N. Anandan; C.G. Wilson; L.R. Meza
International Journal of Mechanical Sciences 301 (2025) 110453
A fundamental challenge for lightweight architected materials is their propensity for localized failure due to layered buckling, plastic shear-banding or fracture. Recent research efforts have used disorder to interrupt localization and enhance deformation, but most design strategies simply distribute the accumulation of damage, they do not prevent it from developing and propagating. This work explores how gradient architecture can be designed to hinder crack propagation and promote recoverability in nanostructured ceramic metamaterials. We experimentally and numerically investigated five different shell-based spinodal ceramic nanoarchitectures with 10-80 nm thick alumina films. These were fabricated using atomic layer deposition on sacrificial polymeric scaffolds written using two-photon lithography. All thin-walled (< 40 nm) architectures underwent shell buckling-dominated deformation and showed nearly full recovery after compression to∼ 45% strain, an expected result for this class of nanoarchitected materials. Thick-walled (> 40 nm) isotropic and anisotropic architectures experienced considerable local damage during compression and predictably showed permanent failure even at low strains. Unexpectedly, thick-walled conch-shell inspired gradient architectures showed localized damage but experienced a full recovery after compression to∼ 45% strain. This degree of recoverability has never been observed in this high density of a nanostructured ceramic, particularly one with visible local cracking during compression. This result stems from the length scale of the structural heterogeneity—the gradient layers were sufficiently small so as to inhibit the local damage development needed for crack propagation, thereby preventing catastrophic failure. Our findings have significant implications for how length scales and heterogeneity can be used to design failure-resistant materials from brittle constituents.