Models to Characterize Multiple Time Scale Behavior in Polyurethane Foam

摘要

Polyurethane foam is a nonlinear and time dependent material that exhibits both long and short-term memory. The challenge is to design experiments that generate data sets with sufficient information to allow the identification of models that can predict multiple time-scale behavior. In this investigation nonlinear viscoelastic models are proposed and fitted to results from uniaxial compression experiments. The material stress response to the imposed compression is modeled as the sum of a nonlinear elastic component and a linear hereditary-type viscoelastic component. The viscoelastic kernel for the hereditary model is taken to be a sum of exponential terms. The compression experiments are performed at several constant strain rates, and a nonlinear viscoelastic model is fitted to each experimental result. The model structure is adapted with an aim to capture the material behavior at multiple time scales simultaneously. The viscoelastic model structure and fitted time constants are studied with respect to the experimental time-scales.