Engineering crack tortuosity in polymer-polymer composites through ordered pores

Multimaterial additive manufacturing (or 3D printing) is an enabling tool for exploring structure-property relationships. In this work, a recently developed multimaterial printing approach, solution mask liquid lithography (SMaLL), is used to produce polymer-polymer composites inspired by tough, hierarchical structures found in nature. Triphasic composites comprised of a hard exterior “cuticle”, a soft interior “core,” and controlled pore size/structure are printed in a single step and their mechanical properties evaluated. The results of these tests demonstrate that varying the size and packing of pores in the core structure leads to significant enhancement in crack deflection. Finite element analysis reveals that this enhancement is linked to geometry-dependent stress distribution in each material. These results provide design cues for increasing resilience in multimaterial polymer-polymer composites.