A Brief Overview of Eight Common High-Performance Carbon Fiber Molding and Processing Methods

Typically, carbon fiber is rarely used alone; it is generally combined with resins or other matrices to form composite materials. Depending on the final product's shape and characteristics, various molding and processing methods are employed.

Additionally, to enhance physical performance, improve structural appearance, and reduce molding time, carbon fiber composite molding techniques are continuously being refined. This article introduces eight representative carbon fiber molding methods.

01. Pultrusion Molding

This continuous molding method involves pulling carbon fibers impregnated with liquid resin through a die, where they undergo thermosetting. It is suitable for producing rod-shaped, tubular, and other products with a specific cross-sectional shape.

Figure 1: Pultrusion

02. Filament-Winding Molding

In this method, carbon fiber tows impregnated with liquid resin are wound onto a mandrel and then thermoset. There are two versions: (i) winding while impregnating the carbon fibers in a resin bath, or (ii) winding pre-impregnated carbon fiber tow materials. It is used for tubular and tank-shaped products.

Figure 2:Filament-winding Molding

03. Resin Transfer Molding (RTM)

In this method, a carbon fiber preform (pre-shaped carbon fiber product or fabric) is placed into a sealed mold with both male and female parts. Liquid resin is then injected, impregnated, and thermoset. When only a female mold is used with vacuum pressure, the process is called Vacuum-Assisted RTM (VaRTM). RTM is suitable for small to medium-sized products, while VaRTM is better for medium to large-sized items.

Figure 3:Resin Transfer Molding

04. Press Molding

In this method, resin-impregnated sheet materials like prepreg or SMC are layered on a mold and thermoset under applied pressure. Mitsubishi Chemical has developed a prepreg compression molding (PCM) technique based on high-cycle and preforming technologies, which can also be mixed with SMC materials. This method is ideal for mass production.

Figure 4:Press Molding

05. Autoclave Molding

An autoclave is essentially a high-pressure vessel. This method involves stacking prepreg on a mold, covering it with a vacuum bag, and then thermosetting under pressure and heat in an autoclave. It is used for high-quality, high-performance products, but due to its long cycle time, it is costly.

06. Oven Molding

Similar to autoclave molding, this method involves stacking prepreg on a mold, covering it with a vacuum bag, and thermosetting under vacuum. Although it has slightly lower performance and quality than autoclave molding, it is cost-effective and can be used for relatively large products.

07. Sheet-Wrap Molding

This method involves wrapping prepreg around a mandrel, followed by thermosetting and removal of the mandrel. It is suitable for producing medium to small tubular and roll-shaped products. Items like golf club shafts and other types of rods are often made using this method, and it can sometimes be used for tapered products.

08. Injection Molding

Also known as injection molding, this method involves heating and melting carbon fiber-reinforced thermoplastic resin (e.g., nylon, polycarbonate) pellets and injecting them into mold cavities. Although the mechanical properties are not outstanding, this method is suitable for forming complex shapes with short cycle times.