Researchers at Oak Ridge National Laboratory (ORNL) have been exploring the use of biocomposite materials for additive manufacturing. In 2016, they produced a 3-D printed table made from a bamboo composite. So when SHoP Architects of New York contacted them last summer about using that bamboo material to build sections of two pavilions, researchers were eager to participate. But they were also a little daunted by the task. “We were going to go from a small table to a structure that required 10,000 pounds of material,” says Soydan Ozcan, a senior R&D scientist in composites and additive manufacturing at ORNL.
SHoP won a competition to design two entrance pavilions for the 2016 edition of Design Miami, a yearly showcase for architects and design professionals. The firm tapped Branch Technologies to print the overhead structural trellis/framework for the pavilions – named Flotsam & Jetsam – and asked ORNL to manufacture the support legs, seating areas and counter space.
The entire structure was printed using a 100 percent biobased and biodegradable composite material – a bamboo-fiber reinforced biopolymer formulation, made with 20 percent bamboo and 80 percent polylactic acid (PLA), a biodegradable, thermoplastic polyester.
“Making the material printable is the No. 1 manufacturing challenge,” says Ozcan. “We had to go to the manufacturer to modify the material and adjust it for the layer time. In order to get the needed strength when the two layers are bonded together, the first layer needs to be fully solidified before putting the second one on.” ORNL researchers worked with Sunstrand, which fillibrated the bamboo materials to the correct micro size so they could be used in the composite material.
ORNL researchers also wanted a material that could move through the printer more quickly and was UV-resistant so it could survive the harsh Miami sun.
The laboratory used its Big Area Additive Manufacturing (BAAM) printer to produce the pavilion components. With BAAM, ORNL can manufacture parts up to 20 feet wide, six feet long and eight feet high. The laboratory printed the pieces in about a week working around the clock, processing about 50 pounds of the bamboo composite per hour. Ozcan says the manufacturing process took longer because this was ORNL’s first big structure and they had to work out some kinks in the process. The BAAM machine is capable of nearly double that speed using the biomaterial composite.
The biodegradable bamboo composite has one-third of the embodied energy and a carbon fiber footprint that’s 90 percent less than a comparable carbon fiber composite, Ozcan says. Although it might not offer the same strength properties as carbon fiber, the bamboo composite was more than strong enough for this application, and it offers many other advantages. One of those is cost; bamboo composites are 40 to 50 percent cheaper than carbon fiber composites.