Thermal effects on the bond behavior of Fe-SMA adhesive joints: A study on temperatures from −20°C to 80°C

Post-tensioned strengthening using adhesively bonded iron-based shape memory alloy (Fe-SMA) strips can significantly increase the cracking load and post-fracture capacity of laminated glass beams. In this study, a finite element model was developed to investigate the bond behaviour of the Fe-SMA-to-glass lap-shear joints at varying service temperatures of −20, 23, 50, and 80 °C. Validated on experimental results, the finite element model was used to further study the mechanical behaviour of Fe-SMA-to-glass lap-shear joints with various adhesive thicknesses (0.5 and 1.5 mm), Fe-SMA strip thickness (0.5, 1.5 and 3.0 mm) and bond length (50, 100, 150, 300 and 450 mm). The effective bond length was observed to increase from 129 mm at −20 °C to 252 mm at 80 °C while the adhesive thickness was kept 1.5 mm. Increasing the Fe-SMA strip thickness from 1.5 mm to 3.0 mm significantly increased the load-carrying capacity, though it decreased the joint deformability. When shorter than an effective bond length, increasing the bond length significantly increased the load-carrying capacity. At relatively short bond lengths (e.g., 50 mm), service temperature had a pronounced impact on the bond performance. However, once exceeding an effective bond length, the influence of service temperature and adhesive thickness on bond capacity diminished considerably. These findings provide critical insights for optimizing the design of Fe-SMA-to-glass adhesive joints in structural applications, such as post-tensioined laminated glass beams in façade systems, ensuring reliable performance under a wide range of service temperatures.