To park visitors, the pavilion may seem deceptively straightforward. Above the bell, 17 free-floating arched beams cantilever from a central concrete/steel superstructure. To create the appearance of an open dome for anyone standing beneath the structure, each beam features an entirely different arc radius.
Because there was no consistency among the beams, molds were immediately ruled out. From there, the University of Tennessee/IACMI team was challenged to develop a cost-effective method for manufacturing 17 unique CFRP beams.
“Many factors went into determining the easiest and cheapest way to produce this without a mold because it had to be a continuous chain for each different arch for the beam,” Vaidya explains. Ultimately, the team hit upon a combination of vacuum infusion, braiding and overbraiding.
“Braiding technology is unique in that it’s able to bring in fibers from different angles and strengthen those based on direction,” Vaidya says. Each beam began with a high-performance polyurethane foam core that was curved to the desired shape. Next, the foam core was sent through a braiding machine where Toray T700 24K standard modulus carbon fiber was wrapped around the foam in a triaxial architecture. Finally, the overbraided form was vacuum infused with a thermoset epoxy resin, fully encapsulating the core.
“This being a prototype, we learned as we went,” Vaidya adds. “It took us about six weeks to produce these 17 beams. I believe if this were an industrial scenario you could probably make them in a week.” The carbon fiber braided arched beams won the Award for Composites Excellence (ACE) for Most Creative Application at CAMX 2019.
Advantages that Appeal to Architects
The Friendship Bell Pavilion highlights one of the primary attractions of composite materials in architecture – their ability to create any shape.
“Shape continues to be attractive to architects, and certain shapes are just problematic to do in concrete and steel and aluminum,” says Andy Bridge, vice president of industrial markets and director of research and development with manufacturer Janicki Industries. “So, architects find themselves intrigued by or having to turn to composites.”
Sustainability also resonates strongly with architects, and this “green” focus could help garner greater interest in composites. While composite materials’ documented durability attests to the fact that it can lengthen a project’s lifespan, designers may be more interested in the integration of recycled materials to create architectural structures.
The Meteghan River house in Nova Scotia, which Composites Manufacturing magazine featured in its September/October 2019 issue, is a case in point. JD Composites Inc. built a 2,000-square-foot waterfront home featuring engineered beams and walls made from Armacell’s 100% recycled PET foam panels. The product has been tested to withstand a Category 5 hurricane, achieves an R30 insulation value and diverted about 612,000 plastic bottles from landfills in the process.