DEVELOPMENT OF AUXETIC STRUCTURES FOR IMPACT RESISTANT APPLICATIONS

Abstract

Auxetic structures are structures architected to enable them to have a negative Poisson ratio (NPR) under static and dynamic loading. In such structures when compressive load is applied, there will a reduction in their lateral width due to the crumpling of struts. Here, in this work, an auxetic structure has been modelled inspired from a frog skeleton, i.e., by replicating the vertical section of frog anatomical skeleton and designing the struts so that it will crumple under compressive loading. Further, in this work, another structure inspired from S structure of another authors’ work, was designed in three dimensions to understand the crumpling mechanism and corresponding auxetic behaviour. Further, in both structures, three dimensional unit cell was modelled based on the three dimensional structure from literatures, with the struts being designed aligning to frog skeleton and S structure of respective auxetics. The two structures are simulated for auxetic behaviour under quasi static compression test with material as PLA based resin and compared with the results from the literature. Further, physical structures were built using SLA and mechanical compression testing was conducted and the experimental results of the three structures were compared. Finally, based on the inference from Load Displacement relationship and Specific Energy Absorption vs Displacement relationship of the three structures, suitable impact applications in the strain rates ranging from 5 x 10^-4 s^-1 to 15000 s^-1 were discussed and one application i.e., crash tubes was modelled using auxetic structures developed, simulated and compared with the conventional structure.