Superelastic Shape Memory Alloy Fiber-Reinforced Polymer Composites

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 exhibits brittle failure, low toughness, limited fatigue strength, and relatively low ultimate tensile strains. 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 explores the use of superelastic SMA fibers to reinforce a thermoset polymer matrix to produce a polymer composite with enhanced mechanical properties. Nickel-Titanium wires with a diameter of 495 micrometer are used as fibers. SMA coupons with different reinforcement ratios are fabricated using a special-made mold and following a modified hand lay-up technique. The uniaxial tensile tests are conducted under cyclic loading protocols. The results of the tests are assessed in terms of ultimate strength, ultimate strain, residual strain, and failure modes of the composites.