Characteristics of carbon fiber reinforced polymers embedded with magnetostrictive Fe–Co wires at room and high temperatures

Composite materials, such as carbon fiber-reinforced polymer (CFRP), glass fiber reinforced polymer, and fiber-reinforced metal matrix, have considerable application potential in the aerospace industry as structural components require remarkable mechanical properties such as high strength, high elasticity, and lightweight. Structural health monitoring (SHM) is required to ensure the safe use of these structural components during service. Magnetostrictive materials can convert mechanical energy into magnetic energy, and are considered desirable candidates to be used in SHM sensors owing to their large magnetostriction, long life, and low cost. In this study, we developed the composite materials comprising CFRPs with embedded Fe–Co wires and evaluated their magnetic and magnetostrictive characteristics using the vibrating sample magnetometer and strain gauge, respectively. Furthermore, the magnetostriction was analyzed using the nonlinear constitutive equations for magnetostrictive materials. It was shown that the largest piezomagnetic constant of 0.281 × 10⁻⁹ m/A is obtained for the CFRP with Fe–Co wires of 0.05 mm diameter. Microstructural observation of the Fe–Co wires with different diameters was performed to investigate the differences in grain structure and residual strain because the diameter of the Fe–Co wire affects the magnetostrictive response. Finally, the magnetostrictive characteristic was measured at high temperatures. The piezomagnetic constant at 373 K was about the same as the value obtained at room temperature. These results will contribute to developing the high-performance CFRP/Fe–Co wire composites that can be used in SHM sensors operating in high-temperature environments.