Wind turbine blades

Composite wind turbine blades are the key moving parts of wind power generation systems, which directly affect the performance of the entire system and have long-term weatherability and reasonable prices for use under outdoor natural environment conditions. Therefore, the level of blade design and manufacturing quality is very important, and it is considered as a representative of the key technologies and technical levels of wind power generation systems.

Traditional composite wind turbine blades are mostly manufactured using Hand Lay-up technology. The main features of the hand lay-up process are manual operation, open molding (the resin and reinforcing fibers in the molding process need to be completely exposed to the operator and the environment), low production efficiency, and the degree of resin curing (degree of chemical reaction of the resin) is often low. It is suitable for the production of composite products with smaller batch size and lower quality uniformity. Therefore, the main disadvantages of the hand lay-up process for producing fan blades are that the product quality is dependant on the worker's operating proficiency and environmental conditions, the production efficiency is low, the product quality and the product quality uniformity fluctuate, the product's dynamic and static balance is poor, and the waste product The rate is higher. In particular, high-performance complex pneumatic and sandwich structure blades often require secondary processing such as bonding. The bonding process requires the bonding of a platform or frame to ensure the adhesion of the bonding surface, and the production process is more complex. difficult. Problems in the use of wind turbine blades produced by the hand lay-up process are often due to cracks, fractures, and blade deformation caused by non-uniform glue content, poor fiber/resin infiltration, and incomplete curing during the process. In addition, the hand lay-up process is often accompanied by the release of a large amount of harmful substances and solvents, and there is a certain problem of environmental pollution. Therefore, foreign high-quality composite fan blades are often manufactured by RIM (polyamine reaction injection molding), RTM, winding and prepreg/hot press processes. The RIM process investment is relatively large, suitable for mass production of small and medium sized fan blades (>50,000 chips/year), and RTM technology is suitable for medium volume production of medium and small size fan blades (5,000 to 30,000 chips/year); Winding and prepreg/hot pressing process are suitable for mass production of large-scale fan blades.

The main principle of the RTM process is to first place a preform for reinforcements (Preform) that is designed according to the performance and structural requirements in the cavity, and inject a special low-viscosity injection resin system into the closed cavity with an injection device. The mold has a peripheral seal and The fastening and injection and exhaust systems ensure that the resin flows smoothly and discharges all the gas in the cavity and thoroughly infiltrates the fibers, and the mold has a heating system that can be heat cured to form the composite member. Its main features are:

Closed-mold molding, high product size and appearance accuracy, suitable for forming high-quality composite material monolithic components (one-piece molding of the entire blade);

Small initial investment (compared with SMC and RIM);

The surface finish of the product is high;

High molding efficiency (compared with hand lay-up process), suitable for forming about 20,000 composite products per year;

Low environmental pollution (organic volatiles less than 50ppm, is the only composite molding process that meets international environmental requirements).

It can be seen that the RTM process is a semi-mechanized composite molding process. The worker only needs to put the designed dry fiber preform into the mold and mold it, and the subsequent process is completely based on the mold and the injection system. It is ensured that there is no exposure of any resin, and therefore the technical and environmental requirements of the workers are far lower than the hand lay-up process and can effectively control the quality of the product. The RTM process uses a closed-mold molding process, which is particularly suitable for forming an integral wind turbine blade at a time (co-molding of fibers, sandwiches, and joints in a primary cavity) without the need for secondary bonding. Compared with the hand lay-up process, not only various tooling equipments for the bonding process are saved, but also the working time is saved, the production efficiency is improved, and the production cost is reduced. At the same time, due to the use of low-viscosity resin infiltrated fibers and the use of heating curing process, greatly improving the quality of composite materials and production efficiency. The RTM process produces less worker-dependent technology, the process quality only depends on the determined process parameters, the product quality is easy to guarantee, and the product waste rate is lower than the hand lay-up process.

The difference between the RTM process and the hand lay-up process is that the RTM process has a higher technical content than the hand lay-up process. Both the design and manufacture of molds, the design and placement of reinforcing materials, the selection and modification of resin types, and the determination and implementation of process parameters (such as injection pressure, temperature, and resin viscosity) need to be simulated by computers before production. Analytical and experimental verification are performed to determine the consistency of quality. This is very important for producing moving parts such as wind turbine blades.

Therefore, from the above analysis and comparison, it can be seen that the use of composite material RTM resin transfer molding technology to replace wind turbine blade paste manufacturing process, with high production efficiency, product quality, and strong mechanical properties. At the same time, it can greatly reduce the harm to the human body and the environment caused by the harmful component volatilization of the resin. It is the main development direction of the wind turbine blade manufacturing technology. The application of this technology can basically solve the technical and quality problems existing in the current hand-made paste blade manufacturing process, and it is the key technology for upgrading products and occupying the market.