Abstract

Rapid progress in additive manufacturing methods has led to the creation of a new class of architected metamaterials that comprise of a network of struts resembling a periodic truss structure. The mechanical performance these materials is ultimately limited by their tolerance to damage and defects. Yet, manufacturing limitations has meant that experimental investigations of the toughness of these materials have remained elusive. Using architected material specimens comprising 10s of millions of unit-cells we show that not only is stress intensity factor, as used in conventional elastic fracture mechanics, insufficient to characterise fracture in these architected materials but also that conventional fracture testing protocols are inadequate. Via a combination of numerical calculations and asymptotic analyses we extend the ideas of fracture mechanics to architected materials and thereby develop a design and test protocol for their structural failure.