From wiki, "composites are formed by combining materials together to form an overall structure with properties that differ from the sum of the individual components." This week we were using fiber layers to make composite. I used glass fiber for the structure of my robot before, so I understand that it's actually hard to make a complicated part with fiber composite, because of that, I decided to make my mode as simple as I can. I made a STAR! If it succeed, it would become a star bowl :P
Making the Mold
This part is just the same as what we did before, making a CAD model, using MasterCAM to make the G code for machine, and using CNC milling machine to mill the mode. This week we used blue foam for molding, the result of my mold was actually pretty good.
(I sanded it afterward but I forgot to take a picture of the end result... but it's pretty smooth.)
1. Cover the mold with aluminum foil
To do the composite, since we were using blue foam, what we need first is to cover our molds with aluminum foil. To make it stick, we used sprayable glue. One thing that I did wrong was to spray the glue on the blue foam instead of on the alumimum foil, and my mold was melted a little bit by the glue.
Spray mold releasing after covering the mold.
2. Cut the fibers
Cut the fibers to the size of the mode. For safety resaon, we need to wear gloves while doing composites, so I had no chance to take the photos on my process. From now on, I will use the photos I took during TA's demo.
3. Weight the fibers and calculate how much epoxy A & B we should use
So basically, after measuring the weight, you need to first times 3 of the weight you got, and times 69% to get the weight of epoxy A, times 31% to get the weight of epoxy B.
4. Mix epoxy A & B well and use it connect each layer
5. Water press / Vacuum
Before water press / vacuum, remember to place a plastic cover on top of the fiber which has little holes to let the resin out and you cover it with cotton to soak the resin.
Calvin was demoing how to use water pressure for it.
My part inside the vacuum bag
It came out not so pretty :(