How Much do you Know About Composite Pultrusion?

 

About Pultrusion

 

The composite material pultrusion process is a process method for producing composite material profiles by impregnating continuous fibers or their fabrics with resin under the traction of traction equipment and curing the resin by heating the molding die.

 

Typical Process Flow of Pultrusion

 

Fiber roving arrangement–impregnation–preforming–extrusion molding and curing–traction–cutting–product

 

Composition of Pultrusion Equipment

 

1. Reinforcement Material Delivery System: such as yarn rack, felt spreading device, yarn hole, etc.

 

2. Resin Impregnation: The straight groove impregnation method is most commonly used. During the entire impregnation process, the fibers and felts should be arranged very neatly.

 

3. Preforming: The impregnated reinforcement material passes through the preforming device and is carefully transferred in a continuous manner to ensure their relative position, gradually approaching the final shape of the product, and extrude excess resin, and then enters the mold for molding and curing.

 

4. Mold: The mold is designed under the conditions determined by the system. According to the resin curing exothermic curve and the friction performance between the material and the mold, the mold is divided into three different heating zones, and its temperature is determined by the performance of the resin system. The mold is the most critical part of the pultrusion process, and the length of the typical mold ranges from 0.6 to 1.2m.

 

5. Traction Device: The traction device itself can be a crawler-type puller or two reciprocating clamping devices to ensure continuous movement.

 

6. Cutting Device: The profile is cut to the required length by an automatically synchronously moving cutting saw.

 

The process flow of pultrusion technology can be briefly divided into three steps: impregnation, molding, and curing/cooling.

 

Advantages of Pultrusion

 

Compared with other composite material production technologies, its main advantages are as follows:

 

1. High uUtilization of Raw Materials

Compared with traditional layering technology, pultrusion technology does not require cutting on sheet fiber materials or prepregs, and directly uses raw fibers and prepreg tapes for production. Except for a small part at both ends of the profile that needs to be cut off (the cutting length depends on the length of the initial traction fiber and the length of the curing mold), the production process does not produce other waste.

 

2. Can Produce Complex Structural Profiles

The process technologies suitable for profile production in the engineering field include winding technology and weaving technology. Due to the limitations of the working principle, the above two technologies can only produce single-cavity simple cross-section profiles, and it is relatively difficult to arrange longitudinal reinforcement fibers. However, pultrusion technology cannot effectively produce variable-section profiles for the time being.

 

3. High Production Efficiency:

Pultrusion technology is an automated or semi-automated assembly line production, with both “molding” and “curing” functions, which can achieve continuous production. The pultrusion speed can reach 10 meters per minute, which is unmatched by other “molding-curing” fiber composite production technologies.

 

4. Excellent Quality

Through automated equipment, the process parameters such as profile traction, longitudinal preload, winding/braiding preload, mold temperature distribution, resin injection pressure, and pultrusion speed can be accurately controlled during the production process to ensure the uniformity and controllability of the overall quality. In addition, the profile is covered by the outer mold during curing, and the overall dimensional tolerance of the profile after curing is small and the surface quality is high.

 

5. High Flexibility

By using different fiber materials and substrates (such as ultra-high modulus unidirectional fibers or multi-axial fibers, thermosetting resins or thermoplastic resins, etc.), pultrusion technology can produce products with different applicability according to different needs.

 

6. Strong Expansion/Replication

By using the same mold, process parameters, and raw materials, the production line can be quickly expanded or replicated in other regions while ensuring the same quality. High-volume, high-quality profile production can be completed without experienced layup workers or high-cost autoclave equipment.

 

Application of Pultruded Products

 

Pultruded products include various rods, flat plates, hollow tubes and profiles, and have a wide range of applications, including the following aspects:

 

1. Electrical Market

This is the earliest market for pultrusion applications. The products that have been successfully developed and applied include: cable trays, ladder racks, brackets, insulating ladders, transformer isolation rods, motor slot wedges, street lamp posts, electric railway third rail guard plates, optical fiber cable core materials, etc. There are many products worth further development in this market.

 

2. Chemical and Anti-Corrosion Market

Chemical anti-corrosion is a major user of pultrusion. Successful applications include: FRP sucker rods, cooling tower brackets, offshore oil production equipment platforms, walking grilles, stair handrails and brackets, structural brackets in various chemical corrosion environments, water treatment plant covers, etc.

 

3. Consumer Entertainment Market

This is a market with huge potential. Currently, the products developed and applied include: fishing rods, tent poles, umbrella frames, flagpoles, tool handles, lamp posts, railings, handrails, stairs, radio antennas, yacht docks, garden tools and accessories.

 

4. Construction Market

Pultrusion molding has penetrated into the market of traditional materials in the construction market, such as: doors and windows, concrete formwork, scaffolding, stair handrails, house partition wall panels, reinforcement materials, decorative materials, etc. It is worth noting that reinforcement materials and decorative materials will have a lot of room for growth.

 

5. Road Traffic Market

Successful applications include: isolation barriers on both sides of highways, road signs, pedestrian bridges, sound insulation walls, refrigerated truck components, etc.

 

6. Wind Power Market

In the field of wind power, pultrusion process is mainly used to form composite sheets of a certain thickness, and then the blade main beam is formed on the mold through vacuum infusion or prepreg process; or it is directly stacked on the platform and bundled into a prefabricated body and placed in the corresponding position of the shell, and infused with the shell as a whole. Compared with other technologies, pultruded sheet main beam laying technology has the characteristics of high efficiency, small quality fluctuation, and low cost. It can effectively improve the strength and modulus of the product and is a trend in the development of blade main beams in the future.