Fabrication and evaluation of SMA-silicone rubber continuous-fiber and particulate composites

Abstract

Shape Memory Alloys (SMAS) may be combined with elastomers to produce composites with unique material and structural behavior. Because of the high damping characteristics of the low temperature SMA phase, the addition of SMA particles to an elastomer may produce a composite with a damping capacity more thermally stable than the elastomer alone. Effective composite properties from micromechanics and the correspon dence principle from viscoelasticity are used to predict the damping capacity of an SMA particulate-elastomeric matrix composite. The embedding of Ni-Ti SMA wire actuators into flexible silicone rubber rods can affect the composite structural behavior by causing the rods to deflect upon heating and shape recovery of the SMA wires. The wires were at first prepared and actuated in the rods according to the shape memory effect, but the relaxed shape of a rod after actuation was different from the original shape. A procedure to train Ni-Ti wire to exhibit the twoway shape memory effect, a behavior involving a thermally induced and zero-stress reversible transformation strain, was established. Rods fabricated with two two-way trained wires deflected in one of two opposite, yet planar directions, according to the SMA wire being heated, and they relaxed to the straight, undeformed shape upon cooling of the SMA wires. Modelling of the response of the flexible rods with embedded actuators included both a closed-form solution of the fully actuated state and an incremental formu lation that accounts for different temperature histories. The deflections of fully actuated rods were predicted within a reasonable accuracy.