Preparation and mechanical property evolution research method of carbon fiber coated BFRP rib

Abstract

The invention discloses a preparation and mechanical property evolution research method of a carbon fiber coated BFRP (Boron Fiber Reinforce Plastic) rib, which mainly comprises the following steps of: preparing a hybrid fiber reinforced composite material rib (C / BFRP rib) from E51 epoxy resin with the volume fraction of 35%, carbon fiber with the fiber volume fraction of 65% and basalt fiber, coating the BFRP with the carbon fiber with the volume fraction of 20%, and coating the BFRP with the basalt fiber with the carbon fiber with the volume fraction of 20%; and finally, the C / BFRP rib is soaked in an alkaline solution (artificial preparation). The method is novel and reasonable in design, simple in test mode, low in operation difficulty and capable of effectively achieving test expectation. According to the research method, the alkaline solution is manually prepared, and the pH value of the solution can be effectively controlled, so that the mechanical property evolution law of the C / BFRP rib in the alkaline environment is researched, the test accuracy can be effectively ensured, the test error is reduced, and the application research of the BFRP rib in seawater and sea sand concrete members is supplemented.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical property test of fiber reinforced composite materials, and in particular to a method for preparing carbon fiber-wrapped BFRP bars and studying the evolution of their mechanical properties. Background Art

[0002] my country is rich in marine resources, such as seawater and sea sand, which provide broad application prospects for concrete structures. Because seawater and sea sand are rich in chloride ions, the erosion of chloride ions causes great trouble to the steel bars in reinforced concrete structures, so FRP bars reinforced seawater and sea sand concrete structures came into being. Basalt fiber reinforced composite (BFRP) bars have the advantages of good mechanical properties, resistance to chloride ion corrosion, green environmental protection, and low price. Its mechanical properties are better than those of glass fiber reinforced composite (GFRP) bars, and its elongation at break is higher than that of carbon fiber reinforced composite (CFRP) bars. BFRP bars have irreplaceable advantages in the construction of large-scale seawater and sea sand concrete structure projects. However, the strong alkaline environment in seawater and sea sand concrete will cause serious corrosion of BFRP bars, which will have an adverse effect on the mechanical properties of BFRP bars. Some scholars have proposed to solve the problem of poor alkali resistance by modifying BFRP bars.

[0003] Carbon fiber has high strength, high elastic modulus, and excellent alkali corrosion resistance. Outer packaging of carbon fiber is a relatively scientific method to solve the poor alkali resistance of BFRP tendons. Therefore, it is particularly important to study the degradation of mechanical properties of BFRP tendons wrapped with carbon fiber in alkaline solutions. At present, most of the research focuses on single fiber reinforced composite tendons, and their mechanical properties are studied through accelerated tests. The present invention mixes two different fibers, and prepares C / BFRP tendons by wrapping the internal BFRP tendons with carbon fiber. The specimens are immersed in solutions of different temperatures and different alkalinities to explore the degradation law of the mechanical properties of C / BFRP tendons in alkaline solutions. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing carbon fiber-wrapped BFRP tendons and studying the evolution of mechanical properties. The component design is innovative and aims to study the evolution law of the mechanical properties of C / BFRP tendons in a strong alkaline environment. At the same time, alkaline solutions with different pH values ​​are used for comparison, thereby improving the accuracy and efficiency of the test.

[0005] In order to solve the above technical problems, the present invention is achieved through the following technical solutions:

[0006] A method for preparing carbon fiber-wrapped BFRP tendons and studying the evolution of mechanical properties includes: 20% volume fraction carbon fiber outsourcing, E51 epoxy resin, C / BFRP tendons with a diameter of 6 mm and a length of 500 mm, alkaline solution (artificially prepared), calcium hydroxide, potassium hydroxide, sodium hydroxide, an immersion box, a heating device, an extensometer, a steel pipe, an expansion agent, and a loading device.

[0007] Optionally, C / BFRP bars are prepared using E51 epoxy resin with a volume fraction of 35% and carbon fibers and basalt fibers with a fiber volume fraction of 65%, wherein 20% of the fiber volume fraction is carbon fiber outer covering.

