Prediction of the tensile impact behavior of injection molded samples from quasi-static data

A methodology for predicting the mechanical behavior of injection molded semicrystalline thermoplastics, within a wide range of strain rates and temperatures, is proposed in this work. This method is based on data obtained at isothermal low velocity tensile tests and on a phenomenological constitutive equation that describes the stress as a function of independent and multiplicative terms of the strain, strain rate and temperature. The effect of the processing conditions on the coefficients of this equation is considered by evaluating their dependence on thermo-mechanical indices, calculated from melt flow simulations. Using a finite element code that has this equation built-in, it is possible to predict the mechanical behavior of samples injected with different molding conditions. The extrapolation of the impact properties requires the consideration of the dependence of the material consistency on the strain rate, which is affected by the sample skin-core structure. So, any constitutive equation used to describe the mechanical behavior of the injection molded samples must consider the distinct contributions of the main microstructural layers.