Phase transformation behavior of thin shape memory alloy wires embedded in a polymer matrix composite

Shape memory alloy composites (SMA-composites) are adaptive materials, whose external shape or mechanical properties can be controlled by the activation of embedded SMA actuators. While considerable information is now available on the structural, mechanical and functional behavior of plain SMAs, nearly nothing is known about embedded SMAs. However, the characteristics of the matrix, and its viscoelastic properties in particular, can have an influence on the martensitic transformation and therefore on the functional properties of the SMA actuator. Accordingly, there is a considerable interest in studying the transformation behavior of embedded SMA. In this work, the transformation behavior of thin NiTi wires, incorporated into epoxy resin is studied by dynamic mechanical analysis and calorimetry. The dynamic mechanical behavior of the SMA composites is compared to that of plain SMA wires. Simple beam bending theory is used to predict the dynamic moduli of the SMA composite from the measured dynamic moduli of the constituents as input data. The difference between the predicted and the measured behavior is analyzed in term of SMA/matrix interaction