The Villari effect of magnetostrictive materials, a change in magnetization due to an applied stress, is used for sensor/energy harvesting applications. In this work, magnetostrictive ber/polymer composites are fabricated for the rst time by embedding strong textured Fe-Co bers in an epoxy matrix, and their stress-rate dependent output voltage characteristics are investigated. Compression tests are rst conducted to measure the output voltage of a sample. A simple magnetomechanical coupling model of the magnetostrictive ber/polymer composite is then established. The output voltage is predicted, and domain wall dynamics is discussed in relation to the macroscopic inverse magnetostrictive response (known as the Villari effect). The results show that the output voltage density of this novel Fe-Co ber/polymer composite dramatically increases with increasing stress-rate and becomes larger than that of Fe-Ga alloy. Our work represents an important step forward in the development of magnetostrictive sensor and energy harvesting materials.

The inverse magnetostrictive effect is an effective property for energy harvesting; the material needs to have large magnetostriction and ease of mass production. Fe–Co alloys being magnetostrictive materials have favorable characteristics which are high strength, ductility, and excellent workability, allowing easy fabrication of Fe–Co alloy fibers. In this study, we fabricated magnetostrictive polymer composites, in which Fe–Co fibers were woven into polyester fabric, and discussed their sensor performance. Compression and bending tests were carried out to measure the magnetic flux density change, and the effects of magnetization, bias magnetic field, and the location of the fibers on the performance were discussed. It was shown that magnetic flux density change due to compression and bending is related to the magnetization of the Fe–Co fiber and the bias magnetic field. The magnetic flux density change of Fe–Co fiber reinforced plastics was larger than that of the plastics with Terfenol-D particles.

Carbon fiber reinforced plastic (CFRP) is an excellent choice in the areas where weight reduction is important and multi-functionalization of CFRP, especially by adding sensor capabilities, is a promising approach to realize lightweight battery-free devices in structural health monitoring (SHM). In this study, we fabricated hybrid CFRP with Fe-Co fibers and evaluated the inverse magnetostrictive response characteristics. It was shown that the measured magnetic flux density of the CFRP fluctuates in response to cyclic bending load. It was also revealed that our Fe-Co fiber inserted CFRP has damage self-sensing ability. In addition, it seems that the optimization of design and more experimental and numerical investigation improves the capability of the hybrid CFRP with Fe-Co fiber as sensor composite materials.

Wearable energy harvesting devices attract attention as the devices provide electrical power without inhibiting user mobility and independence. While the piezoelectric materials integrated shoes have been considered as wearable energy harvesting devices for a long time, they can lose their energy harvesting performance after being used several times due to their brittleness. In this study, we focused on Fe–Co magnetostrictive materials and fabricated Fe–Co magnetostrictive fiber integrated shoes. We revealed that Fe–Co magnetostrictive fiber integrated shoes are capable of generating 1.2 µJ from 1000 steps of usual walking by the Villari (inverse magnetostrictive) effect. It seems that the output energy is dependent on user habit on ambulation, not on their weight. From both a mechanical and functional point of view, Fe–Co magnetostrictive fiber integrated shoes demonstrated stable energy harvesting performance after being used many times. It is likely that Fe–Co magnetostrictive fiber integrated shoes are available as sustainable and wearable energy harvesting devices.