Shape morphing of additively manufactured metallic kinematic structures to trace single- and doubly-curved surfaces

Abstract

Biocompatible and shape-morphing metallic structures have been proposed for musculoskeletal applications to provide structural support to bony tissues. However, fabricating these structures to conform to a wide range of curvatures, including both single and double curvatures, remains a significant challenge. In this study, we present and analyze structures featuring a regular tiling network connected by spherical joints, forming a chain mail-like mechanism capable of adapting to complex geometries with clay-like flexibility. Simulations using a multibody kinematics model show that parameters such as unit cell shape, dimension ratios, and substrate curvature affect the shape-matching abilities of the structure. Experimental validation using specimens additively manufactured through laser-based powder bed fusion (from Ti6Al4V) and full-field strain measurements performed through digital image correlation confirms the simulation results, demonstrating that reducing structural density (i.e., fewer bodies, struts, and joints per unit area) improves shape adaptability. However, the improved shape morphing capability often comes at the expense of mechanical strength under uni-axial tensile loads. These findings provide a framework for optimizing structures designed to achieve efficient surface conformance and adaptability in load-bearing applications.