Superior strength and energy absorption capability of LPBF metallic functionally graded lattice structures

Lightweight structures exhibiting superior mechanical response are highly desirable and find widespread applications in aerospace, biomedical, and automotive industries. Lattice structures are among the promising lightweight mechanical metamaterials with excellent specific strength and energy absorption capabilities. To further enhance the behavior of stretching dominant lattice structures for high-strength applications without compromising their lightweight nature, volume fraction-based functional gradience has been proposed and evaluated in detail in this study. Laser powder bed fusion fabricated Ti6Al4V octet lattice structures with uniform volume fractions and functionally graded lattice structures were fabricated and investigated. Experimental and numerical investigations focused on various functional gradient lattice structures, including Uni-Graded, Bi-Graded Horizontal, and Bi-Graded Vertical, encompassing a wide range of volume fraction variations. The incorporation of functional gradience resulted in a substantial enhancement in both strength and energy absorption capabilities. Uni-Graded and Bi-Graded Vertical functionally graded lattice structures with significant volume fraction variations (referred to as UG3 & BGV3) exhibited an approximate 25 % enhancement in compressive strength, rising from 160 MPa for uniform lattice structure to 200 MPa. Furthermore, these functionally graded lattice structures also demonstrated a remarkable enhancement in energy absorption capacity per unit volume (91 % for UG3 and 101 % for BGV3), underscoring the significant role of functional grading patterns and volume fraction variations in shaping the behavior of lattice structures.