Inclusion connectivity as a design parameter for stiffness and dissipation in MRF-based elastomer composites

The magneto-mechanical response of magnetorheological fluid (MRF)-based elastomer composites is usually tuned through particle fraction and magnetic field intensity. Here we demonstrate that inclusion connectivity is an equally decisive structural parameter governing stiffness, dissipation, and cyclic reversibility. PDMS composites incorporating either continuous double-spiral or discontinuous concentric-ring inclusions were fabricated with fractions of magnetizable particle of 4.2 and 13.3 vol% (fractions of MRF 14.6 and 46 vol%, respectively). Uniaxial compression tests (5% maximum strain, 32 μm·min −1 ) were performed under magnetic fields of 0, 160, and 500 mT. At zero field, replacing a spiral topology with a three-ring discontinuous architecture at 46 vol% MRF decreases the Young's modulus by 20%, evidencing the compliance induced by architectural discontinuity. The nonlinear response is accurately captured by the Mooney-Rivlin model ( R 2 ≈ 1 ). The surface-to-volume ratio of fluid inclusions ( S / V = 2.4–8.3 mm -1 ) emerges as a unifying geometric descriptor controlling stiffness and energy dissipation. Under magnetic activation, discontinuous rings display higher apparent stiffness than spirals due to volumetric confinement of the structured MRF. Cyclic tests reveal geometry-controlled dissipative regimes and a progressive saturation of energy dissipation at high interfacial density, while residual strain decreases with increasing particle fraction and field intensity, and remains lower for discontinuous architectures.