GB2175364A - Reinforcing member having projections - Google Patents

Abstract

A reinforcing member has at least one projection on its surface, which is formed by wrapping a cord- like material on the circumferential surface of a fibre-reinforced synthetic resin core 12, the cord-like material 6 being formed by twisting continuous fibre bundles at a pitch in the range of from 3 turns/ 10 cm to 15 turns/ 10 cm. The fibre bundles comprise glass, or carbon, or boron, or metal, or natural or synthetic fibres. <IMAGE>

Description

SPECIFICATION Reinforcing member having a projection on its surface The present invention relates to a reinforcing member made of a synthetic resin which is provided with at least one projection on the circumferential surface.

For the purpose of stabilizing rock in a tunnel, there has been known a technique that holes are formed in the rock and reinforcing members referred to as lock bolts made of steel are embedded in the rock. However, since the steel lock bolts are apt to cause corrosion under high temperature and high humidity condition in the tunnel thereby inviting reduction in strength and rigidity of the lock bolts, attention is paid to a lock bolt made of a synthetic resin which has corrosion resistance and good processability.

Also, for the purpose of reinforcing a concrete structure, attention is paid to a synthetic resin reinforcing member as a substitute member for steel bar, which is provided with at least one projection on its circumferential surface to increase connection to the rock or the concrete structure.

It is common that reinforcing fibers having a high tensile strength such as carbon fibers are contained in the synthetic resin reinforcing member to obtain a tensile strength same as or higher than the steel reinforcing member.

As a method of forming a projection on the circumferential surface of the fiber reinforced synthetic resin reinforcing member, there has been known a method of shaving the circumferential surface of the member (referred to, for instance, Japanese Unexamined Patent Publication No. 122655/1984). The shaving method has, however, disadvantage such that long fibers for reinforcement are cut when the reinforcing member is shaved whereby reduction in tensile strength in the longitudinal direction of the reinforcing member is caused, and the projection formed by shaving is easily broken.

The inventors of the present invention have got an idea of forming the projection by wrapping continuous fibers such as a glass roving on the circumferential surface of the reinforcing member. In studying formation of the projection, it has been found that a part of the continuous fibers such as the glass roving should be embedded in and closely contact with the circumferential surface in order to form the projection providing good adhesiveness to the circumferential surface. However, it was difficult in the conventional technique to form the projection having a sufficient height.

It is an object of the present invention to provide a reinforcing member in which at least one projection having sufficient heightness is formed in close contact with the surface of the reinforcing member made of a synthetic resin.

The foregoing and the other objects of the present invention have been attainted by providing a reinforcing member having at least one projection on its surface, said projection being formed by wrapping a cord-like material on the circumferential surface of a synthetic resin core material, characterized in that the cord-like material is a twisted cord formed by twisting continuous fiber bundles at a pitch in the range of from 3 turns/lO cm to 15 turn s/I0 cm.

In drawings: Figure 1 is a diagram showing an example of a method of producing the reinforcing member according to the present invention,; Figures 2a and 2b are respectively diagrams showing a state that twisted cords or nontwisted continuous fibers are adhered to the surface of a core material; and Figures 3a, 3b and 3c are respectively diagrams showing how the twisted cord is wrapped around the core material.

Preferred embodiments of the present invention will be described with reference to drawings.

Figure 1 shows a typical method of preparing the reinforcing member of the present invention.

Continuous fibers 1 for reinforcement, such as a mat, a roving and so on is introduced in a vessel containing a molten thermosetting resin or a thermoplastic resin to impregnate the resin in the fibers. The resinimpregnated fibers are fed to a squeezing device 4 to adjust an amount of the resin to be impregnated. The fibers are passed through a draw die 5 together with continuous reinforcing fibers 3 without impregnation of the resin, if necessary, whereby a core material having a predetermined shape in cross-section is continuously produced in a non-cured or a semi-cured state.In the non-cured or the semi-cured state of the surface of the core material, a twisted cord 6 which is formed by twisting a plurality of continuous fiber bundles such as glass rovings (hereinbelow referred to simply as a twisted cord) is wrapped on the surface of the core material so that at least one projection of the twisted cord 6 is formed as shown in Figures 3a to 3c. Then, the core material with the twisted cord are bonded together in the room temperature or in an oven 7, followed by pulling it in a pulling device 8 and cut it at a required length. Thus, the reinforcing member made of a synthetic resin is produced.

