WO1995013414A1

WO1995013414A1 - Multilayer interlocking braided reinforcement member

Info

Publication number: WO1995013414A1
Application number: PCT/US1994/009542
Authority: WO
Inventors: David S. Brookstein
Original assignee: Albany International Corp.
Priority date: 1993-11-10
Filing date: 1994-08-23
Publication date: 1995-05-18
Also published as: AU7637094A

Abstract

A reinforcing member of rebar (10) for use in, for example, reinforcing concrete, comprising a rod member (10) formed from braiding interlocking layers of reinforcing fibers (12) with an enlarged element (16) incorporated into the outer layer to create a surface protrusion (18, 20) to transfer loads from the concrete to the rebar. Resin may also be used with the braided structure to form a composite rebar. A core (342) may also be provided in the rod for reinforcement.

Description

MULTILAYER INTERLOCKING BRAIDED REINFORCEMENT MEMBER

FIELD OF THE INVENTION

The present invention relates to a multilayer 5 interlocking braided reinforcement member comprising high performance fibers for use in reinforcement applications such as the reinforcement of concrete.

BACKGROUND OF THE INVENTION

In construction applications, concrete has

10 excellent compression strength and is used universally in a variety of situations where compression is the dominate mode of stressing. However, concrete inherently is a relatively poor tensile bearing member. In cases of pure tensile loading, steel is

15 the material of choice. For bending loads a composite or hybrid structure of concrete and steel is generally used where the steel is used to pre-stress the concrete. In this regard, the steel is used typically as reinforcement bars or 'rebars' which are loaded

20 with significant tension, and then concrete is poured around the steel reinforcement. When the concrete has cured, the externally applied tensile loads in the steel are removed thus placing residual compression stresses in the concrete. The hybrid structure is

25 designed to perform so that when it is subjected to bending loads, tensile loads added to it are lower than the residual compression loads and the concrete remains in compression.

'.

Steel reinforced concrete is widely used for many

30 construction purposes. However, with time, the steel may corrode and the bond between the steel and the concrete may fail. In addition, there exist certain applications where it is either necessary or desirable to avoid the use of metal. For example, new transportation projects are envisioned which will be based on the principle of magnetic levitation. Accordingly, the guideways and supports should not contain any materials which might influence the magnetic or electrical fields, such as steel. There presently exist various high performance reinforcement fibers, i.e., aramid (also known under the trademark Kelvar) and carbon. These materials are both non-corrosive and non-magnetic. These may be provided in different shapes and forms. For example, a non-metallic type of reinforcement member is found in U.S. Patent No. 4,620,401 issued November 4, 1986. In this patent the center core 14 of the rod is formed by pultrusion to which a helical filament winding 16 is bonded thereto by way of a thermosetting material 46. In another example, that of U.S. Patent No.

5,092,727 issued March 3, 1992, there is shown the use of an elongated core 12 to which a tubular braided layer 14 is bonded to the exterior thereof. While these items may have application in the construction field there are some inherent problems with these types of structures. For example, typically the exterior helical ribs that are used to transfer loads are bonded with resins. Accordingly, the load transfer from the concrete to the reinforcement is dependent on the relatively weak chemical bonding of the resin. In addition, while increasing the cross sectional area of the pultruded sections will increase the strength of the rebar, the amount of stress transferred from the concrete to the rebar is minimized. This is due to the inherent inefficiency of transferring stresses from fiber to resin to fiber.

With regard to braided arrangements generally, there presently exists technology to provide a tubular interlocking braided fabric such as that disclosed in International Patent Publication No. W 091/10766, the disclosure of which is incorporated by reference.

There also exists a means for making a solid multilayer interlocking braided fabric. In this regard, commonly assigned U.S. Patent Application SN 073,882 filed June 9, 1993 entitled Braid Structure,

Now discloses such a means. The disclosure of this application is also incorporated by reference.

SUMMARY OF THE INVENTION It is therefore a principal object of the invention to provide for an effective reinforcing member or rebar which is non-metallic.

It is a further object to provide for such a rebar which can effectively transfer the stress across its entire cross section rather then relying upon a chemical bond between the core and a raised portion making up the ribs thereof.

