Micro- and nano-scale filler materials are commonly used to create composite feedstocks for robocasting and are available in a wide range of compositions, with morphologies typically falling into the broad categories of spheres, platelets, and filaments/tubes. Both composition and morphology play significant roles in the mechanical characteristics imparted by the filler. For example, the inclusion of stiff boron nitride nanobarbs within epoxy feedstock has been demonstrated to anisotropically increase overall composite strength and stiffness along the direction of fiber orientation due to their shape asymmetry, while the inclusion of hollow glass microspheres within the same epoxy feedstock has been demonstrated to isotropically improve specific strength by significantly reducing total density of the composite.
