Modeling and Analysis of a Shape Memory Alloy-Elastomer Composite Actuator

A theoretical model of the stress-strain-temperature response of a thermally driven. shape memory alloy (SMA) composite actuator under applied load is developed. The actuator is assumed to be constructed from a thin layer of SMA bonded to a layer of elastomer. The model is developed by considering an energy balance on the SMA and force equilibrium for both SMA and the composite. It includes the martensite fraction of the SMA as a state variable which describes the phase transition process and the constitutive relation of the SMA. Closed-form solutions for the stress-strain-temperature response are obtained by assuming that heat conduction in the axial direction is negligible. Parametric studies are conducted to show how the material properties of the elastomer and geometric dimensions of the actuator affect the thermal and stress responses of the actuator. Finally, the actuation force as a function of the heating power is predicted by the model.