Fabrication and cyclic behavior of highly ductile superelastic shape memory composites

To address the problem of steel corrosion, fiber-reinforced polymer (FRP) bars are often used as reinforcement in concrete structures. However, conventional FRP bars are characterized by linear elastic behavior that limits their efficacy in seismic structural applications. This paper investigates the fabrication and cyclic behavior of a relatively new class of composite material known as SMA-FRP that could be used as seismic reinforcement for concrete structures. The new composite comprises a high elongation resin matrix, embedded with superelastic NiTi shape memory alloy (SMA) wires as primary reinforcement. The SMAwires are used either with or without the addition of conventional fibers. The hysteretic nonlinear pseudoelastic behavior of SMA provides the new composite with features that conventional FRP lacks, such as ductility and energy dissipation capability. The experimental program carried out in this study starts with the training of SMA wires, and the investigation of the hysteretic behavior of several types of resin. Two types of SMA-FRP composite material are then fabricated and tested under uniaxial tensile cyclic loading. The first type of composite is reinforced with 100% SMAwires, while the second type is reinforced with hybrid fibers made of SMA and glass-FRP. Test results show ductile behavior of the SMA-FRP composite with no signs of fiber debonding. Fiber-based numerical models are then developed to capture the SMA-FRP composite cyclic response.