Magnetostrictive particulates of Tb0.3Dy0.7Fe2 integrated into carbon fiber reinforced polymer for structural damage monitoring

Smart materials usually are either mounted on surfaces or embedded inside; in this work, we study magnetic properties of smart materials that are integrated into the structure. Magnetostrictive particles of TbxDy1−xFe2 (x ∼ 0.3), commonly known as Terfenol-D, incorporated into carbon fiber reinforced polymers showed a 3000% enhancement in the coercive field compared to the reference pristine bulk Terfenol-D. Torque magnetometer measurements revealed a magnetic anisotropy with twofold symmetry. The lowest applied field at which a reversible torque without hysteresis occurred was ∼5.0 kOe, which yields 5 Oe anisotropic field for a carbon fiber reinforced polymer magnet. This value of the anisotropic field is confirmed using the Miyajima method. Angle dependent coercive field and saturation/remanent magnetization also confirmed the twofold symmetry of magnetization in this system. The high magnetostrictive coefficient, together with the enhanced coercive field, makes Terfenol-D integrated into carbon fiber reinforced polymers serve as an excellent candidate for in situ sensing of damage in various polymer composites under several mechanical loading conditions.