[0008] Optionally, after the C / BFRP reinforcement is prepared, both ends of the specimen are sealed with resin to prevent the solution from directly entering the reinforcement from the two end sections and causing errors.

[0009] Optionally, an alkaline solution with a pH of 10 is artificially prepared, with a ratio of calcium hydroxide: potassium hydroxide: sodium hydroxide = 0.0040 g / L: 0.0035 g / L: 0.0060 g / L.

[0010] Optionally, an alkaline solution with a pH of 13 is artificially prepared, with a ratio of calcium hydroxide: potassium hydroxide: sodium hydroxide = 118.5 g / L: 4.2 g / L: 0.9 g / L.

[0011] Optionally, the two alkaline solutions are allowed to stand for 1 day, and the supernatant is taken and its pH is tested with a pH meter until it is qualified.

[0012] Optionally, the test pieces are immersed in an alkaline solution of pH=10 and an alkaline solution of pH=13, respectively, the temperature environments of the solutions are room temperature, 40°C, and 60°C, respectively, and the test pieces are taken out after being immersed for 30, 60, 90, 180, and 360 days.

[0013] Optionally, after taking out the C / BFRP reinforcement, wipe the surface of the specimen clean with absorbent paper.

[0014] Optionally, both ends of the specimen are anchored and bonded with seamless steel pipes. The seamless steel pipe is 13 cm long and the effective length of the C / BFRP reinforcement is 24 cm. When anchoring, the expansion agent and water are mixed in a ratio of 3:1 and stirred evenly, and then poured into the steel pipe. After the expansion agent is solidified, a tensile test is performed with a loading rate of 2 mm / min.

[0015] Optionally, an extensometer is set centered within the effective length of each C / BFRP bar during loading, with a gauge length of 5 cm.

[0016] Optionally, a tensile test may be performed using a loading device.

[0017] The examples of the present invention have the following beneficial effects:

[0018] 1. The component preparation and research method design of this experiment are novel and reasonable, the experimental method is simple, the operation difficulty is small, and the experimental expectations can be effectively achieved.

[0019] 2. The research method of the present invention utilizes artificially prepared alkaline solution, which can effectively control the pH value of the solution, thereby studying the evolution law of the mechanical properties of C / BFRP bars in an alkaline environment, which can effectively ensure the accuracy of the test and reduce the test error.

[0020] Of course, any product implementing the present invention does not necessarily need to achieve all of the above advantages at the same time.

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a three-dimensional diagram of the components of the present invention; Figure 2 is a cross-sectional view of a component of the present invention; Figure 3 This is the C / BFRP reinforcement diagram during the tensile test of the present invention (dimension unit: cm); Figure 4 It is the test environment of the present invention; In the accompanying drawings, the components represented by the reference numerals are as follows: 1-carbon fiber, 2-C / BFRP reinforcement, 3-alkaline solution of pH=10, 4-alkaline solution of pH=13, 5-immersion box, 6-steel pipe, 7-heating device. Specific implementation method:

[0023] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0024] C / BFRP bars with a diameter of 6 mm and a length of 500 mm were used, and both ends of the specimen were sealed with resin to prevent the solution from directly entering the interior of the bar from the cross-sections at both ends and causing errors.

[0025] Artificially prepare an alkaline solution with a pH value of 10, with a ratio of calcium hydroxide: potassium hydroxide: sodium hydroxide = 0.0040 g / L: 0.0035 g / L: 0.0060 g / L; artificially prepare an alkaline solution with a pH value of 13, with a ratio of calcium hydroxide: potassium hydroxide: sodium hydroxide = 118.5 g / L: 4.2 g / L: 0.9 g / L. The two alkaline solutions were left to stand for 1 day, and the upper clear liquid was taken and its pH was tested with a pH meter until it was qualified.

[0026] The specimens were immersed in alkaline solutions of pH=10 and pH=13, respectively. The temperature environments of the solutions were room temperature, 40°C, and 60°C, respectively. The specimens were taken out after soaking for 30, 60, 90, 180, and 360 days. After the C / BFRP tendons were taken out, the surface of the specimens was wiped clean with absorbent paper, and the tensile strength test was carried out.

