Shape memory alloys (SMAs) have the ability to recover a predetermined shape when heated. The property in SMAs is due to a martensitic phase transformation which occurs with a change in their temperatures. SMA composite beams and actuators are a kind of smart structures which are composed of a matrix material with SMA sheets or wires embedded in and/or bonded on the matrix part, and can be activated with heating the SMAs. Shape memory alloys have nonlinearities in their thermo-mechanical behavior, and their material properties change with temperature. Also, due to occurrence of large stress and strains in SMAs, the SMA composite structures have geometrical nonlinearities. The nonlinear behaviors make the modeling of SMA composites complicated. In the present research, a nonlinear finite element model is developed for the transient response of 3D SMA composite beams and actuators. The F.E. model is derived by utilizing the weak forms of the equilibrium and energy balance equations, and a constitutive relation with variable material functions for SMA. The model can simulate active and passive responses of the structures. The developed F.E. model is implemented on an example beam, and the numerical results are presented graphically.
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