JPH07103631B2 - Long fiber reinforced composite material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a long fiber reinforced composite member obtained by arranging and embedding long fiber aggregates in an inorganic base material.

<Prior Art> Ferrocement is a typical one that reinforces an inorganic brittle matrix with conventional long fibers, and has been used for many years in many countries around the world.

However, since the reinforcing fiber is a steel wire, the steel wire inside tends to rust due to the neutralization of the cement base material and the ingress of acid, salt, etc. There was a problem when I damaged it.

For this reason, various new high-performance long fibers have been tried as substitutes, and even if added in a small amount, a reinforcing effect can be obtained, so that it is possible to obtain those having physical properties equivalent to or better than those of ferroecement. It was

However, these are generally more expensive than steel wire, and various measures are required to obtain a product having both strength and toughness with a small amount of addition.

For example, the present inventors have already proposed a long fiber reinforced cement-based member in which two or more kinds of long fibers having different breaking elongations are arranged in the same plane, which is high with a relatively small amount of fiber addition. It has toughness, is an excellent composite member, and has the advantages that the fracture mode can be predicted and the material can be designed using a theoretical formula.

<Problems to be solved by the invention> However, this method is one in which a bundle of a plurality of long fibers having different breaking elongations are arranged individually in the longitudinal direction, and the toughness under tensile or bending stress is obtained. Is improved, but b in FIG.
As shown in Fig. 4, a peculiar discontinuous sawtooth-like temporary stress decrease is observed in the stress-strain curve at break.

The object of the present invention is to reinforce such an inorganic brittle matrix with a long fiber aggregate, thereby providing excellent fracture toughness and strength, and discontinuous and stepwise stress during the action of tensile stress. The object is to provide a reliable composite material that does not deteriorate.

The purpose is to obtain an aggregate in which two or more kinds of long fibers having different break elongations are integrally joined in the longitudinal direction to a base material whose break elongation is equal to or less than that of the reinforcing fiber, and the longitudinal direction is the direction of tensile or bending stress. It is achieved by burying so as to substantially match with.

<Means for Solving Problems> The present invention will be described in detail below.

The base material used in the present invention is generally an inorganic substance generally used industrially such as Portland cement, gypsum, silicic acid, calcium, carbon and clay.

The long fibers to be used may be made of any material such as organic or inorganic, but high performance fibers such as carbon fibers, aramid fibers, alkali resistant glass fibers and high strength vinylon fibers are particularly preferred.

It is possible to use two or more kinds of different materials or fibers of the same kind but different in elongation at break in combination. These may be obtained by simply aligning the above-mentioned two or more types of fiber bundles with each other to form a bundle, or by burning, twisting or twisting them into a bundle.

The effect of joining in the present invention is as follows:
Further, as a result, it is shown as line a in FIG.

That is, in FIG. 1, curves a and b are deflection curves of the members obtained in Examples and Comparative Examples, respectively.

As can be seen from this figure, the member of the invention, namely the curve a
In the case of b, the stress gradually increases with the increase of the flexure to reach the maximum stress level, whereas in b, the fibers having different breaking elongations are individually broken, so that the stress sharply decreases with the increase of the flexure.

Further, although the final amounts of deflection of both are almost the same, a remarkable difference is observed in the bending properties and the stress levels of a and b.

This difference is due to, for example, the difference between the elongation and the tensile load curve when two or more types of long fibers having different breaking elongations are separately pulled and when they are integrally joined to form an aggregate and then pulled. Can be explained.

That is, the straight line d represents the carbon fiber having a low elongation at break, and the e represents the relationship between elongation and tensile load when the carbon fibers having a high elongation at break are individually pulled.

On the other hand, f is obtained by integrally joining the both with an epoxy resin to form an aggregate and then pulling.

That is, when f reaches a level at which the elongation reaches the same level as d, a partial breakage of the d fiber occurs, but the stress does not drop to the level of e at a stretch, and the e fiber having a relatively high breaking elongation around Due to the bonding effect of, the fracture elongation level of e is reached with a higher stress than the theory.

The shaded area in FIG. 2 confirms the effectiveness of the present invention,
It has an unpredictable effect.

Therefore, it is possible to bear a higher tensile stress than expected without causing a sudden decrease in stress as compared with the same member in which a or e is independently arranged in parallel.

The integration of the fiber bundles must have a stress transmitting action, but usually a resin is used.

When the inorganic base material is alkaline such as Portland cement or calcium silicate, it is necessary to use a combination of resin and fiber having good alkali resistance.

FIG. 3 shows an example of a method for disposing long fibers in the inorganic base material according to the present invention.

Reference numeral 1 in FIG. 3 denotes a fiber-reinforced inorganic member subjected to bending stress by a central one-point loading bending test.

2 is the neutral axis of the bending stress of the member (NN ′ in FIG. 3)
Line), where tensile stress acts (N- in Fig. 3)
Arranged so as to bear the tensile stress of the members in the portion below the N ′ line) and arranged at a position closer to the neutral axis (represented by the distance L ₁ from the neutral axis in FIG. 3). It is a long fiber installed. It is preferable that the long fiber has a higher tensile strength.

