Research conducted in 1993 concentrated on Foamed Plastics. These plastics are used in various locations inside a vehicle to soften contacts. Paddings are usually found on doors, instrument panels, steering wheels and knee bolsters. This makes these materials very important for passive safety analysis. Moreover, crash dummies use foamed plastics to mimic flesh and skin. Finally, foamed plastics are the exclusively used material for crash helmets. These are all topics of interest to the Crashworthiness field.
This topic was most suitable for Henk Helleman because it combined his knowledge of the requirements for crashworthiness with his knowledge of plastics. This knowledge of plastics came from working for the TNO Plastics and Rubber Research Institute from 1985 through 1989. Although specializing in Composite Materials during that period, structural foams were an integral part of his work there.
The one year research project focussed on studying material models
that could be used to predict the material behavior of a diversity of
foamed plastics. An elaborate experimental program, conducted in
cooperation with the TNO Plastics and Rubber Research Institute, which
comprised both static and dynamic testing was part of the study. The
test results were used to validate the material models. Methods were
established for both analytical and numerical analysis of this class of
materials. The study helped to improve the understanding of the behavior
of foams and provided a selection of material models for implementation
in the MADYMO program.
This image shows a Finite Element Model of a rigid spherical body impacting a thick layer of foam. Amongst others, this model was used to analyze and validate the material models. The analyses were conducted with DYNA3D, Pam-Crash and MADYMO.