Further Research Into High Strain Magnetostriction in a Ferromagnet-Polymer Composite

Abstract

We have conducted experiments on metal-polymer composite materials to optimize high-strain magnetostriction (magnetically-induced stretching). Our goal was to produce composites exhibiting large strains (order of 20%) in weak magnetic fields (order of 5 kOe). The intent is to develop novel magnetostrictive materials for technological applications such as a magnetically activated mechanical actuator. The exploratory research included how wire loading and wire length affect the strain. Composites were constructed by suspending short steel wires in soft polymer with variation of wire loading and wire length. Composites were placed in a magnetic field that ranged from 0 to 7.5 kOe, with strain measured by video analysis software and compared at 3.0 kOe. Our results indicate that strain increases with wire loading up to a maximum value, and then further loading reduces strain. This loading associated with maximum strain is higher for shorter wire lengths. The measured maximum strain of 38.8% in a 3.0 kOe field using 0.50 cm wire and 0.100 wire volume fraction is the maximum observed in any system to date. Therefore, significant strain can be achieved in relatively weak magnetic fields: additionally, shorter lengths and higher wire loading could further optimize strain.