RU2405092C2 - Composite reinforcement - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: composite reinforcement comprises bearing rod of low-module fibres and winding with ledges, besides bearing rod is arranged as reinforced with high-module fibres assembled into bundles evenly arranged in massif of low-module fibres. Ratio of linear densities of low-module fibres to high-module ones makes from 1.5 to 5.

EFFECT: high-module fibres have elasticity module, exceeding elasticity module of steel reinforcement, and are selected from carbon fibres, boric fibres, Kevlar fibres, fibres of ultrahigh molecular polymers.

4 dwg, 2 tbl, 11 ex

Description

The invention relates to construction, namely to non-metallic composite reinforcement, which is used for reinforcing heat-insulating wall structures, monolithic concrete and prefabricated structures, for use in structural elements of buildings in the form of separate rods, for reinforcing the soil of the base of buildings and structures, including the bases of highways and roads, for anchoring in the ground retaining walls and structures.

Known fiberglass reinforcement according to patent 2194135 (publ. 2002.12.10), containing a supporting rod of high-strength polymer material and a winding with ledges, which are made in the form of a bundle of threads, impregnated with a binder and spirally applied with interference. This type of reinforcement contains a supporting rod of high-strength polymer material (for example, fiberglass GOST 17139-79, SVM TU 6-06-1153-78), which refers to low-modulus glass fibers, providing reinforcement with an elastic modulus of up to 55,000 MPa and tensile strength up to 1000 MPa. When using this reinforcement for reinforcing concrete slabs, increased deflections are observed, which affects the quality of the products.

Known composite reinforcement according to patent No. 77310 (publ. 2008.10.20), comprising a supporting rod of high-strength polymer material and winding with strands of threads of the opposite direction of winding, and the ratio of the cross-sectional areas of the first winding bundle and the second winding bundle, wound in the opposite direction is in the range from 1 to 150, and the winding angle of the second winding cord is 92 ° -150 °.

The armature contains a supporting rod of high-strength low-modulus glass or basalt fiber.

Concrete products made using reinforcement of this type, unlike steel reinforcement, have increased deformability and crack opening width. This behavior of composite concrete products is due to the small modulus of elasticity.

The authors revealed that the elastic modulus is a measure of the stiffness of a material, resistance to the development of elastic deformations. In stress tests of composite concrete products with low-modulus reinforcement, such as road slabs, concrete and reinforcement do not work together. First, the concrete takes up the load, and then the reinforcement is included in the work. As a result of this, the product has increased deflections and crack opening widths. High strength properties of composite reinforcement due to the low modulus of elasticity in the products are not realized.

Comparative characteristics of composite and steel reinforcement are shown in table 1.

Table 1

№№ Characteristic Composite glass fittings Composite basalt rebar Steel reinforcement A-III one Tensile strength σ _in MPa 1000 1400 590 2 Elastic modulus E _r , MPa 55,000 75,000 200,000

The modulus of elasticity with a value of E _p = 200000 MPa satisfies the requirements for the product in terms of deformability, and with lower values of E _p <200000 MPa, the products have increased deformability and do not satisfy the requirements.

The disadvantage of this reinforcement is that the elastic modulus of composite reinforcement is lower than the elastic modulus of steel reinforcement, which leads to a deterioration in product quality and prevents the use of non-metallic composite reinforcement in concrete structures.

Known profile rod for concrete reinforcement (US 4620401 A, 04/04/1986) made of fiberglass, graphite, coal, aramid, polypropylene, polyester, or combinations thereof, impregnated with a thermosetting resin. This design of the rod allows the manufacture of reinforcement with different modulus of elasticity and tensile strength.

Rods made of glass fiber (E = 55000 MPa), polypropylene (E = 40000 MPa), polyester (E _p = 45000 MPa) are low-modulus products. The rods made of graphite, coal (E _p = 230,000 ... 600,000 MPa), aramid (E _p = 400,000-800,000 MPa) are highly modular products.

The disadvantage of this product is the uneven arrangement of the reinforcing fibers in the rod, leading to the manufacture of non-linear rods and impairing the strength of the product. The lack of data on the selection of the ratio of the densities of low and high modulus fibers does not allow to produce composite reinforcement with the necessary properties.

The present invention solves the problem of creating a composite non-metallic reinforcement with a tensile modulus of about or equal to 200,000 MPa.

