Recently, there have been many earthquakes with a magnitude of more than 3 in some areas such as Sichuan, Tibet and Xinjiang. Fortunately, there are no casualties at present. In order to reduce the property loss and personal injury caused by the earthquake, the buildings in the area located in the earthquake zone have been strengthened to varying degrees. Among them, the most widely used material in the building reinforcement industry is carbon fiber cloth.
Strengthening principle of carbon fiber composites
Carbon fiber cloth is actually a unidirectional carbon fiber reinforced product woven from 12K carbon fiber silk. It is often used with impregnation glue to form carbon fiber composites. CFRP reinforced concrete structure has the characteristics of high strength, light weight, corrosion resistance, acid and alkali resistance, does not occupy the original building space, convenient construction and wide application. In terms of mechanical properties, the tensile strength of CFRP can reach 8-10 times that of ordinary reinforcement, but the weight is far lower than that of reinforcement. The increase of self weight of concrete structure during reinforcement can be basically ignored.
Scope of application
Although carbon fiber cloth has many advantages as a material for external reinforcement, it also has some weaknesses that are difficult to control. The main reason is that it is difficult to evaluate the possible risk of fire, man-made damage or other accidents on this material in the reinforcement design. Therefore, this material is only applicable to the reinforcement of the following projects: 1) the original structure and components strengthened are basically intact, but their ability to bear live load needs to be increased; 2) Due to design or construction errors, the original structure and components are less equipped with some tensile reinforcement or stirrups, which need to be reinforced (but it should be noted that the existing reinforcement ratio shall not be lower than the minimum reinforcement ratio specified in GB 50010); 3) To enhance the seismic capacity of the original structural members; 4) It is used for reinforcement of places with corrosive media.
Application example：Hardened bridge
Due to the potential safety hazards of the bridge body, the road bridge crossing Zhengxing street at No. 2 Road in Zhengzhou is reinforced with carbon fiber cloth, and hundreds of carbon fiber cloth are pasted on the top of the bridge bottom. (the picture shows the bottom of the road bridge)
Reinforced steel structure
Compared with the traditional repair methods in steel structures, CFRP reinforcement has obvious advantages. CFRP reinforcement basically does not increase the weight and size of the original structure. The most important thing is that CFRP reinforcement does not need opening and welding, will not cause damage to the steel structure, and ensure the strength and integrity of the original structure.
Application of carbon fiber composites in wind power
The high strength and light weight of carbon fiber cloth make it an ideal material for manufacturing wind turbine and windmill blades. The windmill blade with carbon fiber cloth is harder than the traditional windmill blade and has a longer service life, so as to produce more energy with less wind.
Concrete application of carbon fiber composites in wind turbine blades.
Application position and effect:
1. Main beam cap: significantly reduce the weight of the blade and improve the stiffness of the blade.
2. Skin surface: improve the ability of the blade to resist pressure and tension, and alleviate the corrosion of the environment to the blade.
3. Blade root:①Improve the fracture strength and bearing strength of root materials and reduce the pressure of root bolts. ②Increase the number of bolts, consolidate the new energy at the connection between blade and hub, and improve the static strength and fatigue strength.
4. Lightning protection system: the front and rear edges of the blade are specially designed to effectively avoid lightning stroke and ensure the relevant performance of the blade.
Near the blade tip: ①Reduce the weight and reduce the load on the hub; ②Through relevant methods and measures, the vibration direction and strength of the blade can be guaranteed.
