Material Model Development of an Energy Absorbing Foam for Occupant Safety 2009-26-0088
Different Original Equipment Manufacturers (OEMs) use different Finite Element (FE) codes to perform crash analyses. Primary explicit codes widely used are LS-DYNA, PAM-CRASH and RADIOSS. These codes help rapid evaluation of vehicle design in the preliminary phase, eliminating the need for cumbersome design changes post-physical validation trials. This is more so critical for crash and safety aspects of design.
A variety of Energy Absorbing (EA) foams are offered to OEMs to meet the EA performance requirements. Also the FE codes offer a variety of standard material models to the analyst to choose from. The choice of material model is governed by factors such as type of foam under consideration, simplicity of modeling, available material test data, performance objectives, etc. The development of a validated material model is hence a complex task. This paper deals with development and validation of material models of IMPAXX for the FE codes RADIOSS and PAM-CRASH.
Typical criteria of validation of such a material models are correlation of test and predicted values of peak force, displacements, time and shape factor. Parameters affecting the EA performance are found to be dependent on IMPAXX Foam size and shape, as well as boundary conditions viz. backing, impactor and impact velocities. The material model validation involves correlation studies on the above factors using pelvic impactor and free motion head form.
This paper presents the material characterization requirements for material model generation and component level testing for validation, using Design of Experiment (DOE) procedures for material model development and sensitivity studies. The validated FE material model is then integrated into impact analyses such as head and pelvic impact.