Stiffness and Damping of Non-Homogeneous Engineered Particles

Abstract This paper presents the dynamic properties of a novel granular material composed of glass bead cores covered by a soft silicone shell. Shear modulus ( G ) and damping ratio ( D ) at very small shear strains (< 2E-5 %) were measured in a resonant column apparatus applying low amplitude random torsional vibrations drawing on advances in resonant column theory for making use of off-resonance data. Relative to the clean beads, the engineered particles exhibit lower G max , higher D 0 and greater stress level sensitivity of G max . The impact on both parameters is greater at small confining stresses where it exceeds an order of magnitude. These effects are reduced with increasing confinement, as the rigid cores start interacting. Engineered particles with <4% m/m silicone reach D 0 values slightly above those observed for sand-rubber mixtures with replacement exceeding 35%. This behavior is attributed to the lossy characteristics of the soft silicone and its uniform distribution through the specimens.