PSI - Issue 33

Emanuele Sgambitterra et al. / Procedia Structural Integrity 33 (2021) 1073–1081 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 4. Manufacturing of SMA-polymer sample for pull-out tests.

SMA-polymer samples were subjected to different thermo-mechanical testing conditions with the aim of simulating the service conditions: 1. Pull-out tests of as manufactured samples; 2. Pull-out test of as manufactured samples after 1000 complete thermal activation cycles; 3. Pull-out tests during thermal activation; These testing conditions were carried out to measure the adhesion properties between SMA and polymer resin under both mechanical and thermal stresses, mainly arising from shape recovery of the SMA wires, as well as to analyze possible damage caused by repeated thermal activations. 3. Results and discussions 3.1. Thermal activation by Joule effect Thermal activation was carried out by Joule effect thanks to a power supplier. In order to calibrate the input current to use that guarantees the complete activation of the wire, preliminary test were performed. These latter consist in applying different input currents to a SMA wire and recording the corresponding temperature profile by an infrared camera (IR Flir A615, with a resolution of 640 x 480pixels and a thermal sensitivity\0.05 °C). A typical IR image of the specimen during heating is reported in Fig. 5.a, whereas Fig. 5.b reports a thermal profile recorded during the current activation. In particular, one can be observed that when the current is applied the temperature of the wire quickly increases, then it stabilizes until the current supplier is turned off and the wires cools down.

Fig. 5. Temperature profile history as a function of the applied electric current. Figure also reports a typical IR image of the sample during the current activation.