CA2191241A1 - Fibre reinforced resin composite reinforcing material and method for producing the same - Google Patents
Fibre reinforced resin composite reinforcing material and method for producing the sameInfo
- Publication number
- CA2191241A1 CA2191241A1 CA002191241A CA2191241A CA2191241A1 CA 2191241 A1 CA2191241 A1 CA 2191241A1 CA 002191241 A CA002191241 A CA 002191241A CA 2191241 A CA2191241 A CA 2191241A CA 2191241 A1 CA2191241 A1 CA 2191241A1
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- Canada
- Prior art keywords
- reinforcing
- core portion
- composite bar
- fiber
- forming body
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/07—Reinforcing elements of material other than metal, e.g. of glass, of plastics, or not exclusively made of metal
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
- B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
- B29C70/06—Fibrous reinforcements only
- B29C70/10—Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres
- B29C70/16—Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres using fibres of substantial or continuous length
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
- B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
- B29C70/06—Fibrous reinforcements only
- B29C70/10—Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres
- B29C70/16—Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres using fibres of substantial or continuous length
- B29C70/20—Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres using fibres of substantial or continuous length oriented in a single direction, e.g. roofing or other parallel fibres
- B29C70/205—Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres using fibres of substantial or continuous length oriented in a single direction, e.g. roofing or other parallel fibres the structure being shaped to form a three-dimensional configuration
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- Engineering & Computer Science (AREA)
- Architecture (AREA)
- Textile Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Composite Materials (AREA)
- Mechanical Engineering (AREA)
- Civil Engineering (AREA)
- Structural Engineering (AREA)
- Moulding By Coating Moulds (AREA)
Abstract
A reinforcing fiber bundle impregnated with thermosetting resin twisted in a predetermined manner is tightly wound on a surface of the core portion of reinforcing fiber bundle impregnated with thermosetting resin so as to form a forming body. While this forming body is given a tension so that it can be strained by 500 to 3000 µ/m in the axial direction, the forming body is thermally cured. Alternatively, a forming body formed in such a manner that a reinforcing fiber bundle impregnated with thermosetting resin is wound round a twisted core portion is set in a curved type die curved at a predetermined radius of curvature, and the forming body is thermally cured so as to manufacture a curved reinforcing composite bar of fiber reinforced resin.
Due to the foregoing, it is possible to provide an inexpensive reinforcing composite bar of fiber reinforced resin of high mechanical strength, which is useful as a substitute material of the reinforcing steel bar or PC
steel wire.
Due to the foregoing, it is possible to provide an inexpensive reinforcing composite bar of fiber reinforced resin of high mechanical strength, which is useful as a substitute material of the reinforcing steel bar or PC
steel wire.
Description
2 1 9 1 24 l - 1 - NSC-C848/PCT-US,CA
DESCRIPTION
Reinforcing Composite Bar of Fiber Reinforced Resin and Manufacturing Method Thereof TECHNICAL FIELD
The present invention relates to a reinforcing composite bar of fiber reinforced resin used as a reinforcing bar embedded in a concrete product such as a concrete building or a concrete structure during its manufacturing process. The present invention also relates to a method of manufacturing the reinforcing composite bar of fiber reinforced resin.
BACKGROUND ART
Conventionally, the use of a reinforcing composite bar of fiber reinforced resin has been proposed as a substitute of a reinforcing steel bar or a PC steel wire.
This reinforcing composite bar of fiber reinforced resin is manufactured in such a manner that highly elastic and highly strong continuous fibers such as carbon fibers or aramid fibers are impregnated with thermosetting epoxy resin and the thus impregnated epoxy resin is thermally cured. Therefore, it is well known such a reinforcing composite bar of fiber reinforced resin is light and its mechanical strength is high and further it has a high anticorrosion property. As described above, the reinforcing composite bar of fiber reinforced resin is light and its mechanical strength is high and further it has a high anticorrosion property, and furthermore it can be cut with a wood working saw. Due to the above excellent properties of the reinforcing composite bar of fiber reinforced resin, it is expected that the use of the reinforcing composite bar of fiber reinforced resin will expand in the field of reinforcing bars to be embedded in various concrete products.
However, the following two big problems may be encountered in the use of the aforementioned conventional 2 1 ~ 1 24 1 reinforcing composite bar of fiber reinforced resin.
The first problem is described as follows. A surface of the reinforcing composite bar of fiber reinforced resin is flat, so that the adhesive property of the reinforcing composite bar to concrete is low and its tension transmitting property is deteriorated.
The second problem is described as follows. It is difficult to enhance the productivity of reinforcing composite bars of fiber reinforced resin. When consideration is given to the mechanical strength of reinforcing fibers, the proof strength of the reinforcing composite bar of fiber reinforced resin is actually limited to half of the mechanical strength of the reinforcing fibers.
In order to solve the first problem, various methods have been proposed. For example, the following five methods are conventionally known.
As disclosed in Japanese Unexamined Patent Publication No. 61-274036, the first method is to form protrusions around a core by winding a plurality of reinforcing fiber bundles around it, so that the adhesive force of the reinforcing composite bar to concrete can be ensured.
The second method is to make particulate matters adhere onto the core surface as disclosed in Japanese Unexamined Patent Publication No. 4-363454, or to make short fibers adhere onto the core surface as disclosed in Japanese Unexamined Patent Publication No. 2-248559.
The third method is to form mechanical dents directly on the core surface so that the adhesive force can be enhanced as disclosed in Japanese Unexamined Patent Publication Nos. 63-206548 and 63--219746.
The fourth method is to structurally engage reinforcing composite bars with concrete by curving a plurality of bars as disclosed in Japanese Unexamined Patent Publication No. 3-1514444. Also, the fourth method is to form irregularities on the core surface by waving the surface fibers with a die, on the inner surface of which irregularities are formed, as disclosed in Japanese Unexamined Patent Publication No. 2-248559.
The fifth method is to form irregularities on the core surface by forming fibers in the axial direction into braids so that the adhesive force of the reinforcing composite bar to concrete can be enhanced as disclosed in Japanese Unexamined Patent Publication No. 4-363454.
However, according to the third to the fifth method, the fibers in the core portion are made to wave, or the fibers in the core portion are mechanically damaged.
Accordingly, although the adhesive force of the reinforcing composite bar to concrete is enhanced, the mechanical strength of the core portion is lowered.
Therefore, from the viewpoint of manufacturing reinforcing composite bars of fiber reinforced resin of high mechanical strength, these methods are not appropriate.
In this case, in order to provide a required intensity of mechanical strength, it is necessary to increase a quantity of fiber. Accordingly, the cost is disadvantageously raised.
According to the second method, small particulate matters or short fibers, which are not continuously formed, are made to adhere onto the core surface only by the adhesive force after all. Therefore, it is impossible to ensure a sufficiently high intensity of adhesive force of the core portion to concrete.
It could be said that the first method described above is the best, because the first method is capable of manufacturing a reinforcing composite bar of fiber reinforced resin without deteriorating the fiber strength of the core portion. However, concerning the adhesive force of the reinforcing composite bar to concrete, the first method is inferior to the third to the fifth method described above.
As described above, according to the first to the fifth method, it is difficult to enhance the adhesion property of the reinforcing composite bar to concrete to a level corresponding to the adhesion property of the conventional reinforcing steel bar, without deteriorating the high intensity of fiber strength of the core portion.
A reinforcing composite bar of fiber reinforced resin, the mechanical strength of which corresponds to the mechanical strength of a reinforcing steel bar, has not been developed yet.
The present inventors made investigations into the above second problem and obtained the following results.
Concerning the drawing method (for example, disclosed in Japanese Unexamined Patent Publication Nos. 61-274036 and 2-248559) which has been proposed as a typical method of manufacturing the reinforcing composite bar of fiber reinforced resin, the drawing speed is determined in accordance with the drawing condition. Therefore, the productivity of the drawing method is limited, and further when a strong drawing force is applied to the reinforcing composite bar, a grip portion to grip the fiber bundle is damaged by the strong drawing force. Accordingly, it is impossible to apply a necessarily high intensity of tension to the bundle of reinforcing fibers.
In accordance with an expansion of the market of reinforcing composite bars of fiber reinforced resin, it is demanded to develop not only a straight rod-shaped reinforcing composite bar but also a curved reinforcing composite bar, the radius of curvature of which is determined to be a predetermined value according to the use of the reinforcing composite bar. For example, at present, attention is given to the high cutting property of reinforcing composite bars of fiber reinforced resin.
In the caisson method which is one of the pit excavation methods used in the excavation of an underground tunnel, a plan is made in which reinforcing composite bars of fiber reinforced resin are used for an opening portion of the pit instead of common reinforcing steel bars. The use of curved reinforcing composite bars of fiber reinforced resin is indispensable to this excavation method.
However, concerning the reinforcing composite bar of fiber reinforced resin, only a straight rod-shaped type reinforcing composite bar is known at present.
Accordingly, in order to provide a curved reinforcing composite bar of fiber reinforced resin, there is no other way except for forcibly bending the straight rod-shaped reinforcing composite bar by a mechanical means.
However, this reinforcing composite bar of fiber reinforced resin is made of a brittle material in which plastic deformation is not caused, which is different from metal. Further, a ratio of elongation of the reinforcing fiber is very low, that is, a ratio of elongation is 1 to 2% at most. For this reason, when this reinforcing composite bar of fiber reinforced resin is subjected to forcible bending by a mechanical means, a portion of the fibers are broken, that is, the reinforcing fibers are damaged. As a result, when a radius of curvature is small in the bending process, the mechanical strength of the reinforcing composite bar of fiber reinforced resin, which is originally high, is deteriorated. Even if the radius of curvature is large, a bending stress is generated in the process of bending, and a usable mechanical strength of the composite bar is inevitably lowered. In any case, the original high strength of the composite bar is deteriorated.
In general, when the resin matrix composite material is curved after it has been cured, it is inevitably subjected to a forcible bending processing. As a result, the above problem is caused. It is possible to adopt a bending method in which a straight rod-shaped composite bar is heated again to a temperature not less than 120-C, and the resin impregnated into a bundle of reinforcing fibers is softened, so that bending is conducted.
However, this method is disadvantageous because bending of the composite bar is conducted at high temperatures and this work requires much time and labor. Further, even in this method, the reinforcing fibers are buckled and the mechanical strength is lowered. Therefore, it is impossible for the reinforcing composite bar of fiber reinforced resin to exhibit its original performance.
It is an object of the present invention to provide a reinforcing composite bar of fiber reinforced resin, the adhesive force to concrete of which is equal to or not less than the adhesive force of a metallic reinforcing bar to concrete without deteriorating the mechanical strength of the core portion.
It is another object of the present invention to provide a reinforcing composite bar of fiber reinforced resin in which the original strength of the reinforcing fibers can be fully utilized, so that a quantity of reinforcing fibers can be decreased and the production cost can be reduced, and further the proof strength can be ralsed.
It is still another object of the present invention to provide a method of manufacturing a reinforcing composite bar of fiber reinforced resin by which a reinforcing composite bar of fiber reinforced resin, the proof strength of which is high, can be manufactured at high productivity and low cost.
It is still another object of the present invention to provide a reinforcing composite bar of fiber reinforced resin of high mechanical strength which is curved by a predetermined radius of curvature, and the dimensional accuracy of which is high.
It is still another object of the present invention to provide a method of easily manufacturing a reinforcing composite bar of fiber reinforced resin of high mechanical strength which is curved by a predetermined radius of curvature, and the dimensional accuracy of which is high, wherein the mechanical strength is not deteriorated in the manufacturing process.
DISCLOSURE OF THE INVENTION
In order to solve the above problems, the present inventors made investigations in earnest and found the following.
Concerning the first problem, in the case of a reinforcing composite bar of fiber reinforced resin having a core portion on which protrusions are formed, when reinforcing fiber bundles composing the protrusions on the surface of the core portion are twisted, it is possible to enhance an intensity of the adhesive force of the reinforcing composite bar to concrete without deteriorating the mechanical strength of the core portion.
