JP6553977B2 - Reinforcement braid structure and composite material using the same - Google Patents

Description

  The present invention relates to a reinforcing braid structure, particularly to a reinforcing braid structure suitable for concrete reinforcement and the like, and a composite material using the same.

  It is well known that concrete is strong in compression but weak in tension. Therefore, reinforcement with rebar is performed. Reinforcement as a reinforcing material is corroded by the neutralization of concrete, etc. It is necessary to maintain the weight of the reinforcing bar itself because the specific gravity is high and the weight load per unit area is large, and transportation and workability are greatly restricted There are issues such as, and rebar replacement reinforcement is being considered. As an alternative material, high-strength fiber reinforcements such as carbon fibers having higher tensile strength and lower specific gravity than rebar and para-aramids have been studied. For example, Patent Document 1 discloses braiding of an aromatic polyamide fiber as a fiber having a large tensile strength. Patent Document 2 discloses that the outer side of a core material made of a bundle of carbon fibers is braided with aromatic polyamide and bound with a binder. Patent Document 3 discloses that the elongation at break is improved by using carbon fibers in the form of braids (Patent Document 3; [0013] and FIG. 5). It is proposed in patent document 4 to make a knob in the inside of a braid or a twist, and to improve the adhesion performance with concrete.

JP 60-119853 A Japanese Unexamined Patent Publication No. Sho 63-4158 JP 2007-113346 A JP 2013-155089 A

However, although Patent Document 1 is a reinforcing material using, for example, eight round braids, there is a problem that a reinforcing material having a stress-strain curve close to that of a reinforcing bar cannot be obtained by this alone. In Patent Document 2, it is disclosed that carbon fiber is used as a composite of the both, that is, a core material and the outside is made of aramid fiber. In this case, the initial rigidity can be increased, but when the strain exceeds the breaking elongation of the carbon fiber, the carbon fiber breaks, so that a significant decrease in stress is seen and the original stress level is not restored. That is, there remains a problem that the stress can not be maintained in the area above the breaking elongation of the carbon fiber. Patent Document 3 discloses that the elongation at break is increased by using carbon fibers as braids. This means that the reinforced structure can withstand a greater deformation, and the deformation of the reinforcing structure. However, this is considered to be the effect of the deformation of the fiber structure in addition to the deformation of the fiber itself, but the effect of improving the elongation is not sufficient, and the breaking elongation at the reinforcing bar level has not been reached. Since patent document 4 makes a hoop inside a braid or a twisted yarn, it is difficult to use it as a reinforcing material having a stress-strain curve close to that of a reinforcing bar.
As described above, in the prior art, it is difficult to use a reinforcing material with a stress-strain curve close to that of a reinforcing bar, and this improvement has been desired.

  In order to solve the above-mentioned conventional problems, the present invention reinforces a stress-strain curve close to that of a reinforcing bar by increasing the elongation by using a high strength fiber such as a carbon fiber with high strength and low elongation as a reinforcing structure. Provided is a reinforcing braid structure which is suitable for reinforcement of concrete as a substitute for rebar, and is also applicable to other reinforcement applications other than concrete reinforcement as a substitute for rebar, and a composite material using the same.

The reinforcing braid structure of the present invention is a braid structure containing one or more reinforcing fibers having a tensile strength of 1 GPa or more and a breaking elongation of 1 to 8%, and the braid structure has a surface of the core yarn. The braid is covered, and the braid is composed of at least two layers of braids having different braid angles when the yarn axis direction is 0 degree.
The composite material of the present invention is characterized by comprising the above-mentioned reinforcing braid structure and a reinforcing matrix material.

  According to the present invention, a reinforcing material with a stress-strain curve close to that of a reinforcing bar by using a high strength fiber such as carbon fiber having a high strength and a low breaking elongation and increasing the breaking elongation as a reinforcing structure Thus, it is possible to provide a reinforcing braid structure that is suitable for reinforcing concrete as a substitute for reinforcing steel and is also applicable to other reinforcing applications other than concrete reinforcing as a substitute for reinforcing steel and a composite material using the same.

FIG. 1 is an example of a stress strain curve of carbon fiber, aramid fiber and reinforcing bar. FIG. 2 is an explanatory view schematically showing a reinforcing fiber structure according to an embodiment of the present invention. FIG. 3 is a stress-strain curve of one embodiment of the present invention. FIG. 4 is a stress-strain curve of the reinforcing braid structure of Example 1 and Example 2 of the present invention. FIG. 5: is a stress strain curve of the structure of Comparative Examples 1-3.

