Since I’m bored at work due to Newport being gits…and my vacuum pump ready to commit suicide, i’ll pop a few answers.
- whats does 2 x 2 twill mean?
2 over 2 under. It is the style of the fabric weave. Plain Weave is one over, one under, like a normal…well…plain weave pattern. There are many many more. Harness, Satin, Crowfoot. it all depends on how each tow (strand of Carbon fibers) is weaved.
- How many layers of carbon fiber + epoxy will it take to make a 40cm x 20 cm, 4mm thick part?
Well, for thickness. Um. I dunno. For a 5oz plain weave pre-preg (meaning the epoxy is already on the fabric, ready to lay up and cook) is is about 10 plys.
- I want to make a male mold, for a molded RC car carbon fiber/ kevlar chassis.
My mold is going to be more complex, with corners in the design, but can i use the same theory? Whats that plastic sheet called?
Like, screwing a few 2x4’s on the sides, etc? It is possible yes. Just remember, what you put on, has to come off when it’s hard, so you can’t wrap a 2x4 completely, and expect to pull it right off. We used a truck to do that the other day, to pull a split 2x4 off a tube. (don’t get me started on what became of THAT project…)
The plastic sheet can be many kinds. Vacuum bagging I think is either nylon or some sort of poly. I hear trashbags work.
That picture I’m sure has a bag wrapped around the wood, and then another one stretched on top, to compact all the layers of carbon fiber. One can also put it in a sealed bag, and vacuum out the air with a good pump.
Also, can i sandwich kevlar fabric between carbon fiber, during lay-up?
Yup. as far as I know. I think kevlar is hard to wet-out with epoxy, or might not stick well…someone else can answer this.
Finally, if I don’t use plastic sheet on the mold, what can i use to coat my mold?
You can seal the wood with a sealer. Sand down until perfectly smooth and seal. I’m sure you can coat it with a polyurethane coat to make it shiny.
Then, you must either: wax the mold a few times, or use some sort of mold release agent. Frekote, or PVA. There are many kinds of perm, and semi-perm mold releases.