Hard magnetic elastomers incorporating magnetic annealing and soft magnetic particulate for fused deposition modeling

Abstract

Magnetic elastomers with hard or permanent magnetic particulate are able to achieve complex motion not possible from soft magnetic elastomers. Magnetic annealing and fused deposition modeling (FDM) have been used to increase the performance of magnetic composites. This research explores how the magnetoactive properties of hard magnetic elastomers are influenced by magnetic annealing and the addition of the soft magnetic particulate. Three compositions of the thermoplastic magnetic elastomer composite are explored: 15 vol. % SrFe12O19, 10 vol. % SrFe12O19/5 vol. % carbonyl iron, and 5 vol. % SrFe12O19/10 vol. % carbonyl iron. The material is then extruded into FDM filaments. During the extrusion process, some filament is magnetically annealed in an axial applied field. Magnetic hysteresis loops show that the saturation magnetization and coercivity change based on the relative amount of hard and soft magnetic particulate. The presence of only one coercive field indicates magnetic coupling between the hard and soft components. Magnetoactive testing measures each sample’s mechanical deflection angle as a function of transverse applied magnetic field strength. Qualitative and quantitative results reveal that magnetic annealing is critical to the magnetoactive performance of the hard magnetic elastomers. The results also demonstrate that magnetic annealing and increased carbonyl iron both improve the magnetoactive deflection angle for a given applied field. Scanning electron microscopy shows a stratification effect in a range of the filaments. Understanding these hard magnetic elastomers provides insight into how performance can be controlled and optimized by magnetic annealing and combining hard and soft magnetic particulate.