  According to the study of the present inventors, the mechanical characteristics of the rebar include (1) high rigidity, particularly high stress in the low elongation region, and (2) from the yield point to breakage. The stress is almost constant and the breaking elongation is relatively large. Fig. 1 shows an example of stress-strain curve of carbon fiber and aromatic polyamide (para-aramid fiber) as an example of reinforcing bar and high strength fiber (Source: Journal of the Fibers Society Vol. 51, No. 7 (1995) P299 ). As seen in FIG. 1, generally, organic polymer high-strength fibers such as aramid tend to have higher tensile strength compared to rebar, but lower rigidity in the low elongation region. Carbon fibers, on the other hand, have high tensile strength and rigidity equal to or higher than that of rebar, but have the problem of low breaking elongation. That is, each material has merits and demerits, and various measures are necessary to use it as a reinforcing material with a stress-strain curve close to that of a reinforcing bar. In FIG. 1, a PC steel wire is a tension material that gives tension to prestressed concrete, and is also called a high-strength steel wire or a piano wire. According to the present invention, it is possible to obtain a reinforcing braid structure having a stress-strain curve similar to the PC steel wire.

  The reinforcing braid structure of the present invention contains one or more reinforcing fibers having a tensile strength of 1 GPa or more and an elongation at break of 1 to 8%, and the surface of the core yarn is coated with a braided yarn; When the yarn axis direction is 0 degree, it is composed of at least two layers of braided yarns having different assembly angles. That is, the reinforcing fibers used in the braid structure of the present invention are selected from those having high strength and low elongation, and more preferably having a high elastic modulus (high rigidity). The tensile strength of the reinforcing fiber is preferably 1 GPa or more. More preferably, it is 2 GPa or more. The breaking elongation is 1 to 8%. The preferred elastic modulus is 100 to 800 GPa.

  Specific examples of fibers satisfying the above conditions include organic high-strength fibers such as carbon fibers, high-strength polyethylene fibers, para-aramid fibers, PBO fibers, high-strength PVA fibers, polyarylate fibers, and inorganic fibers (silica, alumina, Silicon carbide, inorganic fibers such as basalt fibers, etc. may be mentioned. Among these, carbon fiber that has an elastic modulus equal to or higher than that of a reinforcing bar and that can provide an elastic modulus similar to that of a reinforcing bar is most preferably used. The said fiber can be mixed as needed as 2 or more types, and can be used as a structure. The fibers to be mixed do not necessarily have to meet all the above requirements, and the main component fibers can be used if the above requirements are met. Here, the main component means 50% by mass or more of the reinforcing fiber.

  Next, in the present invention, in order to make the fiber structure for reinforcement have a tensile behavior similar to that of a reinforcing bar, ie, to approximate the stress-strain curve of the reinforcing bar shown in FIG. And (b) it considered about extending in the state which kept the stress of the yield point almost constant.

First, as a braided structure, a core yarn is provided at the central portion, and a multi-layered structure with two or more layers having different set angles is provided outside the core yarn. The core yarn is preferably any of the following.
(1) Untwisted aligned yarn,
(2) Sweet twist yarn of 50 T / m (T is the number of twists) or less
(3) The smallest braid angle in the structure (preferably, the braid angle is less than 10 degrees)
By setting it as such a structure, the elastic modulus of the standup of a braided structure can be made high. As a material of the core yarn, carbon fiber having a high elastic modulus is preferably used. Moreover, as a ratio of the core yarn, the total fineness of the core yarn is preferably 15 to 33% of the total fineness of the high-strength fibers of the braided structure. If it is less than 15%, the stress in the low elongation region is insufficient, and if it exceeds 33%, as will be described later, the stress when the core yarn breaks is undesirably low.

Furthermore, the braid of the present invention is preferably further designed as follows, whereby the breaking elongation of the braid structure can be increased and the change in stress in the stress-strain curve can be reduced. As a preferable requirement for this,
(A) The breaking load of the braided yarn constituting the layer assembly angle portion of the braided structure is equal to or greater than that of the yarn having a large braid angle.
(B) The breaking load of the core yarn is smaller than or equal to the breaking load of the braided yarn having a small assembly angle.
Can be mentioned.

