8 Forming Methods of Carbon Fiber Composite Materials

 

Carbon fiber is generally used in the form of composite materials after being combined with a parent material (resin, etc.). Carbon fiber/composite materials have excellent performance, such as high specific strength, low specific gravity, high specific modulus, ultra-high temperature resistance, fatigue resistance and excellent corrosion resistance. They are key materials for lightweighting and are widely used in aerospace, wind turbine blades, sports and leisure, pressure vessels, automobiles and other fields.

 

Figure 2021 Global Carbon Fiber Market Demand-Application Source: Sai Ao Carbon Fiber Technology

 

Carbon fiber/composite materials can be formed by various molding methods (processing methods) according to the shape and characteristics of the final product. At the same time, in order to improve the physical properties and appearance of the final product and shorten the molding time, the molding methods of carbon fiber/composite materials are becoming more and more perfect. Next, let’s take a look at the representative molding methods.

1. Pull-out Molding

Also known as pultrusion molding. This is a continuous molding method in which carbon fiber impregnated with liquid resin is introduced and passed through a mold and heated and cured. It is suitable for molded products with a certain cross-sectional shape such as rods and tubes.

 

 

2. Filament Winding Molding

This is a molding method that winds a carbon fiber tow impregnated with liquid resin around a mandrel and then heats and solidifies it. There are two methods, one is to wind the carbon fiber while it is immersed in a resin tank (bath), and the other is to wind the tow material that has been pre-impregnated with resin. It is suitable for tubular and can-shaped moldings.

 

 

3. RTM (Resin Transfer Molding) Molding

This is a method of placing a carbon fiber preform (a product, fabric, etc. that preforms carbon fiber into a product shape) in a pair of male/female sealed molds, pressing liquid resin into it, impregnating it, and heating and curing it. The method of curing it under vacuum pressure using only the female mold is called VaRTM molding (vacuum-assisted RTM). RTM is suitable for small and medium-sized molded products, while VaRTM is suitable for large and medium-sized molded products.

 

 

4. Press Molding

This is a method of stacking thin sheets of resin impregnated with prepreg or SMC on a mold and curing them by heating while applying pressure. Mitsubishi Chemical has established a PCM (prepreg press molding) molding method based on high cycle and preforming technology, and can also be mixed with SMC materials. This molding method is suitable for mass production.

 

5. Autoclave (AC) Molding

An autoclave is simply a pressure cooker. Prepreg is stacked on the molding die, covered with an expansion film (a film used to create a vacuum state) to reduce pressure, and then heated and cured under pressure in the autoclave. This molding method is suitable for manufacturing high-quality, high-performance products, but due to the long molding cycle, the cost is relatively high.

 

 

6. Oven Molding

Like autoclave molding, prepreg is stacked on the molding die, covered with expansion film for decompression, but heated and cured under vacuum pressure. Although it is slightly inferior to autoclave molding in terms of performance, it is a molding method that can be used for larger molded products with low operating costs.

 

 

7. Winding Molding

 

This is a molding method that winds the prepreg around the mandrel (iron core), heats and cures it, and then removes the core. It is suitable for the manufacture of small and medium-sized products in the form of tubes and rolls. Mitsubishi Chemical’s golf clubs and rollers are mainly produced using the winding molding method.

 

8. Injection Molding

 

Also known as injection molding, it is a molding method that heats and melts thermoplastic resin raw materials (pellets) such as carbon fiber reinforced nylon and polycarbonate, and injects them into the mold cavity (gap). The mechanical properties will be reduced, but this is a molding method suitable for short-cycle and complex shape molding.