New paper out by Lingzhen Li

Iron-based shape memory alloys (Fe-SMA) form a new solution for strengthening steel structures. The idea, developed at Empa, comes with the benefits of easy and non-invasive application ensuring gradual stress transfer along the bond line, attractive material properties, and affordable costs. As a novel system, adequate undertanding of its mechanical behavior is mandatory prior to standardized implementation.

In this first systematic work on the Fe-SMA-to-steel lap-shear behavior, we conducted 24 lap-shear tests on two types of Fe-SMA (non-prestrained and prestrained), employing three types of adhesives (one linear and two nonlinear) of varying thickness. During the tests, Digital Image Correlation (DIC) is used to measure the full-field displacement and strain of the bonded joints, which are further analyzed to infer the shear behavior along the bond line.

Three stages were observed during the loading process of a bonded joint: (i) the elastic stage, (ii) the damage accumulation stage, and (iii) the debonding propagation stage. It is found that a more ductile adhesive or a thicker adhesive layer provides a higher fracture energy, thus leading to a greater load transferring capacity. The test results are compared against the well studied carbon fiber reinforce polymer (CFRP)-to-steel bonded joints. It is observed that when a linear adhesive is used as the bonding agent, the Fe-SMA and CFRP joints behave similarly. A nonlinear adhesive, on the other hand, results in significantly differentiated behavior, which is due to the difference between the nonlinear Fe-SMA and the linear elastic CFRP. The knowledge summarized in this study can guide the design and standardisation of bonded Fe-SMA strengthening for steel structures.

Read more in the latest publication in external page Volume 364 of Construction and Building Materials.