Mechanical dimensioning of smc-components based on the process simulation program express

摘要

The compression moulding of sheet moulding compound (SMC) is a suitable process to produce fibre-reinforced components for serial applications, especially for the automotive industry. Since SMC is increasingly being used for structural applications (front end, bumper beam), mechanical dimensioning will gain in importance to optimise the components design. The mechanical properties of the components are determined to a large extent by the flow pattern. this orients the fibres contained in the material and thus leads to anisotropic mechanical properties. Based on th finite element method the process simulation program EXPRESS has been developed at the Institute of Plastics Processing (IKV), Aachen. The local fibre orientations in the final component can be predicted as a result of the flow behaviour and the mould filling using EXPRESS. The knowledge of the fibre orientations enables to calculate the anisotropic mechanical properties using micro- and macromechanical equations. These material data serve as an input for commercial FEA programs to perform a realistic stiffness analysis. Finally, this study presents a new concept for a failure analysis. In dependency of the SMC-component a dimensioning against the different failure modes 'crack initiation' and 'total fracture' can be chosen. Herefore, a suitable failure criterion in combination with a strategy to determine the relevant failure limits for this criterion as a function of different fibre orientations is proposed.