Carbon fiber and Fiberglass are two popular materials for quadcopter frames. The choice between carbon fiber and fiberglass depends on many factors, in this article we will look into some of the most important aspects and differences between these materials
Carbon fiber is lighter than fiberglass, it’s 70% lighter than steel, 40% lighter than Aluminum. The nature of carbon fiber is low in weight, rigid, and strong. This is why most weight-critical performance products use carbon fiber, and it’s a far more popular choice of material for mini quad frames.
Strength vs Rigidity
Rigidity is also known as stiffness. Carbon fiber and fiberglass are both very strong, but Carbon fiber is more rigid. Carbon fiber is about 3 times stiffer than steel and aluminum for a given weight.
In applications where a small amount of flexibility is allowed, carbon fiber is a top choice. Fiberglass is better suited to extreme flex patterns, while carbon fiber has a relatively small flex window.
The shape of Carbon fiber doesn’t deteriorate over time. That means the shape of carbon fibre doesn’t change when consistent and constant force is applied on it.
Fibreglass however being more flexible, it means that glass-fiber typically has a higher ultimate breaking point than a similarly shaped carbon fiber product, therefore having higher strength-to-weight ratio. In general it is a “tougher” material. The incredible rigidity of carbon makes it less capable of enduring certain abuses than fiberglass. I guess therefore you could say CF “more brittle”
Thermal and Electrical Characteristics
As opposed to most other materials, carbon fiber has a negative coefficient of thermal expansion which means they don’t expand or shrink as much as fibreglass when the temperature changes. This is a desirable quality for applications that have to operate in a wide range of temperatures .
Fiberglass composites are insulators, which means they do not respond to an electric field and resist the flow of electric charge. Fiberglass composites are very radiolucent, which means they allow radiation to pass through it freely. This makes fiberglass rods a useful material for antennas. CF is conductive and it’s a problem for mini quad frames.
Fiberglass is more cost effective. Long strands of carbon fibers are very difficult and expensive to manufacture, while fiberglass processes much easier. As a result, fiberglass is considerably less expensive than carbon fiber. Fiberglass composites are less expensive than carbon composites in most cases.
More on Carbon Fiber Specification
These numbers indicate how many carbon strands per tow are in the weave. Lower the number “K” in carbon sheet the thicker and stronger the weave. To simplify it, 3K is stronger than 6K, 1K is stronger than 3K etc. However, 3K is pretty much the standard weave people use for general applications so if you pick up some random carbon it will most likely be 3K.
Twill Carbon fiber?
Some argue mini quad frame parts should be cut in twill pattern (diagonal shaped pattern), and that could maximize the strength. While others argue it just looks different but still provide the same strength properties. This remains a myth until someone can provide some scientific proof.