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Although shape memory alloy/Polyvinyl alcohol (SMA/PVA) hybrid fiber reinforced cementitious composites, (SMA/PVA-ECC) exhibit excellent crack closure and deformation recovery capabilities, however, the research on their fundamental mechanical properties is still limited. This study investigates the tensile mechanical properties of SMA/PVA-ECC materials by conducting uniaxial tensile tests, analyzing the failure behavior, stress–strain curves, and characteristic parameters of the specimens, comparing the influence of SMA fiber content and diameter, and establishing a tensile constitutive model. The results show that the residual crack width of SMA/PVA-ECC specimens significantly decreases after unloading, and SMA fiber content and diameter have a significant impact on the tensile properties of the specimens. The comprehensive tensile properties of specimens with a fiber diameter of 0.2 mm and content of 0.2% are the best, with their initial cracking strength, ultimate strength, and strain increasing by 56.4%, 23.6%, and 13.4%, respectively, compared to ECC specimens. The proposed bilinear tensile constitutive model has high accuracy. This study provides a theoretical basis for further research on SMA/PVA-ECC materials. [ABSTRACT FROM AUTHOR]

SMAF-ECC material composed of shape memory alloy fiber (SMAF) and engineered cementitious composite (ECC) has good bending and tensile properties, as well as good crack self-healing ability, energy consumption, and self-centering ability. The bond behavior between fiber and matrix is crucial to the effective utilization of the superelasticity of SMAF. The experimental study considered three variables: SMA fiber diameter, fiber end shape, and bond length. The pullout stress–strain curve of SMAF was obtained, and the maximum pullout stress, maximum bond stress, and fiber utilization rate were analyzed. Compared with the straight end and the hook end, the maximum pullout stress of the specimen using the knotted end SMAF is above 900 MPa, the fiber undergoes martensitic transformation, and the fiber utilization rate is above 80%, indicating that the setting of the knotted end can give full play to the superelasticity of the SMAF. Within the effective bond length range, increasing the bond length can increase the maximum anchorage force of the knotted end SMAF. Increasing the fiber diameter can increase the maximum pullout stress and maximum anchoring force of the knotted end SMAF but reduce the utilization rate of SMA fiber. This study provides a reliable theoretical basis for the bonding properties between SMAF and ECC. [ABSTRACT FROM AUTHOR]

The combination of superelastic shape memory alloy fibers and ECC materials can form a new SMA fiber reinforced ECC composite material (SMAF-ECC) with good self-centering performance. In order to study the self-centering performance of the new composite material, 6 groups of pre-notch beam specimens were made for three-point bending cyclic loading tests, and the failure phenomenon, hysteresis curve, self-centering effect and influencing factors of the specimens were analyzed. The research results show that when the SMA fibers are effectively anchored in the ECC matrix, the SMA fibers can exert the superelastic properties to provide the ECC beams with recoverying force, and realize the crack self-closure and deflection self-recovery function for the beams, with the minimum residual crack width and deflection is only 0.9 mm and 1.3 mm respectively. Increasing fiber content can cause a small increase in the self-centering ability of the beams. However, only when the fiber diameter is appropriate, better self-centering effect can be achieved, but the difference caused by fiber diameter in the test was only 5%. SMA Fiber end forms have significant influence on self-centering performance. The knotted end beam can get a more than 70% self-centering ratio, while the straight end beams and bended end beams have no self-centering ability. The research results provide important reference for the research and application of this new self-centering materials and their structures. [ABSTRACT FROM AUTHOR]