Concerning the second problem, when the core portion and the protrusions are successively formed into a forming body and the thus obtained forming body is thermally cured while a tension is given to the forming body in the axial direction (in the direction of a reinforcing fiber bundle), so that the reinforcing fibers can be arranged in the same direction without giving a tension to the peripheral resin (since the resin is easily damaged when a tensile stress is given, only a compressive stress is given to the resin), it is possible to utilize the original high mechanical strength and high elasticity of the reinforcing resin. Due to the foregoing, it is possible to manufacture a reinforcing composite bar of fiber reinforced resin, the proof strength of which is high, at a high production efficiency.
In order to curve a reinforcing composite bar of fiber reinforced resin without deteriorating its mechanical strength, it is effective that the reinforcing composite bar of fiber reinforced resin is subjected to thermal curing processing under the condition that the core portion of the reinforcing composite bar is twisted and the forming body composed of the core portion and the protrusions is curved and also under the condition that the core portion is given a predetermined intensity of tensile stress. When the core portion is given a tensile stress, each unit fiber composing the core portion is substantially equally given a tensile stress.
21~1241 Accordingly, even if the core portion is curved while it is twisted, the local buckling of the forming body and the deterioration of mechanical strength can be completely avoided.
The present invention will be further explained as follows.
The present invention is to provide a reinforcing composite bar of fiber reinforced resin composed of a forming body comprising: a core portion and a winding portion to form protrusions on a surface of the core portion, both potions being made of thermosetting material containing thermosetting resin and reinforcing fiber bundles, wherein the forming body is strained by 500 to 3000 ~/m when a tension is applied to the forming body.
In order to manufacture the above reinforcing composite bar, for example, a filament winding device is used; jigs having a plurality of pins are attached to both end chuck portions of the filament winding device;
reinforcing fiber bundles impregnated with thermosetting resin are arranged between the pins of a pair of jigs so as to form a core portion by the filament winding method;
a reinforcing fiber bundle impregnated with thermosetting resin is tightly wound on the circumferential surface of this core portion so as to form protrusions; and the thus obtained forming body is subjected to thermosetting processing while a tension is given to the obtained forming body in the axial direction. Alternatively, the reinforcing fiber bundle forming the above protrusions is given a predetermined twist.
Due to the above construction, the reinforcing composite bar of the present invention has a high tensile strength in which the original mechanical strength of the reinforcing fiber is exhibited, and the adhesive force of the reinforcing composite bar to concrete can be greatly enhanced while the fibers are prevented from being damaged.
Further, the present invention is to provide a curved g reinforcing composite bar of fiber reinforced resin, the overall shape of which is curved by a predetermined radius of curvature, comprising: a core portion made of reinforcing fiber bundles impregnated with thermosetting resin; and protrusions formed when a reinforcing fiber bundle impregnated with thermosetting resin is tightly wound round the core portion.
In order to manufacture the above reinforcing composite bar, first, the core portion is formed; this core portion is twisted; protrusions are formed by at least one reinforcing fiber bundle impregnated with thermosetting resin; the thus obtained core member having protrusions, that is, a forming body is fixed in a curved mold which is curved by a predetermined radius of curvature; and the thermosetting resin impregnated into the above reinforcing fiber bundle is thermally set while a predetermined intensity of tensile stress is given to the core portion.
Another method is described as follows. Protrusions are formed on a formed core portion by at least one reinforcing fiber bundle impregnated with thermosetting resin; the core portion is twisted in the same direction as that of the thus formed protrusions; the thus obtained core member having protrusions, that is, a forming body is fixed in a curved mold which is curved by a predetermined radius of curvature; and thermosetting resin impregnated into the above reinforcing fiber bundle is thermally set while a predetermined intensity of tensile stress is given to the core portion.
The curved reinforcing composite bar of fiber reinforced resin manufactured in this way is very suitable for the reinforcing bars used for the excavation of a pit in the construction work of sewerage, subway and so forth.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a partially cutaway front view of a jig used in the filament winding method.
Fig. 2 is a schematic illustration showing a concept - lo - 2191241 of the filament winding method.
Fig. 3 is a partially perspective view of a metallic stationary die.
Fig. 4 is a partially front view showing a reinforcing composite bar of fiber reinforced resin of an example of the present invention.
Fig. 5 is a partially front view showing a reinforcing composite bar of fiber reinforced resin of Comparative Example 1.
Fig. 6 is a partially cross-sectional front view showing a reinforcing composite bar of fiber reinforced resin of Comparative Example 3.
Fig. 7 is a partially cross-sectional front view showing a method of the tensile test.
Fig. 8 is a graph showing a relation between the average adhesive stress intensity and the amount of slippage obtained in the tensile test.
Fig. 9 is a partially cross-sectional perspective view showing a rod-shaped test piece used in the tensile test in the example of the present invention and also used in the tensile test in the comparative example.
Fig. 10 is a partially perspective view showing a state of forming a curved reinforcing composite bar of fiber reinforced resin of another example of the present invention.
Fig. 11 is a partially perspective view showing a curved reinforcing composite bar of fiber reinforced resin of another example of the present invention.
BEST MODE OF CARRYING OUT THE INVENTION
First, a straight reinforcing composite bar of fiber reinforced resin of the present invention will be explained below.
Concerning the reinforcing fiber used for forming the reinforcing fiber bundle in the present invention, as long as they are fibers which continue from a leading end to a trailing end of the reinforcing composite bar to be manufactured, any conventional fibers may be used. For example, various carbon fibers such as PAN-based (polyacrylonitrile-base), pitch-based and hybrid carbon fibers may be used, and further aramid fibers and glass fibers may be also used. Concerning the thermosetting resin (reinforcing resin) impregnated into the reinforcing fiber bundle, any conventional thermosetting resin may be appropriately used. Usable examples of thermosetting resins are: epoxy resin, phenol resin, and polyamide resin. These reinforcing fibers and thermosetting resin may be appropriately selected in accordance with the use of the reinforcing composite bar to be manufactured.
However, from the viewpoint of heat resistance and resistance to corrosion, epoxy resin is preferably used as thermosetting resin.
Concerning the formation of the core portion in the present invention, only from the viewpoint of improving the adhesive property of the reinforcing composite bar to concrete, a hand-lay-up method may be adopted, in which the carbon fiber yarn impregnated with thermosetting resin is used as a core, and the carbon fiber prepreg impregnated with thermosetting resin is tightly wound round the core. Alternatively, a method may be adopted in which a plurality of pieces of carbon fiber yarn impregnated with thermosetting resin are collected and pieces of braid yarn are tightly wound round the collected pieces of carbon fiber yarn by a braider. Further, a drawing method may be adopted. However, it is preferable to use the following method.
That is, in a filament winding device, which will be referred to as an "FW" device" hereinafter, jigs having a plurality of pins are attached to both end chuck portions of the filament winding device; reinforcing fiber bundles impregnated with thermosetting resin are arranged between the pins of a pair of jigs so as to form a core portion by the filament winding method, which will be referred to as "FW method" hereinafter; a reinforcing fiber bundle impregnated with thermosetting resin is tightly wound on a circumferential surface of this core portion so as to form protrusions; and the thus obtained forming body is subjected to thermosetting processing while a tension is given to the obtained forming body in the axial direction.
This method will be specifically explained below.
First, as shown in Fig. 1, there is prepared a jig 1 made of metal including: a holding portion 2 arranged on the base end side; a plurality of pins 3, the number of which is 2 to 10, arranged on the front end side; and a stationary portion 4 composed of a male screw 5 and a nut 6, arranged between the holding portion 2 and the pin 3.
As shown in Fig. 2, a pair of metallic jigs 1 are attached to both end chuck portions 8 of the filament winding device 7.
Next, a plurality of reinforcing fiber bundles 9 are continuously drawn out and made to pass in a resin bath 10 in which thermosetting resin is accommodated. In this resin bath 10, the reinforcing fiber bundles are impregnated with the thermosetting resin. Then, these reinforcing fiber bundles impregnated with thermosetting resin are repeatedly spread by a traverser 11 between the plurality of pins 3 attached to the pair of jigs 1 so that the diameter of the spread reinforcing fiber bundles can be a predetermined value. In this way, the core portion can be formed, in which the plurality of reinforcing fiber bundles impregnated with thermosetting resin are arranged in the axial direction.
Concerning the core portion formed in this way, it is necessary for the thermosetting resin, which has been impregnated into the reinforcing fiber bundles, to be maintained in a condition in which it is not cured, until protrusions are formed on the surfaces of the reinforcing bundles and thermally cured. In this case, the thermosetting resin may be maintained either in a condition in which it is not cured at all or in a condition referred to as "B stage" in which it is partially cured. It is preferable that the volume content of fiber of this core portion is 40 to 70%, and it is more preferable that the volume content of fiber of this core portion is 50 to 60~. When this volume content of fiber is lower than 40%, the resin becomes too full, and the excess resin drips in the process of curing. When this volume content of fiber is higher than 70~, the quantity of resin is insufficient, and there is a possibility of failure in the adhesion of the core portion to the protrusions.
As described above, when at least one reinforcing fiber bundle impregnated with thermosetting resin is successively wound on a surface of the core portion, protrusions are formed round the core portion, and the forming body composed of the core portion and protrusions can be made. In this case, impregnation of thermosetting resin into the reinforcing fiber bundles and winding of the reinforcing fiber bundles round the core portion may be continuously conducted with the FW device in the process of forming the core portion. Alternatively, it may be conducted when reinforcing fiber bundles previously impregnated with thermosetting resin are brought in from the outside.
In this case, the thermosetting resin impregnated into the reinforcing fiber bundles for forming protrusions and its volume content of fiber may be the same as those of the core portion described before.
In order to improve the adhesive force of the reinforcing composite bar to concrete, it is preferable that the reinforcing fiber bundles impregnated with thermosetting resin are twisted by 10 to 50 turns per meter and tightly wound round the core portion at an angle of 65 to 85- with respect to the axial direction or the core portion.
When the number of turns of twist given to the reinforcing fiber bundles composing the protrusions is smaller than 10 turns per meter, the adhesive force to concrete is not improved. When the number of turns of twist given to the reinforcing fiber bundles composing the protrusions is larger than 50 turns per meter, the fiber bundles are damaged and the adhesion to the core portion is deteriorated. When the winding angle of these twisted reinforcing fiber bundles with respect to the axial direction of the core portion is smaller than 65-, the adhesive force to concrete is lowered. On the other hand, when the winding angle of these twisted reinforcing fiber bundles with respect to the axial direction of the core portion is larger than 85 , the adhesive force to concrete is also lowered.
In this connection, when the reinforcing fiber bundles impregnated with thermosetting resin are spirally wound round the core portion for the formation of protrusions, the twisted fiber bundles may be tightly wound round the core portion twice as shown in Fig. 5.
That is, the twisted fiber bundles are tightly wound round the core portion in one direction and then they are wound round the core portion in the opposite direction to cross each other. In this case, the adhesive force of the reinforcing composite bar to concrete becomes maximum.
However, after the adhesive force of the reinforcing composite bar to concrete has reached the maximum value, the reinforcing composite bar suddenly comes out from the concrete. Due to the above peculiar movement of the reinforcing composite bar, it is impossible to put the above fiber bundle winding method to practical use.
In order to exhibit the mechanical strength of the reinforcing fibers, the forming body, round the core portion of which the reinforcing fiber bundles impregnated with thermosetting resin are tightly wound for forming the protrusions, is thermally cured while the forming body is given a tension in the axial direction, that is, while the fibers composing the core portion are given a tension in the axial direction.
In this case, fundamentally, any method may be used for giving a predetermined tension to the reinforcing - 15 - 219~24~
fibers of the forming body in the axial direction.
However, it is preferable to use the following method.
Both ends of the forming body are fixed to a pair of jigs which are arranged at both ends of a stationary die made of metal. The forming body is entirely heated together with the stationary die made of metal in the above state, so that the thermosetting resin impregnated into the reinforcing fiber bundle is thermally cured. At this time, the forming body is given a tension by the thermal expansion of the stationary die made of metal. When the above method is adopted, it is possible to easily manufacture a reinforcing composite bar of fiber reinforced resin of high mechanical strength, the proof mechanical strength of which is high.
