Experimental and Constitutive Modelling of Viscoelastic Responses in Carbon Black-Filled Natural Rubber Under Cyclic and Relaxation Loading

Elastomeric materials exhibit complex time-dependent behaviour under mechanical loading, necessitating accurate constitutive models for industrial applications. This study investigates the hyperelastic and viscoelastic responses of two carbon black-filled natural rubber compounds (50 ShA and 60 ShA) through cyclic shear/compression tests and stress relaxation experiments. The Arruda-Boyce model captures equilibrium behaviour, while the Bergström-Boyce model predicts transient viscoelasticity without relying on Prony series. Considering the results obtained it can be concluded that quantitative hysteresis analysis shows 7-26% energy dissipation, dependent on hardness and strain rate. Relaxation rates (10^-6-10^-7 s^-1) inversely correlated with hysteresis, validated by FEM simulations. A deviation of <3.5% between experiments and simulations confirms the model's robustness for long-term viscoelastic predictions. This framework enables the efficient design of rubber components (e.g., seismic isolators, seals) requiring prolonged durability under load.