  We investigate fracture toughness of architected interfaces and their ability
to maintain structural integrity and provide stable damage propagation
conditions beyond the failure load. We propose theoretical and numerical
frameworks to evaluate the fracture properties of architected interfaces
sandwiched between two (face) materials. The microscopic geometries of these
interfaces are chosen as 2D cells--pillar, tetrahedron, and hexagon--as well as
their 3D counterparts--namely, pillar array, octet truss, and Kelvin cell. Our
model, both numerical and analytical, exhibits a high level of accuracy in
predicting the compliance before failure and failure loads. Novel results are
obtained during the damage propagation regime, indicating fulfilment of the
so-called fail-safe design. Some of the cell geometries unfold during fracture,
thus increasing the failure load and ensuring stable and controlled damage
propagation conditions.
