You might have heard about the 3K and 12K when you purchase carbon fiber products, yes, actually these 2 grades are the most common option, additionally, there’re many of grades, it might be make you confuse, let’s put it in plain English.
What is "K"?
As we all know the carbon fiber is very thin, usually 5-8 micrometers diameter each, they have to be woven into fabric to be usable, that means packed thousands of individual filaments into a small space, we call it tow or bundle. The “K” means the number of filaments in each tow or a bundle of fibers in the woven fabric. For example:
1K: 1,000 filaments each tow
2K: 2,000 filaments each tow
3K: 3,000 filaments each tow (Most Common)
6K: 6,000 filaments each tow
12K: 12,000 filaments each tow
UD (Unidirectional)
And so forth
In simple terms, the “K” number is bigger, the tows are wider. For example, the width of 1K tows is 1mm, the tow width of 3K fabric is 3mm, and so on.
Is K Number Affect Strength?
Sometimes people thinks the tows are larger, the strength are higher, actually they have the same tensile strength, i.e.: The tensile strength of T300 is around 3.5Mpa. Just the reverse, the manufacturing technique of 1K carbon fiber is more complex than 3K carbon fiber. What really affects the strength of carbon fiber is the “T”, like T300, T700, T800 etc, know more about the strength grade, please check out my previous posts <What is T300, T700, T800 of Carbon Fiber Products>.
Features & Applications
3K Carbon Fiber
3K carbon fiber is the most common and the most economical option on the market, they have a very classic appearance, and also very light, and have enough strength, most of the carbon fiber products you see in the market are made of 3K tows carbon fiber. From sports gear to industrial equipment, and even in aerospace and military applications, you can find it everywhere.
12K Carbon Fiber
12K carbon fiber have more attractive and more impactful appearance due to its wider weave pattern, but it’s heavier and less flexible than 3K carbon fiber. Its distinctive weave also enhances the aesthetic appeal of products, especially in industries where both appearance and durability are important.
UD (Unidirectional) Carbon Fiber
UD carbon fiber tows are aligned in a single direction, so it has excellent strength along that specific axis. Unlike woven fibers that distribute strength evenly across the different directions, UD carbon fiber focuses its strength in one specific direction, it specialist use for some field that require maximum strength in one direction, such as Fishing rods, Bicycle frame & Rim, Pushing pole, etc.
