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SMA actuators are a new kind of force-displacement actuators which act based on the unique property of shape recovery of the shape memory alloys. In this paper a mathematical model is presented for approximate responses of a novel thermally driven SMA actuator under arbitrary loading and boundary conditions. The actuator is a laminated composite beam made of SMA and elastomer layers, with a
hollow rectangular cross section. The
actuator has the ability to act in three dimensions, but here, modeling is done only for the 2-D conditions. The thermomechanical behavior of SMA layers is expressed using Tanaka and Nagaki's one-dimensional constitutive equation, together with a linear phase transformation
kinetics. The thermoelastic behavior of
elastomer layers is expressed by Hooke's law, in which the changes of the elastic modulus with temperature, is considered using an approximate linear function. The general form of the classic beam equations
is used for the force-deformation relationships. This model gives explicit

solutions for the structural response of
actuator, including midplane-strain and curvature, in terms of the variable parameters such as activation temperatures, the layers' thicknesses, .. .etc. A numerical example for a cantilever beam with hollow square cross-section subjected to a transverse concentrated load is presented. Results show that when the: phase transformation starts in the heated SMA layer, significant changes in the actuator'.s response occurs due to strain recovery in it.