Additively Manufactured Functionally Graded Lattices: Design, Mechanical Response, Deformation Behavior, Applications, and Insights

Flora and fauna have evolved to distribute their structural mass efficiently in response to their environment. Inspired by this structural efficiency, functionally graded lattices (FGL) are an emerging subset of non-uniform lattices that employ density gradients for a function-driven mechanical response. These gradients are controlled by stepwise or continuous changes in the geometry or topology of the lattice unit cells. FGLs have the capacity for multifunctionality, facilitating high compliance and energy absorption, or moderate strength and stiffness depending upon the specific gradient. These novel lattice structures have been utilized for a range of applications, including biomimetic implants, heat dissipation, and impact absorption. The fabrication of FGLs with complex internal topologies is facilitated through additive manufacturing (AM) using materials such as metals, polymers, and composites. The mechanical properties of these lattices have been examined through compressive testing. The elastic modulus and the yield stress are reported to range from 0.009 GPa to 6.0 GPa, and from 0.38 MPa to 424 MPa for relative densities between 10% and 80%, respectively. Energy absorption is reported to supersede conventional uniform lattices by up to 30%. By accumulating and assessing the mechanical, geometric, and topological data from the FGL literature, this review will systematically classify and explore the viability of these novel structures for real-world applications.

Automated summary

Inspired by the efficiency of plants and animals, functionally graded lattices (FGL) utilize density gradients for diverse mechanical responses and have a wide range of applications. Additive manufacturing (AM) enables the fabrication of FGL structures with complex internal topologies.