Torque measurements of Strontium Ferrite/PA12 composite filaments and 3D printed samples printed in a magnetic field

Magnetic composites are being investigated for use in permanent magnets, transformers, electrical machines, and magnetic shielding. Materials are manufactured through additive processes such as Fused Filament Fabrication to allow for rapid prototyping and highly complex designs compared to magnetic composites manufactured through conventional methods. In this study, magnetic filaments are made by adding 5wt% and 26wt% of SrO(Fe₂O₃)₆ powders into Nylon-12 using a co-rotating twin-screw extruder. Additionally, we apply an external magnetic field during the 3D printing process. This allows the magnetic particles to be oriented in a well-defined direction resulting in the realization of magnetic structures with complex well-defined easy axis and/or magnetic dipole distribution functions that vary across a mesoscopic scale. The magnetic torque curves of the filaments and of 3D printed samples under exposure of a field are determined with a biaxial VSM. The hysteresis curves indicate that manufactured filaments have a flow-induced anisotropy with an easy plane perpendicular to the filament’s cylindrical axis, indicating a wire texture. The 3D printed material also shows field-induced and shape anisotropies.