De-localizing brittle fracture

TL;DR

This paper introduces engineered metamaterials that prevent damage localization by promoting independent failure of sub-elements, leveraging nonlocal stress redistribution through high contrast composite structures to transition from brittle to ductile behavior.

Contribution

It presents a novel design of metamaterials with zero-stiffness sub-structures that de-localize cracking, enabling control over brittle fracture behavior.

Findings

De-localization of cracks in engineered metamaterials.

Transition from brittle to ductile behavior demonstrated.

Continuum description dominated by gradient elasticity.

Abstract

Extreme localization of damage in conventional brittle materials is the source of a host of undesirable effects. We show how artificially engineered metamaterials with all brittle constituents can be designed to ensure that every breakable sub-element fails independently. The main role in the proposed design is played by high contrast composite sub-structure with zero-stiffness, furnishing nonlocal stress redistribution. The ability to de-localize cracking in such nominally brittle systems is revealed by the fact that their continuum description is dominated by the gradient (bending) rather than classical (stretching) elasticity. By engineering a crossover from brittle to effectively ductile (quasi-brittle) behavior in prototypical systems of this type, we reveal the structural underpinning behind the difference between fracture and damage.