Composite Fabrication

I mentored a composite part fabrication project that involved both the fabrication and testing of carbon fiber parts for the Polaris rover.

First, carbon fiber sheets are cut into strips (figure 1). The carbon fiber strips are laid out on a table and covered in resin in figure 2. The resin hardens when it cures at high temperatures in an oven. The carbon fiber and resin are covered in a sheet of plastic and the resin is spread using a thin piece of plastic pushing against the plastic sheet in the direction of the fibers. The extra resin is pulled out of the carbon fiber in this fashion. When all of the fibers are soaked in the resin, the plastic sheet is pulled off (figure 3).

Figure 1: Carbon fiber sheet and strips

Figure 2: Resin is applied to the carbon fiber strips

Figure 3: Work area where carbon fiber is coated in resin

Next, the sheets are laid up against the foam mold (figures 4 and 5). The mold consists of two long foam pieces on either side of a metal piece (figure 6). The mold is constructed in this way so that the metal piece can easily be pulled out and the mold separated non-destructively from the carbon fiber after it has been baked. The carbon fiber strips are wrapped on the part at 30 degrees and 150 degrees so that the unidirectional fibers provide extra strength.

Figure 4: First carbon fiber strip is placed on mold

Figure 5: Carbon fiber strips placed on mold

Figure 6: Polaris swing arm mold

Last, the part is covered in plastic (figure 7 and 8). Tape is applied to seal the air in. A hole is put in the plastic so that the air can be sucked out of the plastic. When all of the air has been removed, the part is put in the oven (figures 9 and 10).

Figure 7: Mold and carbon fiber is vacuum-sealed

Figure 8: vacuum sealed part is ready for oven

Figure 9: swing arm mold and carbon fiber is in oven to cure

Figure 10: Composite and mold bakes

The final piece is in the picture below (figure 11).

Figure 11: final swing arm