The Octave 9 panels were manufactured from reclaimed unidirectional Toray carbon fiber epoxy prepreg using a quasi-isotropic layup, standard vacuum bagging process and 250 degrees Fahrenheit oven cure for 120 minutes. The 10 x 10-foot panels were then trimmed to their final 7.5 x 8-foot size using a water jet. “The water jet gave it a nice finish, and we were also able to put the hole pattern [for fasteners] in really precisely, which made the assembly a breeze for them,” Poulin notes. The black walnut wood veneer, which was stained to match existing wood in the music hall, was cut to shape with a veneer saw and bonded to the CFRP panel with contact cement.
The size of the panels presented a few challenges. “It’s pretty rare for a company our size to be doing 10 x 10-foot parts,” says Poulin. “Those are pretty big parts, and having good cosmetic properties and getting compaction across the part can be tricky.” Applying veneer to such large panels was also a new experience for CRTC.
Crawford says that the CFRP panels provide numerous advantages over the originally specified acrylic ones. Foremost is weight savings. He calculates that the 30-pound CFRP wood veneer panels provided an 83% weight reduction, making them easier to install and move. They also added shear strength, stiffening the entire structure and reducing bouncing and vibration when the sections are wheeled through the hall. The 1.4-millimeter-thick panels could also be bent into shape, eliminating the need for an expensive curved mold. “The entire assembly of carbon fiber and wood veneer was flexible enough that they could just bend it to fit onto the back of the frame, and that kept the overall cost down,” Crawford stresses.
Using scrap prepreg also reduced costs, making it possible to even consider CFRP. “One of the biggest challenges to the use of composites in architecture is the up-front cost of the material, and oftentimes if you’re not going to get a significant benefit from either the light weight or the corrosion resistance, then it’s hard to make it pencil out,” says Crawford. “But in this case, since [CRTC] is getting this stuff and reusing it, it lowers that initial cost, so it made it more possible for us to explore.”
Poulin stresses the cost savings as well. “It’s pretty unique to switch to carbon fiber and still be within budget,” he reflects. “I think that’s the biggest takeaway – that we were able to show that repurposed carbon fiber is economically feasible.”