THE ACTUATION RESPONSE OF MODEL SMA HYBRID LAMINATES

This paper presents the results from an experimental study on the actuation response of composite laminates containing Shape-Memory Alloy (SMA) actuators. Unidirectional glass-fibre reinforced epoxide laminates were constructed containing Ni-Ti SMA actuators orientated parallel to the glass-fibre direction. The volume fraction of actuator was varied in the range 0 to 2.5 vol%. These laminates were actuated electrically and were designed to exhibit macroscopic shape changes during actuation. The work presented in this paper was a preliminary appraisal of the durability issues associated with the use of such hybrid composites. This has shown that actuator fraction plays a significant role in controlling both the shape change obtained from these materials and the hysteresis associated with their forward and reverse actuation. It has also been shown that during cyclic operation hybrid laminates can suffer from instabilities in shape change due to the accumulation of internal damage. However, by careful selection of the maximum actuation strain and actuator fraction it is possible to achieve useable and stable cyclic shape changes.