The reinforcing composite bar of fiber reinforced resin 16 can be provided as follows. The forming body 12 formed as described above having the core portion 13 and protrusions 14, both of which have not been cured yet, is detached together with a pair of jigs 1 from the chuck portions 8 arranged at both ends of the FW device 7.
Next, as shown in Fig. 3, utilizing the male screws 5 and the nuts 6 of a pair of jigs 1 arranged at both ends, the forming body is fixed to both ends of the stationary die 15 made of metal, the thermal expansion coefficient of which is higher than that of the reinforcing fiber bundles. Under the above condition, the forming body is heated at 110 to 200 C for 50 to 120 minutes, so that the thermosetting resin impregnated into the reinforcing fiber bundles of the forming body 12 is thermally cured. Due to the foregoing, as shown in Fig. 4, the reinforcing composite bar of fiber reinforced resin 16 can be provided, which includes the core portion 17 and the protrusions 18 in which the thermosetting resin impregnated into the reinforcing fiber bundles is cured.
An intensity of tension given in the process of thermosetting is determined to be a value so that the strain caused by the tension can be 500 to 3000 ~/m, and preferably 800 to 2000 ~/m. When the strain caused by the tension in the process of thermosetting is lower than 500 ~/m, it is impossible to exhibit a high mechanical strength capable of overcoming the thermosetting resin existing in the periphery of reinforcing fibers, and the orientation of the reinforcing fibers is deteriorated, so that the original mechanical strength of the reinforcing resin can not be exhibited. As a result, when an external stress is actually given, the resin is given an excessively high stress, and the reinforcing composite bar is damaged. When the strain caused by the tension in the process of thermosetting is higher than 3000 ~/m, on the contrary, the reinforcing fibers are damaged, which causes the deterioration of mechanical strength.
In this connection, the above tension exists as a residual stress even at a normal temperature.
Accordingly, the strain caused by the tension remains as it is even at the normal temperature.
There is shown an example in which a forming body was set in a stationary die 15 made of steel, the expansion coefficient of which was 1 x 105(1/-C), at a room temperature of 20 C, and the thermal curing processing was conducted under the following conditions. The thermal expansion coefficient of reinforcing fibers was much lower than that of steel. Therefore, it was possible to exhibit a tensile stress of about 800 ~/m by conducting the thermal curing processing at llO C for 60 min. Also it was possible to exhibit a tensile stress of about 2000 ~/m by conducting the thermal curing processing at 220 C for 60 min. The above range of tensile stress is particularly preferable.
When the above reinforcing composite bar of fiber reinforced resin is used in a concrete block, a compressive stress generated in a resin portion of the arrangement of bar which takes charge of a force on the tension side in the block is reduced, however, an excessively high tensile stress is not given to this - 17 - 21~1241 portion. Therefore, the resin portion is not damaged, so that the characteristic of the overall fiber bundle can be maintained.
Next, the curved reinforcing composite bar of fiber reinforced resin will be explained below.
In the same manner as the above straight reinforcing composite bar of fiber reinforced resin, this curved reinforcing composite bar of fiber reinforced resin uses the reinforcing fibers and thermosetting resin (reinforcing resin). For the purpose of manufacturing a forming body of the curved reinforcing composite bar of fiber reinforced resin, it is preferable to use the FW
device. In this example, after the forming body has been manufactured, one of the pair of jigs 1 shown in Figs. 1 and 2 is fixed, and the other jig is rotated so as to twist the core portion of the forming body by a predetermined amount of twist.
In this case, an amount of twist given to the core portion is preferably 0.5 to 1 turn per 1 m. When the core portion is not given a twist or an amount of twist given to the core portion is smaller than 0.5 turn per 1 m, there is a possibility that the forming body is locally buckled when the forming body is maintained in a curved condition. On the other hand, when an amount of twist given to the core portion is larger than 1 turn per 1 m, there is a possibility that the twisted portion returns to the original state by the rigidity of reinforcing fibers after the forming body has been cured.
Accordingly, when the above twist is given, it is possible to prevent the occurrence of local buckling of the forming body.
In this connection, except for the above method, it is possible to adopt a method in which the core portion is twisted after the formation of the core portion and then at least one reinforcing fiber bundle impregnated with thermosetting resin is wound on the surface of the core portion so as to form protrusions. In this case, impregnation of thermosetting resin into the reinforcing fiber bundles and winding of the reinforcing fiber bundles round the core portion may be continuously conducted by the FW device in the process of forming the core portion.
Alternatively, it may be conducted when reinforcing fiber bundles previously impregnated with thermosetting resin are brought in from the outside.
It is necessary for the thermosetting resin, which has been impregnated into the reinforcing fiber bundles of the forming body manufactured in this way, to be maintained in a state in which it is not cured until it is thermally cured in the following process. In this case, the thermosetting resin may be maintained either in a state in which it is not cured at all or in a state referred to as "B stage" in which it is partially cured.
It is preferable that the volume content of fiber of this core portion is 40 to 70%, and it is more preferable that the volume content of fiber of this core portion is 50 to 60%. When this volume content of fiber is lower than 40%, the resin becomes excessive, and the excess resin drips in the process of curing. When this volume content of fiber is higher than 70%, the quantity of resin is insufficient, and there is a possibility of failure in the adhesion of the core portion to the protrusions.
Next, the forming body is removed together with the pair of jigs 1 from the chuck portions 8 arranged on both sides of the FW device 7 shown in Fig. 1. Next, as shown in Fig. 10, utilizing the male screws 5 and the nuts 6 of the stationary portions 4 attached to the pair of jigs 1, the pair of jigs 1 are mounted on a curved die 12 having a receiving portion 13, the radius of curvature of which is a predetermined value and also having jig fixing portions 14 arranged on both sides of the receiving portion 13.
Under the above condition, while the forming body is given a tensile force by a mechanical means or by the action of thermal expansion of the metallic die, the forming body is heated at 110 to 200 C for 50 to 120 min, so that the thermosetting resin impregnated into the reinforcing fiber bundles forming the core portion and the protrusions can be thermally cured. In this way, the curved reinforcing composite bar 15 of fiber reinforced resin can be manufactured in which the protrusions 17 are wound round the core portion 16 as shown in Fig. 11. In this case, the forming body is given a tension so that a strain, the amount of which is 500 to 3000 ~/m, can be caused in the reinforcing composite bar.
The radius of curvature of this curved reinforcing composite bar of fiber reinforced resin is not particularly limited to a specific value. For example, the radius of curvature of this curved reinforcing composite bar used for the excavation of a pit in the construction work for sewerage is determined to be 6 to 10 m. The radius of curvature of this curved reinforcing composite bar used for the excavation of a pit in the construction work of underground electrical wiring ducts is determined to be 2 to 4 m. The radius of curvature of this curved reinforcing composite bar used for the excavation of a pit in the construction work of subway is determined to be 15 to 20 m.
As described above, in the straight reinforcing composite bar of fiber reinforced resin according to the present invention, when a predetermined amount of twist is given to the reinforcing fiber bundle which forms protrusions on the surface of the core portion, the height of the protrusions can be ensured. Accordingly, it is possible to remarkably improve the adhesive force of the reinforcing composite bar to concrete without deteriorating the mechanical strength of the core portion.
Since the thermosetting resin is thermally cured while the fibers of the forming body arranged in the axial direction are being given a tension, it is possible to manufacture a reinforcing composite bar at high speed, and further a plurality of reinforcing fiber bundles can be made uniform, and the slack of the fiber bundle can be - 20 - 219~241 removed. Accordingly, it is possible to manufacture a very strong reinforcing composite bar of fiber reinforced resin, the proof strength of which is high.
In the curved reinforcing composite bar of fiber reinforced resin, the local buckling and the deterioration of mechanical strength are not caused in the reinforcing fibers that compose the curved reinforcing composite bar.
Further, it is not necessary to reheat and bend the manufactured reinforcing composite bar. As a result, the manufacturing process of the curved reinforcing composite bar of fiber reinforced resin can be simplified.
EXAMPLES
Referring to examples and comparative examples, the present invention will be specifically explained as follows.
Example 1 In this example, the reinforcing composite bar of fiber reinforced resin 16 was manufactured as follows.
Carbon fibers, the elastic modulus of which was 3.4 x 105 MPa, were impregnated with epoxy resin. A core portion, the diameter of which was 20 mm, was made of the carbon fibers, wherein the fiber volume content of this core portion was 55% and the carbon fibers were oriented in the axial direction. Eight bundles of carbon fibers, each bundle was composed of 12,000 filaments carbon fibers, were twisted by 20 turns per 1 m and impregnated with epoxy resin. The thus obtained twisted fiber bundles were spirally wound round the aforementioned core portion at a winding angle of 80- with respect to the axial direction of the core portion. In this way, the forming body was made. The thermosetting resin impregnated into the carbon fiber bundles composing the core portion of the forming body and the protrusions was thermally cured. In this way, the reinforcing composite bar of fiber reinforced resin 16 shown in Fig. 4 was manufactured, which included the core portion 17 and the protrusions 18 composed of carbon fiber bundles, which had been twisted, to be wound 21 q 1 24 1 round the core portion.
ComParative Example 1 As shown in Fig. 5, the twisted carbon fiber bundles were spirally wound on the surface of the core portion 17 for the formation of protrusions 18 at a winding angle of 80- with respect to the axial direction of the core portion. In this case, the twisted fiber bundles were spirally wound round the core portion in one direction and then they were wound round the core portion in the opposite direction, so that the wound fiber bundles crossed each other. Except for the above points, the reinforcing composite bar of fiber reinforced resin 16 was manufactured in the same manner as that of Example 1.
This example was defined as Comparative Example 1.
ComParative ExamPle 2 Next, eight strands of carbon fiber, which were not twisted, were joined to each other and directly impregnated with resin. The thus obtained carbon fiber bundles were spirally wound round the core portion at a winding angle of 80- with respect to the axial direction of the core portion. Except for the above points, the reinforcing composite bar of fiber reinforced resin of Comparative Example was manufactured in the same manner as that of Example 1 described above. This was defined as Comparative Example 2, which is not shown in the drawing.
ComParative Example 3 As shown in Fig. 6, winding of the carbon fiber bundles was not conducted on the core portion 17, but on the surface of the core portion 17, there was formed a waving layer 19 composed of fibers and impregnated resin, the wave height of which was approximately 3 mm. By the above waving layer 19, protrusions were formed on the surface of the core portion 17. Except for the above points, the reinforcing composite bar of fiber reinforced resin 16 was manufactured in the same manner as that of Example 1 described before. This was defined as Comparative Example 3.
- 22 - 2 1 9 1 2 4 ~
Comparative ExamPle 4 A conventional reinforcing steel bar, the diameter of which was approximately 20 mm was defined as Comparative Example 4.
Adhesive property tests for concrete were conducted on the reinforcing composite bars of fiber reinforced resin 16 which were prepared in Example 1 and Comparative Examples 1 to 4 described above, in accordance with the tensile test method described on pages 26 to 27 of "Application of Continuous Fiber Reinforcing Bar to Concrete Structure" stipulated by the Standard of Japan Society of Civil Engineers. In Fig. 7, reference numeral 20 is a displacement meter, and reference numeral 21 is a piece of concrete.
Results of the tests are shown in Fig. 8. On the graph shown in Fig. 8, the horizontal axis represents a distance of slippage which is a numerical value of the displacement gauge 20. This numerical value represents an amount of drawing of the reinforcing composite bar from concrete.
As can be seen in Fig. 8, the adhesive force of the reinforcing composite bar of fiber reinforced resin of Example 1 was equal to or higher than the adhesive force of the reinforcing steel bar of Comparative Example 4.
Although the initial mechanical strength of the reinforcing composite bar of fiber reinforced resin of Comparative Example 1 was high, the mechanical strength suddenly decreased after that. The adhesive strength of the reinforcing composite bar of Comparative Example 2, in which twisting was not conducted on the fiber bundles, was not higher than half of the adhesive strength of the reinforcing composite bar of Example 1.