  In the braided structure of the present invention, the number of layers having different set angles is N. Each layer is described in order from the inside to B1, B2,... BN, and the core portion is B0. Let a set angle of each layer be θ0, θ1, θ2... Θ3. Assuming that the total strength of the braids forming each layer is S0, S1, S2,... SN, a preferred braid structure of the present invention can be expressed as shown in Table 1 below.

  In Table 1, N is an integer of 2 or more. There is no particular limitation on the upper limit of N, which is about 4 mainly from the viewpoint of manufacturing cost. Fig. 2 is a schematic view showing an example of a braided structure (1) according to the present invention, which comprises a core yarn (2) composed of aligned yarns and three layers (3, 4 and 5) of braided structures different in assembly angle outside thereof. Indicated. In the present invention, as a preferred grouping angle of the multi-layered structure, a structure having a larger outer grouping angle (θ0 <θ1 <θ2 <... <ΘN) as shown in FIG. 2 is more preferable. In this example, the aligned core yarn (2) having a set angle θ of 0 ° and the inner layer set portion B1 (3) of the set angle θ1 outside thereof and the intermediate layer set portion B2 (4) of the set angle θ2 outside thereof Further, it is composed of a total of three layers of outer layer assembly parts B3 (5) having an assembly angle θ3 outside. That is, it is a solid multilayer assembly structure including an assembly of a core and a total of three layers, and the assembly angle is θ0 <θ1 <θ2 <θ3.

  The conditions (a) and (b) are preferably satisfied at the same time. Here, the breaking load force of yarns constituting the same braided part is a value obtained by totaling the strengths of the respective braided yarns, and in the case of the same yarn, (strength of one braided yarn) × (number of yarns used) It is represented by Therefore, in order to increase the breaking load, when using the same material, it is possible to increase the fineness of each braided yarn or to increase the number of yarns used (the number of strikes of the braid).

  Generally, when the braid is pulled, the apparent elongation is higher than the elongation of the raw yarn because the braid structure part (composition) is first stretched and deformed, but since the stress is small in this structural elongation region, the apparent appearance of the standup is The elastic modulus (rigidity) becomes low. When the core yarn is put in the set structure, the rigidity (elastic modulus) of the rising portion becomes high, but if the elongation of the yarn itself is small, the stress is greatly reduced when the yarn with a set angle of 0 breaks and the desired stress It does not become a strain curve. In the present invention, it has been found that a stress-strain curve close to a target can be obtained by adopting a multilayer structure having a plurality of angle parts and by designing the yarn to break in order from a smaller angle.

  Further, when the yarn of the layer having a small group angle is cut, it is desirable that the strength of the next group of angle layers is equal to or higher than the strength of the layer having the small group angle. When the breaking load is not sufficient, the entire braid is cut or the stress is greatly reduced, and the stress level when the portion with a small braid is broken does not recover. The order (position) of the braiding angles is not particularly limited, but a structure closer to the core has a smaller braiding angle and a larger braiding angle of the outer braid is more preferable. A preferred pair angle (θ) in the present invention is 10 to 60 degrees. In addition, it is also possible to insert warp threads (center thread, column thread) at the time of production of each layer, if necessary.

FIG. 3 is a stress-strain curve of one embodiment of the present invention. Hereinafter, the stress strain curve of FIG. 3 will be described.
(1) The stress distortion curve 6 of the first stage of FIG. 3 is mainly expressed by the core yarn (2) of FIG.
(2) The second stage stress-strain curve 7 of FIG. 3 is mainly expressed by the inner layer assembly portion B1 (3) of FIG.
(3) The third-stage stress-strain curve 8 of FIG. 3 is mainly expressed by the intermediate layer assembly B2 (4) of FIG.
(4) The fourth-step stress-strain curve 9 of FIG. 3 is mainly expressed by the outer layer assembly portion B3 (5) of FIG.

  The reinforcing braid structure of the present invention preferably has an elastic modulus of 50 to 500 GPa and a breaking elongation of 2.5 to 15%. Preferably, a carbon fiber is contained, the breaking elongation is 3 to 10%, and the tensile modulus is 100 GPa to 500 GPa. The tensile strength is preferably 0.5 GPa or more. Satisfying this range results in a stress-strain curve close to rebar, which can be suitably applied for rebar replacement.

  In the present invention, normal strength fibers other than reinforcing fibers (elongation: 10% to 40%, strength less than 1 GPa) can be contained in part of the braid structure as necessary. For example, a relatively high elongation yarn having a breaking elongation of 10% or more may be wound or coated as needed between the core yarn portion and the inner layer set portion in the center of the braid. The yarn is not necessarily high strength and is not limited to the material, and polyamide, polyester, polyolefin yarn, etc. can be used. This yarn can be expected to improve the buffer effect and the affinity with the matrix resin when the set during tension is tightened.

