Optimized design of interlocking metasurfaces

Interlocking metasurfaces (ILMs) are a new class of mechanical metasurfaces built from architected arrays of interlocking features that can serve as a nonpermanent, robust joining technology. An ILM's strength is governed by the structural material, orientation, and topology of its latching unit cells. The presented work optimized the topologies of ILM unit cells to maximize strength in tensile and shear loading using gradient-based parametric optimization and genetic algorithms. Experimental validation confirmed that the optimized designs achieved considerable strength increases compared to a human intuitive design. In several cases, the optimized designs were approximately double the effective interfacial strength compared to that achieved via expert intuition alone. The strength improvement was seen for isolated unit cells and arrays of interacting unit cells (metasurfaces). An analysis of the topologies of the optimized designs showed that tall dendritic geometric features with large contact surfaces yield robust solutions in tension, while short and broad geometric features with large contact surfaces yield better results in shear loading. This study revealed the importance of shape optimization to maximize ILM effectiveness under single- and multi-objective scenarios.