To achieve the technical result, in a composite reinforcement containing a supporting rod of low-modulus fibers and windings with ledges, the supporting rod is made of reinforced high-modulus fibers with a linear density ratio of low-modulus fibers to high-modulus fibers from 1.5 to 5, with high-modulus fibers being bundled in uniformly arranged bunches in an array of low modulus fibers.

Distinctive features of the present invention from the aforementioned most famous one is that the supporting rod is made of reinforced high-modulus fibers with a ratio of linear densities of low-modulus fibers to high-modulus fibers from 1.5 to 5, and high-modulus fibers are bundled evenly in the array of low-modulus fibers.

Due to the presence of these features, a new design of high-strength composite reinforcement with an elastic modulus close to or equal to the elastic modulus of metal reinforcement has been created.

The increase in the strength of composite reinforcement is achieved by placing in a certain order in the array of low-modulus fibers of the supporting rod the fibers of high-strength and high-modulus fibers.

The location of high-modulus fibers is determined by the technology of a bezferless method for manufacturing composite reinforcement (patent RU 2287431), according to which 2 to 10 separate bundles are formed from roving threads after unwinding, then each bundle is separately impregnated with a polymeric binder, squeezed, stretched and formed into a reinforcement profile by combining roving bundles into a single rod when performing spiral winding with a winding cord. Adding high-modulus fibers to roving bundles allows, in accordance with the channel layout, to evenly place them in an array of low-modulus fibers.

The deviation of the arrangement of high-modulus fibers from the geometric center of the channel is within the size of one roving bundle. In this regard, the reinforcing fibers can be located both in the array of the supporting rod, and on its surface, with a uniform distribution around the circumference.

The calculated value of the effective elastic modulus of reinforcement can be determined, for example, according to the Voigt formula (book Pobedra S.E. Mechanics of composite materials. Moscow, Moscow State University, 1984)

E _e = E _f V _f + E _m (1-V _f ), where

E _e is the effective modulus of elasticity of the rod;

E _f - modulus of elasticity of high modulus fibers;

E _m is the elastic modulus of low modulus fibers;

V _f - bulk density of high modulus fibers.

It can be seen from the formula that the higher the characteristics of high-modulus fibers, the less they are needed to obtain composite reinforcement with an elastic modulus close to or equal to the elastic modulus of the metal reinforcement.

The proposed design is illustrated by the drawings shown in figures 1-4.

Figure 1 shows a General view of the composite reinforcement with one spiral winding.

Figure 2 shows a General view of composite reinforcement with spiral windings in the opposite direction of winding.

Figure 3 shows a cross section of a composite reinforcement with evenly spaced five bundles of high modulus fibers.

Figure 4 shows a cross section of a composite reinforcement with evenly spaced eight bundles of high modulus fibers.

The composite reinforcement comprises a supporting rod 1 (Fig. 1, 2), on which one winding 2 (Fig. 1) or two spiral windings 3 and 4 (Fig. 2) are located.

The supporting rod 1 is made of low-modulus glass or basalt fibers impregnated with a polymer binder. High-modulus fibers 5 (Figs. 3 and 4) are uniformly, in accordance with the channel layout of roving beams, located in an array of low-modulus fibers of the supporting rod 1. As high-modulus fibers, fibers of organic and inorganic origin, for example, carbon, boron, Kevlar, ultra-high molecular weight, can be used polymers that have a tensile modulus of more than 200,000 MPa. To obtain the necessary characteristics, the carrier rod can be made with different channel layout of roving bundles, for example, Fig. 3 shows a carrier rod including 5 rovings of high-modulus fiber, and Fig. 4 shows a carrier rod including 8 rovings of high-modulus fiber.

Composite fittings are made by the method of "needle traction" by pulling the fibers of the supporting rod through separate channels, followed by winding with a winding bundle. Low-modulus and high-modulus fibers are evenly distributed over the channels and impregnated with a polymer binder based on epoxy, polyester, vinyl ester and other synthetic resins that provide the necessary strength properties of the composite matrix. When used as a polymer component, for example, epoxy resin ED-20, the binder has the following composition:

- Epoxy resin ED-20-100 v.h.

- Hardener - isomethyl tetrahydrophthalic anhydride - 80 parts by weight

- Accelerator - Alkofen - 2 hours

- Modifying additive (product of the interaction of aliphatic resins with polydiisocyanates) - 20 parts by weight

In the case of working with polyesters, the following composition can be used:

- Polyester unsaturated resin "Camfest-05" - 95 parts by weight

- Accelerator NK-2-5 V.Ch.

After curing, the resulting rod is cut into pieces of the required length.

