Characterization of superelastic shape memory alloy fiber-reinforced polymer composites under tensile cyclic loading

Highlights: • Superelastic NiTi SMA fibers are used to reinforce a thermoset polymer matrix. • SMA-FRP coupons with three different reinforcement ratios are fabricated using modified hand lay-up technique. • The uniaxial tensile tests are conducted under cyclic loading protocols at various stress levels. • Results show that the SMA-FRP composites can recover relatively high strains upon unloading. Fiber reinforced polymer (FRP) composites have been increasingly used in engineering applications due to their lightweights, high strength, and high corrosion resistance. However, the conventional FRPs exhibit brittle failure at relatively low ultimate tensile strains, low toughness, and limited fatigue strength. Shape memory alloys (SMAs) are a class of metallic alloys that can recover large strains upon load removal with minimal residual deformations. Besides their ability to recover large deformations, SMAs possess excellent corrosion resistance, good energy dissipation capacity, and high fatigue properties. This study investigates the cyclic behavior of composite materials that consists of a thermoset polymer matrix reinforced with superelastic NiTi SMAs wires. SMA-FRP coupons with three different reinforcement ratios were fabricated using a special-made mold and following a modified hand lay-up technique. The uniaxial tensile tests were conducted under cyclic loading protocols at various stress levels to characterize the behavior of the composite. Low-cycle fatigue properties of SMA-FRPs were also investigated. Microstructural analysis using the scanning electron microscopy (SEM) technique was conducted on fractured surfaces to fully understand the failure mechanism. Results revealed that the SMA-FRP composites can recover relatively high strains upon unloading and exhibit very high failure strains.