Example 2 In this example, the reinforcing composite bar of fiber reinforced resin was formed as follows. Carbon fibers, the elastic modulus of which was 3.4 x 105 MPa, were impregnated with epoxy resin. A core portion, the ~ 19 la~ I
diameter of which was 20 mm, was made of the carbon fibers, wherein the fiber volume content of this core portion was 55% and the carbon fibers were oriented in the axial direction. Eight bundles of carbon fibers, each bundle was composed of 12,000 filaments of carbon fibers, were twisted by 20 turns per 1 m and impregnated with epoxy resin. The thus obtained twisted fiber bundles were spirally wound round the aforementioned core portion at a winding angle of 80- with respect to the axial direction of the core portion. The above forming body was formed by the filament winding device.
The thus obtained forming body was dismounted from the filament winding device together with the jigs attached to both ends. As shown in Fig. 3, this forming body was fixed to a stationary die made of steel, utilizing the jigs attached to both ends. Then the epoxy resin impregnated into the carbon fiber bundles composing the forming body was thermally cured when the forming body was heated at 150-C for 60 min. In this way, the reinforcing composite bar of fiber reinforced resin of Example 2 was manufactured. A tension acting on the reinforcing composite bar of fiber reinforced resin generated by the thermal expansion force of the stationary die is shown on Table 1.
ComParative Exam~le 5 Epoxy resin impregnated into the carbon fiber bundles of the forming body was thermally cured when the forming body was heated at 60 C for 90 min. Except for the above point, the forming body of Comparative Example 5 was made in the same manner as that of Example 2.
Com~arative Exam~le 6 When the forming body was made, the core portion of the forming body was not given a tension by the jigs in the axial direction. Except for the above point, the reinforcing composite bar of fiber reinforced resin was manufactured in the same manner as that of Example 2. In this case, the thermally curing conditions were the same 21 9 ~ 24 1 as those of Example 2, that is, the forming body was heated at 150-C for 60 min.
The following tensile tests were conducted on the reinforcing composite bars of fiber reinforced resin manufactured in Example 2 and Comparative Examples 5 and 6. A rod-shaped test piece 22, the length of which was approximately 1500 mm, was made by cutting each reinforcing composite bar of fiber reinforced resin. As shown in Fig. 9, both end portions of each test piece 22, the length of which was 500 mm, were fixed to tube-shaped metal fittings 24 by the fixing members 23. Then the tube-shaped metal fittings 24 for fixation arranged at both end portions were held, and the test piece was drawn in the transverse direction until the rod-shaped test piece was broken. The results of the tensile test are shown on Table 1.
As can be seen on Table 1, the breaking load in Comparative Example 5 was higher than the breaking load in Comparative Example 6. However, the strain was out of a range of the present invention. Accordingly, the mechanical strength of the test piece was lower than the mechanical strength of the thermosetting resin existing in the periphery of the reinforcing fibers. As a result, the mechanical strength of the reinforcing composite bar was deteriorated. The breaking load of the test piece in Example 2 was much higher than the breaking load of the test piece in Comparative Example 5.
- 25 - 2~ q~ 2 4 Table 1 Tension is Curing Breaking Load given: temperature Amount of strain (~/m) ( C) (N) Example 2 1200 150 4.66 x 105 Comparative 400 60 3.79 x 105 Example S
Comparative 0 lS0 3.40 x 105 Example 6 Exam~le 3 S In the same manner as that of Example 2, a forming body, the diameter of which was approximately 20 mm, was made of carbon fibers, the elastic modulus of which was 3.4 x 105 MPa, and epoxy resin by the filament winding method, wherein the volume content of fiber was set at 55%. A jig arranged on one side was fixed onto the side wall of a furnace, and another jig arranged on the other side was attached to a hydraulic jack. A forming body mounted between the pair of jigs was given a tension of about 4.9 x 104 N by the hydraulic jack so that the strain lS of the forming body could be a value not less than 800 ~.
Under the above condition, only the forming body was thermally cured when it was heated at 150 C for 60 min.
A tensile test was conducted on the thus obtained forming body in the same manner as that of Example 2 and-Comparative Examples S and 6. According to the result ofthe tensile test, the breaking load was 4.85 x 105 N, which was remarkably higher than the breaking load in Comparative Example 6 in which no load was given.
Exam~le 4 In this example, 6 carbon fiber bundles and epoxy resin were used, wherein each carbon fiber bundle was composed of 12,000 filaments of carbon fibers, the elastic modulus of which was 3.4 x 105 MPa. The carbon fiber bundles were spread on the FW device (manufactured by Bolenz & Schafer Co. of Germany) by 30 times, and a core portion, the diameter of which was approximately 20 mm and the length of which was approximately 3 m, was formed by the FW method, wherein the volume content of fiber was set at 55%. After the core portion had been twisted by 2.4 turns (0.8 turn/m), the core portion was tightly wound by 4 carbon fiber bundles, wherein each carbon fiber bundle was composed of 12,000 filaments of carbon fibers.
The thus obtained core portion having protrusions was fixed in a curved die made of metal, the radius of curvature of which was 15 m, and thermally cured at 150'C
for 1 hour. In this way, a curved reinforcing composite bar of fiber reinforced resin was provided, the radius of curvature of which was 15 m, wherein the strain caused by a tensile force was 1,200 ~/m.
Carbon fiber yarn or prepreg impregnated with epoxy resin, the elastic modulus of which was 3.4 x 105 MPa, was used. By the hand-lay-up method or the method in which the braider device was used, a core portion, the diameter of which was approximately 20 mm and the length of which was approximately 3 m, was formed, wherein the fiber volume content was 55%. Both ends of the core portions were tied up and fixed to the jigs 1 with pieces of string. This core portion was attached to an FW device and twisted by 2.4 turns (0.8 turn/m). After that, the core portion was tightly wound by 4 carbon fiber bundles in the same manner as that of Example 1, wherein each bundle was composed of 12,000 filaments of carbon fibers.
The thus obtained core portion was fixed in a curved die made of metal, the radius of curvature of which was 15 m, 2 ! 9 1 24 1 and thermally cured at 150-C for 1 hour. In this way, a curved reinforcing composite bar of fiber reinforced resin was provided, the radius of curvature of which was 15 m, wherein the strain caused by a tensile force was 1,200 ~/m.
According to the same procedure of formation as that of Example 1, a core portion was tightly wound by 4 carbon fiber bundles, wherein each bundle was composed of 12,000 filaments of carbon fibers. After that, the core portion was twisted by 2.4 turns (0.8 turn/m) in the same direction as that of the protrusions without causing the separation of carbon fiber bundles. The thus obtained core portion having protrusions was fixed in a curved die made of metal, the radius of curvature of which was 15 m, and thermally cured at 150-C for 1 hour. In this way, a curved reinforcing composite bar of fiber reinforced resin was provided, the radius of curvature of which was 15 m, wherein the strain caused by a tensile force was 1,200 ~/m.
In this connection, the adhesive force of the forming bodies obtained in Examples 4 to 6 was substantially the same as that of Example 1, and the tensile strength of the forming bodies obtained in Examples 4 to 6 was substantially the same as that of Example 2.
- 27a - 21 91 241 INDUSTRIAL APPLICABILITY
The reinforcing composite bar of fiber reinforced resin of the present invention is capable of exhibiting a high adhesive force to concrete without deteriorating the mechanical strength of the core portion. Further, the reinforcing composite bar of fiber reinforced resin of the present invention is light, and its anticorrosion property is high, and further it has a good cutting property.
According to the method of the present invention for manufacturing a reinforcing composite bar of fiber reinforced resin, it is possible to manufacture a very strong reinforcing composite bar of fiber reinforced resin, the proof strength of which is high, at a high productivity. It is possible to make a reinforcing fiber to exhibit its original mechanical strength effectively.
Accordingly, it is possible to exhibit a required strength using a smaller amount of fibers. Therefore, the reinforcing composite bar of fiber reinforced resin of the present invention is highly economical, and it is possible to supply a large quantity of reinforcing composite bars to the market. Accordingly, it is possible to have the reinforcing composite bars of the present invention come into wide use.
Further, according to the present invention, it is possible to manufacture a very strong curved reinforcing composite bar of fiber reinforced resin, the dimensional accuracy of which is high, without deteriorating the mechanical strength. Also, it is possible to manufacture a very strong curved reinforcing composite bar of fiber reinforced resin which is curved by a radius of curvature of not less than 2 m, and the dimensional accuracy of the curved reinforcing composite bar is high.
Therefore, it is possible to provide an inexpensive reinforcing composite bar of fiber reinforced resin, the demand of which will be expanded as a substitute material of the reinforcing steel bar or PC steel wire. It can be concluded that the reinforcing composite bar of the present invention is very applicable industrially.
DESCRIPTION
Reinforcing Composite Bar of Fiber Reinforced Resin and Manufacturing Method Thereof TECHNICAL FIELD
The present invention relates to a reinforcing composite bar of fiber reinforced resin used as a reinforcing bar embedded in a concrete product such as a concrete building or a concrete structure during its manufacturing process. The present invention also relates to a method of manufacturing the reinforcing composite bar of fiber reinforced resin.
BACKGROUND ART
Conventionally, the use of a reinforcing composite bar of fiber reinforced resin has been proposed as a substitute of a reinforcing steel bar or a PC steel wire.
This reinforcing composite bar of fiber reinforced resin is manufactured in such a manner that highly elastic and highly strong continuous fibers such as carbon fibers or aramid fibers are impregnated with thermosetting epoxy resin and the thus impregnated epoxy resin is thermally cured. Therefore, it is well known such a reinforcing composite bar of fiber reinforced resin is light and its mechanical strength is high and further it has a high anticorrosion property. As described above, the reinforcing composite bar of fiber reinforced resin is light and its mechanical strength is high and further it has a high anticorrosion property, and furthermore it can be cut with a wood working saw. Due to the above excellent properties of the reinforcing composite bar of fiber reinforced resin, it is expected that the use of the reinforcing composite bar of fiber reinforced resin will expand in the field of reinforcing bars to be embedded in various concrete products.
However, the following two big problems may be encountered in the use of the aforementioned conventional 2 1 ~ 1 24 1 reinforcing composite bar of fiber reinforced resin.
The first problem is described as follows. A surface of the reinforcing composite bar of fiber reinforced resin is flat, so that the adhesive property of the reinforcing composite bar to concrete is low and its tension transmitting property is deteriorated.
The second problem is described as follows. It is difficult to enhance the productivity of reinforcing composite bars of fiber reinforced resin. When consideration is given to the mechanical strength of reinforcing fibers, the proof strength of the reinforcing composite bar of fiber reinforced resin is actually limited to half of the mechanical strength of the reinforcing fibers.
In order to solve the first problem, various methods have been proposed. For example, the following five methods are conventionally known.
As disclosed in Japanese Unexamined Patent Publication No. 61-274036, the first method is to form protrusions around a core by winding a plurality of reinforcing fiber bundles around it, so that the adhesive force of the reinforcing composite bar to concrete can be ensured.
The second method is to make particulate matters adhere onto the core surface as disclosed in Japanese Unexamined Patent Publication No. 4-363454, or to make short fibers adhere onto the core surface as disclosed in Japanese Unexamined Patent Publication No. 2-248559.
The third method is to form mechanical dents directly on the core surface so that the adhesive force can be enhanced as disclosed in Japanese Unexamined Patent Publication Nos. 63-206548 and 63--219746.
The fourth method is to structurally engage reinforcing composite bars with concrete by curving a plurality of bars as disclosed in Japanese Unexamined Patent Publication No. 3-1514444. Also, the fourth method is to form irregularities on the core surface by waving the surface fibers with a die, on the inner surface of which irregularities are formed, as disclosed in Japanese Unexamined Patent Publication No. 2-248559.
The fifth method is to form irregularities on the core surface by forming fibers in the axial direction into braids so that the adhesive force of the reinforcing composite bar to concrete can be enhanced as disclosed in Japanese Unexamined Patent Publication No. 4-363454.
However, according to the third to the fifth method, the fibers in the core portion are made to wave, or the fibers in the core portion are mechanically damaged.
