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FRP Molding Process-winding Molding!

Jun 13, 2020

FRP molding process-winding molding! The winding molding process is to wind continuous fibers (or cloth tape, prepreg yarn) impregnated with resin glue on a core mold according to a certain rule, and then solidify and demold to obtain products. According to the different physical and chemical states of the resin matrix during fiber winding molding, it is divided into dry winding, wet winding and semi-dry winding. (1) Dry winding Dry winding is the use of prepreg yarn or tape treated with prepreg, which is heated and softened to a viscous flow state on the winding machine and wound onto the mandrel. Since the prepreg yarn (or tape) is professionally produced, it can strictly control the resin content (accurate to within 2%) and the quality of the prepreg yarn. Therefore, dry winding can accurately control product quality. The biggest feature of the dry winding process is the high production efficiency, the winding speed can reach 100 ~ 200m/h, the winding machine is clean, the labor and hygiene conditions are good, and the product quality is high. The disadvantage is that the winding equipment is expensive and requires additional prepreg manufacturing equipment, so the investment is large. In addition, the interlayer shear strength of dry winding products is low. 2) Wet winding Wet winding is the process of directly dipping the fiber bundle (yarn tape) into the core mold under tension control. The advantages of wet winding are: ① Cost is 40% lower than dry winding; ② The product has good air tightness, because the winding tension causes excess resin glue to squeeze out the air bubbles and fill the gaps; ③ The fiber alignment is good; ④When wet winding, the resin glue on the fiber can reduce fiber wear; ⑤High production efficiency (up to 200m/h). The disadvantages of wet winding are: ① resin waste is large, and the operating environment is poor; ② the amount of glue and the quality of the finished product are not easy to control; ③ there are fewer types of resin available for wet winding. (3) Semi-dry winding. Semi-dry winding is the process of fiber dipping, and a set of drying equipment is added to the winding to the core mold to remove the solvent in the dipped yarn. Compared with the dry method, the pre-drying is saved. Dipping process and equipment; compared with the wet method, it can reduce the bubble content in the product. Among the three winding methods, the wet winding method is the most common application; dry winding is only used in the high-tech, high-precision cutting-edge technology field . The advantages of fiber winding molding ① The winding law can be designed according to the product's stress status, so that the strength of the fiber can be fully exerted; ②High specific strength: Generally speaking, the fiber winding pressure container is compared with the steel container of the same volume and pressure , The weight can be reduced by 40-60%; ③High reliability: The fiber winding products are easy to realize mechanization and automatic production. After the process conditions are determined, the quality of the entangled products is stable and accurate; ④High production efficiency: the use of mechanized or automated production requires There are few operators, and the winding speed is fast (240m/h), so the labor productivity is high; ⑤ low cost: on the same product, several materials (including resin, fiber and lining) can be reasonably matched and recombined to achieve The best technical and economic effect. Disadvantages of winding forming ① The adaptability of winding forming is small, and products with any structure can not be wrapped, especially products with concave surfaces, because the fiber cannot be close to the surface of the core mold and overhead when winding; ② Winding requires a winding machine, core Mold, curing furnace, demoulding machine and skilled technical workers require large investment and high technical requirements. Therefore, only in mass production can costs be reduced and technical and economic benefits can be obtained. 1. Raw materials The raw materials for winding molding are mainly fiber reinforced materials, resins and fillers. (1) Reinforcement materials Reinforcement materials for winding molding are mainly various fiber yarns: such as non-alkali glass fiber yarn, medium alkali glass fiber yarn, carbon fiber yarn, high strength glass fiber yarn, aramid fiber yarn and surface felt, etc. (2) Resin matrix The resin matrix refers to the glue system composed of resin and curing agent. The heat resistance, chemical resistance and natural aging resistance of the winding products mainly depend on the resin properties, and also have a great influence on the processability and mechanical properties. The commonly used resins for winding molding are mainly unsaturated polyester resins, and sometimes epoxy resins, bismaleimide resins, polyurethane resins, etc. are used. For general civilian products such as tubes and cans, unsaturated polyester resins are mostly used. For winding products that require high mechanical strength, compressive strength and interlayer shear strength, epoxy resin can be used. Aerospace products mostly use bismaleimide resin with high fracture toughness and good moisture resistance. (3) Fillers There are many types of fillers, which can improve some functions of the resin matrix after being added, such as improving wear resistance, increasing flame resistance and reducing shrinkage. Adding hollow glass microbeads to the glue solution can increase the rigidity of the product, reduce the density and reduce the cost. When producing large-diameter buried pipelines, 30% quartz sand is often added to increase the rigidity of the product and reduce costs. In order to improve the bonding strength between the filler and the resin, the filler should ensure cleanliness and surface active treatment. The application scope of the winding process: aerospace, missile, military aircraft, underwater equipment, high-strength, light-weight high-pressure container, shell. Civil pipelines, storage tanks, light weight, corrosion-resistant, and low cost. Forming two parts of the winding process-space technology and civil parts.