Introduction of new technology for FRP strengthening

Carbon fiber material introduction

Carbon fiber is a typical high-tech product with high strength, high modulus, high temperature resistance, corrosion resistance, fatigue resistance, creep resistance, conductivity, heat transfer and other characteristics. It is mainly used to prepare advanced FRP composite materials, widely used in aerospace, sports goods, industrial fields. With the decrease of carbon fiber cost and the breakthrough of advanced low cost composite manufacturing technology, the use of carbon fiber composite materials in civil engineering, as the most suitable FRP composite reinforcement material is increasing rapidly year by year.

FRP composite strengthening includes two types: carbon fiber reinforced polymer(CFRP) fabric and carbon fiber reinforced polymer (CFRP) strip. Compared with traditional reinforced concrete or steel-bonded concrete, carbon fiber has the advantages of space saving, simple construction, no need for site fixing facilities, easy construction quality assurance, no increase in structural size and weight, corrosion resistance and good durability. In addition, the adoption of this method can greatly improve the service life of buildings and reduce the cost of reinforcement. Therefore, carbon fiber as an epoch-making reinforcement material has attracted much attention and attention.

FRP strengthening

1.1 Carbon fiber fabric reinforcement
The strengthening technology of CFRP structure refers to the use of matching high-performance resin adhesive to paste CFRP on the surface of building structural components, so that both work together to improve the bearing capacity of structural components (bending and shearing), thus achieving the purpose of strengthening and strengthening the building.

The key technology of CFRP fabric reinforcement is:

1. The matching epoxy resin glue must be fully immersed in the carbon fiber cloth, so that all the fine carbon fiber filament bonding called the whole, the common force;

2, the bonding between the carbon fiber reinforcement system and the existing structures must be firmly formed.

Prestressed FRP laminate reinforcement

1.2 Prestressed FRP laminate reinforcement

Carbon fiber strip is a kind of one-way sheet reinforced by carbon fiber. Its molding process is to solidify the carbon fiber impregnated resin in the mold and continuously pultrusion molding. Using high quality carbon fiber materials and good basic resin, carbon fiber strip has high tensile strength, corrosion resistance, seismic resistance, impact resistance and other good properties. The unidirectional carbon fiber strip can fully exert the strength and elastic modulus of the carbon fiber, and can avoid the resin curing stage of the unidirectional carbon fiber fabric during construction. The strength utilization efficiency is high and the construction is convenient. The elastic modulus of CFRP strip is about 165 ~ 185GPa, and the tensile strength is 2400 ~ 2800MPa.

1.3 carbon fiber fabric reinforcement and prestressed CFRP laminate reinforcement comparison

FRP strengthening is convenient, low cost, no complex equipment input, during the construction period, can be used for various forms of foundation reinforcement.

The prestressed CFRP anchorage system can avoid the phenomenon of strain lag of CFRP by applying prestress to CFRP. It can effectively exert the strength of CFRP, enhance the bearing capacity of the structure, increase the bending stiffness of the flexural members, reduce the deflection of the original members, restrain the deformation and crack propagation of the components, and solve the contradiction between the high ratio of CFRP strength and elastic modulus.