Composite fan blades are key components of wind power generation system, which directly affect the performance of the whole system, and have long-term weather resistance and reasonable price in an outdoor environment. Therefore, the blade design and manufacturing quality level is very important, is regarded as the key technology and technical level of wind power generation system.

The traditional composite wind turbine blades are manufactured by hand lay-up (Hand lay-up).

Hand lay-up process is mainly characterized by manual operation, open die forming (resin and reinforced fiber in the molding process should be completely exposed to the operator and the environment), low production efficiency and resin curing degree (resin chemical reaction degree) tend to be low, suitable for product batch smaller, quality uniformity requirements of lower composite products production.

Therefore, the main disadvantage of hand lay-up production fan blades is that the product quality of the worker’s operating proficiency and environmental conditions dependent on a large, low production efficiency and product quality uniformity fluctuations, product static and dynamic balance to ensure poor, high scrap rate.

Especially for high-performance complex pneumatic and sandwich structure blades, but also often need to adhere to two times processing, bonding process needs to adhere to the platform or type frame to ensure that the adhesive surface of the joint, production process is more complex and difficult.

The problems in the use of wind turbine blades produced by hand lay-up are often due to the uneven content of the rubber in the process, the poor infiltration of fiber/resin, and the incomplete curing, etc.

In addition, the hand lay-up process is often accompanied by a large number of harmful substances and solvents released, there is a certain environmental pollution problem.

Therefore, the current foreign high-quality composite fan blades are often used in RIM (polyurethane reaction injection molding).

RTM winding and Prepreg/hot pressing process manufacturing. RIM process investment is large, suitable for small and medium-sized fan blade mass Production (>50,000 film/year); The RTM process is suitable for medium mass production of small and medium-sized fan blades (5,000~30,000), and the winding and prepreg/hot pressing process is suitable for mass production of large fan blades.

The main principle of RTM process is to set up the reinforced material pre-forming body (preform) designed by the performance and structure requirements first in the cavity berth and inject the special low viscosity injection resin system into the closed die cavity by injection equipment, The mold has the periphery seal and the fastening as well as the injection and the exhaust system to ensure the resin flow smoothly side out the mold cavity all gases and thoroughly infiltrates the fiber, and the mold has the heating system to be able to carry on the heating curing and the forming composite material member.

Its main features are:

Closed-die Molding, product size and high precision, suitable for forming high-quality composite material components (the whole blade molding);

Small initial investment (compared with SMC and RIM);

Product surface finish is high;

High molding efficiency (compared with the hand lay-up process), suitable for forming about 20,000 pieces of composite material products;

Environmental pollution is small (organic volatile less than 50ppm, is the only in line with international environmental requirements of the composite molding process).

It can be seen that the RTM process belongs to the semi-mechanized composite molding process, the workers simply put the design of the dry fiber pre-forming body into the mold and die, followed by the process is entirely by the mold and injection system to complete and ensure that no resin exposure, and thus the workers ‘ technical and environmental requirements are far below the hand lay-up process and can effectively control product quality.

RTM process using a closed-die molding process, especially suitable for a single forming of the overall wind turbine blades (fiber, sandwich and joint, etc. can be molded in one cavity), without two times bonding.

Compared with the hand lay-up process, it not only saves all kinds of fixtures and equipments but also saves working time, improves production efficiency and reduces production cost.

At the same time, because of the low viscosity resin infiltration fiber and the heating curing process, the composite material quality and production efficiency are greatly improved.

RTM process production of less dependent on the technical level of workers, process quality depends only on the determination of good process parameters, product quality is easy to ensure that the product scrap rate is lower than the hand lay-up process.

The difference between the RTM process and the hand lay-up process is that the technical content of the RTM process is higher than that of hand lay-up technology.

Whether it is mold design and manufacturing, the design and placement of reinforced materials, the selection, and modification of resin types, and the determination and implementation of process parameters (such as injection pressure, temperature, resin viscosity, etc.) need to be determined by computer simulation analysis and experimental verification before product production, thus effectively guaranteeing the ⼀ consistency of quality.

This is important for the production of moving parts such as wind turbine blades.

Therefore, from the above analysis and comparison can be seen, the use of composite RTM resin transfer molding technology to replace the wind turbine blade hand lay-up manufacturing process, with high production efficiency, good product quality, strong mechanical properties.

At the same time can greatly reduce the harmful ingredients of resin to the human body and environmental damage caused by the current wind turbine blade manufacturing technology is the main direction of development. The application of this technique can basically solve the technical and quality problems existing in the manufacturing process of ⼿ paste blades and is the key technology of product renewal and market occupation.