Influence of the sample shape factor on the dynamic characterization of viscoelastic properties: complex moduli and Poisson's ratio

This study investigates how the sample shape factor influences the dynamic properties characterization of a silicone rubber within the linear viscoelastic regime. The effective elastic properties of elastomers are known to depend on geometry, but the effect of shape factor on the dynamic response has not been systematically characterized. To address this, cylindrical samples with varying geometries are tested under dynamic compression and torsion. The results reveal that both the complex compressive and shear moduli are affected by shape factor, and that this influence varies with frequency. To quantify the influence of shape factor and extract the material’s dynamic properties, a phenomenological correction model is formulated. The model introduces frequency-dependent parameters that account for the geometric effects on the effective moduli. These corrected moduli yield a complex Poisson’s ratio that exhibits a slight frequency dependence, with a decreasing real part and an increasing loss factor. This approach enables both the quantification of geometry-induced effects in dynamic mechanical testing and the extraction of intrinsic material’s viscoelastic properties. • Sample shape influences dynamic moduli in elastomeric compression and torsion. • Correction model quantifies shape effects on complex moduli measurements. • Frequency-dependent model parameters capture viscoelastic–geometric coupling. • Corrected moduli yield physically consistent complex Poisson’s ratio estimates. • Model extracts material dynamic properties from shaped elastomer samples.