Application and Connection Technology of Fiber Reinforced Composite Material Members

With the proposal of China's "carbon peak" and "carbon neutrality" goals, various industries have put forward higher requirements for the carbon emissions throughout the product life cycle, and product lightweighting is one of the most effective measures for energy conservation and emission reduction for the vast majority of products. Fiber Reinforced Plastic (FRP) has the advantages of lightweight, high strength, and customizable material properties, making it the primary choice for lightweight products. Compared with metal rods, FRP rods have excellent performance in specific strength, specific stiffness, corrosion resistance, and other aspects, and are widely used in various industries.

In the bridge engineering industry, all ultra large span bridges in the world currently use high-strength steel cables. As the span increases, it can lead to a decrease in stiffness, low bearing efficiency, and fatigue corrosion problems. To solve these problems, the use of FRP cables (usually composed of multiple FRP rods to form one FRP cable) instead of steel cables is a key research direction both domestically and internationally. The Tuohai River Bridge in Liaocheng, completed in 2021, is the world's largest span and the first domestically built CFRP cable car bridge, marking a milestone in the application of FRP cables in bridge engineering.

Reinforced concrete building structures are the most commonly used building structures in civil engineering, and the steel bars in them have problems such as high density, poor fatigue, and susceptibility to corrosion. Compared with steel bars, FRP bars have lighter weight, higher tensile strength, a thermal expansion coefficient closer to cement, and better corrosion resistance, which can significantly improve the durability of concrete structures. Therefore, FRP reinforced concrete is an important research direction in the field of civil engineering. In developed countries such as Europe, America, and Japan, the application of FRP reinforcement in civil engineering has developed rapidly.

The most important technology for the application of FRP rods, whether it is FRP cables or FRP bars, is the connection technology of FRP rods. The superiority of the mechanical properties of FRP members is mainly reflected in the axial direction, while the lateral performance is poor. Therefore, appropriate connection techniques must be selected, otherwise the static and fatigue strength of FRP members cannot be fully utilized. At present, the connection technology of FRP members mainly includes bonding and hybrid bonding, which are more suitable for lightweight and high-strength connection requirements.

Adhesive technology is a special process that requires a specialized quality management system to ensure the quality of adhesive joints. Yifa Bonding & Composite Research Institute is a leader in China's adhesive quality management system. Yifa Bonding & Composite Research Institute is a strategic partner of Fraunhofer IFAM in China, with four companies including Shanghai Yifa Adhesive Chemical Technology Co., Ltd., Yifa New Materials Research Institute (Jiangsu) Co., Ltd., Yifa New Materials (Qingdao) Co., Ltd., and Shanghai Yifa Business Consulting Co., Ltd. For over a decade, Yifa has introduced adhesive standards such as EN17460/DIN6701 and ISO21368/DIN2304 into China. Starting from the rail industry, it covers fields such as aviation, automotive, home appliances, electronics, shipbuilding, and construction, helping China's manufacturing industry establish and improve technical standards in adhesive applications. At the same time, through EAB training, EAS training, and EAE training, Yifa has trained a large number of adhesive operators, technicians, and engineers in China, greatly enriching the domestic adhesive talent. At present, Yifa Bonding & Composite Research Institute is also bringing training in composite repair and composite technicians to China. Through these adhesive quality management systems and adhesive training, the connection quality of FRP members can be greatly improved, and the application of FRP members can also be promoted.