Carbon Fiber - Wind Power Pultruded Beam

Introduction of pultrusion production process

How to use new clean energy to replace traditional petroleum and coal resources has become a hot issue of social concern at the important historical node of not only developing the economy but also achieving the dual carbon goal. more attention.

It has been nearly a hundred years since the invention of wind power generation technology. The corresponding technology is relatively mature, but it also faces considerable challenges. Blades, the main components of wind power generation equipment, are currently mostly made of glass fiber reinforced composite materials (GFRP), which have good strength and rigidity and low production costs. With the gradual increase in the requirements for the power generation capacity of the generator set, the corresponding blade size also needs to be gradually increased, and higher technical requirements are also put forward for the performance requirements such as material strength and stiffness. For this reason, the use of carbon fiber in the manufacture of large blades has become the best choice.

Research data shows that only replacing glass fiber composite materials with carbon fiber composite materials at the girders reduces the weight of the blade by 12%, and has higher stiffness and fatigue resistance, while bringing lower transportation, installation and maintenance costs. life, the use cost of its entire life cycle is lower.

There are many forming methods of carbon fiber composite materials, and there are also many options for the production and manufacture of composite material sheets, such as prepreg process, carbon cloth infusion process and pultrusion process. Among them, the pultrusion process is a molding method for the continuous production of fixed-section fiber-reinforced composite materials. The technology started in the United States in 1948 and has been developed and promoted all over the world.

Pultruded profiles are widely used in electrical equipment, corrosion-resistant parts, construction engineering, transportation industry and military and other fields, and are currently in a stage of rapid development. Pultrusion can theoretically produce products of any length. The typical pultrusion line speed is 0.2~1.5m/min, the rapid prototyping rate can reach more than 4m/min, and multiple products can be produced at the same time, which greatly improves the The molding efficiency is suitable for mass production; in addition, the production process can be fully automated and controlled, and the cross-sectional shape of the product can be serialized and standardized, which significantly reduces the discreteness of the quality of composite products, and has stable performance; high fiber content, up to 80 %, because the fibers are fully straightened under the action of tension during molding, the fiber properties can be fully exerted, the longitudinal mechanical properties are outstanding, and the raw material utilization rate can reach more than 95%.

The steps of pultrusion are: fiber supply-fiber guiding-resin impregnation-preforming-pultrusion-drawing-cutting-pultrusion products, the heating forming part is generally divided into preheating zone, gel zone and curing zone, As shown in FIG. Existing pultrusion resins include epoxy resins, vinyl resins, and unsaturated polyester resins.

As an efficient production process for producing fixed-section composite materials, pultrusion is extremely strict in the setting and regulation of equipment and process parameters, and any small changes or nano-errors will cause product quality defects and waste. This paper briefly introduces the product structure, material selection and production process of carbon fiber wind power pultruded beams (carbon beams). Some data parameters and mix ratios are for reference only.

Product structure and material selection

The carbon beam is composed of a composite material board body, a left protective layer, an upper release cloth, a right protective layer, and a lower release cloth. The fiber of the main body of the composite material board is carbon fiber, and the fiber volume content is 50% to 80%; the reinforcing material of the protective layer on the left and right sides of the composite material board is glass fiber, and the number is at least 1 per side. 

The resin of the material is selected from high-performance epoxy resin, the curing agent is preferably a liquid acid anhydride, the accelerator is preferably a tertiary amine, and the release agent is preferably an epoxy type release agent. The mixing ratio should be epoxy resin: curing agent: accelerator: release agent = 100: (80-110): (0.5-2.0): (0.5-2.5). 

The upper and lower release cloths are made of nylon or polyester. On the one hand, the release cloth can protect the carbon beam from being damaged by scratches and scratches during product packaging and transportation. In addition, the rough surface formed by the carbon beam after removing the release cloth during use can increase the bonding strength of the product. Eliminate the grinding process of carbon beams, saving man-hours and costs.

Production process

Prepare a pultrusion die with a length of 900mm and fix it on the die holder of the pultrusion machine. Install the specified number of 48K or 24K carbon fibers on the creel, and pass through the dipping tank, the pre-forming die, the forming die in sequence, and then introduce into the pulling machine.  

The temperature of the three zones of the molding die is set and heated as required. After the temperature of the molding die is balanced, the prepared resin is added to the dipping tank, the fibers are dipped in 2 to 4 layers, and the pultrusion speed is set to 0.2 to 0.5 m/min. , After the carbon fiber is dipped, it is extruded step by step through the extrusion roller, the preforming die, etc., to fully reduce the glue content of the dipped carbon yarn before entering the mold, and the upper and lower release cloths enter the molding die together with the fiber.  

After the formed sheet is cooled down by the bellows, it enters the tractor and the winder to become the finished composite sheet.