Accordingly, although the adhesive force of the reinforcing composite bar to concrete is enhanced, the mechanical strength of the core portion is lowered.
Therefore, from the viewpoint of manufacturing reinforcing composite bars of fiber reinforced resin of high mechanical strength, these methods are not appropriate.
In this case, in order to provide a required intensity of mechanical strength, it is necessary to increase a quantity of fiber. Accordingly, the cost is disadvantageously raised.
According to the second method, small particulate matters or short fibers, which are not continuously formed, are made to adhere onto the core surface only by the adhesive force after all. Therefore, it is impossible to ensure a sufficiently high intensity of adhesive force of the core portion to concrete.
It could be said that the first method described above is the best, because the first method is capable of manufacturing a reinforcing composite bar of fiber reinforced resin without deteriorating the fiber strength of the core portion. However, concerning the adhesive force of the reinforcing composite bar to concrete, the first method is inferior to the third to the fifth method described above.
As described above, according to the first to the fifth method, it is difficult to enhance the adhesion property of the reinforcing composite bar to concrete to a level corresponding to the adhesion property of the conventional reinforcing steel bar, without deteriorating the high intensity of fiber strength of the core portion.
A reinforcing composite bar of fiber reinforced resin, the mechanical strength of which corresponds to the mechanical strength of a reinforcing steel bar, has not been developed yet.
The present inventors made investigations into the above second problem and obtained the following results.
Concerning the drawing method (for example, disclosed in Japanese Unexamined Patent Publication Nos. 61-274036 and 2-248559) which has been proposed as a typical method of manufacturing the reinforcing composite bar of fiber reinforced resin, the drawing speed is determined in accordance with the drawing condition. Therefore, the productivity of the drawing method is limited, and further when a strong drawing force is applied to the reinforcing composite bar, a grip portion to grip the fiber bundle is damaged by the strong drawing force. Accordingly, it is impossible to apply a necessarily high intensity of tension to the bundle of reinforcing fibers.
In accordance with an expansion of the market of reinforcing composite bars of fiber reinforced resin, it is demanded to develop not only a straight rod-shaped reinforcing composite bar but also a curved reinforcing composite bar, the radius of curvature of which is determined to be a predetermined value according to the use of the reinforcing composite bar. For example, at present, attention is given to the high cutting property of reinforcing composite bars of fiber reinforced resin.
In the caisson method which is one of the pit excavation methods used in the excavation of an underground tunnel, a plan is made in which reinforcing composite bars of fiber reinforced resin are used for an opening portion of the pit instead of common reinforcing steel bars. The use of curved reinforcing composite bars of fiber reinforced resin is indispensable to this excavation method.
However, concerning the reinforcing composite bar of fiber reinforced resin, only a straight rod-shaped type reinforcing composite bar is known at present.
Accordingly, in order to provide a curved reinforcing composite bar of fiber reinforced resin, there is no other way except for forcibly bending the straight rod-shaped reinforcing composite bar by a mechanical means.
However, this reinforcing composite bar of fiber reinforced resin is made of a brittle material in which plastic deformation is not caused, which is different from metal. Further, a ratio of elongation of the reinforcing fiber is very low, that is, a ratio of elongation is 1 to 2% at most. For this reason, when this reinforcing composite bar of fiber reinforced resin is subjected to forcible bending by a mechanical means, a portion of the fibers are broken, that is, the reinforcing fibers are damaged. As a result, when a radius of curvature is small in the bending process, the mechanical strength of the reinforcing composite bar of fiber reinforced resin, which is originally high, is deteriorated. Even if the radius of curvature is large, a bending stress is generated in the process of bending, and a usable mechanical strength of the composite bar is inevitably lowered. In any case, the original high strength of the composite bar is deteriorated.
In general, when the resin matrix composite material is curved after it has been cured, it is inevitably subjected to a forcible bending processing. As a result, the above problem is caused. It is possible to adopt a bending method in which a straight rod-shaped composite bar is heated again to a temperature not less than 120-C, and the resin impregnated into a bundle of reinforcing fibers is softened, so that bending is conducted.
However, this method is disadvantageous because bending of the composite bar is conducted at high temperatures and this work requires much time and labor. Further, even in this method, the reinforcing fibers are buckled and the mechanical strength is lowered. Therefore, it is impossible for the reinforcing composite bar of fiber reinforced resin to exhibit its original performance.
It is an object of the present invention to provide a reinforcing composite bar of fiber reinforced resin, the adhesive force to concrete of which is equal to or not less than the adhesive force of a metallic reinforcing bar to concrete without deteriorating the mechanical strength of the core portion.
It is another object of the present invention to provide a reinforcing composite bar of fiber reinforced resin in which the original strength of the reinforcing fibers can be fully utilized, so that a quantity of reinforcing fibers can be decreased and the production cost can be reduced, and further the proof strength can be ralsed.
It is still another object of the present invention to provide a method of manufacturing a reinforcing composite bar of fiber reinforced resin by which a reinforcing composite bar of fiber reinforced resin, the proof strength of which is high, can be manufactured at high productivity and low cost.
It is still another object of the present invention to provide a reinforcing composite bar of fiber reinforced resin of high mechanical strength which is curved by a predetermined radius of curvature, and the dimensional accuracy of which is high.
It is still another object of the present invention to provide a method of easily manufacturing a reinforcing composite bar of fiber reinforced resin of high mechanical strength which is curved by a predetermined radius of curvature, and the dimensional accuracy of which is high, wherein the mechanical strength is not deteriorated in the manufacturing process.
DISCLOSURE OF THE INVENTION
In order to solve the above problems, the present inventors made investigations in earnest and found the following.
Concerning the first problem, in the case of a reinforcing composite bar of fiber reinforced resin having a core portion on which protrusions are formed, when reinforcing fiber bundles composing the protrusions on the surface of the core portion are twisted, it is possible to enhance an intensity of the adhesive force of the reinforcing composite bar to concrete without deteriorating the mechanical strength of the core portion.
Concerning the second problem, when the core portion and the protrusions are successively formed into a forming body and the thus obtained forming body is thermally cured while a tension is given to the forming body in the axial direction (in the direction of a reinforcing fiber bundle), so that the reinforcing fibers can be arranged in the same direction without giving a tension to the peripheral resin (since the resin is easily damaged when a tensile stress is given, only a compressive stress is given to the resin), it is possible to utilize the original high mechanical strength and high elasticity of the reinforcing resin. Due to the foregoing, it is possible to manufacture a reinforcing composite bar of fiber reinforced resin, the proof strength of which is high, at a high production efficiency.
In order to curve a reinforcing composite bar of fiber reinforced resin without deteriorating its mechanical strength, it is effective that the reinforcing composite bar of fiber reinforced resin is subjected to thermal curing processing under the condition that the core portion of the reinforcing composite bar is twisted and the forming body composed of the core portion and the protrusions is curved and also under the condition that the core portion is given a predetermined intensity of tensile stress. When the core portion is given a tensile stress, each unit fiber composing the core portion is substantially equally given a tensile stress.
21~1241 Accordingly, even if the core portion is curved while it is twisted, the local buckling of the forming body and the deterioration of mechanical strength can be completely avoided.
The present invention will be further explained as follows.
The present invention is to provide a reinforcing composite bar of fiber reinforced resin composed of a forming body comprising: a core portion and a winding portion to form protrusions on a surface of the core portion, both potions being made of thermosetting material containing thermosetting resin and reinforcing fiber bundles, wherein the forming body is strained by 500 to 3000 ~/m when a tension is applied to the forming body.
In order to manufacture the above reinforcing composite bar, for example, a filament winding device is used; jigs having a plurality of pins are attached to both end chuck portions of the filament winding device;
reinforcing fiber bundles impregnated with thermosetting resin are arranged between the pins of a pair of jigs so as to form a core portion by the filament winding method;
a reinforcing fiber bundle impregnated with thermosetting resin is tightly wound on the circumferential surface of this core portion so as to form protrusions; and the thus obtained forming body is subjected to thermosetting processing while a tension is given to the obtained forming body in the axial direction. Alternatively, the reinforcing fiber bundle forming the above protrusions is given a predetermined twist.
Due to the above construction, the reinforcing composite bar of the present invention has a high tensile strength in which the original mechanical strength of the reinforcing fiber is exhibited, and the adhesive force of the reinforcing composite bar to concrete can be greatly enhanced while the fibers are prevented from being damaged.
Further, the present invention is to provide a curved g reinforcing composite bar of fiber reinforced resin, the overall shape of which is curved by a predetermined radius of curvature, comprising: a core portion made of reinforcing fiber bundles impregnated with thermosetting resin; and protrusions formed when a reinforcing fiber bundle impregnated with thermosetting resin is tightly wound round the core portion.
In order to manufacture the above reinforcing composite bar, first, the core portion is formed; this core portion is twisted; protrusions are formed by at least one reinforcing fiber bundle impregnated with thermosetting resin; the thus obtained core member having protrusions, that is, a forming body is fixed in a curved mold which is curved by a predetermined radius of curvature; and the thermosetting resin impregnated into the above reinforcing fiber bundle is thermally set while a predetermined intensity of tensile stress is given to the core portion.
Another method is described as follows. Protrusions are formed on a formed core portion by at least one reinforcing fiber bundle impregnated with thermosetting resin; the core portion is twisted in the same direction as that of the thus formed protrusions; the thus obtained core member having protrusions, that is, a forming body is fixed in a curved mold which is curved by a predetermined radius of curvature; and thermosetting resin impregnated into the above reinforcing fiber bundle is thermally set while a predetermined intensity of tensile stress is given to the core portion.
The curved reinforcing composite bar of fiber reinforced resin manufactured in this way is very suitable for the reinforcing bars used for the excavation of a pit in the construction work of sewerage, subway and so forth.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a partially cutaway front view of a jig used in the filament winding method.
Fig. 2 is a schematic illustration showing a concept - lo - 2191241 of the filament winding method.
Fig. 3 is a partially perspective view of a metallic stationary die.
Fig. 4 is a partially front view showing a reinforcing composite bar of fiber reinforced resin of an example of the present invention.
Fig. 5 is a partially front view showing a reinforcing composite bar of fiber reinforced resin of Comparative Example 1.
Fig. 6 is a partially cross-sectional front view showing a reinforcing composite bar of fiber reinforced resin of Comparative Example 3.
Fig. 7 is a partially cross-sectional front view showing a method of the tensile test.
Fig. 8 is a graph showing a relation between the average adhesive stress intensity and the amount of slippage obtained in the tensile test.
Fig. 9 is a partially cross-sectional perspective view showing a rod-shaped test piece used in the tensile test in the example of the present invention and also used in the tensile test in the comparative example.
Fig. 10 is a partially perspective view showing a state of forming a curved reinforcing composite bar of fiber reinforced resin of another example of the present invention.
Fig. 11 is a partially perspective view showing a curved reinforcing composite bar of fiber reinforced resin of another example of the present invention.
BEST MODE OF CARRYING OUT THE INVENTION
First, a straight reinforcing composite bar of fiber reinforced resin of the present invention will be explained below.
Concerning the reinforcing fiber used for forming the reinforcing fiber bundle in the present invention, as long as they are fibers which continue from a leading end to a trailing end of the reinforcing composite bar to be manufactured, any conventional fibers may be used. For example, various carbon fibers such as PAN-based (polyacrylonitrile-base), pitch-based and hybrid carbon fibers may be used, and further aramid fibers and glass fibers may be also used. Concerning the thermosetting resin (reinforcing resin) impregnated into the reinforcing fiber bundle, any conventional thermosetting resin may be appropriately used. Usable examples of thermosetting resins are: epoxy resin, phenol resin, and polyamide resin. These reinforcing fibers and thermosetting resin may be appropriately selected in accordance with the use of the reinforcing composite bar to be manufactured.
However, from the viewpoint of heat resistance and resistance to corrosion, epoxy resin is preferably used as thermosetting resin.
