Encapsulations of Magnetorheological Fluids Within 3-D Printed Elastomeric Cellular Structures

In this study, magnetorheological fluid (MRF) was successfully encapsulated in a 3-D printed elastomeric cellular structure. To this end, an MRF, which was composed of (40% volume fraction) carbonyl iron particles (6- 10~\mu \text{m} in diameter) suspended in silicone oil, was encapsulated in a thermoplastic polyurethane (TPU) elastomeric cellular structure. A 3-D printer was used to print a TPU elastomer with a rectangular cellular structure in the shape of a circular cylinder. The MRF was injected into the rectangular voids within the TPU cellular structure (hereinafter MRF-TPU elastomeric composite), and then sealed into the composite by 3-D printing a capping or sealing layer on top. The mechanical stiffness and damping properties of the MRF-TPU elastomeric composite with respect to external magnetic fields (0, 2, and 7 kG) and excitation frequencies (1, 5, and 10 Hz) were measured via uniaxial dynamic mechanical testing. Also, the effects of excitation and prestrain amplitude on the mechanical properties of the MRF-TPU elastomeric composite were investigated in these experiments. The complex stiffness and dissipated energy measured via dynamic mechanical testing were used as the performance index.