Negative Stiffness Honeycombs for Recoverable Shock Isolation

Negative stiffness honeycomb materials are comprised of unit cells that exhibit negative stiffness or snap-through-like behavior. Under an external load of small magnitude, a negative stiffness honeycomb exhibits large effective elastic modulus, equivalent to those of other standard honeycomb topologies. When the external load reaches a predetermined threshold, the negative stiffness cells begin to transition from one buckled shape to another, thereby absorbing mechanical energy and mechanically isolating the underlying structure. When the external load is released, the honeycomb returns to its original topology in a fully recoverable way. In this paper, theoretical and experimental behavior of negative stiffness honeycombs is explored, based on FEA modeling and experimental evaluation of laser sintered specimens. Additive manufacturing enables fabrication of these complex honeycombs in regular or conformal patterns. Example applications are also discussed.