Shape memory alloys as strain sensors in composites

Composites of shape memory alloys (SMA) with a matrix have been widely studied to suppress propagating damage of the matrix, where the embedded SMA is used as an actuator. We use the embedded SMA wire in composites both as an actuator and as a strain sensor. The possibilities of using the SMA wire as a strain sensor to obtain an actuation trigger signal for damage suppression were investigated using the variation of the SMA electric resistance. We determined that the electric resistance variation of the SMA wire is correlated with the strain. The temperature dependence of the correlation, which can be reduced by a compensation method, is also discussed.