L. Meza; N. Anandan; C. Wilson
SSRN 5009936
Ceramics are broadly used in applications from medical implants to next-generation turbine blades, but they are plagued by their tendency for brittle failure. Recent studies have demonstrated that ceramic metamaterials can recover from large strains if their deformation is dominated by shell buckling, but this requires them to be ultralight, limiting their utility. This work explores how gradient architecture can hinder crack propagation in higher-density nanostructured ceramic metamaterials, permitting recovery while accommodating local fractures. We experimentally and numerically investigated five shell-based spinodal ceramic nanoarchitectures with varying anisotropy and structural gradients and wall thicknesses from 10-80 nm. Architectures with thin walls < 40 nm were governed by shell buckling and showed nearly full recovery after compression to ~45\% strain. Both isotropic and anisotropic architectures with walls > 40 nm thick tended to show permanent failure even at low strains. Unexpectedly, architectures with pronounced structural gradients showed localized cracking but managed full recovery after large compression. This result stems from structural heterogeneity within the fracture process zone-gradient interfaces distribute stress to stop cracks from fully developing, thereby preventing catastrophic failure. Our findings have significant implications for how to use length scale and heterogeneity to design failure-resistant materials from brittle constituents.