Magnetic field induced toughening mechanisms in isotropic and anisotropic soft magnetoactive elastomers

Abstract

Soft magnetoactive elastomers (sMAEs) are promising multifunctional composites obtained by embedding soft-magnetic particles into an elastomer matrix. Under external magnetic fields, these composites exhibit tunability in mechanical and rheological properties, including stiffness modulation and controllable deformation. Despite growing interest in their magneto-mechanical capabilities, the fracture behavior of sMAEs under magnetic fields remains entirely unexplored. Here, we present the first comprehensive experimental characterization of the fracture toughness and underlying fracture mechanisms in sMAEs subjected to magnetic fields. The study includes different volume fractions of particles, with particles arranged both randomly and aligned, parallel and perpendicular to the loading direction. Experimental results show that in the presence of a magnetic field, fracture toughness increases by 42% for anisotropic sMAEs and 23% for isotropic sMAEs, compared to their unmagnetized states. With the aid of the load-stretch curves, spatial distribution of strain from Digital Image Correlation (DIC), and optical microscopy images of the test specimens, we identify two key mechanisms driving the observed toughening: bulk magneto-mechanical induced stiffening and/or local magneto-mechanical coupling near the crack tip that delays catastrophic failure. This work bridges a critical knowledge gap and expands the design space for durable and adaptive multifunctional magneto-responsive composites.