Further, it is preferable that the longitudinal direction of the long fibers is the same as the tensile or bending stress direction of the member since the effect of bearing the tensile or bending stress is the best. However, even if the longitudinal direction of the long fibers is not exactly the same as the tensile stress direction of the member, if the tensile or bending stress can be substantially beared, the respective directions may be slightly different.

3 is preferably arranged and arranged in the same longitudinal direction as 2 except that it has a smaller tensile strength and is located farther from the neutral axis (represented by the distance L ₂ from the neutral axis in FIG. 3). It is made of long fibers.

In the above drawings, the case where the long fibers are arranged in two layers is shown, but the present invention is not limited to this, and the long fibers may be arranged in three or more layers, or in a single layer arrangement. But it's okay. Moreover, you may arrange | position the different kind fiber combination aggregate separately.

Here, the tensile strength of the fiber in the present invention is expressed as the product of the tensile strength per unit cross-sectional area of the long fiber used and the cross-sectional area of the fiber arranged in the inorganic base material.

And the tensile strength and cross-sectional area are
It can be measured by the method of JIS standard R7601, and also for other fibers, it can be measured according to the same method.

If there is at least a relative size relationship between the long fibers having a large elongation at break and the long fibers having a smaller breaking elongation, a composite effect can be obtained. The relationship is more preferable because the combined effect is more effectively exhibited. When three or more kinds of long fibers are used, the above relationship can be seen in the one having the smallest breaking elongation and the one having the largest breaking elongation.

What is important in the present invention is that an aggregate formed by integrally joining two or more kinds of long fibers having different breaking elongations with a joining material having a stress transmitting property in the longitudinal direction is arranged at least substantially in the same direction with respect to tensile stress. That is.

Next, in the present invention, long fibers are usually used in the form of a bundle of hundreds to tens of thousands of single yarns having a diameter of several microns to several tens of microns.

Long fibers having different breaking elongations are integrally joined using a joining material.

At this time, as described in FIG. 2, what is necessary for the function of the bonding material is to bond due to the bonding effect of the bonding material even if the fibers having a small breaking elongation in the integrally bonded fibers are partially broken. The fibers have a bonding action of maintaining the integrity of one bundle until the fiber portion having a large breaking elongation breaks.

As a specific bonding material, a substance having such a bonding action can be used without particular limitation.

For example, epoxy resin, urethane resin, phenol resin,
Thermosetting and crosslinkable polymer substances such as unsaturated polyester resin, polyimide resin, various rubber polymers, and heat of vinyl acetate resin, polyvinyl alcohol, styrene resin, olefin resin, acrylic resin, polyester resin, polyamide resin, etc. A plastic polymer substance or the like is used.

These polymer substances are melted or dissolved in a solvent to impregnate the fibers, and desolvate, cool and solidify, and dry the fibers to fix the fibers together.

Furthermore, in order to improve the adhesiveness with the inorganic base material, the fiber is subjected to a surface treatment such as surface oxidation treatment, or a carboxyl-modified rubber polymer is further attached onto the epoxy resin layer as a polymer substance to be attached. A method or the like may be used.

In order to further improve the adhesion with the inorganic base material, fine sand or the like is further adhered to the surface impregnated with the above substance with resin or cement to give an anchoring effect to the inorganic base material. Good.

The shape of the long fibers used in the present invention is not limited to a linear one-dimensional shape, but it is also possible to form components such as a lattice shape, a mesh shape or a woven shape into a band shape and arrange the same in the same plane as the tensile stress or in the orthogonal plane. it can.

Particularly in the case of a mesh, when it is composed of entangled weave and two or more kinds of entangled fibers having different breaking elongations are arranged in the longitudinal direction of the fiber in the present invention, a fiber having higher strength and higher toughness A reinforcing member is obtained, which is preferable.

The embedding of the long fiber of the present invention into the inorganic base material may be carried out by a conventional method.

For example, a conventional stacking / embedding method may be used, or the base material may be preliminarily three-dimensionally assembled in the mold and then the base material may be injected and cured.

At this time, if defoaming is performed by vibrating with a vibrator or the like, the adhesion between the inorganic base material and the reinforcing fiber assembly becomes even tighter, and good mechanical properties can be obtained.

Further, the member of the present invention may be a plate-shaped member, a cylindrical member, a hollow plate, a block or the like member that is subjected to tensile stress or bending stress, and its shape is not particularly limited.

<Examples> Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

Example Pitch-based low-elasticity carbon fiber (consisting of about 4000 single yarns having a breaking elongation of 0.84% and a diameter of 11 microns) was similarly used as Pitch-based high-elasticity carbon fiber (breaking elongation of 0.43% and a single yarn of about 10 microns having a diameter of about 2000). (Consisting of a book), while being aligned, continuously impregnated with an epoxy resin solution containing a curing agent diluted with acetone and heat-cured at 130 ° C to integrally bond both fibers to form a straight line with a resin content of 37%. A long fiber aggregate was obtained.