  In the present invention, at least a part of the reinforcing fibers constituting the braided structure is preferably impregnated and / or coated with a resin component, preferably a thermoplastic resin, from the viewpoint of prevention of fluff generation, processability, etc. As a result, the strength utilization factor of the structure can be increased. In addition, it is possible to select a resin in consideration of the affinity with the composite material in the post-process. The thermoplastic resin is not particularly limited, and resins suitable for use such as polyamide, polyolefin, polyester, polyurethane can be selected. The method for applying the resin is not limited either, and any of the melt coating method, the solvent solution of the resin, and the resin processing method using the dispersion liquid of the resin is possible.

  The invention comprises a composite material in which the above-mentioned reinforcing braid structure is used. The matrix material of the composite material is not particularly limited, and concrete, cement, various resin materials may be mentioned. Particularly preferred is a composite material in which the reinforcing fibers are carbon fibers and the reinforcing matrix is concrete.

  The present invention will be illustrated using the following examples, but the present invention is not construed as being limited to the following examples.

The evaluation method of the following example and comparative example was performed as follows.
<Strong elongation, tensile modulus>
The tensile strength and the breaking elongation of the braided structure were measured according to JIS L1013. The sample holding | maintenance at the time of a tension test used Shimadzu 5KN split drum type rope clamp. The strength is indicated by the maximum strength, and the elongation is indicated by the breaking elongation. This holder was corrected in the following manner at the initial stage of tension due to its low stress and a slight increase in elongation. The tensile elastic modulus is a stress-strain curve, and is represented by the slope of the largest slope in the initial part, and the point where the straight line of this slope intersects the axis of zero stress is defined as 0% elongation.
<Outer diameter of braid structure>
Measurements were made using calipers.
<Mass>
The braid was cut to a length of 50 cm, and the mass was measured and converted to a mass of 1 m length.
<Assembly angle>
The braid was observed under an actual microscope, the central stitch portion was observed (photographed), the crossing angle (corresponding to 2 × θN) of the braid was measured, and half the angle was taken as the braiding angle (θ).

The carbon fibers used in the following examples and comparative examples are as follows.
<Carbon fiber>
-Toray Industries, Inc., trade name "Torayca" T300-12K (carbon fiber), fineness: 800 Tex, tensile strength: 3530 MPa, tensile elastic modulus: 230 GPa, specific gravity: 1.76
-Toray Industries, Inc., trade name "Torayca" T300-3K (carbon fiber), fineness: 198 Tex, tensile strength: 3530 MPa, tensile elastic modulus: 230 GPa, specific gravity: 1.76
The carbon fiber yarn had 1 K = 66 Tex, and the single fiber strength was 3520 MPa.

Example 1
The two carbon fiber 12K yarns were drawn as a core yarn, and the carbon fiber 3K sweet twisted yarn (30 T / m) was used as a braid for 16 punching (first layer). At this time, polyester ordinary yarn (fineness; 1100 dtex) was wound while being wound around a core yarn. Further, 16 carbon fiber 3K sweet-twisted yarns were used to form a string (second layer) while winding polyester ordinary yarn (fineness: 1100 dtex) in the same manner. The carbon fiber of the obtained string yarn is composed of three layers of a core yarn, an intermediate layer (first layer), and an outer layer (second layer), and each breaking load is determined by the core yarn (including the warp yarn insertion portion). The breaking load of each part is 24 K, the first layer braided yarn 24 K, and the second layer braided yarn 48 K
Core yarn = first layer braided yarn <second layer braided yarn.
Table 2 shows the constitution and physical properties of the yarn produced.

(Example 2)
In the same configuration as in Example 1, a braid structure was manufactured by changing a combination (arrangement angle) of the first layer and the second layer. That is, 16 carbonized yarns (first layer) were made using two carbon fiber 12K yarns as an aligned core yarn and carbon fiber 3K sweet twisted yarn (30 T / m) as a braid. At this time, a polyester ordinary yarn (fineness; 1100 dtex) was wound while being wound around a core. Further, 16 carbon fiber 3K sweet-twisted yarns were used to form a string (second layer) while winding polyester ordinary yarn (fineness: 1100 dtex) in the same manner. At this time, by changing the gear of the braiding machine, the assembly angle was made larger than in the first embodiment. The carbon fiber of the obtained string yarn is composed of three layers of a core yarn, an intermediate layer (first layer), and an outer layer (second layer), and each breaking load is determined by the core yarn (including the warp yarn insertion portion). The breaking load of each part is 24 K, the first layer braided yarn 24 K, and the second layer braided yarn 48 K
Core yarn = first layer braided yarn <second layer braided yarn.
Table 2 shows the constitution and physical properties of the yarn produced.

