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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.
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Room temperature crack-healing in an atomically layered ternary carbide
Ceramic materials provide outstanding chemical and structural stability at high temperatures and in hostile environments but are susceptible to catastrophic fracture that severely limits their applicability. Traditional approaches to partially overcome this limitation rely on activating toughening mechanisms during crack growth to postpone fracture. Here, we demonstrate a more potent toughening mechanism that involves an intriguing possibility of healing the cracks as they form, even at room temperature, in an atomically layered ternary carbide. Crystals of this class of ceramic materials readily fracture along weakly bonded crystallographic planes. However, the onset of an abstruse mode of deformation, referred to as kinking in these materials, induces large crystallographic rotations and plastic deformation that physically heal the cracks. This implies that the toughness of numerous other layered ceramic materials, whose broader applications have been limited by their susceptibility to catastrophic fracture, can also be enhanced by microstructural engineering to promote kinking and crack-healing.
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- Award ID(s):
- 1944496
- PAR ID:
- 10330631
- Date Published:
- Journal Name:
- Science Advances
- Volume:
- 7
- Issue:
- 33
- ISSN:
- 2375-2548
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1126/sciadv.abg2549
