Finite Element Modeling of Structural Foam and Head Impact Interaction with Vehicle Upper Interior

This paper first describes an experimental analytical approach and numerical procedures used to establish crushable foam material constants needed in finite element (FE) analysis. Dynamic compressive stress-strain data of a 2 pcf Dytherm foam, provided by ARCO Chemical, is used to determine the material parameters which appears in the foam constitutive equation. A finite element model simulating a 15 mph spherical headform impact with a foam sample 6 in. x 6 in. x 1 in. fixed against a rigid plate is developed. The predicted force-deflection characteristic is validated against test data to characterize the initial loading and final unloading stiffnesses of the foam during impact.

Finite element modeling and analysis of 15 mph spherical headform impact with component sections of upper interior structures of a passenger compartment is presented. The FE model validations are carried out through very good correlations of the predicted headform responses to those obtained from laboratory tests of spherical headform impact with vehicle components in unpadded and padded configurations. Such techniques can demonstrate the capacity of a well-defined model to help predict headform responses and the effect of adding foam padding and structural design changes on so called Head Injury Criteria (HIC). It is concluded in this paper that the application of finite element technique to head impact design issues has great potential for understanding structural design attributes and their effect on HIC measurements.