Does anyone know if there is a performance difference between the 4 x 4 and 2 x 2 twill and if so what they are? I have not come across any suppliers that even stock the 4 x 4 twill. None of the composites manufacturing books I have even mention 4 x 4 twill.
This guy always sells it:
http://search.ebay.com/_W0QQsassZpennon
I know nothing about its strengths/weakness’. Pagani uses it. Must be decent.
Sure is pretty…but never working with it leaves me opinionless.
I wonder how well the raw fabric would drape…and as I recall, Ferrari also uses/used it in prepreg form on the Enzo…
I use 4 x 4 quite a lot, it does drape well and hold the weave pattern better being tighter but does need extra care making sure it is in contact with the mold surface.
Baz
exactly. It is one of my favorite fabrics! I am making my hood for my M3 with it. I will post pics when I get it done. I don’t know the strength differences. I did email pagani or i guess his sales office and asked. So we will know soon
I’m quite sure their lay-up process is proprietary, but I wonder if the top layer is 4x4 and the rest of the layers are 2x2, unidirectional, or something else. The biggest beauty of these high performance fabrics is being able to get the same or higher performance level than a metal but at a much lower weight. Seems that there could be more money and weight in some products than are necessary by not know how to get the most with less. Darn engineering stuff 
4x4 twill is generally used as a surface ply as it is a much tighter weave than 2x2.
In doing wet layup it can trap air at the surface, if you use more than 1 ply. It does
drape well but not as well as 2x2. It is normally around 285 GSM with 3k fiber where
2x2 is around 200 GSM. 4x4 has a cured ply thickness around .011" compared to .008"
for 2x2. As far as performance goes it is slightly stiffer do to there being less crimp and
it being more dense of a weave.
When used in chassis construction it is used for a surface ply and usually backed up
uni. It is much more popular in Europe than the US. That is why you see it used on
so many race cars. In the US twills are generally considered tooling fabrics and 5 HS
and 8 HS are prefered for structural composites.
Hope this helps
Oh ya it is more pricey
Cheers
Jim
I have 4x4 in stock, but to tell you the through if you want to work in a surface with a lot of curves likes bikes parts, is not so co-operative.
Thanks Jim, that’s good info. The 4x4 definitely seems to have the best aesthetic qualities. I guess that’s another great thing about these products. That you can put the best looking on the outside and lay up all the strong stuff over it.
having a 4x4 is more similar to a satin weave. The benefit lies in the uninterrupted fiber. Having fibers weave up and down weakens the fiber by the fact of an incorporated radius. In tension there is a stress concentration and in compression there is an influenced bucking.
I have had a textiles engineer spit ball a figure of standard weave being 70 % as effective as unidirectional material in the specific direction. As you go more and more towards uni, you are increasing the strength in that direction, but at 70% baseline, the difference is marginal and the lay ease or visual effects are probably more important. Its up to you