Experimental study on characterizing damage behavior of thermoplastics

Loading–unloading uniaxial tension tests are performed with a talc-filled and impact-modified polypropylene material. The damage parameters are calculated following two documented methods. One of these methods is based on the loading and unloading moduli, and the other is based on the volume strain. Two different approaches for obtaining the unloading modulus are studied and compared. Further tests are conducted to investigate the influence of test procedure and loading speed on the damage parameters. The SAMP-1 material model in the FE software LS-DYNA is employed with those calculated damage parameters to simulate the loading–unloading uniaxial tension tests. To validate the material model and to evaluate the applicability of the different damage characterization methods, loading–unloading 3-point bending tests are carried out and the corresponding simulation is also conducted. It is shown that the simulation with the damage parameter based on the unloading modulus calculated using the energy equivalent method is of better overall correlation with the test results.