The performance of nitinol shape memory alloy actuators embedded in thermoplastic composite material systems

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Virginia Tech


Intelligent materials are a class of material systems usually consisting of a composite or hybrid material system with fibrous or distributed actuators, various sensors and a control system. One type of actuator being developed for intelligent material systems is made of nitinol or shape memory alloy wire. In order for nitinol and other actuators to be a reliable part of the system, the effect of composite manufacturing on the actuators’ performance and behavior must be determined. The results of a study investigating the effects of a "high temperature" thermoplastic composite processing cycle on the nitinol actuator’s performance is presented. A study of the interfacial strength between the actuators and APC-2 thermoplastic composite is also reported.

The nitinol actuators were exposed to high temperature (400°C) composite processing cycles. Critical parameters of the processing cycles were varied to determine their effect on the actuators’ performance. After the processing cycles, the nitinol actuators demonstrated useable recovery stresses (σru) of 173-265 MPa. The σru of a nitinol actuator in the virgin state, subjected to a thermoset processing cycle, and embedded in a specimen of APC-2 thermoplastic composite was also tested to develop a basis for comparison. The quality of the actuator-composite interface bond was tested by pull-out testing and fatigue loading to determine if the actuator is adequately bonded with the host composite. Pull-out forces of 30-50 N could fracture the actuator-composite interface, but 1000 activation cycles of the actuator produced no damage in the bond between actuator and host composite.