Material Models for Polymers under Crash Loads - Existing LS-DYNA Models and Perspective

Continuum mechanical modelling of structures made from thermoplastic materials under crash loads including large deformations and failure is still challenge in the existing numerical tools for crash simulation. This challenge has two components. One is the fact that the micromechanical nature of the material must be modelled by continuum mechanical models. Continuum models, for pure or for reinforced plastics, will always get either very complex or not very precise if applied to macro molecular materials. The second challenge is the derivation of material parameters for these models by design and instrumentation of adequate experiments. In this paper, an overview on existing material models for thermoplastics applicable on shell elements in LS-DYNA will be given. Specifically, the problem of parameter derivation from experimental data is discussed and examples will be given. Based on a PHD thesis [1] a new approach is described with a special focus on the problem of dilatation under tensile loading. Some perspectives for future developments are described and illustrated by examples.