CN112324054A - Steel-continuous fiber composite bar and preparation method thereof - Google Patents

Abstract

The invention discloses a steel-continuous fiber composite bar and a preparation method thereof, wherein the steel-continuous fiber composite bar comprises a steel bar inner core, a continuous fiber layer arranged outside the steel bar inner core and a bar rib on the outer surface of the bar, and a bridging layer composed of chopped fibers and resin is arranged between the steel bar inner core and the continuous fiber layer. The rib spacing of the rib material is 1.5 times of the diameter of the rib material, the rib width is 23% -25% of the diameter, and the rib depth is 0.07-0.08% of the diameter. According to the invention, the chopped fiber reinforced resin is used, and the obtained modified resin is used for manufacturing the bridging layer, so that the cooperative working performance of the steel bar and the fiber is improved, and the production efficiency of the bar material is improved. The surface form of the reinforcement is optimized, controllable slippage between the composite reinforcement and the concrete is realized, and the fracture risk of the continuous fibers is reduced; meanwhile, the reasonable volume ratio of the reinforcing steel bars to the fibers ensures the secondary rigidity of the composite reinforcing steel bars after the reinforcing steel bars are subjected to yielding, reduces the decline amount of the strength of the reinforcing steel bars after the fibers are fractured, and further improves the safety performance of the structure.

Description

Steel-continuous fiber composite bar and preparation method thereof

Technical Field

The invention relates to the field of design and preparation of composite bars, in particular to a steel-continuous fiber composite bar for a structure.

Background

Reinforced concrete is the most widely applied and developed building material in the application engineering at present. However, the steel bars have the defect of easy corrosion, and the bearing capacity of the steel bars is reduced after corrosion, so that the structure fails. This not only shortens the life of the structure, but also increases the maintenance costs of the building. FRP (fiber Reinforced Polymer) is a new material emerging at the end of the last century and has the advantages of light weight, high strength and corrosion resistance. However, the FRP ribs are greatly limited in use in the construction industry due to the disadvantages of low elastic modulus and brittle failure.

Steel-continuous Fiber composite bars (SFCB) are novel composite bars formed by wrapping continuous fibers around the outside of a Steel Bar core and impregnating the Steel Bar core with resin. The SFCB has the advantages of high elastic modulus of the steel bars, high elongation and high strength and corrosion resistance of the FRP rib material, and the SFCB has the characteristic of higher secondary rigidity which is not possessed by the steel bars, so that the SFCB rib becomes a research hotspot gradually in recent years. However, the existing SFCB rib has the problem that the reinforcing steel bar and the external FRP are difficult to cooperatively bear force due to insufficient interfacial bonding force of the inner core reinforcing steel bar and the external composite material. In addition, the strength of the conventional SFCB ribs is sharply reduced after the fibers are broken, and the structural safety performance is seriously threatened. Therefore, a new design and preparation method of steel-continuous fiber composite bar for structure is needed.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide an SFCB (reinforced plastic band) rib which has strong bonding between an inner core of the steel bar and an external FRP (fiber reinforced plastic) material, controllable strength recession and can stably slide with concrete in the using process and a preparation method thereof, aiming at overcoming the defects of the prior art.

The technical scheme is as follows: the utility model provides a compound muscle of steel-continuous fibers, includes the bar inner core, sets up the bar rib at the outside continuous fibers layer of bar inner core and bar surface, its characterized in that: and a bridging layer consisting of chopped fibers and resin is arranged between the reinforcing steel bar inner core and the continuous fiber layer.

The material of the steel bar inner core is not lower than the second-grade steel, and the surface of the steel bar inner core is provided with threads.

The chopped fibers are basalt fibers or glass fibers, the average diameter is 15-20 mu m, the average length is 400-500 mu m, and the volume fraction of the chopped fibers in the bridging layer is 40-50%.

The preparation method of the steel-continuous fiber composite bar is characterized by comprising the following steps of:

processing a bridging layer on the surface of the steel bar inner core;

processing the continuous fiber layer on the bridging layer by adopting continuous fiber bundles to obtain a composite reinforcement material;

and (4) processing rib material ribs outside the composite rib material.

The method for processing the bridging layer on the surface of the steel bar inner core comprises the following steps:

mixing the chopped fibers and a resin to form a chopped fiber reinforced resin;

the obtained chopped fiber reinforced resin is coated on the surface of the steel bar core.

