Design and structural analysis of unique lattice structure with negative poisson's ratio

The positive Poisson's ratio is one of the common and characteristic features of most materials. Materials with a negative Poisson's ratio are called auxetic materials. Materials with auxetic behavior are rare in nature. Auxetic materials, unlike normal materials, contract in compression and expand in tension, due to the negative Poisson's ratios. Materials with negative Poisson's ratio have energy absorbency, fracture strength, thermal shock resistance, etc. properties are expected to be high. For this reason, it is planned to be used in many fields such as biomedicine, defense industry and aviation. Structural analysis was run according to the thickness and angle parameters of the unique lattice structure with negative Poisson's ratio determined in the first part of the study. Poisson's ratios of 15 different lattice structures in total were calculated according to 3 different thicknesses and 5 different angles. The lowest Poisson's ratio was found to be -0.70. Then, geometric improvements were made with two different methods by keeping the mass of the lattice structure with the lowest Poisson's ratio constant and the improvements were modeled numerically. As a result of the applied improvements, finite element analysis was performed again and the Poisson's ratios of the lattice structures with two different methods were calculated as -0.78 and -0.73. Finally, in order to compare the mechanical properties of three different lattice structures, modal, static structural and explicit dynamics analyzes were carried out using the finite element method. According to the results of the analysis made after the new numerical model was applied, it was observed that there was a significant decrease in the stresses on the lattice structure. As a result; It has been concluded that the stresses of auxetic geometries with different lattices can be reduced by mathematical models developed with special formulas.