Actuation properties of adaptable hybrid composites with embedded shape memory alloy wires

Adaptable hybrid composites are materials in which actuators are embedded into polymer matrix composites. Shape memory alloys (SMA) are among the potential candidates for actuators embedded in such composite smart structures. After plotting Clausius-Clapeyron diagrams for three structural states, thin wires ('fi'=120 micrometers) of Nickel-Titanium-Copper (nitinol) were incorporated parallel with the reinforcing fibres into a glass-epoxy unidirectional laminate during lay-up. Then the whole structure was subjected to different curing procedures. The interfacial shear strength between the matrix and the nitinol wires in various structural states was determined by micromechanical tests involving the interface directly: the pull-out and microdebond tests. The clamped-free (cantilever) beam method was used to evaluate the effect of actuation by heating the nitinol wires embedded into the composite. The comparison between the different composites points out to the leading role of the interfacial shear strength. The influence of the training conditions before embedding and the occurrence of a self-trained two way shape memory effect, can also be noted.