Wood is a ubiquitous, natural example of a composite material: Within its cell walls, cellulose fibers provide structure and strength and are held in place by a matrix of lignin. Brett Compton and Jennifer Lewis of Harvard University have now demonstrated how the additive techniques of three-dimensional printing can be enlisted to manufacture cellular composites whose strength and stiffness nearly match those of wood.
In typical 3D printing, a heated and softened plastic extrudes through the printing nozzle, cools, and rehardens. In the researchers’ composite, silicon carbide whiskers and carbon fibers play the reinforcing role of cellulose and are held in place by a matrix of cross-linked epoxy molecules. For 3D printing, the “ink” requires carefully tailored composition and rheology. As the nozzle traces each successive layer of the 3D pattern, the ink has to extrude easily from the few-hundred-micron-wide opening and afterward maintain its filamentary shape and position. Starting...