A yet further object to provide for such a rebar which avoids the disadvantages of rebars heretofore discussed. The objects of the invention will be realized through the disclosure of the present inventions of a multilayer interlocking braid used to create a reinforcing bar. In this regard, the present invention provides for a reinforcing bar made out of high performance fibers or yarns such as aramid and carbon. This bar is made as a coreless braid with interlocking layers. At least one of the fibers or yarns used has a coarser linear structure then the rest and is braided in to provide a protrusion or rib portion of the rebar. In view of the interlocking of the layers, stress is effectively transferred to the center of the rebar. In one embodiment dry fibers are used. In other embodiments pre-impregnated yarns may be used having an intimate coating of resin which, for example, may be heated to cause the resin to flow and become cured or consolidated. This will provide a relatively strong composite structure. Alternatively, resin can be injected during the braiding of the rebar and subsequently cured or consolidated to provide a similar effect. To provide additional strength, a core formed of a plurality of fibers may also be provided extending axially through the rebar.

BRIEF DESCRIPTION OF THE DRAWINGS Thus, by the present invention, its objects and advantages will be realized the description of which should be taken in conjunction with the drawings wherein:

Figure 1 is a side perspective view of the braided rebar, incorporating the teachings of the present invention Figure 2 is a partially sectional perspective view of the rebar shown in Figure 1, incorporating the teachings of the present invention;

Figure 3 is a side perspective of the braided rebar having an increased rib arrangement, incorporating the teachings of the present invention;

Figure 4 is a partially sectional perspective view of the rebar shown in Figure 3, incorporating the teachings of the present invention; Figure 5 is a perspective view depicting the injection of resin into the rebar as it is braided, incorporating the teachings of the present invention; and

Figure 6 is a partially sectional perspective view of the rebar with a core of axial yarns.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning now more particularly to the drawings, in Figures 1 and 2 there is shown a fiber or yarn based reinforcement member or rebar 10. Such a rebar 10 may be used in reinforcing concrete which heretofore typically involved the use of steel reinforcement rods which commonly had raised ribs transferring stress throughout the bar.

Rebar 10 may be made of high performance fibers 12 such as that made out of aramid and carbon. The rebar is formed as a coreless braid having a multilayered structure wherein each layer is interlocked with the next in a manner as provided for in U.S. Application SN 073,882. The fiber or yarn 12 making up the interior layers or body 14 of the rebar 10 may be of generally the same cross section. About the exterior layer or surface of the body 14 is provided an enlarged fiber or yarn 16 having a significantly higher linear density then fibers 12. Fiber 16 may itself be a braided structure and is incorporated into the braided rebar 10. As shown in Figures 1 and 2, fiber 16 is incorporated in the form of helixes 18, 20, 22 and 24. Helixes 18 and 20 run parallel to each other and in an opposite direction to helixes 22 and 24 which similarly run parallel with respect to each other. At the point where helix 20 and 22, and 18 and 24 cross respective raised knuckles 26 and 28 exist. Where helix 18 and 22, and 20 and 24 cross respective raised knuckles 30 and 32 exist.

Fibers 12 substantially overlap the entire length of fiber 16 making up the helixes and incorporating them into the braid. The helixes 18, 20, 22 and 24 create a relatively large surface protrusion which serves to transfer the load from the concrete to the rebar 10. Since all of the fibers 12 and 16 are interconnected, stress is transferred throughout the rebar 10 without relying solely upon the chemical bonding of a resin to transfer the load, as heretofore discussed.

However, the present invention does provide in addition to the use of dry fibers (that is without adding resin) , the use of pre-impregnated fibers or yarns. These fibers are provided with an intimate coating of a resin such as thermoset epoxy or thermoplastic materials such as polyetheretherketone (PEEK) . After the pre-impregnated yarn fibers are braided as previously described, heat is applied to the structure to cause the resin to flow and cure (thermoset) or consolidate (thermoplastic) . No molding process is required since the braided structure is under tension with sufficient internal pressure to produce a composite structure having superior structural integrity.

