Failure modes in open-cell foams with hollow struts

Failure modes in open-cell foams with hollow struts are analyzed. As the walls of the struts become thin, the failure mode of the foam can change from plastic collapse of struts loaded in bending to plastic collapse of struts loaded in direct compression. For very thin strut walls an elastic strut wrinkling failure mode is possible. Expressions for the failure modes are derived, and a failure mode map is presented to clarify when the various modes are expected. The analysis suggests that a hollow strut foam can be substantially stronger than a solid strut foam with the same relative density.