The method for processing the continuous fiber layer on the bridging layer by adopting the continuous fiber bundles comprises the following steps: selecting continuous fiber bundles, fully soaking in resin, uniformly distributing the continuous fiber bundles on the outer side of the steel bar inner core with the bridging layer, winding the outer side of a steel bar material by using plastic to form ribs, pultrusion, and curing molding to obtain the steel-continuous fiber composite bar.

Before processing the bridging layer on the surface of the steel bar inner core, the method also comprises the step of processing the surface of the steel bar inner core, wherein the surface processing method comprises the following steps:

and (3) carrying out dust removal and polishing on the surface of the steel bar, cutting ribs to be not more than 0.4mm, soaking the treated steel bar in a silane coupling agent alcoholic solution for 30-40 minutes, and drying at room temperature.

The continuous fibers are basalt fibers or glass fibers, and the volume ratio of the continuous fiber bundles to the reinforcing steel bars is not more than 1: 4.

The distance between the rib materials is 1.5 times of the diameter of the rib materials, the width of the rib materials is 23% -25% of the diameter, and the depth of the rib materials is 0.07-0.08% of the diameter.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) according to the invention, the silane coupling agent is used for modifying the inner core of the steel bar, so that on one hand, the free energy of the surface of the steel bar subjected to coupling treatment is obviously improved, the infiltration of resin is facilitated, and the bonding strength of a resin/steel interface is increased; on the other hand, the silicon functional group is bonded with the surface of the steel through hydrolysis condensation reaction, and the carbon functional group is tightly connected with a resin system through bonding of chemical reaction, so that the interface bonding property of the steel bar inner core and the outer layer composite material is improved, and the cooperative work of the steel bar inner core and the external fiber is ensured.

(2) The invention adopts the chopped fiber reinforced resin with the volume fraction of 40-50 percent to wrap the outside of the steel bar and serve as a bridging layer. On one hand, the homology of the materials of the bridging layer and the external continuous fiber layer is ensured, the organic combination of the composite bar inner core and the external fiber is enhanced, the connection performance of the steel bar and the external continuous fiber is improved, and the cooperative working performance of the steel bar and the fiber is improved; on the other hand, the treatment method simplifies the surface treatment process of the reinforcing steel bar, thereby simplifying the production process of the composite reinforcing steel bar and improving the production efficiency of the composite reinforcing steel bar.

(3) After the continuous fibers of the composite bar are broken, the strength is mainly contributed by the steel bars, and the strength attenuation of the bar material after the fibers are broken is large due to the overhigh content of the continuous fibers, so that the structural safety is influenced. The volume of the continuous fibers and the reinforcing steel bars is not more than 1:4, so that the secondary rigidity of the SFCB reinforcing steel bars after the reinforcing steel bars are yielded is ensured, the attenuation of the strength after the fibers are broken is reduced, and the structural safety and the practicability of the composite reinforcing steel bars are improved.

(4) The size of the bonding force between the composite rib and the concrete is influenced by the space, the width and the depth of the rib on the surface of the rib, meanwhile, the rigidity of the rib on the surface of the composite rib is small, so that the bonding force between the composite rib and the concrete is close to the limit stress born by the rigidity of the rib on the surface of the composite rib through designing the rib on the surface of the rib, macroscopically, the composite rib and the concrete generate stable relative sliding under the condition of ensuring the rib and the concrete to be intact (the peak stress is not attenuated). Therefore, the surface form of the reinforcement is optimized, so that the reinforcement and the concrete stably slide under high stress, the bonding force is slowly faded after the sliding, and the ductility and the safety performance of the structure are further improved.

Drawings

Fig. 1 is a schematic structural diagram of a steel-continuous fiber composite bar.

FIG. 2 is a schematic view of the surface morphology of a steel-continuous fiber composite bar.

FIG. 3 is a drawing and extruding process for manufacturing the steel-continuous fiber composite bar for structural use.

FIG. 4 is a stress-slip comparison of drawn test pieces of different rib depths.

FIG. 5 is a stress-slip comparison of drawn test pieces of different rib spacing.

FIG. 6 is a graph of stress-slip comparison for drawn test pieces of different rib widths.

