| Abstract: | Creep experiments carried out on transparent and translucent polymers permit the observation of irreversible material damage in the form of crazes or microcracks. The formation of such damage is strongly dependent on the applied stress, temperature and environmental conditions. The first appearance of observable material damage seems to be explicable by an energy criterion. The energy supplied by the external load can be divided into conserved and dissipated parts, each of them causing volume (isotropic) and shape (deviatoric) changes. The different parts of the energy can be computed if the creep-compliance is approximated by a Prony-Dirichlet series with a finite number of terms. Computations carried out for experiments with air as the environmental medium under isothermal conditions show the dependence between the appearance of first visible material damage (crazes or microcracks) and the conserved energy. |
