PSI - Issue 64

Zhikang Deng et al. / Procedia Structural Integrity 64 (2024) 400–408 Zhikang Deng / Structural Integrity Procedia 00 (2019) 000 – 000

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3. Experimental program 3.1. Test specimens

Two specimens were manufactured and tested in this investigation. The Fe-SMA strips (750 mm x 25 mm x 1.5 mm in length × width × thickness) were adhesively bonded to both sides of the monolithic annealed glass pane. The glass dimensions were 750 mm x 250 mm x 10 mm (length × width × thickness). The adhesive layer was controlled at approximately 1.5 mm in thickness. The geometric configuration of the specimen is shown in Fig. 2. The pre-defined activation length (L_ac1) was 400 mm. The anchorage zone at the two ends was 175 mm, which was longer than the maximum effective bond length defined in a previous investigation by Silvestru et al. (2022a).

Fig. 2. Geometry dimension, thermocouples and strain gauge locations for the activation test specimen.

The specimens were manufactured and cured at room temperature. The Fe-SMA strips were firstly sandblasted at a pressure of 8 bar using 0.15-0.21 mm aluminium oxide to remove the oxidized layer and increase the surface roughness. Then the Fe-SMA and glass were cleaned with acetone before bonding. Two 1.5 mm-thick Teflon strips were placed at the two ends of the bond line to ensure a 1.5 mm bond thickness. Steel weights were put on the top surface of the Fe-SMA to squeeze excess adhesive and to guarantee uniform bond thickness during the adhesive curing process. These weights were removed after 24 hours. Two Fe-SMA strips were bonded to the glass pane as shown in Fig. 2. One Fe-SMA strip was bonded to one side of the glass according to the above process, and after curing at room temperature for 24 hours, the other Fe-SMA strip was bonded to the other side of the glass. Subsequently, the specimens were stored in a climate-controlled room at a temperature of 23 °C and a relative humidity of 50% for at least two weeks before testing. 3.2. Test procedures For these activation tests, A high-current power supply (Model 4G-100, capable of reaching 100 A) was employed based on electrical resistive heating to activate the Fe-SMA. The test procedure consisted of 4 steps. In step 1, the activation length (L_ac1) as illustrated in Fig. 2, was subjected to heating up to 160 °C. The generated pre-stress was reflected by the compression strain of the glass pane, measured by strain gauges from HBK throughout and after the activation process. In step 2, the length L_ac1 was activated at 200 °C to further increase the pre-stress level. The steps 1 and 2 were carried out at room temperature. In steps 3 and 4, both specimens were kept in the climate chamber at 50 °C, first, and 80 °C, later. These steps were conducted to measure the pre-stress loss resulting from elevated service temperatures, mimicking the situation when the joints would be subjected to direct sunlight in summer. The