What's Carbon Fiber?
Carbon fiber (also known as carbon fibre) is one of the strongest and most lightweight materials available on the market today. Five times stronger than steel and one third its weight, carbon fiber composites are often used in aerospace and aviation, robotics, racing, and a wide variety of industrial applications.
Carbon Fiber Fabric
Carbon fiber starts as very, very thin strands of fiber that are finer than a human hair. These strands are twisted together like yarn (called a tow) and woven into carbon fiber fabric which typically comes in 3k, 6k and 12k weights. A 3k fabric has 3,000 strands of carbon in each tow while a heavier weight 6k fabric has 6,000 strands per tow.
Carbon fiber fabric comes in a variety of weaves that have different strength properties. The most common are plain weave, harness satin weave, twill weave and unidirectional.
Weave is critical for two reasons – appearance and functionality. Each weave looks very different and sometimes people prefer the look of a certain weave for a specific application. Also, weave impacts product strength. A unidirectional weave creates a carbon fiber sheet that’s very strong in the direction of the fibers, but weak in the opposite direction. Plain and twill weaves, on the other hand, have more uniform strength since they’re strongest at the points where the fibers cross in either direction.
Carbon Fiber Composites
To make a carbon fiber sheet (also known as a composite), carbon fiber fabric is saturated or infused with epoxy resins and heated at high temperatures. Shaped pieces are made by layering several pieces of fabric over a mold, saturating them with resin and heating it until the resin has infused through all layers.
The key to carbon fiber's properties is its unique microscopic crystalline structure. It is composed mostly of carbon atoms that are bound together in microscopic crystals which are linearly aligned and parallel to the long axis of the fibers. When carbon fiber is produced, thousands of thin strands of carbon are twisted together to form a yarn. This yarn is then woven into a flexible fabric that can be molded into many different shapes. To give you an idea of just how lean carbon fiber is, a single strand has a diameter of 0.005-0.010 mm, less than a human hair.
Advantages of Carbon Fiber
Carbon fiber composites stand out from the crowd for several reasons. Here are a few:
- Lightweight – carbon fiber is a low density material with a very high strength to weight ratio
- High tensile strength – one of the strongest of all commercial reinforcing fibers when it comes to tension, carbon fiber is very difficult to stretch or bend
- Low thermal expansion – carbon fiber will expand or contract much less in hot or cold conditions than materials like steel and aluminum
- Exceptional durability – carbon fiber has superior fatigue properties compared to metal, meaning components made of carbon fiber won’t wear out as quickly under the stress of constant use
- Corrosion-resistance – when made with the appropriate resins, carbon fiber is one of the most corrosion-resistant materials available
- Radiolucence – carbon fiber is transparent to radiation and invisible in x-rays, making it valuable for usage in medical equipment and facilities
- Electrical conductivity – carbon fiber composites are an excellent conductor of electricity
- Ultra-violet resistant – carbon fiber can be UV resistant with use of the proper resins
- Carbon fiber will break or shatter when it’s compressed, pushed beyond its strength capabilities or exposed to high impact. It will crack if hit by a hammer. Machining and holes can also create weak areas that may increase its likelihood of breaking.
- Relative cost – carbon fiber is a high-quality material with a price to match. While prices have dropped significantly in the past five years, demand has not increased enough to increase the supply substantially. As a result, prices will likely remain the same for the near future.