The supporting rod consists of an array of low-modulus fibers, for example glass (E _p = 55000 MPa) or basalt (E _p = 75000 MPa), and high-modulus fibers with an elastic modulus exceeding the elastic modulus of steel reinforcement (E _p = 200000 MPa), for example carbon fibers (E _p = 230,000 ÷ 800,000 MPa), boron fibers (E _p = 400,000 ÷ 800,000 MPa), Kevlar fibers (E _p = 150,000 ÷ 400,000 MPa), fibers of ultra-high molecular weight polymers (Er = 180,000 ÷ 450,000 MPa).

Below is an example of testing a composite basalt-plastic reinforcement with a diameter of 6 mm when reinforcing a support rod with carbon fibers with different modulus of elasticity. The purpose of the tests is to determine the optimal ratio of low-modulus and high-modulus fibers to create high-quality composite reinforcement with tensile modulus close to or equal to 200,000 MPa.

The test results are shown in table 2, where:

T _n - linear density of low-modulus fibers (unit - tex)

T _in - the linear density of high-modulus fibers (unit - tex).

The linear density of the fibers is determined according to GOST 6943-79 "Textile glass materials" by the formula: T = 1000 · ^m / _l , where:

m is the mass of an individual skein or segment (unit - gram).

l - the length of the thread, yarn, roving or piece (unit - meter).

According to the test results, it was found that the ratio of the linear densities of low-modulus and high-modulus fibers in the supporting reinforcement bar to ensure E _p = 200,000 MPa, depending on the high-modulus fiber used, varies from 1.5 to 5.

The proposed design of non-metallic composite reinforcement allows to reach the tensile modulus to the level of metal reinforcement equal to 200,000 MPa, while increasing the tensile strength.

The proposed composite reinforcement has the necessary quality characteristics that allow it to be widely used for reinforcing critical monolithic concrete structures.

TABLE 2 Example No. p / p Low modulus fibers High Modulus Fiber T _n / t _in E _r , MPa σ _p , MPa one Basalt roving RBN-1260 94510 1300 E _p = 95000 MPa T _n = 26400 Tex - - 2 Basalt roving RBN-1260 Carbon thread UKN-M-760 34.7 104400 1350 E _p = 95000 MPa E _p = 230,000 MPa T _n = 26400 Tex T _in = 760 tack 3 Basalt roving RBN-1260 Carbon thread UKN-M-760 17 201100 1830 E _p = 95000 MPa E _p = 230,000 MPa T _n = 26400 Tex T _in = 1520 tack four Basaltic Carbon thread roving RBN-1260 UKN-M-1600 16.5 113000 1370 E _p = 95000 MPa E _p = 345000 MPa T _n = 26400 Tex T _in = 1600 tack 5 Basaltic Carbon thread roving RBN-1260 UKN-M-1600 1.8 203400 1870 E _p = 95000 MPa E _p = 345000 MPa T _n = 26400 Tex T _in = 14400 tack 6 Basaltic Carbon thread roving RBN-1260 UKN-M-1600 2.75 202300 1850 E _p = 95000 MPa E _p = 500000 MPa T _n = 26400 Tex T _in = 9600 tack 7 Basaltic Carbon thread roving RBN-1260 UKN-M-1600 3.3 201900 1830 E _p = 95000 MPa E _p = 600000 MPa T _n = 26400 Tex P _in = 8000 tack 8 Basaltic Carbon thread roving RBN-1260 UKN-M-1600 4.1 200050 1790 E _p = 95000 MPa E _p = 700000 MPa T _n = 26400 Tex T _in = 6400 tack 9 Basaltic Carbon thread roving RBN-1260 UKN-M-1300 4.1 201300 1830 E _p = 95000 MPa E _p = 800000 MPa T _n = 26400 Tex T _in = 6400 tack 10 Glass Kevlar thread 34.7 55,000 1000 EU roving E _p = 150,000 MPa E _p = 55000 MPa T _n = 26400 Tex T _in = 760 tack eleven Glass Kevlar thread 6.95 57000 1100 EU roving E _p = 150,000 MPa E _p = 55000 MPa P _in = 3800 tack T _n = 26400 Tex

Claims (1)

Composite reinforcement containing a supporting rod of low-modulus fibers and windings with ledges, characterized in that the supporting rod is made of reinforced high-modulus fibers with a linear density ratio of low-modulus fibers to high-modulus from 1.5 to 5, and high-modulus fibers are collected in bundles uniformly located in the array low modulus fibers.

Images