Imagine unwrapping a much-anticipated Christmas present this year. You know what it is – a carbon fiber phone case – because your significant other told you about it months ago. Yet you find yourself let down at the big reveal. Why? Because your carbon fiber phone case feels like plastic.
You expected something more. Sure, the phone case really looks cool. It also feels pretty solid. But it still feels like plastic in your hands. Well, there is a reason for that. What you are holding in your hand is known as a carbon fiber reinforced plastic (CFRP). It might sometimes be referred to as a carbon fiber reinforced polymer – it is the same thing, just a more scientific name.
The Carbon Fiber Misnomer
Rock West Composites is a Salt Lake City company that specializes in composite materials. If you were to purchase the raw materials for making your own phone case, Rock West would sell you a woven carbon fiber fabric and a container of epoxy resin. You would combine the two materials to make a CFRP.
The term ‘carbon fiber’ is actually a misnomer when applied to finished parts. Again, your phone case is not just carbon fiber. It is carbon fiber and resin combined to create a plastic. We call it carbon fiber because the term is easier to say than ‘carbon fiber reinforced plastic’. It also sounds more exciting and, from a manufacturer’s perspective, more marketable.
That does not change the fact that your phone case is made of plastic. It is just a plastic reinforced with carbon fiber fabric. The amazing thing is that the fabric is what makes the finished product so strong.
High Tensile Strength
CFRPs are extremely strong compared to steel and aluminum. They exhibit a high tensile strength, which is measured as the amount of force a material is able to withstand before failing. Carbon fiber’s high tensile strength is the result of the fibers themselves.
In any carbon fiber material, its strength runs in the same direction as its fibers. So if all the fibers run in a lateral direction, the finished part’s strength would be laterally. But what happens if you weave a carbon fiber fabric instead? Woven fabrics align threads in perpendicular directions. Moreover, the threads cross over and under one another. This makes a carbon fiber fabric extremely strong.
The multi-directional strength is that which makes finished carbon fiber parts stronger than aluminum and steel. But because the finished parts are actually plastics, they are much lighter. This is the inherent beauty of CFRPs for manufacturing.
Too Weak On Its Own
With a thorough explanation of carbon fiber out of the way, let’s get back to plastics. There is no non-reinforced plastic we know of strong enough to be used to make things like airplane fuselage panels and wings. Plastics are too weak on their own.
You know from your own experience how easy it is to break plastic pieces. For example, imagine the same plastic in your TV remote being chosen to make airplane wings. Would you fly on a 747 with wings made of that plastic? Of course not.
We make plastics stronger by reinforcing them. And one of the best ways to do that is with carbon fiber fabric or tow. Carbon fiber does for epoxy resin what rebar does for concrete. It reinforces to give the finished part greater tensile strength and more rigidity.
Some carbon fiber parts feel like plastic because that is exactly what they are. They are plastics reinforced with carbon fiber to make them stronger. It is no more complicated than that.
