Amherst. Massachusetts 01 003Two-dimensional indenters (flat plate and cylinder) were used to compress rectangular and trapezoidal foam energy absorbers as a function of polymer, foam density, and thickness. An increased deformation volume formed when the indenter contact area was less than the foam absorber area, resulting in both increased energy absorption and stress transmitted to the indenter (i.e., "load spreading"). The deformation volume was trapezoidal, not prismatic, and was characterized by the indenter geometry, dlmensions, and foam thickness. Conservative energy absorber design can be achieved by using "energy absorption diagrams" that account for the indenter (i.e., product) and absorber geometry and degree of load spreading.
MTRODUCTIONhe use of energy absorbers in packaging is a T necessity, whether it is to protect a product during shipping, a passenger in an automobile, or the head of a cyclist. Polymer foams are ubiquitous as packaging materials because they are effective, inexpensive energy absorbers that can be easily shaped to conform to complex product geometries. Current design practice relies on "cushioning curves," which are strictly applicable only to objects with planar contact areas impacting foam cushions of equal or lesser area (1, 2). When combined with "drop testing," however, this method succeeds in p r e tecting most packages, but it is questionable whether the polymer foam, thickness, and geometry are optimum (3).Regardless, future packaging trends are expected to demand decreased shipping and warehouse costs bYg package volume without loss of protec-
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