In the figure: 1. a steel bar inner core; 2. rib teeth of reinforcing steel bars; 3. a continuous fiber layer; 4. a bridging layer; 5. wrapping the inner core of the steel bar with the bridging layer; 6. an SFCB rib; 7. arranging yarns; 8. a yarn arranger; 9. a first glue tank; 10. a second glue groove; 11. a pultrusion die; 12. electrically winding a plastic tape; 13. a constant temperature curing oven; 14. a traction device.

Detailed Description

The technical solution of the present invention is described in detail below, but the scope of the present invention is not limited to the embodiments.

Example 1:

as shown in fig. 1, the SFCB bar 6 of the present invention includes a bar core 1, a continuous fiber layer 3 and a bridging layer 4, wherein the bridging layer 4 is wrapped around the bar core 1, the bar core 1 and the continuous fiber layer 3 are organically formed into a stressed whole through the bridging layer 4, and a bar rib is provided on an outer surface of the bar.

Totally preparing 6 groups of SFCB ribs 6 with different parameters, wherein the specific parameter design is shown in a table 3, and the preparation method of the SFCB ribs is as follows:

(1) the rib tooth height of the twisted steel is polished to a preset height, decontamination treatment is carried out, and the mechanical properties of the steel bar inner core after primary treatment are shown in table 1. The inner core steel bar is soaked in the silane coupling agent alcoholic solution for 30 minutes, and then is dried at room temperature.

(2) Selecting chopped basalt fibers with a preset specification, reinforcing epoxy resin, placing the resin reinforced by the chopped basalt fibers in a first glue groove 9, and enabling the steel bar in the step (1) to pass through the first glue groove 9 to obtain the steel bar inner core 5 coated with the bridging layer.

TABLE 1

Nominal internal diameter/mm	Rib height/mm	Yield strength/MPa	Modulus of elasticity/GPa	Ultimate strength/MPa
					10.5	0.35	420	210	640

(3) And selecting a set amount of basalt continuous fibers (the specifications of the continuous fibers are tex, the 2400 ultimate strength is 2100MPa, and the elastic modulus is 85GPa), and allowing the basalt continuous fibers to enter a second glue groove 10 through a yarn arranger 8 to be fully soaked in epoxy resin. And (3) uniformly distributing the basalt continuous fibers soaked with the resin on the periphery of the inner rib prepared in the step (2) through a creeper, performing pultrusion, winding the outer side of the rib material by using plastic to form ribs, and curing through a constant-temperature curing furnace to prepare the SFCB rib. The external surface morphology parameters of the prepared steel-continuous fibers are shown in table 2.

TABLE 2

TABLE 3

Numbering	Volume ratio of basalt continuous fiber to steel bar	Bridged layer chopped fiber volume fraction	Nominal diameter/mm of composite rib
				a	1:4.0	45％	13
b	1:3.2	45％	13
				c	1:4.0	30％	13
d	1:4.0	40％	13
				e	1:4.0	50％	13
f	1:4.0	60％	13

The obtained steel-continuous fiber composite bar was subjected to a tensile test, and the test results are shown in table 4:

TABLE 4

Note: strength retention ═ strength after fiber fracture/maximum tensile strength

As can be seen from Table 4, when the parameters of the steel-continuous fiber composite bar are within the design range of the present invention (i.e., the volume ratio of the continuous fiber bundle to the steel bar is not more than 1:4, and the volume fraction of the chopped fibers in the bridging layer is 40% -50%), the prepared composite bar has high maximum tensile strength, significant secondary stiffness, strength decline after fracture of the outer layer of the continuous fiber composite is less than 20%, and the failure modes of the bar are yield, fiber fracture and ductile failure of the steel bar. When the volume ratio of the continuous fiber bundle to the reinforcing steel bar is more than 1:4, the embodiment shows that the strength is reduced by nearly 30% after the continuous fiber is broken, and the structural safety is threatened; when the volume fraction of the chopped fibers in the bridging layer is more than 40-50%, the failure mode of the composite bar is changed into that the reinforcing bar is debonded from external fibers, and the maximum tensile strength is sharply reduced. In addition, the method improves the production efficiency of the rib material by about 10 percent.

Example 2:

3 groups of steel-continuous fiber composite bars are prepared by the preparation method in the example 1, and the preparation parameters of the composite bars are consistent with those of the test piece a in the example 1, namely: the volume ratio of the continuous fiber bundles to the reinforcing steel bars is 1:4, and the volume fraction of the chopped fibers in the bridging layer is 45%. The design of the outer surface parameters of the bar is shown in table 5. A self-mixing concrete pouring standard drawing test piece is selected, and the compressive strength of the self-mixing concrete is 41.7 MPa.

