A. Alrashed; Z. Patel; K. Dwiwedi; B. White; B. Kaehr; B.L. Boyce; L. Meza
SSRN (2025) 5737745
Architecture has long been used as a tool to enhance material toughness, but despite the extensive
investigations into toughening mechanisms, the role of feature size remains poorly understood.
In this work, we demonstrate the powerful connection between size and toughness by combining
fracture experiments on macro- and nanolattices with an analytical framework that integrates
fracture size-effects. We fabricate rhombic dodecahedron, octet-truss, and interpenetrating macro-
lattices from brittle (Vero) and less-brittle (Avero) polymer, along with nanolattices made using
a single polymer (IP-Dip) processed to be brittle or ductile. Nearly all lattices failed in a ductile
manner, even when made from nominally ‘brittle’ constituents. Notably, lattices undergoing
this brittle-to-ductile transition achieved a substantial 3–6× higher work of fracture than their base
materials despite having only 25% relative density. Our analytic framework reveals two key
mechanisms for this enhancement: (1) size-affected brittle-to-ductile transitions at the material scale
amplify lattice plastic energy dissipation, and (2) interpenetrating architectures enhance the size
and thereby energy dissipation of the damage zone in brittle-strut lattices. This framework establishes
a generalized method to design resilient metamaterials from virtually any brittle or ductile
constituent.