As shown in Figure 5, during the braiding process, resin may be pumped or injected into the center of the braid via a tube member 34, as an alternative to pre-impregnated fibers. The resin flows from the center outward. The outside of the rebar 10 can then be brushed with exuded resin and then cured to provide the desired composite structure. Turning now to Figures 3 and 4, there is shown a rebar 100. Previous discussions with regard to rebar 10 equally apply in all respects to rebar 100 with the exception that the latter is constructed using an increased number of helixes to create even more surface protrusions to transfer the loads from the concrete. In this regard, four parallel helixes 102, 104, 106 and 108 of the higher linear density fiber 110 are provided. Running in the opposite direction to these are similarly four parallel helixes 112, 114, 116 and 118. The intersection of these sets of helixes created even greater area of surface protrusion of themselves in addition to the number of knuckles where they overlap.

The embodiment of Figure 6 is similar to the embodiment of Figures 1 and 2. Reinforcement member or rebar 300 is made of high performance fibers 312 braided into an interlocked multilayered system forming a body 314, and a plurality of enlarged fibers 318, 320, 322 and 324 forming helixes aboard body 314. The crossover of these yarns form knuckles 326, 328, 330 and 332. Importantly, the fibers 12 are braided about a plurality of yarn 340 extending in parallel to form a core 342. Yarns 430 may be made of the same material yarns 312 or 318-324. Preferably, the core for a rebar 300 having a normal diameter of 1/2 inch, is formed of about 24-36 yarns 340 extending in parallel, each yarn 340 having a diameter of about 1/64 inch. The yarns 340 may also be pre-impregnated with a resin with cures or consolidates these yarns with the yarns 312, 318-324 to form a solid structure.

Thus, by the present invention its objects and advantages are realized and although preferred embodiments have been disclosed and described in detail herein, its scope should not be limited thereby rather its scope should be determined by that of the pending claims.

Claims

What IS CLAIMED IS:

1. A reinforcing member comprising: a rod member formed from braided interlocking layers of reinforcing elements including an exterior layer; and protrusion means incorporated into the exterior layer of the braid, said protrusion means having a sufficient linear density to have it protrude from the exterior layer.

2. The invention in accordance with claim 1 wherein said protrusion means comprises an enlarged element having a greater cross section then the remainder of the elements forming the exterior layer.

3. The invention in accordance with claim 2 where said elements comprise reinforcing fibers

4. The invention in accordance with claim 3 wherein said protrusion means comprises criss¬ crossing helixes of enlarged fibers.

5. The invention in accordance with claim 4 wherein at least two parallel helixes of enlarged fibers criss-cross with at least two parallel helixes of enlarged fibers travelling in the opposite direction thereto.

6. The invention in accordance with claim 4 wherein at least four parallel helixes of enlarged fibers criss-cross with at least four parallel helixes of enlarged fibers travelling in the opposite direction thereto.

7. The invention in accordance with claim 2 wherein said reinforcing elements comprise high performance fibers and resin.

8. The invention in accordance with claim 7 wherein said enlarged element comprises a high performance fiber and resin.

9. The invention in accordance with claim 8 wherein said resin comprises a thermoset or thermoplastic material.

10. The invention in accordance with claim 9 wherein said resin is cured or consolidated to create a composite reinforcing member.

11. The invention in accordance with claim 2 which where in said elements comprise high performance fibers and said rod member is formed from said fibers and a resin to create a composite reinforcing member.

12. The invention in accordance with claim 1 further comparing a care for said rod member.

13. The invention in accordance with claim 12 wherein said core includes a plurality of parallel yarns.

14. The invention in accordance with claim 12 wherein said reinforcing elements are braided about said core.

15. A method of forming a reinforcing member comprising the following steps: forming a rod member from braided interlocking layers of reinforcing elements including an exterior braided layer and incorporating a protrusion member into the exterior layer of the rod member.

16. The invention in accordance with claim 15 which further includes the step of providing a protrusion member that has a cross section greater then that of the elements forming the exterior layer.

17. The invention in accordance with claim 16 which further includes the step of providing said enlarged element on the exterior layer in the form of criss-crossing helixes.

18. The invention in accordance with claim 17 which further includes the step of providing elements comprising fibers including a thermoset or thermoplastic material and applying heat thereto to cause the material to flow and cure or consolidate.

19. The invention in^•accordance with claim 18 which further includes the steps of injecting resin into the center of the rod member during braiding and coating the outside the reinforcing member with resin; and curing or consolidating said resin.

20. The invention in accordance with claim 15 wherein said layers are braided about a core.

21. The invention in accordance with claim 20 wherein said core is formed of a plurality of parallel yarns.