In order to wrap the twisted cord 6 around the core material 12 as shown in Figures 3a and 3b, the pulling device 8 is stopped until each wrapping operation for the twisted cord 6 is finished. Especially, in Figure 3a, the twisted cord 6 is cut for each single turn of the twisted cord 6. In Figure 3b, a plurality of turns of the twisted cord 6 is connected by the same single twisted cord 6 in the longitudinal direction of the core material without cutting the twisted cord 6. Figure 3c shows the core material on which the twisted cord 6 is wrapped in a spiral form. The spiral projection is formed by warpping the twisted cord 6 while the core material is continuously pulled.

Figures 2a and 2b respectively show a state of a twisted cord 10 attached to the circumferential surface of a core material 12 and a state a conventional glass rovings 11 are attached to the circumferential surface of the core material 12. The twisted cord 10 is formed by twisting two glass rovings having the same weight per unit length. The glass rovings 11 consist of two parallel glass rovings. In comparing the thickness t, of the twisted cord 10 with the thickness t2 of the glass rovings in parallel arrangement, there is a relation of t, > t2 and therefore, there is a relation r1 > r2. Namely, the twisted cord 10 does not tend to sink in the surface of the core material 12.Further, raised portions 13 in the twisted cord 10 can be firmly connected to the core material and a force of adhesion increases in comparison with the glass rovings 11 having a uniform press-contacting force. Accordingly, the projection formed by the twisted cord provides good adhesiveness to the core material and fairly high projection can be realized.

The twisted cord may be previously impregnated with a resin to be non-cured or a semicured state. If a resin permeable to the twisted cord is coated in non-cured state on the circumferential surface of the core ma teal, the twisted cord without impregnation of a resin may be wrapped around the core material. In a case that the twisted cord is wrapped around the core material, it is preferable to apply a tention to the twisted cord to increase adhesiveness between the core material and the twisted cord. The twisted cord may be one previously twisted, or may be twisted while the cord is wrapped around the core material. The number of continuous fiber bundles to be twisted to form the twisted cord depends on the outer diameter of the core material and the thickness of the twisted cord. The number of glass rovings is generally 2-10, preferably 2 to 4.It is desirable that the thickness of a continuous fiber bundle is selected from the range from 4 g/m-1O g/m where the core material is circular rod body and having a diameter of 1 cm. The number of pitch for twisting the twisted cord depends on the diameter of the core material, the thickness of the twisted cord and the number of continuous fiber bundles to be twisted. It is desirable for the twisted cord to have a pitch of 3 turns/10 cm-15 turns/l0 cm, preferably, a pitch of 5 turns/1Ocm-10 turns/10 cm when the twisted cord is twisted by using two continuous fiber bundles and the thickness of each bundle is in the range of 2 g/m-3 g/m.

As a bundle of continuous fibers which constitues the twisted cord, a glass roving formed by gathering glass fiber filaments or a tow formed by gathering carbon fiber filaments is used as a typical bundle of fibers.

The tow consisting of carbon fibers is preferably used when tensile strength is required.

Carbon fibers may be of acrylics or rayon series. A preferred shape of the core material is cylindrical or an angular column. However, it is possible to use the core material having a plate-like form having a flat shape in closssection. It is preferable that long reinforcing fibers such as a roving of glass filaments or a tow of carbon filaments are arranged in the central portion of the core material and, if necessary, reinforcing fibers in a continuous strand mat form is arranged on the circumferential portion of the core material. The core material may be formed in such a manner that the central portion of the core material is constituted by the conventional steel reinforcing member and a fiber reinforced synthetic resin is coated on the central part.

The reinforcing member of the present invention can be used as a lock bolt, a substitute member for a steel bar or various reinforcing members for a concrete structure and so on. Specifically, the reinforcing member of the present invention is applicable to construction and maintenance for, for instance, a marine structure such as the platform of an oil rig which requires high durability, a chemical plant, a traffic facilities such as a road, or a bridge which suffers salt damadge by, for instance, a snow-melting agent. Further, the reinforcing member of the present invention can be used as a seat of a beam for a fusion reactor or a linear motor car by utilizing nature of non-magnetization.The reinforcing fibers constituting the core material or the twisted cord of the present invention may be inorganic fibers such as boron fibers, various metal fibers and so on besides the carbon fibers or glass fibers; natural or synthetic fibers such as hemp, vinylon, aramid, polyamide, polyester and so on. The above-mentioned materials may be used independently or in any combination. The reinforcing fibers may be used as a chopped strand mat, a continuous strand mat, a surfacing mat, non-woven fabrics, cloth, bias cloth, a roving and so on. They may also be used independently or any combination. On the other hand, for the resin constituting the reinforcing member, when the reinforcing member is used for reinforcing a concrete structure, an epoxy resin or an epoxyaclyrate resin is preferably used since the resin has a resistance to alkali in the concrete material.

