this week we got to choose out of a delicious menu of options from the TAs and staff members at mit. there were so many options that i wanted to go with, but i went with composite casting offered and taught by alfonso parra rubio.

composite casting is a processing of layering fabrics with resin over a (typically) smooth surface to create a super strong and resilient cast. it's used in industry (think airplane bodies) and is the method for wrapping carbon fiber.

i started out the week by not really understanding the process so i created this super intricate model in cad which i wanted to mold and cast (i'll cast it next week using 3d printed material and oomoo instead), but as i was learning more about the process by watching videos and reading about it, i decided to go with something that's flatter for my first project with composites.

leni haass had the cute idea to make an envelope (out of carbon fiber!?), and i liked it a lot so i decided to mock up a version, first by defining the shape in fusion, and then giving it some imperfection by molding it in blender. see the file here.

i then had to turn the postive cad design into a negative print, so i pulled the file back into fusion and cut a rectangle body using the new shape. that file is here!

i 3d printed that part out using the prusa printers at the harvard reef lab.

then we moved over to the mars lab at mit and i spent a couple hours sanding the print and making sure the corners, edges, and surfaces were smooth and clean and ready for the cast.

then we started preparing for the wet-lay up and vacuum forming process. we started by cutting out fabrics for layering. in this print i used 6 layers, one and the beginning and end of glass fiber, and the four middle layers were a hemp combination weave. to keep the edges from unraveling, you apply a layer of tape around your cut perimeter and do not remove it during the process.

meanwhile, we were applying wax and alcohol based wax release sprays to our molds so that we could actually demold when the composite had formed.

then we were preparing our work area, we had our layers of fabric cut and ready, our vacuum bag layed out on a 'mostly clean' table, our resin ready to go, gloves and aprons on, and our molds waxed and ready to go.

then the race was on. we used a resin that had about 8-10 minutes before it starts to react, which means our work time was about 8 minutes before we had to seal the vacuum bag and start the vacuum. we mixed up the resin under the hood, and then started to form the layers, layering first resin, then fabric, and then gently patting the resin into place to stop the fabric from moving around too much.

then the layers were finished, and we quickly sealed up the vacuum bag to let the resin cure overnight.

when we came back the next morning, the resin had hardened with the extra extracted through the plastic, and demolding was tricky! we used chisels and a little bit of force to pop the composites free.

the finished mold looked great! it has a brown color from the resin, and you can sort of see the warp and weft of the hemp showing through.

the next day we wanted to do a carbon fiber version because it would look so cool, so we repeated the same process, just this time the first layer down in the mold was carbon fiber. it was extra important to not move or warp the threads this time. and there they are together for comparison.