TABLE 5

After 28 days of maintenance, the three groups of test pieces are subjected to drawing tests, and the test results are summarized in fig. 4 to 6, wherein fig. 4 is a stress-slip comparison graph of the drawing test pieces with different rib depths, fig. 5 is a stress-slip comparison graph of the drawing test pieces with different rib pitches, and fig. 6 is a stress-slip comparison graph of the drawing test pieces with different rib widths. The summary result shows that when the appearance form parameters of the composite reinforcement are in the range of the patent requirement, the bonding strength between the reinforcement and the concrete is relatively high, and when the concrete and the reinforcement slide relatively, the bonding stress between the two materials can be kept relatively stable.

Therefore, the SFCB steel bar prepared by the parameters selected by the invention has good bonding property of the steel bar and the external composite material, good synergetic stress property and obvious secondary rigidity. After the fiber is broken, the strength retention rate of the rib material reaches more than 80%, the safety of the structure is guaranteed, and the practicability of the composite rib material is improved. Meanwhile, the process of bridging the inner core and the outer continuous fiber layer of the steel bar is simplified, and the production efficiency of the composite bar is improved. When the bonding stress between the reinforcement and the concrete reaches the peak value, the characteristic that the rigidity of the outer resin is small is utilized, so that the reinforcement and the concrete slide and the bonding stress is relatively stable, the ductility of the structure is improved, the fracture risk of the composite reinforcement is reduced, and the safety of the structure is further ensured.

Claims (10)

1. The utility model provides a compound muscle of steel-continuous fibers, includes the bar inner core, sets up the bar rib at the outside continuous fibers layer of bar inner core and bar surface, its characterized in that: and a bridging layer consisting of chopped fibers and resin is arranged between the reinforcing steel bar inner core and the continuous fiber layer.

2. The method of claim 1, wherein the rib spacing is 1.5 times the rib diameter, the rib width is 23% -25% of the diameter, and the rib depth is 0.07-0.08% of the diameter.

3. A steel-continuous fibre composite bar according to claim 1, wherein the chopped fibres have an average diameter of 15 μm to 20 μm and an average length of 400 μm to 500 μm, the volume fraction of chopped fibres in the bridging layer being 40% to 50%.

4. A steel-continuous fibre composite bar according to claim 3, wherein said chopped fibres are basalt fibres or glass fibres.

5. The steel-continuous fiber composite bar as claimed in claim 1, wherein the material of the inner core of the steel bar is not lower than that of the secondary steel, and the surface of the steel bar has threads.

6. The preparation method of the steel-continuous fiber composite bar is characterized by comprising the following steps of:

processing a bridging layer on the surface of the steel bar inner core;

processing the continuous fiber layer on the bridging layer by adopting continuous fiber bundles to obtain a composite reinforcement material;

and (4) processing rib ribs on the outer surface of the composite rib.

7. The method as claimed in claim 6, wherein the method for processing the bridging layer on the surface of the steel bar core comprises the following steps:

mixing the chopped fibers and a resin to form a chopped fiber reinforced resin;

the obtained chopped fiber reinforced resin is coated on the surface of the steel bar core.

8. A method according to claim 7, characterized in that the continuous fibre layer is processed with continuous fibre tows on the bridging layer by: selecting continuous fiber bundles, fully soaking in resin, uniformly distributing the continuous fiber bundles on the outer side of the steel bar inner core with the bridging layer, winding the outer side of a steel bar material by using plastic to form ribs, pultrusion, and curing molding to obtain the steel-continuous fiber composite bar.

9. The method as claimed in claim 6, further comprising the step of treating the surface of the steel bar core before processing the bridging layer on the surface of the steel bar core, wherein the surface treatment is performed by:

and (3) carrying out dust removal and polishing on the surface of the steel bar, cutting ribs to be not more than 0.4mm, soaking the treated steel bar in a silane coupling agent alcoholic solution for 30-40 minutes, and drying at room temperature.

10. The method of claim 8, wherein the continuous fibers are basalt fibers or glass fibers, and the volume ratio of continuous fiber bundles to rebar is no greater than 1: 4.

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