I am looking for dry carbon fiber weave that is basically unidirectional, with some reinforcement in the weft. I found this picture at a carbon fiber supply shop. It is described as 3K 4 harness satin. I think this is what I am looking for. Can someone comment on the picture and my observations?
Can’t see the picture. A 4 harness satin is NOT a unidirectional fabric. It is often balanced.
http://imageshack.us/f/694/sqd4.jpg/
I had some trouble with the photo. Here it is at imageshack.
It looks like it has substantially more carbon fiber in one direction, but I have virtually no experience with carbon fiber, and can’t trust my observations. Is this a balanced 4HS, and if so, what exactly does balanced mean? I would think it means the about the same number of fibers in each direction, but again this appears to have many more fibers running in one direction.
The harness satin weaves may look like a majority of uni in the warp direction on one side, but when you flip it to the other side, it essentially has the same amount of fiber in the weft (fill) direction.
What is the purpose of the reinforcement in the weft? Do you need it to hold the uni’s together or is it actually structural? I ask because they make uni fabrics that are loosely held together. I suppose you could request a custom weave with a fewer or lower tow weft fibers, but probably way too expensive.
Yes, I’d say I need it to hold the unidirectional fibers together rather than structural. Again, I must confess I am completely new to carbon fiber, but my intuition tells me that there should be some stock weave that is ideal for a very thin single layer composite tube .75" to 1" in diameter, where the majority of fibers are unidirectional.
I’ve had to make lots of very lightweight but stiff carbon tubes in that diameter. You will probably need to use several different fiber formats to achieve your goals. Using pure UD along with some other woven fabrics works well. Some of the tubes that I produced were made with high modulus carbon UD formats and 1K carbon woven fabric. I would put the woven fabric on 0/90 to the length of the tube to maximize the stiffness and hoop strength/stiffness. Fabric on 0/90 is better in respect to the hoop strength and stiffness than fabric on +/-45. The also allows half the fibers of the woven fabric to be directly aligned for the bending loads of the tube. I also used glass style 2113 along with UD carbon for some really light weight stuff. 2113 is a very unbalanced glass fabric. I would but the warp yarns on 90 and the lighter weft yarns on 0. This would maximize the hoop strength. These parts were .75" in diameter, 30 inches longs, and weighed around 13 grams.
Really lightweight components can be challenging because of the access to lightweight materials. One has to be creative. There are quite a few people who are using combinations of UD carbon and spread tow wovens for light weight tubes.
Thanks for the informative post. From it (and others) I am beginning to form the idea of what I have to do to make the tube I want. Using a lightweight weave in the 0 90 orientation along with UD is interesting.