Time-dependent deformation of closed-cell PVC foam

Abstract

Time-dependent deformation behaviors of closed-cell polyvinyl chloride (PVC) foams (113 and 176 kg/m 3 foam densities) under tension were studied at various strain rates (10—5—10—1 s —1). It was found that the tensile properties including modulus, yield strength, ultimate tensile strength, and fracture strain were time dependent. Modulus and strength increased with increasing strain rate, while fracture strain decreased with increasing strain rate. Strain recoveries after unloading were also found to be time dependent. At low strain rates, more permanent deformations were observed, and the strain recoveries were less than those at high strain rates. Cell-wall buckling and crazing were dominant mechanisms at low strain rates, which enhanced the time-dependent strain and reduced the foam strength. However, the time-dependent strains decreased, and the failure mechanism became brittle fracture at higher strain rates.