Design of a Shape Memory Alloy Actuator for Self-Deployable Heat Exchangers

The design of thermally driven self-deployable heat exchangers is a challenging thermomechanical problem. The driving concept is the coupling of a foldable heat exchanger with Shape Memory Alloy (SMA) actuators to passively engage the deploying system. SMA materials have stress-temperature dependent mechanical behaviour, a characteristic exploited in thermally controlled actuation. This experimental work reports on the design and testing of a deployable panel driven by passive heating. The SMA actuator is a Nickel-Titanium wire (SmartFlex® Wire), supplied by SAES group® company. The maximum deploying angle of the panel is about 62 degrees and is measured if the actuator is warmed up above the austenite finish temperature through Joule effect. The tests showed that using Teflon coating or shaving foam, which reduces, thermal exchange, can increase the deploying angle up to 7 degrees. Further tests on higher performance foams and a three-wire configuration will be considered to allow the full deploying of the panel.