LARGE-STRAIN 3D-ANALYSIS OF FIBER-REINFORCED COMPOSITES USING REBAR ELEMENTS - HYPERELASTIC FORMULATIONS FOR CORDS

The well-known finite element representation of reinforcing bars by me ans of overlay (''rebar'') elements is recast in the context of finite strain analyses of cord-reinforced composite materials. The variation al formulation including the linearized forms is presented on the basi s of hyperelasticity. Three material laws including two variants of th e Neo-Hooekean model and the quadratic logarithmic model are investiga ted. An explicit formulation for uniaxial stress states is given for t he Neo-Hooekean model. A comparative evaluation with regards to comput ational efficiency and physical plausibility shows that the logarithmi c model is optimally suited for this class of problems and for moderat ely large strains. The rebar-element concept in conjunction with an in compressible finite element formulation for the representation of a ru bber matrix material is applied to comparative finite strain FE-analys es of a cord-reinforced rubber sandwich panel, with different hyperela stic models used for modelling of the ply material.