Magneto-mechanical actuation of ferromagnetic shape memory alloy/epoxy composites

Ferromagnetic shape memory alloys (MSMA) exhibit magnetic field- and stress-induced twinning when processed into single crystals, but are brittle and difficult to shape. Embedding slender single crystalline MSMA elements into a polymer matrix can thus provide composites with adjustable magnetic strain actuation behavior. Ni–Mn–Ga single crystalline rods were characterized for their magneto-mechanical behavior and embedded in two different types of epoxy matrices with different volumetric fractions. The magnetic actuation of the composites was measured and shown to depend on the Ni–Mn–Ga volumetric fraction and the matrix stiffness. This behavior was well predicted by finite element simulations of the composite using a simple material model for the strain of the MSMA as a function of the magnetic field and applied stresses. Guidelines for composite behavior prediction could thus be proposed.