Extreme damping in composite materials with a negative stiffness phase.
Composites with negative stiffness inclusions in a viscoelastic matrix are shown to have higher stiffness and mechanical damping tandelta than that of either constituent and exceeding conventional bounds. The causal mechanism is a greater deformation in and near the inclusions than the composite as a whole. Though a block of negative stiffness is unstable, negative stiffness inclusions in a composite can be stabilized by the surrounding matrix. Such inclusions may be made from single domains of ferroelastic material below its phase transition temperature or from prebuckled lumped elements.
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Department of Engineering Physics, Engineering Mechanics Program, University of Wisconsin, 147 ERB, 1500 Engineering Drive, Madison, WI 53705, USA.