Why carbon fiber thread counts matter

You'll often see carbon fibre fabric described as a weight, tow size and weave.  Such as 600gsm 12K Twill.

Don't be misled into the notion that tow size is the same as the thread count.and, like cotton sheets, the higher the better.  We'll get to the thread counts a bit farther on. 

We use different weights with different tow sizes and different weaves.  They do different jobs so we choose the right combination of materials for the job in hand.

Carbon fiber fabrics are made from incredibly thin carbon fiber filaments that are much finer than a human hair. 

These filaments are bundled into tows (or yarns) used for weaving the fabric.  These tows will commonly have 1K, 3K, 6K or 12K filaments.  Different weaves are created by changing the number of vertical tows (warp) that the horizontal tow (weft) cross. 

So in a plain weave the weft crosses one warp at a time whereas in a 2x2 twill the weft crosses 2 warps at a time with an offset on each line to create the diamond pattern.  Clear?  OK, I think we need pictures.

This is showing the pattern for plain weave. Obviously this would be a ridiculously narrow piece of fabric and you would need many more warp tows to make something usable but you get the picture.

This is what plain weave carbon fiber fabric looks like.

 

 

Now we come to 2x2 twill.  This is the 2x2 twill weave pattern.

 

This is what 2x2 twill carbon fiber fabric looks like.

Now the filament count together with the density of the weave (how tightly the warp and weft are bound together) is what determines the weight of the fabric.  And we all know that the whole point of carbon fiber is light weight, strength and how gorgeous it looks on finished products such as iPhone cases. 

So a 200gsm 3K 2x2 carbon fiber fabric has 3 thousand filaments per tow, has been woven with a twill pattern to a density that means it weighs 200 grams per square metre.  A 600gsm 12K Plain weave, well you can do it now.  You also know what a 400gsm 12K 2x2 carbon fiber fabric is.

Where do thread counts come in?  The thread count is a definition of how tight the weave is.  In weaving terms it is the number of ends (wefts) plus the number of picks in a square inch.  Thus a 400 thread cotton sheet has 200 horizontal threads and 200 vertical threads in each square inch so it feels very smooth and luxurious.  Carbon fiber fabrics will typically have thread counts between 8 and 20 but that doesn't mean they are not luxurious, you just wouldn't make bed sheets out of them.

Now the next obvious question is why isn't it a simple progression in filament count to weight?  Why doesn't the 400gsm have 6K tows and the 600gsm have 9K tows?  Well give me chance, I did say it was a big topic.