Researchers at Harvard University have developed a carbon-fiber reinforced epoxy ink, shown here printed in a hexagonal honeycomb.

Researchers at Harvard University have developed a carbon-fiber reinforced epoxy ink, shown here printed in a hexagonal honeycomb.

Credit: Brett G. Compton, Harvard University

In an earlier post concerning bioactive glass, I discussed the development of inorganic materials to support living tissue. A recent development by researchers at Harvard University’s Wyss Institute and its School of Engineering and Applied Sciences (SEAS) reveals the sophisticated manipulation of inorganic substances to mimic the performance of a living material. Specifically, the scientists have been able to fashion fiber-reinforced epoxy composites to emulate the cellular structure and mechanical characteristics of balsa wood.

Why balsa wood? The material is used extensively as the interior core of wind turbine blades due to its lightness and stiffness. But the design of ever-longer blades has increased demand on the supply and performance of the material at such a scale.

Left, a triangular honeycomb composite structure is printed using the material. Right, a schematic illustration of the composite ink deposition with fibers oriented in the direction of the print.

Left, a triangular honeycomb composite structure is printed using the material. Right, a schematic illustration of the composite ink deposition with fibers oriented in the direction of the print.

Credit: Brett G. Compton, Harvard University

Square, hexagonal, and triangular honeycomb structures printed with the carbon fiber–reinforced epoxy resins.

Square, hexagonal, and triangular honeycomb structures printed with the carbon fiber–reinforced epoxy resins.

Credit: Brett G. Compton, Harvard University

Using advanced 3D extrusion printing, the researchers were able to fabricate carbon fiber–reinforced epoxy resins that perform as well as or better than balsa wood and other synthetic polymer composites. "Balsa wood has a cellular architecture that minimizes its weight since most of the space is empty and only the cell walls carry the load," said Jennifer Lewis, a professor of materials science and mechanical engineering at Harvard's SEAS and a co-author of the related paper published online last month in the journal Advanced Materials, in a press release. "It therefore has a high specific stiffness and strength. We've borrowed this design concept and mimicked it in an engineered composite.”

Although wind turbines are the research's primary application, the development of ultralight, mechanically precise materials could benefit many fields. The researchers are considering future uses in the automotive industry, with aerospace as a potential counterpart. Architecture could also benefit from the advancement of structural composites that are minimal in weight and bulk. But carbon fiber–reinforced plastics aren’t cheap. Moreover, a focus on this kind of energy-intensive composite calls for further life-cycle study. If economic and environmental hurdles cannot be overcome, it may be better to stick with balsa wood for most applications.

Blaine Brownell, AIA, is a regularly featured columnist whose stories appear on this website each week. His views and conclusions are not necessarily those of ARCHITECT magazine nor of the American Institute of Architects.