Concerning the formation of the core portion in the present invention, only from the viewpoint of improving the adhesive property of the reinforcing composite bar to concrete, a hand-lay-up method may be adopted, in which the carbon fiber yarn impregnated with thermosetting resin is used as a core, and the carbon fiber prepreg impregnated with thermosetting resin is tightly wound round the core. Alternatively, a method may be adopted in which a plurality of pieces of carbon fiber yarn impregnated with thermosetting resin are collected and pieces of braid yarn are tightly wound round the collected pieces of carbon fiber yarn by a braider. Further, a drawing method may be adopted. However, it is preferable to use the following method.
That is, in a filament winding device, which will be referred to as an "FW" device" hereinafter, jigs having a plurality of pins are attached to both end chuck portions of the filament winding device; reinforcing fiber bundles impregnated with thermosetting resin are arranged between the pins of a pair of jigs so as to form a core portion by the filament winding method, which will be referred to as "FW method" hereinafter; a reinforcing fiber bundle impregnated with thermosetting resin is tightly wound on a circumferential surface of this core portion so as to form protrusions; and the thus obtained forming body is subjected to thermosetting processing while a tension is given to the obtained forming body in the axial direction.
This method will be specifically explained below.
First, as shown in Fig. 1, there is prepared a jig 1 made of metal including: a holding portion 2 arranged on the base end side; a plurality of pins 3, the number of which is 2 to 10, arranged on the front end side; and a stationary portion 4 composed of a male screw 5 and a nut 6, arranged between the holding portion 2 and the pin 3.
As shown in Fig. 2, a pair of metallic jigs 1 are attached to both end chuck portions 8 of the filament winding device 7.
Next, a plurality of reinforcing fiber bundles 9 are continuously drawn out and made to pass in a resin bath 10 in which thermosetting resin is accommodated. In this resin bath 10, the reinforcing fiber bundles are impregnated with the thermosetting resin. Then, these reinforcing fiber bundles impregnated with thermosetting resin are repeatedly spread by a traverser 11 between the plurality of pins 3 attached to the pair of jigs 1 so that the diameter of the spread reinforcing fiber bundles can be a predetermined value. In this way, the core portion can be formed, in which the plurality of reinforcing fiber bundles impregnated with thermosetting resin are arranged in the axial direction.
Concerning the core portion formed in this way, it is necessary for the thermosetting resin, which has been impregnated into the reinforcing fiber bundles, to be maintained in a condition in which it is not cured, until protrusions are formed on the surfaces of the reinforcing bundles and thermally cured. In this case, the thermosetting resin may be maintained either in a condition in which it is not cured at all or in a condition referred to as "B stage" in which it is partially cured. It is preferable that the volume content of fiber of this core portion is 40 to 70%, and it is more preferable that the volume content of fiber of this core portion is 50 to 60~. When this volume content of fiber is lower than 40%, the resin becomes too full, and the excess resin drips in the process of curing. When this volume content of fiber is higher than 70~, the quantity of resin is insufficient, and there is a possibility of failure in the adhesion of the core portion to the protrusions.
As described above, when at least one reinforcing fiber bundle impregnated with thermosetting resin is successively wound on a surface of the core portion, protrusions are formed round the core portion, and the forming body composed of the core portion and protrusions can be made. In this case, impregnation of thermosetting resin into the reinforcing fiber bundles and winding of the reinforcing fiber bundles round the core portion may be continuously conducted with the FW device in the process of forming the core portion. Alternatively, it may be conducted when reinforcing fiber bundles previously impregnated with thermosetting resin are brought in from the outside.
In this case, the thermosetting resin impregnated into the reinforcing fiber bundles for forming protrusions and its volume content of fiber may be the same as those of the core portion described before.
In order to improve the adhesive force of the reinforcing composite bar to concrete, it is preferable that the reinforcing fiber bundles impregnated with thermosetting resin are twisted by 10 to 50 turns per meter and tightly wound round the core portion at an angle of 65 to 85- with respect to the axial direction or the core portion.
When the number of turns of twist given to the reinforcing fiber bundles composing the protrusions is smaller than 10 turns per meter, the adhesive force to concrete is not improved. When the number of turns of twist given to the reinforcing fiber bundles composing the protrusions is larger than 50 turns per meter, the fiber bundles are damaged and the adhesion to the core portion is deteriorated. When the winding angle of these twisted reinforcing fiber bundles with respect to the axial direction of the core portion is smaller than 65-, the adhesive force to concrete is lowered. On the other hand, when the winding angle of these twisted reinforcing fiber bundles with respect to the axial direction of the core portion is larger than 85 , the adhesive force to concrete is also lowered.
In this connection, when the reinforcing fiber bundles impregnated with thermosetting resin are spirally wound round the core portion for the formation of protrusions, the twisted fiber bundles may be tightly wound round the core portion twice as shown in Fig. 5.
That is, the twisted fiber bundles are tightly wound round the core portion in one direction and then they are wound round the core portion in the opposite direction to cross each other. In this case, the adhesive force of the reinforcing composite bar to concrete becomes maximum.
However, after the adhesive force of the reinforcing composite bar to concrete has reached the maximum value, the reinforcing composite bar suddenly comes out from the concrete. Due to the above peculiar movement of the reinforcing composite bar, it is impossible to put the above fiber bundle winding method to practical use.
In order to exhibit the mechanical strength of the reinforcing fibers, the forming body, round the core portion of which the reinforcing fiber bundles impregnated with thermosetting resin are tightly wound for forming the protrusions, is thermally cured while the forming body is given a tension in the axial direction, that is, while the fibers composing the core portion are given a tension in the axial direction.
In this case, fundamentally, any method may be used for giving a predetermined tension to the reinforcing - 15 - 219~24~
fibers of the forming body in the axial direction.
However, it is preferable to use the following method.
Both ends of the forming body are fixed to a pair of jigs which are arranged at both ends of a stationary die made of metal. The forming body is entirely heated together with the stationary die made of metal in the above state, so that the thermosetting resin impregnated into the reinforcing fiber bundle is thermally cured. At this time, the forming body is given a tension by the thermal expansion of the stationary die made of metal. When the above method is adopted, it is possible to easily manufacture a reinforcing composite bar of fiber reinforced resin of high mechanical strength, the proof mechanical strength of which is high.
The reinforcing composite bar of fiber reinforced resin 16 can be provided as follows. The forming body 12 formed as described above having the core portion 13 and protrusions 14, both of which have not been cured yet, is detached together with a pair of jigs 1 from the chuck portions 8 arranged at both ends of the FW device 7.
Next, as shown in Fig. 3, utilizing the male screws 5 and the nuts 6 of a pair of jigs 1 arranged at both ends, the forming body is fixed to both ends of the stationary die 15 made of metal, the thermal expansion coefficient of which is higher than that of the reinforcing fiber bundles. Under the above condition, the forming body is heated at 110 to 200 C for 50 to 120 minutes, so that the thermosetting resin impregnated into the reinforcing fiber bundles of the forming body 12 is thermally cured. Due to the foregoing, as shown in Fig. 4, the reinforcing composite bar of fiber reinforced resin 16 can be provided, which includes the core portion 17 and the protrusions 18 in which the thermosetting resin impregnated into the reinforcing fiber bundles is cured.
An intensity of tension given in the process of thermosetting is determined to be a value so that the strain caused by the tension can be 500 to 3000 ~/m, and preferably 800 to 2000 ~/m. When the strain caused by the tension in the process of thermosetting is lower than 500 ~/m, it is impossible to exhibit a high mechanical strength capable of overcoming the thermosetting resin existing in the periphery of reinforcing fibers, and the orientation of the reinforcing fibers is deteriorated, so that the original mechanical strength of the reinforcing resin can not be exhibited. As a result, when an external stress is actually given, the resin is given an excessively high stress, and the reinforcing composite bar is damaged. When the strain caused by the tension in the process of thermosetting is higher than 3000 ~/m, on the contrary, the reinforcing fibers are damaged, which causes the deterioration of mechanical strength.
In this connection, the above tension exists as a residual stress even at a normal temperature.
Accordingly, the strain caused by the tension remains as it is even at the normal temperature.
There is shown an example in which a forming body was set in a stationary die 15 made of steel, the expansion coefficient of which was 1 x 105(1/-C), at a room temperature of 20 C, and the thermal curing processing was conducted under the following conditions. The thermal expansion coefficient of reinforcing fibers was much lower than that of steel. Therefore, it was possible to exhibit a tensile stress of about 800 ~/m by conducting the thermal curing processing at llO C for 60 min. Also it was possible to exhibit a tensile stress of about 2000 ~/m by conducting the thermal curing processing at 220 C for 60 min. The above range of tensile stress is particularly preferable.
When the above reinforcing composite bar of fiber reinforced resin is used in a concrete block, a compressive stress generated in a resin portion of the arrangement of bar which takes charge of a force on the tension side in the block is reduced, however, an excessively high tensile stress is not given to this - 17 - 21~1241 portion. Therefore, the resin portion is not damaged, so that the characteristic of the overall fiber bundle can be maintained.
Next, the curved reinforcing composite bar of fiber reinforced resin will be explained below.
In the same manner as the above straight reinforcing composite bar of fiber reinforced resin, this curved reinforcing composite bar of fiber reinforced resin uses the reinforcing fibers and thermosetting resin (reinforcing resin). For the purpose of manufacturing a forming body of the curved reinforcing composite bar of fiber reinforced resin, it is preferable to use the FW
device. In this example, after the forming body has been manufactured, one of the pair of jigs 1 shown in Figs. 1 and 2 is fixed, and the other jig is rotated so as to twist the core portion of the forming body by a predetermined amount of twist.
In this case, an amount of twist given to the core portion is preferably 0.5 to 1 turn per 1 m. When the core portion is not given a twist or an amount of twist given to the core portion is smaller than 0.5 turn per 1 m, there is a possibility that the forming body is locally buckled when the forming body is maintained in a curved condition. On the other hand, when an amount of twist given to the core portion is larger than 1 turn per 1 m, there is a possibility that the twisted portion returns to the original state by the rigidity of reinforcing fibers after the forming body has been cured.
Accordingly, when the above twist is given, it is possible to prevent the occurrence of local buckling of the forming body.
In this connection, except for the above method, it is possible to adopt a method in which the core portion is twisted after the formation of the core portion and then at least one reinforcing fiber bundle impregnated with thermosetting resin is wound on the surface of the core portion so as to form protrusions. In this case, impregnation of thermosetting resin into the reinforcing fiber bundles and winding of the reinforcing fiber bundles round the core portion may be continuously conducted by the FW device in the process of forming the core portion.
Alternatively, it may be conducted when reinforcing fiber bundles previously impregnated with thermosetting resin are brought in from the outside.
It is necessary for the thermosetting resin, which has been impregnated into the reinforcing fiber bundles of the forming body manufactured in this way, to be maintained in a state in which it is not cured until it is thermally cured in the following process. In this case, the thermosetting resin may be maintained either in a state in which it is not cured at all or in a state referred to as "B stage" in which it is partially cured.
It is preferable that the volume content of fiber of this core portion is 40 to 70%, and it is more preferable that the volume content of fiber of this core portion is 50 to 60%. When this volume content of fiber is lower than 40%, the resin becomes excessive, and the excess resin drips in the process of curing. When this volume content of fiber is higher than 70%, the quantity of resin is insufficient, and there is a possibility of failure in the adhesion of the core portion to the protrusions.
Next, the forming body is removed together with the pair of jigs 1 from the chuck portions 8 arranged on both sides of the FW device 7 shown in Fig. 1. Next, as shown in Fig. 10, utilizing the male screws 5 and the nuts 6 of the stationary portions 4 attached to the pair of jigs 1, the pair of jigs 1 are mounted on a curved die 12 having a receiving portion 13, the radius of curvature of which is a predetermined value and also having jig fixing portions 14 arranged on both sides of the receiving portion 13.
Under the above condition, while the forming body is given a tensile force by a mechanical means or by the action of thermal expansion of the metallic die, the forming body is heated at 110 to 200 C for 50 to 120 min, so that the thermosetting resin impregnated into the reinforcing fiber bundles forming the core portion and the protrusions can be thermally cured. In this way, the curved reinforcing composite bar 15 of fiber reinforced resin can be manufactured in which the protrusions 17 are wound round the core portion 16 as shown in Fig. 11. In this case, the forming body is given a tension so that a strain, the amount of which is 500 to 3000 ~/m, can be caused in the reinforcing composite bar.
