Talcum Particle Reinforced Thermoplastics - Part II: Material Modeling and Simulation

Thermoplastic polymers reinforced with mineral (talc) particles typically display an anisotropic mechanical behavior that results from the preceding manufacturing process (e.g. injection moulding) with a distinctive direction of melt flow [1]. Moreover, plastic dilatancy under tensile loading is observed which can be ascribed to particle-matrix debonding and subsequent void growth; see e.g. [2]. Based on the experimental study presented in [1], the present work deals with the development and implementation of a macroscopic constitutive model for talc particle reinforced polymers. Key incredients of the model are an anisotropic pressure-dependent yield criterion that contains the porosity due to void growth as a damage parameter, along with a rate and temperature dependent associated flow rule. The model well captures the experimentally observed anisotropy of the yield strength as well as the (likewise anisotropic) plastic dilatancy under tension. It has been implemented as a user-defined material model in LS-Dyna, and aspects of the numerical treatment will also be discussed in the presentation. Application to components subjected to crash loading serve to validate the constitutive model. Therefore, anisotropy directions and positions of weld lines as predicted from mould filling simulations [1] are accounted for via a mapping strategy.