Effect of Loading Geometry on the Stress-Strain Behavior of Plastic Foams in Cushioning Design Study 710040

The dependence of the compressive stress-strain behavior of plastic foams on the loading geometry and its significance in relation to the cushioning design study for automobile safety is explored. Experimental load-deflection responses obtained under dynamic (impact) and static conditions using loading objects of various different geometry are analyzed.

A strong interaction between the loading geometry and the material response existed. It was found that the stress-strain behavior of plastic foams varied, whether under static or dynamic conditions, with the loading geometry. The linear load-deflection response observed in the case of hemi-spherical loading differed from that of the convoluted faceform loading, while the response for the flat plate compression deviated from both. The importance of this loading geometry effect in connection with the development of an effective crash padding system for automobile vehicles is discussed in detail in terms of the peak deceleration and the maximum average stress produced upon impact on the plastic foams. The analysis of the test results leads to the conclusion that a realistic evaluation of the cushioning system should incorporate into it this geometry effect by the selection of an appropriate loading geometry. The dependence of the stress-strain behavior on foam density, foam thickness, and the nature of the base polymer from which the foam is expanded is also briefly discussed in this paper.