Fabricating parts with carbon fiber is catching on in all sorts of industries. Parts formerly made of metal are enjoying new life and better performance after being made with carbon fiber. Nonetheless, carbon fiber is an entirely different material with unique properties that metals do not possess. Replacing metal with carbon fiber involves an entirely new mindset.
Fabrics and Resins
Creating carbon fiber parts via a manual layup process involves combining fabrics and resins. Knowing this is key to understanding why carbon fiber fabrication is so different. Like any other fabric, a carbon fiber fabric is woven from individual carbon threads. The weaving process aligns the threads in a specific direction.
Laying down multiple layers of fabric with fibers all running in the same direction creates a quasi-isotropic layup. The finished piece is known as a ‘black metal’ part. It is so named because it looks like it was made with metal. You can barely see the fabric because all of the fibers are aligned in the same direction.
Black metal fabrication works just fine if the desired part needs to have uniform stiffness and thickness. But if more stiffness is required at certain locations, quasi-isotropic layups are not practical.
Adding Strength Where Necessary
One of the difficulties of fabricating with metals is that you are stuck with uniform thickness and stiffness. It is impossible to strengthen key areas of a given part simply by realigning the metal. All you can do is add more metal where more strength is needed. That adds weight and bulk.
Approaching carbon fiber fabrication in the same way fails to take advantage of some of the best properties of the composite material. As such, black metal fabricating is rarely applied. Instead, fabricators look to add strength where it is necessary by changing how fibers are aligned.
According to Rock West Composites, fabricators can align fibers perpendicularly with each alternating layer of fabric. This gives additional strength at those perpendicular joints. But that is not even the half of it. They can slightly alter the angle of intersection so that it differs with every layer. This creates more strength with each slightly offset angle.
Extra Thickness Not Required
An obvious advantage of this property of carbon fiber is that additional thickness is not required to achieve extra strength. You can create a part with uniform thickness that is still stronger in some locations than others. As a result, you do not need to increase the volume or weight in order to increase strength.
Being able to increase the strength without also increasing weight or volume is key to creating some very important parts. Consider the carbon fiber bike frame as an example. It would not be nearly as strong if fabricators employed a black metal approach to creating the tubes that make up the frame. Just by realigning fiber direction at key points, they can make a carbon fiber bike frame extremely strong.
Even with Complex Geometry
Most exciting of all is the realization that fabricating with carbon fiber is possible even with complex geometry. If fabricators can break out of the black metal way of thinking, they can use carbon fiber to create rather complex parts that would be impossible with metal. It is simply a matter of creating the right tools and choosing the best fabrication method.
Metals and composites all have their places in the fabrication world. When companies switch from metal to composites however, they also have to change their thinking. Composites require an entirely different mindset in order to take advantage of all they have to offer.