Experimental analysis of rate-dependent toughness of 3D-printed soft interface composites

The hierarchical structure of biological nacre has long inspired the design of tough, damage-tolerant synthetic composites for advanced engineering applications. In this study, nacre-inspired composites were fabricated via additive manufacturing, embedding rigid inclusions within a soft polymer matrix, and systematically tested to complete fracture. We proposed innovative geometric designs and benchmarked them against the nacre-like architecture, validating experimental outcomes using the material-sink (MS) fracture modeling framework. This work is the first to reveal the rate-dependent fracture pathways in nacre-like composites across a wide spectrum of loading rates – from quasi-static to dynamic – and to document the novel emergence of inclusion fracture as a dominant failure mode at high strain rates. Moreover, the nacre-like design demonstrated exceptional mechanical performance – outperforming alternative architectures by nearly an order of magnitude in work of fracture – due to its unique, multi-stage fracture mechanism that delays and distributes damage progressively. These findings offer critical new insights into the interplay between architectural design and strain-rate effects, providing unprecedented guidance for optimizing nacre-inspired composites for dynamic, load-bearing applications.