Numerical and experimental studies of polyurethane foam under impact loading

Proper predictions of the behaviour of shock absorber materials are of utmost importance in safety assessments for licensing casks for transport and storage of highly active waste. After having identified significant discrepancies between numerical results and the actual response of polyurethane foam limiters subjected to accidental scenarios, a new research project ENREA was established by BAM. A major objective is to enhance and to develop advanced material models intended to simulate limiters under impact loading. They should account for all major factors influencing the load–deformation relationship like temperature, strain rate and specific stress state. The corresponding test program, applicable plasticity models, the overall parameter identification strategy based on local and global optimization techniques as well as experimental and numerical results are presented here in particular for closed cell foams.

Research highlights▸ A systematic compression test series was performed on polyurethane foam cubes in order to quantify the effect of temperature, loading speed, boundary condition and foam density on the flow curve. ▸ Standard material models provided by Abaqus library succeeded to reproduce all three zones of the compression flow curve consisting of an elastic zone followed by an extensive flat plateau and a densification zone as well as dynamic hardening. ▸ A combination of neural networks and local optimization tools was successfully applied to identify all relevant parameters of the foam material model.