Design, fabrication, and evaluation of negative stiffness elements using SLS

Purpose - Recent research has shown that constrained bistable structures can display negative stiffness behavior and provide extremal vibrational and acoustical absorptive capacity. These bistable structures are therefore compelling candidates for constructing new meta-materials for noise reduction, anechoic coatings, and backing materials for broadband imaging transducers. To date, demonstrations of these capabilities have been primarily theoretical because the geometry of bistable elements is difficult to construct and refine with conventional manufacturing methods and materials. The purpose of this paper is to leverage the geometric design freedoms provided by selective laser sintering (SLS) technology to design and construct constrained bistable structures with negative stiffness behavior. Design/methodology/approach - A meso-scale negative stiffness system is designed and fabricated with SLS technology. The system includes a bistable structure in the form of a pre-compressed/pre-buckled beam. The dynamic transmissibility of the system is measured, and its behavior is compared to the predictions of analytical models. Findings - Experimental results demonstrate that pre-compression and pre-buckling can be used to induce negative stiffness behavior and thereby increase the damping and shift the resonant frequency of an unconstrained beam. Originality/value - The results support the usefulness of SLS and other additive manufacturing technologies for acoustic and dynamic applications. Specifically, the demonstrated advantages of SLS include the ability to rapidly redesign, functionally 2 prototype, and tune physical models for acoustic and dynamic experimentation. Of significant importance is the ability of SLS to enable consolidation of parts that are traditionally separate, thereby reducing vibrational noise in these systems. In this specific application, SLS enables a proof-of-concept comparison of the theoretical and experimental behavior of a meso-scale negative stiffness system. The demonstrated acoustical and vibrational absorptive capacity of these systems is expected to lead to designs for new structures and materials that offer significantly improved energy absorbing capabilities over a broad range of tunable frequencies without compromising structural stiffness.