Damping nonlinearity in agarose hydrogels under relative humidity: balancing network stiffness and energy dissipation

Sustainable, biodegradable elastomers are needed to replace fossil-based alternatives and reduce the environmental impact of traditional vibration damping materials. We investigate agarose-based hydrogels as eco-friendly vibration absorbers, examining the combined effects of polymer concentration (1-7 wt%), relative humidity (55-98%), and mechanical pre-stress on their dynamic mechanical properties. Frequency-dependent viscoelastic and vibration transmissibility tests, supported by Gaussian Process Regression (GPR), reveal that increasing agarose concentration enhances the storage modulus (E') by over an order of magnitude, reaching[~] 5 MPa depending on humidity and applied prestress. Remarkably, the damping efficiency--characterised by the loss factor (tan(d))--exhibits a highly non-monotonic trend. Maximum energy dissipation is observed at intermediate network densities, with tan(d) up to 0.21 and a loss modulus of[~] 515 kPa at 5 w% and 75% relative humidity, comparable to synthetic elastomers. GPR analysis shows that prestress controls nonlinear stiffening and transmissibility resonance behavior, while shifting peak damping from 5 wt% to 1 wt% agarose as prestress increases. These findings underscore the mechanical tunability and sustainability of agarose hydrogels, providing potential design guidance for biodegradable vibration mitigation materials.