Novel geometric functionally graded auxetic double arrowhead lattice structures design: Tailored unit cell angles for superior energy absorption

Due to the importance of energy absorption in various industries, including aerospace, automotive, and marine, lightweight energy absorbers such as auxetic structures under in-plane loading have attracted significant attention. This study introduces and systematically investigates novel Geometric Functionally Graded (GFG) auxetic double arrowhead lattice structures, where performance enhancement is achieved by strategically varying the constituent unit cell angles along the loading direction—a distinct approach from conventional thickness-grading. The aim encompasses the design, fabrication (via Fused Filament Fabrication), and quasi-static compressive testing of thirteen distinct lattice configurations, including seven uniform and six GFG designs, with their mechanical behavior and energy absorption characteristics rigorously analyzed and validated through finite element simulations. Results indicated that the angle of the auxetic double arrowhead unit cell is the crucial geometric parameter affecting mechanical behavior and dominant failure modes. The volumetric energy absorption and specific volumetric energy absorption of the auxetic double arrowhead lattice structure with geometric functionally graded with α = 14° to 20° are 81% and 173% higher, respectively, compared to the uniform auxetic double arrowhead lattice structure with α = 10°. In light of these findings, geometric functionally graded designs offer superior energy absorption performance for auxetic double arrowhead lattice structures with negative Poisson's ratio compared to conventional uniform arrangements.