How thin are carbon fibers? 🧐 The answer is pretty simple, carbon fibers have a diameter between 5 and 10 micrometers. But that is kind of hard to visualize, right? So let's compare them to something all humans have (some more than others😂), hair! Luckily, we have a very nice picture that makes it very easy to draw a comparison. Crazy to realize how carbon fibers are thin, right? In case you are wondering, a human hair is about 40-120 microns in diameter. 🕵🏻‍♂️ But if you think that human hair is a very weak material, you are wrong! It consists almost entirely of a protein called Keratin which has about half of the ultimate tensile strength of steel (200 MPa). If you are tensile testing a single strand, you will only measure about 100 grams of force. 🤯 Going back to carbon fibers, it is crucial for them to have small diameters, because it allows greater graphite content. This way, the probability of having a concentration of defects in the 3D structure is considerably reduced. The mechanical properties of these fibers are inversely proportional to their filament diameter. 😃