A mesomechanics parametric finite element study of damage growth and coalescence in polymers using an Elastoviscoelastic-Viscoplastic internal state variable model

A split-level factorial design of experiments (DOE) parametric study using a two-dimensional mesoscale Finite Element Analysis (FEA) was executed to elicit the most essential aspects pertaining to void/crack growth and void/crack coalescence in polymers above the glass transition temperature. The FEA was coupled to a physically based, strain rate and temperature dependent, elastoviscoelastic-viscoplastic internal state variable polymer model that was calibrated to physical experiments. The DOE method examined the relative influences of seven independent parameters related to mechanics (stress state, strain rate, and temperature) and materials science (polymer blend, number of initial defects, defect type, and initial microporosity-also called the subscale free volume) with respect to both void/crack growth and void/crack coalescence in polymers. The results of the DOE algorithm clearly illustrated that the stress state and applied strain rate were the most critical factors affecting void/crack growth. For void/crack coalescence, the stress state and number of defects were the crucial parameters. The conclusions of this study gives insight for the development of a macroscale damage model for polymers.