"design and make a 3D mold (~ft2), and produce a fiber composite part in it"
Just like the molding and casting assignment, this is an assignment where you go from a 3D design to a mold to a physical object. Composites are interesting, because they allow for making thin-walled and strong objects, like custom casings for digital products and interactive installations.
My idea for the composites assignment is to make a chair in the shape of a leaf that bends when you sit in it and that acts as a decorative piece when you are not. The challenge is to make a composite that can bend and is strong at the same time.
This is the design of the 'leaf' in Rhinoceros:
The actual design would be about 90 cm high, but I want to try out making the composite and test the area where the shape would bend first.
So I made a scaled down mold out of foam. After milling, there was an error in the mold. I used a piece of foam that already had some material milled out from it and I tried to adjust for that with the Shopbot, but still a little dent was left in the mold. I repaired this was some clay:
Then, I cut out linnen using a paper template to fit in the mold.
With the linnen pieces cut out, I did a dry test in the vacuum bag, to see how the matial would behave. I noticed that the linnen produced folds where it was forced over mold. I marked the places where that happened with a marker and cuts slits in the linnen to allow it more room to move.
Then it was time to prepare the vaccum bag. I placed baking paper on the mold and between the linnen and the vacuum bag. The baking paper makes it easy to remove the model from the mold. A good tip from Mickael was to apply Vaseline to the baking paper too.
Mixing the components for the resin, it is important to read the labels. There were two bottles, A and B that had to be mixed in a 2:1 volume ratio. After mixing there is 25 minutes to apply the resin to the linnen an place the model in the vacuum bag.
To make sure the air could get out well, I made a small breathing vent out of soft material between the mold and the valve.
At this point, I placed the model in the vacuum bag and had to leave it overnight because the Fablab was closing for the day :).
The final result:
