Three-Dimensional Property Enhancement of Composites by Realization of Three-Dimensional Fiber Alignment via Embedded Direct Ink Writing

The orientation of fibrous fillers, induced by shear forces during extrusion, has been extensively demonstrated to exert a significant impact on various material properties such as mechanical properties, electrical conductivity, thermal conductivity, and microwave attenuation. However, these effects have primarily been observed in a two-dimensional (2D) x-y plane. In this study, we propose a novel approach to achieve fiber alignment in a three-dimensional (3D) context, specifically focusing on the Z-direction, by employing embedded 3D printing techniques. This methodology involves the extrusion and suspension of composite inks within a viscoelastic gel medium, allowing the control of fiber alignment through processing conditions such as velocity ratio, nozzle size, and fiber dispersion. By selectively aligning the fibers in a 3D pattern, it becomes possible to significantly enhance and tailor the mechanical properties and conductivity in a three-dimensional manner.