EVALUATION OF CRACK CLOSURE IN INTELLIGENT STRUCTURE MEMBER WITH EMBEDDED SMA

Crack closure in epoxy resin plates with embedded shape memory (SMA) w ires as an actuator in intelligent structure members was investigated as a function of the length of crack, duration of the supply of electr ic current to the SMA wires and the volume fraction of the SMA wires u nder tensile loads using photoelastic experiments, The effect of heat generation due to the SMA wires in the plate was also investigated. Th e crack closure was evaluated by the stress intensity factor obtained from photoelastic fringes generated near the crack tip. The results sh owed that the closure strongly depended on the crack length and durati on of the current supply. The closure was not found in the plate with a crack which did not pass through the SMA wires. A complete cessation of the supply caused the disappearance of the closure with time. Cont inuous current supply resulted in change in quality of the epoxy matri x and separation of the SMA wires from the matrix. The intermittent cu rrent supply prevented the separetion and maintained the closure.