(Comparative Examples 1, 2, 3)
As Comparative Example 1, only the core yarn of Example 1 was produced, and as Comparative Example 2, only a braided yarn having a set portion without core yarn was produced, and as Comparative Example 3, a sample in which only one layer was coated on the outer side of the core yarn was produced Compared with.
The conditions and results for each example and comparative example are summarized in Table 2.

  As is clear from Table 2, each Example of the present invention has a higher breaking elongation compared to the Comparative Example, and the elastic modulus is also lower than that of Comparative Example 2 in which the core yarn is absent. In both Examples 1 and 2, the modulus of elasticity was close to that of the raw yarn, and the target high elongation at break and high modulus of elasticity (high rigidity) were obtained.

  FIG. 4 shows the stress-strain curve of the reinforcing braid structure of Examples 1-2 of the present invention, and FIG. 5 shows the stress-strain curve of the structures of Comparative Examples 1-3. As is clear from FIGS. 4 to 5, the reinforcing braided structure of Examples 1 and 2 of the present invention can significantly increase the elongation compared to Comparative Examples 1 to 3, and a stress-strain curve close to a reinforcing bar It could be used as a reinforcing material.

Reference Signs List 1 braid structure 2 core yarn 3 inner layer set portion 4 middle layer set portion 5 outer layer set portion

Claims (14)

A braided structure comprising one or more reinforcing fibers having a tensile strength of 1 GPa or more and a breaking elongation of 1 to 8%,
In the braided structure, a braided yarn covers the surface of the core yarn,
The braid structure for reinforcement is characterized in that the braid is composed of at least two layers of braids having different braiding angles when the yarn axis direction is 0 degree.   The reinforcing fiber according to claim 1, wherein the reinforcing fiber is at least one selected from the group consisting of carbon fiber, high strength polyethylene fiber, para-aramid fiber, PBO fiber, high strength PVA fiber, polyarylate fiber and inorganic fiber. Braid structure.   The reinforcing braid structure according to claim 1, wherein the reinforcing fibers contain carbon fibers.   The said braided structure contains carbon fiber in core yarn, The total fineness of the carbon fiber of the said core yarn is 15 to 33% of the total fineness of the high strength fiber of the whole braided structure. The reinforcing braid structure described in 1.   The core yarn is at least one selected from non-twist aligned yarns, sweet twist yarns having a twist number of 50 T / m (T is the twist number) or less, and braided yarns having a set angle of 10 degrees or less. The reinforcing braid structure according to any one of the above.   The reinforcing braid structure according to any one of claims 1 to 5, wherein the breaking load of the core yarn is equal to or less than the breaking load of the braiding yarn of each layer of the braiding portion.   The reinforcing braid according to any one of claims 1 to 6, wherein the breaking load of the braided yarn constituting the braided portion of each layer is equal to that of a yarn having a larger braiding angle or larger in the yarn having a larger braiding angle. Structure.   The reinforcing braid structure according to any one of claims 1 to 7, wherein the reinforcing braid structure has an elastic modulus of 50 to 500 GPa and a breaking elongation of 2.5 to 15%.   The reinforcing braid structure according to any one of claims 1 to 8, wherein a part of the reinforcing braid structure contains a fiber of ordinary strength having a breaking elongation of 10 to 40% and a tensile strength of less than 1 GPa.   10. The reinforcing braid structure according to claim 9, wherein the ordinary strength fiber is wound or braided between a core yarn and an inner braided yarn.   The reinforcing braid structure according to any one of claims 1 to 10, wherein the reinforcing braid structure is impregnated and / or coated with a resin component.   The reinforcing braid structure according to claim 11, wherein the resin component is a thermoplastic resin.   A composite material comprising the reinforcing braid structure according to any one of claims 1 to 12 and a reinforcing matrix material.   The composite material according to claim 13, wherein the reinforcing braid structure contains carbon fibers, and the reinforcing matrix is concrete.

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