin tape layer10and the CFRP tape layer60, the ring-shaped CFRP resin tape layer10and CFRP tape layer60are each collapsed from the lateral direction into a band shape, and wound concentrically around one end thereof as a central axis. However, the ring-shaped CFRP resin tape layer10and CFRP tape layer60may each be bent several times using the axis parallel to the winding axis as a bending axis. In other words, the CFRP resin tape layer10and the CFRP tape layer60may each be bent several times in a direction perpendicular to the orientation of the fibers of the CFRP12.

(4) In the above embodiments, the inner surface shape of the die40is indicated as an example of the outer shape of the bolt1. However, the shape is not limited to this, and may be any other shape such as a shape having no cylindrical part32.

(5) In the above embodiments, the heaters82are used to heat the die40. However, a method capable of heating the die40to the curing temperature of the thermosetting resin, for example, any other heating means of circulating a heated liquid inside the die40, winding a nichrome wire around the die40, or the like, may be used.

REFERENCE SIGNS LIST