The design of a reversible bending actuator based on a SMA/SMP composite is presented. The SMA/SMP composite is made of SMA NiTi wires with a bent ‘U’-shape in the austenite phase embedded in an epoxy SMP matrix which has a memorized flat shape. The bending motion is caused by heating the composite above TAf to activate the NiTi recovery. Upon cooling, the softening from the austenite to R-phase transformation results in a relaxation of the composite towards its original flat shape. In the three-point bending measurement the composite was able to exhibit a reversible deflection of 1.3 mm on a support with a 10 mm span. In addition, a material model for predicting the composite’s deflection is presented and predicts the experimental results reasonably well. The model also estimates the in-plane internal force and the degree of the SMA phase transformation.

A thermal energy harvester using piezo-shape memory alloy (SMA) composite was designed. The main mechanism of such a piezo-SMA composite is the synergistic effect of piezoelectrics and SMA, which are connected in series and subjected to fluctuating temperature. Strain induced in the SMA phase immediately causes stress in the piezoelectric phase, thus, inducing charge by the direct piezoelectric effect. In order to make this problem more analytically tractable, two models were developed: simple laminated model and 3D model with Eshelby theory. The models predict the available power according to material properties and thermal fluctuation. The impedance of the system was examined with different thermal fluctuating frequencies. Experimental and predicted results are in agreement for higher frequencies, while for lower frequencies of thermal fluctuation, the prediction is not accurate due to internal loss.

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This paper is aimed at to discuss two cases of active composites, (i) ferromagnetic shape memory alloy composites, and (ii) piezoelectric ceramic-shape memory alloy composites. Here we discuss the merits of designing such active composites, for use as possible actuator materials. To optimize the nano-/micro-structures of such composites, we developed analytical models based on Eshelby type modeling. Based on the modeling study; a few cases of optimized active composites are suggested.