Crack recovery and re-centring performance of cementitious composites with pseudoelastic shape memory alloy fibres Ayoub Dehghani, Farhad Aslani ⇑ Materials and Structures Innovation Group, School of Engineering, The University of Western Australia, WA, Australia highlights Hooked-end SMA fibres were manufactured and used in cementitious composites. Crack-closing and re-centring behaviour of the composites were studied. DIC technique was used to capture full-depth crack width profiles. Fibre distribution was examined by l-CT images and statistical point processes. The re-centring and crack-closing ratios were as large as 75% and 51%. article info Article history: Received 25 February 2021 Received in revised form 19 May 2021 Accepted 6 June 2021 Keywords: Pseudoelastic shape memory alloy fibres Re-centring Crack recovery Fibre dispersion Spatial point pattern analysis Cyclic loading abstract Newly developed hooked-end pseudoelastic shape memory alloy fibres (PSMAF) provide re-centring and crack-closing behaviour in cementitious composites. Relatively large PSMAF-reinforced specimens are tested under cyclic flexural loading at small and large deflection amplitudes to examine these capabilities realistically. Crack propagation, maximum crack width at each cycle, crack-closing ratio, and full-depth crack width are quantified through 2D digital image correlation (DIC) technique for composites with 0.5% to 1.25% PSMAF. The re-centring ratios are established for the developed composites, and their flex- ural performances are evaluated based on various parameters, including cyclic modulus, toughness, and ductility. Furthermore, X-ray micro-computed tomography and statistical analysis of spatial point pat- terns are employed to examine fibre dispersion in the cracked sections. Results indicate that PSMAF-reinforced composites with 0.75% and 1% fibre content exhibit considerable re-centring and crack-closing capabilities with minimal fibre clumping. Ó 2021 Elsevier Ltd. All rights reserved. 1. Introduction Shape memory alloys (SMA) have been increasingly considered for structural engineering applications due to their exceptional strain recovery, excellent resistance against corrosion, and good energy absorption capacity. SMA can be classified as those with shape memory effect and pseudoelastic performance. The strain recovery is activated upon heating for SMA with shape memory effect and upon unloading for pseudoelastic SMA. In this study, the focus is on pseudoelastic SMA. It is noteworthy that pseudoe- lasticity stands for both superelastic and rubber-like behaviour [1]. The pseudoelasticity with almost full strain recovery occurs due to phase transformation from austenite to martensite at temperatures above the austenitic finish temperature (A f ). When pseudoelastic SMA are subjected to mechanical stress, the forward phase transformation to martensite starts and ends at stress levels r Ms and r Mf , respectively. During unloading, the onset and end of reverse transformation into austenite occurs at stress level r As and r Af , respectively (see Fig. 1). The distinctive ability of SMA in recovering large inelastic defor- mation upon stress removal leads to a unique hysteresis behaviour, where they can dissipate significant energy with a negligible resid- ual strain. Pseudoelastic SMA also benefits from high corrosion resistance and long fatigue life [2,3]. SMA in the form of wire and bar have been used to develop seismic damping devices [4,5], con- nectors for beam-column joints [6,7], and prestressing elements (typically by using shape memory effect) [8,9]. Researchers have also used SMA wires and bars to enhance the cyclic performance of reinforced concrete (RC) members and provide them with re-centring and crack-closure capabilities. The former is referred to as the member capability to return to its undeformed shape. https://doi.org/10.1016/j.conbuildmat.2021.123888 0950-0618/Ó 2021 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Materials and Structures Innovation Group, School of Engineering, The University of Western Australia, WA, Australia. E-mail address: [email protected] (F. Aslani). Construction and Building Materials 298 (2021) 123888 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat 168
Crack recovery and re-centring performance of cementitious composites with pseudoelastic shape memory alloy fibres
May 20, 2023
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