The fibers used for carbon fiber composite reinforcement must be continuous fibers. Among them, as the carbon fiber for load-bearing structure reinforcement, polyacrylonitrile-based (PAN-based) 24K and below 24K small bundle filament fibers must be selected, and large bundle filaments are strictly prohibited.

Carbon fiber is a new type of high-strength, high-modulus fiber with a carbon content of more than 95%. Carbon fiber has many excellent properties. Carbon fiber has high axial strength and modulus, low density, high specific performance, no creep, and high temperature resistance under non-oxidizing environment. Good fatigue resistance, specific heat and conductivity between non-metal and metal, small thermal expansion coefficient and anisotropy, good corrosion resistance, good X-ray transmission. Good electrical and thermal conductivity, good electromagnetic shielding, etc.

Compared with traditional glass fiber, Young's modulus of carbon fiber is more than 3 times. Compared with Kevlar fiber, the Young's modulus is about twice that of the Kevlar fiber. It does not melt or swell in organic solvents, acids and alkalis, and has outstanding corrosion resistance.

On February 15, 2016, China broke through the Japanese control blockade and developed high-performance carbon fiber. Among them, the tensile strength is above 3500 MPa; the tensile elastic modulus is from 230G to 430G.

The chemical properties of carbon fiber are similar to carbon. In addition to being oxidized by a strong oxidant, it is inert to general alkalinity. When the temperature in the air is higher than 400 ℃, there will be obvious oxidation, generating CO and CO². Carbon fiber has good corrosion resistance to general organic solvents, acids, and alkalis, does not melt and does not swell, and the corrosion resistance is outstanding. There is no problem of rust at all. Some scholars soaked polyacrylonitrile-based (PAN-based) carbon fiber in a strong alkaline sodium hydroxide solution in 1981. After more than 30 years, it still maintains the fiber shape.

Nowadays, the quality of fiber composite materials in the reinforcement and transformation projects on the market is diverse. In addition to the difference in the quality of fiber composite materials, the braided wires used for weaving carbon fiber cloth are also very different. At present, hot melt wire and cotton thread are mostly used as braided wire fixing and edge banding.

A hot-melt wire is a linear connecting material made of a polymer that can be melted by heating. When binding, the temperature can reach 150℃, and a good hot-melt wire can withstand the high temperature of four or five hundred.

The materials used for making hot-melt wires are mainly divided into polypropylene and polypropylene; the well-known carbon fiber manufacturers at home and abroad use hot-melt wires as braided wires. Such as Toray Japan, Toho Japan and Hummer Shanghai, etc.

Compared with the high cost of hot-melt thread, the use of cotton thread can save a lot of cost, but cotton thread is a slender thread spun from cotton fiber; it can not be compared with hot-melt thread in high temperature resistance and fatigue resistance.

Therefore, the service life of fiber composite reinforcement materials is currently inestimable. At present, there is no clear test data that can detect the service life of composite fibers. In terms of durability, it is only the service life of carbon fiber structural glue identification.