Investigation of the anisotropy and crushing responses of 3D printed structures

Abstract Additive manufacturing (3D printing) enables lightweight structural components with complex geometries, but its layer-by-layer process introduces anisotropy that reduces strength, limits energy absorption, and complicates modeling. This study investigates the anisotropy and crushing responses of hexachiral auxetic metastructures and crash box configurations fabricated from Polylactic Acid (PLA) using fused deposition modeling (FDM). Mechanical tests, including tensile (ASTM D638), compression (ASTM D695), and drop-weight impact (ASTM D7136), were performed to assess structural performance. Results show that smaller unit cell designs promote more stable collapse and achieve ~10% higher specific energy absorption compared to larger cells, while multi-cell crash boxes significantly outperform single-cell tubes with substantially higher energy absorptions. Printing orientation proved critical: specimens at 0° achieved ~1.6–2 times the tensile strength of 90° ones, with markedly better ductility. These findings highlight the combined role of anisotropy, geometry, and configuration in optimizing crashworthiness.