High damping rubber bearings have 10–16% equivalent viscous
damping [24]. Elastomer layers in HDRBs have a much higher
damping capacity compared to those of natural low damping rubbers
used in standard elastomeric isolators with the critical damping
ratios about 2–3% [25]. The damping property of the
elastomeric isolator is improved by adding specific materials like
extra-fine carbon block, oils, or resins and other proprietary fillers
to the natural rubber [26]. With these additives, the elastomeric
isolator will have a higher damping capacity, with a high initial
shear modulus. Because of the materials added to the natural rubber
during vulcanization process, it is difficult to accurately capture
their mechanical properties like stress–strain relationship
and fatigue properties. Many studies showed that although the
hyperelastic material model can simulate the response of natural
low damping rubber, this model cannot accurately capture the
mechanical behavior of high damping rubber materials [6,27,28].