Crashworthiness analysis of structures made from polymers

The numerical simulation of structural parts made from polymers is becoming increasingly important. Although highly sophisticated material laws are available in commercial finite element programs, there are still open questions, especially for crashworthiness analysis. In this paper, we restrict our attention to the explicit solver of LS-DYNA, see [1] and [2]. However, the results are transferable to other solvers without qualification. We present an overview of both classical and new material models for polymers which are used for crash simulations. For this purpose, it is useful to classify polymers in elastomers, foams and thermoplastics. For quasi-static problems, elastomers can be considered as incompressible rubber-like materials. For this class of materials, a large number of models are available in LS-DYNA, e.g. the material laws by Blatz and Ko [3], Mooney and Rivlin [4], [5] and Ogden [6]. In short-time dynamics, however, a strong strain rate dependency of elastomers can be observed. For crash simulations, if the strain rate varies in dependence on the location, this material behavior has also to be taken into account. To consider this behavior, the Ogden material has been generalized by viscous terms. A disadvantage of such a material description is the large number of parameters which has to be identified for each material. Usually, the parameter identification is quiet complex and time consuming. Therefore, we developed a Abstract: