Creating static mechanical nonreciprocity by introducing through-thickness gaps

• Static mechanical nonreciprocity is achieved by introducing through-thickness gaps. • Contact nonlinearity due to gap behavior governs nonreciprocal response. • Gap-based design exhibits static nonreciprocity across different loading conditions. • The degree of mechanical nonreciprocity depends on the gap dimension and orientation. Mechanical nonreciprocity has emerged as a promising characteristic in the design of next-generation mechanical systems due to its potential to enable direction-dependent control. However, breaking the fundamental principle of mechanical reciprocity in static systems remains a significant challenge. This paper proposes a simple yet general approach to achieve static mechanical nonreciprocity by introducing through-thickness gaps. Three silicone rubber specimens are fabricated and experimentally tested, and a finite element model is developed and validated to confirm the effectiveness of the proposed system in achieving static mechanical nonreciprocity. Both experimental observations and numerical simulations reveal that contact nonlinearity induced by direction-dependent gap opening and closure behaviors is responsible for the nonreciprocal mechanical response. Results also demonstrate that mechanical nonreciprocity achieved by introducing gaps is robust across different loading conditions and can be programmed by modifying gap parameters such as gap length, tilt angle, and friction coefficient. The findings from this study provide a basis to achieve static mechanical nonreciprocity for a wide range of engineering applications.