Introduction to the Pultrusion Process of Carbon Fiber Wind Power Beam

 

Carbon Fiber Wind Power Pultruded Beam

 

Pultrusion Molding Production Process Introduction

 

At a major historical juncture where we need to develop the economy and achieve dual carbon goals, how to use new clean energy to replace traditional oil and coal resources has become a hot issue of social concern, and wind power, as a type of clean energy, has received more and more attention.

 

 

Wind power generation technology has been around for nearly a hundred years since its invention. The corresponding technology has become relatively mature, but it also faces considerable challenges. The main component of wind power generation equipment, the blade, is currently mostly made of glass fiber reinforced composite material (GFRP), which has good strength and rigidity and low production cost. 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 for material strength and stiffness and other performance requirements have also been put forward. Due to the limitations of the performance of glass fiber itself, it is difficult to do this. Therefore, the use of carbon fiber for large blade manufacturing has become the only choice.

 

Research data shows that only replacing glass fiber composite materials with carbon fiber composite materials at the beam can reduce the weight of the blade by 12%, and have higher rigidity and fatigue resistance, while bringing lower transportation and installation costs and maintenance costs, extending the service life of the wind turbine, and its full life cycle cost is lower.

 

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

 

Pultruded profiles are widely used in electrical equipment, corrosion-resistant components, construction engineering, transportation industry, 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, and the rapid molding rate can reach more than 4m/min. It can also produce multiple products at the same time, which greatly improves the molding efficiency and is suitable for mass production. In addition, the production process can be fully automated, and the cross-sectional shape of the products can be serialized and standardized, which significantly reduces the discreteness of the quality of composite products and has stable performance. The fiber content is high, up to 80%. Since the fibers are fully straightened under tension during molding, the fiber performance 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 guidance-resin impregnation-preforming-pultrusion-traction-cutting-pultrusion products. The heating and forming part is generally divided into preheating zone, gel zone and curing zone, as shown in the figure above. Existing pultrusion resins include epoxy resins, vinyl resins and unsaturated polyester resins.

 

FXR/FXC-550 produced by Shanghai Fuchen is an epoxy resin for pultrusion process, which is often used in composite material pultrusion process. FXR/FXC-550 has high environmental safety characteristics (solvent-free curing system), high mechanical properties, high temperature resistance, long application period and excellent pultrusion speed; according to the shape of the product, it can reach 100-500mm/min; it has good wettability to glass fiber and carbon fiber, good storage stability, and storage time is up to 1 year.

 

 

 

As a production process for efficiently producing fixed-section composite materials, pultrusion is extremely strict in the setting and regulation of equipment and process parameters. Any small change or slight mistake will cause product quality defects and waste. This article briefly introduces the product structure, material selection and production process of carbon fiber wind power pultruded beam (carbon beam). Some of the data parameters and mix ratios are for reference only.

 

Product Structure and Material Selection

The carbon beam consists of a composite material plate body, a left protective layer, an upper demoulding cloth, a right protective layer, a lower demoulding cloth, etc. The fiber of the composite material plate body is carbon fiber, and the fiber volume content is 50% to 80%; the reinforcing material of the left and right protective layers of the composite material plate is glass fiber, and the number is at least 1 on each side.

 

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

 

The upper and lower mold release cloths are made of nylon or polyester. On the one hand, the mold release cloth can protect the carbon beam from being damaged by scratches and scrapes during product packaging and transportation. On the other hand, the rough surface of the carbon beam formed after the mold release cloth is removed during use can increase the product bonding strength, eliminate the grinding process of the carbon beam, and save time and cost.

 

Figure 2 Carbon beam structure diagram

 

Production Process Flow

 

The schematic diagram of the pultrusion process flow is as follows:

 

 

Figure 3 Schematic Diagram of Pultrusion Production Process

 

(1-creel, 2-yarn collecting plate, 3-layered yarn plate, 4-impregnation tank, 5-mixing, 6-rubber extrusion roller, 7-mold stripping cloth, 8-preforming mold, 9-forming mold, 10-traction device, 11-cutting device, 12-winding device)

 

Prepare a pultrusion molding mold with a length of 900mm and fix it on the pultrusion machine mold fixing frame. Install the specified number of 48K or 24K carbon fibers on the creel, and pass through the impregnation tank, preforming mold, forming mold in turn, and introduce it into the traction machine.

 

The temperature of the three zones of the forming mold is set and heated as required. After the temperature of the forming mold is balanced, the prepared resin is added to the dipping tank, and the fiber is dipped in 2 to 4 layers. The pultrusion speed is set to 0.2 to 0.5 m/min. After the carbon fiber is dipped in glue, it is squeezed through four stages such as the squeeze roller and the preforming mold to fully reduce the glue content of the dipped carbon yarn before entering the mold, and enters the forming mold with the upper and lower demolding cloths.

 

After the formed sheet is cooled by the bellows, it enters the traction machine and the winder to become a finished composite sheet.