The radius of curvature of this curved reinforcing composite bar of fiber reinforced resin is not particularly limited to a specific value. For example, the radius of curvature of this curved reinforcing composite bar used for the excavation of a pit in the construction work for sewerage is determined to be 6 to 10 m. The radius of curvature of this curved reinforcing composite bar used for the excavation of a pit in the construction work of underground electrical wiring ducts is determined to be 2 to 4 m. The radius of curvature of this curved reinforcing composite bar used for the excavation of a pit in the construction work of subway is determined to be 15 to 20 m.
As described above, in the straight reinforcing composite bar of fiber reinforced resin according to the present invention, when a predetermined amount of twist is given to the reinforcing fiber bundle which forms protrusions on the surface of the core portion, the height of the protrusions can be ensured. Accordingly, it is possible to remarkably improve the adhesive force of the reinforcing composite bar to concrete without deteriorating the mechanical strength of the core portion.
Since the thermosetting resin is thermally cured while the fibers of the forming body arranged in the axial direction are being given a tension, it is possible to manufacture a reinforcing composite bar at high speed, and further a plurality of reinforcing fiber bundles can be made uniform, and the slack of the fiber bundle can be - 20 - 219~241 removed. Accordingly, it is possible to manufacture a very strong reinforcing composite bar of fiber reinforced resin, the proof strength of which is high.
In the curved reinforcing composite bar of fiber reinforced resin, the local buckling and the deterioration of mechanical strength are not caused in the reinforcing fibers that compose the curved reinforcing composite bar.
Further, it is not necessary to reheat and bend the manufactured reinforcing composite bar. As a result, the manufacturing process of the curved reinforcing composite bar of fiber reinforced resin can be simplified.
EXAMPLES
Referring to examples and comparative examples, the present invention will be specifically explained as follows.
Example 1 In this example, the reinforcing composite bar of fiber reinforced resin 16 was manufactured as follows.
Carbon fibers, the elastic modulus of which was 3.4 x 105 MPa, were impregnated with epoxy resin. A core portion, the diameter of which was 20 mm, was made of the carbon fibers, wherein the fiber volume content of this core portion was 55% and the carbon fibers were oriented in the axial direction. Eight bundles of carbon fibers, each bundle was composed of 12,000 filaments carbon fibers, were twisted by 20 turns per 1 m and impregnated with epoxy resin. The thus obtained twisted fiber bundles were spirally wound round the aforementioned core portion at a winding angle of 80- with respect to the axial direction of the core portion. In this way, the forming body was made. The thermosetting resin impregnated into the carbon fiber bundles composing the core portion of the forming body and the protrusions was thermally cured. In this way, the reinforcing composite bar of fiber reinforced resin 16 shown in Fig. 4 was manufactured, which included the core portion 17 and the protrusions 18 composed of carbon fiber bundles, which had been twisted, to be wound 21 q 1 24 1 round the core portion.
ComParative Example 1 As shown in Fig. 5, the twisted carbon fiber bundles were spirally wound on the surface of the core portion 17 for the formation of protrusions 18 at a winding angle of 80- with respect to the axial direction of the core portion. In this case, the twisted fiber bundles were spirally wound round the core portion in one direction and then they were wound round the core portion in the opposite direction, so that the wound fiber bundles crossed each other. Except for the above points, the reinforcing composite bar of fiber reinforced resin 16 was manufactured in the same manner as that of Example 1.
This example was defined as Comparative Example 1.
ComParative ExamPle 2 Next, eight strands of carbon fiber, which were not twisted, were joined to each other and directly impregnated with resin. The thus obtained carbon fiber bundles were spirally wound round the core portion at a winding angle of 80- with respect to the axial direction of the core portion. Except for the above points, the reinforcing composite bar of fiber reinforced resin of Comparative Example was manufactured in the same manner as that of Example 1 described above. This was defined as Comparative Example 2, which is not shown in the drawing.
ComParative Example 3 As shown in Fig. 6, winding of the carbon fiber bundles was not conducted on the core portion 17, but on the surface of the core portion 17, there was formed a waving layer 19 composed of fibers and impregnated resin, the wave height of which was approximately 3 mm. By the above waving layer 19, protrusions were formed on the surface of the core portion 17. Except for the above points, the reinforcing composite bar of fiber reinforced resin 16 was manufactured in the same manner as that of Example 1 described before. This was defined as Comparative Example 3.
- 22 - 2 1 9 1 2 4 ~
Comparative ExamPle 4 A conventional reinforcing steel bar, the diameter of which was approximately 20 mm was defined as Comparative Example 4.
Adhesive property tests for concrete were conducted on the reinforcing composite bars of fiber reinforced resin 16 which were prepared in Example 1 and Comparative Examples 1 to 4 described above, in accordance with the tensile test method described on pages 26 to 27 of "Application of Continuous Fiber Reinforcing Bar to Concrete Structure" stipulated by the Standard of Japan Society of Civil Engineers. In Fig. 7, reference numeral 20 is a displacement meter, and reference numeral 21 is a piece of concrete.
Results of the tests are shown in Fig. 8. On the graph shown in Fig. 8, the horizontal axis represents a distance of slippage which is a numerical value of the displacement gauge 20. This numerical value represents an amount of drawing of the reinforcing composite bar from concrete.
As can be seen in Fig. 8, the adhesive force of the reinforcing composite bar of fiber reinforced resin of Example 1 was equal to or higher than the adhesive force of the reinforcing steel bar of Comparative Example 4.
Although the initial mechanical strength of the reinforcing composite bar of fiber reinforced resin of Comparative Example 1 was high, the mechanical strength suddenly decreased after that. The adhesive strength of the reinforcing composite bar of Comparative Example 2, in which twisting was not conducted on the fiber bundles, was not higher than half of the adhesive strength of the reinforcing composite bar of Example 1.
Example 2 In this example, the reinforcing composite bar of fiber reinforced resin was formed as follows. Carbon fibers, the elastic modulus of which was 3.4 x 105 MPa, were impregnated with epoxy resin. A core portion, the ~ 19 la~ I
diameter of which was 20 mm, was made of the carbon fibers, wherein the fiber volume content of this core portion was 55% and the carbon fibers were oriented in the axial direction. Eight bundles of carbon fibers, each bundle was composed of 12,000 filaments of carbon fibers, were twisted by 20 turns per 1 m and impregnated with epoxy resin. The thus obtained twisted fiber bundles were spirally wound round the aforementioned core portion at a winding angle of 80- with respect to the axial direction of the core portion. The above forming body was formed by the filament winding device.
The thus obtained forming body was dismounted from the filament winding device together with the jigs attached to both ends. As shown in Fig. 3, this forming body was fixed to a stationary die made of steel, utilizing the jigs attached to both ends. Then the epoxy resin impregnated into the carbon fiber bundles composing the forming body was thermally cured when the forming body was heated at 150-C for 60 min. In this way, the reinforcing composite bar of fiber reinforced resin of Example 2 was manufactured. A tension acting on the reinforcing composite bar of fiber reinforced resin generated by the thermal expansion force of the stationary die is shown on Table 1.
ComParative Exam~le 5 Epoxy resin impregnated into the carbon fiber bundles of the forming body was thermally cured when the forming body was heated at 60 C for 90 min. Except for the above point, the forming body of Comparative Example 5 was made in the same manner as that of Example 2.
Com~arative Exam~le 6 When the forming body was made, the core portion of the forming body was not given a tension by the jigs in the axial direction. Except for the above point, the reinforcing composite bar of fiber reinforced resin was manufactured in the same manner as that of Example 2. In this case, the thermally curing conditions were the same 21 9 ~ 24 1 as those of Example 2, that is, the forming body was heated at 150-C for 60 min.
The following tensile tests were conducted on the reinforcing composite bars of fiber reinforced resin manufactured in Example 2 and Comparative Examples 5 and 6. A rod-shaped test piece 22, the length of which was approximately 1500 mm, was made by cutting each reinforcing composite bar of fiber reinforced resin. As shown in Fig. 9, both end portions of each test piece 22, the length of which was 500 mm, were fixed to tube-shaped metal fittings 24 by the fixing members 23. Then the tube-shaped metal fittings 24 for fixation arranged at both end portions were held, and the test piece was drawn in the transverse direction until the rod-shaped test piece was broken. The results of the tensile test are shown on Table 1.
As can be seen on Table 1, the breaking load in Comparative Example 5 was higher than the breaking load in Comparative Example 6. However, the strain was out of a range of the present invention. Accordingly, the mechanical strength of the test piece was lower than the mechanical strength of the thermosetting resin existing in the periphery of the reinforcing fibers. As a result, the mechanical strength of the reinforcing composite bar was deteriorated. The breaking load of the test piece in Example 2 was much higher than the breaking load of the test piece in Comparative Example 5.
- 25 - 2~ q~ 2 4 Table 1 Tension is Curing Breaking Load given: temperature Amount of strain (~/m) ( C) (N) Example 2 1200 150 4.66 x 105 Comparative 400 60 3.79 x 105 Example S
Comparative 0 lS0 3.40 x 105 Example 6 Exam~le 3 S In the same manner as that of Example 2, a forming body, the diameter of which was approximately 20 mm, was made of carbon fibers, the elastic modulus of which was 3.4 x 105 MPa, and epoxy resin by the filament winding method, wherein the volume content of fiber was set at 55%. A jig arranged on one side was fixed onto the side wall of a furnace, and another jig arranged on the other side was attached to a hydraulic jack. A forming body mounted between the pair of jigs was given a tension of about 4.9 x 104 N by the hydraulic jack so that the strain lS of the forming body could be a value not less than 800 ~.
Under the above condition, only the forming body was thermally cured when it was heated at 150 C for 60 min.
A tensile test was conducted on the thus obtained forming body in the same manner as that of Example 2 and-Comparative Examples S and 6. According to the result ofthe tensile test, the breaking load was 4.85 x 105 N, which was remarkably higher than the breaking load in Comparative Example 6 in which no load was given.
Exam~le 4 In this example, 6 carbon fiber bundles and epoxy resin were used, wherein each carbon fiber bundle was composed of 12,000 filaments of carbon fibers, the elastic modulus of which was 3.4 x 105 MPa. The carbon fiber bundles were spread on the FW device (manufactured by Bolenz & Schafer Co. of Germany) by 30 times, and a core portion, the diameter of which was approximately 20 mm and the length of which was approximately 3 m, was formed by the FW method, wherein the volume content of fiber was set at 55%. After the core portion had been twisted by 2.4 turns (0.8 turn/m), the core portion was tightly wound by 4 carbon fiber bundles, wherein each carbon fiber bundle was composed of 12,000 filaments of carbon fibers.
The thus obtained core portion having protrusions was fixed in a curved die made of metal, the radius of curvature of which was 15 m, and thermally cured at 150'C
for 1 hour. In this way, a curved reinforcing composite bar of fiber reinforced resin was provided, the radius of curvature of which was 15 m, wherein the strain caused by a tensile force was 1,200 ~/m.
Carbon fiber yarn or prepreg impregnated with epoxy resin, the elastic modulus of which was 3.4 x 105 MPa, was used. By the hand-lay-up method or the method in which the braider device was used, a core portion, the diameter of which was approximately 20 mm and the length of which was approximately 3 m, was formed, wherein the fiber volume content was 55%. Both ends of the core portions were tied up and fixed to the jigs 1 with pieces of string. This core portion was attached to an FW device and twisted by 2.4 turns (0.8 turn/m). After that, the core portion was tightly wound by 4 carbon fiber bundles in the same manner as that of Example 1, wherein each bundle was composed of 12,000 filaments of carbon fibers.
The thus obtained core portion was fixed in a curved die made of metal, the radius of curvature of which was 15 m, 2 ! 9 1 24 1 and thermally cured at 150-C for 1 hour. In this way, a curved reinforcing composite bar of fiber reinforced resin was provided, the radius of curvature of which was 15 m, wherein the strain caused by a tensile force was 1,200 ~/m.
