Simplified temperature-dependent elasto-viscoplastic deformation and fracture modeling of a talcum-filled PP/PE co-polymer

Abstract

Thermoplastic polymers are widely used in the automotive industry, however, for industrial crash applications there is no generally agreed constitutive theory for modeling large deformations of the rate- and temperature-dependent, non-linear, elasto-viscoplastic material behavior, especially for crash load cases around the glass transition temperature. Nevertheless, for simulating the material response, a prediction model capturing the polymer specific features is required. Therefore, in this work a temperature-dependent material model is presented for a talcum-filled polypropylene/polyethylene co-polymer. The model predicts the rate-dependent deformation and fracture behavior at different ambient temperatures and stress states. It has been implemented in a user material subroutine for an explicit crash code, based on a profound material characterization at −35∘C, 20∘C and 90∘C, covering the load cases uni-axial tension, bi-axial tension, uni-axial compression and shear. For the parameterization and calibration of the model, a parameter identification procedure is presented using a non-linear interpolation method, based on uni-axial tensile tests in between the aforementioned fully characterized ambient temperatures. These additional tests are utilized for obtaining the variation of the most important mechanical properties such as the elastic modulus, the strain hardening, the non-linear plastic Poisson's ratio and the fracture strain over the desired range of ambient temperatures. The model is validated utilizing bi-axial tension tests and glove box flap component punch tests at combinations of ambient temperatures and stress states which have not been used for characterization. The numerical predictions were in good agreement with the experimental observations.