Cohesive Contact Modeling in Thermoforming Simulations of Metal-CRFP-Metal Sandwich Sheets

A novel carbon fiber reinforced metal laminate based on thermoplastic polymer is investigated in the project LEIKA. For the safeguarding of the production of the parts made of this material, coupled thermo-mechanical simulations have to be carried out. Experiments show a large relative sliding, separation and re-sticking behavior between layers during the forming of the heated sheets. Hence, each layer of the laminate needs to be modeled as an individual shell in order to represent the different forming behavior. In this work we concentrate on the complex interlayer contact behavior. As the built-in contact models in LS-DYNA are not capable of modeling the relevant physical aspects, an improved user defined contact model has been developed in the LS-DYNA user defined friction routine. A new temperature dependent traction-separation behavior has been implemented based on a bi-functional cohesive definition with damage (RCCM). For the post separation state the model has been extended with a pressure dependent re-sticking and adhesive re-healing. For the tangential behavior either a temperature dependent Coulomb friction or a hydrodynamic friction law can be used. The developed contact model has been verified and applied to test parts. For the latter case the simulation results show good agreement with experimental results provided by partners.