Materials selection of flexible open-cell foams in energy absorption applications

Publication date: 5 January 2018
Source:Materials & Design, Volume 137
Author(s): Evan T. Bird, Anton E. Bowden, Matthew K. Seeley, David T. Fullwood
Foam must be engineered to absorb a particular range of energy in various impact-related applications. Since energy absorption is dependent upon the unique stress-strain response of each foam specimen, it is difficult to quantify analytically; thus, energy absorption cannot be easily compared across materials. Current methods accomplish this using an experimental approach, individually testing foam materials, densities, and geometries to quantify how each influences energy absorption. Such methods require large amounts of time and money to characterize a narrow range of foams. This paper facilitates foam selection by deriving generalized energy absorption material indices. Assuming Euler buckling of columns in the open-cell foam structure, this paper applies equations derived by Maiti et al. to a typical impact scenario wherein the indices are extracted. Using existing Ashby charts, these indices allow polymers to be ranked by the mass and cost each would require as a foamed structure to satisfy specific energy absorption constraints. The presented method allows the energy absorption of a wide range of flexible foams to be compared and relieves the need for extensive factor-specific testing. This method is applied to football helmet foam selection; however, it can be used for many applications where energy absorption is of interest.

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