CHARACTERIZATION AND IMPROVISATION OF DIRECT- INK-WRITING (DIW) TECHNIQUE WITH IN-SITU ELECTRIC FIELD TO PRINT HIGHLY ALIGNED CARBON FIBER/EPOXY COMPOSITE

Abstract

An investigation is presented on direct-ink-writing (DIW) of carbon fiber epoxy composite with and without an electric field. Initial emphasis is focused on the importance of DIW and a common notion that DIW/3D printing aids in better alignment across a printed specimen. For this purpose, the DIW technique is utilized in printing a single filament dog bone specimen, and uniaxial tensile tests were performed on all printed specimens. Furthermore, the microstructure of the printed sample and the fracture surface of the specimens was performed using a high-resolution scanning electron microscope (SEM). It was found that the fibers adjacent to the surface of the printed specimens were highly aligned along the printing direction, whereas the fibers at the core remain mostly misaligned. This could be due to the high shear stress and higher change in velocity gradient of the ink at the inner nozzle wall, which leads to better alignment of the fibers along the print direction. However, very little or negligible change in shear stress and velocity gradient at the core of the ink filament at the nozzle leads to poor alignment of the fibers during extrusion. Thus, integrating DIW and the electric field was conceived, which could effectively be used to align fibers at the surface and the core of the ink filament during the extrusion of the ink. The in-situ electric field, in association with the direct ink writing fabrication (iEF-DIW) technique, effectively aids in controlling both in-plane and through-thickness properties of the composite by controlling the alignment of the carbon fibers. This fabrication technique could effectively replace most of the conventional as well as cumbersome methods that are used to orient/align fibers/fillers in the desired direction.