How Forged Carbon Is Made

What forged carbon is

Forged carbon, often called forged composite, is a carbon fiber material made from short, randomly oriented fibers mixed with resin and pressed in a mold. Instead of the regular weave pattern seen in traditional carbon fiber, it has a marbled, swirled look that differs from part to part. It is used in automotive trim, watches, wheels, sporting goods and consumer products.

How forged carbon is made

The details vary by manufacturer, but the general process is as follows.

1. Chop the fiber. Carbon fiber tow is cut into short pieces, typically well under an inch long (check the supplier for exact lengths).
2. Combine with resin. The chopped fibers are mixed with a resin, commonly an epoxy (see epoxy durability for how cured epoxy ages), or supplied as a ready-made pre-impregnated material.
3. Load the mold. A measured amount of material is placed in a metal mold. Weighing the charge matters because it determines how fully the cavity fills.
4. Compression mold. The mold closes and applies pressure, which forces the material into every corner and squeezes out excess resin. This is similar in principle to sheet molding compound (SMC) processing.
5. Cure. Heat, and in some systems an oven or autoclave, hardens the resin. Some hobby kits are designed to cure at room temperature under clamping pressure.
6. Finish. The part is removed, trimmed, sanded and often clear coated and polished to bring out the marbled pattern.

Three common material routes

Suppliers describe a few ways to arrive at forged carbon:

• Pre-preg chopped material. Fibers are already combined with resin in a sheet or bulk form, which is easier to handle and load.
• Dry chopped fibers or fabric pieces with added resin. Resin is added in the mold or by infusion.
• Hand-placed chopped fibers. Common in small-scale or hobby work, with more variation in results.

Is forged carbon actually forged?

Not in the metalworking sense. Metal forging shapes solid metal by hammering or pressing it. Forged carbon is in practice compression molding of fiber and resin, and “forged” is largely a marketing and industry term borrowed for the look and the pressure-based process. The material is still a real carbon fiber composite.

Forged carbon versus woven carbon fiber

• Appearance. Woven carbon has a repeating pattern, while forged carbon is random and marbled.
• Strength. Woven laminates with continuous fibers aligned to the load can be stronger in a given direction. Forged carbon has short fibers in random orientation, so its properties are more similar in all directions (isotropic). Which is “better” depends on the application.
• Shapes. Forged carbon flows into complex 3D shapes more readily than woven fabric, which can wrinkle on tight curves.
• Production. Compression molding can be quicker per part for repeatable shapes once the tool exists.

Disadvantages

• Tooling is required, and molds capable of high pressure are not cheap.
• Short random fibers typically do not match the directional strength of continuous-fiber layups.
• Appearance varies from part to part, which some buyers like and others do not.
• Surface finish, resin quality and void content can vary between manufacturers.
• Repairs are harder than on many other materials.

Why it costs what it costs

Forged carbon is generally priced as a premium material. Carbon fiber itself is costly, tooling and presses add expense, and finishing for a glossy surface takes labor. Cost depends heavily on part size, volume and quality, so quotes vary widely.

Making it at home

Forged carbon kits and DIY approaches exist, and makers sometimes use 3D-printed molds for small experiments. Be cautious: printed plastic molds may not withstand much pressure or heat, and results can be inconsistent. Resin, fine carbon dust and sanding residue can irritate skin and lungs, so work with gloves, eye protection, good ventilation and a suitable respirator, and follow the safety data sheets for your materials.

Related

Forged carbon relies on the same idea as other mold-based processes: material, heat, pressure and a well-made tool. For a related plastics process, see injection molding tips and tricks.