Forming Simulations in LS-DYNA using the Material Law 249

The reduction of car fuel consumption by proposing lightweight structural and non-structural parts is one of the main strategic goals of Faurecia Automotive Exteriors (FAE). Composites as fiber reinforced plastic materials (FRP) provide an important lightweight potential but increase the material complexity due to their anisotropy. The latter is induced or, depending on the fiber structure, at least reinforced during processing and impacts largely the product performances. At FAE, the product performances as crash behavior are evaluated using LS-Dyna. For guaranteeing continuity between models and for reducing the translation effort between different codes, we investigate using LS-Dyna also for the simulation of FRP part forming. A successful forming simulation implies the use of a predictive material law with realistic material parameters. Up to now we used material law Mat-34 in the preforming process simulation. The newly developed Mat-249 comes to challenge the former one. The framework was a collaborative project with the Fraunhofer ICT [1]. Additionally to solving some numerical issues due to material instabilities, a better prediction of wrinkling can be confirmed. Some material parameters can be determined directly with the outcome of trials. For non-physical ones as the bending stiffness in the studied material laws, a reverse engineering approach is necessary. This implies to create models corresponding to the trials and to do parameter optimizations using LS-Opt. Having determined the corresponding material parameters, Mat-249 allowed optimizing the forming kinematics in the aforementioned project. A second domain of application for this new material law is the thermoforming process, used at Faurecia in the School Mold project and in the Composite one shot process for visible parts [2]. [1] F. Henning et al., Cost-efficient Preforming as leading process step to achieve a holistic and profitable RTM product development, 1st International Composites Congress (ICC)-2015 [2] G. Chambon, Composite one shot process for visible parts, JEC World 2016, Paris