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Model characteristics of a finite element deformable featureless headform with one to four layers of solid elements for the headform skin are studied using both the LS-DYNA3D and FCRASH codes. The models use a viscoelastic material law whose constitutive parameters are established through comparisons of drop test simulations at various impact velocities with the test data. Results indicate that the one-layer model has a significant distinct characteristic from the other (2-to-4-layer) models, thus requiring different parametric values. Similar observation is also noticed in simulating drop tests with one and two layers of solid elements for the headform skin using PAM-CRASH. When using the same parametric values for the viscoelastic material, both the LS-DYNA3D and FCRASH simulations yield the same results under identical impact conditions and, thereby, exhibit a “functional equivalency” between these two codes.

This paper presents a method to obtain improved foam/pillar structural designs to help enhance occupant interior impact protection. Energy absorbing foams are used in this study with their thickness and crush strength being selected as primary design variables for optimization. The response surface techniques in the design of experiment are used in the optimization process. Head impact analyses are conducted by a CAE model with explicit, nonlinear, dynamic finite element code LS-DYNA3D. A baseline model is developed and verified by comparing the simulation results with the experimental data. Based on this model, the anticipated effects of stiffness of the pillar structure and the trim on the Head Injury Criterion (HIC) results are also assessed. The optimization approach in this study provides a comprehensive consideration of the factors which affect the HIC value.