Behavior of auxetic structures under compression and impact forces

Abstract

In recent years, various auxetic material structures have been designed and fabricated for diverse applications that utilize normal materials that follow Hooke’s law but still show the properties of negative Poisson’s ratios (NPR). One potential application is body protection pads that are comfortable to wear and effective in protecting body parts by reducing impact force and preventing injuries in high-risk individuals such as elderly people, industrial workers, law enforcement and military personnel, and athletes. This paper reports an integrated theoretical, computational, and experimental investigation conducted for typical auxetic materials that exhibit NPR properties. Parametric 3D CAD models of auxetic structures such as re-entrant hexagonal cells and arrowheads were developed. Then, key structural characteristics of protection pads were evaluated through static analyses of FEA models. Finally, impact analyses were conducted through dynamic simulations of FEA models to validate the results obtained from the static analyses. Efforts were also made to relate the individual and/or combined effect of auxetic structures and materials to the overall stiffness and shock-absorption performance of the protection pads. An advanced additive manufacturing (3D printing) technique was used to build prototypes of the auxetic structures. Three different materials typically used for fused deposition modeling technology, namely polylactic acid (PLA) and thermoplastic polyurethane material (NinjaFlex® and SemiFlex®), were used for different stiffness and shock-absorption properties. The 3D printed prototypes were then tested and the results were compared to the computational predictions. The results showed that the auxetic material could be effective in reducing the shock forces. Each structure and material combination demonstrated unique structural properties such as stiffness, Poisson’s ratio, and efficiency in shock absorption. Auxetic structures showed better shock absorption performance than non-auxetic ones. The mechanism for ideal input force distribution or shunting could be suggested for designing protectors using various shapes, thicknesses, and materials of auxetic materials to reduce the risk of injury.

Dome-Shape Auxetic Cellular Metamaterials: Manufacturing, Modeling, and Testing

“…In the arrow-head topology ν a grows from a negative value to zero with increasing strain (Yang et al, 2018). The arrow-head and re-entrant topology has higher energy dissipation than the hexagonal lattice due to the negative in-plane ν a .…”

Vibration and Sound Transmission Performance of Sandwich Panels with Uniform and Gradient Auxetic Double Arrowhead Honeycomb Cores

“…en, sandwich structures with combined conventional and re-entrant hexagonal metamaterials were investigated based on various characteristics, such as the specified objective deformations [28]; the strength and failure properties under bending, compressive and impact loads [29][30][31]; the dynamic behavior [32,33]; and the sound transmission performance [23,34]. Moreover, functionally gradient auxetic metamaterials based on other topologies, such as double arrowhead honeycombs (DAHs), have been developed [35][36][37][38] in recent years.…”

A New Mechanism for Soft Landing in Robotic Space Exploration

“…Finally, the effect of the soil itself is generally nontrivial to model [17][18][19][20]; it can be simulated using numerical methods [17] or experimentally. The physics of impact and energy dissipation during collisions and landing have been studied from a structural point of view [21][22][23], from a dynamics perspective [1,2,10,16,[23][24][25], and as a mission-planning problem [11,26].…”

“…Generally, landing systems for space probes are designed to be used only once [21][22][23]26]; an interesting example is that of Saeki, who proposed a landing gear based on a spring that, when fully compressed, is released, thus dissipating the landing energy [33]. On the other hand, the need for reusable landing systems can be found in some proposals, e.g., vertical take-off and landing systems (VTOL) vehicles [34], suspension system for rovers [24], and several others [25,35].…”