The center of the cross section of this long fiber assembly is width 40 x height 20 x length 32
4 pieces at a distance of 2 mm (represented by L ₁ in FIG. 3) and a distance of 7 mm (L in FIG. 3 from the neutral axis of the cement-based bending member of 0 mm)
5) (denoted by ₂ ), and the composite system was arranged so that the longitudinal direction thereof was the same as the tensile stress direction and at equal intervals.

The total cross-sectional area of four L ₁ long fiber aggregates is a carbon fiber with a small elongation at break 0.01492 cm ² , and a carbon fiber with a large elongation at break.
0.00608cm ^2, also small carbon fiber 0.01865Cm ² of elongation at break Total length fiber assembly five L _2, a large carbon fiber 0.00760Cm ² elongation at break. The cement was early-strength Portland cement, the aggregate was river sand (maximum particle size 2.5 mm), and the water / cement ratio was 0.4 / 1 and the aggregate-cement ratio was 0.67 / 1.

The specimen was aged in wet air for 1 week, span 260 mm, loading speed 1
Stress when performing bending test with one point loaded in the center at mm / min ~
The deflection curve is shown in FIG.

The bending strength was 277 kgf / cm ² , and the maximum deflection was 3.3 mm.

In addition, the stress-deflection curve of the plain mortar, which was manufactured and bent in the same manner as above except that the reinforcing fiber was not laminated, is c in FIG.

The bending strength was 81 kgf / cm ² , and the maximum deflection was 0.3 mm.

Comparative Example The type and amount of the reinforcing fiber were exactly the same as those in the example, but the fibers were not integrally joined, and the fibers were alternately arranged in parallel and oriented in the longitudinal direction of the mortar specimen.

The stress-deflection curve obtained by carrying out a bending test after curing this specimen in the same manner as in the example is shown in b of FIG.

The bending strength was 210 kgf / cm ² , and the maximum deflection was 3.4 mm.

<Effects of the Invention> As described above, according to the present invention, two or more kinds of reinforcing fibers having different breaking elongations are integrally joined in the longitudinal direction and then arranged in the same direction with respect to the tensile or bending stress received by the member. By this extremely simple method, it is possible to obtain effective and rational reinforcing performance with a small amount of fibers, and to obtain a composite member having excellent fracture toughness and strength.

Also, like the reinforced concrete structure, it is possible to effectively and easily design a cross-section according to the application and load conditions, and it is also highly practical.

Further, even when carbon fiber is used as a reinforcing material, the surface of the carbon fiber is coated with a polymer or an organic-inorganic composite, and it comes into contact with embedded metals or members as pointed out in general carbon fiber short fiber reinforced cement products. There is no need to worry about galvanic corrosion of metals.

[Brief description of drawings]

FIG. 1 shows flexural stress-deflection curves of a long fiber reinforced inorganic member during a bending test in Examples and Comparative Examples of the present invention. FIG. 2 is a diagram showing a relationship between tensile load and elongation showing a combined effect of a long fiber aggregate in which two kinds of long fibers having different breaking elongations are integrally joined. FIG. 3 is a plan view and a cross-sectional view of the long fiber reinforced composite member. 1: Long-fiber reinforced composite member 2, 3: Long-fiber aggregate obtained by integrally joining break elongations having different tensile elastic moduli a: Provided with an aggregate in which two kinds of fibers having different break elongations are integrally joined Bending stress of specimen-deflection curve b: Bending stress of specimen in which two kinds of fibers having different breaking elongations are alternately arranged in parallel without being integrally bonded-deflection curve c: unreinforced inorganic base material alone Bending stress-deflection curve d: Relationship between tensile load and elongation of filaments with relatively large breaking elongation e: Relationship between tensile load of filaments with relatively small breaking elongation and elongation f: Difference of breaking elongation that the two types of relationship L ₁ of the tensile load-elongation of the long fiber assembly which is integrally joined to the long fibers, L _2: distance from the neutral axis of the cross-sectional center of the long fiber aggregate

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Claims (5)

[Claims] 1. A composite member in which reinforcing fibers are embedded in an inorganic base material and subjected to tensile or bending stress, and the base material is made of a base material whose breaking elongation is equal to or less than that of the reinforcing fibers.
The reinforcing fiber is composed of an aggregate formed by integrally joining two or more kinds of long fibers having different breaking elongations in the longitudinal direction, and the longitudinal direction of the aggregate is substantially coincident with the tensile or bending stress direction. A long-fiber-reinforced composite member, which is embedded as described above. 2. The composite member according to claim 1, wherein the base material is a cement material. 3. The member according to claim 1, wherein the long fibers are carbon fibers, alkali resistant glass fibers, aramid fibers or vinylon fibers. 4. The member according to any one of claims 1 to 3, wherein the two or more kinds of long fibers having different breaking elongations are all carbon fibers. 5. A composite member in which reinforcing fibers are embedded in a base material and subjected to tensile or bending stress, and the base material is made of a base material whose breaking elongation is equal to or less than that of the reinforcing fibers. It is composed of an aggregate formed by integrally joining two or more kinds of carbon fibers having different breaking elongations in the longitudinal direction,
Moreover, the long fiber reinforced composite member is characterized in that it is embedded so that the longitudinal direction of the aggregate substantially coincides with the direction of tensile or bending stress.