According to the same procedure of formation as that of Example 1, a core portion was tightly wound by 4 carbon fiber bundles, wherein each bundle was composed of 12,000 filaments of carbon fibers. After that, the core portion was twisted by 2.4 turns (0.8 turn/m) in the same direction as that of the protrusions without causing the separation of carbon fiber bundles. The thus obtained core portion having protrusions was fixed in a curved die made of metal, the radius of curvature of which was 15 m, and thermally cured at 150-C for 1 hour. In this way, a curved reinforcing composite bar of fiber reinforced resin was provided, the radius of curvature of which was 15 m, wherein the strain caused by a tensile force was 1,200 ~/m.
In this connection, the adhesive force of the forming bodies obtained in Examples 4 to 6 was substantially the same as that of Example 1, and the tensile strength of the forming bodies obtained in Examples 4 to 6 was substantially the same as that of Example 2.
- 27a - 21 91 241 INDUSTRIAL APPLICABILITY
The reinforcing composite bar of fiber reinforced resin of the present invention is capable of exhibiting a high adhesive force to concrete without deteriorating the mechanical strength of the core portion. Further, the reinforcing composite bar of fiber reinforced resin of the present invention is light, and its anticorrosion property is high, and further it has a good cutting property.
According to the method of the present invention for manufacturing a reinforcing composite bar of fiber reinforced resin, it is possible to manufacture a very strong reinforcing composite bar of fiber reinforced resin, the proof strength of which is high, at a high productivity. It is possible to make a reinforcing fiber to exhibit its original mechanical strength effectively.
Accordingly, it is possible to exhibit a required strength using a smaller amount of fibers. Therefore, the reinforcing composite bar of fiber reinforced resin of the present invention is highly economical, and it is possible to supply a large quantity of reinforcing composite bars to the market. Accordingly, it is possible to have the reinforcing composite bars of the present invention come into wide use.
Further, according to the present invention, it is possible to manufacture a very strong curved reinforcing composite bar of fiber reinforced resin, the dimensional accuracy of which is high, without deteriorating the mechanical strength. Also, it is possible to manufacture a very strong curved reinforcing composite bar of fiber reinforced resin which is curved by a radius of curvature of not less than 2 m, and the dimensional accuracy of the curved reinforcing composite bar is high.
Therefore, it is possible to provide an inexpensive reinforcing composite bar of fiber reinforced resin, the demand of which will be expanded as a substitute material of the reinforcing steel bar or PC steel wire. It can be concluded that the reinforcing composite bar of the present invention is very applicable industrially.
Claims (19)
1. A reinforcing composite bar of fiber reinforced resin composed of a forming body comprising: a core portion; and a winding portion to form protrusions on a surface of the core portion, both portions being made of thermosetting material containing thermosetting resin and reinforcing fiber bundles, wherein the forming body is strained by 500 to 3000 µ/m when a tension is applied to the forming body.
2. The reinforcing composite bar of fiber reinforced resin according to claim 1, wherein the reinforcing fiber bundles of the winding portion are twisted by 10 to 50 turns per 1 m.
3. The reinforcing composite bar of fiber reinforced resin according to claim 1 or 2, wherein the winding portion is spirally formed at an angle of 65 to 85° with respect to the axial direction of the core portion.
4. A reinforcing composite bar of fiber reinforced resin composed of a forming body comprising: a core portion; and a winding portion to form protrusions on a surface of the core portion, both portions being made of thermosetting material containing thermosetting resin and reinforcing fiber bundles, wherein the core portion is twisted and the forming body is curved and strained by 500 to 3000 µ/m when a tension is applied to the forming body.
5. The reinforcing composite bar of fiber reinforced resin according to claim 4, wherein the core portion is twisted by 0.5 to 1 turn per 1 m.
6. The reinforcing composite bar of fiber reinforced resin according to claim 4, wherein the core portion is curved by a radius of curvature of about 2 to 20 m.
7. The reinforcing composite bar of fiber reinforced resin according to claim 1 or 4, wherein the winding portion is composed of at least one reinforcing fiber bundle containing resin that has been thermally cured.
8. A method of manufacturing a reinforcing composite bar of fiber reinforced resin comprising the steps of: forming a core portion by impregnating thermosetting resin into a plurality of reinforcing fiber bundles, the fiber direction of which is oriented in the longitudinal direction; forming protrusions on a surface of the obtained core portion by winding at least one reinforcing fiber bundle impregnated with thermosetting resin; and thermally curing the thus obtained forming body composed of the core portion and the protrusions while the forming body is being given a tension so that it can be strained by 500 to 3,000 µ/m in the axial direction.
9. The method of manufacturing a reinforcing composite bar of fiber reinforced resin according to claim 8, wherein a pair of jigs having a plurality of pins are attached to both end chuck portions of a filament winding device, and the reinforcing fiber bundles impregnated with thermosetting resin are arranged between the pins of the pair of jigs so as to form a core portion.
10. The method of manufacturing a reinforcing composite bar of fiber reinforced resin according to claim 8, wherein a reinforcing fiber bundle impregnated with thermosetting resin twisted by 10 to 50 turns per 1 m is wound on a surface of the core portion so as to form protrusions.
11. The method of manufacturing a reinforcing composite bar of fiber reinforced resin according to claim 8 or 10, wherein both ends of the forming body are fixed to a pair of jigs arranged at both ends of a stationary die made of metal, and the forming body is heated together with the stationary die while both ends of the forming body are fixed to the jigs, so that the thermosetting resin impregnated into the reinforcing fiber bundles is thermally cured, and the forming body is given a tension by the thermal expansion of the stationary metallic die and strained by 500 to 3,000 µ/m.
12. A method of manufacturing a reinforcing composite bar of fiber reinforced resin comprising the steps of: forming a core portion by impregnating thermosetting resin into a plurality of reinforcing fiber bundles, the fiber direction of which is oriented in the longitudinal direction; twisting the obtained core portion; forming protrusions on a surface of the obtained core portion by winding at least one reinforcing fiber bundle impregnated with thermosetting resin; fixing the forming body in a curved die curved by a predetermined radius of curvature; and thermally curing the forming body while the forming body is being given a tension in the axial direction so that it can be strained by 500 to 3,000 µ/m.
13. A method of manufacturing a reinforcing composite bar of fiber reinforced resin comprising the steps of: forming a core portion by impregnating thermosetting resin into a plurality of reinforcing fiber bundles, the fiber direction of which is oriented in the longitudinal direction; forming protrusions on a surface of the obtained core portion by winding at least one reinforcing fiber bundle impregnated with thermosetting resin; twisting the thus obtained forming body in the same direction as that of winding the forming body; fixing the forming body in a curved die curved by a predetermined radius of curvature; and thermally curing the forming body while the forming body is being given a tension in the axial direction so that it can be strained by 500 to 3,000 µ/m.
14. The method of manufacturing a reinforcing composite bar of fiber reinforced resin according to claim 12 or 13, wherein the core portion is formed while a reinforcing fiber bundle impregnated with thermosetting resin is spread between a plurality of pins arranged at both end chuck portions of the filament winding device and pins arranged in a pair of jigs having fixing portions to be fixed to the curved die.
15. The method of manufacturing a reinforcing composite bar of fiber reinforced resin according to claim 12 or 13, wherein the core portion is twisted by 0.5 to 1 turn per 1 m.
16. The method of manufacturing a reinforcing composite bar of fiber reinforced resin according to claim 12 or 13, wherein the core portion is curved at a radius of curvature of about 2 to 20 m.
17. The method of manufacturing a reinforcing composite bar of fiber reinforced resin according to claim 12 or 13, wherein the reinforcing fiber bundle is wound on a surface of the core portion at an angle of 65 to 85°
with respect to the axial direction of the core portion so as to form a winding portion.
with respect to the axial direction of the core portion so as to form a winding portion.
18. The reinforcing composite bar of fiber reinforced resin according to claim 1 or 4, wherein the thermosetting resin is epoxy resin, phenol resin or polyamide resin, and the reinforcing fiber is PAN-based, pitch-based or hybrid carbon fiber, aramid fiber or glass fiber.
19. The method of manufacturing a reinforcing composite bar of fiber reinforced resin according to claim 8, 12 or 13, wherein the reinforcing fiber is PAN-based, pitch-based or hybrid carbon fiber, aramid fiber or glass fiber, and the thermosetting resin is epoxy resin, phenol resin or polyamide resin.
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP06115002A JP3088061B2 (en) | 1994-05-27 | 1994-05-27 | Fiber reinforced resin composite reinforced material and method for producing the same |
| JP6-115002 | 1994-05-27 | ||
| JP6-115001 | 1994-05-27 | ||
| JP6115001A JP3064179B2 (en) | 1994-05-27 | 1994-05-27 | Curved fiber reinforced resin composite bar and method for producing the same |
| PCT/JP1995/001029 WO1995033109A1 (en) | 1994-05-27 | 1995-05-29 | Fibre reinforced resin composite reinforcing material and method for producing the same |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2191241A1 true CA2191241A1 (en) | 1995-12-07 |
Family
ID=26453627
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002191241A Abandoned CA2191241A1 (en) | 1994-05-27 | 1995-05-29 | Fibre reinforced resin composite reinforcing material and method for producing the same |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA2191241A1 (en) |
| WO (1) | WO1995033109A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2013138921A1 (en) * | 2012-03-23 | 2013-09-26 | Pultrall Inc. | Bent reinforcement rod having improved mechanical strength at the bending point thereof, and method for producing same |
| AT514390A1 (en) * | 2013-05-17 | 2014-12-15 | Asamer Basaltic Fibers Gmbh | rebar |
| US10576658B2 (en) | 2017-05-15 | 2020-03-03 | Morton Buildings, Inc. | System and method for embedding substrate in concrete structure |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FI103267B (en) * | 1996-05-23 | 1999-05-31 | Uponor Innovation Ab | Method of making a pipe joint and pipe joint |
| CN100411856C (en) * | 2006-09-29 | 2008-08-20 | 连云港中复连众复合材料集团有限公司 | Making process of molded curved GRP lattice |
| US20160052233A1 (en) * | 2013-04-05 | 2016-02-25 | Shikibo Ltd. | Composite lightweight fitting |
| CN103498535B (en) * | 2013-09-29 | 2016-02-17 | 江苏法尔胜泓昇集团有限公司 | Carbon fiber composite reinforcement material tabular cross section anchoring process |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1238205A (en) * | 1985-04-26 | 1988-06-21 | Cerminco Inc. | Structural rod for reinforcing concrete material |
| JPH0615078Y2 (en) * | 1986-09-22 | 1994-04-20 | 東京製綱株式会社 | Reinforcing material for concrete |
-
1995
- 1995-05-29 WO PCT/JP1995/001029 patent/WO1995033109A1/en active Application Filing
- 1995-05-29 CA CA002191241A patent/CA2191241A1/en not_active Abandoned
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2013138921A1 (en) * | 2012-03-23 | 2013-09-26 | Pultrall Inc. | Bent reinforcement rod having improved mechanical strength at the bending point thereof, and method for producing same |
| US9885181B2 (en) | 2012-03-23 | 2018-02-06 | Pultrall Inc. | Bent reinforcement rod having improved mechanical strength at the bending point thereof, and method for producing same |
| AT514390A1 (en) * | 2013-05-17 | 2014-12-15 | Asamer Basaltic Fibers Gmbh | rebar |
| US10576658B2 (en) | 2017-05-15 | 2020-03-03 | Morton Buildings, Inc. | System and method for embedding substrate in concrete structure |
| US10703014B2 (en) | 2017-05-15 | 2020-07-07 | Morton Buildings, Inc. | System and method for embedding substrate in concrete structure |
| US10843378B2 (en) | 2017-05-15 | 2020-11-24 | Morton Buildings, Inc. | System and method for applying stress to a reinforcement member |
Also Published As
| Publication number | Publication date |
|---|---|
| WO1995033109A1 (en) | 1995-12-07 |
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| Date | Code | Title | Description |
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| EEER | Examination request | ||
| FZDE | Discontinued |