Elastic buckling of the cell walls is the mode of failure for elastomeric materials,[30] ductile materials fail due to plastic yielding, and brittle crushing is the mode of failure when the solid is brittle.[29][30] The elastic buckling stress is proportional to the relative density cubed, plastic collapse stress is proportional to relative density squared, and brittle crushing stress is proportional to relative density squared.[29][30] Following the critical stress and failure of the material, a plateau stress is observed in the material, in which increases in strain are observed while the stress of the honeycomb remains roughly constant.[30] Once a certain strain is reached, the material will begin to undergo densification as further compression pushes the cell walls together.[30]