A viscoelastic damage model for hysteresis in PVC H100 foam under cyclic loading

Abstract

A phenomenological constitutive model for Divinycell PVC H100 foam undergoing crushing and hysteresis under cyclic compression loading was developed. Cyclic compression tests were done with strain amplitudes from 0.02 to 0.1 and strain rates ranging from 0.0005 s−1 to 5 s−1. Within this test range, the PVC H100 foam exhibited strain rate-dependency, damage, and hysteresis. Damage that occurred in the foam after yielding followed the pattern of Mullins damage, i.e. the damage was essentially fixed at a given strain amplitude, and more damage occurred with increasing the strain amplitude. A constitutive model based on damage initiation and viscoelastic damage evolution of the foam was proposed. A simple damage initiation criterion based on critical compressive strain was proposed to separate undamaged and damaged foam response. A standard model, an elastic spring in parallel with Maxwell element, was used to describe viscoelastic behavior before and after damage. Before damage, spring and damper constants were evaluated from the test data. The rate-dependent undamaged stress–strain response and flow stress were found to be in good agreement with the test results. After damage, the spring and dashpot resistances were found to be the functions of strain amplitude and flow stress, which depended on strain rate. These viscoelastic damage functions were shown to give very good predictions of the hysteresis and strain rate-dependent behavior of the foam after damage.