Optimal design methodology for negative stiffness structures considering lifespan and additive manufacturing uncertainty

Abstract Negative stiffness honeycomb unit cells (NSH-UCs), which employ negative stiffness beams, are capable of absorbing impact energy and are reusable, making them promising for energy-absorbing structural applications. However, limited research has addressed their operational lifespan and manufacturing variability, both of which are critical for practical implementation. This study aims to establish a design optimization framework for NSH-UCs that accounts for both performance metrics such as energy absorption (EA) and operational aspects like reusability and manufacturing-induced uncertainty. To this end, NSH-UC specimens with varying dimensions were fabricated using fused filament fabrication with PLA/PHA filaments, and their mechanical behavior was evaluated through quasi-static and cyclic compression tests. A surrogate-based optimization method was then applied to improve EA and extend operational lifespan, while considering geometric and material uncertainties inherent to the additive manufacturing process. The proposed framework led to a significant improvement in EA and end-of-life performance compared to the initial design, despite only modest changes in specific EA. These findings demonstrate the feasibility of incorporating performance, reliability, and manufacturing variability into early-stage design, highlighting the framework’s potential for structural health monitoring and prognostics and health management applications.