Thermomechanical response of a shape memory alloy hybrid composite

The shape memory effect is responsible for shape memory alloys (SMA) shape recovery during heating, which can be exploited to generate mechanical work. Composite systems incorporating pre-strained SMA elements have the ability to actively change their shape in a tuneable way. The properties associated to this type of adaptive composites are directly related to the reversible martensitic transformation in the SMA and to the constrained condition of the SMA in the composite matrix.
In the present work the behaviour of a shape memory alloy hybrid composite (SMAHC) has been numerically and experimentally investigated. A hybrid composite plate was fabricated using pre-strained NiTiCu wires embedded in an epoxy resin pre-preg glass fibres laminate composite. A two dimensional finite element model was implemented in order to predict the structural behaviour of the SMAHC, using as input data the material properties of SMA wires and pre-preg composite obtained via calorimetric and mechanical characterisations. In the experimental tests, the plate was clamped at one side and actuated via electrical heating. Resulting data in terms of achieved displacement at the free end of the composite plate, SMA and composite temperatures were used to validate the FEM model. The comparison between experimental and theoretical data show that the model is able to predict the behaviour of the SMAHC if the materials properties are properly characterised.