Improvement in separation of SMA from matrix in SMA embedded smart structures

Crack closure in epoxy resin plates with an embedded spiral shape memory alloy (SMA) wire as an actuator in smart structural members was investigated as a function of the duration of the supply of electric current to the spiral SMA wire under three-point bending using photoelastic experiments. The effect of heat generation due to the spiral SMA wire in the matrix was also investigated. Crack closure was evaluated by the stress intensity factor obtained from the photoelastic fringes generated near the crack tip. The results showed that the closure function in the plate with the spiral SMA wire was slightly inferior to that in the plate with a linear SMA wire. In addition, the spiral SMA wire was observed to greatly improve separation between the matrix and the SMA wire due to the heat generation compared with that of the linear SMA wire.