[0027] The tensile test of C / BFRP bars was carried out according to GB / T 30022-2013. The length of the C / BFRP bar specimen was 50 cm. The two ends of the specimen were anchored and bonded with seamless steel pipes. The seamless steel pipe was 13 cm long. The effective length of the C / BFRP bar was 24 cm. During anchoring, the expansion agent and water were mixed and stirred in a ratio of 3:1 and then poured into the steel pipe. After the expansion agent solidified, the tensile test was carried out. The loading rate was 2 mm / min. During loading, an extensometer was set in the center of the effective length of each C / BFRP bar, with a gauge length of 5 cm.

[0028] The above preferred embodiments are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. According to the content of this specification, many modifications and changes can be made. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing carbon fiber-wrapped BFRP tendons and studying the evolution of their mechanical properties, characterized in that: include: 20% volume fraction carbon fiber (1) is wrapped with E51 epoxy resin, C / BFRP reinforcement (2) with a diameter of 6 mm and a length of 500 mm, two alkaline solutions with different pH values ​​are prepared using calcium hydroxide, potassium hydroxide and sodium hydroxide, namely an alkaline solution with pH = 10 (3) and an alkaline solution with pH = 13 (4), an immersion box (5), a heating device (7), an extensometer, a steel pipe (6), an expansion agent, and a loading device.

2. The method for preparing carbon fiber-wrapped BFRP bars and studying the evolution of mechanical properties as claimed in claim 1, characterized in that: C / BFRP bars (2) are prepared using 35% E51 epoxy resin and 65% carbon fiber and basalt fiber by volume, wherein 20% of the fiber volume fraction of the carbon fiber (1) is externally coated.

3. The method for preparing carbon fiber-wrapped BFRP bars and studying the evolution of mechanical properties as claimed in claim 1, characterized in that: After the C / BFRP reinforcement (2) is prepared, both ends of the specimen are sealed with resin to prevent the solution from directly entering the reinforcement from the two end sections and causing errors.

4. The method for preparing carbon fiber-wrapped BFRP bars and studying the evolution of mechanical properties as claimed in claim 1, characterized in that: An alkaline solution (3) with a pH value of 10 is artificially prepared, and the proportion of calcium hydroxide: potassium hydroxide: sodium hydroxide = 0.0040 g / L: 0.0035 g / L: 0.0060 g / L.

5. The method for preparing carbon fiber-wrapped BFRP bars and studying the evolution of mechanical properties as claimed in claim 1, characterized in that: An alkaline solution (4) with a pH value of 13 was artificially prepared, with a ratio of calcium hydroxide: potassium hydroxide: sodium hydroxide = 118.5 g / L: 4.2 g / L: 0.9 g / L.

6. The method for preparing carbon fiber wrapped BFRP bars and studying the evolution of mechanical properties as claimed in claim 1, characterized in that: The two alkaline solutions were allowed to stand for 1 day, and the supernatant was taken and its pH was tested with a pH meter until it was qualified.

7. The method for preparing carbon fiber-wrapped BFRP bars and studying the evolution of mechanical properties as claimed in claim 1, characterized in that: The test pieces were immersed in an alkaline solution (3) with a pH value of 10 and an alkaline solution (4) with a pH value of 13, respectively. The temperature environments of the solutions were room temperature, 40° C., and 60° C., respectively. The test pieces were taken out after being immersed for 30, 60, 90, 180, and 360 days.

8. The method for preparing carbon fiber-wrapped BFRP bars and studying the evolution of mechanical properties as claimed in claim 1, characterized in that: After taking out the C / BFRP reinforcement (2), wipe the surface of the specimen clean with absorbent paper.

9. The method for preparing carbon fiber-wrapped BFRP bars and studying the evolution of mechanical properties as claimed in claim 1, characterized in that: The two ends of the specimen are anchored and bonded with a seamless steel pipe (6), the length of the seamless steel pipe is 13 cm, and the effective length of the C / BFRP bar (2) is 24 cm. During anchoring, the expansion agent and water are mixed and stirred in a ratio of 3:1 and then poured into the steel pipe. After the expansion agent is solidified, a tensile test is performed at a loading rate of 2 mm / min. During loading, an extensometer is set in the center of the effective length of each C / BFRP bar, with a gauge length of 5 cm, and a tensile test is performed using a loading device.

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