Numerical and experimental investigation of 3D printed tunable stiffness metamaterial with real-time response using digital light processing technology

A tunable mechanical metamaterial is a type that can be altered or manipulated to change its physical properties in various situations. This study introduces a novel type of metamaterial, hydro-tunable metamaterials (HTMs), which can be dynamically adjusted in real-time by filling or draining it with water. The development of HTMs has significant implications for various fields, including mechanical engineering, biomedical applications, and energy absorption. The study involves designing and manufacturing HTMs using a Digital Light Processing (DLP) 3D printing process. The design process involves modifying an initial basic auxetic structure to create a closed and sealed structure accommodating fluid. The printed samples are then characterized using mechanical testing and finite element analysis (FEA). Experiments and simulations have found that a sample containing water behaves differently from a sample without water, resulting in an increase in stiffness. This difference can be leveraged to modify the stiffness and strength of the structure. This phenomenon is attributed to the incompressibility of water within the structure. Water exerts a hydrostatic pressure on the auxetic material, resulting in increased stiffness and resistance to compression. This technique highlights the potential of HTMs to be dynamically adjusted in real-time, leading to enhanced energy absorption and improved performance. An additional FEA was conducted to examine the impact of water pressure on the mechanical behavior of the structure. The results indicate that applying pressure or temperature to the water can significantly enhance the mechanical properties of the water-filled sample.