However, besides epoxy series resins, a thermosetting resin such as an unsaturated polyester resin, a phenol resin, and a thermoplastic resin such as a polycarbonate resin, polyvi nyl chloride, a polypropylen resin may be used. The reinforcing fibers are mixed in the core material in the range of from 40 to 80 vo1.%, preferably, from 60 to 80 vol.% to maintain sufficient strength and rigidity of the core material. Further, it is desirable that an amount of the resin impregnated in the projection formed by the twisted cord wrapped on the surcumferential surface of the core material is 50 vo1.% or higher.

Preparation Example 1 An unsaturated polyester resin is impregnated in 22 glass rovings each having a thickness of 4.45 g/m. The resin-impregnated glass rovings were passed in a draw die having a diameter of 8.2 mm to form a glass fiber reinforced circular bar as a core material.

A projection in a spiral form having a pitch of 10 mm was formed by wrapping around the core material a twisted cord formed by glass rovings impregnated with unsaturated polyester resin, while the core material in noncured or a semi-cured state was continuously pulled. Then, the core material having the projection was passed through an oven having a temperature of 80"C to cure the projection and the core material in one piece. The twisted cord formed by twisting two glass rovings (each having a thickness of 2.22 g/m) at a rate of 8 turns/10 cm was used. As a result, a reinforcing member (I) in which a spiral projection of 2 mm wide and 2 mm high was firmly attached to a glass fiber reinforced circular bar of a diameter of 8 mm at a pitch of 10 mm was obtained.

Preparation Example 2 The same operation as in the preparation I was carried out except that a twisted cord is prepared by twisting two glass rovings at a pitch of 15 turns/l0 cm, whereby a reinforcing member (II) in which a spiral projection of 2 mm wide and 2.5 mm high was firmly attached onto a glass fiber reinforced circular bar of a diameter of 8 mm at a pitch of 10 mm was obtained.

Preparation Example 3 The same operation as in the preparation 1 was carried out except that two glass rovings were warpped without twisting, whereby a reinforcing member (III) in which a spiral projection of 2.5 mm wide and 1 mm high was firmly attached to a glass fiber reinforced circular bar of a diameter of 8 mm at a pitch of 10 mm was obtained.

Preparation Example 4 The same operation as in the preparation example 1 was carried out except that two glass rovings without twisting were wrapped onto the core material so that the height of the projection was 0 mm, whereby a reinforcing member (1V) in which a spiral projection of 2.5 mm wide and 0 mm high was firmly attached to the glass fiber reinforced circular bar of a diameter of 8 mm at a pitch of 10 mm was obtained.

Example At the center of cubic concrete body having a side of 100 mm, the reinforcing members (I) and (II) were respectively embedded and fixed so as to pass through the cubic body. The cubic concrete body is fixed to a tension tester. One end of the reinforcing members is respectively inserted in an steel sleeve and a resin material is poured in the steel sleeve followed by curing the resin material. The ends of the reinforcing members are pulled through the sleeve to measure a strength of adhesion between the concrete body and the reinforcing members. The adhesion strength of the reinforcing member (I) was 150 kg/cm2 and the adhesion strength of the reinforcing member (II) was 135 kg/cm2.

Comparative Example Measurements were conducted in the same manner as in the example as to the reinforcing members (III) and (IV). The adhesion strength of the reinforcing member (III) was 120 kg/cm2 and the adhesion strength of the reinforcing member (IV) was 100 kg/cm2.

According to the present invention, a reinforcing member having at least one projection on the surface of the reinforcing member made of a fiber reinforced synthetic resin can be effectively obtained. The projection has a strong connecting force to the core material since the twisted cord is formed by twisting bundles of continuous fibers at an optimum pitch. Accordingly, the reinforcing member of the present invention imparts excellent effect as a lock bolt or a substitute member for a steel bar.

Claims (5)

1. A reinforcing member having at least one projection on its surface, said projection being formed by wrapping a cord-like material on the circumferential surface of a synthetic resin core material, characterized in that said cordlike material is a twisted cord formed by twisting continuous fiber bundles at a pitch in the range of from 3 turns/lO cm to 15 turns/10 cm.

2. A reinforcing member according to Claim 1, wherein said synthetic resin core material is a fiber reinforced synthetic resin core material.

3. A reinforcing member according to Claim 1, wherein said continuous fiber bundles are glass rovings formed by gathering glass fiber filaments or tows formed by gathering carbon fiber filaments.

4. A reinforcing member according to Claim 1, wherein said reinforcing member having the projection on its surface is a substitute member for a steel product to be used for a rein forced concrete structure.

5. A reinforcing member according to claim 1, substantially as described with reference to the drawings.