Comparison of magnetic field controlled damping properties of single crystal Ni-Mn-Ga and Ni-Mn-Ga polymer hybrid composite structures

Magnetically controlled hybrid Ni-Mn-Ga composites are potential candidates for actuation and damping applications. The combination of ductile polymer and gas atomized large grained Ni-Mn-Ga powder has many advantages compared to bulk single crystals. These advantages include ease of manufacturing and freedom of shape, while still being magnetically controllable. In this report, Ni-Mn-Ga-epoxy hybrid composite structures are manufactured at three different filling ratios 25, 30 and 35 vol-% and damping properties of the composites are compared to those of 5M Ni-Mn-Ga single crystal. The damping properties are characterized using a laboratory made high-frequency dynamic mechanical testing instrument and a dynamic mechanic analyzer (DMA) in single cantilever mode. The mechanical cycling experiments revealed that the damping ability of the Ni-Mn-Ga composites depends on the filling ratio. The magnetic field induced stiffening observed in the mechanical cycling experiments of the single crystal sample at 100 Hz correlated roughly with that of the composite sample having filling ratio of 35 vol-%.