Carbon Fiber

So I'm finally getting my hands on carbon fiber at work. We got a roll of material in to make some prototype parts for the project I'm working on. All of our parts for this project are carbon. This is a "plain weave" carbon that is pre-impregnated ("pre-preg") with epoxy resin. Even though I haven't done a lot of research on the actual bike carbons out there, I'm going to guess this stuff is about as strong as the "high modulus" stuff that's used in the bike industry. Usually you'll also see double digit MegaPSI numbers for young's modulus (as in "high modulus"). This stuff is no different, with some crazy tensile strengths between 110ksi (kilo PSI) to 150ksi depending on the testing condition. You'll also see stuff in the name like "8k" or "6k". That talks to the weave style (think sewing - how the fibers weave up and down to create the pattern you see). The weave affects the properties - a plain weave will give you about the same properties in all directions. The "warp" direction is the direction where there are the most fibers, giving it the most strength in that direction. The "fill" or "weft" direction is 90 degrees to the warp.

The prepreg material is created by the manufacturer dipping the dry cloth in epoxy resin. We do some "wet-layup" at work too, but it is less consistent than if you get it as a pre-preg (but

cheaper). With a prepreg there is a short shelf-life between 6 months and up to a year and a half and that has to be stored in a freezer usually. So you have a limited time that you can work with it. This stuff is thin, about 0.008" thick (cloth and resin). We're making parts with 3 or 4 layers, so the final thickness is 0.026" (with one other thin material inside). We are doing a combo of 0 degrees, then 90, then another 0 degree for some parts. Other parts get a + and - 45 degree layups. (Where the degree is pointing to the warp direction.) For the parts you see in the picture there's 3 plys, 0/90/0 layed up on a flat aluminum plate. Then there's a material that is layed over the laminate to air to flow evenly over the laminate, then a telfon sheet goes over t

hat, then a cotton-looking pad called a "breather", then a air-tight vacuum bag over all of that. The edges are sealed and a vacuum is pulled on the setup to compress the plys together. Then additional heat and pressure are applied, about 350 degrees at 45 psi in an autoclave. After that cooks, you get the laminate you see here. These basic flat panels are for some testing we're doing for flammability, and other fire related tests (cause it goes on an aircraft).

Anyway, maybe that's interesting to you, maybe not. Otherwise, I've been biking quite a bit,

mainly road biking, and working on my new Surly, slowly finding just the right parts for it on ebay. I also got a new seat, a WTB Devo for my road bike. I road it yesterday, and it was just like I remember when I test road one awhile back - just the right shape.