Magneto-mechanical behavior in polyurethane foams containing oriented FeCo microparticles: A competition between bending and stretching effects

摘要

Soft magneto-active composites are of particular interest in areas of biomedical applications, wearable sensors and soft robotic. In this context, this work presents a deep study of how the incorporation of Fe₇₀Co₃₀ microparticles into foam polyurethane composites affects its magnetostrictive response. The composites were fabricated in both foam and foam film-like structures, resulting from free or confined expansion, respectively, and with varying percentages and orientations of magnetic microparticles. All of the fabricated foams have been optically, magnetically, mechanically and thermally characterized. The inclusion of magnetic microparticles had negligible impact on thermal stability and degradation behavior. In contrast, mechanical and magnetic properties were highly sensitive to both the concentration and alignment of the particles. Magnetostriction behavior revealed a competition between bending and stretching mechanisms, governed by the composite’s stiffness. At lower particle contents (≤40 wt%), bending dominated, producing negative magnetostriction values. As particle content increased (>40 wt%), the material stiffened, suppressing bending and allowing stretching to prevail, resulting in positive magnetostriction, particularly evident in foam-film composites. These findings demonstrate the tunability of the magnetic response in soft composites through structural and compositional control. • Magneto-active foams with Fe₇₀Co₃₀ microparticles were fabricated and characterized. • Free vs. confined expansion produced distinct foam and foam-film composite structures. • Magnetostrictive response was tunable by particle concentration and alignment. • Magnetostriction governed by bending-stretching balance, strongly affected by composite stiffness.